Heater control system for liquid crystal device

Details Heater control system for liquid crystal device Heater control system for liquid crystal device

1977-06-17

1978-10-10

Tokar, M.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

350331, 350351, G01J 120

Patent

active

041198425

ABSTRACT:
A twisted nematic liquid crystal device contains a liquid crystal material having dielectric anisotropy .DELTA..epsilon. which is positive for certain values of temperature and frequency of an electrical signal applied across the material and negative for other values of these parameters. The device includes a heater and a test area (separate from the display area of the device) at which transmittance of light is monitored by a heater control circuit. A test frequency chosen to give .DELTA..epsilon..apprxeq.0 at the minimum desired operation temperature of the device is applied across the test area and the light transmittance is monitored to assure that the temperature is high enough. When the temperature is too low, the heater element is automatically energized to increase the temperature of the liquid crystal device.

REFERENCES:
patent: 2792484 (1957-05-01), Gurewitsch
patent: 4029393 (1977-06-01), Dungan

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