Absolute Calibration of Slope Measuring Tests

Researchers at the University of Arizona have developed a system for testing the figure and finish of optical surfaces or any other curved surface using a Shack-Hartmann type of method, wherein a pattern can be projected onto the surface and then its returned image can be analyzed. The patterns can be varied to optimize the returned information regarding slope details of a variety of shapes. The SCOTS technology can be used on a rough surface as well as on the nearly-finished surface.

Background: 
Testing of aspheric and freeform surfaces can be challenging at best using conventional interferometric techniques. Interferometers deliver precise information about surface departures from the ideal surface, but require the finish and polishing to be at a relatively advanced stage. Typically, multiple instruments at different wavelengths must be used to cover testing from the initial polishing runs to the final runs.

Advantages:

• One set-up can measure from rough polishing to finish
• Accuracy and precision are comparable to interferometers
• Can measure all sizes and shapes

Applications:

• Optical component surface metrology
• Surface figure and finish testing of cars, boats, and other curved surfaces