JP4011091B2 - Projection display device - Google Patents

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 kept constant even when the average brightness (APL: Average Picture Level) of the video changes, or the average brightness of the video There has been proposed a projection display apparatus that improves the contrast by reducing the lamp driving power when the brightness (APL) is bright and increasing the lamp driving power when the brightness (APL) is 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.

  The means for solving the above-mentioned problem is that light emitted from a light source is transmitted through an integrator lens composed of a pair of lens groups, then polarized by a polarization converter, and light-modulated by a light valve. In the projection type image display device to project, the projection type image display device is disposed along the optical axis at a position in the vicinity of the lens group located on the polarization conversion device side between the pair of lens groups and which does not block the passage of effective illumination light. A light-blocking adjustment unit comprising a plurality of light-blocking members, each having a rotation center at the end on the polarization conversion device side, each independently rotating effective illumination light transmitted through the individual lens portions of the lens group. And a means for generating a signal indicating the average brightness of the video based on the video signal, and when the signal shows a bright value, the amount of light emitted from the light source is increased, and the light shielding amount by the light shielding adjusting unit is reduced. On the other hand, when the signal shows a dark value, the amount of light emitted from the light source is reduced, and the light shielding member located outside the plurality of light shielding members according to the degree that the signal shows a dark value And a control means for controlling to increase the light shielding amount by the light shielding adjusting unit by preferentially driving the light to the light shielding state.

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

  A liquid crystal projector according to an embodiment of the present invention will be described below 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 drive 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. 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 the APL average value (for the same 6-bit data) is the 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 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 with 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 portion 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 drive 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, the 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 leftmost shutter unit 28 is also formed with a light shielding state, and when “1100” is received, the second shutter unit 28 from the left end is also formed with a light shielding state. As described above, the light shielding operation is performed.

  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, but when projecting a bright image, the projected image is brightened and a dark image is projected. 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 non-linear diagram 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 (1)

In a projection display apparatus that projects light emitted from a light source through an integrator lens composed of a pair of lens groups, then polarizes the light by a polarization conversion device, modulates the light with a light valve, and projects an image. Between the lens groups in the vicinity of the lens group located on the side of the polarization conversion device and at a position that does not block the passage of effective illumination light, and is disposed along the end of the polarization conversion device side. A light-blocking adjustment unit composed of a plurality of light-blocking members, each having a moving center, each pivotally blocking effective illumination light that individually passes through individual lens portions of the lens group, and an average of images based on video signals A means for generating a signal indicating a target brightness, and when 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 adjustment unit, while the signal is dark. When the value is indicated, the amount of light emitted from the light source is reduced, and the light shielding member located outside of the plurality of light shielding members is preferentially driven to the light shielding state in accordance with the degree of the dark value of the signal. A projection display apparatus comprising: a control unit that performs control to increase a light shielding amount by the light shielding adjustment unit.