Patent ID: 8692880
Filing Date: 2014-04-08
Classification: G01B,G06T

Abstract:
1. An image correlation displacement sensor for measuring a positional displacement relative to a target surface, the image correlation displacement sensor comprising: an illumination portion which emits illumination light to the target surface to produce a speckle field; an imaging portion including a detector, a first optical path which is used to capture a plurality of images of the speckle field produced on the target surface and is inclined with respect to a normal to the target surface within a distance of the target surface to capture an image, and a second optical path which is used to capture a plurality of images of the speckle field produced on the target surface and is inclined with respect to the first optical path within a distance of the target surface to capture an image, the imaging portion including an element which deflects at least one of the first and second optical paths, wherein the first and second optical paths enter different parts of the detector; and a processing portion which measures a displacement relative to the target surface along a direction which includes a component normal to the target surface in accordance with determining a first image displacement based on image correlation processing using images from the plurality of images captured in the first optical path and determining a second image displacement based on image correlation processing using images from the plurality of images captured in the second optical path, and determining the component normal to the target surface based on a relationship between the first and second image displacements.