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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.

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.

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.

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.

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.

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.