LIQUID CRYSTAL IMAGING SYSTEM

• US 3,770,961 A
• Filed: 11/24/1972
• Issued: 11/06/1973
• Est. Priority Date: 11/24/1972
• Status: Expired due to Term

• Current Assignee: William E. Westell
• Original Assignee: William E. Westell
• Inventors: Westell, William E.
• Primary Examiner(s): Bauer, Edward S.
• Application Number:
  US05/309,287
• Time in Patent Office: 347 Days
• Field of Search: 250/83R,83.3HP,208,209,238 350/78,16R,16P,16LC 356/45
• US Class Current: 250/331
• CPC Class Codes: G02B 23/12 with means for image conversion or intensification
• CPC Class Codes: G02F 1/132 Thermal activation of liquid crystals exhibiting a thermo-optic effect

Abstract

Infrared radiation is imaged on a film of liquid crystal whose characteristic color is a function of its absolute temperature. A heat exchanger in juxtaposition with the liquid crystal is provided for maintaining the ambient temperature of the liquid crystal at the temperature of maximum sensitivity to infrared radiation. A remote sensor responsive to the characteristic color of the liquid crystal controls the heating and cooling cycles of the heat exchanger. In consequence, the liquid crystal is maintained at the temperature of maximum sensitivity by remote sensing of color balance over the entire useful area of the film.

Claims

2. The apparatus as claimed in claim 1 wherein said focusing means is a reflector.

3. The apparatus as claimed in claim 1 wherein said heat exchanger is a thermocouple exhibiting a Peltier effect.

4. The apparatus as claimed in claim 1 wherein said sensing means includes:

light source means;

b. detecting means responsive to the characteristic color of said liquid crystal;

c. a differential amplifier electrically connected to said detecting means; and

d. switch means electrically connected to said differential amplifier means and said heAt exchanger.

5. The apparatus as claimed in claim 4 wherein said detecting means includes:

a. a first phototube;

b. a first optical filter optically interposed between said first phototube and said liquid crystal means;

c. a second phototube; and

d. a second optical filter optically interposed between said second phototube and said liquid crystal means.

6. The apparatus as claimed in claim 1 wherein said liquid crystal means is a cholesteric liquid crystal.

7. An apparatus for presenting a highly contrasted visual representation of an infrared radiation pattern comprising:

a. a body;

b. a carriage reciprocally mounted to said body at one end thereof;

c. an objective lens mounted in said body;

d. an eyepiece mounted in said carriage;

e. focusing means mounted to said body at the other end thereof;

f. liquid crystal means operatively connected to said focusing means at the focal point of said focusing means, infrared radiation focused on said liquid crystal means by said focusing means, said liquid crystal means having a characteristic color and a sensitivity to infrared radiation as a function of its absolute temperature, an infrared radiation image presented on said liquid crystal means by infrared radiation focused thereon;

g. a heat exchanger producing a temperature rise and a temperature drop at a rate greater than the rate of temperature rise and temperature drop produced by ambient temperature, said heat exchanger means operatively connected to said liquid crystal means for controlling the temperature of said liquid crystal means; and

h. sensing means electrically connected to said heat exchanger and optically communicating with said liquid crystal means, said sensing means sensing the characteristic color of said liquid crystal means and generating output signals as a function of the sensed characteristic color of said liquid crystal means, said heat exchanger responsive to said output signals generated by said sensing means, said liquid crystal means heated and cooled by said heat exchanger at a rate which is greater than the heating and cooling rate provided by the ambient temperature about said liquid crystal means, said liquid crystal means maintained at its absolute temperature of maximum sensitivity to infrared radiation by said heat exchanger.

8. A method of maintaining a liquid crystal at a specific temperature, said liquid crystal having a characteristic color as a function of its temperature, said method comprising the steps of:

a. sensing a predetermined characteristic color of said liquid crystal;

b. generating control signals related to said sensed characteristic color; and

c. heating and cooling said liquid crystal at a rate which is greater than the ambient temperature heating and cooling rate in response to said control signals for maintaining said lqiuid crystal at said predetermined characteristic color, said specific temperature defined by said determined characteristic color.