JP2008052230A - Rear projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear projector capable of controlling a projection part by appropriately grasping influences of degradation in a projection optical system as well as degradation in a light source. <P>SOLUTION: The rear projector includes at least one optical sensor 40 disposed on an overshoot part 30 being non-display region in a projection region and a projection part 10 which projects a calibration image to the projection region, wherein the projection part 10 comprises a plurality of light sources 130, a driving part 140 which drives respective light sources 130, a driving control part 150 which controls the driving part 140 and a projection optical system 11, the optical sensor 40 measures a brightness value of the calibration image and the driving control part 150 controls the driving part 140 by feeding-back on the basis of the brightness value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rear projector.

  When individual light sources for each color such as RGB are used in the rear projector, it is conceivable that the color displayed by the rear projector changes over time due to deterioration of the light source over time. In such a case, a method of correcting the illuminance by measuring with a sensor can be considered.

  For example, in Patent Document 1, an optical sensor is provided in the vicinity of the lower part of each RGB LED, the luminance level is detected by the optical sensor, converted into a voltage value, the voltage value is compared with a reference voltage, and the LED is compared. A technique for adjusting the brightness level is described.

In Patent Document 2, there is a method of adjusting the white balance of an image by using three types of backlights that emit different colors for illuminating the LCD from the back and three types of light sensors corresponding to the three types of emission colors. Are listed.
JP 10-49074 A JP-A-11-295589

  Since the methods of Patent Documents 1 and 2 are methods for applying feedback by measuring the luminance of the LED itself, it is impossible to correct deterioration of the entire projection unit including the light source and the projection optical system.

  Also, a method of sequentially lighting the LEDs and measuring the luminance of the LEDs is conceivable, but this method cannot be used for display methods other than the field sequential method.

  Furthermore, when the common voltage value, which is the center value of the highest voltage and the lowest voltage at the time of AC driving of the LCD, changes with time, a luminance difference may occur and flicker may occur. In order to prevent the occurrence of such a situation, it is necessary to appropriately adjust the drive voltage of the LCD by appropriately measuring the brightness value such as the illuminance value of the image.

  An object of the present invention is to provide a rear projector capable of appropriately adjusting a driving voltage during AC driving of an LCD.

In order to solve the above problem, a rear projector according to the present invention includes at least one sensor provided in an overshoot portion that is a non-display area in a projection area;
A projection unit for projecting a calibration image to the projection area;
Including
The projection unit
Multiple light sources;
A drive unit for driving each light source;
A drive control unit for controlling the drive unit;
A projection optical system that projects light from each light source via a spatial light modulator;
Have
The sensor measures a brightness value of the calibration image;
The drive control unit feedback-controls the drive unit based on the brightness value.

  According to the present invention, since the rear projector can measure the brightness value of the actually projected image by the sensor provided in the overshoot portion, not only the deterioration of the light source but also the deterioration of the projection optical system. The impact can be grasped appropriately. Further, the rear projector can appropriately control the light source according to deterioration of the light source or the like by performing feedback control of the drive unit based on the brightness value.

Further, the projection unit sequentially projects an image for projecting a color corresponding to each light source on the overshoot portion as the calibration image,
The sensor may sequentially measure the brightness value of the image.

  According to this, the rear projector can appropriately grasp the influence of the deterioration of the optical system at a lower cost by using one sensor without using a plurality of sensors.

The rear projector includes a storage unit that stores pattern data for projecting a color corresponding to each light source in the overshoot portion,
The calibration image may include an input image based on an input image signal and a pattern image based on the pattern data.

  According to this, the rear projector can adjust the driving of the light source in a state where the input image is projected, and it is not always necessary to adjust the driving of the light source before the input image is projected. The drive can be adjusted.

In addition, as the at least one sensor, a plurality of sensors that measure brightness values of colors corresponding to the respective light sources are provided,
The projection unit projects an image for projecting a color corresponding to each light source on each sensor as the calibration image,
The plurality of sensors each measure a brightness value of the image,
The drive control unit may feedback control the drive unit based on a brightness value measured by each sensor.

  According to this, since the rear projector does not need to sequentially project calibration images, it is possible to appropriately grasp the influence of deterioration of the projection unit in a shorter time.

The plurality of light sources are provided for each primary color,
The rear projector may include a color balance determination unit that controls the drive control unit so as to maintain a balance between the primary colors based on the brightness value.

  According to this, the rear projector can reduce the influence of deterioration while maintaining a balance with other primary colors even when only a light source of a certain primary color is deteriorated.

The rear projector is
A common voltage value determining unit for determining a common voltage value based on the brightness value;
The projection unit
Multiple LCDs for each light source;
An LCD drive unit for driving each LCD;
An LCD drive signal processing unit for outputting a drive signal for driving the LCD with a drive voltage based on the common voltage value to the LCD drive unit;
May be included.

The rear projector according to the present invention includes at least one sensor provided in an overshoot portion that is a non-display area in the projection area,
A projection unit for projecting a calibration image to the projection area;
A common voltage value determination unit for determining a common voltage value based on a brightness value of the calibration image measured by the sensor;
Including
The projection unit
Multiple light sources;
Multiple LCDs for each light source;
An LCD drive unit for driving each LCD;
An LCD drive signal processing unit for outputting a drive signal for driving the LCD with a drive voltage based on the common voltage value to the LCD drive unit;
It is characterized by including.

  According to the present invention, the rear projector can grasp the flicker of the image by measuring the brightness value of the actually projected image. As a result, the rear projector can determine the common voltage value so as to eliminate the flicker, and can appropriately adjust the driving voltage of each LCD.

The rear projector is
A storage unit for storing pattern data for measuring the brightness value;
Based on the pattern data, a control unit that generates a control signal for projecting a pattern image on a portion of the overshoot portion where the sensor is provided;
Including
The calibration image includes an input image based on an input image signal and the pattern image,
The LCD drive signal processing unit may output a drive signal for projecting the calibration image to the LCD drive unit based on the control signal.

  According to this, the rear projector can adjust the common voltage value while projecting the input image, and does not necessarily need to adjust the common voltage value before projecting the input image. The common voltage value can be adjusted.

  Further, the common voltage value determination unit obtains a frequency component by performing a fast Fourier transform on the brightness value, and the common voltage value so that the frequency component of the frequency that the common voltage value has the most influence is minimized. May be determined.

  According to this, the rear projector can appropriately adjust the common voltage by determining the common voltage value so that the frequency component is minimized, that is, the flicker is minimized.

  Hereinafter, a case where the present invention is applied to a rear projector will be described as an example with reference to the drawings. In addition, the Example shown below does not limit the content of the invention described in the claim at all. In addition, all of the configurations shown in the following embodiments are not necessarily essential as means for solving the problems described in the claims.

  First, an example of controlling the driving of the light source in accordance with the influence of deterioration of the light source or the like will be described, and then an example of adjusting the LCD driving voltage based on the common voltage value will be described.

(First embodiment)
FIG. 1 is a schematic diagram showing a projection situation in the first embodiment.

  As shown in FIG. 1, the rear projector projects an image from the back side of the screen (screen) 20 through the projection lens 190, but cannot project at an accurate size according to the screen 20, and thus is larger than the screen 20. Project an image onto the projection area. For this reason, there is an overshoot portion 30 (shaded portion in FIG. 1) which is a non-display area outside the screen 20 on which an image is projected.

  FIG. 2 is a schematic diagram showing the arrangement of the optical sensors 40 in the first embodiment.

  In this embodiment, as shown in FIG. 2, an optical sensor 40 is provided in the overshoot portion 30, and the brightness value of the image projected from the projection lens 190 is measured using the optical sensor 40. Note that the brightness value corresponds to an illuminance value, a luminance value, an RGB value, an XYZ value, or the like. In this embodiment, the illuminance value is used.

  FIG. 3 is a diagram illustrating an example of the calibration image 200. FIG. 4 is a diagram illustrating another example of the calibration image 210.

  As shown in FIG. 3, the rear projector projects a calibration image 200 whose entire image is a single color (for example, red, blue, and green with the highest gradation) at the time of calibration before projecting a normal image. Good.

  Further, as shown in FIG. 4, the rear projector may project a calibration image 210 in which a part of the original image is replaced with a pattern image 212 during normal image projection (or during calibration). .

  The entire pattern image 212 is also an image of a single color (for example, red, blue, and green with the highest gradation), and is projected onto a portion where the optical sensor 40 is provided as shown in FIG. In this embodiment, the rear projector uses the calibration image 210.

  Further, since the overshoot portion 30 is outside the screen 20, the overshoot portion 30 is in a position that cannot be seen by an observer of the image. Thereby, the rear projector can measure the illuminance value of the image without disturbing the viewing of the observer.

  The rear projector adjusts the brightness of each of the RGB light sources according to the illuminance value.

  Next, functional blocks of a rear projector that implements such functions will be described.

  FIG. 5 is a functional block diagram of the rear projector in the first embodiment.

  The rear projector includes a projection unit 10, a screen 20, an overshoot portion 30, an optical sensor 40, an A / D conversion unit 50 that converts an analog measurement value of the optical sensor 40 into a digital value, and a color balance determination. The unit 60, the control unit 64, the storage unit 70, the light source power source 80, the LCD power source 82, and the image signal processing unit 90 are configured.

  Here, the storage unit 70 stores pattern data 72 and the like for projecting a color corresponding to each light source 130 in the overshoot portion 30. The control unit 64 outputs a control signal based on the pattern data 72 to the LCD drive signal processing unit 170 and controls the optical sensor 40.

  For example, the optical sensor 40 converts the measured illuminance value into an electric signal such as a voltage, the A / D conversion unit 50 converts the electric signal into a digital value, and the color balance determination unit 60 converts the digital value into the digital value. Based on the signal indicating the color of the pattern image 212 to be measured from the control unit 64, the drive control units 150-1 to 150-3 are controlled so that the balance of the RGB colors is maintained.

  The projection unit 10 controls the projection optical system 11, the light sources 130-1 to 130-3 for each LCD 120, the drive units 140-1 to 140-3 that drive the light sources 130, and the drive units 140. Drive control units 150-1 to 150-3 are included.

  The projection optical system 11 includes a condensing prism 110 that condenses R light, G light, and B light and outputs the light as one image light, and three LCDs (Liquid Crystal Display) that transmit or reflect RGB light. Also referred to as a liquid crystal panel.) 120-1 to 120-3, LCD driving units 160-1 to 160-3 for driving the respective LCDs 120, and a projection lens 190. The LCD 120 is a type of spatial light modulator.

  The driving unit 140 is supplied with a driving voltage from the light source power source 80, and the LCD driving unit 160 is supplied with a driving voltage from the LCD power source 82.

  Note that, for example, the following may be employed as hardware for implementing the functions of these units. For example, the optical sensor 40 is an illuminance sensor, the color balance determination unit 60, the control unit 64 is a CPU, the storage unit 70 is a RAM, the light source 130 is an LED (Light Emitting Diode), a drive unit 140, and a drive A circuit or the like may be used as the control unit 150, the LCD driving unit 160, and the LCD driving signal processing unit 170, and an image processing circuit or the like may be used as the image signal processing unit 90.

  Next, the flow of control using these units will be described.

  First, the control unit 64 outputs a control signal for projecting R light as the pattern image 212 to the LCD drive signal processing unit 170 based on the pattern data 72 stored in the storage unit 70. Since it is a rear projector, the distance from the projection lens 190 to the screen 20 is always constant, the position of the optical sensor 40 is also fixed, and the coordinate position and size of the pattern image 212 in the calibration image 210 are also fixed. ing.

  For this reason, as the pattern data 72, for example, data indicating the upper left coordinate position, lower right coordinate position, color, display order, etc. of the pattern image 212 is provided, so that the control unit 64 can perform a desired order in a desired order. A signal for projecting the color pattern image 212 can be output to the image signal processing unit 90.

  For example, the image signal processing unit 90 outputs an image signal for projecting the calibration image 210 illustrated in FIG. 4 to the LCD drive signal processing unit 170, and the LCD drive signal processing unit 170 performs the LCD based on the image signal. A drive signal is output to each LCD drive unit 160. Note that the method of driving the LCD 120 based on the image signal is a general method, and thus description thereof is omitted.

  The projection optical system 11 projects, for example, a calibration image 210 shown in FIG. 4 based on the LCD drive signal.

  The optical sensor 40 measures the illuminance value of the pattern image 212 (R light) projected on the overshoot portion 30 and converts the illuminance value into a voltage, and the A / D converter 50 performs color balance on the measured value obtained by digitally converting the voltage. The data is output to the determination unit 60. When the optical sensor 40 has a function of outputting a digital value, the A / D conversion unit 50 is not necessary.

  In this way, the projection unit 10 sequentially projects R light, G light, and B light as the pattern image 212, the optical sensor 40 measures the illuminance value of each pattern image 212, and the color balance determination unit 60 performs control. The measured value is stored in the storage unit 70 via the unit 64.

  The color balance determination unit 60 compares the measurement reference value of each primary color light (R light, G light, and B light) stored in the storage unit 70 with the actual measurement value of each primary color light, and the measurement value is the measurement reference. If it is smaller than the value, control data for outputting a control signal for brightening is stored in the storage unit 70, and if the measured value is larger than the measurement reference value, a control signal for darkening is output. Is stored in the storage unit 70.

  Further, the color balance determination unit 60 determines each control data so as to keep the balance of each primary color light. For example, the color balance determination unit 60 determines each control data so as to reduce the adjustment amount when the balance of each primary color light is lost due to the brightness adjustment.

  Then, the color balance determination unit 60 outputs a control signal for causing the drive control units 150-1 to 150-3 to adjust the light amounts of the light sources 130-1 to 130-3 based on the control data.

  Thus, the light sources 130-1 to 130-3 are feedback-controlled so as to output light with appropriate brightness, and the rear projector can project an image with appropriate brightness.

  As described above, according to the present embodiment, the rear projector can measure the brightness value of the actually projected image by the optical sensor 40 provided in the overshoot portion 30, and therefore only the light source 130. In addition, it is possible to appropriately grasp the influence of deterioration of the entire projection unit 10. Further, the rear projector can appropriately control the projection unit 10 according to deterioration of the light source 130 and the like by performing feedback control of the drive unit 140 based on the illuminance value. That is, according to the present embodiment, the rear projector can grasp the influence of the deterioration of the entire projection unit 10 as compared with the case of directly measuring the light of the individual light source, and thus can perform correction with higher accuracy.

  In addition, for example, in the conventional method, there is a method for inferring deterioration according to the operating time of the light source 130, but with such a method, it is impossible to grasp the influence of individual differences of each light source 130. On the other hand, according to the present embodiment, the rear projector can grasp the influence of individual differences of each light source 130 by measuring the projection light of each light source 130 individually, and more accurately the brightness of the image. Can be adjusted.

  Further, according to the present embodiment, the rear projector can appropriately grasp the influence of the deterioration of the projection unit 10 at a lower cost by using one optical sensor 40 without using a plurality of sensors.

  Further, according to the present embodiment, the rear projector can adjust the brightness of the image by providing the optical sensor 40 in the overshoot portion 30 without the observer being aware of the presence of the optical sensor 40. .

  Further, according to the present embodiment, the rear projector can adjust the driving of the light source 130 using the calibration image 210 in which the input image is overwritten with the pattern image 212 by using the pattern data 72, and the input is not necessarily performed. Since it is not necessary to adjust the driving of the light source 130 before projecting an image, the driving of the light source 130 can be adjusted more efficiently, that is, the brightness can be adjusted.

  Further, according to the present embodiment, the rear projector can maintain the color balance of each light source 130 by using the color balance determination unit 60 even when the individual light sources are individually controlled. For example, even when only the R light source 130-1 is deteriorated, the influence of the deterioration can be reduced while maintaining the balance with the other G light and B light.

(Second embodiment)
Next, an example of adjusting the driving voltage of the LCD based on the common voltage value will be described. The common voltage value is a value serving as a reference for driving voltage for driving each LCD, and more specifically, for example, is a positive or negative center value for performing AC driving of the LCD 120.

  FIG. 6 is a functional block diagram of the rear projector in the second embodiment.

  The rear projector includes a projection unit 10, a screen 20, an overshoot portion 30, an optical sensor 40, an A / D conversion unit 50 that converts an analog measurement value of the optical sensor 40 into a digital value, and a color balance determination. A unit 60, a common voltage value determination unit 62, a control unit 64, a storage unit 70, a light source power supply 80, and an image signal processing unit 90 are configured.

  Here, the storage unit 70 stores pattern data 72 and the like for projecting a color corresponding to each light source 130 in the overshoot portion 30. The control unit 64 outputs a control signal based on the pattern data 72 to the LCD drive signal processing unit 170 and controls the optical sensor 40.

  For example, the optical sensor 40 converts the measured illuminance value into an electric signal such as a voltage, the A / D conversion unit 50 converts the electric signal into a digital value, and the color balance determination unit 60 converts the digital value into the digital value. Based on the signal indicating the color of the pattern image 212 to be measured from the control unit 64, the drive control units 150-1 to 150-3 are controlled so that the balance of the RGB colors is maintained.

  Further, the common voltage value determination unit 62 determines a common voltage value based on the measurement value from the A / D conversion unit 50 and outputs the common voltage value to the LCD drive signal processing unit 170.

  The projection unit 10 controls the projection optical system 11, the light sources 130-1 to 130-3 for each LCD 120, the drive units 140-1 to 140-3 that drive the light sources 130, and the drive units 140. Drive control units 150-1 to 150-3 are included.

  The projection optical system 11 includes a condensing prism 110 that condenses R light, G light, and B light and outputs the light as one image light, and three LCDs (Liquid Crystal Display) that transmit or reflect RGB light. Also referred to as a liquid crystal panel.) 120-1 to 120-3, LCD driving units 160-1 to 160-3 for driving the respective LCDs 120, and a projection lens 190.

  The driving unit 140 is supplied with a driving voltage from the light source power source 80, and the LCD driving unit 160 is supplied with a driving voltage from the LCD power source 82.

  Note that, for example, the following may be employed as hardware for implementing the functions of these units. For example, an illuminance sensor or the like as the optical sensor 40, a color balance determination unit 60, a common voltage value determination unit 62, a CPU or the like as the control unit 64, a RAM or the like as the storage unit 70, and an LED (Light Emitting Diode) as the light source 130. As the drive unit 140, the drive control unit 150, the LCD drive unit 160, and the LCD drive signal processing unit 170, a circuit or the like may be employed, and as the image signal processing unit 90, an image processing circuit or the like may be employed.

  Next, the flow of control using these units will be described.

  FIG. 7 is a schematic diagram showing a driving voltage and a luminance difference in the second embodiment.

  The liquid crystal (LCD 120) needs to be driven by alternating current, and if the LCD 120 is driven while the direct current component remains, it causes a display defect (burn-in, etc.) and a decrease in life. For example, even when AC driving is performed, if a DC component remains, a luminance difference occurs at each driving timing as shown in FIG.

  In addition, as shown in FIG. 7, when the positive polarity maximum drive voltage is V1, the positive polarity minimum drive voltage is V2, the negative polarity maximum drive voltage is V3, and the negative polarity minimum drive voltage is V4, the common voltage value Is the center value of V1 and V4. In practice, a common voltage value exists for each of R, G, and B.

  When the highest voltage and the lowest voltage applied to the LCD 120 around the common voltage value are not targeted, the luminance difference increases as the degree of deviation of the common voltage value from the center increases. Further, such a shift may occur not only when the light source 130 is deteriorated but also when the continuous operation time of the LCD 120 becomes long.

  In FIG. 7, the polarity is inverted every field, but the polarity is inverted every 0.5 field when the LCD 120 is driven at double speed. The polarity inversion method may be for each line (line inversion driving) as shown in FIG. 7 or for each pixel (dot inversion driving).

  In the case of NTSC, since one field is 60 Hz, the frequency of the luminance difference accompanying the shift of the common voltage value is 30 Hz.

  In this embodiment, the illuminance value (luminance value, RGB value, XYZ value, etc.) of the calibration image projected from the projection lens 190 is measured using the optical sensor 40. The calibration image may be any color and any gradation, but the rear projector may use, for example, a calibration image having an intermediate gradation of each primary color. Since the rear projector has an intermediate gray level between the highest voltage and the lowest voltage, the common voltage value can be determined more appropriately.

  In this embodiment, the calibration image 210 including the pattern image 212 shown in FIG. 4 is used. In this case, the pattern image 212 is one of an intermediate gradation of R light, an intermediate gradation of G light, and an intermediate gradation of B light.

  The optical sensor 40 measures the illuminance value of each pattern image 212 and converts it into a voltage. The A / D converter 50 digitally converts the voltage to generate a measured value. Based on the measurement value from the D conversion unit 50, FFT (Fast Fourier Transform) is performed to obtain a frequency component.

  FIG. 8 is a diagram showing frequency components for each frequency in the second embodiment.

  When the common voltage value is shifted, the frequency component of 30 Hz increases when displaying at 60 Hz. For this reason, the control part 64 determines a common voltage value so that the frequency component of 30 Hz may become the minimum.

  FIG. 9 is a diagram showing an optimum common voltage value in the second embodiment. FIG. 10 is a schematic flowchart showing a processing procedure for determining an optimum common voltage value in the second embodiment.

  The common voltage value is Vcom, the initial value of the common voltage value is Vcom0, and the voltage value to be changed is Vchg. In addition, the initial value of the FFT output value in the case of 30 Hz by the control unit 64 is F0, and the output value of the nth measurement after the first time is Fn.

  For example, in the case of the second measurement (n = 1), the control unit 64 sets the common voltage value Vcom to Vcom0 + Vchg (step S1). The drive signal processing unit 170 outputs the drive signal to the LCD drive units 160-1 to 160-1 so that a common voltage value becomes Vcom and an image of an intermediate gradation is projected based on the image signal from the image signal processing unit 90. Output to 160-3.

  The LCD driving units 160-1 to 160-3 drive the LCDs 120-1 to 120-3 based on the driving signal.

  The optical sensor 40 measures the illuminance value of the intermediate gradation image projected through the projection lens 190 and outputs a voltage, and the A / D converter 50 generates a measurement value obtained by digitally converting the voltage.

  The control unit 64 performs an FFT process on the measurement value from the A / D conversion unit 50 to obtain an output value F1.

  Then, the control unit 64 determines whether or not the first output value F0 is greater than or equal to the second output value F1 (step S2).

  When F0 is F1 or more, the control unit 64 sets the common voltage value Vcom to Vcom + Vchg (step S3), and the optical sensor 40 measures the illuminance value of the image in which the LCD 120 is driven under this condition.

  Then, the control unit 64 performs an FFT process on the measurement value from the A / D conversion unit 50 to obtain an output value Fn.

  Further, the rear projector changes the common voltage value (step S3), projects the calibration image, measures the illuminance value, until Fn becomes Fn-1 (n-1th output value) or more (step S4). The calculation of the output value by FFT and the comparison of the output values (step S4) are repeatedly executed.

  On the other hand, when F0 is less than F1, the control unit 64 sets the common voltage value Vcom to Vcom0−Vchg (step S5), and the optical sensor 40 measures the illuminance value of the image in which the LCD 120 is driven under these conditions. .

  Then, the control unit 64 performs an FFT process on the measurement value from the A / D conversion unit 50 to obtain an output value Fn.

  Further, the rear projector changes the common voltage value to decrease by Vchg (step S7) until Fn becomes equal to or larger than Fn-1 (n-1th output value) (step S7), projection of the calibration image, and illuminance value. Measurement, output value calculation by FFT, and output value comparison (step S6) are repeatedly executed.

  Through the above procedure, the control unit 64 can determine an optimum common voltage value in the preparation stage, and the LCD drive signal processing unit 170 generates a drive signal so as to be the common voltage value, and drives each LCD drive. The unit 160 can drive the LCD 120 with drive voltages V1 to V4 corresponding to the respective primary colors.

  As described above, according to the present embodiment, the rear projector can grasp the flicker of the image by measuring the illuminance value of the actually projected image. As a result, the rear projector can determine the common voltage value so as to eliminate the flicker, and can appropriately adjust the voltage related to the driving of each LCD driving unit 160.

  Further, according to this embodiment, the rear projector appropriately adjusts the driving voltage of the LCD 120 by determining the common voltage value so that the frequency component is minimized, that is, the flicker is minimized. Can do.

  As described above, the common voltage value may shift as the continuous operation time of the LCD 120 becomes longer. For this reason, the rear projector performs measurement by the optical sensor 40 at regular time intervals (for example, 10 minutes, 30 minutes, 1 hour, etc.), compares the FFT calculation by the control unit 64 and the FFT calculation result (Fn), and determines the optimum. The common voltage value may be reset when the FFT calculation result Fo at the time of determining the common voltage value and the latest FFT calculation result Fn are different from each other by a set value (for example, 3 dB). Further, the rear projector may automatically reset the common voltage value at every predetermined time.

  According to this, the rear projector can appropriately correct the shift of the common voltage value in the actual projection stage, and can suppress the occurrence of image flicker.

  Note that the rear projector is provided with the optical sensor 40 in the overshoot portion 30 and projects the calibration image 210 including the input image as the pattern image 212 shown in FIG. 4 so that the observer can notice the presence of the optical sensor 40. The driving voltage of the LCD 120 based on the common voltage value can be adjusted without any problem.

  Further, according to the present embodiment, the rear projector can adjust the driving of the LCD 120 by using the calibration image 210 in which the input image is overwritten with the pattern image 212 by using the pattern data 72, and the input image is not necessarily required. Therefore, it is not necessary to adjust the driving of the LCD 120 before the projection of the image, so that the driving of the LCD 120 can be adjusted more efficiently.

(Other examples)
In addition, application of this invention is not limited to the Example mentioned above, A various deformation | transformation is possible.

  For example, the first embodiment and the second embodiment may be combined. That is, the rear projector may adjust the light amount of the light source 130 while maintaining the color balance, and may adjust the driving voltage of the LCD 120 based on the common voltage value determined from the illuminance value.

  In the above-described embodiment, one optical sensor 40 is used, but a plurality of sensors may be used.

  FIG. 11 is a schematic diagram showing the arrangement of the optical sensors 40-1 to 40-3 in other embodiments. FIG. 12 is a diagram illustrating an example of a calibration image 220 in another embodiment.

  For example, as shown in FIG. 11, an optical sensor 40-1 that measures the brightness value of the R light, an optical sensor 40-2 that measures the brightness value of the G light, and an optical sensor that measures the brightness value of the B light. 40-3 may be provided at different positions of the overshoot portion 30.

  In this case, as shown in FIG. 12, at the time of brightness adjustment, the highest gradation R color as the pattern image 222 for the optical sensor 40-1, and the highest gradation G color as the pattern image 224 for the optical sensor 40-2. The B color of the highest gradation is projected as the pattern image 226 for the optical sensor 40-3, and at the time of adjusting the driving voltage of the LCD 120, the R color of the intermediate gradation as the pattern image 222 for the optical sensor 40-1, the optical sensor Pattern data 72 for projecting the intermediate gradation G color as the pattern image 224 for 40-2 and the intermediate gradation B color as the pattern image 226 for the optical sensor 40-3 is stored in the storage unit 70. .

  The control unit 64 causes the projection unit 10 to project pattern images 222 to 226 corresponding to a target adjustment target based on the pattern data 72.

  According to this, the rear projector can simultaneously project colors corresponding to the respective optical sensors 40. As a result, the rear projector does not need to sequentially project calibration images, so that the influence of deterioration of the projection unit 10 can be properly grasped in a shorter time, and it can also be used for display methods other than the field sequential method. it can. Note that the rear projector may use pattern images of the same gradation regardless of the adjustment target.

  The rear projector may project a moving image or a still image, or may have a TV function (for example, a projection TV).

  The application of the present invention relating to the first embodiment is not limited to a rear projector having a liquid crystal display device as long as it has an individual light source. For example, DMD (Digital Micromirror) developed by Texas Instruments, USA A rear projector using Device) may be used. DMD is a kind of spatial light modulator.

  The pattern data 72 may be data for projecting a single color calibration image shown in FIG.

  According to this, since the rear projector can project the calibration image 200 without using an image signal, the brightness of the image and the drive voltage of the LCD 120 can be adjusted more easily.

  Further, the application of the present invention relating to the second embodiment is not limited to one having an individual light source, and may have a common light source.

  Further, the position where the optical sensor 40 is provided may be a retrace period portion outside the overshoot portion 30.

  For example, in the case of the NTSC signal, the actual data signal is 482.5 lines for 525 scanning lines, and the remaining 42.5 lines are the blanking period parts (the outer parts above and below the overshoot part 30). It is. In the case of using a rear projector capable of performing projection in the blanking period portion, the optical sensor 40 may be provided in the blanking period portion of the screen 20 surface. In the above-described embodiment, the optical sensor 40 is provided on the lower side portion of the overshoot portion 30, but the installation position is arbitrary.

  In the above-described embodiment, the control unit 64 adjusts the image signal of the image signal processing unit 90 in order to project a pattern image or a single color calibration image, but sends a control signal to the LCD drive signal processing unit 170. It may be output. The LCD drive signal processing unit 170 may output a drive signal for projecting a pattern image or a single color calibration image to the LCD drive unit 160 based on the control signal. Also by this, the rear projector can project a calibration image including a pattern image or a single color calibration image.

It is a schematic diagram which shows the projection condition in a 1st Example. It is a schematic diagram which shows arrangement | positioning of the optical sensor in a 1st Example. It is a figure which shows an example of a calibration image. It is a figure which shows another example of a calibration image. FIG. 2 is a functional block diagram of a rear projector in the first embodiment. It is a functional block diagram of the rear projector in a 2nd Example. It is a schematic diagram which shows the drive voltage and brightness | luminance difference in a 2nd Example. It is a figure which shows the frequency component for every frequency in a 2nd Example. It is a figure which shows the optimal common voltage value in a 2nd Example. It is a schematic flowchart which shows the process sequence which determines the optimal common voltage value in a 2nd Example. It is a schematic diagram which shows arrangement | positioning of the optical sensor in another Example. It is a figure which shows an example of the calibration image in another Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Projection part, 11 Projection optical system, 20 Screen, 30 Overshoot part, 40 Optical sensor, 60 Color balance determination part, 62 Common voltage value determination part, 64 Control part, 70 Storage part, 72 Pattern data, 120 LCD, 130 Light source, 140 drive unit, 150 drive control unit, 160 LCD drive unit, 170 drive signal processing unit, 190 projection lens

Claims (3)

At least one sensor provided in an overshoot portion that is a non-display area in the projection area;
A projection unit for projecting a calibration image to the projection area;
A common voltage value determination unit for determining a common voltage value based on a brightness value of the calibration image measured by the sensor;
Including
The projection unit
Multiple light sources;
Multiple LCDs for each light source;
An LCD drive unit for driving each LCD;
An LCD drive signal processing unit for outputting a drive signal for driving the LCD with a drive voltage based on the common voltage value to the LCD drive unit;
A rear projector comprising: The rear projector according to claim 1,
A storage unit for storing pattern data for measuring the brightness value;
Based on the pattern data, a control unit that generates a control signal for projecting a pattern image on a portion of the overshoot portion where the sensor is provided;
Including
The calibration image includes an input image based on an input image signal and the pattern image,
The rear projector, wherein the LCD drive signal processing unit outputs a drive signal for projecting the calibration image to the LCD drive unit based on the control signal. The rear projector according to any one of claims 1 and 2,
The common voltage value determining unit obtains a frequency component by performing a fast Fourier transform on the brightness value, and determines the common voltage value so that the frequency component of the frequency that the common voltage value has the most influence is minimized. A rear projector characterized by the above.

Images