Holographic operating optical apparatus

• US 5,132,811 A
• Filed: 06/28/1990
• Issued: 07/21/1992
• Est. Priority Date: 08/10/1989
• Status: Expired due to Term

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Yamamoto, Shuhei, Mitsuoka, Yasuyuki, Iwaki, Tadao
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Lerner, Martin
• Application Number:
  US07/545,913
• Time in Patent Office: 754 Days
• Field of Search: 350/3.64, 350/342, 350/162.12, 350/162.13, 359/6, 359/7, 359/72, 359/561
• US Class Current: 359/6
• CPC Class Codes: G03H 1/16 using Fourier transform G03H1/10, G03H1/12, G03H1/14 take precedence; analogue computers G06G, e.g. G06G7/19
• CPC Class Codes: G03H 1/22 Processes or apparatus for obtaining an optical image from holograms G03H1/26 - G03H1/34 take precedence
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2001/0088 for video-holography, i.e. integrating hologram acquisition, transmission and display
• CPC Class Codes: G03H 2222/56 Conjugated beam
• CPC Class Codes: G03H 2225/25 Optically addressed SLM [OA-SLM]
• CPC Class Codes: G03H 2226/11 Electro-optic recording means, e.g. CCD, pyroelectric sensors
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means
• CPC Class Codes: H04Q 2011/002 using optical delay lines or optical buffers or optical recirculation
• CPC Class Codes: H04Q 2011/0035 using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical

Abstract

A holographic apparatus has an inferometer for concurrently irradiating an image recording medium by a writing reference light of spherical or plane wave form and a signal light containing image information which interfere with each other to form a hologram, and means for irradiating the hologram by a reading reference light in the opposite direction of the reference light to thereby reconstruct the image information. The image recording medium is comprised of a photoconductive layer, an optical reflective layer, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristic between its optical reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates. The interferometer is preferably of the Mach-Zehnder type which includes along its signal light forming path an optical shutter, means for entering image information and an imagery optical system for optionally optically Fourier transforming the input image information and then enlarging the same to form the image on an otpical writing face of the light addressed liquid crystal light valve. By such construction, an extremely small holographic apparatus can be obtained to record and read the hologram in real time.

Claims

1. A holographic apparatus comprising:

an interferometer for irradiating an image recording medium concurrently with a reference light having a spherical wave or plane wave form and a signal light containing image information so that the reference light and the signal light interfere with each other to form thereon a hologram; and

means for irradiating the hologram by a reading light in the opposite direction of the reference light to reconstruct the image information;

wherein the image recording medium comprises a light addressed liquid crystal light valve composed of a photoconductive layer, an optical reflective layer, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its optical reflectivity and an applied voltage, means for applying the voltage, and a pair of transparent substrates.

2. A holographic apparatus according to claim 1, wherein the interferometer includes a means disposed in a signal-light-forming optical path for entering the image information, and an imagery optical means for optically Fourier transforming the input image information and then enlarging the Fourier transformed image information to effect image formation on an optical writing face of the light addressed liquid crystal light valve.

3. A holographic apparatus according to claim 1, wherein the interferometer comprises a Mach-Zehnder or Michelson interferometer.

4. An optical interconnection apparatus for recording interference fringes causes between coherent signal input light and reference light on a hologram recording medium to form a hologram and for selectively reconstructing an output light from the hologram to effect optical interconnection between the input and output lights, comprising:

an optical system for generating signal input lights and having optical shutters for controlling the transmission of light for generating more than one signal input light; and

a hologram recording medium comprising a light addressed liquid crystal light valve composed of a photoconductive layer, an optical reflective layer, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its reflectivity and an applied voltage, means for applying the voltage, and a pair of transparent substrates.

5. An optical correlation apparatus for effecting optical correlation processing of two-dimensional images using coherent light so as to automatically carry out recognition and measurement of a given pattern, comprising:

means for converting at least one code image and at least one input image into a corresponding coherent code image and a corresponding coherent input image;

means for independently Fourier transforming the coherent code image and the coherent input image into a Fourier code image and a Fourier input image;

means for enabling a coherent reference light of spherical wave or plane wave form to interfere with the Fourier code image to form a Fourier code hologram;

means including a binary spatial light modulator for converting the Fourier code hologram into a binarized intensity hologram image and recording the same;

means for reading the binarized intensity hologram recorded on the binary spatial light modulator using the Fourier input image; and

means for Fourier transforming the read binarized intensity hologram into a correlation image and for converting the correlation image into a corresponding output signal.

6. An optical correlation apparatus according to claim 5, wherein the binary spatial light modulator comprises a light addressed liquid crystal light valve composed of a photoconductive layer, an optical reflection layer, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics of its reflectivity in response to an applied voltage, means for applying the voltage and a pair of transparent substrates.

7. A method of driving an optical correlator having means for converting at least one code image and at least one input image into a corresponding coherent code image and a corresponding coherent input image, means for Fourier transforming the coherent code image and the coherent input image independently of each other into a Fourier code image and a Fourier input image, means for enabling a coherent reference light having a spherical wave or plane wave form to interfere with the Fourier code image to form Fourier holographic fringes, a light addressed ferroelectric liquid crystal light valve for binarizing the Fourier holographic fringes and recording them in the form of a binarized intensity hologram, wherein the light valve comprises a hydrogenated amorphous silicon photoconductive layer, an optical reflection layer having a given transmittance, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates, means for reading the binarized intensity hologram recorded on the light addressed ferroelectric liquid crystal light valve using a reading light from the Fourier input image, and means for Fourier transforming the read binarized intensity hologram into a correlation image and for photoelectrically converting the correlation image into a corresponding output signal, the method comprising the steps of:

continuously irradiating the light addressed ferroelectric liquid crystal light valve with a writing light to form the Fourier holographic fringes;

continuously irradiating the light addressed ferroelectric liquid crystal light valve with the reading light to form the Fourier input image;

continuously applying to the light addressed ferroelectric liquid crystal light valve a pulse voltage having a voltage polarity relative to the hydrogenated amorphous silicon photoconductive layer which is sequentially and cyclically changed between positive, negative and zero voltages, whereby erasing of the image is carried out when the positive voltage is applied, writing of the image is carried out when the negative voltage is applied and reading of the image is carried out when either the negative voltage or zero voltage is applied; and

controlling the pulse voltage to adjust its amplitude, frequency and pulse width when the positive, negative and zero voltages are applied so as to regulate an intensity of the correlation image.

8. A method of driving a holography apparatus of a Fourier transform type having means for converting at least one input image into a corresponding coherent input image, means for Fourier transforming the coherent input image into a Fourier input image, means for enabling a coherent reference light having a spherical wave or plane wave form to interfere with the Fourier input image to form Fourier holographic fringes, a light addressed ferroelectric liquid crystal light valve for binarizing the Fourier holographic fringes and recording them in the form of a binarized intensity hologram, the light valve being composed of a hydrogenated amorphous silicon photoconductive layer, an optical reflection layer having a given transmittance, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates, means for reading the binarized intensity hologram recorded on the light addressed ferroelectric liquid crystal light valve using a coherent reading light having spherical wave or plane wave form, and means for Fourier transforming the read binarized intensity hologram image into a reconstructed image and for photoelectrically converting the reconstructed image into a corresponding output signal, the method comprising the steps of:

continuously irradiating the light addressed ferroelectric liquid crystal light valve with a writing light which forms the Fourier holographic fringes and with the coherent reading light of spherical or plane wave form;

continuously applying to the light addressed ferroelectric liquid crystal light valve a pulse voltage having a voltage polarity relative to the hydrogenated amorphous silicon photoconductive layer which is sequentially and cyclically changed between positive, negative and zero voltages, whereby erasing of the image is carried out when the positive voltage is applied, writing of the image is carried out when the negative voltage is applied and reading of the image is carried out when either the negative voltage or the zero voltage is applied; and

controlling the pulse voltage to adjust its amplitude, frequency and pulse width when the positive, negative and zero voltages are applied so as to regulate an intensity or quality of the reconstructed image.

9. A method of driving a holographic apparatus having means for converting at least one input image into a corresponding coherent input image, means for enabling a coherent reference light having a spherical wave or plane wave form to interfere with the coherent input image to form holographic fringes, a light addressed ferroelectric liquid crystal light valve for binarizing the holographic fringes and recording them in the form of a binarized intensity hologram, the light valve being composed of a hydrogenated amorphous silicon photoconductive layer, an optical reflection layer having a give transmittance rate, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates, means for reading the binarized intensity hologram recorded on the light addressed ferroelectric liquid crystal light valve using a coherent reading light of spherical or plane wave form, and means for converting the read binarized intensity hologram into a corresponding output signal, the method comprising the steps of:

continuously irradiating the light addressed ferroelectric liquid crystal light valve with a writing light to form the holographic fringes;

continuously irradiating the light addressed ferroelectric liquid crystal light valve with the coherent reading light of spherical or plane wave form;

continuously applying to the light addressed ferroelectric liquid crystal light valve a pulse voltage having a voltage polarity relative to the hydrogenated amorphous silicon photoconductive layer which is sequentially and cyclically changed between positive, negative and zero voltages, whereby erasing of the image is carried out when the positive voltage is applied, writing of the image is carried out when the negative voltage is applied and reading of the image is carried out when the negative voltage or zero voltage is applied; and

controlling the pulse voltage to adjust its amplitude, frequency and pulse width when the positive, negative and zero voltages are applied so as to regulate an intensity or quality of the image.