US 5,822,066 A · Point diffraction interferometer and pin mirror for use therewith

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.

Claims74

Dependent claims

A light receiving apparatus for use in an interferometer with a light source emitting light with a wavelength, .lambda., and with a test object with a numerical aperture, NA, the light receiving apparatus comprising:

a first pin mirror having a first reflective surface with a largest cross-width dimension that is less than the wavelength of said light divided by the numerical aperture of said test object, .lambda./NA, said reflective surface disposed to diffract the received light to generate a first light beam.

An apparatus for detecting at least one optical characteristic of a test object, the apparatus comprising:

a light source for generating a light beam;
a beam splitter disposed to receive said light beam from said light source, said beam splitter dividing said received light beam into probe and reference beams;
a probe pin mirror arranged to receive said probe beam from said beam splitter, said probe pin mirror diffracting said probe beam and directing the diffracted probe beam toward said test object;
and
a reference pin mirror arranged to receive said reference beam from said beam splitter, said reference pin mirror diffracting said reference beam and directing the diffracted reference beam in a direction to interfere with said probe beam reflected from said test object to generate an interference pattern indicative of at least one optical characteristic of said test object.

2 more elements

Dependencies are inferred from the claim text.

Point diffraction interferometer and pin mirror for use therewith

Life of this patent

Point diffraction interferometer and pin mirror for use therewith

Life of this patent

Abstract

Claims74