METHOD AND SYSTEM FOR ACOUSTO-ELECTRIC SCANNING

• US 3,826,866 A
• Filed: 04/16/1973
• Issued: 07/30/1974
• Est. Priority Date: 04/16/1973
• Status: Expired due to Term

• Current Assignee: Calvin F. Quate, Nicolas J. Moll, Oberdan W. Otto
• Original Assignee: Calvin F. Quate, Nicolas J. Moll, Oberdan W. Otto
• Inventors: Quate, Calvin F., Otto, Oberdan W., Moll, Nicolas J.
• Primary Examiner(s): Murray, Richard
• Application Number:
  US05/351,237
• Time in Patent Office: 470 Days
• Field of Search: 178/7.1,7.6
• US Class Current: 348/198
• CPC Class Codes: G10K 11/36 Devices for manipulating acoustic surface waves electro-acoustic amplifiers H03F13/00; networks comprising electro-acoustic elements H03H9/00
• CPC Class Codes: H04N 3/10 by means not exclusively optical-mechanical H04N3/36 takes precedence

Abstract

A method and system for scanning an energetic image to convert the information in the energetic image into an electrical signal. A semiconductor has an electrical field applied thereto to increase the average depletion layer width of the semiconductor by charging the semiconductor surface states. The energetic image is impinged upon the semiconductor and begins discharging the surface states in accordance with intensity variations in the image to produce depletion layer with variations. A piezoelectric substrate is situated adjacent to the semiconductor. A reading acoustic surface wave is propagated along the piezoelectric substrate along one dimension of the semiconductor. The amplitude of the reading wave is modulated by the depletion layer width perturbations of the semiconductor so that an output acoustic wave is formed. The output acoustic wave is converted to an electrical signal having amplitude variations corresponding to the depletion layer width perturbations of the semiconductor. In accordance with one embodiment of the invention two dimensional scanning of the semiconductor is achieved through propagating a plurality of reading acoustic surface waves differing in frequency from each other and spaced from each other along a second dimension of the semiconductor film.

Claims

1. A method of scanning an energetic image to convert the information present therein into an electrical signal comprising the steps of charging the surface states of a semiconductor to produce a relatively uniform depletion layer along the semiconductor, impinging the energetic image on the semiconductor whereby perturbations are produced in the depletion layer as the surface states begin to discharge at a rate dependent upon the intensity of the energetic image, propagating a reading acoustic wave in the vicinity of the semiconductor in one direction past the semiconductor with the depletion layer width perturbations producing corresponding propagation coefficient perturbations of the reading acoustic wave to form an output acoustic wave which is modulated in accordance with the depletion layer width perturbations in the semiconductor, and converting the output acoustic wave into an electrical signal.

2. A method in accordance with claim 1 in which the semiconductor surface states are charged by application of an electrical field across the semiconductor.

3. A method in accordance with claim 2 in which the electric field is simultaneously applied along the extent of the semiconductor.

4. A method in accordance with claim 3 in which a single polarity electrical field is applied along the extent of the semiconductor and then removed so that the surface states can then begin to discharge in accordance with the intensity of the energetic image.

5. A method in accordance with claim 3 in which an alternating polarity electrical field is applied along the extent of the semiconductor and then removed so that the surface states can then begin to discharge in accordance with the intensity of the energetic image.

6. A method in accordance with claim 1 wherein the step of charging the surface states of the semiconductor comprises propagating a scanning acoustic wave pulse in a second direction past the semiconductor opposite the one direction whereby the electric field associated with the scanning acoustic wave pulse sequentially charges the surface states along the extent of the semiconductor.

7. A method in accordance with claim 1 including the steps of generating a plurality of reading acoustic waves, said plurality of reading acoustic waves being propagated past the semiconductor parallel to each other along the extent of the semiconductor in one dimension but being spaced from each other along a second dimension of the semiconductor to form a plurality of modulated output acoustic waves, and converting the plurality of output acoustic waves into electrical signals whereby a two dimensional scan of depletion layer width perturbations in the semiconductor due to the energetic image is achieved.

8. A method in accordance with claim 7 wherein the plurality of reading acoustic waves are each of a different frequency one from the other.

9. Apparatus for converting an energetic image into an electrical signal comprising a semiconductor, means for applying an electrical field to said semiconductor for charging the surface states thereof to produce a relatively uniform depletion layer width, means for imaging the energetic image on said semiconductor whereby perturbations appear in the depletion layer width in accordance with information present in the energetic image, a piezoelectric substrate adjacent to said semiconductor, means for propagating a reading acoustic Wave along said piezoelectirc substrate in one direction with the depletion layer width perturbations producing corresponding propagation coefficient perturbations of the reading acoustic wave to form a modulated output acoustic wave, and means for converting said modulated output acoustic wave into an electrical signal.

10. Apparatus in accordance with claim 9 wherein said means for applying an electrical field to said semiconductor comprises an electric field generator coupled across said semiconductor.

11. Apparatus in accordance with claim 9 wherein said means for applying an electric field to said semiconductor comprises means for propagating a scanning acoustic wave along said piezoelectric substrate in a second direction opposite to the one direction, with the electric field associated with said scanning acoustic wave sequentially charging the surface states of said semiconductor along its extent.

12. Apparatus in accordance with claim 9 wherein said means for propagating a reading acoustic wave includes an interdigitated electrode disposed on said piezoelectric substrate.

13. Apparatus in accordance with claim 9 including means for propagating a plurality of reading acoustic waves, said plurality of reading acoustic waves being propagated parallel to one another along one dimension of said semiconductor but spaced with respect to one another along a second dimension of said semiconductor.

14. Apparatus in accordance with claim 13 wherein said means for propagating a plurality of reading acoustic waves comprises a plurality of interdigitated electrodes on said piezoelectric substrate spaced with respect to each other along the second dimension of said semiconductor.

15. Apparatus in accordance with claim 13 wherein said means for propagating a plurality of reading acoustic waves comprises a single interdigitated electrode disposed on said piezoelectric substrate, said single interdigitated electrode having a varying width along the second dimension of said semiconductor, and including a signal source of varying frequency for driving said single interdigitated electrode wherein different width portions of said single interdigitated electrode are responsive to different frequencies of said signal source of varying frequency for propagating a plurality of reading acoustic waves of corresponding different frequencies.

16. A method for scanning a pattern of energy distribution capable of causing depletion width variations in a semiconductor comprising the steps of charging the surface states of the semiconductor to produce a relatively uniform depletion layer width along the semiconductor, exposing the semiconductor to the pattern of energy distribution whereby corresponding perturbations appear in the depletion layer of the semiconductor, propagating a reading acoustic wave past the semiconductor so that the depletion layer perturbations cause corresponding propagation coefficient perturbations of the reading acoustic wave to form an output acoustic wave modulated in accordance with the depletion layer perturbations in the semiconductor, and converting the output acoustic wave into an electrical signal.