Fabrication of Large Off-axis Optics

Abstract

The construction of very large optical telescopes can be prohibitively costly due to the massive weight of conventional primary mirrors. The cost of such telescopes can be reduced by the use of a segmented lightweight primary mirror. An Itek process, computer controlled optical surfacing (CCOS), is ideally suited for manufacturing the off-axis aspheric segments. During CCOS operations, a subaperture tool is moved across the optic surface under accurate computer control. By altering the time that the machine grinds or polishes each surface region, accurate and rapid figure progress can be achieved. This CCOS technology has fabricated seven thin, 2-meter, off-axis, aspheric optics and a lightweighted, active, off-axis mirror. Also, a large active off-axis aspheric is presently being manufactured.