SONIC IMAGE TRANSDUCER USING A STORAGE CAMERA

• US 3,772,457 A
• Filed: 03/29/1971
• Issued: 11/13/1973
• Est. Priority Date: 03/29/1971
• Status: Expired due to Term

• Current Assignee: Albert Macovski
• Original Assignee: Albert Macovski
• Inventors: Macovski, Albert
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Orsino, Jr., Joseph A.
• Application Number:
  US05/128,753
• Time in Patent Office: 960 Days
• Field of Search: 73/67.5R,67.5H,69 340/5H 350/3.5 178/DIG.18 356/106
• US Class Current: 348/163
• 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: H04N 5/30 Transforming light or analogous information into electric information scanning details H04N3/00; cameras or camera modules comprising electronic image sensors, or control thereof H04N23/00; circuitry of solid-state image sensors [SSIS] or control thereof H04N25/00
• CPC Class Codes: Y10S 359/901 Acoustic holography

Abstract

An acoustic to optical image converting system of the type in which an acoustic field originating from an object insonified by a sonic signal generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent light and in which the reflected object beam is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the acoustic field. A pulsed laser and an interferometer are used to generate the object beam and reference beam and selected interference patterns derived from different phase combinations of the laser beams and sonic signals are projected on the face of the storage type television camera. Outputs from the television camera corresponding to specified image components are electronically processed by a variety of system embodiments with and without video storage devices to filter the desired image information and reconstruct an image or hologram of the original object. The sonic source can similarly be pulsed in co-ordination with the pulsed laser to increase the sensitivity of the image system.

Claims

1. A sonic image transducer of the type in which a sonic image of an object immersed in an acoustic medium and insonified by a sonic signal generator source is impressed on a reflective vibrating surface at a boundary of the acoustic medium and illuminated with an object beam of coherent light, and in which the reflected object beam is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the sonic image impressed at the reflective vibrating surface comprising:

a pulsed laser synchronized with the sonic signal generator source and means for controlling said pulsed laser So that it can be turned on either during a positive or negative peak of the sonic signal generated by said sonic source, each of the laser pulses from said pulsed laser being a small part of the cycle of the insonifying signal;

interferometer means for generating from said pulsed laser beams an object beam for illuminating the sonic image and a reference beam for combination with the object beam to form an optical interference pattern;

an optical modulator interposed in the reference beam path and means for actuating said light modulator to introduce selected phase shifts in the reference beam;

a storage-type television camera positioned to receive on the camera target the pulsed interference patterns produced by said combined object and reference beams;

a video storage device coupled to the output of said television camera;

a first difference amplifier coupled to the output of said video storage device for generating the difference of first and second signals corresponding to first and second intensities appearing on the camera face plate, said first and second signals corresponding to positive and negative peaks of the sonic signal with no phase shift introduced in the reference beam by the light modulator;

first multiplier means for squaring the difference between said first and second signals;

second difference amplifier means for generating the difference between third and fourth signals corresponding to third and fourth intensities appearing on the camera face plate, said third and fourth intensities corresponding to positive and negative peaks of the sonic signal with a phase shift of pi /2 introduced by the light modulator in the reference beam;

second multiplier means for squaring the difference between said third and fourth signals;

an adder for adding the outputs from said first and second multipliers; and

a cathode ray tube display for applying the output from said adder comprising the envelope signal containing the desired image information.

2. A sonic image transducer as set forth in claim 1 wherein said provided means for pulsing the sonic signal generating source so that laser pulses and sonic pulses are coincident at the reflective vibrating surface.

3. An acoustic to optical image converting system of the type in which an acoustic field originating from an object insonified by a sonic signal generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent light and in which the reflected object beam is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the acoustic field comprising:

a pulsed laser synchronized with the sonic signal generator source and means for controlling said pulsed laser to pulse either during a positive or negative peak of the sonic signal;

optical modulator means interposed in the reference beam path and means for driving said modulator to introduce selected phase shifts in the reference beam;

a storage-type television camera positioned to receive on the camera target the interference patterns produced by said combined object and reference beams;

a high pass filter coupled to the output of said television camera;

a squaring circuit coupled to the output of said high pass filter; and

a cathode ray tube display coupled to the output of said squaring circuit for summing and displaying squared signals received from the television camera.

4. An acoustic to optical image converting system as set forth in claim 3 wherein is provided means for pulsing the sonic signal generating source so that laser pulses and sonic pulses are coindicent at the reflective vibrating surface.

5. A system for visualizing acoustic images of the type in which an acoustic field originating from an object insonified by a sonic signal generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent lighT and in which the reflective object beam is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the acoustic field comprising:

a pulsed laser and means for controlling said pulsed laser to produce a pulse duration of many cycles of the sonic signal generated by the sonic source;

optical modulator means interposed in the reference beam path and means for driving said modulator to cyclicly temporally offset the reference beam at a frequency substantially the same as the frequency of the sonic signal;

a storage-type television camera positioned to receive on the camera face the interference patterns produced by said combined object and reference beams and to integrate said interference patterns over many cycles of the sonic signal;

high pass filter means coupled to the output of said television camera for eliminating DC and constant signal components;

squaring circuit means coupled to the output of said high pass filter means; and

adder means coupled to the squaring circuit means thereby to isolate the desired envelope signal representing the acoustic image information.

6. A system for visualizing an acoustic image as set forth in claim 5 wherein a video storage device is interposed in the signal processing circuitry at the output of the vidicon camera.

7. A system for visualizing acoustic images as set forth in claim 5 wherein said adder means comprises cathode ray tube display means coupled to the output of the squaring circuit means.

8. A system for visualizing acoustic images as set forth in claim 5 wherein is provided means for pulsing the sonic signal generating source so that laser pulses and sonic pulses are coincident at the reflective vibrating surface.

9. An acoustic to optical image converting system of the type in which an acoustic field originating from an object insonified by a sonic signal generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent light and in which the reflected object beam is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the acoustic field comprising;

a pulsed laser and means for controlling said laser to produce pulsed durations of many cycles of the sonic signal;

interferometer means for generating from the laser pulse beams an object beam and a reference beam, said interferometer constructed and arranged to provide off-axis recombination of the object beam reflected from the acoustic image and the reference beam thereby to modulate the optical interference pattern corresponding to the acoustic image on a spatial frequency carrier, the frequency of said spatial frequency carrier determined by the angle between the recombined off-axis reference and object beams;

a storage type television camera positioned to receive on the camera face the recombined object and reference beams, said interferometer arranged to combine the object and reference beams at an angle to generate a spatial frequency carrier having a frequency substantially at the resolution capability of the television camera;

high pass filter means coupled to the output of said storage type television camera for eliminating DC and constant signal components from the output; and

envelope detector means for detecting the envelope signal corresponding to the desired image information.

10. An acoustic to optical image converting system as set forth in claim 9 wherein said envelope detecting means comprises modulator means for amplitude modulating the filtered television camera on a high frequency carrier at least twice the band width of the television camera, filter means for filtering one of the side bands of the modulated signal, and detector means for envelope detecting the vestigial side band of said modulated signal.

11. An acoustic to optical image converting system as set forth in claim 9 wherein a video storage device is interposed in the signal processing circuitry coupled to the output of said television camera.

12. An acoustic to optical image converting system as set forth in claim 9 wherein is also provided an optical display means coupled to the output of said envelope detector means.

13. An acoustic to optical image converting system as set forth in claim 9 wherein is also provided means for pulsing the sonic source so that sonic pulses reflected from the object and laser pulses are coincident at the reflective vibrating surface.

14. A method of acoustic to optical image conversion using a sonic image transducer of the type in which an acoustic field originating from an object insonified by a sonic signal generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent light and in which the object beam is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the acoustic image impressed at the reflective vibrating surface comprising:

pulsing the object beam in pulse durations lasting a fraction of a cycle of the insonifying signal and illuminating the acoustic image with a first pulse to produce a first intensity pattern;

projecting said first intensity pattern on the face plate of a storage-type television camera and reading out said first intensity pattern to provide a first signal;

storing said first signal;

illuminating said acoustic image with a second object beam pulse during a phase of the sonic signal opposite that during illumination by the first pulse to produce a second intensity pattern;

projecting said second intensity pattern on the camera face plate and reading out said pattern to form a second signal;

storing said second signal;

phase shifting the reference beam pi /2;

illuminating said acoustic image with a third object beam pulse thereby to provide a third intensity pattern;

projecting said third intensity pattern on the camera face plate and reading out said pattern to produce a third signal;

storing said third signal;

illuminating said acoustic image with a fourth object beam pulse during a phase of the insonifying signal opposite that during illumination by the third pulse to form a fourth intensity pattern;

projecting said fourth intensity pattern on the camera face plate and reading out said fourth pattern to produce a fourth signal;

storing said fourth signal;

generating a first difference signal corresponding to the difference between the first and second signals;

squaring said first difference signal;

generating a second difference signal corresponding to the difference between the third and fourth signals;

squaring said second difference signal;

summing the squares of the first and second difference signals; and

applying the summed signal to a cathode ray tube display.

15. A method of acoustic to optical image conversion as set forth in claim 14 wherein is provided the step of pulsing the sonic signal generating source to produce sonic pulses coincidental with the laser pulses at the reflective vibrating surface.

16. A method of acoustic to optical image conversion using a sonic image transducer of the type in which an acoustic field originating from an object insonified by a sonic generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent light and in which the object beam reflected from the acoustic image is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the sonic image comprising:

generating a first laser pulse having a duration of a fraction of the cycle of the insonifying signal and illuminating the acoustic image to form a first intensity pattern at the camera face plate;

shifting the path length of said reference beam by a half wavelength and illuminating the acoustic image with a second laser pulse at a time when The insonifying signal is of opposite polarity thereby generating a second intensity pattern on the camera face plate;

summing the first and second intensity patterns at the camera face plate and reading out a first signal corresponding to the sum of the first and second intensity patterns;

separating the AC component of said signal;

squaring said AC component to provide a first squared signal; and

applying said first squared signal to a cathode ray tube display;

shifting the phase of the reference beam by 90*;

illuminating the acoustic image with a third laser pulse;

shifting the reference beam by half a wavelength and illuminating the acoustic image with a fourth laser pulse at a time when the insonifying signal is of opposite polarity;

summing the third and fourth intensity patterns corresponding to the third and fourth laser pulses at the face plate of the television camera and reading out said patterns to produce a signal corresponding to the sum of the third and fourth intensity patterns;

separating the AC component of said signal;

squaring the AC component of said signal to provide a second squared signal;

applying said second squared signal to the cathode ray tube display; and

summing the first and second squared signals on the face of said cathode ray tube display.

17. A method of acoustic to optical image conversion as set forth in claim 16 wherein is provided the step of pulsing the sonic signal generating source to produce sonic pulses coincidental with the laser pulses at the reflective vibrating surface.

18. A method of acoustic to optical image conversion using a sonic image transducer of the type in which a sonic image originating from an object insonified by a sonic signal generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent light and in which the object beam is combined with a reference beam of coherent light to generate an optical interference pattern corresponding to the sonic image comprising:

Shifting the reference beam at a frequency equal to the frequency of the insonifying signal thereby forming an interference pattern of the combined object and reference beams with an unmodulated portion due to the sonic signal;

projecting said interference pattern on the face plate of a storage-type television camera;

integrating the intensity patterns formed on the television camera over many cycles of the insonifying signal;

reading out said integrated pattern to generate a first signal;

shifting the phase of the insonifying signal by 90*;

integrating the patterns on the camera face plate over many cycles of the insonifying signal to produce a second integrated pattern;

reading out said second integrated pattern to provide a second signal;

squaring the time varying portion of each of the first and second signals; and

adding the squares of said first and second signals.

19. A method of acoustic to optical image conversion as set forth in claim 18 wherein is provided the step of storing the first and second signals read out from the television camera.

20. A method of acoustic to optical image conversion as set forth in claim 18 wherein the step of adding the squared signals comprises summing said squared signals of the face of a a cathode ray tube.

21. A method of acoustic to optical image conversion as set forth in claim 18 wherein is provided the step of pulsing the sonic signal generating course to produce sonic pulses coincidental with the laser pulses at the reflective vibrating surface.

22. A method of acoustic to optical image conversion using a sonic image transducer of the type in which a sonic image originating from an object insonified by a sonic signal generating source is impressed on a reflective vibrating surface and illuminated with an object beam of coherent light and in which the object beam is combined with a reference beam of coheRent light to generate an optical interference pattern corresponding to the sonic image comprising:

aligning the object beam and reference beam at a slight angle with respect to each other thereby to modulate the optical interference pattern from the combined object and reference beams onto a spatial frequency carrier;

projecting the optical interference pattern and spatial frequency carrier onto the face plate of a storage-type television camera;

reading out an AC signal corresponding to the optical interference pattern and spatial carrier and eliminating constant components of the signal; and

envelope detecting the camera output signal to provide an envelope signal containing the desired image information.

23. A method of acoustic to optical image conversion as set forth in claim 22 wherein the step of envelope detecting the camera output signal comprises amplitude modulating a high frequency carrier with the television camera output, the frequency of said carrier being at least twice the camera video band width, filtering the upper band width of the modulated camera video output and detecting said filter signal.

24. A method of acoustic to optical image conversion as set forth in claim 22 wherein is provided the steps of pulsing the object beam and sonic signal so that the object beam pulses and sonic pulses are coincident at the reflective vibrating surface.