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Digital holography device and image generation method using digital holography

外国特許コード F150008349
整理番号 外0091-1
掲載日 2015年5月20日
出願国 アメリカ合衆国
出願番号 201213980201
公報番号 20130301093
公報番号 9201397
出願日 平成24年2月14日(2012.2.14)
公報発行日 平成25年11月14日(2013.11.14)
公報発行日 平成27年12月1日(2015.12.1)
国際出願番号 JP2012053436
国際公開番号 WO2012114947
国際出願日 平成24年2月14日(2012.2.14)
国際公開日 平成24年8月30日(2012.8.30)
優先権データ
  • 特願2011-040820 (2011.2.25) JP
  • 2012JP053436 (2012.2.14) WO
発明の名称 (英語) Digital holography device and image generation method using digital holography
発明の概要(英語) A digital holography device (1) which is capable of measuring a subject with high accuracy by correcting intensity unevenness by accurately removing zeroth-order diffracted light, includes: a hologram generating section (26) for generating a first hologram and a second hologram each obtained by extracting components identical in phase shift amount from a polarizer array hologram which is recorded in an image capturing device (7) mounted with a polarizer array (6); a dividing section (3) for dividing the first hologram into a plurality of first regions, and dividing the second hologram into a plurality of second regions; a comparing section (4) for comparing a first average value of an intensity in a first region of the first hologram and a second average value of an intensity in a second region of the second hologram which region corresponds to the first region; and a correcting section (5) for, in a case where the first average value and the second average value differ, correcting at least one of the first average value and the second average value so that the first average value and the second average value are equal.
従来技術、競合技術の概要(英語) BACKGROUND ART
A unit of a phase is hereinafter represented by a radian.
As a processing technology becomes elaborated and diversified, sophisticated measurement and analysis of, for example, a three-dimensional shape of an object is required, and various measurement methods have been developed.
Among such measurement methods, an interference measurement technique using light interference, especially digital holography allows non-destructive and non-contact obtainment of three-dimensional information on an object.
Therefore, digital holography is one of the measurement methods which have recently gained attention.
Digital holography is a technique for reconstructing, by use of a computer, an image of a three-dimensional object in accordance with an interference pattern (interference fringe) obtained by light irradiation to the three-dimensional object.
Specifically, for example, an interference pattern formed by an object light beam obtained by light irradiation to a three-dimensional object and a reference light beam coherent to the object light beam is recorded by use of an image capturing device such as a CCD (charge coupled device).
In accordance with the interference pattern thus recorded, an image of the three-dimensional object is reconstructed by calculating diffraction by use of a computer.
Inventors of the present invention have proposed a digital holography device which has a configuration such that a polarizer array is provided, e.g., attached to an image capturing surface of a CCD camera, the polarizer array splitting light emitted from a light source into two kinds of reference light beams having different phases in a plane perpendicular to a direction in which the light travels, and which has improved an image quality of a reconstructed image of a subject by a single shot (see Patent Literature 1).
Further, the inventors of the present invention have proposed a digital holography device which is capable of obtaining highly-accurate three-dimensional information in a deep range at a moment of a single shot by including: a polarized light splitting section which splits an object light beam into two kinds of object light beams that are polarized in different directions, so as to cause a difference in angle between directions in which the two kinds of object light beams are transmitted; and a polarizer array section in which a plurality of first polarizer regions and a plurality of second polarizer regions are provided and which transmits a reference light beam and an object light beam that reaches the polarizer array section via a subject (see Patent Literature 2).

CITATION LIST

Patent Literatures
Patent Literature 1
International Publication No. WO/2009/066771 (Publication Date: May 28, 2009)
Patent Literature 2
International Publication No. WO/2010/092739 (Publication Date: Aug. 19, 2010)
Patent Literature 3
Specification of Japanese Patent No. 4294526

Non Patent Literatures
Non Patent Literature 1
J. W. Goodman and R. W. Lawrence, Appl.
Phys. Lett. 11, p. 77 (1967)
Non Patent Literature 2
I. Yamaguchi and T. Zhang, Opt.
Lett. 22, p. 1268 (1997)

特許請求の範囲(英語) [claim1]
1. A digital holography device comprising: a hologram generating section for generating a first hologram and a second hologram each obtained by extracting components identical in phase shift amount of a reference light beam from a polarizer array hologram which is recorded in a pixel of an image capturing device mounted with a polarizer array and includes two or more kinds of hologram information that differ in the phase shift amount;
a dividing section for dividing the first hologram into a plurality of first regions, and dividing the second hologram into a plurality of second regions in a second pattern identical to a first pattern in which the first hologram is divided into the plurality of first regions;
a comparing section for comparing a first average value of an intensity in a first region of the first hologram and a second average value of an intensity in a second region of the second hologram which region corresponds to the first region; and
a correcting section for, in a case where the first average value and the second average value differ, in order that an intensity of zeroth-order diffracted light is accurately removed, correcting at least one of the intensity in the first region of the first hologram and the intensity in the second region of the second hologram which region corresponds to the first region.
[claim2]
2. The digital holography device as set forth in claim 1, wherein, in a case where the first average value is greater than the second average value, the correcting section corrects the intensity in the first region of the first hologram so that the intensity of zeroth-order diffracted light is accurately removed.
[claim3]
3. The digital holography device as set forth in claim 1, wherein: the dividing section divides a reference light beam into a plurality of reference light beam regions in a third pattern identical to the first pattern in which the first hologram is divided into the plurality of first regions; and
in a case where the first average value is greater than the second average value, the correcting section corrects an intensity in a reference light beam region that corresponds to at least one of the first region and the second region that corresponds to the first region.
[claim4]
4. The digital holography device as set forth in claim 1, wherein the plurality of first regions into which the first hologram is divided by the dividing section are arranged in a matrix pattern.
[claim5]
5. The digital holography device as set forth in claim 1, wherein the plurality of first regions into which the first hologram is divided by the dividing section are arranged in six rows and six columns with respect to a 512- by 512-pixel hologram.
[claim6]
6. An image generation method using digital holography, comprising the steps of: (a) generating a first hologram and a second hologram each obtained by extracting components identical in phase shift amount of a reference light beam from a polarizer array hologram which is recorded in a pixel of an image capturing device mounted with a polarizer array and includes two or more kinds of hologram information that differ in the phase shift amount;
(b) dividing the first hologram into a plurality of first regions, and dividing the second hologram into a plurality of second regions in a second pattern identical to a first pattern in which the first hologram is divided into the plurality of first regions;
(c) comparing a first average value of an intensity in a first region of the first hologram and a second average value of an intensity in a second region of the second hologram which region corresponds to the first region; and
(d) in a case where the first average value and the second average value differ, in order that an intensity of zeroth-order diffracted light is accurately removed, correcting at least one of the intensity in the first region of the first hologram and the intensity in the second region of the second hologram which region corresponds to the first region.
[claim7]
7. A digital holography device comprising: a hologram generating section for generating a first hologram and a second hologram each obtained by extracting components identical in phase shift amount of a reference light beam from a polarizer array hologram which is recorded in a pixel of an image capturing device mounted with a polarizer array and includes two or more kinds of hologram information that differ in the phase shift amount;
a dividing section for dividing the first hologram into a plurality of first regions, and dividing the second hologram into a plurality of second regions in a second pattern identical to a first pattern in which the first hologram is divided into the plurality of first regions;
a reconstructed image group generating section for generating a group of a plurality of reconstructed images by calculation under a phase shift method and diffraction integration in accordance with the first hologram and the second hologram while changing a correction value for an intensity in at least one of a first region of the first hologram and a second region of the second hologram; and
a selecting section for selecting, from the group of the plurality of reconstructed images, a reconstructed image on which least zeroth-order diffracted light is superimposed, and finding the correction value for the reconstructed image thus selected.
[claim8]
8. An image generation method using digital holography, comprising the steps of: (a) generating a first hologram and a second hologram each obtained by extracting components identical in phase shift amount of a reference light beam from a polarizer array hologram which is recorded in a pixel of an image capturing device mounted with a polarizer array and includes two or more kinds of hologram information that differ in the phase shift amount;
(b) dividing the first hologram into a plurality of first regions, and dividing the second hologram into a plurality of second regions in a second pattern identical to a first pattern in which the first hologram is divided into the plurality of first regions;
(c) generating a group of a plurality of reconstructed images by calculation under a phase shift method and diffraction integration in accordance with the first hologram and the second hologram while changing a correction value for an intensity in at least one of a first region of the first hologram and a second region of the second hologram; and
(d) selecting, from the group of the plurality of reconstructed images, a reconstructed image on which least zeroth-order diffracted light is superimposed, and finding the correction value for the reconstructed image thus selected.
  • 発明者/出願人(英語)
  • AWATSUJI YASUHIRO
  • XIA PENG
  • TAHARA TATSUKI
  • KYOTO INSTITUTE OF TECHNOLOGY
国際特許分類(IPC)
米国特許分類/主・副
  • 359/22
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