Simultaneous alignment and figure testing of optical system components via aberration measurement and reverse optimization.

Abstract

Optical component alignment and testing using reverse optimization has been investigated for different measurement methods and optical systems. The methods discussed were ray aberration measurement and wavefront aberration measurement. The methods were applied to real and simulated optical systems and compared. A testbed was designed to measure ray aberrations by means of physical raytracing of a three-mirror telescope in order to align the telescope by means of ray aberration measurement and reverse optimization, a technique of computer aided alignment. Ray aberration measurements were used to align the three-mirror telescope. Experimental results and improvements to the technique are discussed. Wavefront aberration methods are described and compared to ray aberration measurements. The wavefront aberration method was more easily used with systems with low nominal aberrations and when figure testing is desired. The ray aberration technique is most useful with systems of large aberration when capture range may be a problem and when component figure is well known. The method of reverse optimization is shown to work for wavefront aberration measurements in computer simulations using a Cassegrainian telescope, Cooke triplet and afocal two-Petzval telescope. Component figure errors and misalignments were determined simultaneously with sufficient spatial sampling of the wavefront aberrations. Surface parameters and component alignments were used as optimization variables. The effects of gaussian noise on the wavefront data were simulated for misalignment of the two-Petzval design. Results showed that noise can be compensated by the use of large numbers of optimization targets. Wavefront aberration measurements and reverse optimization were used to align a laboratory two-Petzval system to verify the results of the simulations.