Interaction of images with strain waves to derive Fourier transform components of the images

• US 4,065,791 A
• Filed: 06/29/1976
• Issued: 12/27/1977
• Est. Priority Date: 12/29/1972
• Status: Expired due to Term

• Current Assignee: Research Corporation
• Original Assignee: Research Corporation
• Inventors: Kowel, Stephen T., Kornreich, Phillipp G.
• Primary Examiner(s): Martin, John C.
• Application Number:
  US05/700,836
• Time in Patent Office: 546 Days
• Field of Search: 358/209, 358/213, 315/55, 315/169 TV, 250/211 J, 250/211 R, 250/20 B, 250/213 R, 310/8.1, 310/8, 310/8.5, 310/9.7
• US Class Current: 348/198
• CPC Class Codes: G02F 1/11 based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves acousto-optical deflection G02F1/33
• CPC Class Codes: G06V 10/12 Details of acquisition arrangements; Constructional details thereof
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 10/42 Global feature extraction by analysis of the whole pattern, e.g. using frequency domain transformations or autocorrelation
• CPC Class Codes: G08B 13/18 Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
• CPC Class Codes: G08B 13/1961 Movement detection not involving frame subtraction, e.g. motion detection on the basis of luminance changes in the image
• CPC Class Codes: G08B 13/19634 Electrical details of the system, e.g. component blocks for carrying out specific functions
• CPC Class Codes: H04N 3/10 by means not exclusively optical-mechanical H04N3/36 takes precedence

Abstract

A system relying on the interaction of images and strain waves uses a technique called pseudo-beam steering to obtain selected components of the two-dimensional Fourier transform of the images. In pseudo-beam steering, two intersecting strain waves are controlled so as to produce the desired effects of a third wave without actually producing such third wave. These desired effects, produced by the interaction of the two intersecting waves, correspond to the effects which would have been produced by a third wave whose direction of travel and whose frequency could be controlled as desired.

Claims

1. A device comprising:

a body of a material and means for forming a light image at a selected image surface of the body;

means for generating at least two acoustic waves propagating along said image surface of the body at intersecting directions and having individually controllable frequency characteristics;

means for deriving electrical signals having frequency characteristics determined by the combination of the frequency characteristics of the two acoustic waves and having electrical parameters representative of the two-dimensional spatial Fourier transform characteristics of the image formed at said image surface of the body;

wherein the body of material comprises an elasto-birefringent substrate having a surface defining said image surface and a first and a second polarizer crossed with respect to each other and flanking the substrate along an optical axis transferse to and intersecting said image surface, and the deriving means comprise means for measuring the light emerging from the combination of the substrate and the polarizers along said optical axis while the acoustic waves propagate along the image surface and while the image is formed at the same surface.

2. A device comprising:

a body of a material and means for forming a light image at a selected image surface of the body;

means for generating at least two acoustic waves propagating along said image surface of the body at intersecting directions and having individually controllable frequency characteristics;

means for deriving electrical signals having frequency characteristics determined by the combination of the frequency characteristics of the two acoustic waves and having electrical parameters representative of the two-dimensional spatial Fourier transform characteristics of the image formed at said image surface of the body;

wherein

the body of material comprises a piezoelectric substrate having an electrophotoconductive film disposed at a surface thereof defining said image surface and acoustically coupled thereto and interdigital contacts disposed on the film in electrical contact therewith;

the deriving means comprise means for measuring the component of the electrical conductivity of the film for frequencies determined by both said first and second frequencies; and

the electrophotoconductive film is divided into a grid of a multiplicity of individual small portions spaced from each other along the image surface.

3. A device comprising:

an elasto-birefringent substrate;

means for directing an optical signal along an optical axis transverse to an image surface of the substrate;

a first and a second polarizer crossed with respect to each other and flanking the substrate along the optical axis;

means for generating a first and a second acoustic wave propagating at intersecting directions along the image surface at respective first and second frequencies; and

means for measuring the intensity of the optical signal emerging from the combination of the substrate and the polarizers along the optical axis to derive electrical signals corresponding to frequencies determined by both the first and the second frequencies and having parameters representative of the two-dimensional spatial Fourier transform characteristics of the image at said image surface of the substrate.

4. A device as in claim 3 including means for varying in a selected manner the first and second frequencies to obtain a selected set of Fourier transform characteristic terms representative of the image.

5. A device comprising:

a substrate;

an electrophotoconductive film disposed on a surface of the substrate and acoustically coupled thereto, said film defining an image surface and being divided into a pattern of individual small film portions interspersed with spaces of other material;

interdigital contacts extending along said image surface and being in electrical contact with the film;

means for generating a first and a second acoustic wave propagating at intersecting directions along said image surface of the substrate at respective first and second frequencies;

means for forming an image on the film; and

means for deriving from the interdigital contacts electrical signals corresponding to frequencies determined by both the first and the second frequencies and having parameters representative of the two-dimensional spatial Fourier transform characteristics of the image formed at the image surface.

6. A device as in claim 5 wherein the substrate is made of a material generating at the film an electrical field of desired characteristics determined by the first and second strain waves propagating therein.