JP2002258401A - Projection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type liquid crystal display device which has excellent reproducibility of black of video and wide dynamic range, and in which a service life of a light source lamp is long. SOLUTION: The projection type liquid crystal display device which makes the light projected by a light source means 19 incident on liquid crystal light valves 13 to 15 and composites and projects images respectively projected from the image formation surfaces of the liquid crystal light valves on a screen through an optical system 16 is equipped with a control means 17 which finds features of the lightness of the images to be projected and adjusts the quantity of light of the light source means and the contracts of the projected images according to the features.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a projection type liquid crystal display device (liquid crystal projector).

[0002]

2. Description of the Related Art A liquid crystal projector converts light emitted from a light source lamp into R, G, B which functions as a light valve.
Are transmitted through the three liquid crystal panels, and the transmitted light is combined to display a color image. The minimum and maximum luminance values that can be expressed are determined by the brightness of the light source lamp. Although the efficiency of the light source lamp has been improved to save the power of the liquid crystal projector, most of the power consumption of the liquid crystal projector is still the power consumed by the light source lamp.

[0003]

In order to improve the brightness of an image displayed by a liquid crystal projector, it is necessary to increase the output (light amount) of a light source lamp, but the liquid crystal panel has light leakage. Light cannot be completely blocked, and therefore, the minimum luminance value that can be expressed by the liquid crystal projector increases with an increase in the output of the light source lamp, and black floating occurs. Thus, the liquid crystal projector has a CR
Compared with T, there is a problem that the reproducibility of black is poor and the dynamic range is narrow.

Although the life of a light source lamp used in a liquid crystal projector is very short as compared with a CRT, there is a problem that the life is further shortened when the output thereof is increased to increase the brightness of an image.

An object of the present invention is to provide a projection type liquid crystal display device which is excellent in reproducibility of black of an image, has a wide dynamic range, and has a long life of a light source lamp. As an issue.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a liquid crystal light valve, in which light emitted from a light source is incident on a plurality of liquid crystal light valves, and projected images respectively emitted from an image forming surface of the liquid crystal light valve are optically converted. A projection-type liquid crystal display device that performs composite projection on a screen via a system, including a control unit that obtains a brightness characteristic of an image to be projected and adjusts a light amount of the light source unit and a contrast of the projected image according to the characteristic. The problem is solved by a projection-type liquid crystal display device characterized in that:

The control means divides the image to be projected into a plurality of blocks, obtains an average value of the sum of all the average values of the color signal data of each block, and compares the average value with a predetermined value. The feature of the brightness of the image to be projected can be obtained.

[0008] The control means can efficiently suppress the power consumption of the lamp by the characteristic of the brightness of the image to be projected, and can prolong the life of the lamp.

[0009]

FIG. 1 is a block diagram showing the configuration of a projection type liquid crystal display device 25 (hereinafter abbreviated as display device 25) of the present invention. As shown in FIG.
Signal input unit 1, A / D converters 2 to 4, digital signal processing unit 5, image quality improvement processing unit 6, D / A converters 7 to 9, drive circuits 10 to 12, light source lamp 19, liquid crystal panels 13 to 1
5, optical system 16, microcomputer (microcomputer) 1
7 is provided. The operation of the display device 25 will be described below.

An analog video signal is supplied to the signal input unit 1 from a video signal source such as a personal computer (not shown) or a video tape recorder (not shown). The signal input unit 1 converts the video signal into R, G, B color signals s1, s.
2, s3, and sent to A / D converters 2, 3, and 4. The color signals s1, s2, and s3 are digitized by A / D converters 2, 3, and 4, respectively, and sent to a digital signal processing unit 5.

The digital signal processor 5 converts the input color signals s1, s2, s3 into the liquid crystal panel 1 respectively.
Digital signal processing such as pixel conversion, menu display, enlargement / reduction, etc. for adapting to the sizes (number of pixels) of 3, 14, and 15 is performed as necessary, and color signals s4, s5,
It is sent to the image quality improvement processing section 6 as s6.

The image quality improvement processing section 6 includes color signals s4, s5,
Contrast adjustment, brightness adjustment, and gamma correction based on a predetermined gamma curve are individually performed on each of s6 to generate color signals s7, s8, and s9, respectively. As described later, in the present embodiment, the contrast adjustment is performed in conjunction with the output (light amount) of the light source lamp 19.

[0013] R, output from the image quality improvement processing unit 6,
The G and B digital color signals s7, s8 and s9 are D / A
After being converted into analog signals by the converters 7, 8, and 9, respectively, the signals are sent to the drive circuits 10, 11, and 12.

The driving circuits 10, 11, and 12 correct the level of the input analog signal so as to conform to the specification of the liquid crystal panel, and as final R, G, B color signals, the liquid crystal panels 13, 14,. 15 respectively.

The liquid crystal panels 13, 14, and 15 transmit light emitted from the light source lamp 19 at a transmittance corresponding to the level of a signal supplied from the drive circuits 10, 11, and 12, and include an optical system including a mirror, a lens, and the like. It functions as a light valve that transmits the light as a projection image toward the light source 16. Projected images from each liquid crystal panel are synthesized by the optical system 16 and projected on a screen (not shown).

The image data s13 before correction is input from the image quality improvement processing unit 6 to the microcomputer 17. The microcomputer 17 obtains the brightness of the image according to a procedure described later, outputs a signal s12 to the light source lamp 19 in order to instruct a change in the amount of light according to the result, and instructs to change the contrast. The signal s11 is output to the image quality improvement processing unit 6.

Next, the operation of changing the amount of light in the light source lamp 19 and the operation of changing the contrast in the image quality improvement processing section 6 will be described. FIG. 2 is a graph showing a relationship between an input signal level (0 to 100% white) and an output level of the liquid crystal projector. As described above, in the liquid crystal projector, the minimum luminance value is determined by the output (light amount) of the light source, and even if a 0% white signal is input, the brightness cannot be completely set to 0, and a floating black occurs. I do.

For example, the input / output characteristics of the liquid crystal projector are shown by a solid line b in FIG.
From b to bh, if the light amount of the light source is increased by 25%, the input / output characteristic becomes as shown by a broken line a, and the maximum luminance that can be expressed, that is, the maximum luminance value increases to ah. The value also increases to ab, and the degree of floating black increases. Conversely, if the light amount of the light source is reduced by 50%, the minimum luminance value is reduced to cb and the floating of black can be suppressed.
The maximum luminance value also decreases to ch.

Therefore, simply adjusting the light amount of the light source cannot simultaneously improve both the floating black and the dynamic range. In the present embodiment, the following processing is executed to solve this problem.

The microcomputer 17 divides the image into, for example, 64 blocks as shown in FIG. 5 based on the uncorrected image data s13 input from the image quality improvement processing section 6, and calculates the average value of the data for each block. That is, an average value of brightness is obtained. If the image is a dark scene and the average value of the sum of all the average values of the data of each block is calculated, and the value is below a predetermined threshold, the microcomputer 17 sets the light source lamp 19
To send a signal s12 to reduce the light amount of the light source lamp 19.

When the light quantity decreases, as shown in FIG. 3, the input / output characteristics of the display device change from those shown by the solid line b to those shown by the chain line c, and the output level with respect to the input level IN1 changes from OUT1 to OUT2. At this time, the minimum luminance value decreases from bb to cb, and the floating of black is improved.

However, at the same time, the amplitude of the output level decreases and the dynamic range narrows. Since the contrast is thereby reduced, the microcomputer 17 sends the signal s11 to the image quality improvement processing section 6 to improve the contrast. The image quality improvement processing unit 6 has an input / output characteristic equivalent to a broken line c ′.
The correction is applied to the input color signal so as to be as shown by. As a result, the output level changes from OUT2 to OUT3, and the minimum luminance can be reduced without narrowing the dynamic range.

Conversely, if the image is a bright scene, the average value of the sum of all the average values of the data of each block of the image is calculated, and if the average value exceeds a predetermined threshold, the microcomputer 17 sets the light source lamp to A signal s12 is sent to 19 to instruct to increase the light amount. As a result, the input / output characteristics of the display device are changed from the solid line b to the broken line a in FIG.
As a result, the output level corresponding to the input level IN1 becomes O
The state changes from UT1 to OUT2, and the maximum luminance value increases.
However, with this alone, the minimum luminance value also increases from bb to ab, and the degree of floating black increases.

Therefore, the microcomputer 17 controls the image quality improvement processing unit 6.
Instruct to improve the black float. Image quality improvement processing unit 6
Corrects the input color signal so that the input / output characteristics are equivalent to those indicated by the chain line a '. As a result, the output level does not change so much from OUT2 to OUT3, so that the dynamic range of the video can be widened and the floating of black can be suppressed.

In the above embodiment, for example,
If the light source lamp used at a fixed output of 50 W is used at an output of 130 W in a normal scene, the output is reduced to 100 W in a dark scene, and increased to 150 W in a bright scene, the gradation is increased in a dark scene. The minimum luminance value can be reduced without loss, and the black floating characteristic of the liquid crystal projector can be improved. In a bright scene, the dynamic range of an image can be increased while suppressing the floating of black. Therefore, according to the present embodiment, the dynamic range, which is the difference between the minimum luminance and the maximum luminance, can be greatly increased, and the narrow dynamic range, which is a drawback of the liquid crystal projector, can be improved.

Further, by changing the output of the light source lamp conventionally used at a fixed output of 150 W according to the brightness of an image, the power consumption is reduced if the output is used at an average of 130 W. The lamp life can be prolonged accordingly.

[0027]

According to the first aspect of the present invention, the light intensity and contrast of the light source are adjusted in accordance with the characteristics of the brightness of the image. Therefore, in a dark scene, the minimum luminance value is reduced without deteriorating the gradation. In a bright scene, the maximum luminance value can be increased while suppressing the floating of black. This makes it possible to display an image with a small degree of black floating and a wide dynamic range.

According to the second aspect of the present invention, it is possible to easily obtain the brightness characteristic of an image.

According to the third aspect of the present invention, the power consumption of the lamp can be efficiently suppressed by controlling the light source according to the characteristic of the brightness of the image, and the life of the lamp can be extended. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a projection type liquid crystal display device of the present invention.

FIG. 2 is a graph illustrating input / output characteristics of a conventional projection type liquid crystal display device.

FIG. 3 is a graph illustrating input / output characteristics of the projection type liquid crystal display device of the present invention.

FIG. 4 is a graph illustrating input / output characteristics of the projection type liquid crystal display device of the present invention.

FIG. 5 is an explanatory diagram of image division for obtaining a feature of brightness of an image.

[Explanation of symbols]

Reference Signs List 1 signal input unit, 2-4 A / D converter, 5 digital signal processing unit, 6 image quality improvement processing unit, 7-9
D / A converter, 10-12 drive circuit, 13-15
LCD panel, 16 optical system, 17 microcomputer, 1
9 light source lamp, 25 projection type liquid crystal display device.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/34 G09G 3/34 J 5C080 3/36 3/36 H04N 5/74 H04N 5/74 K 9 / 31 9/31 Z F term (reference) 2H088 EA14 EA15 HA28 MA02 MA05 MA20 2H093 NA53 NA62 NC42 ND04 ND08 ND39 ND47 NG02 5C006 AA16 AA22 AC21 AF45 AF69 AF81 AF82 BB11 BC13 EA01 EC11 FA47 FA56 5C058 AA26 EA08 BA04 BB13 BC05 DB00 GB06 HB05 HB24 HD01 JA11 JA17 JB06 5C080 AA10 BB05 CC03 DD03 DD29 EE29 FF09 GG10 GG11 JJ02 JJ04 JJ05 KK43 KK52

Claims (3)

[Claims] 1. A light emitted from a light source means is incident on a plurality of liquid crystal light valve means, and projected images respectively emitted from an image forming surface of the liquid crystal light valve means are combined and projected on a screen via an optical system. A projection-type liquid crystal display device comprising: a control unit that obtains brightness characteristics of an image to be projected and adjusts a light amount of the light source unit and a contrast of the projection image according to the characteristics. Display device. 2. The control means divides an image to be projected into a plurality of blocks, calculates an average value of the sum of all the average values of the color signal data of each block, and compares the average value with a predetermined value. 2. The projection type liquid crystal display device according to claim 1, wherein a characteristic of brightness of an image to be projected is obtained. 3. The projection type projector according to claim 2, wherein the control unit efficiently suppresses power consumption of the lamp by realizing a characteristic of brightness of an image to be projected, and realizes a long life of the lamp. Liquid crystal display.