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EP0028548A1 - Optisches Realzeit-Korrelationssystem - Google Patents

Optisches Realzeit-Korrelationssystem Download PDF

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Publication number
EP0028548A1
EP0028548A1 EP80401397A EP80401397A EP0028548A1 EP 0028548 A1 EP0028548 A1 EP 0028548A1 EP 80401397 A EP80401397 A EP 80401397A EP 80401397 A EP80401397 A EP 80401397A EP 0028548 A1 EP0028548 A1 EP 0028548A1
Authority
EP
European Patent Office
Prior art keywords
objects
beams
correlation system
illuminating
photosensitive support
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP80401397A
Other languages
English (en)
French (fr)
Inventor
Jean-Pierre Huignard
Jean-Pierre Herriau
Laurence Pichon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thomson CSF SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0028548A1 publication Critical patent/EP0028548A1/de
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06E—OPTICAL COMPUTING DEVICES; COMPUTING DEVICES USING OTHER RADIATIONS WITH SIMILAR PROPERTIES
    • G06E3/00—Devices not provided for in group G06E1/00, e.g. for processing analogue or hybrid data
    • G06E3/001—Analogue devices in which mathematical operations are carried out with the aid of optical or electro-optical elements
    • G06E3/005—Analogue devices in which mathematical operations are carried out with the aid of optical or electro-optical elements using electro-optical or opto-electronic means

Definitions

  • the invention relates to optical correlation systems making it possible to obtain the function of correlating one image with another.
  • Such systems allow for example to recognize a predetermined graphic in a composite pattern.
  • a known correlation method consists in recording on a photosensitive support a system of interference fringes representing the diffraction pattern provided by a lens which corresponds to two light beams on the path of which are interposed respectively two objects with non-uniform transparency, generally l object to analyze and a reference object.
  • This photosensitive support is read by a reading beam and a characteristic intensity distribution is obtained in the focal plane of a second lens in certain zones of the correlation product between the two objects.
  • the reference object carries a pattern that one seeks to find in the object to be analyzed
  • the image obtained is formed of peaks indicating the presence and the position of the reference pattern in the object to be analyzed.
  • This correlation method has been tested with interference fringe supports of photographic and thermoplastic types.
  • Such supports require a treatment, chemical or thermal, between the recording and reading phases, which implies a delay between the two operations.
  • they are generally not erasable. They therefore do not allow operation in real time.
  • the object of the invention is to use the correlation method described above in real-time applications such as automatic reading, target tracking, machine guidance, etc.
  • the correlation system according to the invention comprises a photosensitive support that is continuously recyclable, that is to say writable without development and erasable at will.
  • Particularly suitable materials are electro-optical materials such as bismuth-silicon oxide, in which spatial variations in light intensity can be converted in real time into spatial variations in refractive index. Registration is done by volume, and not on the surface, the optimal reading conditions are defined by Bragg's law which imposes a value distinct from the reading angle for each spatial frequency recorded. Knowing that the correlation peaks are linked to the recorded spatial frequencies, the invention provides an angular scanning of the read beam making it possible to explore the whole spectrum of the recorded spatial frequencies.
  • FIG. 1 represents a known optical system carrying out the recording trement of the algebraic sum of the Fourier transforms of two two-dimensional functions.
  • the two functions represent the transmittances of the two objects A and B lit by parallel beams FA and FB contiguous or not coming from the same coherent source.
  • Objects A and B are placed on either side of the optical axis z of a lens L 1 of focal distance fl, in the same plane PO perpendicular to this axis.
  • the focal plane PF of the lens L 1 an amplitude distribution proportional to the Fourier transform of the amplitude distribution in the object plane is obtained.
  • a photosensitive support 1 photographic or thermoplastic being placed in the plane PF records the superposition of fringe systems of intensity of different steps, the average step p being equal to where ⁇ 1 is the optical wavelength of the beams FA and F B and ⁇ 0 the half angle between the two beams which interfere.
  • the resulting intensity distribution along x, y axes of the PF plane is proportional to the square of the module of the Fourier transform of the amplitude distribution in the object plane PO.
  • the positions of the objects A and B in this plane are represented in figure 2.
  • the sign X expresses the correlation product.
  • k is the magnification ratio: .
  • FIG. 5 represents an embodiment of the invention. Part of the elements of the correlation device are common with those of Figures 1 and 3 and bear the same references.
  • the interference fringes resulting from the superposition of the beams F A and F B which illuminate the objects A and B, after the focusing effected by the lens L are recorded in a photosensitive plate 10 centered on the focal image plane PF of the lens L 1 and made of an electro-optical material polarized by a field electric obtained by means of a voltage source V. Its orientation is such that the electric field produces a transverse electro-optical effect. Spatial variations in light intensity existing in the PF plane are instantly reflected in the plate by spatial variations in refractive index, the interference planes being almost perpendicular to the direction of the applied electric field.
  • the thickness of the crystal must be equal to or greater than the width of the diffraction zone corresponding to the intersection of the diffraction ellipsoids of the two beams FA and FB whose dimensions depend on the numerical aperture of the lens L 1 .
  • a useful thickness can be defined, which is in any case clearly greater than the wavelength of the two beams so that the recording in the slide can be considered as three-dimensional. It is a superposition of arrays of surfaces.
  • these surfaces can be assimilated to planes perpendicular to the plane of the figure and whose pitch p and inclination f relative to the z axis depend on the angle of the interfering rays, the wavelength ⁇ 1 and the refractive index n of the plate 10.
  • the materials which can be used to form the strip 10 must be both photosensitive and electro-optical.
  • Bismuth-silicon oxide (Bi 12 Si 0 20 ) and bismuth-germanium oxide (Bi 12 Ge 020) are particularly suitable for the invention because they are very sensitive, in the range of wavelengths commonly used (visible and infrared spectrum) and it is known to obtain single crystals of sufficient dimensions (several cm) and having good optical qualities.
  • Other materials could also be suitable but generally do not have as good optical qualities: potassium niobate (KNb0 3 ), KTN, SBN.
  • the invention provides for angular scanning of the reading beam F L.
  • This is supplied by a laser 4 of low power and of wavelength ⁇ 2 chosen outside the range of wavelengths to which the material constituting the lamelO is sensitive.
  • the beam F L is deflected by a conventional acousto-optical or mechanical deflector 5 carrying out the angular scanning in a manner which will be detailed later.
  • the semi strip -transparent L is interposed on the path of the beams FA and F B and must be designed so as to allow these beams to pass. It inevitably introduces a phase shift, which is not annoying since it is identical for the two beams.
  • the orientation relative to the blade 10 of the reading beam, parallel is variable as a function of time and controlled by the deflector 5.
  • n is the refractive index of the plate 10 and d the thickness of the useful diffraction zone in the plate 10.
  • the detection of the correlation peaks is carried out by means 18 such as, for example: mosaic of detectors or vidicon tube connected to a television system.
  • the scanning beam scanning speed is advantageously equal to the television scanning speed.
  • the device was produced with a monocrystalline bismuth-silicon oxide blade of length 2 mm and thickness 1 mm polarized by a voltage V 0 of the order of 2000 V, which provides an electric field of the order of 10 kV / cm 1 , the wavelength of the illumination beams ⁇ , was 0.5 ⁇ m, which corresponds to good sensitivity of the crystal.
  • the focal length of the lens L 1 was: 30 cm and that of the lens L 2 : 10 cm.
  • the magnification k was therefore equal to 0.4.
  • the objects were 2 cm x 2 cm slides.
  • the extent of each zone II and III was thus 0.8 x 0.8 cm, observable with a vidicon tube whose diameter is typically 1.5 cm.
  • a semiconductor laser with a wavelength of 0.8 ⁇ m can also be used.
  • FIG. 5 admits numerous variants, in particular as to the means supplying the beams F A , F B , F L , to the means for detecting the correlation peaks obtained in the plane P and at the respective location of the different elements optical.
  • FIG. 6 represents an alternative embodiment concerning the means supplying the bundles F A and F B. It avoids the use of a lens L 1 with a large aperture. In fact, according to the previous embodiment, the width of the objects being typically 2 or 3 cm and the distance between their centers at least equal to this value, the necessary diameter of the lens L 1 reaches close to 10 cm.
  • the lens L 1 is replaced by two lenses LA and L B , smaller since their dimensions correspond to those of objects A and B, and whose optical axes are merged respectively with the axes of the beams FA and F B which are no longer parallel but each form with respect to the z axis an angle ⁇ ⁇ o, which remains unchanged after the lenses.
  • the beams FA and F B come from a single beam F delivered by a laser 7, argon for example, after widening by a widener 13 and separation and return by mirrors 14, 15, 16, 17.
  • Objects A and B are centered with respect to the respective axes of the two beams.
  • the correlation system is represented in the case of its application to the tracking of targets: Object A is the reference object.
  • Object B has a variable pattern. It consists of an electro-optical modulator controlled by a signal S from, for example, a television camera aiming at the object to be pursued.
  • the correlation system allows the detection of the coincidence between the target landscape and the fixed landscape.
  • the illumination due to this reference beam creates a first variation of index which is not spatially modulated, to which are added the variations due to interference systems due to the illumination beams of objects A and B. additional interference is formed but it can be ensured, by suitably choosing the inclination of the reference beam, that the reflected rays which result therefrom are clearly outside the zones examined, centered around I and J.
  • An exemplary embodiment of system in which a constant level of index modulation is created is shown in FIG. 7.
  • the reference beam FR comes from the same source 7 as the beams F A and F B.
  • a semi-reflecting plate 8 and a mirror 9 make it possible to separate the beam F R.
  • the beams F A F B on the one hand and F R on the other hand are widened by means of wideners 11 and 12.
  • the rest of the system is similar to that of FIG. 5 or of one of the variants thereof. .

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Nonlinear Science (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Holo Graphy (AREA)
  • Optical Recording Or Reproduction (AREA)
EP80401397A 1979-11-05 1980-10-02 Optisches Realzeit-Korrelationssystem Ceased EP0028548A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7927218A FR2468947A1 (fr) 1979-11-05 1979-11-05 Systeme de correlation optique en temps reel
FR7927218 1979-11-05

Publications (1)

Publication Number Publication Date
EP0028548A1 true EP0028548A1 (de) 1981-05-13

Family

ID=9231296

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80401397A Ceased EP0028548A1 (de) 1979-11-05 1980-10-02 Optisches Realzeit-Korrelationssystem

Country Status (4)

Country Link
US (1) US4383734A (de)
EP (1) EP0028548A1 (de)
JP (1) JPS5675618A (de)
FR (1) FR2468947A1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0058592A1 (de) * 1981-02-06 1982-08-25 Thomson-Csf Optische Anordnung zur Fouriertransformation und optischer Korrelator zu deren Anwendung
GB2230125A (en) * 1989-04-06 1990-10-10 British Aerospace Pattern recognition apparatus
WO1997022849A1 (de) * 1995-12-15 1997-06-26 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren und vorrichtung zur hochauflösenden bestimmung von abständen im fokussierten bild eines linsen-pupillen-systems

Families Citing this family (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2518766A1 (fr) * 1981-12-18 1983-06-24 Thomson Csf Dispositif de commutation de faisceaux optiques et central telephonique comprenant un tel dispositif
US4539651A (en) * 1983-02-09 1985-09-03 Ludman Jacques E Optical correlator
US5078501A (en) * 1986-10-17 1992-01-07 E. I. Du Pont De Nemours And Company Method and apparatus for optically evaluating the conformance of unknown objects to predetermined characteristics
US5159474A (en) * 1986-10-17 1992-10-27 E. I. Du Pont De Nemours And Company Transform optical processing system
US4903314A (en) * 1988-05-31 1990-02-20 Grumman Aerospace Corporation Single plate compact optical correlator
JPH0830830B2 (ja) * 1988-09-07 1996-03-27 セイコー電子工業株式会社 光学的相関処理装置
IT1232051B (it) * 1989-03-24 1992-01-23 Cselt Centro Studi Lab Telecom Dispositivo per la correlazione fra fasci ottici
US5107351A (en) * 1990-02-16 1992-04-21 Grumman Aerospace Corporation Image enhanced optical correlator system
US5029220A (en) * 1990-07-31 1991-07-02 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Optical joint correlator for real-time image tracking and retinal surgery
US5276636A (en) * 1992-09-14 1994-01-04 Cohn Robert W Method and apparatus for adaptive real-time optical correlation using phase-only spatial light modulators and interferometric detection
IL110771A (en) * 1994-08-25 1998-02-08 Holon Holon Hanni A priori and adaptive filtering for detection of signals corrupted by noise
US5900620A (en) * 1997-08-27 1999-05-04 Trw Inc. Magic mirror hot spot tracker
FR2755516B1 (fr) 1996-11-05 1999-01-22 Thomson Csf Dispositif compact d'illumination
FR2819061B1 (fr) * 2000-12-28 2003-04-11 Thomson Csf Dispositif de controle de polarisation dans une liaison optique
FR2860291B1 (fr) * 2003-09-26 2005-11-18 Thales Sa Dispositif capteur de vitesse de rotation interferometrique a fibre optique
US10337851B2 (en) * 2015-04-02 2019-07-02 Ramot At Tel-Aviv University Ltd. Fast phase processing of off-axis interferograms

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2362466A1 (fr) * 1976-08-19 1978-03-17 Thomson Csf Cellule d'enregistrement holographique, memoire et dispositif de calcul optique utilisant une telle cellule

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3519992A (en) * 1966-08-10 1970-07-07 North American Rockwell Photointerpretation system
US3544197A (en) * 1967-03-23 1970-12-01 Research Corp Optical crosscorrelation
US3761154A (en) * 1971-12-27 1973-09-25 Bendix Corp Display device generating many superimposed output signals to provide an image
US3812496A (en) * 1972-08-22 1974-05-21 Trw Inc Optical signal recording system
US4174179A (en) * 1977-08-24 1979-11-13 Guy Indebetouw Continuous feed holographic correlator for randomly oriented workpieces

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2362466A1 (fr) * 1976-08-19 1978-03-17 Thomson Csf Cellule d'enregistrement holographique, memoire et dispositif de calcul optique utilisant une telle cellule

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
APPLIED OPTICS, Vol. 14, No. 11, novembre 1975, New York, US, NISENSON et SPRAGLIE: "Real-time optical correlation", pages 2602-2606 *
APPLIED OPTICS, Vol. 9, Juillet 1970, New York, US, WEAVER et al.: "The Optical Convolution of Time Functions", pages 1672-1688 *
OPTICS LETTERS, Vol. 4, No. 4, avril 1979, New York, US, LEE et al.: Dual-axis joint-Fourier-transform correlator", pages 121-123 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0058592A1 (de) * 1981-02-06 1982-08-25 Thomson-Csf Optische Anordnung zur Fouriertransformation und optischer Korrelator zu deren Anwendung
GB2230125A (en) * 1989-04-06 1990-10-10 British Aerospace Pattern recognition apparatus
WO1997022849A1 (de) * 1995-12-15 1997-06-26 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren und vorrichtung zur hochauflösenden bestimmung von abständen im fokussierten bild eines linsen-pupillen-systems

Also Published As

Publication number Publication date
JPS5675618A (en) 1981-06-22
FR2468947A1 (fr) 1981-05-08
US4383734A (en) 1983-05-17

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Inventor name: HUIGNARD, JEAN-PIERRE

Inventor name: HERRIAU, JEAN-PIERRE

Inventor name: PICHON, LAURENCE