1 April 1975 New Concepts in Projection Mask Aligners
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A new concept (the annular field optical system) makes it possible to avoid the extreme complexity of conventional projection mask alignment objectives. This has been done in a new, extremely simple, all-reflecting optical system that consists of two, concentric, spherical mirrors. A monolithic block consisting of three mutually perpendicular plane mirrors is used to fold the system into a configuration that makes possible an inherently synchronous, simple scanning arrangement. Partially coherent illumination is used to increase the effective MTF without decreasing the depth of focus.
A. Offner, A. Offner, } "New Concepts in Projection Mask Aligners," Optical Engineering 14(2), 142130 (1 April 1975). https://doi.org/10.1117/12.7978742 . Submission:

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