JP2005227577A - Liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal projector in which fluctuation of color balance among liquid crystal projectors is reduced. <P>SOLUTION: The liquid crystal projector provided with a light source lamp and liquid crystal panels for respective R, G and B colors, is further provided with a light quantity detector to detect light quantity of each of R, G and B colors outputted from the light source lamp and a control means to control driving voltages of the respective liquid crystal panels based on the light quantity values of the respective R, G and B colors detected with the light quantity detector. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal projector.

  FIG. 1 shows the configuration of a conventional liquid crystal projector.

  An optical device 30 is disposed inside a housing 100 made of plywood, metal, synthetic resin, or the like. The optical device 18 will be described.

  As the light source lamp 1, a metal halide lamp, a high-pressure mercury lamp, or the like is used. The light source 1 is driven by a lamp power circuit 22. Three types of liquid crystal panels are provided: a liquid crystal panel 11 for red (R), a liquid crystal panel 14 for green (G), and a liquid crystal panel 17 for blue (B). Each liquid crystal panel 11, 14, 17 is controlled by a video signal. Each of the liquid crystal panels 11, 14, and 17 can change the light transmittance for each pixel. Incident-side polarizing plates 10, 13, 16 are arranged on the incident side of the liquid crystal panels 11, 14, 17, and outgoing-side polarizing plates 12, 15, 18 are arranged on the outgoing side.

  The white light output from the lamp 1 reaches the spectroscope 5 via the infrared / ultraviolet absorption filter 2, the integrator lens 3 and the total reflection mirror 4. As the spectroscope 5, a dichroic mirror having a property that transmittance and reflectance differ depending on the wavelength of light is generally used. The spectroscope 5 has a property of reflecting blue light out of visible light and passing other light. The white light reaching the spectroscope 5 is separated into a blue light beam and other light beams. Light rays other than blue contain a lot of green and red rays of visible light.

  Light rays other than blue light that have passed through the spectroscope 5 reach the spectroscope 7. The spectroscope 7 reflects green light and allows other light to pass through. The light beam that has passed through the spectroscope 7 reaches the total reflection mirror 8.

  The blue light beam reflected by the spectroscope 5 reaches the liquid crystal panel 17 via the total reflection mirror 6. The green light beam reflected by the spectroscope 7 reaches the liquid crystal panel 14. The red light beam reflected by the total reflection mirror 8 reaches the liquid crystal panel 11 via the total reflection mirror 9.

  The video signals modulated into electrical signals by the liquid crystal panels 11, 14, and 17 are converted into optical signals. The light of each color that has passed through each liquid crystal panel 11, 14, 17 is sent to the combiner 19 and is combined into one optical signal. As the synthesizer 19, a dichroic prism is generally used.

  The light synthesized by the synthesizer 19 is enlarged and output by the projection lens 21. By projecting the output light onto the screen 23, the user can visually recognize the video signal on a large screen. The projection lens 21 is held by a holding body 20 fixed to the housing 100.

  In the housing 100, a main power supply circuit 51 and a control circuit 52 that operates with electric power supplied from the main power supply circuit 51 are further provided. In the control circuit 52, a microcomputer 61 and a liquid crystal driving circuit 62 are provided. In addition, the optical device 30, the liquid crystal panels 11, 14, and 17 and a cooling fan 24 that cools the inside of the housing 100 are provided in the housing 100.

  Each of the liquid crystal panels 11, 14, and 17 is driven to form an image by changing the transmittance of the pixels of the liquid crystal panel according to a drive signal from the liquid crystal drive circuit 62. The liquid crystal drive circuit 62 is controlled by the microcomputer 61. The lamp power supply circuit 22 is also controlled by the microcomputer 61.

  In the conventional liquid crystal projector, the color balance of the reproduced image projected on the screen 23 greatly depends on the color balance of the light source when the entire liquid crystal dynamic range is used. Since the color balance of the light source is different among individual light sources, the color balance is also different for each liquid crystal projector.

  The variation in color balance between liquid crystal projectors is less problematic when displaying images using only one liquid crystal projector, but when displaying multiple projection images using multiple liquid crystal projectors. It becomes a big problem. Further, even when an image is displayed using only one liquid crystal projector, it becomes a problem in a usage environment in which color reproducibility is important.

  In general, when the liquid crystal is irradiated with a certain amount of light, the color balance in the halftone from black to white can be adjusted by adjusting the balance of the voltages applied to the liquid crystal. On the other hand, the color balance in the state of 100% white is governed by the color balance of the light source when the entire dynamic range of the liquid crystal is used. Further, the color balance of the liquid crystal projector changes because the color balance of the light source also changes due to the temporal change of the light source.

  An object of the present invention is to provide a liquid crystal projector that can reduce variations in color balance among liquid crystal projectors.

  Another object of the present invention is to provide a liquid crystal projector capable of reducing a change in color balance due to a change in the light source over time.

  According to the first aspect of the present invention, in a liquid crystal projector including a light source lamp and a liquid crystal panel for each of R, G, and B, a light amount detection for detecting the light amount for each of R, G, and B output from the light source lamp. And a liquid crystal projector comprising adjusting means for adjusting the driving voltage of each liquid crystal panel based on the light amounts of R, G, and B detected by the light amount detector.

  According to a second aspect of the present invention, in the first aspect of the present invention, the adjusting means is configured to adjust the light amount ratio for each of R, G, and B based on the light amount for each of R, G, and B detected by the light amount detector. Based on a preset standard light quantity ratio for each of R, G and B of the light source lamp and a light quantity ratio for each of R, G and B calculated by the first means. A second means for calculating an adjustment value for adjusting the driving voltage of the panel, and an adjustment value corresponding to the driving voltage of each liquid crystal panel obtained from the input video signal, thereby multiplying the driving voltage of each liquid crystal panel by A third means for adjusting is provided.

  According to the present invention, variations in color balance among liquid crystal projectors can be reduced.

  In addition, according to the present invention, a change in color balance due to a change in the light source over time can be reduced.

  Embodiments in which the present invention is applied to a liquid crystal projector will be described below with reference to the drawings.

  FIG. 2 shows the configuration of the liquid crystal projector.

  In FIG. 2, the same components as those in FIG.

  On the path from the light source 1 to the total reflection mirror 4, a photosensor 71 capable of detecting the light quantity separately for R, G, and B is disposed. The amount of light for each of R, G, and B detected by the photosensor 71 is given to the microcomputer 61 via the luminance level detection circuit 72.

  By the way, when the dynamic range of the liquid crystal is used 100%, for example, in the all white pattern, the voltages applied to the R, G, B liquid crystal panels 11, 14, 17 have the same value. The transmittances of 14 and 17 are almost the same. For this reason, the white balance is largely governed by the white balance of the light source 1. Since the color balance of the light source 1 changes with time, the amount of light for each of R, G, and B output from the light source 1 also changes with time.

  The present invention pays attention to this point, and when the average light quantity ratio of R, G, B for the light source of the liquid crystal projector is R light quantity: G light quantity: B light quantity = X: Y: Z, the actual liquid crystal When the light quantity ratio for each of R, G, and B detected by the photosensor 71 in the projector is different from X: Y: Z, R and R after passing through the liquid crystal panels 11, 14, and 17 at the time of displaying all white patterns. By adjusting the voltage (input signal value) for driving the liquid crystal panels 11, 14, and 17 so that the light quantity ratio for each of G and B is X: Y: Z, the difference in white balance between individuals is reduced. It is characterized by letting.

  Further, even if the light quantity ratio for each of R, G, and B of the light source 1 changes with time, the light quantity ratio for each of R, G, and B after passing through the liquid crystal panels 11, 14, and 17 when displaying an all white pattern. It is characterized in that the temporal change of white balance is reduced by adjusting the voltage (input signal value) for driving the liquid crystal panels 11, 14, and 17 so that becomes X: Y: Z.

  This will be specifically described below. A standard light amount ratio for each of R, G, and B detected by the photosensor 71 is, for example, 0.8: 1.0: 0.6. When a light source having such a light amount ratio is used as the light source, the signal amplitude ratio for each of R, G, and B input to each liquid crystal panel is R: G: B = 100: 100: 100. Assume that the white balance is adjusted to the optimum white balance.

  Since the liquid crystal panel has a characteristic gamma characteristic, the input amplitude is defined as 100% and the maximum amplitude that can be applied as a voltage between black and white, and is defined as a voltage that can obtain 100% apparent white.

  Here, in an actual liquid crystal projector, the light amount ratio for each of R, G, and B detected by the photosensor 71 due to variations in the light source 1 is, for example, 0.9: 1.0: 0.7. . In order to match the optimum white balance, it is necessary to reduce the ratio of the R illuminance to the G illuminance and the ratio of the B illuminance to the G illuminance. In this case, the input amplitude to the R liquid crystal panel and the B liquid crystal panel is obtained by the following equation (1).

  R amplitude: G amplitude: B amplitude = 100 × 0.8 / 0.9: 100: 100 × 0.6 / 0.7 = 88.9: 100: 85.7 (1)

  Therefore, in the following, the voltage applied to the R liquid crystal panel 11 is controlled to a value of 88.9% of the voltage value obtained from the input video signal, and the voltage applied to the B liquid crystal panel 17 is set to the input video signal. The voltage applied to the B liquid crystal panel 17 is controlled to a value of 85.7% of the voltage value obtained from the input video signal.

  Further, if the light quantity ratio for each of R, G, and B detected by the photosensor 71 is, for example, 0.7: 1.0: 0.6, input to the R liquid crystal panel and the B liquid crystal panel. The amplitude is obtained by the following equation (2).

  R amplitude: G amplitude: B amplitude = 100 × 0.8 / 0.7: 100: 100 × 0.6 / 0.6 = 14.3: 100: 100 (2)

  As shown in the following equation (2), when the amplitude of any of R, G, and B exceeds 100, the maximum amplitude that can be applied as the black-and-white voltage is 100. In addition, each amplitude is converted so that the maximum amplitude becomes 100.

  R amplitude: G amplitude: B amplitude = 114.3 × 100 / 114.3: 100 × 100 / 114.3: 100 × 100 / 114.3 = 100: 87.5: 87.5 (3)

  Therefore, in the following, the voltage applied to the R liquid crystal panel 11 is controlled to 100% of the voltage value obtained from the input video signal, and the voltage applied to the G liquid crystal panel 14 is obtained from the input video signal. The voltage applied to the B liquid crystal panel 17 is controlled to 87.5% of the voltage value obtained from the input video signal.

  Note that the calculation of the adjustment value as described above based on the light quantity ratio for each of R, G, and B detected by the photosensor 71 is performed by first turning on the light source 1 after the liquid crystal projector is turned on. This is performed when the lighting state of 1 is stabilized. Therefore, it is performed every time the liquid crystal projector is turned on.

It is a block diagram which shows the structure of the conventional liquid crystal projector. It is a block diagram which shows the structure of the liquid crystal projector in a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 11, 14, 17 Liquid crystal panel 62 Liquid crystal drive circuit 61 Microcomputer 62 Liquid crystal drive circuit 71 Photo sensor 72 Brightness level detection circuit

Claims (2)

In a liquid crystal projector having a light source lamp and a liquid crystal panel for each of R, G and B,
Based on the light quantity detector for detecting the light quantity for each of R, G, B output from the light source lamp, and the light quantity for each R, G, B detected by the light quantity detector, the drive voltage of each liquid crystal panel is determined. Adjustment means to adjust,
A liquid crystal projector comprising: Adjustment means
A first means for calculating a light amount ratio for each of R, G, and B based on a light amount for each of R, G, and B detected by the light amount detector;
The drive voltage of each liquid crystal panel is adjusted based on a preset standard light amount ratio for each of R, G, and B of the light source lamp and a light amount ratio for each of R, G, and B calculated by the first means. Second means for calculating an adjustment value for the liquid crystal panel, and third means for adjusting the drive voltage of each liquid crystal panel by multiplying the adjustment value corresponding to the drive voltage of each liquid crystal panel obtained from the input video signal,
The liquid crystal projector according to claim 1, further comprising:

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