JP2000028988A - LCD projector - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To make the luminance of an image projected on a screen constant until the end of the life of a light source lamp. SOLUTION: Behind a dichroic mirror 45,
A light receiving sensor 6 for detecting the leakage light amount (transmitted light) is provided, the light amount of the discharge lamp 3 is estimated from the detected value, and the estimated value is compared with the appropriate light amount data, so that the discharge lamp 3 maintains the appropriate light amount. As described above, by providing the microcomputer 7 that controls the lamp driving unit 4 to vary the lamp power,
The brightness of the image projected on the screen 52 can be kept constant until the end of the lamp life. The discharge lamp 3
By setting the initial power value of the lamp to be equal to or less than the rated value, the burden on the initial stage of the lamp life can be reduced and the lamp life can be extended as much as possible. Further, by setting the power limit of the discharge lamp 3, the discharge lamp 3 can be driven at the power limit or less without exceeding the power that can be supplied at the end of the lamp life.

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, and more particularly to a liquid crystal projector in which the brightness of a projected image is kept constant until the end of a lamp life.

[0002]

2. Description of the Related Art In recent years, with the development of multimedia, the importance of large-screen video display devices for accurately transmitting video and text information has been increasing. So far the video display device is C
Although a large screen, high definition and high image quality have been realized by using an RT (cathode ray tube), a liquid crystal panel (hereinafter referred to as L) using a liquid crystal display element (LCD) as a thin and lightweight video display device.
A liquid crystal projector device for enlarging and projecting an image of a CD panel onto a screen has attracted attention.

FIG. 4 shows a principle diagram of an illumination optical system in such a general liquid crystal projector. The liquid crystal projector using the illumination optical system shown in FIG. 4 is a single-panel LCD type liquid crystal projector using one LCD panel having front and rear polarizing plates. The LCD panel includes a microlens (for example, a lens formed by injecting a lens member into a plurality of holes provided in a glass plate) via a counter substrate (not shown) for each pixel of a liquid crystal display element (LCD). ) And changing the light condensing position of the microlens (the incident angle of the three primary colors with respect to the microlens) enables color display without using a color filter.

In FIG. 4, an illumination optical system 40 in the liquid crystal projector device condenses light emitted from a discharge lamp 41 as a light source lamp by, for example, a reflector 42, converts the light into a point light source by a rod lens 43, and forms a condenser lens. After increasing the parallelism at 44, the dichroic mirror 4
5, the color is separated into R (red), G (green), and B (blue), and the polarization direction is restricted by the first polarizer 46.
The three primary colors R, G, and B are respectively displaced by an arbitrary minute angle, condensed, and radiated to the LCD panel 48. And the second
The polarizing plate 49 restricts only the arbitrary polarization direction of the image light passing through the LCD panel 48, and takes in the image light of the LCD panel 48 into the projection lens 51 via the field lens 50. The projection lens 51 functions as a liquid crystal projector by projecting the image light onto a screen 52 in an enlarged manner.

In such a conventional liquid crystal projector, the power consumption of a discharge lamp used as a light source is kept constant at a rated value and used until the end of its life. Therefore, the brightness of the image projected on the screen depends on the life of the lamp, and the brightness (brightness) of the projected image differs every time the discharge lamp is turned on. The brightness of the image decreases, and eventually the light turns off. The viewer decreases the brightness (darkness) of the projected image until it is turned off.
Had a problem of discomfort.

Further, in order to eliminate the decrease in brightness (darkness) of the projected image, the brightness (brightness) of the projected image is adjusted by LC.
Although the driving control unit (not shown) of the D panel performed the operation, sufficient luminance (brightness) could not be obtained at the end of the lamp life by the luminance adjustment of the driving control unit.

[0007]

As described above, the discharge lamp of the conventional liquid crystal projector has been used until the end of the life of the lamp with a constant power consumption at the rated value. Therefore, the brightness (brightness) of the projected image on the screen is high. There was a problem that it gradually fell and became dark and unpleasant. Further, even if the brightness is adjusted by the drive control unit of the LCD panel in order to solve this problem, sufficient brightness (brightness) cannot be obtained in the projected image at the end of the lamp life.

In view of the above problems, an object of the present invention is to provide a liquid crystal projector capable of keeping the brightness of an image projected on a screen constant until the end of lamp life of a light source lamp. .

[0009]

According to a first aspect of the present invention, there is provided a liquid crystal projector apparatus for projecting an image, irradiating the liquid crystal panel with light, and projecting the image of the liquid crystal panel onto a screen. A light source lamp; a lamp driving unit for supplying lamp power for driving the light source lamp; and a light source for irradiating the liquid crystal panel with light emitted from the light source lamp condensed and color-separated to project an image of the liquid crystal panel An optical element group to be supplied to a lens, a light-receiving sensor provided outside an irradiation range between the light source lamp and the liquid crystal panel, and detecting a light leakage amount of the optical element group; and a light source based on a detection value of the light-receiving sensor. The light amount of the lamp is estimated, and the estimated value is compared with preset appropriate light amount data, so that the light source lamp maintains the appropriate light amount and the brightness of the image projected on the screen becomes constant. In this way, the lamp driving unit is controlled, and in the early stage of the life of the light source lamp, the initial power value of the light source lamp is set to be equal to or less than the rated value in advance, thereby reducing the initial load on the lamp life and reducing the lamp life. And a control unit that can be extended.

According to the first aspect of the present invention, a light receiving sensor for detecting the amount of leakage of the optical element group is provided outside the irradiation range between the light source lamp and the liquid crystal panel, and the light source is detected based on the detection value of the light receiving sensor. The light amount of the lamp is estimated, the estimated value is compared with a predetermined appropriate light amount data, and the lamp power is varied by controlling the lamp driving unit so that the light source lamp maintains the appropriate light amount, and the light is projected on the screen. By providing a control unit for keeping the brightness of the video image constant, the brightness of the video image projected on the screen can be kept constant until the end of the lamp life. In addition, by setting the initial power value of the light source lamp to a value equal to or less than the rated value in advance, the burden on the light source lamp at the beginning of its life can be reduced and the lamp life can be prolonged. As a result, a liquid crystal projector device that can extend the lamp life as much as possible can be realized.

According to a second aspect of the present invention, in the liquid crystal projector device according to the first aspect, the control unit sets a limit power of the light source lamp so that the light source lamp can be turned on at the limit power or less. It is characterized by the following.

According to the second aspect of the present invention, in the control section for controlling the lamp driving section, the power limit of the light source lamp is set so that the lamp light quantity is kept constant at the end of the lamp life of the light source lamp. Although the lamp power is increased as much as possible, the power supply is limited, so that the light source lamp can be driven at a power lower than the limit power.

According to a third aspect of the present invention, in the liquid crystal projector device according to the first aspect, the optical element group transmits or reflects substantially parallel light in an arbitrary wavelength range so as to emit red, green, and blue light. An illumination optical system including a dichroic mirror that separates light in a range and irradiates the liquid crystal panel with the light is configured. The light receiving sensor is provided behind the dichroic mirror to detect the amount of leakage light from the dichroic mirror. It is characterized by the following.

According to the third aspect of the invention, in the liquid crystal projector according to the present invention, the light receiving sensor is provided on the rear side of the dichroic mirror (part of the optical element group between the discharge lamp and the liquid crystal panel). Out of the irradiation range) and the amount of light leaked from the dichroic mirror (transmitted light)
Is detected, and the lamp power of the light source lamp is automatically adjusted in accordance with the detected value, thereby realizing a liquid crystal projector device that keeps the brightness of the image projected on the screen constant until the end of the lamp life.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a liquid crystal projector according to an embodiment of the present invention. FIG.
The same reference numerals in FIG. 4 denote the same parts in FIG.

In FIG. 1, a liquid crystal projector 1
Is composed of an LCD panel 2, a discharge lamp 3 as a light source lamp, a lamp driving unit 4, an optical element group 5, a light receiving sensor 6, and a microcomputer 7 as a control unit. ing. LCD panel 2
Project video. The discharge lamp 3 irradiates light to the LCD panel 2 and projects an image of the LCD panel 2 onto a screen 52. The lamp driving section 4 supplies lamp power for driving the discharge lamp 3. The optical element group 5 collects and separates the irradiation light of the discharge lamp 3 and irradiates the light to the LCD panel 2, and supplies the image of the LCD panel 2 to the projection lens 51. The light receiving sensor 6 is provided outside the irradiation range between the discharge lamp 3 and the LCD panel 2 and detects the amount of leaked light from the optical element group 5. The microcomputer 7 as a control unit estimates the light amount of the discharge lamp 3 from the detected value of the light receiving sensor 6, compares the estimated value with preset appropriate light amount data, and holds the appropriate amount of light. The lamp driving unit 4 is controlled so that the brightness of the image projected on the screen 52 is constant.
By setting the initial value of the power to be equal to or less than the rated value, the load at the beginning of the lamp life is reduced so that the lamp life can be extended.

The optical element group 5 includes optical elements such as an optical lens and an optical mirror, for example, a reflector 42 and a rod lens 4.
3, condenser lens 44, dichroic mirror 4
5, a first polarizing plate 46, a second polarizing plate 49, a micro lens 47, and a field lens 50. The irradiation light from the discharge lamp 3 is condensed and color-separated, and is irradiated to the LCD panel 2. The image on the LCD panel 2 is supplied to the projection lens 51. The operation of the optical element group 5 is the same as that described with reference to FIG.
The color-separated light is emitted to the LCD panel 2, and the image projected on the LCD panel 2 is supplied to the projection lens 51.

The light receiving sensor 6 is provided behind the dichroic mirror 45, which is a part of the optical element group 5, outside the irradiation range between the discharge lamp 3 and the LCD panel 2 by using, for example, a photodiode. The amount of leakage light (transmitted light) of the dichroic mirror 45 is detected, the detected value is converted into a voltage value, and output to the microcomputer 7 as a control unit.

Next, the operation of each circuit will be described.

The LCD panel 2 is composed of liquid crystal display elements arranged in a matrix. A liquid crystal drive control unit (not shown) supplies video signals from a video processing unit (not shown) to each pixel constituting the display element via electrodes. And LC
The entire D panel 2 displays an image based on the supplied image signal.

As the light source lamp, for example, a discharge lamp 3
And discharges and lights a metal halide lamp using, for example, a metal halide compound as a filling gas, irradiates the light to the LCD panel 2, and projects an image projected on the LCD panel 2 through a projection lens 51 to a screen 52. Project to In general, the amount of irradiation of the lamp changes in accordance with the input voltage. Therefore, when the lamp voltage of the discharge lamp 3 increases, the amount of irradiation on the screen 52 increases, and the luminance of the image projected on the screen 52 also increases. become.
Accordingly, the microcomputer 7 controls the lamp power by performing the negative feedback control of the lamp driving unit 4 in accordance with the magnitude of the light amount detection voltage of the light receiving sensor 6, thereby preventing the lamp light amount from decreasing at the end of the lamp life. It is possible to make the luminance of the projected image on the screen 52 constant in the above.

Next, the operation of the dichroic mirror 45 and the light receiving sensor 6 when the light receiving sensor 6 detects the amount of leakage light (transmitted light) of the dichroic mirror 45 will be described.

The dichroic mirror 45 has three reflecting surfaces (45a to 45c) as shown in FIG. 1, and is arranged at an angle of about 45 degrees with respect to the light made substantially parallel by the condenser lens 44. Dichroic mirror 4 with slightly changing angle before and after 45b
5a and 45c are provided, and substantially parallel light irradiated on the reflection surface of each mirror is transmitted or reflected in an arbitrary wavelength range, and is color-separated into light at an equal angle. That is, by utilizing the characteristic of reflecting light of a certain color and transmitting all light of the other colors, it is possible to perform color separation for incident light according to the wavelength reflection characteristic. For example, the light in the wavelength range of R (red) is used as the dichroic mirror 45a, and the dichroic mirror 45
Light in the wavelength range of G (green) is radiated as b, and light that selectively reflects light in the wavelength range of B (blue) as the outer dichroic mirror 45c is irradiated with substantially parallel light from the condenser lens 44 in the above-described arrangement. Then, light in a wavelength range other than the three primary colors RGB is transmitted through the dichroic mirrors 45a to 45c.

Light receiving sensor 6 according to an embodiment of the present invention
Is provided on the rear side of the dichroic mirror 45, detects transmitted light (light in a wavelength range other than the three primary colors) from the dichroic mirror 45 as a leak light amount, and converts the detected value into a voltage value. Output to the microcomputer 7 which is a control unit.

The microcomputer 7 estimates the current light amount of the discharge lamp 3 from the detection value (voltage value) of the light receiving sensor 6 and compares the estimated value with preset appropriate light amount data. A control signal for maintaining an appropriate amount of light is output to the lamp driving unit 4.

The microcomputer 7 sets an initial power value (an initial power value) of the discharge lamp 3 to a rated value or less.
The lamp driving unit 4 is controlled so as to reduce the burden on the discharge lamp 3 at the beginning of its life and to set the limit power of the discharge lamp 3 so that the discharge lamp 3 can be turned on at the limit power or less.

The lamp driving section 4 supplies lamp power for driving the discharge lamp 3 based on a control signal from the microcomputer 7. In addition, the initial value of the power of the discharge lamp 3 is supplied at a rated value or less to extend the life, and furthermore, by driving the discharge lamp 3 with power less than the limit power, the supply power at the end of the life exceeds the limit. Don't overdo it.

As described above, the amount of leaked light (transmitted light) of the dichroic mirror 45 is detected by the light receiving sensor 6 provided behind the dichroic mirror 45 between the discharge lamp 3 and the LCD panel 2. The current light amount of the discharge lamp 3 is estimated according to the detected value, and the estimated value is compared with the appropriate light amount data to control the lamp driving unit 4 so that the discharge lamp 3 maintains the appropriate light amount so that the lamp light amount is constant. The lamp power is automatically varied so that

Next, the operation of the embodiment of the present invention will be described with reference to FIGS. 2 and 3 are explanatory diagrams showing the operation of the embodiment of the invention shown in FIG. 1. FIG. 2 shows a change in lamp power with respect to the lighting time of the discharge lamp 3 by a conventional liquid crystal projector (not shown). FIG. 3 is a diagram showing a comparison between the change in the lamp power and a change in the brightness of the projection image with respect to the lighting time of the discharge lamp 3 and the change in the brightness of the projection image by a conventional liquid crystal projector (not shown). ing.

First, the change in lamp power will be described with reference to FIG.

Referring to FIG. 2, a lamp driving section (not shown) of the conventional liquid crystal projector apparatus continuously supplies a lamp power having a constant rated value from the beginning of the lamp life to the lamp life (non-lighting).

On the other hand, in the liquid crystal projector 1 of the present invention, the lamp driving unit 4 is controlled by the microcomputer 7 to set the initial power value of the discharge lamp 3 to be less than the rated value of the discharge lamp 3. In the early to middle life of the lamp, the lamp power according to the present invention is slightly lower than the conventional lamp power, but the load on the discharge lamp 3 is reduced correspondingly, and the life can be extended.

In the early to middle stages of the lamp life, the lamp drive unit 4 is controlled by the above-described control of the microcomputer 7 in accordance with the detection value of the light receiving sensor 6 so that an appropriate lamp light amount can be obtained. The lamp driving unit 4 supplies a substantially constant lamp power until the end of the lamp life.

At the end of the lamp life, the discharge lamp 3
In order for the brightness of the projected image to start to decrease due to the decrease in the light amount of the light, the light receiving sensor 6 is controlled by the microcomputer 7 described above.
The lamp driving unit 4 increases the lamp power in accordance with the detected value of, but since the power limit has been set in advance, the lamp driving unit 4 raises the lamp power to the set power limit, and thereafter, the lamp life (improper). Until it lights up).

The overall lamp life can be extended by setting the initial value of the power of the discharge lamp 3 to a value equal to or less than the rated value, while the lamp power is supplied by feedback control accompanying a decrease in the amount of light at the end of the life. End of lamp life (lamp deterioration period) in order to compensate for insufficient light quantity by increasing (overload)
, The life of the lamp tends to be shortened, but the overall life of the lamp can be the same as that of the conventional lamp.

Next, a change in the luminance of the projected image will be described with reference to FIG.

In FIG. 3, since the lamp power is controlled by the lamp driving unit 4 until the end of the lamp life so that the luminance is constant, the brightness of the projected image from the early to the middle of the lamp life is the same as that of the conventional discharge lamp 41. The luminance at the beginning of the lamp life is slightly lower than the luminance of the projected image, but remains stable and constant until the end of the lamp life.

The luminance of the projected image from the end of the lamp life to the lamp life (non-lighting) is maintained almost constant until immediately before the lamp life, falls rapidly just before the lamp life, and finally falls shortly. 3 is not lit.

For this reason, when compared with a conventional liquid crystal projector (not shown) in which the brightness of the projected image gradually decreases from the end of the lamp life, the liquid crystal projector 1 according to the embodiment of the present invention has a dark feeling at the end of the lamp life. , The luminance of the projected image can be kept constant from the early stage of the lamp life to just before the lamp life.

In the above-described embodiment, the light receiving sensor for detecting the amount of leakage light of the optical element group is provided outside the irradiation range between the discharge lamp and the LCD panel by the dichroic mirror which is a part of the optical element group. It is provided on the rear side to detect the amount of leaked light (transmitted light) of the dichroic mirror, but the present invention is not limited to this, and the discharge lamp and the LC
The light receiving sensor may be provided anywhere outside the irradiation range with the D panel. In short, it can detect the amount of light,
If it is provided in a place that does not become a shadow of the image projected on the screen, it may be provided anywhere to receive the light.

In the embodiment described above, the LCD
Although a liquid crystal projector device having an LCD single-panel type illumination optical system using one panel has been described, the present invention is not limited to this. The present invention may be applied to a liquid crystal projector having an illumination optical system such as a three-panel LCD system.

Further, in the above-described embodiment, the lamp power is automatically varied so that the lamp light amount becomes constant according to the detection value of the light receiving sensor. However, the present invention is not limited to this. For example, since the lamp current is almost proportional to the lamp light amount, the lamp current flowing through the light source lamp is detected, and the detected current value is fed back instead of the detection value of the light receiving sensor, so that the light amount of the light source lamp becomes constant. The lamp current may be automatically varied as described above.

[0043]

As described above, according to the present invention, the lamp power is automatically varied so that the light amount of the light source lamp is constant, and the brightness of the image projected on the screen is changed to the end of the lamp life of the light source lamp. It is possible to realize a liquid crystal projector device that can be kept constant up to the maximum.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining the operation of the liquid crystal projector device in FIG.

FIG. 3 is a diagram showing a change in luminance of a projection image in FIG. 2;

FIG. 4 is a diagram illustrating the principle of an illumination optical system in a conventional liquid crystal projector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal projector apparatus 2 ... LCD panel (liquid crystal panel) 3 ... Discharge lamp (light source lamp) 4 ... Lamp drive part 5 ... Optical element group 6 ... Light receiving sensor 7 ... Microcomputer (control part)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05B 37/02 H05B 37/02 D 5C060 41/16 41/16 Z F Term (Reference) 2H088 EA12 HA13 HA24 HA28 MA04 2H093 NC25 NC42 NC49 NC50 NC56 ND09 ND47 NE06 NG02 3K073 AA41 AA43 AA87 BA09 BA26 CF13 CF18 CG01 CG02 CG06 CJ16 CJ19 CJ22 3K082 AA00 AA35 BD04 BD13 BD26 BD31 BE00 BE02 CA33 5C058 AA06 BA05 EA12 HC06 BC05 EA12 HC06

Claims (3)

[Claims] A liquid crystal panel for projecting an image; a light source lamp for irradiating the liquid crystal panel with light to project an image on the liquid crystal panel onto a screen; and supplying lamp power for driving the light source lamp. A lamp driving unit, an optical element group that collects and separates the irradiation light of the light source lamp and irradiates the liquid crystal panel with the light, and supplies an image of the liquid crystal panel to a projection lens; and the light source lamp and the liquid crystal panel. A light-receiving sensor that is provided outside the irradiation range and detects the amount of light leaking from the optical element group; estimating the light amount of the light source lamp from the detection value of the light-receiving sensor; Comparing the data with the data, controlling the lamp driving unit so that the light source lamp holds an appropriate amount of light and the luminance of an image projected on a screen is constant. A liquid crystal display, comprising: a control unit for setting a power initial value of the light source lamp to be equal to or less than a rated value in advance at an early stage of the life, thereby reducing a load at an early stage of the lamp life and extending a lamp life. Projector device. 2. The liquid crystal projector according to claim 1, wherein the control unit sets a limit power of the light source lamp, and enables the light source lamp to be turned on at the limit power or less. 3. The dichroic mirror according to claim 1, wherein the optical element group transmits or reflects substantially parallel light in an arbitrary wavelength range, separates light in red, green, and blue wavelength ranges and irradiates the liquid crystal panel with the dichroic mirror. 2. The liquid crystal projector device according to claim 1, wherein the light receiving sensor is provided behind the dichroic mirror to detect the amount of leakage light from the dichroic mirror.