SYSTEM AND METHOD FOR ACCURATELY MAINTAINING LCD LUMINANCE, CONTRAST, AND RESPONSE TIME AT LOW TEMPERATURES

Abstract

A liquid crystal display (LCD) having a temperature regulation framework which utilizes a digital to analog converter. The thermal management system involves display heating controlled based on temperature values calculated for the center of the display.

Claims

1. A system for maintaining a liquid crystal display comprising: a liquid crystal display assembly comprising a processor; a heating element in electronic communication with the processor; a temperature measuring device in electronic communication with the processor, wherein the temperature measuring device is positioned proximate to edge glass located away from a center of the liquid crystal display; and a power supply; wherein the temperature measuring device is adapted to communicate to the processor a first temperature value, wherein the first temperature value is a measurement of edge glass temperature; wherein the processor is configured to calculate a second temperature value based on the first temperature value, wherein the second temperature value is an estimate of temperature of liquid crystal material positioned at the center of the liquid crystal display; wherein the processor is configured to adjust the heating element to achieve a desired temperature threshold when the second temperature value does not meet the desired temperature threshold; and wherein the heating element comprises a thermally conductive film or grid in thermal communication with liquid crystal material of the liquid crystal display assembly.

2. The system of claim 1 further comprising: a heat input lookup table for determining a steady state temperature delta based on at least one selected from the group of a digital analog control converter value and a measured heating element value; wherein the steady state temperature delta is capable of representing a temperature gradient between edge glass and liquid crystal material positioned at the center of the liquid crystal display.

3. The system of claim 1, wherein: the processor is configured to cause the heating element to increase by one when the second temperature value is less than the desired temperature threshold; the processor is configured to cause the heating element to decrease by one when the second temperature value is greater than the desired temperature threshold; and the processor is configured to cause no change to the heating element when the second temperature value meets the desired temperature threshold.

4. The system of claim 1, wherein the temperature measuring device comprises a thermistor or thermocouple.

5. The system of claim 2, wherein the second temperature value is the sum of the steady state temperature delta and the at least one measured edge glass temperature value.

6. The system of claim 1, wherein LCD luminance, contrast and response time are maintained below 0° C. to −200° C.

7. The system of claim 1, wherein the LCD assembly comprises an aircraft cockpit display, ground vehicle display, boat display, or submarine display.

8. A system for maintaining a liquid crystal display comprising: a liquid crystal display assembly comprising a control unit; a heater in electronic communication with the control unit; a temperature measuring device in electronic communication with the control unit; and a power supply; wherein the temperature measuring device is adapted to communicate to the control unit at least one measured edge glass temperature value; wherein the control unit includes a processor to calculate a center temperature value for the display based on the at least one measured edge glass temperature value and a steady state temperature delta; and wherein the control unit is configured to regulate the heater to meet a desired center temperature threshold.

9. The system of claim 8, further comprising: a heat input lookup table for determining the steady state temperature delta based on at least one selected from the group of a digital analog control converter value and a measured heater value; wherein the steady state temperature delta is capable of representing a temperature gradient between edge glass and liquid crystal material positioned at the center of the liquid crystal display.

10. The system of claim 8, wherein: the control unit is adapted to cause the heater to increase by one when the calculated center temperature value is less than the desired center temperature threshold; the control unit is adapted to cause the heater to decrease by one when the calculated center temperature value is greater than the desired center temperature threshold; and the control unit is adapted to cause no change to the heater when the calculated center temperature value meets the desired center temperature threshold.

11. The system of claim 9, wherein calculated center temperature is the sum of the steady state temperature delta and the at least one measured edge glass temperature value.

12. The system of claim 11, wherein the heater comprises a thermally conductive grid including a plurality of each horizontal and vertical controlled-resistance heater conductors in thermal communication with liquid crystal material of the liquid crystal display assembly.

13. The system of claim 8, wherein LCD luminance, contrast and response time are maintained below 0° C. to −200° C.

14. A method for maintaining a liquid crystal display comprising: providing a processor; providing a heating element in electronic communication with the processor; providing a temperature measuring device in electronic communication with the processor, wherein the temperature measuring device is positioned proximate to edge glass located away from a center of the liquid crystal display; providing a power supply; causing the temperature measuring device to communicate to the processor at least one measured edge glass temperature value; causing the processor to calculate a center temperature value for the liquid crystal display based on the at least one measured edge glass temperature value and a steady state temperature delta; and causing the processor to regulate the heating layer to meet a desired center temperature threshold.

15. The method of claim 14, wherein a heat input lookup table is used for determining the steady state temperature delta based on at least one selected from the group of a digital analog control converter value and a measured heating element value, wherein the steady state temperature delta is used to represent a temperature gradient between edge glass and liquid crystal material positioned at the center of the liquid crystal display.

16. The method of claim 14, further comprising: causing the processor to cause the heating element to increase by one when the calculated center temperature value is less than the desired center temperature threshold; causing the processor to cause the heating element to decrease by one when the calculated center temperature value is greater than the desired center temperature threshold; and causing the processor to cause no change to the heating element when the calculated center temperature value meets the desired center temperature threshold.

17. The method of claim 14, wherein the temperature measuring device comprises a thermistor or thermocouple.

18. The method of claim 15, wherein calculated center temperature is the sum of the steady state temperature delta and the at least one measured edge glass temperature value.

19. The method of claim 14, wherein the heating element comprises a thermally conductive film or grid in thermal communication with liquid crystal material of the liquid crystal display assembly.

20. The method of claim 14, wherein LCD luminance, contrast and response time are maintained below 0° C. to −200° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Novel features and advantages of the present invention, in addition to those expressly mentioned herein, will become apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawings. The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that different references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

[0015] FIG. 1 is a front perspective view of an exemplary LCD being exposed to cold ambient air;

[0016] FIG. 2 is a plan view of the exemplary LCD of the FIG. 1 embodiment;

[0017] FIG. 3 is a front view of an exemplary integral heater layer;

[0018] FIG. 4 is a plan view of another exemplary integral heater layer;

[0019] FIG. 5 is a cross-sectional, left-side view of an exemplary LCD panel display;

[0020] FIG. 6 is a left-side plan view of an exemplary LCD panel display;

[0021] FIG. 7 illustrates exemplary logic according to a preferred embodiment of the present invention; and

[0022] FIG. 8 also illustrates exemplary logic according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)

[0023] Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, specific details such as detailed configuration and components are merely provided to assist the overall understanding of these embodiments of the present invention. Therefore, it should be apparent to those skilled in the art that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the present invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0024] Embodiments of the invention are described herein with reference to illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing.

[0025] Referring now to FIG. 1, a front portion 10A of an exemplary LCD 10 is shown. The LCD 10 may comprise a housing 12 and a panel portion 14. The panel portion 14 may comprise an edge region 15 and a center 20. The housing 12 of LCD 10 may further comprise supports 16. A thermometer 18 is shown to demonstrate that the LCD 10 may operate at any number of temperatures, including temperatures below 0° C., or even significantly below 0° C. It will be understood by one of ordinary skill in the art that any number of shapes and/or sizes of LCDs and any number of different LCD housing configurations may be employed without departing from the scope of the present invention.

[0026] FIG. 2 shows an interior region 38 of the exemplary LCD 10 of the FIG. 1 embodiment, where various components of the LCD 10 are shown positioned within the housing 12. A power source circuit board 32 may distribute electric power from a power source (not shown) to the various other components positioned within the housing 12. An application circuit board 30 may function as an interface for an external device, and may further be linked to a central circuit board 26 by one or more flexible printed circuits 36. The central circuit board 26 may be configured to have at least one control unit 24 mounted thereto, wherein the control unit 24 may comprise a processor, microprocessor, FPGA, or the like. The at least one control unit 24 may be in electronic communication with one or more thermistors 22 or other suitable temperature sensors, such as, by way of illustration and not limitation, electronic wiring 28. Furthermore, source circuit boards 34 may be positioned within the housing 12. In certain embodiments, the source circuit boards 34 may control at least one TFT, and may be linked by one or more flexible printed circuits 36 to the central circuit board 26. The plurality of circuit boards 26, 30, 32, 34, and 36 may be mounted on a back surface of a rear frame (not shown) of the panel portion 14.

[0027] Referring now to FIG. 3, an exemplary integral heater layer 40 is shown. The integral heater layer 40 may comprise current injector sections 46 where current may be injected into a film or grid of conductive material 42 to heat objects, surfaces or material, including by way of example and not limitation, liquid crystal material, in thermal communication with the conductive material 42. One or more wires 48 may direct power from a power source (not shown) to a power input 45 of the integral heater layer 40.

[0028] It will be understood by those of ordinary skill in the art that any number of different heating elements in electronic communication with at least one control unit may be employed without departing from the scope of the present invention. By way of example and not limitation, FIG. 4 illustrates another exemplary integral heater layer 50. This particular integral heater layer 50 comprises a grid of conductive material 51. The integral heater layer 50 may comprise a plurality of horizontal 52 and vertical 54 controlled-resistance heater conductors or lines that direct current through the layer 50. The integral heater layer 50 may also include selective discontinuities 56, transistors 58, and sub-pixel apertures 60.

[0029] FIG. 5 illustrates a side, cross-sectional view of the exemplary panel portion 14 of the FIG. 1 embodiment comprising an integral heater layer 40. The panel portion 14 may further comprise a number of other layers contributing to LCD visual display, including by way of example and not limitation, a front plate 62, black mask 64, TFT array 66, TFT plate 68, color filter plate 70, rear polarizer 71, liquid crystal material 72, and sealing adhesive 74, which may extend around the periphery of the plates maintaining the liquid crystal material 72 to prevent damage to or displacement of the material 72. FIG. 6 illustrates a plan view of the exemplary panel portion 14 wherein the panel portion 14 includes an integral heater layer 40, TFT plate 68, color filter plate 70, rear polarizer 71, liquid crystal material 72, anti-reflective coating 76, front polarizer 78, a first 80A and second 80B pressure sensitive adhesive layer, and a first 82A and second 82B index matching dielectric layer.

[0030] Referring now to FIG. 7, exemplary logic 84 of a preferred embodiment of the present invention is shown. In this particular embodiment, a suitable device for measuring display temperature measures the temperature of glass at or near the edge of an LCD panel portion. The temperature measuring device may be in electronic communication with a heater control unit of a temperature regulation framework. The temperature regulation framework may comprise firmware etched into a central control unit, the firmware linked to a digital analog converter (DAC) or heater control, heat input (Qc) look up table (QC LUT), and center temperature calculator. The temperature regulation framework may be in electronic communication with a heating element, such as, by way of example and not limitation, an integral heater layer. The temperature regulation framework may further be in electronic communication with one or more databases. By way of example and not limitation, one or more databases may provide the DAC information about the heating element to permit the DAC to communicate to the temperature regulation framework a digital analog converter value for that particular heating element (DAC.sub.h). In other embodiments, the DAC may communicate directly with the heating element to regulate temperature of the display, wherein firmware etched into the control unit may control or set the DAC.sub.h value which is provided to the QC LUT, and/or a heating element value may be measured by the control unit and provided to the QC LUT, permitting a steady state temperature delta to be determined based on the DAC.sub.h value and/or heating element value.

[0031] The suitable device for measuring display temperature may electronically communicate one or more glass edge temperature measurements to the control unit. The DAC may communicate the DAC.sub.h to the QC LUT in order for the temperature regulation framework to determine a steady state temperature delta (ΔT.sub.(r)) between a center glass temperature (T.sub.c) and an edge glass temperature (T.sub.(edge)) for a given DAC.sub.h. The center temperature calculator may calculate T.sub.(edge)+ΔT.sub.(r) to determine T.sub.c. The T.sub.c value may be communicated to the heater control, where the heater control may direct the heating element to adjust heating to the LCD based on whether the T.sub.c falls outside the temperature threshold. In particular, the DAC setting may increment or decrement temperature by a value of 1: When the T.sub.c value is greater than the temperature threshold, the DAC may communicate a decrement of 1 (−−) to the heating element. When the T.sub.c value is less than the temperature threshold, the DAC may communicate an increment of 1 (++) to the heating element. When the T.sub.c value meets the temperature threshold, the DAC may communicate to the heating element that no change in output is to be made. The glass edge temperature may continuously be measured and fed back into the temperature regulation framework for continuous control over display temperature.

[0032] FIG. 8 further illustrates exemplary logic according to a preferred embodiment of the present invention. In this particular embodiment, the LCD assembly 10 having a housing 12 comprises at least one thermistor 22, a control unit or temperature regulator 86, and an integral heating layer 40. The ambient air 18 temperature (T.sub.(aa)) may be equal to or below 0° C. The at least one thermistor 22 may measure the temperature of one or more LCD panels 90 at or near the edge of the LCD 10. The thermistor 22 may electronically communicate to the temperature regulator 86 the T.sub.(edge). The temperature regulator 86 may comprise a processor, microprocessor, FPGA, or the like. The temperature regulator 86 may further comprise a DAC and firmware providing a DAC.sub.h to an external DAC device controlling heater hardware circuitry (not shown), wherein the heater hardware circuitry may control the heating element 40. The temperature regulator 86 may further comprise a QC LUT and center temperature calculator. The temperature regulator 86 may electronically communicate with the integral heater layer 40 to achieve a desired LCD temperature. A power supply 88 may provide power to each of the thermistor 22, control unit/temperature regulator 86, and integral heater layer 40.

[0033] The control unit or temperature regulator 86 may communicate DAC.sub.h to the QC LUT in order for the control unit to determine a steady state temperature delta (ΔT.sub.(r)), which is a function of DAC.sub.h (ΔT.sub.(r)=f(DAC.sub.h)). The ΔT.sub.(r) value may account for variance between a center glass temperature (T.sub.c) and an edge glass temperature (T.sub.(edge)) for a given DAC.sub.h. The center temperature calculator may calculate the sum of T.sub.(edge) and ΔT.sub.(r) to determine T.sub.c. The T.sub.c value may be communicated to the heater control, where the heater control may direct the heating element to adjust heating to the LCD based on whether the T.sub.c falls outside of the temperature threshold.

[0034] Any embodiment of the present invention may include any of the features of the other embodiments of the present invention. The exemplary embodiments herein disclosed are not intended to be exhaustive or to unnecessarily limit the scope of the invention. The exemplary embodiments were chosen and described in order to explain the principles of the present invention so that others skilled in the art may practice the invention. Having shown and described exemplary embodiments of the present invention, those skilled in the art will realize that many variations and modifications may be made to the described invention. Many of those variations and modifications will provide the same result and fall within the spirit of the claimed invention. It is the intention, therefore, to limit the invention only as indicated by the scope of the claims.

[0035] Certain operations described herein may be performed by one or more electronic devices. Each electronic device may comprise one or more processors, electronic storage devices, executable software instructions, and the like configured to perform the operations described herein. The electronic devices may be general purpose computers or specialized computing devices. The electronic devices may comprise personal computers, smartphone, tablets, databases, servers, or the like. The electronic connections and transmissions described herein may be accomplished by wired or wireless means. The computerized hardware, software, components, systems, steps, methods, and/or processes described herein may serve to improve the speed of the computerized hardware, software, systems, steps, methods, and/or processes described herein.