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# Optical Perspectives Group

Alignment tools for optimizing opto-mechanical system performance

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## Posts

- [Blog](https://www.opticalperspectives.com/blog/)
- [Choosing Between Portable and Lab-Based Optical Metrology Systems](https://www.opticalperspectives.com/portable-optical-metrology-field-lab/) - Compare portable optical metrology systems with lab-based interferometry for field alignment in aerospace, manufacturing, and telescope installation applications.
- [Choosing Between Interferometers and PSMs for Your Optical Lab](https://www.opticalperspectives.com/interferometer-psm-optical-alignment-comparison/) - Compare interferometers and Point Source Microscopes for optical alignment. Learn accuracy specs, costs, portability trade-offs, and which tool fits specific lab applications best.
- [The Point Source Microscope, a unique autocollimator](https://www.opticalperspectives.com/the-point-source-microscope-a-unique-autocollimator/) - ABSTRACT The Point Source Microscope (PSM) utilizes infinite conjugate optics internally. When the microscope objective is removed, the PSM is an autocollimator. Unlike conventional autocollimators, which use a reticle pattern for illumination, the PSM employs a single-mode fiber. The PSM camera captures a well-focused, circular return reflection when a perfect plane mirror is aligned perpendicular
- [Understanding Point Source Microscopes: Complete Technical Guide for Engineers](https://www.opticalperspectives.com/point-source-microscope-guide/) - Learn what a point source microscope is, how it differs from interferometers, and when to use this precision optical alignment tool in engineering applications.
- [Chapter 2 Radius measurement – the original use of an autostigmatic microscope](https://www.opticalperspectives.com/chapter-2-radius-measurement-the-original-use-of-an-autostigmatic-microscope/) - After finishing Chapter 1, I was going to jump right into discussing using the PSM for opticalalignment. As I started an outline for this Chapter, one of the entries was locating the center ofcurvature, and this led to radius of curvature which made me think that it would be best toexplain the origin of the
- [Chapter 1 The Optics of the Point Source Microscope (PSM)](https://www.opticalperspectives.com/chapter-1-the-optics-of-the-point-source-microscope-psm/) - This chapter introduces the Point Source Microscope (PSM) as a multipurpose optical metrologyinstrument. For those already familiar with the PSM, many of the following concepts may seemstraightforward. However, for new users—or those with limited background in optics—theoperation and capabilities of the instrument are not immediately obvious. Even experienced usersmay not fully appreciate certain aspects of
- [Centering with the PSM](https://www.opticalperspectives.com/centering-with-the-psm/) - Centering with the Point Source Microscope (PSM) is a perfect application. Centering with the Point Source Microscope (PSM) is a perfect application. When a spot of light from the objective focus is reflected back from a concave surface sitting on a rotary table, it will sweep out a circle on the video screen as the
- [Conjugate Selection For Precision Lens Centering](https://www.opticalperspectives.com/conjugate-selection-for-precision-lens-centering/) - ABSTRACT The concept of centering a precision, symmetric lens system using a high-quality rotary table and an auto-focusing test instrument are well known. Less well known are methods of finding convenient, or easily accessible, lens conjugates on which to focus while performing the centering operation. We introduce methods of finding suitable conjugates and centering configurations
- [Lens Centering Using The Point Source Microscope](https://www.opticalperspectives.com/lens-centering-using-the-point-source-microscope/) - ABSTRACT Precision lens centering is necessary to obtain the maximum performance from a centered lens system. A technique to achieve precision centering is presented that incorporates the simultaneous viewing through the upper lens surface of the centers of curvature of each element as it is assembled in a lens barrel. This permits the alignment of
- [Practical Alignment Using An Autostigmatic Microscope](https://www.opticalperspectives.com/practical-alignment-using-an-autostigmatic-microscope/) - ABSTRACT Auto-stigmatic microscopes (ASM) are useful for bringing centers of curvatures of lenses and mirrors to the centers of balls used as part of an alignment fixture. However, setting up the fixture to get the balls used for alignment in a straight line to represent the optical axis generally requires another piece of equipment. We
- [Calculation Of The Vertex Radius Of An Off Axis Parabolic Surface Using The Sag Measured With A Three Ball Spherometer](https://www.opticalperspectives.com/calculation-of-the-vertex-radius-of-an-off-axis-parabolic-surface-using-the-sag-measured-with-a-three-ball-spherometer/) - Abstract We describe a method of calculating the vertex radius of an off-axis parabolic segment using a three ball spherometer to measure the sag. The vertex radius is found by solving a set of six simultaneous, non-linear equations for the three coordinates of one of the ball centers and the corresponding three coordinates of the
- [Swing Arm Optical Coordinate-Measuring Machine: High Precision Ground Aspheric Surfaces Using A Laser Triangulation Probe](https://www.opticalperspectives.com/swing-arm-optical-coordinate-measuring-machine-high-precision-ground-aspheric-surfaces-using-a-laser-triangulation-probe/) - ABSTRACT The swing arm optical coordinate-measuring machine (SOC), a profilometer with a distance measuring interferometric sensor for in situ measurement of the topography of aspheric surfaces, has shown a precision rivaling the full aperture interferometric test. To further increase optical manufacturing efficiency, we enhance the SOC with an optical laser triangulation sensor for measuring test
- [Method Of Alignment Using A Laser Tracker System](https://www.opticalperspectives.com/method-of-alignment-using-a-laser-tracker-system/) - 1. Introduction: Laser trackers are an accurate and efficient tool for finding the locations of features in a threedimensional space but they rely on Spherically Mounted Retroreflectors (SMR) to return the laser beam to the tracker. If the feature cannot be contacted or it is not convenient to use an SMR another method must be
- [Using The Point Source Microscope (PSM) To Find Conjugates Of Parabolic And Elliptical Off-axis Mirrors](https://www.opticalperspectives.com/using-the-point-source-microscope-psm-to-find-conjugates-of-parabolic-and-elliptical-off-axis-mirrors/) - ABSTRACT Although the PSM is primarily an alignment instrument, it can also be used to determine the conjugates of parabolic and elliptical off-axis mirrors. By positioning the PSM at the sagittal and tangential foci of the mirrors, the conjugate distances of the mirror can be found using a laser range finder, for example. Knowing the
- [Alignment Of Optical Systems](https://www.opticalperspectives.com/alignment-of-optical-systems/) - 1. Introduction As optical systems become more complex and packaging requirements more severe and multi-dimensional, proper alignment becomes more challenging. Yet with current improvements in the manufacture and measurement of optical surfaces to nm levels, alignment is one of the few remaining opto-mechanical aspects of optical system manufacture and assembly where improvement in optical performance
- [Optical Alignment Using The Point Source Microscope](https://www.opticalperspectives.com/optical-alignment-using-the-point-source-microscope/) - ABSTRACT We give an example of a Point Source Microscope (PSM) and describe its uses as an aid in the alignment of optical systems including the referencing of optical to mechanical datums. The PSM is a small package (about 100x150x30 mm), including a point source of light, beam splitter, microscope objective and digital CCD camera
- [Versatile Autostigmatic Microscope](https://www.opticalperspectives.com/versatile-autostigmatic-microscope/) - ABSTRACT An autostigmatic microscope is described and its uses explained. Then an adaptation of the original instrument is described that uses current technological advances in laser diodes and video displays to turn an old workhorse into a versatile optical test and alignment device. This paper illustrates applications that make use of the capabilities of the
- [Non-Contact Probe For On-Machine Metrology](https://www.opticalperspectives.com/non-contact-probe-for-on-machine-metrology/) - INTRODUCTION On-machine metrology is particularly important for diamond turning and grinding as it is difficult to remount and align a part if it does not meet off-line inspection criteria. There is also the issue of tool wear; a process that started well may fail part way through the cut, and if tool replacement is needed,
- [Reverse Engineering Lens Elements](https://www.opticalperspectives.com/reverse-engineering-lens-elements/) - Introduction Need for reverse engineering Properties necessary for reverse engineering How to make necessary measurements How to calculate the paraxial properties Use of a spreadsheet for the solution Use of a lens design program to find a solution Need for reverse engineering Actually want to copy someone’s design Concern that lens may be wrong glass
- [A Contemporary Version of the Autostigmatic Microscope and Its Uses](https://www.opticalperspectives.com/a-contemporary-version-of-the-autostigmatic-microscope-and-its-uses/) - OUTLINE What is an autostigmatic microscope (ASM) Measuring the radius of curvature of a concave surface– Main historical use Modern version of an ASM uses internal infinite conjugate optics Use of an ASM for alignment of optical systems Other uses of an ASM Conclusions DESCRIPTION OF AN ASM First description in English literature is Drysdale,
- [Webinar: The Autostigmatic Microscope and Its Uses](https://www.opticalperspectives.com/webinar-the-autostigmatic-microscope-and-its-uses/) - This webinar with Robert Parks is presented by the OSA Systems and Instrumentation Technical Group. Topics discussed include the evolution of the classical autostigmatic microscope (ASM) into an all-purpose optical alignment tool whose use has been described in over 60 optical engineering papers that illustrate real-world systems applications. The evolution that led to the current
- [Computer Generated Holograms As Fixtures For Testing Optical Elements](https://www.opticalperspectives.com/computer-generated-holograms-as-fixtures-for-testing-optical-elements/) - 1. INTRODUCTION It is common to think of computer generated holograms (CGH) as artifacts for testing aspheres but they can also be used as general calibration artifacts and fixtures for the alignment and test other more conventional optics. We show how simple Fresnel zone patterns can be created to simulate centers of curvature or axes
- [Centering Steep Aspheric Surfaces](https://www.opticalperspectives.com/centering-steep-aspheric-surfaces/) - 1. INTRODUCTION Finding the optical axis of an aspheric surface is an essential part of making an aspheric lens because the center of curvature, or optical axis, of the second side must lie on, or be coincident with, respectively, the optical axis of the first side for maximum optical performance. Looking at the center of
- [Videos From the Optical Society](https://www.opticalperspectives.com/videos-from-the-optical-society/) - OSA Stories The Optical Society offered Robert (Bob) Parks an opportunity to share his stories of excitement and inspiration in a couple of short videos. (ANNOUNCEMENT FROM THE OPTICAL SOCIETY) OSA CAM VIDEOS We're Celebrating All Members (CAM) by inviting members attending many OSA meetings and congresses with an opportunity to share their stories. View OSA
- [Design For Alignment](https://www.opticalperspectives.com/design-for-alignment/) - 1. INTRODUCTION The premise of this paper is that the only remaining way to improve optical system performance is with better alignment techniques. We feel optical design is a mature field and that little can be done to improve the design of optical systems by improvements to lens design software. The software may become easier
- [Prism Alignment Using A Point Source Microscope](https://www.opticalperspectives.com/prism-alignment-using-a-point-source-microscope/) - The Point Source Microscope (PSM) is used to locate the apex of retroreflecting prisms in 3 degrees of translational freedom with a precision of less than 1 micron. The process is easily explained for right angle prisms, as will be done in this paper, but the explanation is valid for cube corner retroreflectors such as those mounted in spherical balls, spherically mounted retroreflectors, or SMRs, for use with laser trackers. With suitable, simple fixtures, the measurements for all 3 directions are made to a precision of < 1 μm in less than 1 minute.
- [Report on Finding Best Focus of Slow Systems](https://www.opticalperspectives.com/report-on-finding-best-focus-of-slow-systems/) - EXPERIMENTAL SETUP: A Point Source Microscope (PSM) was mounted on a motorized vertical stage above a 25 mm diameter, 200 mm efl lens sitting above a plane mirror. A square black paper mask with an 8 mm diameter hole was placed over the lens as shown in the figure below to give an f/25 aperture.
- [Aligning Reflecting Optics With Bessel Beams](https://www.opticalperspectives.com/aligning-reflecting-optics-with-bessel-beams/) - ABSTRACT Bessel beams have found use in the alignment of transmissive optics for some time. They are also used for the alignment of reflecting optics when used in the imaging mode, that is, when the wavefront is near spherical. However, there are cases where it would be useful to use the Bessel beam for alignment
- [Precision Cementing Of Doublets Without Using A Rotary Table](https://www.opticalperspectives.com/precision-cementing-of-doublets-without-using-a-rotary-table/) - Methods of centering without using a precision rotary table to establish a reference axis in space are several times faster than with a rotary table. However, finding an optimum method of establishing an alternative reference axis is challenging. We look at the small class of centering situations involving the precision cementing of doublets to illustrate the advantages of using a Bessel beam as the reference axis. Two approaches to centering illustrate the method: one involving first aligning the meniscus element and then adding the positive element, and the other, cementing the two elements and aligning the pair.
- [News & Announcements for January 2021](https://www.opticalperspectives.com/news-announcements-for-january-2021/) - GOOD NEWS FOR THE NEW YEAR, THE STANDARD PSM WORKS IN THE NEAR IR Many times potential customers have asked “How far does the PSM work into the infrared?” I told them the standard PSM works as far out as 1050 nm with the CMOS camera that comes with every new PSM because I have
- [How Well Can the Point Source Microscope (PSM) Locate the Source of a Single Mode Fiber?](https://www.opticalperspectives.com/__trashed-3/) - I needed to measure the height of a free space fiber termination above an optical bench the other day and in the process remembered a question I had been asked in passing. Since I had the pieces of such an experiment in front of me, all I had to do was save a couple of
- [How Repeatably Can the Point Source Microscope Find Best Focus at a Center of Curvature?](https://www.opticalperspectives.com/how-repeatably-can-the-point-source-microscope-find-best-focus-at-a-center-of-curvature/) - Recently, a client asked how well can you focus if you really had to do better? I did not know but it was easy to do an experiment with our centering station that has a motorized stage and the ability to log data as the stage moves. It is easily demonstrated that the PSM lateral
- [Need Custom Optical Test Equipment?](https://www.opticalperspectives.com/need-custom-optical-test-equipment/) - WHY START FROM SCRATCH WHEN YOU CAN ORDER A PSM FROM OUR WEBSITE? It may surprise you but about 15% of Point Source Microscopes (PSMs) purchased are built into custom optical test hardware. Optical Perspectives supplies a CAD model of the PSM to help the customer integrate the PSM into their test hardware design. When
- [Practical Considerations For Using Grating Produced Bessel Beams For Alignment Purposes](https://www.opticalperspectives.com/practical-considerations-for-using-grating-produced-bessel-beams-for-alignment-purposes/) - Bessel beams are useful for alignment because they create a small diameter, bright, straight line image in space perpendicular to the Axicon, or Axicon grating, producing the beam that is an exact analog of a single ray in a ray tracing program. Here we limit our discussion to Bessel beams produced by plane gratings whose pattern is evenly spaced concentric circles that are illuminated by a point source of light on the grating axis. The gratings produce a more nearly ideal Bessel beam than a lens type Axicon, and the plane grating serves as a plane mirror as well in an alignment setup, so the combination defines four degrees of freedom in space rather than the usual two.
- [Rapid Centering Of Optics](https://www.opticalperspectives.com/rapid-centering-of-optics/) - Traditionally a rotary table is used for optical centering because the table creates an axis as a reference. Previously, we showed that a Bessel beam also creates an axis useful for centering. The Bessel beam axis and the center of curvature of the surface makes it possible to center an optic simultaneously in tilt and decenter. We also showed that simultaneously sampling two arbitrary points along the Bessel beam also permits full adjustment of tilt and decenter of a powered optic. This makes centering possible without either a rotary table or a precision linear stage. In most common instances, however, sampling the beam at two points is unnecessary because of the inability to correct for both tilt and decenter. We discuss an alternative, simpler method using a Bessel beam.
- [Chapter 4: Autostigmatic Microscope](https://www.opticalperspectives.com/chapter-4-autostigmatic-microscope/) - There is no better way to describe an autostigmatic microscope (ASM) than to call it an autocollimator (AC) with a microscope objective attached to the front. This converts the AC from an instrument that measures 2 angular degrees of freedom (DOF) into an instrument that measures the location of the center of curvature of a
- [Chapter 6: Centering on a Single Center of Curvature](https://www.opticalperspectives.com/chapter-6-centering-on-a-single-center-of-curvature/) - In this Chapter we will discuss the centering of a single center of curvature of a lens in a cell sitting on a rotary table that creates a reference axis. This discussion describes the traditional method of centering a lens in a cell. While this does not sound like an ambitious goal, the ideas presented
- [Chapter 8: Alignment of 3 Centers of Curvature](https://www.opticalperspectives.com/chapter-8-alignment-of-3-centers-of-curvature/) - A convenient and concrete example of aligning three centers of curvature is the cementing of the doublet we used in the optical axis example in Chapter 5, the details of which are reproduced below. Fig. 1 Doublet used as an example of aligning three centers of curvature The goal is to get all three centers
- [Chapter 9: Creating and Viewing Single Paraxial Ray](https://www.opticalperspectives.com/chapter-9-creating-and-viewing-single-paraxial-ray/) - From the beginning we have said that centering a lens meant aligning the optical axis of the lens to a reference axis. Up to this point we have assumed the axis was the mechanical axis of a rotary table. Because there are disadvantages to using a rotary table, I was curious to see if there
- [Chapter 10: Index of Refraction and Lens Conjugates        ](https://www.opticalperspectives.com/chapter-10-index-of-refraction-and-lens-conjugates/) - This Chapter is a little out of order but illuminates a topic we have hinted at in previous Chapters, how does the index of refraction affect the lens conjugates we see when doing centration? The immediate interest came from a call I got because some glass apparently got mixed up in a batch of identical
- [Chapter 11: Alignment and Precision Engineering](https://www.opticalperspectives.com/chapter-11-alignment-and-precision-engineering/) - As I said in the first chapter, I hope to make these articles into a book on alignment after significant editing to organize the material coherently. In that spirit, and before I forget, let me discuss some aspects of alignment and precision engineering that belong in a Preface or Introduction to the book rather than
- [Chapter 12: Further Comments on Classical Optical Instruments](https://www.opticalperspectives.com/chapter-12-further-comments-on-classical-optical-instruments/) - There was more interest in Chapter 3 about the classical instruments used for optical alignment than any other chapter to date, and I didn’t have a chance to say all I wanted to, so I will continue the discussion in this Chapter to emphasize how changes in technology have changed the design of these instruments.
- [Chapter 14: Tabletop Alignment Part 1](https://www.opticalperspectives.com/chapter-14-tabletop-alignment-part-1/) - At last, I am back to writing more about optical alignment. The hiatus was due to my realization that most readers are not interested in assembling lenses in a tube. Rather, they want to align free-standing optics on tabletops or benches in labs researching topics like laser light interactions with matter, free-space communication, and quantum
- [Chapter 15: Tabletop Alignment Part 2](https://www.opticalperspectives.com/chapter-15-lens-alignment-to-a-reference-bessel-beam/) - In Chapter 14, we showed how to determine the axis of a laser beam to which we want to align optical elements and then how to align a Bessel beam to the laser beam axis. This Chapter shows the steps to align optical elements to the reference Bessel beam. With tabletop alignment, you have all
- [Chapter 16 - Footnote for Chapters 14 and 15](https://www.opticalperspectives.com/chapter-16-footnote-for-chapters-14-and-15/) - This brief chapter serves as a vital addendum to the last two chapters. While I’ve already described the alignment process, I realized I hadn’t emphasized how remarkably simple it is—and what makes it so effortless. Over the years, countless methods have been used to align optics successfully, long before Bessel beams entered the picture. What
- [Chapter 17 - Alignment of Symmetric Parabolas](https://www.opticalperspectives.com/chapter-17-alignment-of-symmetric-parabolas/) - I often receive requests for assistance with aligning parabolic mirrors, particularly off-axis ones. Interestingly, with the right tools, the actual alignment process is often quicker than mounting the optical alignment equipment. This observation led me to reflect on the tools themselves. Currently, no traditional method—whether using an autocollimator or an alignment telescope—provides an effective way
- [Chapter 18 - Alignment of Off-Axis Parabolas](https://www.opticalperspectives.com/chapter-18-alignment-of-off-axis-parabolas/) - Although this is a chapter on off-axis parabolas (OAPs), I want to start with one more way of testing symmetric parabolas because it illustrates a point about off-axis alignment. Assume we have a symmetric parabola with no central hole and we want to minimize the obstruction due to testing. If we set the parabola up
- [Chapter 19 - Microscope Objective to Tube Lens Alignment](https://www.opticalperspectives.com/chapter-19-microscope-objective-to-tube-lens-alignment/) - The subject of this Chapter is prompted by several questions over the last couple of months concerning the alignment of tube lenses to high power microscope objectives. In most microscopes these days the objectives are designed as finite to infinite conjugate optics so there is a need for a “tube” lens to focus the object
- [Optical Alignment for Quantum Computing: Why Precision Matters More Than You Think](https://www.opticalperspectives.com/optical-alignment-quantum-computing-precision/) - Quantum computing demands unprecedented optical alignment precision. Learn why sub-micron alignment matters for qubit fidelity and how to achieve it in tabletop systems.
- [Why is Tucson called Optics Valley?](https://www.opticalperspectives.com/why-is-tucson-called-optics-valley/) - Since it’s Women’s History month, a question from my lawyer (a woman) about why Tucson is called “Optics Valley” reminded me of two influential women who are largely responsible for that legacy. The first is Lavinia Steward of Oracle, Arizona, who made the largest private donation to the University of Arizona up to that time
- [Alignment Chapters Take 2](https://www.opticalperspectives.com/alignment-chapters-take-2/) - Practical Optical Alignment with the Point Source Microscope In optical design, the concept of an optical axis is basic, it exists naturally within the description of the system. In the laboratory, however, the optical axis does not exist until it is physically established through measurements and alignment. Optical components must be positioned and oriented relative
- [Chapter 27 Another use for the Bessel beam](https://www.opticalperspectives.com/chapter-27-another-use-for-the-bessel-beam/) - We recently began assembling a 10.6 µm interferometer using a CO₂ laser as the coherent light source. Because most CO₂ lasers are designed for materials processing, their output power is far greater than is practical—or safe—for interferometry. Even after inserting a wire-grid polarizer immediately after the laser, our initial alignment attempts resulted in a burned
- [Chapter 26 Single lens centering](https://www.opticalperspectives.com/chapter-26-single-lens-centering/) - I was never satisfied with my explanation of lens centering, so this Chapter is another try. Start with a diagram that is familiar to anyone who has some familiarity with optics, the diagram that explains first order image formation as in Fig. 1. Fig. 1 A generic optical system with the two rays that define
- [ROI Analysis: When to Invest in a Point Source Microscope for Your Lab](https://www.opticalperspectives.com/point-source-microscope-roi-analysis-investment/) - Complete ROI analysis for Point Source Microscope investment. Calculate time savings, reduced scrap, and payback period for your optical alignment projects.
- [Chapter 25 Single lens centering](https://www.opticalperspectives.com/chapter-25-single-lens-centering/) - I was never satisfied with my explanation of lens centering, so this Chapter is another try. Start with a diagram that is familiar to anyone who has some familiarity with optics, the diagram that explains first order image formation as in Fig. 1. Fig. 1 A generic optical system with the two rays that define
- [Chapter 24 Alignment of convex surfaces](https://www.opticalperspectives.com/chapter-24-alignment-of-convex-surfaces/) - This chapter may seem out of sequence, but it tackles a recurring challenge that arguably deserved attention in a previous chapter: aligning convex surfaces. These surfaces appear nearly as often as their easier-to-align concave counterparts, yet they’re frequently overlooked—perhaps because they’re more difficult to visualize and work with. But they do exist, and they can’t
- [PSM vs. Interferometer: When to Use Each Tool for Optical Alignment](https://www.opticalperspectives.com/psm-vs-interferometer-when-to-use-each-tool-for-optical-alignment/) - Choosing the right metrology tool for optical alignment can significantly impact your project's success, timeline, and budget. Two of the most powerful instruments available are interferometers and Point Source Microscopes (PSM). While both excel at precision measurement, they serve different purposes and offer distinct advantages. At Optical Perspectives Group, we help optical engineers select the
- [5 Costly Optical Alignment Mistakes That Derail Research Labs (And How to Avoid Them)](https://www.opticalperspectives.com/costly-optical-alignment-mistakes-avoid/) - Discover the most expensive optical alignment errors research labs make and learn proven solutions. From environmental control to measurement methodology, avoid costly mistakes now.
- [Chapter 1: Introduction](https://www.opticalperspectives.com/chapter-1-introduction/) - Introduction to a Series of Articles on Optical Alignment For some time, I have been encouraged to write a book about optical alignment. There have been several half-hearted attempts at beginning, but it never seemed there was enough to talk about and I kept finding new ideas about alignment. I didn’t want the book to
- [Chapter 2: Three Methods of Alignment](https://www.opticalperspectives.com/chapter-2-three-methods-of-alignment/) - In the Introduction to this series of articles on optical alignment, I said there were three basic methods of alignment. This article presents my thoughts on these methods. My approach may be a bit unconventional, but I hope this way of beginning makes the whole idea of alignment easier to understand. To illustrate the three
- [Chapter 3: Classical Optical Alignment Instruments](https://www.opticalperspectives.com/chapter-3-classical-optical-alignment-instruments/) - Fig. 1 A simple collimator with a point source of illumination. An illuminated target in the same plane could serve as the source. Collimators are used as a light source for testing camera lenses on a nodal slide optical bench. The collimator simulates a point source, or in astronomical terms, a star, at infinity. For lens
- [Chapter 5: Optical Axis Definition](https://www.opticalperspectives.com/chapter-5-optical-axis-definition/) - The purpose of optical alignment is making the optical axis of an optical element, or complete system, coaxial with some other axis that is defined by other optical or mechanical components. This means we must start the discussion of optical alignment by making sure we all mean the same thing when we say the optical
- [Chapter 7: Centering 2 Centers of Curvature](https://www.opticalperspectives.com/chapter-7-centering-2-centers-of-curvature/) - In the previous chapter we looked at finding a single center of curvature using any of several optical instruments. This locates a particular point in space but does not define an axis. For that, two centers of curvature separated by a finite axial distance must be located to define an axis, or line. This chapter
- [Chapter 13: New Optical Alignment Tools](https://www.opticalperspectives.com/chapter-13-new-optical-alignment-tools/) - In Chapter 12, I commented again on classical optical instruments since there was interest in an earlier discussion. This got me thinking about what had changed in optical technology since the period ending about 1950 when there was a rather canonical set of classical optical metrology tools. There has been a huge technological change since
- [Chapter 20: Aligning Off-Axis Parabolas with a Bessel Beam — It’s Much Easier](https://www.opticalperspectives.com/chapter-20-aligning-off-axis-parabolas-with-a-bessel-beam-its-much-easier/) - Introduction In Chapter 18, I described aligning off-axis parabolas (OAPs) by placing the focus of a test instrument at the OAP's focus and autoreflecting off a plane mirror. Although I suggested some tips to ease the process, the initial alignment—getting the reflected light back into the test device's objective—remains challenging. Because I've found that using
- [Chapter 21 - Bessel Beam Alignment of a Single Lense](https://www.opticalperspectives.com/chapter-21-bessel-beam-alignment-of-a-single-lense/) - Introduction: In Chapters 14 and 15 I explained how a Bessel beam is used to align optics when you have all the necessary degrees of freedom to fully align the optics in tilt, decenter and focus. Many times, you have physical constraints due to the hardware the optics are installed in, so you don’t have
- [Chapter 22 - Simulation of the alignment of a Cooke triplet using a Bessel beam reference](https://www.opticalperspectives.com/chapter-22-simulation-of-the-alignment-of-a-cooke-triplet-using-a-bessel-beam-reference/) - For some time, I wanted to simulate the assembly of a Cooke triplet using a Bessel beam as a reference,and assuming the hardware constrained the alignment of each element to either a tilt or decenter as isthe case for many precision lens assemblies. A new optical design software is now available that makesthis modelling relatively
- [Chapter 23 Alignment of Convex Surfaces](https://www.opticalperspectives.com/chapter-23-alignment-of-convex-surfaces/) - This chapter may seem out of sequence, but it tackles a recurring challenge that arguably deserved attention in a previous chapter: aligning convex surfaces. These surfaces appear nearly as often as their easier-to-align concave counterparts, yet they’re frequently overlooked—perhaps because they’re more difficult to visualize and work with. But they do exist, and they can’t
- [A Short History of the CaliBall™ and the Random Ball Test](https://www.opticalperspectives.com/a-short-history-of-the-caliball-and-the-random-ball-test/) - Back in the late 1990’s NIST had a number of firms that wanted to send their interferometer transmission spheres there for calibration but NIST was not in this sort of calibration business. While I was at NIST consulting for Chris Evans in the Precision Machining Facility we thought of the idea of a self-calibration test
- [Practical Optical Tabletop Alignment](https://www.opticalperspectives.com/practical-optical-tabletop-alignment/) - Many research projects begin as tabletop assemblies of optical components to move light from a source through an interaction zone to change the character of the light and on to a detector. The quality of the signal reaching the detector depends on the optical alignment of all the components between the source and detector. The
- [What is an Autostigmatic Microscope (ASM) and the Origin of the Point Source Microscope (PSM)](https://www.opticalperspectives.com/what-is-an-autostigmatic-microscope-asm-and-the-origin-of-the-point-source-microscope-psm/) - When most people think of a microscope it is one that works in transmission with the light source on one side of the sample and the microscope objective and eyepiece on the other. An autostigmatic microscope (ASM) works in reflection, just like an autocollimator, so the light source is in the microscope body, and is
- [Ritchey-Common Test & Similar Methods Using AI Image Space Phase Retrieval](https://www.opticalperspectives.com/ritchey-common-test-similar-methods-using-ai-image-space-phase-retrieval/) - In this document, we will describe a general approach/method to measure optical surfaces in reflection and/or transmission when the incoming beam is not a simple plane wave. Among such tests are the Hindle test for measuring convex surfaces and the Ritchey-Common (RC) test for flat, concave, or convex surfaces. We will explain the concept using
- [Simulation for Design For Manufacture (DFM) and tolerancing of realistic optical surface scatter for Mid-spatial Frequencies (MSF) and beyond](https://www.opticalperspectives.com/simulation-for-design-for-manufacture-dfm-and-tolerancing-of-realistic-optical-surface-scatter-for-mid-spatial-frequencies-msf-and-beyond/) - Simon P. Tsaoussisa, W. Andrew Chenga, Ronnie Appelsb, and Robert E. Parksc aKostaCLOUD Inc., 5795 Commerce Lane, South Miami, FL 33143, USA bTucson Optical Research Corp., 210 S Plumer Ave, Tucson, AZ 85719, USA cOptical Perspectives Group LLC, 7011 E Calle Tolosa, Tucson, AZ 85750, USA ABSTRACT We propose a realistic model for tolerancing ofscattered surface
- [Quasi-Ray Tracing Realization Using a Bessel Beam for Optical Alignment](https://www.opticalperspectives.com/quasi-ray-tracing-realization-using-a-bessel-beam-for-optical-alignment/) - In this study, we explore the behavior of Bessel beams as they propagate through a misaligned apertured optical system in practice. Based on experimental observations, we propose what we believe to be a novel hypothesis that a Bessel beam propagating through an optical system behaves identically to a paraxial ray under certain conditions. We then derive analytical formulas for the propagation of Bessel beams in Cartesian coordinates and the Huygens-Fresnel principle. Additionally, another simulation employing Gaussian decomposition was conducted, and we compared both simulations with experimental results, demonstrating a high correlation. Our findings indicate that Bessel beams can be interpreted as meridional rays when passing through misaligned spherical surface systems, allowing us to achieve quasi-ray tracing in practice. We further discuss the significance of utilizing this property of Bessel beams for precise optical alignment, highlighting its potential to enhance the accuracy and efficiency of optical systems.
- [Optical alignment using the Point Source Microscope](https://www.opticalperspectives.com/optical-alignment-using-the-point-source-microscope-2/) - Robert E. Parks and William P. KuhnOptical Perspectives Group, LLC, 9181 E. Ocotillo Drive, Tucson, AZ 85749 ABSTRACT We give an example of a Point Source Microscope (PSM) and describe its uses as an aid in the alignment of optical systems including the referencing of optical to mechanical datums. The PSM is a small package
- [Physical Ray Tracing with Bessel Beams](https://www.opticalperspectives.com/physical-ray-tracing-with-bessel-beams-2/) - Robert E. ParksOptical Perspectives Group, LLC Tucson, AZ 85750 Daewook KimJ. C. Wyant College of Optical Sciences The University of Arizona Tucson, AZ 75721 INTRODUCTION Following the discovery of so called non- diffracting Bessel beams [1], they have been used for a number of exotic purposes such as trapping single atoms and aiding in the
- [Determination of the unique optical axis of assembled lens systems](https://www.opticalperspectives.com/determination-of-the-unique-optical-axis-of-assembled-lens-systems/) - Measuring the quality of alignment of an assembled compound lens is often necessary. This raises the question of what axis to use as a reference axis for this measurement. We suggest that the reference axis should be the optical axis of the assembled system and that this axis is unique for each assembly.
- [Computer Generated Holograms As 3-Dimensional Calibration Artifacts](https://www.opticalperspectives.com/computer-generated-holograms-as-3-dimensional-calibration-artifacts/) - The positioning accuracy of multi-axis machine tools and coordinate measuring machines are often checked using ball bars or ball plates where the spatial locations of the balls are externally calibrated to provide a traceable artifact [1,2]. In use, the individual ball surfaces are probed in at least 4 places with a tactile sensor and the points of contact fit to the equation of a sphere to determine the center of the ball. The method is tedious, indirect and semi-static. Furthermore, it is difficult or impossible to create artifacts that truly span the three-dimensional work volume of machines because some features become occluded by others and cannot be accessed.
- [Alignment Using Axicon Plane Gratings](https://www.opticalperspectives.com/alignment-using-axicon-plane-gratings/) - Axicon gratings are computer generated holograms of equally spaced concentric circles printed on a plane substrate. When illuminated by a point source of light they create axes in space defined by a line between the point source and the center of the grating pattern. The axis can be viewed in either transmission or reflection with an autostigmatic microscope. The axis created by the grating can be located to less than 1 um in translation and depending on distance from the grating to less than 1 microradian in angle. Several examples of such a use in alignment are explained.
- [Evaluating SMR Positioning with an Autostigmatic Microscope](https://www.opticalperspectives.com/evaluating-smr-positioning-with-an-autostigmatic-microscope/) - An optical method of determining the location of the apex of a corner reflector mounted in a steel ball, commonly referred to as a Spherically Mounted Retroreflector (SMR), relative to the center of the ball to the 1-2 μm level was previously described by us. The method used an autostigmatic microscope focused on the apex and viewed the reflected spot image as the SMR was rotated about a normal to its entrance aperture. This measurement determined the lateral offset of the apex and tipping the SMR while viewing the spot gave an indication of the axial displacement.
- [New Approach to Optical Assembly and Cementing](https://www.opticalperspectives.com/new-approach-to-optical-assembly-and-cementing/) - A novel method of projecting a reference axis in space for use in optical assembly of centered elements such as assembly in a barrel or in cementing multi-element lenses is presented. An axicon grating, a set of concentric, uniformly spaced circles, when illuminated with a point source of light creates a line of bright spots surrounded by concentric rings in both transmission through and reflection from the grating. This axis is easily interrogated with an autostigmatic microscope to gauge the distance a center of curvature, or other lens conjugate, lies from the axis created by the grating.
- [Optical Alignment Using a CGH and an Autostigmatic Microscope](https://www.opticalperspectives.com/optical-alignment-using-a-cgh-and-an-autostigmatic-microscope/) - We show how custom computer generated holograms (CGH) are used along with an autostigmatic microscope (ASM) to align both optical and mechanical components relative to the CGH. The patterns in the CGHs define points and lines in space when interrogated with the focus of the ASM. Once the ASM is aligned to the CGH, an optical or mechanical component such as a lens, a well-polished ball or a cylinder can be aligned to the ASM in 3 or 4 degrees of freedom and thus to the CGH. In this case we show how a CGH is used to make a fixture for cementing a doublet lens without the need for a rotary table or a precision vertical stage.
- [Optical Ball Center Finder for Use in the R-Test](https://www.opticalperspectives.com/optical-ball-center-finder-for-use-in-the-r-test/) - We present a description of an attachment for an autostigmatic microscope that uses two objectives set at right angles to unambiguously locate the center of a ball in all 3 translational degrees of freedom that can be used to perform the “R” test, or to scan a ball plate, to determine machine tool precision dynamically.
- [Using Image Symmetries to Uniquely Align Aspheric Mirrors to a Focus and Axis](https://www.opticalperspectives.com/using-image-symmetries-to-uniquely-align-aspheric-mirrors-to-a-focus-and-axis/) - The Point Source Microscope (PSM) is used to find five aberrations related to the symmetries of the autostigmatic image viewed when aligning aspheric mirrors to a point along an axis. These five aberrations exactly match in number the five degrees of mechanical freedom required to align the mirror to an axis and thus provide an exact solution to a unique focus and alignment to an axis. We show how the PSM is used to capture and analyze a set of images as the PSM is moved through focus using the symmetry properties of the image.
- [Systematic Method of Optical Alignment Using Aberrations](https://www.opticalperspectives.com/systematic-method-of-optical-alignment-using-aberrations/) - We use a known optic, a catalog off-axis parabola, as a reference to both model in Zemax and to align while tracking the position of the focus in 3 degrees of freedom (DOF) and the tilt of the auto-reflecting flat in 2 DOF to demonstrate a systematic approach to alignment. The aberrations present at each step of the experimental procedure are monitored using an autostigmatic microscope.
- [Physical Ray Tracing With Bessel Beams](https://www.opticalperspectives.com/physical-ray-tracing-with-bessel-beams-3/) - Following the discovery of so called non-diffracting Bessel beams [1], they have been used for a number of exotic purposes such as trapping single atoms and aiding in the discovery of exoplanets. We discuss more mundane but practical methods applicable to precision engineering, and the physical ray tracing of a ball lens in transmission to determine if it behaves as geometrical optics predicts.
- [Optical Alignment Using Bessel-Gauss Beams](https://www.opticalperspectives.com/optical-alignment-using-bessel-gauss-beams/) - The article demonstrates a new approach for achieving high-accuracy alignment with a Bessel-Gauss Beam by utilizing its property of propagating as a paraxial ray. © 2024 OSJ
- [Computer Generated Holograms as 3d Calibration Artifacts](https://www.opticalperspectives.com/computer-generated-holograms-as-3d-calibration-artifacts/) - In this paper we step back from complex CGH patterns used to test aspheric and freeform optics to ask what can be done with the simplest CGH patterns and the high precision of pattern location on a photomask substrate4. We first describe the use of patterns of equally spaced concentric circles to create an axis in space perpendicular to the CGH plane, and the Fresnel zone patterns that produce points in space when illuminated with a point source of light.
- [Complementary Aspects of Optical Alignment and Image Symmetry 4 Format](https://www.opticalperspectives.com/complementary-aspects-of-optical-alignment-and-image-symmetry-4-format/) - Optical aspherical surfaces have become more widely used as they offer advantages such as improved image quality, compact design, increased light gathering, and reduced distortion. However, measuring aspherical surfaces presents challenges due to their non-spherical shapes. The primary difficulties include the complexity of surface geometries and the need for specialized metrology equipment. These challenges require advanced measurement techniques to ensure accurate characterization and quality control of aspherical surfaces in various applications. This paper introduces an innovative, AI-driven solution for the measurement of aspherical surfaces within the image space, offering a flexible optical metrology tool for measuring aspherical surfaces. This approach is characterized by its ability to deliver rapid and cost-effective integration without the need for custom, complex optics.
- [Aspherical Surface Measurement a Cost-Effective and Fast Ai Solution](https://www.opticalperspectives.com/aspherical-surface-measurement-a-cost-effective-and-fast-ai-solution/) - Optical aspherical surfaces have become more widely used as they offer advantages such as improved image quality, compact design, increased light gathering, and reduced distortion. However, measuring aspherical surfaces presents challenges due to their non-spherical shapes. The primary difficulties include the complexity of surface geometries and the need for specialized metrology equipment. These challenges require advanced measurement techniques to ensure accurate characterization and quality control of aspherical surfaces in various applications. This paper introduces an innovative, AI-driven solution for the measurement of aspherical surfaces within the image space, offering a flexible optical metrology tool for measuring aspherical surfaces. This approach is characterized by its ability to deliver rapid and cost-effective integration without the need for custom, complex optics.
- [Aligning Reflecting Optics With Bessel Beams](https://www.opticalperspectives.com/aligning-reflecting-optics-with-bessel-beams-2/) - Bessel beams have found use in the alignment of transmissive optics for some time. They are also used for the alignment of reflecting optics when used in the imaging mode, that is, when the wavefront is near spherical. However, there are cases where it would be useful to use the Bessel beam for alignment of far-off axis aspheres to order to get the asphere aligned close enough to its final position that light will go through the system in the imaging mode. In another mode, the Bessel beam is used to determine the normal to a free form surface.
- [A new approach to Wavefront Sensing: AI Software With An Autostigmatic Microscope](https://www.opticalperspectives.com/a-new-approach-to-wavefront-sensing-ai-software-with-an-autostigmatic-microscope/) - The use of artificial intelligence (AI) software for wavefront sensing has been demonstrated in previous studies [1], [3]. In this work, we have developed a novel approach to wavefront sensing by coupling an AI software with an Autostigmatic Microscope (AM). The resulting system offers optical component and system testing capabilities similar to those of an interferometer used in double pass, but with several advantages. The AM is smaller, lighter, and less expensive than commercially available interferometers, while the AI software is capable of reading out Zernike coefficients, providing real-time feedback for alignment.
- [History of PSM Development](https://www.opticalperspectives.com/history-of-psm-development/)
- [Microns, Microns, Everywhere and All of Them Out of Line](https://www.opticalperspectives.com/microns-microns-everywhere-and-all-of-them-out-of-line/)
- [Complementary Aspects of Optical Alignment and Image Symmetry](https://www.opticalperspectives.com/complementary-aspects-of-optical-alignment-and-image-symmetry/) - INTRO: INTRODUCTION Almost all optical elements and systems are sym- metric about their optical axes which means there are only 5 degrees of freedom that will affect op- tical alignment. Likewise, stigmatic images of a point source of light imaged by a finite conjugate optical system have 5 types of symmetry. There is a part of the image that is symmetric about the centroid of the image, and there are 4 symmetries in the plane of the image, namely, even-even, odd-odd, even-odd and odd-even. We show there is a one-to-one correspondence between the im- age symmetries and the degrees of freedom op- tical elements can be moved to align them.
- [Transmission sphere calibration using a Fresnel zone CGH](https://www.opticalperspectives.com/transmission-sphere-calibration-using-a-fresnel-zone-cgh/) - ABSTRACT: There are two basic methods of calibrating a transmission sphere without use of an external artifact, statistical or shear. In the low NA range where shearing is the preferred method, the calibration is difficult to perform precisely because it is hard to measure the shear distance or rotation of the reference surface precisely. If the reference is a Fresnel zone CGH, then there are two centers of curvature that provide an axis that can be located precisely. We show theoretically and experimentally an absolute method of calibrating a TS using one rotational and one translational shear.
- [Systematic method of alignment using aberrations](https://www.opticalperspectives.com/systematic-method-of-alignment-using-aberrations/) - ABSTRACT: Talk is largely tutorial by has a two-fold motivation Definitions of kinds of alignmentInitial alignment steps to get light into alignment sensor-autostigmatic microscope, alignment telescope or interferometer Systematic alignment steps using the alignment sensor. Good idea to have a written procedure because many steps Alignment results using real hardware. Robert E. Parks, Benjamin F.
- [PHYSICAL RAY TRACING WITH BESSEL BEAMS](https://www.opticalperspectives.com/physical-ray-tracing-with-bessel-beams/) - Authors: Robert E. Parks (Optical Perspectives Group, LLC) and Daewook Kim (J. C. Wyant College of Optical Sciences, University of Arizona). INTRODUCTION Following the discovery of so called non-diffracting Bessel beams[1], they have been used for a number of exotic purposes such as trapping single atoms and aiding in the discovery of exoplanets. We discuss more
- [Free Psm Data Logging Software Available](https://www.opticalperspectives.com/free-psm-data-logging-software-available/) - A user of a PSM mentioned that it was too bad that data of spot positions could not be logged in the PSM Align software. This is true, data cannot be logged in the PSM Align software, but there is a version of the software designed for use with the centering station, LCS-PSM Align, that
- [New Paper Presented at OptiFab 2021](https://www.opticalperspectives.com/new-paper-presented-at-optifab-2021/) - During the SPIE Optifab Exhibition 18 - 21 October 2021, Robert (Bob) Parks presented a newly published paper. For more information about this continue reading... This paper is available to read on optiper.com:
- [Announcement of Re-Publication of “Optics and Optical Instruments—Preparation of Drawings for Optical Elements and Systems: A User’s Guide”](https://www.opticalperspectives.com/announcement-of-re-publication-of-optics-and-optical-instruments-preparation-of-drawings-for-optical-elements-and-systems-a-users-guide/) - FROM THE OSA PUBLISHING BOOKSHELF OSA Standards Committeeeds. Ronald K. Kimmel and Robert E. Parks We hope you appreciate this republication of ISO 10110 Optics and Optical Instruments—Preparation of Drawings for Optical Elements and Systems: A User's Guide, first published in 1995. This open-access republication is intended to give you a feel for the ISO 10110
- [Using the PSM as an Autocollimator](https://www.opticalperspectives.com/using-the-psm-as-an-autocollimator/) - The other day I got a call from a PSM user asking about calibration. What he was really asking about was the setting of the zero, or origin, on the video screen. CROSSHAIRS IN THE CENTER OF THE FIELD This is the same sort of “calibration” people talk about when using autocollimators, which are the
- [Adding Mechanical Datums to CGHs and Fresnel Mirrors](https://www.opticalperspectives.com/adding-mechanical-datums-to-cghs-and-fresnel-mirrors/) - In general, computer generated holograms (CGHs) and plane Fresnel mirrors (and lenses), made by the same techniques as CGHs, have optical “datums” or foci that are “rigidly attached” to the CGH or Fresnel plane substrate and move in six degrees of freedom with the substrate. THIS CONCEPT IS MORE EASILY SEEN BY CONSIDERING A GRATING
- [News & Announcements for December 2020](https://www.opticalperspectives.com/news-announcements-for-december-2020/) - How well can the Point Source Microscope (PSM) find a point in space? A POTENTIAL CUSTOMER FOR A PSM RECENTLY ASKED “WHAT IS THE ACCURACY/REPEATABILITY OF ALIGNMENT OF OPTICAL AXIS?” The question is a little ambiguous as to exactly what he was asking for, but my own experience in the lab is that the PSM
- [Two New Papers Presented With 2020 (VIRTUAL) SPIE Conference](https://www.opticalperspectives.com/two-new-papers-presented-with-2020-virtual-spie-conference/) - DURING THE SPIE OPTICS + PHOTONICS FREE DIGITAL FORUM (ONLINE ONLY) AUGUST 24-28 2020, ROBERT (BOB) PARKS PRESENTED TWO NEWLY PUBLISHED PAPERS. SEE THE PRESENTATION BY GOING DIRECTLY TO SPIE EXHIBITOR FORUM
- [News & Announcements for November 2020](https://www.opticalperspectives.com/news-announcements-for-november-2020/) - I am sorry to say I did not get to meet any of you personally at either the SPIE Optics and Photonics show in San Diego or the American Society for Precision Engineering Exhibit scheduled for Minneapolis in October. THE CENTERING STATION DOES PRECISION CENTERING WITHOUT THE NEED OF A ROTARY TABLE. THIS MAKES CENTERING
- [Measuring the Radius of Curvature of a Spherical Surface](https://www.opticalperspectives.com/measuring-the-radius-of-curvature-of-a-spherical-surface/) - DURING THE SPIE OPTICS + PHOTONICS FREE DIGITAL FORUM (ONLINE ONLY) AUGUST 24-28 2020, ROBERT (BOB) PARKS PRESENTED TWO NEWLY PUBLISHED PAPERS. SEE THE PRESENTATION BY GOING DIRECTLY TO SPIE EXHIBITOR FORUM
- [PSM Mounting Hardware](https://www.opticalperspectives.com/psm-mounting-hardware/) - Customers purchasing a PSM often ask me if we offer mounting hardware for the PSM like x-y-z stages. MY ANSWER HAS BEEN “NO”, BECAUSE THERE ARE SO MANY WAYS OF USING THE PSM THAT IT WOULD BE IMPOSSIBLE TO MEET EVERYONE’S DIFFERENT NEEDS. IN FACT, THE ANSWER IS “YES!” The centering station is a tall,
- [Can the PSM Find Best Focus of an F/25 Optical System?](https://www.opticalperspectives.com/can-the-psm-find-best-focus-of-an-f-25-optical-system/) - Can the PSM find best focus of an f/25 optical system to less than ± 10 μm? SOMEWHAT SURPRISINGLY, YES, TO ABOUT ± 2 ΜM. You scan axially through best focus several times and plot the number of pixels above threshold versus scan distance. The curve is quadratic and the derivative of the curve fit
- [The Microfinish Topographer and the Solar Telescope](https://www.opticalperspectives.com/the-microfinish-topographer-and-the-solar-telescope/) - The MicroFinish Topographer helped bring you this spectacular image of the sun. The smoothness criterion on the Daniel K. Inouye Solar Telescope primary mirror was a scatter specification. This was a problem in two respects, the mirror substrate was Zerodur and the scatter angle was too close to specular to measure with a scatterometer. The
- [Rapid Centering Small Lenses Using an Axicon Grating and the PSM](https://www.opticalperspectives.com/rapid-centering-small-lenses-using-an-axicon-grating-and-the-psm/) - A combination of the Auto Gain function of the Point Source Microscope (PSM) and the use of an Axicon grating make centering of severely misaligned lenses easy. The lenses in the cell are misaligned far enough that light in the center of the aperture barely makes it through the lens. The PSM video screen displays
- [How the PSM Caught a Potential Problem](https://www.opticalperspectives.com/how-the-psm-caught-a-potential-problem/) - Recently a customer was using the Point Source Microscope (PSM) to align a slow, singlet objective lens and find its focus. The customer had a plane retro mirror behind the objective and should have seen a nice round spot at best focus. Instead, he saw a vertical line image as in the following screen shot
- [News Announcement About What is Happening in 2018 for OPG](https://www.opticalperspectives.com/news-announcement-about-what-is-happening-in-2018-for-opg/) - For the last three years Optical Perspectives Group, LLC (OPG) had a licensing agreement with Trioptics-USA to manufacture and sell OPG products exclusively world-wide. OPTICAL PERSPECTIVES GROUP, LLC (OPG) AND TRIOPTICS-USA MUTUALLY DECIDE TO END LICENSING AGREEMENT Toward the end of last year it was becoming clear that this arrangement was not in the best
- [New Instructions for Using CaliBall](https://www.opticalperspectives.com/new-instructions-for-using-caliball/) - USING THE CALIBALLTM TO CALIBRATE INTERFEROMETER TRANSMISSION OR REFERENCE SPHERES USING THE RANDOM BALL TEST IS ALMOST FOOL PROOF. However, observing a few simple precautions will improve the results of the calibration. These precautions are detailed in the "Instructions for Using CaliBall" in approximately the order they should be followed. Read Instructions
- [MFT Microfinish Topographer Mentioned in Five Papers Given at Telescope Conference](https://www.opticalperspectives.com/mft-microfinish-topographer-mentioned-in-five-papers-given-at-telescope-conference/) - MFT was mentioned in five of the papers given at the SPIE Conference on Telescopes in Edinburgh, Scotland at the end of June 2016 by authors from six different international research organizations. PROC. SPIE 99055O, SEE MENTION OF MFT ON P. 19, FIG 18. The surface roughness measurements of a silicon plate with a multilayer
- [Why Is Optical Alignment So Important to Optical System Performance?](https://www.opticalperspectives.com/why-is-optical-alignment-so-important-to-optical-system-performance/) - The main reason is that the other two major factors in performance, optical design and optical fabrication, have already been improved to the very limits of what can be accomplished. After spending good money on a near perfect design and fabrication of optical components does it make any sense not to assemble them in perfect

## Pages

- [Home](https://www.opticalperspectives.com/) - Optical Perspectives Group Alignment Tools for Optimizing Opto-Mechanical System Performance Point Source Microscope A swiss army knife for your lab Point Source Microscope A complete, self-contained, portable metrology system. Nearly as precise as an interferometer, yet far more flexible and easy to use due to its small size, light weight and powerful software. Read more
- [Test](https://www.opticalperspectives.com/test/) - Optical Perspectives Group Alignment Tools for Optimizing Opto-Mechanical System Performance Point Source Microscope A swiss army knife for your lab Point Source Microscope A complete, self-contained, portable metrology system. Nearly as precise as an interferometer, yet far more flexible and easy to use due to its small size, light weight and powerful software. Read more
- [PSM Align Software](https://www.opticalperspectives.com/psm-align-software/) - PSM Align software Optical Perspectives Group is pleased to announce new Python based software for the Point Source Microscope (PSM) called PSM Align. From now on all PSMs will be shipped with PSM Align. PSM Align introduces several improvements over the LabView version, including the ability to zoom in video windows using the mouse scroll
- [Videos](https://www.opticalperspectives.com/videos/) - Videos Using the PSM on a CMM Watch Video Optics Valley Technical Series Webinar: A New Method of Optical Alignment Using Bessel Beams Watch Video Bob Parks on the Point Source Microscope, Alignment, and Optics Watch Video Alignment to Ball with PSM Watch Video Aligning Reflecting Optics with Bessel Beams Watch Video Axicon Grating Centering
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- [About Autocollimators](https://www.opticalperspectives.com/about-autocollimators/) - AUTOCOLLIMATOR The PSM is an autocollimator when the objective is removed because the pigtailed SM fiber laser is collimated inside the PSM. As an autocollimator the PSM has a capture range of +/- 1.5 degrees and an angle sensitivity of slightly less than 1 second of arc (about 4 microradians). The collimated beam is 8
- [About](https://www.opticalperspectives.com/about/) - ABOUT US Optical Perspectives Group Optical Perspectives Group specializes in low-cost, easy-to-use and accurate instruments for aligning and centering optics and optical systems. 7011 E Calle TolosaTucson, AZ 85750 520-529-2950 Support@OptiPer.com
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- [Testimonials](https://www.opticalperspectives.com/testimonials/) - Testimonials at Kreischer Optics "The Point Source Microscope is a great tool for all types of measurements. I'm retired but some years back we had Bob make a cementing station using the PSM. I had a project that had Germanium and Silicon lenses around 8" diameter I needed to center. The clear aperture was out
- [Citations](https://www.opticalperspectives.com/citations/) - Papers By Researchers/Customers Using the PSM Telescope Alignment Papers and Highlights Spectroscope Alignment Papers and Highlights Lens Centering Papers and Highlights Opto-mech Metrology Papers and Highlights Optical Testing Papers Using the PSM Contact Us For More Information on a Paper or Technique
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## Products

- [AI4Wave and PSM bundle](https://www.opticalperspectives.com/product/ai4wave-and-psm-bundle/) - AI4Wave upgrades your PSM into a precise wavefront measurement tool for various optical surfaces. REQUEST A QUOTE
- [Bessel Beam Projector](https://www.opticalperspectives.com/product/bessel-beam-projector/) - The Bessel beam projector includes an Axicon grating, an adjustable fold mirror for centering the source on the grating axis, and an FC/PC single-mode fiber coupler. A Bessel beam will emanate from the grating once a single-mode fiber is connected to the projector. When the Bessel beam is viewed with an autostigmatic microscope such as
- [PSM with Integrated 5-Axis Mount](https://www.opticalperspectives.com/product/psm-with-integrated-5-axis-mount/) - The PSM and integrated 5-axis mount are available as a package with micrometers as pictured or with Mitutoyo digital micrometers with 1 μm resolution as a package. REQUEST A QUOTE
- [MicroFinish Topographer (MFT)](https://www.opticalperspectives.com/product/microfinish-topographer-mft/) - Optical Perspective’s unique new MFT is a simple, low cost solution to surface roughness measurement. REQUEST A QUOTE Download Spec Sheet
- [Axicon Grating Centering Station](https://www.opticalperspectives.com/product/axicon-grating-centering-station/) - The Axicon Centering Station (ACS) offers precise lens alignment for cementing doublets and for assembling optical systems up to 250 mm in diameter. Featuring a motorized vertical stage with 900 mm travel, a digital encoder readout with 1µm resolution, and a damped 600 x 450 mm breadboard base, it provides stable, high-accuracy centering without the need for a rotary table. The ACS includes a Bessel beam projector to create a reference axis, a Point Source Microscope (PSM) as the centering detector, two fiber-coupled laser light sources, and two oilless vacuum pumps for holding tooling and lenses. REQUEST A QUOTE
- [The Point Source Microscope (PSM)](https://www.opticalperspectives.com/product/point-source-microscope/) - A complete, self-contained, portable metrology system. To learn more about the PSM's unique features and the origin of the PSM click here. Download Spec Sheet REQUEST A QUOTE
- [Leasing Options](https://www.opticalperspectives.com/product/leasing-options/)
- [Tip/Tilt Mount](https://www.opticalperspectives.com/product/tip-tilt-mount/) - The tip/tilt mount for the PSM is designed to give additional flexibility and adjustment for a means of mounting and use of the PSM.
- [CaliBall™ II](https://www.opticalperspectives.com/product/caliball-2/) - A horizontal interferometer calibration device. Learn more about the history of the CaliBall™ by downloading the PDF below. Download PDF
- [CALIBALL™ I](https://www.opticalperspectives.com/product/caliball-1/) - CaliBall™ I is for either horizontal or vertical interferometer set ups but it requires an x-y-z stage to position the CaliBall center at the transmission sphere focus. Learn more about the history of the CaliBall™ by downloading the PDF below. Download Instructions Download PDF
- [Microscope Objective Adapters](https://www.opticalperspectives.com/product/microscope-objective-adapters/) - These adapters are compatible with most major brands of infinity-corrected microscope objectives.
- [Silicon Nitride Balls](https://www.opticalperspectives.com/product/silicon-nitride-balls/) - These 0.5” (12.7 mm) diameter silicon nitride balls are Grade 5, the best quality available as a commodity item. The balls are round to 125 nm with a surface finish of 1.25 nm rms. They are near diffraction-limited convex mirrors with a reflectivity of about 11%, more than enough for most applications with the PSM.
- [Ball & Nest](https://www.opticalperspectives.com/product/ball-nest/) - Magnetic, kinematic seats for ½” balls having a controlled 0.5000” height from nest base to ball center.
- [Make Payment](https://www.opticalperspectives.com/product/make-payment/)
- [PSM Angular Measurement Calibration Package](https://www.opticalperspectives.com/product/psm-angular-measurement-calibration-package/) - Calibration package for Point Source Microscope Angular Measurement.
- [PSM Linear Magnification Calibration Package](https://www.opticalperspectives.com/product/psm-linear-magnification-calibration-package/) - A NIST traceable linear grating with 250 µm lp/mm spacing for calibrating the PSM magnification.
- [Right Angle Adapter (RAA)](https://www.opticalperspectives.com/product/right-angle-adapter-raa/) - The Right Angle Adapter (RAA) is a useful attachment for the Point Source Microscope (PSM) that adds flexibility in mounting the PSM by allowing the objective to be attached at right angles to the body.
- [PSM Precision Balls](https://www.opticalperspectives.com/product/psm-precision-balls/) - 10 Precision Balls for use with the PSM for alignment and assembly of optical systems.

## Downloads

- [Measuring The Four Paraxial Lens Parameters Using An Autostigmatic Microscope](https://www.opticalperspectives.com/download/measuring-the-four-paraxial-lens-parameters-using-an-autostigmatic-microscope-2/) - We describe a method of measuring the four paraxial lens parameters—the two radii, the center thickness, and the index—of a realistic-size positive lens using an autostigmatic microscope (ASM). The method is similar to meas- uring the radius of curvature of a concave mirror with an ASM but slightly more complex in that four character- istic distances must be measured to solve for the four unknown parameters. Once the four distances are measured, it is shown how to use an Excel spreadsheet and the add-in iterative “Solver” to find the four unknown param- eters. Finding the paraxial lens parameters is useful for troubleshooting a lens assembly that does not perform as expected due to mislabeling, the incorrect glass type used, insertion into the assembly backward, or for finding a replacement glass type.
- [The Structure Function As An Optical Surface Specification](https://www.opticalperspectives.com/download/the-structure-function-as-an-optical-surface-specification-c/) - The structure function is suggested as a means of specifying surface figure and roughness in order to avoid surface errors that have regions of high slope that produce unacceptable imaging performance.
- [A Practical Implementation Of The Random Ball Test](https://www.opticalperspectives.com/download/a-practical-implementation-of-the-random-ball-test-color/) - The random ball test for calibrating interferometer transmission spheres1 was reported about 8 years ago but there did not appear to be an ideal ball. Now, nearly ideal balls are available.
- [Using The Point Source Microscope (PSM) To Find Conjugates Of Parabolic And Elliptical Off-Axis Mirrors](https://www.opticalperspectives.com/download/using-the-point-source-microscope-psm-to-find-conjugates-of-parabolic-and-elliptical-off-axis-mirrors/) - Although the PSM is primarily an alignment instrument, it can also be used to determine the conjugates of parabolic and elliptical off-axis mirrors. By positioning the PSM at the sagittal and tangential foci of the mirrors, the conjugate distances of the mirror can be found using a laser range finder, for example. Knowing the sagittal and tangential radii of curvature (Rs and Rt), the vertex radius (Rv) is easily calculated. This information is used to verify that the mirror has been correctly manufactured and to aid in positioning the mirror in an optical system.
- [Use Of The Surface PSD To Investigate Near Specular Scatter From Smooth Surfaces](https://www.opticalperspectives.com/download/use-of-the-surface-psd-to-investigate-near-specular-scatter-from-smooth-surfaces/) - The Rayleigh Rice vector perturbation theory has been successfully used for several decades to relate the surface power spectrum of optically smooth reflectors to the angular resolved scatter resulting from light sources of known wavelength, incident angle and polarization. While measuring low frequency roughness is relatively easy, the corresponding near specular scatter can be difficult to measure. This paper discusses using high incident angle near specular measurements along with profile generated surface power spectrums as a means of checking a near specular scatter requirement.
- [Specifications: Figure And Finish Are Not Enough](https://www.opticalperspectives.com/download/specifications-figure-and-finish-are-not-enough/) - Several examples are given of optics apparently specified only by figure and finish. Although these optics met the specifications they did not produce good images. The presumed reason for the poor performance was the lack of a specification for mid-spatial frequency roughness. We show that a reasonable specification can be applied using the concept of a structure function, a mathematically simple function easily calculated from interferometric phase data at each pixel. An example wavefront is used to show how the specification can be developed from typical figure and finish specifications and include information about roughness in the mid-spatial frequency region.
- [Microfinish Topographer: Surface Finish Metrology For Large And Small Optics](https://www.opticalperspectives.com/download/microfinish-topographer-surface-finish-metrology-for-large-and-small-optics/) - The MicroFinish Topographer (MFT) is the result of an interest in directly measuring the surface roughness of large optics without the need for using replicas that may degrade the measurement data and that contaminate the surface. Once the MFT proved itself on large optics it was immediately suggested that a similar device should be designed for small optics. All this really took was turning the original MFT upside down and placing small specimens on a holder. This one device tests samples from 10 mm diameter to 10 m with phase measuring interferometry that does not need vibration isolation. Further, the MFT form factor makes it ideal for use in doing on-machine surface finish metrology.
- [In Situ Surface Roughness Measurement](https://www.opticalperspectives.com/download/in-situ-surface-roughness-measurement/) - Measuring surface roughness or finish is one the more difficult measurements to make on large mirrors or lenses. In general, the measurand is too large to place on the stage of a surface- roughness measuring microscope, so an indirect measurement must be made using replicas. The long mechanical path between interference objective and sample on traditional microscope based profilers make these instruments prone to vibration due to the environment which disturbs temporal phase shifting measurements.
- [Non-Contact Probe For On-Machine Metrology](https://www.opticalperspectives.com/download/non-contact-probe-for-on-machine-metrology/) - On-machine metrology is particularly important for diamond turning and grinding as it is difficult to remount and align a part if it does not meet off-line inspection criteria. There is also the issue of tool wear; a process that started well may fail part way through the cut, and if tool replacement is needed, it is vital to know that before removing the part. A means of rapid, non- contact, in situ profiling and roughness measurement could improve the productivity of diamond tool machining.
- [Method Of Alignment Using A Laser Tracker System](https://www.opticalperspectives.com/download/method-of-alignment-using-a-laser-tracker-system/) - Laser trackers are an accurate and efficient tool for finding the locations of features in a three- dimensional space but they rely on Spherically Mounted Retroreflectors (SMR) to return the laser beam to the tracker. If the feature cannot be contacted or it is not convenient to use an SMR another method must be used to follow the beam.
- [Measuring The Four Paraxial Lens Parameters Using An Autostigmatic Microscope](https://www.opticalperspectives.com/download/measuring-the-four-paraxial-lens-parameters-using-an-autostigmatic-microscope/) - We describe a method of measuring the four paraxial lens parameters—the two radii, the center thickness, and the index—of a realistic-size positive lens using an autostigmatic microscope (ASM). The method is similar to meas- uring the radius of curvature of a concave mirror with an ASM but slightly more complex in that four character- istic distances must be measured to solve for the four unknown parameters.
- [What Is A Point Source Microscope](https://www.opticalperspectives.com/download/what-is-a-point-source-microscope/) - As opposed to an ordinary bright field microscope that uniformly illuminates the full field of view so that a microscopic image of the full field is seen, a point source microscope has a single, very small point of illumination that lies on the axis of the microscope objective.
- [Measuring Wedge In A Window](https://www.opticalperspectives.com/download/measuring-wedge-in-a-window/) - One of the easier measurements to make with the PSM is the wedge in a nominally plane, parallel window. Since the PSM is an autocollimator when the objective is removed, the collimated beam is pointed at the window in question. With the PSM source turned up to the MAX mode, the beam reflected from the window is easy to see against a white sheet of paper under normal room lighting.
- [Measurement Of Radius Of Curvature](https://www.opticalperspectives.com/download/measurement-of-radius-of-curvature/) - The most basic use for the Point Source Microscope (PSM), or any autostigmatic microscope, is the measurement of the radius of curvature of concave surfaces.
- [Aligning Optical Elements To A Common Axis](https://www.opticalperspectives.com/download/aligning-optical-elements-to-a-common-axis/) - It is sometimes necessary to align a series of optical elements, lenses and mirrors, to a single, straight optical axis. What is required is a means of moving either the optical bench on which the elements are mounted along a straight line, or moving an autostigmatic microscope along the same line.
- [Aligning A Parabola To An Autocollimating Flat Mirror](https://www.opticalperspectives.com/download/aligning-a-parabola-to-an-autocollimating-flat-mirror/) - An autostigmatic microscope is a perfect way of aligning an autocollimating flat mirror to a parabola. The reason this alignment must be done is that a parabola only produces a perfect image of light from infinity when the light comes in parallel to the optical axis of the parabola. If the light is not parallel the image will be comatic, or have a tail that looks like a comet.
- [Swing Arm Optical Coordinate-Measuring](https://www.opticalperspectives.com/download/swing-arm-optical-coordinate-measuring/) - The swing arm optical coordinate-measuring machine (SOC), a profilometer with a distance measuring interferometric sensor for in situ measurement of the topography of aspheric surfaces, has shown a pre- cision rivaling the full aperture interferometric test. To further increase opti- cal manufacturing efficiency, we enhance the SOC with an optical laser triangulation sensor for measuring test surfaces in their ground state before polishing.
- [Practical Alignment Using An Autostigmatic Microscope](https://www.opticalperspectives.com/download/practical-alignment-using-an-autostigmatic-microscope/) - Auto-stigmatic microscopes (ASM) are useful for bringing centers of curvatures of lenses and mirrors to the centers of balls used as part of an alignment fixture. However, setting up the fixture to get the balls used for alignment in a straight line to represent the optical axis generally requires another piece of equipment. We show that within a practical range, the autocollimation mode of a modern ASM can be used to align balls to an axis with about the same precision as they could be aligned with an alignment telescope, or laser tracker. As a lead in to this topic, we discuss our meaning of alignment, the means of positioning optically important features such as centers of curvature and foci to the coordinates specified on assembly drawings. Finally, we show a method of using an ASM along with other tooling to align a toroidal mirror using its foci.
- [Lens Centering Using The Point Source Microscope (PSM)](https://www.opticalperspectives.com/download/lens-centering-using-the-point-source-microscope-psm/) - Precision lens centering is necessary to obtain the maximum performance from a centered lens system. A technique to achieve precision centering is presented that incorporates the simultaneous viewing through the upper lens surface of the centers of curvature of each element as it is assembled in a lens barrel. This permits the alignment of the optical axis of each element on the axis of a precision rotary table which is taken as the axis of the assembly.
- [Conjugate Selection For Precision Lens Centering](https://www.opticalperspectives.com/download/conjugate-selection-for-precision-lens-centering/) - The concept of centering a precision, symmetric lens system using a high-quality rotary table and an auto-focusing test instrument are well known. Less well known are methods of finding convenient, or easily accessible, lens conjugates on which to focus while performing the centering operation. We introduce methods of finding suitable conjugates and cen- tering configurations that lend themselves to practical centering solutions.
- [Centering With The PSM](https://www.opticalperspectives.com/download/centering-with-the-psm/) - Centering with the Point Source Microscope (PSM) is a perfect application. When a spot of light from the objective focus is reflected back from a concave surface sitting on a rotary table, it will sweep out a circle on the video screen as the table is rotated unless the center of curvature of the surface lies precisely on the axis of rotation of the table.
- [Calibration Of Interferometer Transmission Spheres](https://www.opticalperspectives.com/download/calibration-of-interferometer-transmission-spheres/) - Background: As the tolerances on optical figure get tighter and as the need to provide traceable test methods to fulfill I S 0 9000 standards becomes greater, the more there is the need for a ro- bust and reliable method to determine the residual error in interferometer test optics.
- [A Short History of the CaliBall(TM) and the Random Ball Test](https://www.opticalperspectives.com/download/a-short-history-of-the-caliballtm-and-the-random-ball-test/) - Back in the late 1990’s NIST had a number of firms that wanted to send their interferometer transmission spheres there for calibration but NIST was not in this sort of calibration business. While I was at NIST consulting for Chris Evans in the Precision Machining Facility we thought of the idea of a self-calibration test for transmission spheres that was a spherical analog of the plane surface test1 used to self-calibrate interferometric surface roughness testing microscopes.
- [What is an ASM and the Origin of the PSM](https://www.opticalperspectives.com/download/what-is-an-asm-and-the-origin-of-the-psm/) - When most people think of a microscope it is one that works in transmission with the light source on one side of the sample and the microscope objective and eyepiece on the other. An autostigmatic microscope (ASM) works in reflection, just like an autocollimator, so the light source is in the microscope body, and is almost always introduced via a beamsplitter close to the objective but between objective and eyepiece.

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