JPH11305203A - Liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal projector using a liquid crystal display(LCD) part with a heater function for equalizing the temperature of the center part of the LCD part and that of its peripheral part. SOLUTION: A picture display device for equally converging light flux from a light source such as a metal halide lamp by a converging optical system 2, spectrally dividing the converged light flux by a diachroic mirror or the like having spectral characteristics of red(R), green(G) and blue(B), optically modulating a picture signal by an optical valve control means such as an LCD panel 4a for each color, synthesizing respective optically modulated colors by a dichroic prism or the like and projecting an enlarged image on a screen by a projecting optical system is constituted of a fitting plate 4b for fixing an LCD 4g, a heater 4d fixed to the LCD fitting surface of the fitting plate 4b or the LCD peripheral part of the rear face of the plate 4b and a heater control part for controlling the heating of the heater 4d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector for correcting color unevenness due to non-uniform temperature distribution, and more particularly to a means for correcting non-uniform temperature distribution of an LCD.

[0002]

2. Description of the Related Art In a liquid crystal projector, output light from a light source is condensed by a condensing optical system, light is modulated by an LCD having a light modulation function that is converted and driven by an input image signal, and is enlarged and output by a projection optical system. The projected image is displayed and output on the screen. The light modulation function of the LCD is based on the V of the liquid crystal panel shown in FIG.
As shown in the -T characteristic (electrode potential-light transmittance) diagram,
By applying an electric potential between the transparent electrodes disposed so as to sandwich the liquid crystal, the axial direction of the liquid crystal is controlled to change the transmittance. In this VT characteristic, the transmittance operating point changes significantly depending on the temperature. For example, when the temperature of the liquid crystal changes from 40 ° C. to 70 ° C., the relative value of the gray level reaches about 20%. In addition, a temperature difference of 5 ° C. or more is generated between the central portion and the peripheral portion of the LCD where the strong light beam strikes. Further, since a temperature difference occurs between the G color having a relatively large amount of light and the other R and B colors, the color balance is lost due to uneven transmittance of each color. In the case of a luminance component such as white, the transmittance unevenness (= luminance unevenness) is not so noticeable. On the other hand, display of a subtle hue such as a flesh color has a problem that partial transmittance unevenness (= color unevenness) is easily noticeable.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a liquid crystal projector using an LCD with a heater function in order to equalize the temperature between the center and the periphery of the LCD. And

[0004]

A light beam from a light source such as a metal halide lamp is evenly condensed by a condensing optical system.
The light is separated by a dichroic mirror having spectral characteristics such as (red) G (green) and B (blue), and light-modulated by an image signal by a light valve control unit such as an LCD (liquid crystal display panel) for each color, and light-modulated. In an image display device that synthesizes each color by a dichroic prism or the like and enlarges and projects an image on a screen by a projection optical system, a mounting plate to which an LCD is fixed, and an LCD on the mounting surface or the back surface of the LCD of the mounting plate
It comprises a heater fixed to the periphery and a heater control unit for controlling the heat generation of the heater.

[0005] Further, the heater is a heater plate fixed to the surface of the mounting plate by a fixing means such as affixing or screwing, and a thick film heating element having a heat generating thick film printed on the surface of the mounting plate. A thin film heating element in which a metal thin film is deposited on the surface of the mounting plate, or a heating element such as a semiconductor fixed to the surface of the mounting plate.

Further, the heat generation of the heater is controlled by separately installing a temperature detection sensor on a mounting plate for each of the RGB colors, which individually controls the heaters for each of the R, G, and B colors, based on the temperature data detected by the temperature detection sensor. To individually control heaters based on R
A temperature detection sensor is additionally installed on the mounting plate for each color of GB, and the temperature of the other mounting plate is controlled to be relatively equal to the temperature of the highest mounting plate.

The temperature sensor may be a thermistor fixed to the surface of the mounting plate, a thermoelectric element such as a thermocouple fixed to the surface of the mounting plate, or a transistor fixed to the surface of the mounting plate. Heat conversion semiconductor device.

[0008]

FIG. 1 is a conceptual diagram of an embodiment of a liquid crystal projector according to the present invention. FIG. 2 is a perspective view of an LCD unit with a heater according to the present invention. A light beam from a light source 1 such as a metal halide lamp is condensed by a condensing optical system 2 into L light of each color.
The light is focused on the incident light surface of the CD. The incident light for each color is optically modulated by the output signal of the signal processing unit 3 by the LCD unit 4 and is enlarged and projected as an image on the screen 6 by the projection optical system 5.

The image processing section 3a converts the input image signal S into image data and performs image processing such as image quality and gradation. The image driver 3b generates display image data from the output image data, and drives the LCD 4a for display. The synchronization separation unit 3c and PLL (Phase Locked Loop) 3d are H (horizontal pulse), V (vertical pulse), and CLK synchronized with the input image signal.
(Clock pulse), and a scanning drive unit (not shown) scans and drives the LCD 4a.

The LCD 4a is fixed to a mounting plate 4b having an opening for transmitting a light beam and a mounting hole 4f to a housing by fixing means such as sticking and screwing. A heater 4d is formed on the back side of the LCD mounting surface of the mounting plate 4b and around the LCD. Further, a temperature sensor 4g is L on the LCD mounting surface.
It is fixed in close contact with the CD 4a. LCD4a
Is performed through the flexible cable 4c.

[0011] The role of the heater 4d is L
Since a difference in light transmittance occurs due to a temperature difference between the DC central portion and the peripheral portion, the peripheral portion is heated by an auxiliary heater to suppress the temperature difference. Further, the thermal energy of the light incident on the LCD of each of the RGB colors is different, and the highest G color and the B color have a ratio of 80: 5, and a temperature difference occurs between the LCDs. On the other hand, since the change rate (gamma characteristic) of the light transmittance of the LCD with respect to the drive voltage has almost no temperature dependence (see FIG. 3), the setting of the LCD drive voltage of the black level is changed for each color to cope with this. doing. However, there is a problem that the assumed temperature difference does not occur at the time of startup such as immediately after power-on. For this purpose, a plurality of temperature sensors 8A each composed of a temperature sensor 4g for each color, and each LCD
And a heater control unit 7 for controlling the temperatures of the R and B LCDs based on the temperature of the G color.

The heater can be controlled by the simplest method of supplying a constant current, the method of changing the supply current value for each color, the method of controlling the supply current based on the temperature detected by the temperature sensor 4g and the temperature detection unit 8, or The method of controlling the temperature of the R and B LCDs 4a based on the temperature of the G color is selected based on cost performance factors.

The heater 4d is fixed on the surface of the mounting plate 4b by a fixing means such as affixing or screwing, and the heating element is coated with a heat-resistant resin or the like. The insulating film and the heating element film are formed on the surface of the mounting plate 4b. A thick-film heating element printed with a thick film, a thin-film heating element in which a thin metal film is deposited on the surface of the mounting plate 4b that has been subjected to insulating film processing, or semiconductor heat generation using the collector loss of a transistor fixed to the surface of the mounting plate 4b. Elements can be selected. Heater terminals 4e for connecting lead wires are provided at both ends of the heater 4d.

The temperature sensor 4g includes a thermistor fixed to the surface of the mounting plate 4b, a thermocouple such as a thermocouple fixed to the surface of the mounting plate 4b, or a thermoelectric element such as a transistor fixed to the surface of the mounting plate 4b. A conversion semiconductor element or the like is selected, and the temperature detector 8 is a detection circuit corresponding to the type of the temperature sensor 4g.

[0015]

The present invention is embodied in the form described above, and has the following effects. It comprises a mounting plate to which the LCD is fixed, a heater fixed to the LCD mounting surface of the mounting plate or the back surface of the LCD, a heater control unit for controlling the heat generation of the heater, and the like. By controlling the temperature of the projection screen and the temperature of the peripheral area to be equal, a liquid crystal projector capable of keeping the color tone of the central area of the projection screen and the peripheral area substantially uniform can be proposed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of one embodiment of a liquid crystal projector according to the present invention.

FIG. 2 is a perspective view of an LCD unit with a heater according to the present invention.

FIG. 3 is an explanatory diagram of VT characteristics (potential between electrodes-light transmittance) of a liquid crystal panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Condensing optical system 3 Signal processing part 4 LCD part 4a LDC 4b Mounting plate 4d Heater 4e Heater terminal 4f Mounting hole 4g Temperature sensor 5 Projection optical system 6 Screen 7 Heater control part 8 Temperature detection part 8A Multiple temperature sensors

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 9/31 H04N 9/31 Z

Claims (11)

[Claims] 1. A light beam from a light source such as a metal halide lamp is evenly condensed by a condensing optical system, and R (red) G (green) B
The light is separated by a dichroic mirror having spectral characteristics such as (blue), and light is modulated by an image signal by light valve control means such as an LCD (liquid crystal display panel) for each color, and each light modulated color is synthesized by a dichroic prism or the like. ,
An image display device for enlarging and projecting an image on a screen by a projection optical system, comprising: a mounting plate for fixing the LCD; and the LCD of the mounting plate.
A heater fixed to the periphery of the LCD on the mounting surface or the back surface thereof, and a heater control unit for controlling heat generation of the heater. The heater controls the temperature of the central portion and the peripheral portion of the LCD to be equal. A liquid crystal projector. 2. The liquid crystal projector according to claim 1, wherein the heater is a heater plate fixed to a surface of the mounting plate by fixing means such as affixing or screwing. 3. The liquid crystal projector according to claim 1, wherein the heater is a thick film heating element formed by printing a heat generating thick film on a surface of the mounting plate. 4. The liquid crystal projector according to claim 1, wherein the heater is a thin film heating element in which a thin metal film is deposited on a surface of the mounting plate. 5. The liquid crystal projector according to claim 1, wherein the heater is a heating element such as a semiconductor fixed to a surface of the mounting plate. 6. The liquid crystal projector according to claim 1, wherein the heat generation of the heater is controlled individually for each of the RGB colors. 7. The heat generation control of the heater, wherein a temperature detection sensor is additionally installed on the mounting plate for each of the RGB colors, and the heaters are individually controlled based on temperature data detected by the temperature detection sensor. The liquid crystal projector according to claim 1, wherein 8. The heat generation of the heater is controlled such that a temperature detection sensor is additionally installed on the mounting plate for each of the RGB colors so that the temperature of the other mounting plate is relatively equal to the highest mounting plate. The liquid crystal projector according to claim 1, wherein: 9. The liquid crystal projector according to claim 1, wherein the temperature sensor is a thermistor fixed to a surface of the mounting plate. 10. The liquid crystal projector according to claim 1, wherein the temperature sensor is a thermoelectric element such as a thermocouple fixed to a surface of the mounting plate. 11. The liquid crystal projector according to claim 1, wherein the temperature sensor is a heat conversion semiconductor element such as a transistor fixed to a surface of the mounting plate.