JP4266767B2 - Projection display device - Google Patents

Description

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

2. Description of the Related Art Conventionally, there has been proposed a projection display apparatus that controls lamp driving power based on average picture level (APL) (see Patent Document 1).
Japanese Patent Laid-Open No. 3-179886

  By the way, when lamp dimming control based on such an image is performed, assuming that the lamp power is the highest and the cooling fan is driven with a large amount of power, the state where the lamp power is low continues for a long time. In this case, the lamp may be overcooled, which may adversely affect the lamp life.

  In view of the above circumstances, an object of the present invention is to provide a projection display apparatus capable of preventing lamp overcooling in lamp dimming control.

  The projection display apparatus according to the present invention is a projection display apparatus that projects light by modulating light emitted from a light source with a light valve, and outputs a signal indicating the average brightness of the image based on the image signal. Generating means, a temperature sensor for detecting an air temperature in the apparatus, and a control means for controlling a light source and a cooling fan for cooling the light source. The control means outputs a signal indicating the average brightness of the image. And controlling the cooling fan based on the output of the signal indicating the average brightness of the image and the output of the temperature sensor, and if the signal is a bright image signal, the power supplied to the light source If the signal is a dark video signal, the power supplied to the light source is reduced, and the higher the temperature sensor output is, the higher the power supplied to the cooling fan is. Causes, characterized in that the signal to reduce the power supplied to as the cooling fan output is low of the temperature sensor in the dark image signal.

  With the above configuration, when the power supplied to the light source is increased, the power supplied to the cooling fan is increased, while when the power supplied to the light source is reduced, the power supplied to the cooling fan is reduced. Lamp overcooling in lamp dimming control can be prevented.

  The fan control means may control the power supplied to the cooling fan in correspondence with the average value of the power supplied to the light source. The fan control means preferably has an upper limit on the amount of change in power supplied to the cooling fan within a predetermined time. With these configurations, it is possible to eliminate a sudden change in the sound of the cooling fan and to prevent the sound of the cooling fan from becoming annoying. In addition, the fan control means sets the power supplied to the cooling fan after the light source is turned off to a value lower by a predetermined amount with respect to the power supplied at the time of turning off, and the power that exceeds the set supply power after a predetermined time after the setting. The cooling fan should be driven. Thereby, accurate light source cooling after light extinction becomes possible.

  According to the present invention, it is possible to prevent lamp overcooling in lamp dimming control.

  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).

  FIG. 2A is a block diagram showing an image processing system, a light source control system, and a cooling fan control system of the projection display apparatus, and FIG. 2B is an explanatory diagram showing the light source control system by functional blocks. is there. 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). : Processing to generate data indicating Average Picture level). 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. 4B, 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) 1.

  For example, the APL data is generated every frame period (every 1 V), and the APL average value is an average value of APL data of four consecutive frame periods. When the APL average value is given to the table as a read address, dimming data (for example, 3-bit data: 8 levels from 0 to 7) is output from the table. For example, when the video is the darkest video, the dimming data is “000”, and when the video is the brightest video, the dimming data is “111”.

  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 “111” is received as the dimming command, the lamp driver 26 controls the switch to emit light at the maximum output watt (eg, 135 W), and “000” as the dimming command. "Is received, the switch is controlled to emit light at a minimum output wattage (for example, 100 W). Of course, the power switching circuit is not limited to the above-described resistor and switch, and a circuit that switches supply power by phase control, switching power supply control, or the like may be used.

  The microcomputer 25 functions as a fan control unit, and gives a control signal to the fan driver 27. The fan driver 27 supplies a motor voltage (fan supply power) set based on the given control signal to the cooling fan 28. The control signal corresponds to lamp supply power (in this embodiment, the above-described dimming command is used instead of detecting the lamp supply power itself) and temperature data from the temperature sensor 29 that detects the temperature inside the apparatus. Generated. Specifically, as shown in FIG. 3, the fan voltage is changed (curved) in accordance with the temperature (output of the temperature sensor 29), and this change is caused by a difference in lamp supply power (dimming command). It is different. For example, when the dimming command is “111” (135 W), the uppermost change A in FIG. 3 is adopted, and when the dimming command is “110” (130 W), the second from the top in FIG. When the change B is adopted and the dimming command is “000” (100 W), the lowermost change H in FIG. 3 is adopted. Such control includes, for example, each change described above as a table, gives a dimming command and a temperature data value as an address to the table, obtains a fan voltage digital value from the table, and converts it to a D / A conversion. Thus, a method of obtaining a fan voltage value may be employed. Of course, it is not limited to such a method.

  By the way, when projecting an image with a drastic change in the APL value, the fan voltage also changes frequently, and the sound of the fan may be annoying. In order to eliminate this, the change in the APL value (or APL average value) is not directly reflected in the fan voltage, but the average value (for example, 1 second) of the APL value (or APL average value) ( That is, it is preferable to control the fan voltage based on the average value of the lamp supply power. In addition, when projecting an image with a large change width of the APL value, the change width of the fan voltage also becomes large, and there is a possibility that the sound of the fan may become annoying. Therefore, for example, when the dimming command changes to “111” in the state where the lowermost change H is adopted in FIG. 3 (dimming command “000”), the uppermost change A in FIG. Is set to an upper limit for the amount of change in the power supplied to the cooling fan 28 within a predetermined time. Specifically, if control is performed to maintain each step for, for example, 0.5 seconds by shifting to the next change step by step, the uppermost change A is adopted over 4 seconds in the above case. As a result, a sudden change in fan sound can be avoided.

  Normally, the cooling fan 28 is controlled to rotate for a while after the lamp is turned off. In this case, the cooling fan 28 is rotated in the low speed mode for a predetermined time in order to prevent overcooling of the light source (lamp) 1. It is conceivable to switch to the high speed mode later and rotate for a predetermined time. However, the lamp supply power immediately before the lamp is turned off differs depending on whether the image when the lamp is turned off is bright or dark, and accurate cooling cannot be performed with a single low-speed mode rotation. Therefore, the low-light-off mode is set for each of the steps (changes) in FIG. 3 described above. Specifically, a method of executing the low-speed mode at a voltage of, for example, 80% of the fan voltage just before turning off, and then executing the high-speed mode at a voltage higher than the voltage (may be the highest fan voltage), Or, the fan voltage (change (curve) adopted immediately before turning off) is changed to a low speed mode by using a change (curve) under one stage or under two stages, and then a voltage higher than that voltage. A method of executing the high speed mode at the maximum fan voltage may be adopted.

  In the above embodiment, a three-plate type liquid crystal projector using a liquid crystal display panel has been described. However, the present invention can also be applied to a projection type video display device having another video light generation system.

1 is a configuration diagram showing an optical system of a liquid crystal projector of an embodiment of the present invention. FIG. 4A is a block diagram showing a liquid crystal projector image processing system, a light source control system, and a fan control system, and FIG. 4B is an explanatory diagram showing the light source control system by functional blocks. It is the graph which showed the relationship between temperature and a fan voltage by using lamp electric power as a parameter.

Explanation of symbols

1 Light source 23 Video signal processing circuit 24 Gamma correction circuit 25 Microcomputer
26 Lamp Driver 27 Fan Driver 28 Cooling Fan 29 Temperature Sensor 31, 32, 33 Liquid Crystal Light Valve

Claims (4)

In a projection display apparatus for projecting an image by modulating light emitted from a light source with a light valve, means for generating a signal indicating the average brightness of the image based on the image signal, and the temperature in the apparatus A temperature sensor to detect, and a control means for controlling the light source and a cooling fan for cooling the light source, the control means controls the light source based on the output of a signal indicating the average brightness of the video, The cooling fan is controlled based on the output of the signal indicating average brightness and the output of the temperature sensor, and when the signal is a bright video signal, the power supplied to the light source is increased and the video signal is dark. In the case of the above-mentioned signal, the power supplied to the light source is reduced, the signal is a bright video signal, the higher the output of the temperature sensor, the higher the power supplied to the cooling fan and the darker the video Signal projection display apparatus wherein an output of the temperature sensor reduce the power supplied to lower the cooling fan. 2. The projection display apparatus according to claim 1, wherein the fan control means controls supply power to the cooling fan in accordance with an average value of supply power to the light source. . 3. The projection image display apparatus according to claim 1, wherein the fan control means has an upper limit on a change amount of power supplied to the cooling fan within a predetermined time. Display device. 4. The projection display apparatus according to claim 1, wherein the fan control means sets the power supplied to the cooling fan after the light source is turned off to a value lower by a predetermined amount based on the power supplied when the light is turned off. A projection-type image display apparatus, characterized in that the cooling fan is driven with a power exceeding the set supply power after a predetermined time of the setting.

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