Abstract: An encoder for providing a conical array of temporally phased pulse beams. A pulse is inserted and continuously recirculated around an optical ring. The pulse is amplified during each circulation and a portion of the pulse is emitted at the end of each circulation. The encoder includes means for spatially separating each emitted pulse to provide a conical array of beams at a constant field angle relative to the optical axis of propagation.

Abstract: An optical system providing a new field lens corrector group for a two mirror telescope. The field group corrector has a negative net power and allows the resulting system to have a long back focus and low obscuration while covering a wide field of view. The field corrector group provides the overall system with good Petzval curvature aberration correction characteristics because the aberration of the corrector group is of opposite sign to the Petzval curvature aberration of the two mirror system. The negative field corrector group is designed to increase the f number speed of the two mirror system.

Abstract: A viewing system for an annular projection system, particularly useful to provide a view of a semiconductor wafer on which an image of a integrated circuit mask pattern has been projected using an annular field projection system in which the field of view can be as large as the large dimension of that portion of the annular region subtended by the wafer thereby permitting ideal coarse alignment of the mask and wafer. The system further includes means to illuminate the mask and wafer separately and in different colors to thereby simplify the distinction of one from the other in the combined image thus facilitating the alignment task.