Apparatus for measure of coherence of light source for holographic display and method thereof

Patent metadata

Field	Value
Publication number	US-2020182701-A1
Application number	US-201916552940-A
Country	US
Kind code	A1
Filing date	Aug 27, 2019
Priority date	Dec 5, 2018
Publication date	Jun 11, 2020
Grant date	—

Abstract

A method and an apparatus for measuring a coherence of a light source of a holographic display through steps of: photographing an interference pattern generated by light output from the light source; obtaining an interference pattern feature information with respect to the interference pattern from an interference pattern image of the interference pattern; and measuring the coherence of the light source based on the interference pattern feature information, are provided.

First claim

What is claimed is:

1 . An apparatus for measuring a coherence of a light source of a holographic display, the apparatus comprising:
an image measurement unit configured to photograph an interference pattern generated by light output from the light source; a feature information extractor configured to obtain an interference pattern feature information with respect to the interference pattern from an interference pattern image of the interference pattern; and a coherence measurement unit configured to measure the coherence of the light source based on the interference pattern feature information.

2 . The apparatus of claim 1 , wherein
the interference pattern feature information is an average of all brightness values on a straight line parallel to a vertical axis of the interference pattern image when the interference pattern is in a vertical direction.

3 . The apparatus of claim 1 , wherein
the interference pattern feature information is an average of all brightness values on a straight line parallel to a horizontal axis of the interference pattern image when the interference pattern is in a horizontal direction.

4 . The apparatus of claim 1 , wherein
the coherence measurement unit is further configured to calculate a contrast of the interference pattern feature information and determine a rotation angle of the interference pattern which maximizes the contrast.

5 . The apparatus of claim 4 , wherein
the contrast is calculated by dividing a difference between a maximum value of the interference pattern feature information and a minimum value of the interference pattern feature information by a sum of the maximum value and the minimum value.

6 . The apparatus of claim 4 , further comprising
an analyzing processor configured to analyze influence of characteristic information of components of the light source on the coherence by using a neural network based on the rotation angle.

7 . The apparatus of claim 6 , wherein
the light source includes a spatial filter and a collimator; and the characteristic information includes at least one of a lens focal distance of the spatial filter, a lens focal distance of the collimator, a size of an opening of the light source or a pin hole, a diameter of a collimating lens, a diameter of aspheric lens, and a degree of alignment of incident light.

8 . The apparatus of claim 6 , wherein when the analyzing processor analyzes the influence of the interference pattern feature information, the analyzing processor performs machine learning by using the neural network based on a training set including the characteristic information of the light source mapped to interference pattern feature information having a high contrast.

9 . The apparatus of claim 8 , wherein
the analyzing processor is further configured to feedback an optimal characteristic value for the light source determined by a result of the machine learning through the neural network.

10 . The apparatus of claim 1 , further comprising:
a shear interferometer configured to receive the light and represent a degree of the coherence of the light source through the interference pattern, wherein when the image measurement unit photographs the interference pattern, the image measurement unit photographs the interference pattern represented on the shear interferometer.

11 . A method for measuring a coherence of a light source of a holographic display, the method comprising:
photographing an interference pattern generated by light output from the light source; obtaining an interference pattern feature information with respect to the interference pattern from an interference pattern image of the interference pattern; and measuring the coherence of the light source based on the interference pattern feature information.

12 . The method of claim 11 , wherein
the interference pattern feature information is an average of all brightness values on a straight line parallel to a vertical axis of the interference pattern image when the interference pattern is in a vertical direction.

13 . The method of claim 11 , wherein
the interference pattern feature information is an average of all brightness values on a straight line parallel to a horizontal axis of the interference pattern image when the interference pattern is in a horizontal direction.

14 . The method of claim 11 , wherein the measuring the coherence of the light source based on the interference pattern feature information includes:
calculating a contrast of the interference pattern feature information; and determining a rotation angle of the interference pattern which maximizes the contrast.

15 . The method of claim 14 , wherein
the contrast is calculated by dividing a difference between a maximum value of the interference pattern feature information and a minimum value of the interference pattern feature information by a sum of the maximum value and the minimum value.

16 . The method of claim 14 , further comprising
analyzing influence of characteristic information of components of the light source on the coherence by using a neural network based on the rotation angle.

17 . The method of claim 16 , wherein
the light source includes a spatial filter and a collimator; and the characteristic information includes at least one of a lens focal distance of the spatial filter, a lens focal distance of the collimator, a size of an aperture of the light source or a pin hole, a diameter of a collimating lens, a diameter of aspheric lens, and a degree of alignment of incident light.

18 . The method of claim 11 , wherein analyzing influence of characteristic information of components of the light source on the coherence by using a neural network based on the rotation angle includes
performing machine learning by using the neural network based on a training set including the characteristic information of the light source mapped to interference pattern feature information having a high contrast.

19 . The method of claim 18 , further comprising:
feeding-back an optimal characteristic value for the light source determined by a result of the machine learning through the neural network.

20 . An apparatus for measuring coherence for holographic display, the apparatus comprising:
a light source configured to output a plane wave having the coherence; a camera configured to photograph an interference pattern by the plane wave; and a processor configured to obtain an interference pattern feature information with respect to the interference pattern from an interference pattern image which is photographed by the camera and measure the coherence of the light source based on the interference pattern feature information.

Assignees

• Electronics & Telecommunications Res Inst

Inventors

• Nam Jeho
• Park Min-Sik
• Shin Seung Hyup

Classifications

• G06N3/04

  Architecture, e.g. interconnection topology · CPC title

• G01B9/02047

  using digital holographic imaging, e.g. lensless phase imaging without hologram in the reference path · CPC title

• G02B5/32

  Holograms used as optical elements · CPC title

• G06N3/08

  Learning methods · CPC title

• G01B9/021 Primary

  using holographic techniques · CPC title