Santa Barbara Research Center has been exploring technology related to the design, tolerance, and alignment of wide-field, all-reflective sensors for multispectral earth observation. The goals of this study are to design an optical system with reduced fabrication risks, to develop a detailed tolerance budget and to demonstrate our ability to align the system to a tolerance of 0.05 waves rms at 0.6328 microns. The final optical system is a three-mirror unobscured telescope. It is telecentric and flat field over 15 degrees at F/4.5, and achieves diffraction-limited imagery at visible wavelengths.
This paper describes the results of the design effort, the tolerance exercise, and a metrology approach for the optics fabrication. The alignment results are discussed in a separate paper.1 Three conclusions are made: 1) design of unobscured optical systems is still best approached using fundamental optical design principles, 2) time spent in careful modeling of fabrication, testing, and alignment interactions will result in more relaxed tolerances and a higher probability of success for the assembled system, 3) precise metrology of optical surfaces can be achieved with fairly simple techniques.