Point diffraction interferometer and pin mirror for use therewit

Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer

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356354, 356360, G01B 902

Patent

active

058220666

ABSTRACT:
This invention includes a pin mirror arranged to receive light, preferably from a laser source. The pin mirror has a reflective surface that diffracts and reflects the received light to generate a diffraction-limited spherical wavefront. The pin mirror can reflect the wavefront in a predetermined direction by angling the pin mirror's reflective surface with respect to the direction of travel of the light incident to the pin mirror. The capability of the pin mirror to generate a diffraction-limited spherical wavefront and to direct the wavefront in a predetermined direction provides the capability to test objects or systems with relatively high numerical apertures, and yet allows for a reduction in the number and criticality of the properties of optical elements that would otherwise be required in an interferometer. The invention also includes several embodiments of interferometers that incorporate one or more pin mirrors to generate probe and reference beams used to generate an interference pattern indicative of one or more characteristics of a test object or system.

REFERENCES:
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patent: 4682025 (1987-07-01), Livingston et al.
patent: 4872755 (1989-10-01), Kuchel
patent: 5076695 (1991-12-01), Ichihara
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patent: 5504578 (1996-04-01), Kopf
patent: 5548403 (1996-08-01), Sommargren
patent: 5557408 (1996-09-01), Kanaya
patent: 5675413 (1997-10-01), Prikryl et al.
"A 3-D Numerical Study of Pinhole Diffraction to Predict the Accuracy of EUV Point Diffraction Interferometry," K.A. Goldberg et al., OSA TOPS on Extreme Ultraviolet Lithography, 1996, vol. 4, pp. 133-137.
"Phase Shifting Diffraction Interferometry for Measuring Extreme . . . " Gary E. Sommargren, OSA TOPS on Extreme Ultraviolet Lithography 1996, vol. 4, pp. 108-112.
Optical Shop Testing, "Common Path Interferometers," Section 3.7 Point Diffraction Interferometer, pp. 97-98, editor Daniel Malacara, 1978.
"Device Profiles Optics over Wide Spectral Range," Kristin Lewotsky Laser Focus World, pp. 41-42, Jan. 1997.

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