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Interference measurement apparatus and method for measuring interference

Foreign code F120007028
Posted date Nov 19, 2012
Country United States of America
Application number 201013138408
Gazette No. 20110292402
Gazette No. 8654343
Date of filing Jan 13, 2010
Gazette Date Dec 1, 2011
Gazette Date Feb 18, 2014
International application number JP2010000132
International publication number WO2010092739
Date of international filing Jan 13, 2010
Date of international publication Aug 19, 2010
Priority data
  • P2009-031449 (Feb 13, 2009) JP
  • 2010WO-JP00132 (Jan 13, 2010) WO
Title Interference measurement apparatus and method for measuring interference
Abstract (US8654343)
An embodiment of the present invention realizes an interference measurement apparatus which can obtain an interference image to be used for obtaining three-dimensional information of a subject which dynamically changes.
An interference measurement apparatus of the present invention, which captures an interference image formed by the reference light beam and the object light beam which has reached the image-capturing element via a subject, the interference measurement apparatus includes: a laser light source; a beam splitter which splits a laser beam into a reference light beam and an object light beam; and an image-capturing element; a polarization splitting section which splits the object light beam into two types of object light beams which are different in polarization direction so that an angular difference is caused between respective propagation directions of the two types of object light beams; and a polarizer array device which allows (i) the reference light beam and (ii) the two types of object light beams which have reached the polarizer array device via the subject to pass through the polarizer array device (30), the polarizer array device in which a plurality of first polarizer regions and a plurality of second polarizer regions are arranged, and each of the plurality of first polarizer regions and each of the plurality of second polarizer regions respectively allowing light components which are different in polarization direction.
This makes it possible to obtain, by one-time image capturing, a plurality of interference patterns required for phase unwrapping.
Scope of claims [claim1]
1. An interference measurement apparatus comprising: at least one light source which generates coherent light;
a light splitting section which splits, into a reference light beam and an object light beam, the coherent light emitted from the at least one light source;
an image-capturing section which captures an interference image formed by the reference light beam and the object light beam which has reached the image-capturing section via a subject;
a polarization splitting section which splits, into two types of object light beams, a first object light beam polarized in a first direction and a second object light beam polarized in a second direction which is different from the first direction, the object light beam emitted from the light splitting section, so that an angular difference is caused between respective propagation directions of the two types of object light beams; and
a polarizer array section which allows (i) the reference light beam and (ii) the two types of object light beams which have reached the polarizer array section via the subject to pass through the polarizer array section, the polarizer array section in which a plurality of first polarizer regions and a plurality of second polarizer regions are arranged, the plurality of first polarizer regions having their transmission axes in the first direction and the plurality of second polarizer regions having their transmission axes in the second direction,
wherein the image-capturing section which captured the interference image contains (I) a first interference pattern of interference between the first object light beam and a light component of the reference light beam which light component is polarized in the first direction and (II) a second interference pattern of interference between the second object light beam and a light component of the reference light beam which light component is polarized in the second direction,
wherein the reference light beam passes through a path to go around the polarization splitting section and the subject.
[claim2]
2. An interference measurement apparatus as set forth in claim 1, further comprising a phase-shifting array section which allows the reference light beam to pass through the phase-shifting array section, the phase-shifting array section in which a plurality of first phase-shifting regions and a plurality of second phase-shifting regions are arranged, the phase-shifting array section causing a difference in phase between a portion of the reference light beam which portion has passed through the plurality of first phase-shifting regions and a portion of the reference light beam which portion has passed through the plurality of second phase-shifting regions.
[claim3]
3. An interference measurement apparatus as set forth in claim 1, further comprising, between the subject and the image-capturing section, an optical path length-shifting array section which allows the reference light beam and the two types of object light beams to pass through the optical path length-shifting array section, the optical path length-shifting array section in which a plurality of first optical path length-shifting regions and a plurality of second optical path length-shifting regions are arranged, the optical path length-shifting array section causing a difference in phase between a portion of the reference light beam which portion has passed through the plurality of first optical path length-shifting regions and a portion of the reference light beam which portion has passed through the plurality of second optical path length-shifting regions, and
the optical path length-shifting array section causing a difference in phase between (i) respective portions of the two types of object light beams which portions have passed through the plurality of first optical path length-shifting regions and (ii) respective portions of the two types of object light beams which portions have passed through the plurality of second optical path length-shifting regions.
[claim4]
4. An interference measurement apparatus as set forth in claim 1, further comprising a wavelength-selecting filter, the at least one light source being a plurality of light sources,
the plurality of light sources respectively generating coherent lights which are different in wavelength,
the wavelength-selecting filter having a plurality of wavelength-selecting regions which are different in wavelength at which light is passed through the plurality of wavelength-selecting regions,
the wavelength-selecting filter selectively allowing the reference beam light and the two types of object light beams to pass through the wavelength-selecting filter, in accordance with respective wavelengths of the plurality of wavelength-selecting regions.
[claim5]
5. An interference measurement apparatus as set forth in claim 4, further comprising a reproducer section which extracts, from the interference image, pixels corresponding to the first interference pattern and pixels corresponding to the second interference pattern so as to generate a reconstructed image of the subject, the reproducer section including:
a reproduction processing section which finds, with respect to each of a plurality of wavelengths, a reconstructed image of the subject on the basis of the interference image;
a phase unwrapping processing section which carries out, on the basis of the interference image, phase unwrapping with respect to each of the plurality of wavelengths so as to find a height distribution of the subject; and
an extraction processing section which compares representative intensities of wavelengths of reproduced light in a predetermined region which covers a target pixel in pixels which form the reconstructed image, so as to extract, as a height distribution of the target pixel, a height distribution of a wavelength at which the reproduced light has a highest intensity.
[claim6]
6. An interference measurement apparatus as set forth in claim 1, further comprising a reproducer section which extracts, from the interference image, pixels corresponding to the first interference pattern and pixels corresponding to the second interference pattern so as to generate a reconstructed image of the subject, the reproducer section finding a height distribution of the subject.
[claim7]
7. An interference measurement apparatus as set forth in claim 1, further comprising: a size measuring device configured to measure a size of the subject along a depth direction as viewed from the image-capturing section;
an angular difference adjusting device configured to alter on the basis of the instruction from the control section, the angular difference between the two types of object light beams split by the polarization splitting section; and
a control device,
wherein the control device (i) determining, on the basis of the size thus measured by the size measuring device, a range in which phase unwrapping can be carried out, and (ii) giving an instruction to the angular difference adjusting device in accordance with the range thus determined.
[claim8]
8. An interference measurement method comprising: splitting coherent light into a reference light beam and an object light beam;
splitting the object light beam into two types of object light beams, a first object light beam polarized in a first direction and a second object light beam polarized in a second direction which is different from the first direction so that an angular difference is caused between respective propagation directions of the two types of object light beams;
passing, through a plurality of first polarizer regions having their transmission axes in the first direction and a plurality of second polarizer regions having their transmission axes in the second direction, the reference light beam and the two types of object light beams which have reached the polarizer array section via a subject to pass through, so that light components which are different in polarization direction pass through the plurality of first polarizer regions and the plurality of second polarizer regions; and
capturing an interference image containing (I) a first interference pattern of interference between the first object light beam and a light component of the reference light beam which light component is polarized in the first direction and (II) a second interference pattern of interference between the second object light beam and a light component of the reference light beam which light component is polarized in the second direction,
wherein the reference light beam passes through a path to go around the polarization splitting section and the subject.
  • Inventor, and Inventor/Applicant
  • AWATSUJI YASUHIRO
  • TAHARA TATSUKI
  • KYOTO INSTITUTE OF TECHNOLOGY
IPC(International Patent Classification)
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