Patent ID: 7075721

Claim:
An optical imaging system for producing images with deep-ultraviolet light comprising: an arrangement of optical elements aligned along a common optical axis and exhibiting with respect to a beam of deep-ultraviolet light an intrinsic birefringence that varies with both inclination of the beam's rays to the optical axis and angular orientation of the beam's rays around the optical axis; the optical elements being arranged with respect to the beam of deep-ultraviolet light in a progression that renders an accumulated birefringence less sensitive to the angular orientation of the beam's rays around the optical axis; and a compensating optic exhibiting a radially symmetric birefringence in a sense opposite to the accumulated birefringence so that together with the arrangement of optical elements, the accumulated birefringence of the beam of deep-ultraviolet light is reduced with respect to both the inclination of the beam's rays to the optical axis and the angular orientation of the beam's rays around the optical axis, wherein the compensating optic is located within a telecentric object space in which chief rays of object points extend substantially parallel to the optical axis in positions that are variously offset from the optical axis.