Joseph M. Geary

Analyzing optics test data on rectangular apertures using 2-D Chebyshev polynomials

We use the two-dimensional Chebyshev polynomials as the basis for decomposition of test data over rectangular apertures, particularly for anamorphic optics. This includes simple optics such as cylindrical lenses and mirrors as well as complex optics, such as aspheric cylindrical optics. The new basis set is strictly orthogonal over rectangles of arbitrary aspect ratio and they correspond well with the aberrations of systems containing such type of optics. An example is given that applies the new basis set to study the surface figure error of a cylindrical Schmidt corrector plate. It is not only an excellent fitting basis but also can be used to flag misalignment errors that are critical to fabrication.

Data Analysis In Fiber Optic Testing Of Cylindrical Optics

Optical fiber testing of positive power cylindrical optics is shown to be bisensitive. This means that the resulting interferogram is twice as sensitive along the cylindrical (zero power) axis as along the orthogonal (power) direction. The analysis of such interferograms is discussed.

Testing Cylindrical Lenses

Two new techniques for testing cylindrical lenses are discussed and compared. One makes use of an optical fiber as a cylindrical reference; the other utilizes diffraction through a slit.

Schmidt-like corrector plate for cylindrical optics

We report initial results on designing and manufacturing a Schmidt-like corrector plate for a commercial off-the-shelf cylindrical lens, eliminating the cylindrical equivalent of its spherical aberration. The corrector is made by figuring the correction profile onto a precision glass window, which is subsequently aligned to the cylindrical lens. We have successfully fabricated the first plate and applied it in an interferometric test of a near-cylinder optic. The interferometric data from before and after applying the corrector demonstrates that the modified optic produces a cylindrical test wavefront with 25× reduction compared to the uncorrected case.

Introduction to Optical Testing

This volume in the SPIE Tutorial Text series presents a practical approach to optical testing, with emphasis on techniques, procedures, and instrumentation rather than mathematical analysis. The author provides the reader with a basic understanding of the measurements made and the tools used to make those measurements. Detailed information is given on how to measure and characterize imaging systems, perform optical bench measurements to determine first- and third-order properties of optical systems, set up and operate a Fizeau interferometer and evaluate fringe data, conduct beam diagnostics (such as wavefront sensing), and perform radiometric calibrations.

Retrace error: a case study

An f/10.3 lens with 6 waves of spherical aberration was tested on a Fizeau interferometer using a standard ZYGO retro sphere. It was found that this configuration led to retrace error difficulties. A longer radius retro sphere yielded results in much better agreement with theory.

Passive optical lane position monitor

A laboratory prototype of a passive optical lane position monitor has been designed, built, and tested. The sensor head is simple and consists of two parts: a cylindrical lens, and a position sensitive detector. The amplifier/processing electronics which provides the position signal is compact and lightweight. No complex software or computer is needed. Sensor performance was validated both in the laboratory and in the field. The prototype was tested in sunlight over a range of solar angles from dawn to dusk. It was even tested at night with illumination provided by headlights. The bottom line is that, for such a simple system, the sensor worked quite well. This opens up possibilities for its use as a practical tool in vehicle/highway management.

Modeling point diffraction interferometers

The point diffraction interferometer (PDI) is modeled using the GLAD diffraction code. Behavior of the interference fringe pattern is examined as a function of F-number, aberration type, and lateral and axial translation of the PDI.

Separating misalignment from misfigure in interferograms on cylindrical optics.

This paper presents an analytical method that allows for unambiguous separation of misalignment from the interferometric measurement of cylindrical optics with rectangular apertures. This method not only removes the misalignment-induced aberration from the measured wavefront data, but also yields the amount of misalignment in the test setup. We verified this method during testing of a convex cylindrical optic.

Overview of cylindrical optics testing using a fiber optic reference

The use of a fiber optic reference to test cylindrical optics in a Fizeau interferometer configuration is described. (Note: this presentation was accompanied by a short video demonstration).