ULTRASONIC VISUALIZATION BY PULSED BRAGG DIFFRACTION

• US 3,737,573 A
• Filed: 08/30/1971
• Issued: 06/05/1973
• Est. Priority Date: 08/30/1971
• Status: Expired due to Term

• Current Assignee: Lawrence W. Kessler
• Original Assignee: Lawrence W. Kessler
• Inventors: Kessler, Lawrence W.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Martin, John C.
• Application Number:
  US05/175,954
• Time in Patent Office: 645 Days
• Field of Search: 178/7.3D,7.5D,DIG.18 250/199 350/161,162 343/17 73/67.7,69,67.5H,67.5R 340/5MP
• US Class Current: 348/769
• CPC Class Codes: G01N 29/06 Visualisation of the interior, e.g. acoustic microscopy medical or veterinary diagnosis using sonic waves A61B8/00; representation of acoustic wave distribution G01H3/125, G01H9/002; short-range imaging systems using reflection of acoustic waves G01S15/8906
• CPC Class Codes: G02F 1/33 Acousto-optical deflection devices circuit or control arrangements therefor G02F1/113

Abstract

An improvement in reflection mode Bragg display systems of the type wherein an acoustic beam is incident on an object which by reflection spatially modulates this sound field with its image information, a laser light beam interacts with such modulated sound field to undergo Bragg diffraction, thereby reproducing the image information in the diffracted light, and an optical system receiving such diffracted light images various desired cross sections of the object with a discrimination limited by the overall depth of focus of the optical imaging system. Control means are incorporated for delivering both the acoustic beam and the light beam in synchronized bursts of controlled duration to allow any of a plurality of cross-section within the acoustic depth of focus to be visualized, and spurious acoustic images eliminated, with a discrimination depth dependent on the duration of the acoustic burst. The light burst is delayed with respect to the initiation of the sound burst, and its duration limited, so as together to insure proper coincidence of the light with the sound energy reflected from the particular object plane selected for imaging.

Claims

1. Light-sound interaction apparatus utilizing a laser light beam and comprising:

a Bragg light-sound interaction cell including a sound conducting medium and means for propagating wavefronts of sound energy within said medium;

means for projecting into said cell said light beam to obtain Bragg light-sound interaction;

means for repetitively pulsing said sound enErgy in bursts of predetermined duration;

means for repetitively pulsing said light beam in bursts of predetermined duration; and

means for coordinating said means for pulsing said sound energy and said means for pulsing said light beam for selecting a particular one of a plurality of available cross-sections of an object positioned in said medium.

2. A system for developing an optical image of a preselected cross-section of an object to be examined and utilizing a laser light beam, comprising:

a light-sound interaction cell adapted to receive said object within said cell including a sound-conducting medium;

means for propagating wavefronts of sound energy of predetermined wavelength in said medium to be incident on said object, said energy being at least partially reflected by said object along a path within said conducting medium;

means for projecting said laser light beam across a portion of said path to obtain Bragg light-sound interaction between said light and said reflected sound energy, providing at least one Bragg diffraction optical image of said object;

means for repetitively pulsing said sound energy in bursts or predetermined duration; and

means synchronized to said sound pulsing means for repetitively pulsing said light beam in bursts or predetermined duration to obtain said light-sound interaction only during the presence within said laser-illuminated path portion of the sound energy reflected by said preselected object cross-section so that said optical image represents said preselected cross-section of said object.

3. A system as in claim 2, in which said system further includes an optical system for projecting said image upon on imaging surface, said optical system having a depth of focus within which said imaged cross-section lies.

4. A system as in claim 2, in which said optical system compensates the astigmatic demagnification of said image.

5. A system as in claim 3 in which the focus of said optical system may be moved to include different regions of the object within the depth of focus.

6. A system as in claim 2 in which for each sound burst a corresponding light burst is furnished, and in which said light pulsing means includes means for delaying the initiation of each light pulse with respect to the initiation of its corresponding sound burst.

7. A system as in claim 2 in which said reflection path coincides with the path of travel of said incident sound burst to said object, and in which the rate of repetition of said sound light bursts is such as to avoid Bragg-imaging of said incident sound burst.

8. A system as in claim 2 in which the duration of said sound burst is adjustable in accordance with the degree of discrimination dsired.

9. A system as in claim 2 in which said projecting means is adjustable to increase or decrease said laser-illuminated portion of said reflection path.

10. A system as in claim 6 in which said light burst is initiated and persists only with the presence within said laser-illuminated portion of said reflection path of a predetermined substantial fraction of the sound energy reflected by said imaged cross-section.