Closed loop LCD heater system

• US 6,535,266 B1
• Filed: 12/16/1999
• Issued: 03/18/2003
• Est. Priority Date: 12/16/1999
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Coffin, Ronald L., Cudworth, Daniel E., Nemeth, Paul R., Mosier, Donald E.
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): NGUYEN, DUNG T
• Application Number:
  US09/464,424
• Time in Patent Office: 1,188 Days
• Field of Search: 349/72, 349/169, 349/199, 219/209
• US Class Current: 349/161
• CPC Class Codes: G02F 1/133382 Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell

Abstract

An LCD heater having independent closed loop control over heating for a plurality of zones on the display, wherein each zone has a relatively homogeneous heat dissipation or heat sinking properties and one of the zones is a central region of the display which is heated by an ITO film and has its temperature sensed, by a transparent sensor, at a central point within the viewable section of the LCD.

Claims

1. An LCD comprising:

a liquid crystal panel having a plurality of thermal dissipation zones thereon;

plurality of thin film thermal sensors disposed on said liquid crystal panel, each of which is associated with and for independently measuring temperature of one of said plurality of thermal dissipation zones; and

,

plurality of closed loop heating systems, each of which is associated with and for independently applying heat to one of said plurality of thermal dissipation zones.

2. An LCD of claim 1 wherein each of said thermal dissipation zones has a predetermined characteristic of heat dissipation.

3. An LCD of claim 2 wherein said predetermined characteristic of heat dissipation is a predetermined level of homogeneity with respect to heat dissipation.

4. An LCD of claim 3 wherein each of said thermal dissipation zones is an isothermal dissipation zone.

5. An LCD of claim 1 wherein said plurality of thin film thermal sensors includes a transparent thermal sensor disposed across a viewable section of said LCD panel.

6. An LCD of claim 5 wherein one of said plurality of closed loop heating systems includes a feedback loop in which a temperature of one of said thermal dissipation zones is monitored for any effect on temperature of an application of heat to said one of said thermal dissipation zones.

7. An LCD of claim 6 wherein one of said plurality of thermal dissipation zones includes a centrally disposed region on said viewable section.

8. An LCD of claim 7 wherein another of said plurality of thermal dissipation zones includes an edge of said liquid crystal panel.

9. An LCD of claim 8 wherein one of said plurality of closed loop heating systems includes a foil heater disposed along said edge of said liquid crystal panel.

10. An LCD of claim 9 wherein one of said plurality of closed loop heating systems includes a planar heating element of a sheet of a transparent resistive film over said viewable section.

11. An LCD of claim 9 wherein said foil heater is disposed between said LCD panel and one of a plurality of mounts.

12. An LCD of claim 11 wherein a thermal isolating material has been coupled to one of said plurality of mounts to provide for an increase in homogeneity of heat dissipation characteristics across said liquid crystal panel.

13. An LCD of claim 12 further including a reference thermistor used to provide correction signals in output paths of said thin film thermal sensors.

14. An LCD of claim 13 wherein each of said plurality of thermal dissipation zones has a predetermined target temperature toward which a heater driver drives a temperature characteristic.

15. An LCD heater comprising:

first thin film means for sensing a temperature of a first isothermal dissipation zone of a liquid crystal panel;

second thin film means for sensing a temperature of a second isothermal dissipation zone of a liquid crystal panel;

first means for independently manipulating a temperature characteristic of said first zone; and

,

second means for independently manipulating a temperature characteristic of said second zone.

16. An LCD heater of claim 15 wherein said first thin film means is transparent and disposed over a viewable section of said liquid crystal panel.

17. An LCD heater of claim 16 including a means for providing a reference temperature.

18. An LCD heater of claim 17 wherein said first means for independently manipulating a temperature comprises a foil heater disposed on an edge of said liquid crystal panel.

19. An LCD heater of claim 18 wherein second means for independently manipulating a temperature comprises a transparent thin film heater disposed on said viewable section of said liquid crystal panel.

20. A method of improving the optical characteristic of a liquid crystal display comprising the steps of:

providing a liquid crystal panel having an optical compensator thereon which is optically sensitive to thermal and mechanical stresses thereon;

dividing said liquid crystal panel into a plurality of isothermal heat dissipation zones;

providing independent temperature monitoring of said zones at points within a viewing section of said liquid crystal display; and

,

providing independent closed loop control of a temperature for each of said plurality of isothermal heat dissipation zones.