US 7,599,074 B2 · Grating angle magnification enhanced angular sensor and scanner

Abstract

An angular magnification effect of diffraction is exploited to provide improved sensing and scanning. This effect is most pronounced for a normal or near-normal incidence angle in combination with a grazing diffraction angle, so such configurations are preferred. Angular sensitivity can be further enhanced because the width of the diffracted beam can be substantially less than the width of the incident beam. Normal incidence configurations with two symmetric diffracted beams are preferred, since rotation and vertical displacement can be readily distinguished. Increased sensitivity to vertical displacement can be provided by incorporating an interferometer into the measurement system. Quad cell detectors can be employed to provide sensitivity to rotation about the grating surface normal. A 2-D grating can be employed to provide sensitivity to angular displacements in two different planes (e.g., pitch and yaw). Combined systems can provide sensitivity to vertical displacement and to all three angular degrees of freedom.

Claims23

Dependent claims

Apparatus for measuring a change of angular orientation of a test object, the apparatus comprising;

an optical source providing an incident beam of substantially monochromatic optical radiation to said test object at an angle of incidence θi, wherein a diffraction grating disposed on said test object is illuminated by said incident beam and provides a first diffracted beam having a first diffraction angle θd1 responsive to said incident beam;
wherein for a reference angular orientation of said test object, said incident beam and said first diffracted beam define a first diffraction plane;
a first optical detector receiving said first diffracted beam and providing a first output responsive to a position of said first diffracted beam on said first detector in said first diffraction plane;
wherein a first change ε1 of angular orientation of said test object in said first diffraction plane relative to said reference angular orientation induces corresponding changes Δθi of said angle of incidence and Δθd1 of said first diffraction angle;
wherein Δθi=ε1 and wherein θi and θd1 are selected such that Δθd1 is substantially greater than ε1.

2 more elements

Dependencies are inferred from the claim text.

Grating angle magnification enhanced angular sensor and scanner

Life of this patent

Grating angle magnification enhanced angular sensor and scanner

Life of this patent

Abstract

Claims23