JP2006343767A - Projection type image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type image display apparatus capable of realizing the improvement of contrast, the reduction of power consumption, and the restraint of black floating on a liquid crystal projector. <P>SOLUTION: An image signal processing circuit 23 inputs an image signal so as to perform processing such as frequency conversion, and also, performs processing to generate data showing average brightness (APL:Average Picture Level) of the image. A microcomputer 25 receives the APL data, controls the emitted light quantity of a light source (lamp), and also, controls the stopping state of a diaphragm mechanism 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a projection display apparatus such as a liquid crystal projector.

Conventionally, a liquid crystal display device (see Patent Document 1) in which the display brightness and contrast are constant even when the average brightness (APL: Average Picture Level) of the video changes, or the average brightness of the video A projection-type image display apparatus has been proposed in which the lamp driving power is lowered when the brightness (APL) is bright, and the contrast is improved by increasing the lamp driving power when dark (see Patent Document 2).
JP-A-8-201812 Japanese Patent Laid-Open No. 3-179886

However, further improvement in contrast and reduction in power consumption are desired,
In a liquid crystal projector, there is a problem of suppressing black float, which is a weak point.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a projection display apparatus capable of improving contrast, reducing power consumption, and suppressing black floating when a liquid crystal projector is used.

  A first means for solving the above problem is a projection-type image display device that projects light by light-modulating light emitted from a light source with a light valve. A means for generating a signal indicating the average brightness of the image based on the signal, and when the signal indicates a bright value, the light quantity emitted from the light source is increased and the direction of opening the aperture is controlled while the signal Control means for reducing the amount of light emitted from the light source and controlling the diaphragm portion in the closing direction.

  A second means for solving the above-described problem is a light-shielding light that adjusts light-shielding of light emitted from a light source in a projection display apparatus that projects an image by light-modulating light emitted from a light source with a light valve. An adjustment unit, a means for generating a signal indicating an average brightness of the video based on the video signal, and an amount of light emitted from the light source when the signal indicates a bright value, and a light shielding amount by the light shielding adjustment unit Control means for reducing the amount of light emitted from the light source and increasing the light shielding amount by the light shielding adjusting unit when the signal shows a dark value. And

  As described above, according to the present invention, since the control for brightening the projected image when projecting a bright image and darkening the projected image when projecting a dark image is realized, the contrast is improved. In addition, since a liquid crystal light valve is used as the light valve, there is an effect that black floating can be suppressed.

  Hereinafter, a liquid crystal projector according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a view showing a three-plate liquid crystal projector of this embodiment. The light emitting part in the light source 1 is composed of an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp or the like, and the irradiation light is emitted as parallel light by a parabolic reflector and guided to the integrator lens 4.

The integrator lens 4 is composed of a pair of lens groups (fly eye lenses) 4a and 4b, and each lens portion guides light emitted from the light source 1 to the entire surface of a liquid crystal light valve to be described later. The partial luminance unevenness existing in the light source 1 is averaged, and the light amount difference between the center of the screen and the peripheral portion is reduced. The light passing through the integrator lens 4 is guided to the first dichroic mirror 7 after passing through the polarization conversion device 5 and the condenser lens 6.

  The polarization conversion device 5 is configured by a polarization beam splitter array (hereinafter referred to as a PBS array). The PBS array includes a polarization separation film and a phase difference plate (1 / 2λ plate). Each polarization separation film of the PBS array passes, for example, P-polarized light out of the light from the integrator lens 4 and changes the optical path of S-polarized light by 90 °. The optically polarized S-polarized light is reflected by the adjacent polarization separation film and emitted as it is. On the other hand, the P-polarized light transmitted through the polarization separation film is converted into S-polarized light by the retardation plate provided on the front side (light emitting side) and emitted. That is, in this case, almost all light is converted to S-polarized light.

  The first dichroic mirror 7 transmits light in the red wavelength band and reflects light in the cyan (green + blue) wavelength band. The light in the red wavelength band that has passed through the first dichroic mirror 7 is reflected by the reflection mirror 8 to change the optical path. The red light reflected by the reflection mirror 8 is light-modulated by passing through a lens 9 and a transmissive liquid crystal light valve 31 for red light. On the other hand, the light in the cyan wavelength band reflected by the first dichroic mirror 7 is guided to the second dichroic mirror 10.

  The second dichroic mirror 10 transmits light in the blue wavelength band and reflects light in the green wavelength band. The light in the green wavelength band reflected by the second dichroic mirror 10 is guided to the transmissive liquid crystal light valve 32 for green light through the lens 11 and is modulated by being transmitted therethrough. The light in the blue wavelength band that has passed through the second dichroic mirror 10 is guided to the blue-light transmissive liquid crystal light valve 33 through the total reflection mirror 12, total reflection mirror 13, and lens 14, and is transmitted therethrough. It is optically modulated.

  Each of the liquid crystal light valves 31, 32, 33 includes a panel portion 31b, in which liquid crystal is sealed between an incident-side polarizing plate 31a, 32a, 33a and a pair of glass substrates (with pixel electrodes and alignment films formed). 32b, 33b and output side polarizing plates 31c, 32c, 33c.

  The modulated light (each color video light) modulated by passing through the liquid crystal light valves 31, 32, 33 is synthesized by the cross dichroic prism 15 to become color video light. The color image light is enlarged and projected by the projection lens 16, and is projected and displayed on a screen (not shown).

  As shown in FIG. 2, the projection lens 16 includes a diaphragm mechanism 21 for narrowing the projected image light and a diaphragm mechanism motor (for example, using a stepping motor) 22. When a driving signal is given to the diaphragm mechanism motor 22 from a microcomputer 25 described later, the diaphragm state of the diaphragm mechanism 21 is adjusted.

FIG. 3A is a block diagram showing an image processing system and a light source control system of the projection display apparatus, and FIG. 3B is an explanatory diagram showing the light source control system by functional blocks. The video signal processing circuit 23 receives the video signal and performs processing such as frequency conversion (scanning line number conversion) and the like, and the average brightness (APL) of the frame video for each frame period based on the video signal (Y signal). : Generates data indicating Average Picture Lever). When an RGB signal is input as a video signal, Y data may be generated by matrix conversion of the RGB signal. The gamma correction circuit 24 performs correction processing in consideration of the applied voltage-light transmission characteristics of the liquid crystal light valve (LCD), and applies (drives) the corrected video signal (video data) to the liquid crystal light valve. The microcomputer 25 functions as a dimming calculation block shown in FIG. 5B, receives APL data and generates dimming data, and also functions as a lamp driver control block, and sends a dimming command to the lamp driver 26. Process to send. The lamp driver 26 receives the dimming command and controls the amount of light emitted from the light source (lamp).

  FIG. 4A is an explanatory diagram showing the relationship between APL data, APL average value generation, and dimming data conversion processing, and FIG. 4B is a table for generating dimming data based on the APL average value ( It is explanatory drawing which showed the nonlinear conversion characteristic in the light control calculation block. For example, APL data (for example, 6-bit data) is generated for each frame period (every 1 V), and an APL average value (for the same 6-bit data) is an average value of APL data for four consecutive frame periods. . When the APL average value is given to the table as a read address, dimming data (for example, 4-bit data: 16 levels from 0 to 15) is output from the table. For example, when the video is the darkest video, the dimming data is “0000”, and when the video is the brightest video, the dimming data is “1111”.

  In the power supply section of the lamp driver 26, for example, a circuit is provided in which a plurality of resistors are connected in series so that a desired voltage can be taken out by a voltage drop generated at the connection point of each resistor. That is, a switch is connected to each connection point of each resistor, and the light source driving power can be switched depending on which switch is turned on. For example, when “1111” is received as the dimming command, the lamp driver 26 controls the switch so as to emit light at the maximum output watt (eg, 130 W), and “0000” as the dimming command. "Is received, the switch is controlled to emit light at a minimum output wattage (for example, 105 W). Of course, the power switching circuit is not limited to the above-described resistor and switch, and a circuit that switches power consumption by phase control, switching power supply control, or the like may be used.

In this way, when projecting a bright image, the lamp light amount is increased to brighten the projected image, and when projecting a dark image, the lamp light amount is decreased to darken the projected image, thereby improving contrast and suppressing black float. . In addition, reducing the lamp light amount reduces the power consumption and improves the energy saving effect. Note that execution of light source control based on APL may be selected by a user operation.
(Projected image light aperture control based on APL)
The microcomputer 25 can perform projection image light aperture control based on APL together with the lamp light amount control described above or instead of the lamp light amount control. When performing this projection image light aperture control, the microcomputer 25 performs drive control of the aperture mechanism motor 22 based on APL, and adjusts the aperture state of the aperture mechanism 21. That is, when projecting a bright image, the aperture is opened to make the projected image brighter, and when projecting a dark image, control is performed to close the aperture and darken the projected image.
(Shading control based on APL)
A shutter device may be provided, and the amount of illumination light blocked may be controlled based on APL. For example, as shown in FIG. 5, the shutter device 27 includes 15 shutter portions 28, and each shutter portion 22 is in the vicinity of the lens group 4 b located on the polarization conversion device 5 side and obstructs the passage of effective illumination light. It is provided in a position that does not. Each shutter section 28 includes a shaft 28a arranged in the vertical direction and a light shielding plate 28b fixed to the shaft 28a. By rotating the shaft 22a by 90 °, the illumination light is blocked and passed. Can be switched. A driving device (not shown) individually rotates each shutter unit 28 by an actuator such as a motor or an electromagnetic solenoid. For example, when “1111” is received as the dimming command, this driving device forms a passing state for all the shutter portions 28, and when “1110” is received, the driving device shields the rightmost shutter portion 28. When “1101” is received, the light shielding state is also formed for the leftmost shutter portion 28. When “1100” is received, the light shielding state is also formed for the second shutter portion 28 from the left end. As described above, the light shielding operation is executed.

  The projection image light aperture control and light shielding control based on the APL described above do not reduce the lamp light amount, so the power consumption cannot be reduced. In this case, since the control for darkening the projected image is realized, the contrast is improved and the black float can be suppressed.

1 is a configuration diagram illustrating a liquid crystal projector according to an embodiment of the present invention. It is an expansion perspective view of a projection lens. FIG. 4A is a block diagram showing a video processing system and a light source control system, and FIG. 4B is an explanatory diagram showing the light source control system by functional blocks. (A) is an explanatory view showing the relationship between APL data, APL average value generation, and dimming data conversion processing, and (b) in FIG. 11 is a nonlinear view in a table for generating dimming data based on the APL average value. It is explanatory drawing which showed the conversion characteristic. It is the top view which expanded and showed the arrangement | positioning location of an optical shutter apparatus.

Explanation of symbols

1 Light source 4 Integrator lens 4a and 4b Lens group (fly eye lens)
5 Polarization Converter 23 Video Signal Processing Circuit 24 Gamma Correction Circuit 25 Microcomputer
26 Lamp driver 28 Shutter device 31, 32, 33 Liquid crystal light bulb

Claims (2)

In a projection-type image display device that projects light by modulating light emitted from a light source with a light valve, generates a signal that indicates the average brightness of the image based on the aperture that restricts the projected image light and the image signal. And when the signal shows a bright value, the amount of light emitted from the light source is increased and controlled in the direction to open the aperture, while when the signal shows a dark value, the amount of light emitted from the light source is reduced. And a control means for controlling the closing portion in the closing direction. In a projection display apparatus for projecting an image by modulating light emitted from a light source with a light valve, a shading adjustment unit for adjusting shielding of the emitted light from the light source, and an average brightness of the image based on the video signal When the signal indicates a bright value and the signal indicates a bright value, control is performed to increase the amount of light emitted from the light source and to reduce the light shielding amount by the light shielding adjusting unit, while the signal has a dark value. The projection type image display apparatus includes: a control unit that performs control to reduce the amount of light emitted from the light source and to increase a light shielding amount by the light shielding adjustment unit.