JP2012248910A - Color correction method of projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a color correction function most suitable for both color corrections due to influences of screen color and external light in an image projection apparatus having a function of performing color correction processing of a screen by detecting reflection light from the screen.SOLUTION: The screen color is properly discriminated, and a color correction mode is switched to be optimized by using a sensor for detecting reflection light from the screen and an external light sensor. When the screen is colored, the color is corrected by a luminance correction table (1D-LUT), such as an RGB gain and gamma so that the luminance is not lowered as much as possible. Moreover, when the screen is white, the color can be properly corrected by a color correction table (3D-KUT) and the luminance correction table (1D-LUT) for correcting influence of peripheral environment light.

Description

  The present invention relates to an image projection apparatus having a function of detecting reflected light from a screen and performing color tone correction processing.

  In recent years, liquid crystal projectors that can easily project and display a large screen are widely used for presentations at conferences and home video content display. Liquid crystal projectors are used in various lighting environments, but it is desirable to reproduce colors according to actual projection environment lighting.

  On the other hand, CIECAM02 (CAM; Color Appearance Model) etc., which are chromatic adaptation models issued by the International Commission on Illumination (CIE), have been developed for color matching technology applications. It is becoming possible to reproduce colors that take into account the above.

  When color reproduction considering such visual adaptation is applied to a liquid crystal projector, it is necessary to acquire information on illumination light (environment light) as the visual environment information. As existing techniques for measuring such illumination light, for example, there are a spectroscopic measuring instrument using a diffraction grating, a color sensor using a color filter, and the like. Further, in order to correctly measure the illumination light, it is necessary to install an integrating sphere and a diffusion plate in front of these sensors.

  Although the illumination light can be accurately measured if the above equipment is provided, it is not preferable from the viewpoint of product cost. If a screen color measurement sensor (wall color sensor) for automatic screen color correction is installed, it is desirable to measure illumination light using this wall color sensor.

  As an example of measuring illumination light using a wall color sensor, in Patent Document 1, a plurality of calibration images such as white and black are projected, and color information when the calibration image is projected from the wall color sensor. And generating color conversion that matches the color appearance from the color information of the input image and the color information of the projection image on the projection plane, and converting the color of the input image based on the color conversion to the projector The correction color to be output is obtained.

  Further, in Patent Document 2, when it is determined that there is no input of image information of a normal image, that is, when it is determined that a synchronization signal is not input, a calibration image is generated and used for screen color correction. The three-dimensional look-up table (3D-LUT) and the one-dimensional look-up table (1D-LUT) for correcting the brightness of the screen are updated for each non-signal detection operation.

JP 2003-323610 A Japanese Patent No. 3755593

  In the method disclosed in Patent Document 1, an image for calibration is measured in advance to obtain a color conversion characteristic that realizes both the screen color correction and the influence correction by the ambient environment light. However, the correction value is not calculated by distinguishing whether the main color correction target is screen color correction or ambient ambient light. An image for calibration is projected, and a color conversion LUT that simultaneously realizes both the color correction of the screen and the correction of the influence of the ambient environment light is generated. For this reason, for example, there is a problem that a correction of a certain color is a color correction that lowers the luminance at best.

  In the method of Patent Document 2, it is necessary to block the synchronization signal between the 3D-LUT generation step for correcting the color of the projection plane and the 1D-LUT generation step for correcting the brightness of the projection plane. It takes a lot of time to process both steps. Further, since it is not stipulated whether the color correction on the projection plane or the brightness correction on the projection plane is prioritized, the 3D-LUT is generated and the influence of the ambient environment light is corrected, and then the 1D-LUT is generated. When the brightness of the screen is corrected, the color creation that corrects the influence of the ambient light previously performed is lost.

In order to solve the above problem, the image display device of the present invention provides:
An object is to improve accuracy by performing color correction optimal for each color correction mode of screen color correction and external light correction using means for accurately determining the color of the screen.

In order to solve the above problems in the projection image display device of the present invention,
According to the invention of claim 1,
In the projection display device having a color correction function of the display color by detecting the reflected light of the screen and changing various characteristics of the image according to the result,
First color sensor means for detecting different wavelength regions from the reflected light of the screen;
Reference value storage means for storing a value obtained by detecting screen reflected light as a reference by the color sensor means;
Second color sensor means for detecting different wavelength regions from light other than projection light; and
A reference value storing means for storing a value obtained by detecting external light as a reference by the color sensor means;
Means for determining that the screen color is within a predetermined color range by comparing the measurement value and the reference value of the first and second color sensors;
A color correction method for a projection display device is provided, wherein different color correction functions are executed depending on whether the color is within a predetermined color range or outside the predetermined color range.
According to invention of Claim 2,
In the projection display device according to the first item,
Provided is a color correction method for a projection display device, wherein the screen color is in the vicinity of white within a predetermined color range.
According to invention of Claim 3,
In the projection display device according to the first item,
A color correction method for a projection display device, wherein when the screen color is within a predetermined color range, the color correction is performed by comparing the measurement value of the first and second color sensors with a reference value. Is provided.
According to invention of Claim 4,
In the projection display device according to the first item,
When the screen color is out of a predetermined color range, the measured value of the first color sensor and the reference value are compared and calculated, and the gain of a plurality of colors is corrected. Is provided.
According to the invention of claim 5,
In the projection display device according to the first item,
There is provided a color correction method for a projection display device, wherein the first and second color sensor means are switched by one color sensor by switching.
According to the invention of claim 6,
In the projection display device according to item 3,
There is provided a color correction method for a projection display device, wherein a three-dimensional color conversion is performed using a three-dimensional lookup table.
According to the invention of claim 7,
In the projection display device according to item 4,
There is provided a color correction method for a projection display device, which uses a one-dimensional lookup table for color conversion for each color.

  According to the image display device of the present invention, the screen color is accurately determined by a sensor or the like that detects external light and reflected light from the screen, and is switched to an optimal color correction mode such as screen color correction priority or external light correction priority. Since color correction is performed, the correction accuracy is improved.

  For example, when the screen is colored, color correction is performed using a luminance correction table (1D-LUT) so that the luminance is not reduced as much as possible.

  In addition, when the screen is white, color correction can be performed more accurately by using a color correction table (3D-LUT) and a luminance correction table (1D-LUT) for correcting the influence of ambient ambient light.

  By accurately discriminating the color of the screen, it is possible to perform color correction optimum for each color mode of wall color correction and external light correction, and to increase the brightness or improve the accuracy depending on the screen color condition.

Configuration diagram of image processing apparatus of the present invention Overall flow chart of color correction of the present invention Diagram of Example 1 for specifying the screen color of the present invention Diagram of Example 2 for specifying the screen color of the present invention Diagram of Example 3 for specifying the screen color of the present invention Example of screen color correction not considering external light of the present invention Sequence diagram of an example of color correction considering external light according to the present invention Diagram showing the spectral sensitivity of the sensor The figure which shows the example of an external light color sensor reference value table A diagram showing an example of a screen color sensor reference value table

[Example 1]
A configuration of an image display apparatus to which the present invention is applied is shown in FIG.

  FIG. 1 is a diagram illustrating main components in the embodiment of the image display apparatus.

  First, each function, image, and control flow will be described.

  Input signal processing 101 receives an input video signal from an image supply device such as a personal computer (PC), a DVD player, a TV tuner, etc. (not shown) as an input signal. When the input signal is an analog signal, it is converted into a digital signal by an analog / digital converter in the input signal processing 101. When the input signal is a digital signal, the OSD 124 displays a menu screen or the like via the switch 125 as a digital signal. And sent to the color correction unit 102.

  In the color correction unit 102, a resolution conversion unit (not shown) converts the video signal into a resolution suitable for the display element 107 made up of red, green, and blue liquid crystal. The color correction unit 102 performs color correction and luminance correction on the video signal whose resolution has been converted.

  The 1D-LUT storage unit 104 of the color correction unit 102 stores a gamma table, a color balance table, and the like mainly as part of the luminance correction information.

  The 3D-LUT storage unit 103 stores a color gamut correction table and a table for independently correcting luminance, saturation, and brightness of six colors as a part of color correction information. .

  Further, the liquid crystal display element driving circuit 105 performs double speed conversion and VT gamma correction necessary for driving the liquid crystal display element 107 to generate a liquid crystal display element driving signal.

  The liquid crystal display element 107 modulated by the video signal receives the light beam emitted from the illumination optical system 106 including the high-pressure mercury lamp, and projects the light beam based on the control by the liquid crystal display element drive signal from the liquid crystal display element drive circuit 105. Send to lens 108.

  The projection lens 108 performs a zoom operation with a zoom lens or the like, and projects the light beam from the liquid crystal display element 107 onto the screen 110 as projection light.

  On the other hand, when calibration for color correction is started, a reference image necessary for color correction is transferred from the reference image output unit 112 via the switch 125 instead of an input signal such as a PC in accordance with an instruction from the control unit 118. Through the OSD 124 for displaying the menu screen and the like, it is sent to the color correction unit 102 and projected onto the screen.

  The reference image is projected, the reflected light from the screen is detected by the screen color sensor 111, and is sent to the image comparison calculation unit 123 as RGB / XYZ values.

  In the image comparison calculation unit 123, the comparison calculation unit 116 compares the screen sensor reference value 121 set and stored in advance at the time of factory shipment and the projected image information 134, and performs color correction to the color correction unit 102. Get the value.

  Next, according to an instruction from the control unit 118, the color correction value is stored in the correction value storage unit 115, and the correction value update determination unit 115 updates the correction data of the color correction unit 102, thereby correcting the color correction. Rebirth is performed.

  Next, the screen and sensor will be described.

  The screen 110 installed in a conference room or the like is simultaneously illuminated by external light such as sunlight incident from the external light illumination 109 or a window together with the projection light, and is affected by color and brightness.

  Furthermore, the screen 110 itself has a slight color width with respect to the ideal white.

  The screen that appears white may be slightly different, and depending on the screen material, it may be blue, yellow, or not white.

  Further, the screen 110 may be a blackboard in an extreme case, or a color partition such as pale blue, pink, and yellow.

  In order to perform color correction in consideration of these effects, the color of the reference image projected on the screen is detected by the screen color sensor 111 as shown in Patent Document 2 (Japanese Patent No. 3755593), and color correction is performed. Is required.

  The screen color sensor 111 and the external light color sensor 130 are composed of a two-dimensional RGB color sensor such as a CCD camera, for example, and detect the entire projection area on the screen, and compare it with the image comparison calculation unit 123 as an RGB value or an XYZ value. It is sent to the calculation means 116.

  The XYZ value is a kind of color standard based on CIE, and the XYZ value can be converted into an RGB value.

  The Y value is a value indicating luminance. That is, the color and brightness of the image can be obtained by obtaining the XYZ values of the projected reference image.

  Similarly, in order to detect the external light characteristic of the external light illumination 109 that has an influence on the color characteristics on the screen, the external light color sensor 130 is used, and the external light comparison unit 131 compares it with the sensor reference value to obtain RGB. Value or XYZ value is sent to the comparison calculation means 116 of the image comparison calculation unit 123.

  The external light comparison unit 131 determines whether or not the screen is colored by comparing the reference value of the reflected light from the screen corresponding to the external light and the reflected light at the time of black projection and the reference value.

  An example of spectral characteristics of the screen color sensor 111 and the external light color sensor 130 is shown in FIG.

  The sensor includes three color sensors 9 (R sensor, G sensor, and B sensor) (not shown), and has sensitivity in each wavelength region of R, G, and B.

  The screen color sensor 111 is arranged so that only the light reflected from the screen (projection surface) 110 of the light projected from the projector can be detected.

  The external light color sensor 130 is arranged so that only the light from the external light illumination can be detected.

  Here, FIGS. 9 and 10 show reference value tables of the external light color sensor and the screen color sensor. The condition parameters are stored in advance as factory adjustments or preset values in a non-volatile memory or the like as a reference value table in which the measured values of each sensor for the reference image to be projected, the reference screen, and non-reference light.

  The ambient light is detected by the ambient light color sensor 130 and compared with the ambient light sensor reference value to identify the ambient light, and at the same time, the detected value is sent to the image comparison calculation unit 123.

  The image comparison calculation unit 123 accurately determines the screen color based on the detection value of the screen color sensor 111 and its reference value, and the detection value of the external light color sensor 130 and its reference value.

  From these detection results, it is judged whether the screen is white, and the color correction accuracy is improved by switching to the optimal correction means such as whether to correct the screen color or to correct the color considering external light correction. There is.

  For example, when the screen is colored, color correction is performed using a luminance correction table (1D-LUT) with only R, G, and B gains so that the luminance is not reduced as much as possible.

  In addition, when the screen is white, color correction can be performed more accurately by using a color correction table (3D-LUT) and a luminance correction table (1D-LUT) for correcting the influence of ambient ambient light.

  By accurately discriminating the color of the screen, it is possible to perform color correction optimal for each color mode of screen color correction and external light correction, and to increase the brightness or improve the accuracy depending on the screen color condition.

  FIG. 2 shows an overall flowchart of color correction according to the present invention.

  In step S1, it is determined whether or not the screen is colored. In step S2, the process branches depending on whether or not the screen is white.

  When the screen is white, color correction (luminance correction 1D-LUT) is performed in step S3 so that the luminance of only the RGB gain and the RGB gamma curve does not decrease as much as possible without considering external light.

  When the screen is other than white, high-precision color correction (luminance correction 1D-LUT and color correction 3D-LUT) is performed simultaneously with screen color correction in consideration of the influence of external light.

  3 and 4 show Example 1 and Example 2 for specifying the screen color of the present invention.

  By operating the menu of the display device, the user can select the screen color, specify the correct screen color without any mistakes, and perform optimum color correction.

  In Example 1 in FIG. 3, the screen color is classified into white and other colors.

  In Example 2 in FIG. 4, the screen colors are classified into white, yellow, green, pink, and blue.

  FIG. 5 shows Example 3 for specifying the screen color of the present invention.

  In step S501, the sensor reference values under necessary conditions are stored in the nonvolatile memory for factory adjustment or the like.

  Examples of conditions include a projection reference image, a reference screen, color, reflectance, and non-reference light.

  Specific examples of the projection reference image include white (gray 100%, black gray 0%, gray 50%), yellow, green, pink, and blue.

  Examples of the reference screen include colored ones such as partitions, blackboards, and materials having different reflectivities.

  Non-standard light includes incandescent bulbs and fluorescent lamps having various color temperatures.

  In step S502, external light is detected, and in step S503, a reference value of reflected light with respect to the external light is read. In step S504, black light is projected, and the reflected light from the outside light reflected on the screen is detected.

  In step S505, it is determined from these detection results whether the screen color is finally within an allowable range as white, and is specified in steps S506 and S507.

  FIG. 5 shows an example of screen color correction of the present invention that does not take into account external light.

  The gain of each color of RGB is adjusted according to the LUT conversion table as shown in Table 1.

  Since the calculation table is also simple, color correction can be performed at high speed. For example, color correction that minimizes the projection luminance can be performed.

  FIG. 7 shows a sequence diagram of a color correction example in consideration of external light according to the present invention.

  The values of both the external light sensor and the screen sensor are detected while projecting the reference image so that the case where the external light affects the screen and the screen is also colored can be dealt with. Compare and calculate detailed sensor detection and color correction values. With these operations, the correction values of the luminance correction value 1D-LUT and the color correction value 3D-LUT are obtained and updated and set in the color correction unit, so that more accurate color correction is possible.

  In the example of FIG. 1, the screen sensor and the external light color sensor have been described independently, but it is also possible to configure the two sensors as one and switch the detection target between the external light and the screen. .

  As described above, whether the screen is colored or not is set accurately using an external light sensor or menu operation, etc., so that it is optimal for screen color correction and color correction considering external light. Since the color correction is performed by switching to the correct color correction mode, the correction accuracy is improved.

  If the screen is colored, it is possible to perform signal processing with as little luminance reduction as possible by simply adjusting the RGB gain.

  If a white screen can be detected, the color correction value 3D-LUT and the luminance correction value 1D-LUT can be calculated and updated as accurately as possible in consideration of external light, and the correction accuracy can be improved.

  By accurately determining the color of the screen, color correction that is optimal for each color mode of screen color correction and color correction considering external light is performed, and brightness is increased depending on the screen color conditions, or the accuracy of color correction is improved. Can do.

101 Input signal processing color correction unit 3D-LUT storage unit 1D-LUT storage unit 105 Display element drive circuit 106 Illumination optical system 107 Display element 108 Projection lens 109 Ambient light illumination 110 Screen 111 Screen color sensor 112 Reference image output means correction update determination Means correction value storage means Comparison calculation means control means (CPU)
Program memory screen sensor reference value storage means Image comparison operation section switch 130 External light color sensor 131 External light comparison section 132 External light sensor reference value storage means 133 Comparison means

Claims (7)

In the projection display device having a color correction function of the display color by detecting the reflected light of the screen and changing the characteristics of the image according to the result,
First color sensor means for detecting different wavelength regions from the reflected light of the screen;
Reference value storage means for storing a value obtained by detecting screen reflected light as a reference by the color sensor means;
Second color sensor means for detecting different wavelength regions from light other than projection light; and
A reference value storing means for storing a value obtained by detecting external light as a reference by the color sensor means;
Means for determining that the screen color is within a predetermined color range by comparing the measurement value and the reference value of the first and second color sensors;
A color correction method for a projection display device, wherein different color correction functions are executed depending on whether the color is within or outside a predetermined color range. The color correction method for a projection display device according to claim 1, wherein the screen color is in the vicinity of white within a predetermined color range. 2. The projection according to claim 1, wherein when the screen color is within a predetermined color range, the color correction is performed by comparing and calculating the measurement values of the first and second color sensors and the reference value. Display device color correction method. 2. The projection according to claim 1, wherein when the screen color is outside a predetermined color range, the measurement value of the first color sensor is compared with the reference value to correct the gains of the plurality of colors. Display device color correction method. The color correction method for a projection display device according to claim 1, wherein the first and second color sensor means are switched by one color sensor. In the projection display device according to item 3,
4. The color correction method for a projection display device according to claim 3, wherein a three-dimensional lookup table is used for the color conversion of the three colors. 5. The color correction method for a projection display device according to claim 4, wherein a one-dimensional lookup table is used for color conversion for each color.