Optical interferometric system for measurement of a full-field thickness of a plate-like object in real time

Patent metadata

Field	Value
Publication number	US-9952034-B2
Application number	US-201715609862-A
Country	US
Kind code	B2
Filing date	May 31, 2017
Priority date	Jun 28, 2016
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

An optical interferometric system for measurement of a full-field thickness of a plate-like object in real time includes two light sources, two screens, two image capturing devices, and an image processing module. The light sources radiate incident lights toward a reference point on the plate-like object in respective directions to produce respective interference fringe patterns (IFPs). The image capturing devices capture light intensity distribution images respectively of the IFPS imaged respectively on the screens. The image processing module calculates a fringe order at the reference point according to the light intensity distribution images, and obtains a full-field thickness distribution of the plate-like object according to the fringe order.

First claim

What is claimed is:

1. An optical interferometric system for measurement of a full-field thickness of a plate-like object in real time, said optical interferometric system comprising:
a first light source for radiating a first incident light in a first direction toward a reference point located on a surface of the plate-like object to produce a first interference fringe pattern (IFP);
a second light source for radiating a second incident light in a second direction different from the first direction toward the reference point to produce a second IFP, the first incident light and the second incident light being coherent, having spherical wavefronts, and radiating the plate-like object with the spherical wavefronts;
a first screen and a second screen for allowing the first and second IFPs to be imaged thereon, respectively;
a first image capturing device and a second image capturing device that are disposed to face said first screen and second screen, respectively, and that are configured to respectively capture first and second light intensity distribution images respectively of the first and second IFPs imaged respectively on said first and second screens; and
an image processing module that is electrically connected to said first image capturing device and said second image capturing device, and that is configured to
convert the first and second light intensity distribution images into digital data,
calculate a fringe order at the reference point according to digital data, and
obtain a full-field distribution of the thickness of the plate-like object according to the fringe order.

2. The optical interferometric system of claim 1 , wherein said image processing module is configured to calculate the fringe order by obtaining a first relative phase of the first IFP and a second relative phase of the second IFP, and calculating the fringe order based on the first and second relative phases.

3. The optical interferometric system of claim 2 , wherein said image processing module is configured to calculate the fringe order N 1 at the reference point located at coordinates (x 0 , y 0 ) based upon

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Assignees

• Univ Nat Tsing Hua

Inventors

• Wang Wei-Chung
• Sung Po-Chi

Classifications

• G01B11/06 Primary

  for measuring thickness {; e.g. of sheet material (thickness measurement by thermal means G01B21/085)} · CPC title

• G01B9/02019

  contacting different points on same face of object · CPC title

• G01J9/04

  by beating two waves of a same source but of different frequency and measuring the phase shift of the lower frequency obtained · CPC title

• G01B2290/45

  Multiple detectors for detecting interferometer signals · CPC title