Automatic calibration optical interferometer and automatic calibration method of optical interferometer

Patent metadata

Field	Value
Publication number	US-10890429-B2
Application number	US-201916379721-A
Country	US
Kind code	B2
Filing date	Apr 9, 2019
Priority date	Dec 27, 2018
Publication date	Jan 12, 2021
Grant date	Jan 12, 2021

Abstract

An automatic calibration optical interferometer comprises: a light source; an optical interference assembly, which divides a low coherent light into a first and a second incident light; an optical sampling assembly, with a first end receiving the first incident light and a partially reflective window at the second end being configured to divide the first incident light into a first reflected light and a first penetrating light configured to be emitted to the test sample; an optical reference assembly, with a reference mirror and an actuator, wherein the optical sampling assembly emits the second incident light to the reference mirror to generate a second reflected light, and the actuator moves the reference mirror; a polychromator, which outputs a displacement signal according to an optical path difference variation between the first and second reflected lights; and a displacement controller, which controls the actuator according to the displacement signal.

First claim

What is claimed is:

1. An automatic calibration optical interferometer, comprising:
a light source configured to emit a low coherent light;
an optical interference assembly coupled to the light source and configured to divide the low coherent light into a first incident light and a second incident light, wherein the optical interference assembly is implemented by a coupler or a splitter;
an optical sampling assembly coupled to the optical interference assembly, wherein the optical sampling assembly comprises a first end and a second end, the first end couples to the optical interference assembly to receive the first incident light, the second end is configured to face a test sample, a partially reflective window at the second end is configured to divide the first incident light into a first reflected light and a first penetrating light, and the first penetrating light is configured to be emitted to the test sample;
an optical reference assembly coupled to the optical interference assembly, wherein the optical reference assembly comprises a reference mirror and an actuator, the optical reference assembly receives the second incident light and emits the second incident light to the reference mirror so as to generate a second reflected light, and the actuator is configured to move the reference mirror;
a polychromator coupled to the optical interference assembly, wherein the polychromator is configured to output a displacement signal according to an optical path difference variation which is derived from the first optical path of the first reflected light and the second optical path of the second reflected light; and
a displacement controller electrically connecting to the polychromator and configured to control the actuator according to the displacement signal, wherein the reference mirror is moved with the optical path difference variation by the actuator, and a modified optical path of the second reflected light equals to a sum of a second optical path of the second reflected light and the optical path difference variation.

2. The automatic calibration optical interferometer of claim 1 , wherein the partially reflective window is made of glass or polymer material.

3. The automatic calibration optical interferometer of claim 1 , wherein an energy of the first reflected light is less than an energy of the first penetrating light.

4. The automatic calibration optical interferometer of claim 1 , wherein the partially reflective window comprises an anti-reflective coating.

5. The automatic calibration optical interferometer of claim 1 , wherein the optical sampling assembly further comprises a switching device at the second end, the partially reflective window and another partially reflective window are disposed on the switching device, two reflected coefficients of said two partially reflective windows are different, and the switching device is configured to select one of said two partially reflective windows to receive the first incident light.

6. The automatic calibration optical interferometer of claim 1 , wherein an energy ratio of the first reflected light to the first incident light is from 0.1 to 5%, and an energy ratio of the first penetrating light to the first incident light is from 95.0% to 99.9%.

7. An automatic calibration method of optical interferometer comprising:
emitting a low coherent light by a light source;
dividing the low coherent light into a first incident light and a second incident light by an optical interference assembly, wherein the optical interference assembly is implemented by a coupler or a splitter;
receiving the first incident light by a first end of an optical sampling assembly;
dividing the first incident light into a first reflected light and a first penetrating light by a partially reflective window disposed on a second end of the optical sampling assembly, wherein the first penetrating light emits to a test sample;
receiving the second incident light by an optical reference assembly and emitting the second incident light to a reference mirror for generating a second reflected light;
receiving the first reflected light and the second reflected light by a polychromator and outputting a displacement signal according to an optical path difference variation which is derived from the first optical path of the first reflected light and the second optical path of the second reflected light; and
controlling an actuator of the optical reference assembly by a displacement controller according to the displacement signal for moving the reference mirror, wherein the reference mirror is moved with the optical path difference variation by the actuator, and a modified optical path of the second reflected light equals to a sum of a second optical path of the second reflected light and the optical path difference variation.

8. The automatic calibration method of optical interferometer of claim 7 further comprising:
after the first penetrating light emits to the test sample, receiving a sampling light reflected from the test sample by the polychromator, wherein the sampling light emits through the partially reflective window to the polychromator along the optical sampling assembly.

9. The automatic calibration method of optical interferometer of claim 7 further comprising:
before the first end of the optical sampling assembly receives the first incident light,
selecting one of the partially reflective window and another partially reflective window to receive the first incident light according to a reflectivity of the test sample by a switching device, wherein two reflected coefficients of said two partially reflective windows are different.

Assignees

• Ind Tech Res Inst

Inventors

• Chiang Hung Chih
• Chang Cheng Yi
• Chang Ting Wei
• Chang Chi Shen

Classifications

• G01B2290/60

  Reference interferometer, i.e. additional interferometer not interacting with object · CPC title

• G01B9/0209 Primary

  Low-coherence interferometers · CPC title

• G01B9/02029 Primary

  Combination with non-interferometric systems, i.e. for measuring the object · CPC title

• G01B9/02067

  by electronic control systems, i.e. using feedback acting on optics or light · CPC title

• G01B9/02072 Primary

  by calibration or testing of interferometer · CPC title