Blog

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 […]

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 […]

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 […]

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 […]

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.

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.