LIQUID CRYSTAL DEVICES AND SYSTEMS FOR ULTRASONIC IMAGING

• US 3,707,323 A
• Filed: 11/06/1970
• Issued: 12/26/1972
• Est. Priority Date: 11/06/1970
• Status: Expired due to Term

• Current Assignee: Lawrence W. Kessler, Samuel P. Sawyer
• Original Assignee: Lawrence W. Kessler, Samuel P. Sawyer
• Inventors: Kessler, Lawrence W., Sawyer, Samuel P.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Bauer, Edward S.
• Application Number:
  US05/087,553
• Time in Patent Office: 781 Days
• Field of Search: 350/3.5,150,160,161 250/199 332/7.51
• US Class Current: 349/23
• 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: G02F 1/13 based on liquid crystals, e.g. single liquid crystal display cells

Abstract

A device is disclosed which includes a layer comprising a nematic liquid crystal toward which ultrasonic wavefronts are directed. A marked change over any particular area of the layer occurs from a clear state to a light-scattering state when the intensity of the ultrasound applied to that area exceeds a threshold value. The degree of light scattering obtainable is found to be functionally related to the intensity of the applied ultrasound above the threshold. A matrixed array of such devices is arranged in a system with suitable ultrasonic addressing means and scanning means to provide a real-time image display system having a gray-scale. A system for visualizing ultrasonic image information either conventionally or holographically is also provided by causing a sound beam carrying image information as well as a reference beam to impinge on a common area of such a device. The resulting pattern of ultrasonic intensity variations over the area causes light to be variably scattered from different points in the area in accordance with the ultrasonic intensity pattern, thereby rendering visible the analogue optical hologram of the image.

Claims

1. An acoustic-optic display device, comprising:

a light-modulating layer comprising a nematic liquid crystal responsive to applied ultrasonic energy of the order of magnitude 10 megahertz to higher of intensity beyond a threshold value to scatter incident light; and

meAns for applying to said liquid crystal layer ultrasonic energy of an intensity greater than said threshold to stimulate scattering of said incident light.

2. An acousto-optic display device as in claim 1, which further includes:

a light-reflective layer with which said liquid crystal layer interfaces, and in which said light is incident upon the surface of the crystal layer opposite that of said interface.

3. An acousto-optic display device as in claim 1, which further includes:

a light-absorptive layer with which said liquid crystal layer interfaces, and in which said light is incident upon the surface of said layer opposite that of the absorptive surface.

4. An acousto-optic display device as in claim 1, in which said light is incident upon the surface of said crystal layer opposite from the one which is viewed.

5. An acousto-optic display device as in claim 1, wherein said means for applying ultrasonic energy includes a plurality of transducers positioned so as to establish an array of said stimulated areas over said crystal layer, and which further includes means for addressing said transducers with actuating signals modulated in accordance with image information to cause said incident light to be scattered by said stimulated areas in accordance with said image information.

6. An acousto-optic display device as in claim 5, wherein said layer is separated into discrete units each including one of said stimulated areas, and wherein each of said plurality of transducers is discrete and respectively matched to one of said areas.

7. An acousto-optic display device as in claim 1, in which degree of said scattering of said incident light by said liquid crystal layer is a function of the intensity of the applied ultrasonic energy beyond threshold.

8. An acousto-optic display device as in claim 7, in which said means for applying ultrasonic energy to an area of said layer includes an ultrasonic beam source spaced from said layer, with said beam being directed toward said area, and which further includes means for spatially modulating said ultrasonic beam with image information to stimulate the scattering of said incident light from said area in accordance with said image information.

9. An acousto-optic display device as in claim 7, in which said means for applying ultrasonic energy to an area of said layer includes two sources of ultrasonic beams spaced from said layer and of the same frequency and coherent with respect to each other, whose directions of propagation make an angle with respect to each other so that both beams converge toward said area on said crystal layer, interfering thereon to form a stationary pattern of varying ultrasonic energy intensity over said area, and which further includes means for modulating one of said beams with image information so that said stationary pattern bears said information, said pattern of ultrasonic intensity variations stimulating the scattering of said incident light from said stimulated area in accordance with said intensity variations, giving rise to a visible corresponding pattern over said area which at any moment constitutes a hologram bearing said image information.