CPC G02B 5/1866 (2013.01) [G02B 5/18 (2013.01); G02F 1/31 (2013.01); G03F 1/44 (2013.01); G03F 7/2024 (2013.01); G03F 7/70616 (2013.01); G03F 7/70633 (2013.01); G03H 1/26 (2013.01); G02B 5/1861 (2013.01)] | 20 Claims |
1. A method comprising:
using a first aperture plate to measure a first-axis diffraction of a composite grating, wherein the first aperture plate has a first pair of radiation-transmitting regions disposed along a first diametrical axis and on opposite sides of an optical axis; and
using a second aperture plate, complementary to the first aperture plate, to measure a second-axis diffraction of the composite grating, wherein the second aperture plate has a second pair of radiation-transmitting regions disposed along a second diametrical axis and on opposite sides of the optical axis, wherein the second diametrical axis is substantially perpendicular to the first diametrical axis, and wherein the first-axis is substantially perpendicular to the second-axis.
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