ACOUSTIC TO OPTICAL IMAGE CONVERTER USING AN ACOUSTIC GRATING

• US 3,711,823 A
• Filed: 07/27/1970
• Issued: 01/16/1973
• Est. Priority Date: 07/27/1970
• Status: Expired due to Term

• Current Assignee: Philip S. Green
• Original Assignee: Philip S. Green
• Inventors: Green, Philip S.
• Primary Examiner(s): Engle, Samuel W.
• Assistant Examiner(s): Moskowitz, N.
• Application Number:
  US05/058,442
• Time in Patent Office: 904 Days
• Field of Search: 332/7.51 340/5H,5I 350/161,3S 181/.5NP 73/67.5H
• US Class Current: 367/7
• CPC Class Codes: G01H 9/002 for representing acoustic field distribution sonar systems for imaging G01S7/56, G01S15/89; acoustic holography G03H3/00
• CPC Class Codes: G03H 3/00 Holographic processes or apparatus using ultrasonic, sonic or infrasonic waves for obtaining holograms; Processes or apparatus for obtaining an optical image from them G03H1/22 takes precedence; acoustic non-destructive testing using holographic methods G01N29/0663; seismology using acoustic vibrations G01V1/00; non-holographic methods for visualizing acoustic waves G10K15/00
• CPC Class Codes: Y10S 181/402 Liquid

Abstract

A system for converting an acoustic wave field to a light wave field including an acoustically transmissive medium, a solid elastic or liquid reflective interface at a boundary of the medium, means for generating an acoustic wave field in the medium, means for optically detecting the acoustic wave field incident at the reflective interface, and a grating or grid immersed in the acoustic medium adjacent to but spaced from the reflective interface. The grating is formed of a material having an acoustic impedance different from the medium thereby to superimpose the acoustic wave field on a spatial frequency carrier.

Claims

1. In a system for converting an acoustic wave field to a light wave field including an acoustically transmissive medium, a deformable reflective interface at a boundary of said medium, means for generating an acoustic wave field in the medium, and means for detecting the acoustic wave field impressed at the deformable reflective interface by light incident on the reflective interface, the improvement comprising:

a grating immersed in said medium adjacent to but spaced from the reflective interface for superimposing the acoustic wave field on a spatial frequency carrier wave to facilitate the subsequent light detection on the impressed wave field, said grating formed of a material having an acoustic impedance different from the medium.

2. A system as set forth in claim 1 wherein said grating comprises coplanar parallel lines of material.

3. A system as set forth in claim 1 wherein said grating comprises hollow tubes of air.

4. A system as set forth in claim 3 wherein said grating comprises a solid material having hollow tubes formed therein.

5. A system as set forth in claim 1 wherein said grating comprises an array of wires.

6. A system as set forth in claim 5 wherein said wire grating is embedded in plastic.

7. A system for converting an acoustic wave field to a light wave field as set forth in claim 1 wherein is also provided spatial filter means for spatially filtering light reflected from the reflective interface thereby substantially to eliminate undiffracted portions of the light.

8. A system for converting an acoustic wave field to a light wave field as set forth in claim 1 wherein is also provided means for imaging light reflected from the reflective surface, means for scanning the imaged light pattern thereby to generate an electrical signal having frequency components corresponding to the components of the imaged pattern, and means for electrically filtering said signal to extract signal components corresponding to desired imaged information.

9. A system as set forth in claim 8 wherein is also provided an electronically addressable optical display for displaying the filtered signal components.

10. An acoustic to optical image converter comprising:

an acoustically transmissive medium in which is immersed an object to be imaged;

means for insonifying an object immersed in the medium thereby to generate an acoustic wave field representative of the object;

means for modulating the acoustic wave field on a spatial frequency carrier wave;

a reflective deformable surface positioned at a boundary of the medium for displaying the modulated acoustic wave field originating frOm the insonified object;

means for optically detecting and visualizing the modulated acoustic image displayed on said reflective surface by light incident on the reflective surface.

11. An acoustic to optical image converter as set forth in claim 10 wherein is also provided means for spatially filtering the light reflected from the reflective surface.

12. A acoustic to optical image converter as set forth in claim 10 wherein is also provided means for demodulating the optically detected image information from the spatial frequency carrier wave.

13. An acoustic to optical image converter as set forth in claim 10 wherein is provided means for imaging light reflected from the reflective surface, means for scanning the imaged light pattern thereby to generate an electrical signal having frequency components corresponding to the components of the imaged pattern, and means for electrically filtering said signal to extract signal components to desired image information.

14. A system as set forth in claim 13 wherein is also provided an electronically addressable optical display for displaying the filtered signal components.

15. An acoustic to optical image converter as set forth in claim 13, wherein is also provided spatial filter means in the Fourier transform plane of the imaged coherent light.

16. In a system for converting an acoustic wave field to a light wave field including an acoustically transmissive medium, a deformable reflective interface at a boundary of said medium, means for generating an acoustic wave field in the medium, and means for detecting the acoustic wave field impressed at the reflective interface by light incident on the reflective interface, the improvement comprising:

a grating immersed in said medium adjacent to but spaced from the reflective interface for superimposing the acoustic wave field on a spatial frequency carrier wave to spatially offset the wave field impressed on the interface, said grating being formed of a material having an acoustic impedance different from the medium;

means for forming an image from the light reflected from the reflective interface; and

means for filtering undiffracted light components reflected by the reflective interface from the formed image.

17. A system as set forth in claim 16 wherein said filtering means comprises spatial filter means.

18. A system as set forth in claim 16 wherein said image forming means includes scanning means for generating an electrical signal and an electronically addressable optical display and wherein said filtering means comprises electrical filtering means for filtering electrical signal components corresponding to desired image information.

19. A system as set forth in claim 16 wherein said filtering means includes both electrical and spatial filtering means.

20. An acoustic grating for use in acoustic to optical image converters for superimposing an acoustic wave field on a spatial frequency carrier wave comprising:

a layer of solid material having air channels formed therein.

21. An acoustic grating for use in acoustic to optical image converters for superimposing an acoustic wave field on a spatial frequency carrier wave comprising:

an array of air spaces sandwiched between layers of plastic.

22. An acoustic grating for use in acoustic to optical image converters for superimposing an acoustic wave field on a spatial frequency carrier wave comprising an array of wires sandwiched between layers of plastic.

23. A method for acoustic to optical image conversion comprising:

immersing an object to be imaged in an acoustically transmissive medium;

insonifying the object immersed in the medium thereby generating an acoustic wave field representative of the object;

superimposing said acoustic wave field representative of the object on a spatial frequency acoustic carrier wave in the medium;

impressing and displaying the modulated spatial frequency acoustic carrier wave on a reflective defOrmable surface positioned at the boundary of the medium;

optically illuminating the displayed spatial frequency acoustic carrier wave modulated with the acoustic wave field representative of the object with coherent light and optically imaging the reflected light;

electronically scanning the so formed optical image to generate an electrical signal comprising signal components corresponding to the acoustic wave field components; and

electrically filtering said electrical signal to separate desired image information signal components.

24. A method for converting an acoustic wave field to a light wave field comprising:

insonifying an object to be imaged thereby generating an acoustic wave field representative of the object;

superimposing the acoustic wave field on a spatial frequency acoustic carrier wave;

impressing the acoustic carrier wave modulated by the acoustic wave field representative of the object on a deformable reflective surface; and

illuminating the deformable surface with coherent light and imaging the reflected light to form an image of said surface.