Optical information processing apparatus and method for using computer generated hologram

• US 5,497,433 A
• Filed: 05/12/1995
• Issued: 03/05/1996
• Est. Priority Date: 06/05/1990
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Itoh, Masami, Fukui, Atsushi, Kawamura, Hiroyuki, Nishii, Kanji
• Primary Examiner(s): Mancuso, Joseph
• Assistant Examiner(s): DEL ROSSO, GERARD DOMNICK
• Application Number:
  US08/440,236
• Time in Patent Office: 298 Days
• Field of Search: 382/209, 382/210, 382/211, 382/216, 382/217, 382/218, 359/29, 359/559, 359/561, 364/822, 364/515
• US Class Current: 382/211
• CPC Class Codes: G03H 1/08 Synthesising holograms, i.e. holograms synthesized from objects or objects from hologramsusing electric digital computers G06F; G06T
• CPC Class Codes: G06V 10/895 the filter being related to phase processing, e.g. phase-only filters

Abstract

An input image of an object is optically Fourier-transformed and after coordinate-transforming the Fourier-transformed input image optically to obtain a rotation-invariant and scale-invariant image, the resultant image is pattern-matched with a computer generated hologram of a reference image. The coordinate-transformation of the Fourier-transformed input image is made using an optical phase filter represented as a computer generated hologram.

Claims

1. An optical information processing apparatus comprising:

an input means for inputting an image of an object;

a first spatial light modulator for displaying an input image;

a light source for irradiating said first light modulator;

a first lens means arranged so as for its front focal plane to coincide with the plane on which said first spatial light modulator is arranged, said first lens means Fourier-transforming the input image displayed on said first spatial light modulator and irradiated by said light source;

a first memory means for storing a coordinate transforming computer generated hologram for performing a rotation-invariant and scale-invariant coordinate transform;

a second spatial light modulator arranged on the rear focal plane of said first lens for superposing the image Fourier-transformed by said first hens means with said coordinate transforming computer generated hologram having been stored in said first memory;

a second lens means arranged so as for its front focal plane to coincide with the rear focal plane of said first lens means, said second lens means Fourier-transforming the superposed image, thereby obtaining a rotation-invariant and scale-invariant Fourier-transformed image;

a third lens means arranged so as for its front focal plane to coincide with the rear focal plane of said second lens means, said third lens means Fourier-transforming the image Fourier-transformed by said second lens means;

a second memory for storing computer generated holograms of reference images each obtained by Fourier-transforming a reference image, rotation-invariant and scale-invariant coordinate transforming the Fourier-transformed reference image, calculating an absolute value of the coordinate-transformed image, and Fourier-transforming the absolute value;

a third spatial light modulator arranged on the rear focal plane of said third lens means for superposing the image Fourier-transformed by said third lens means and a complex conjugate of a computer generated hologram having been stored in said second memory;

a fourth lens means arranged so as for its front focal plane to coincide with the plane of said third spatial light modulator, said fourth lens means Fourier-transforming an image obtained by superposing the image Fourier-transformed by said third lens means to said computer generated hologram displayed on said third spatial light modulator; and

a photo detecting means arranged on the rear focal plane of said fourth lens means which receives the image Fourier-transformed by said fourth lens means to detect whether or not the input image coincides with the reference image.

2. The optical information processing apparatus as claimed in claim 1, wherein each of said first to third spatial light modulators is comprised of a liquid crystal display.

3. An optical information processing apparatus comprising:

an input means for inputting an image of an object;

a first spatial light modulator for displaying an input image;

a light source for irradiating said first light modulator;

a first lens means arranged so as for its front focal plane to coincide with the plane on which said first spatial light modulator is arranged, said first lens means Fourier-transforming the input image displayed on said first spatial light modulator and irradiated by said light source;

a memory means for storing a coordinate transforming computer generated hologram and a plurality of computer generated holograms of reference images, said coordinate transforming computer generated hologram for performing a rotation-invariant and scale-invariant coordinate transform and each of said plurality of computer generated holograms of reference images being obtained by Fourier-transforming a reference image, rotation-invariant and scale-invariant coordinate transforming the Fourier-transformed reference image, calculating a square of an absolute value of the coordinate-transformed image, Fourier-transforming the square of an absolute value of the coordinate-transformed image;

a second spatial light modulator arranged on the rear focal plane of said first lens means for selectively displaying said coordinate transforming computer generated hologram and a complex conjugate of one of said plurality of computer generated holograms of reference images;

a second lens means arranged so as for its front focal plane to coincide with the rear focal plane of said first lens means, said second lens means Fourier-transforming the image superposed on said second spatial light modulator;

a photoelectric transforming device arranged on the rear focal plane of said second lens means, which detects an intensity distribution of the image Fourier-transformed by said second lens means; and

a signal transforming means for transforming an output signal of said photoelectric transforming device and inputting the transformed signal to said first spatial light modulator to display the intensity distribution detected by said photoelectric transforming device thereon, wherein the input image of an object displayed on said first spatial light modulator and Fourier-transformed by said first lens means is superposed with said coordinate transforming computer-generated hologram stored in said memory means on said second spatial light modulator, thereby being transformed to a rotation-invariant and scale-invariant image, an intensity distribution of the rotation-invariant and scale-invariant image, after being Fourier-transformed by said second lens means, is detected by said photoelectric transforming device, the detected intensity distribution is displayed on said first spatial light modulator via said signal transforming means and, after being Fourier-transformed by said first lens means, is superposed with said complex conjugate of one of computer-generated holograms of reference images stored in said memory meads on said second spatial light modulator, the superposed image, after being Fourier-transformed by said second lens means, is detected by said photoelectric transforming device, thereby obtaining a result of pattern matching between the input image of an object and the reference pattern.

4. The optical information processing apparatus as claimed in claim 3, wherein each of said first and second spatial light modulators is comprised of a liquid crystal display.

5. An optical information processing apparatus comprising:

an input means for inputting an image of an object;

a first spatial light modulator for displaying an input image;

a light source for irradiating said first light modulator;

a first lens means arranged so as for its front focal plane to coincide with the plane on which said first spatial light modulator is arranged, said first lens means Fourier-transforming the input image displayed on said first spatial light modulator and irradiated by said light source;

a second spatial light modulator of a light writing type arranged on the rear focal plane of said first lens means on one side of which the image Fourier-transformed by said first lens means is written;

a memory means for storing a coordinate transforming computer generated hologram and a plurality of computer generated holograms of reference images, said coordinate transforming computer generated hologram being for performing a rotation-invariant and scale-invariant coordinate transform and each of said plurality of computer generated holograms of reference images being obtained by Fourier-transforming a reference image, rotation-invariant and scale-invariant coordinate transforming the Fourier-transformed reference image, calculating a square of an absolute value of the coordinate-transformed image, Fourier-transforming the square of an absolute value of the coordinate-transformed image;

a third spatial light modulator for selectively displaying the coordinate transforming computer generated hologram and said plurality of computer generated holograms having been stored in said memory;

a second lens means for projecting a condensed image of an image displayed on the other side of said second spatial light modulator, thereby superposing the Fourier-transformed input image and the image displayed on said third spatial light modulator;

a third lens means arranged so as for its front focal plane to coincide with the rear focal plane of said first lens means, said third lens means Fourier-transforming the image superposed on said second spatial modulator;

a photoelectric transforming device arranged on the rear focal plane of said second lens means, which detects an intensity distribution of the image Fourier-transformed by said third lens means; and

a signal transforming means for transforming an output signal of said photoelectric transforming device and inputting the transformed signal to said first spatial light modulator to display the intensity distribution detected by said photoelectric transforming device thereon, wherein the intensity distribution displayed on said first spatial light modulator is Fourier-transformed by said first lens means, the Fourier-transformed intensity distribution is superposed with said one of plurality of computer generated holograms on said second spatial light modulator, the superposed image is Fourier-transformed by said third lens means and the Fourier-transformed superposed image is detected by said photoelectric transforming device.

6. The optical information processing apparatus as claimed in claim 5, wherein each of said first to third spatial light modulators is comprised of a liquid crystal display.

7. An optical information processing apparatus comprising:

an input means for inputting an image of an object;

a first spatial light modulator for displaying an input image;

a light source for irradiating said first light modulator;

a first lens means arranged so as for its front focal plane to coincide with the plane on which said first spatial light modulator is arranged, said first lens means Fourier-transforming the input image displayed on said first spatial light modulator and irradiated by said light source;

a memory means for storing a plurality of computer generated holograms related to reference images to be compared with an input image, each of said plurality of computer generated holograms being obtained by Fourier-transforming a reference image, rotation-invariant and scale-invariant coordinate transforming the Fourier-transformed reference image, calculating an absolute value of the coordinate-transformed image, Fourier-transforming the absolute value, taking a complex conjugate of the Fourier-transformed absolute value, inverting polarities of spatial frequencies with respect to the complex conjugate, and superposing phase information for rotation-invariant and scale-invariant transforming to the inverted complex conjugate;

a second spatial light modulator arranged on the rear focal plane of said first lens which optically superposes the Fourier-transformed input image and one of said plurality of computer generated holograms having been stored in said memory;

a second lens means arranged so as for its focal plane to coincide with the rear focal plane of said first lens means, said second lens means Fourier-transforming the image superposed on said second spatial light modulator; and

a photo detecting means arranged on the rear focal plane of said fourth lens means, which detects an intensity distribution of the image Fourier-transformed by said second lens means.

8. The optical information processing apparatus as claimed in claim 7, wherein each of said first and second spatial light modulators is comprised of a liquid crystal display.

9. An optical information processing apparatus comprising:

an input means for inputting an image of an object;

a first spatial light modulator for displaying an input image;

a light source for irradiating said first light modulator;

a first lens means arranged so as for its front focal plane to coincide with the plane on which said first spatial light modulator is arranged, said first lens means Fourier-transforming the input image displayed on said first spatial light modulator and irradiated by said light source;

a second spatial light modulator of a light writing type arranged on the rear focal plane of said first lens means on one side of which the image Fourier-transformed by said first lens means is written;

a memory means for storing a plurality of computer generated holograms related to reference images to be compared with an input image, each of said plurality of computer generated holograms being obtained by Fourier-transforming a reference image, rotation-invariant and scale-invariant coordinate transforming the Fourier-transformed reference image calculating an absolute value of the coordinate-transformed image, Fourier-transforming the absolute value, taking a complex conjugate of the Fourier-transformed absolute value, inverting polarities of spatial frequencies with respect to the complex conjugate, and superposing phase information for rotation-invariant and scale-invariant transforming to the inverted complex conjugate;

a third spatial light modulator for displaying one of said plurality of computer generated holograms having been stored in said memory, thereby superposing the Fourier-transformed input image and one of said plurality of computer generated holograms on said second spatial modulator;

a second lens means for projecting a condensed image of an image displayed on said third spatial light modulator onto the other side of said second spatial light modulator;

a third lens means arranged so as for its focal plane to coincide with the plane on which said second spatial modulator is arranged for Fourier-transforming the image superposed on said second spatial modulator; and

a photoelectric transforming device arranged on the rear focal plane of said third lens means, which detects an intensity distribution of the image Fourier-transformed by said third lens means.

10. The optical information processing apparatus as claimed in claim 9, wherein each of said first to third spatial light modulators is comprised of a liquid crystal display.