JP2019204017A - Color correction method of image projection device - Google Patents

Abstract

To provide correction processing determination means that switches color correction processing by a projection surface, and an effect of environment light and a projection image without being limited to the projection environment in an image projection device having a function detecting reflection light from a projection surface and performing the color correction processing of the projection surface.SOLUTION: An image projection device, which displays videos on a projection surface 1, has: color measurement means 107 that detects spectrum information on the projection surface 1; range-finding means 108 that detects a distance from the image projection device to the projection surface 1; first computation means 109 that computes a spectrum of projection light; and correction processing determination means 113 that switches a color correction method on the basis of a first color measurement result detected by the color measurement means when the image projection device is at a time of projection, a second color measurement result detected by the color measurement means when the image projection device is at a time of non-projection, and range-finding information detected by the range-finding means 108. In accordance with a determination result of the correction processing determination means, a wall color correction or an external light correction is made.SELECTED DRAWING: Figure 1

Description

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

  The image projection device is used when the projection surface is colored or in an environment with ambient light such as lighting or sunlight, but the projected image is colored in consideration of the color of the actual projection surface and the influence of ambient light. It is necessary to correct. Conventionally, the color of the projection surface is detected using a color sensor, and the presence or absence of ambient light is judged by comparing the brightness of the ambient light or the color temperature with a reference table recorded on the projection surface of a certain color. Switching between correction and wall color correction.

JP 2012-248910 A

  In the method disclosed in Patent Document 1, the color sensor is used to determine whether the screen is colored or ambient light is present, and the screen color correction mode and the external light correction mode are switched. This judgment is based on a reference value measured with several reference ambient light with different brightness and color temperature on a reference screen of several colors such as white, green and yellow. The values are compared. However, in an actual projection environment, there are numerous materials and colors for the projection surface, and there are many brightnesses and colors of ambient light. Therefore, the actual environment is not always the same as the determination environment, and the correction mode may be switched incorrectly. Therefore, the image projection apparatus described in Patent Document 1 in which the influence of such a projection environment is not taken into account cannot cope with the types of screen colors and ambient light colors, and thus there is a limit in improving switching accuracy. there is a possibility.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image projection apparatus that can perform highly accurate color correction determination regardless of the type of screen or ambient light.

The image projection apparatus of the present invention is an image projection apparatus for displaying and displaying an image on a projection surface,
A colorimetric means for detecting spectroscopic information on the projection surface;
Ranging means for detecting the distance between the image projection device and the projection surface;
First computing means for computing the spectrum of the projected light;
The first color measurement result detected by the color measurement means when the image projection apparatus is not projecting, the second color measurement result detected by the color measurement means when the image projection apparatus is projected, and the distance measurement detected by the distance measurement means Correction processing determination means for switching the color correction method based on the information;
Have
According to the determination result of the correction processing determination means, wall color correction or external light correction is performed.

  According to the image projection apparatus of the present invention, it is possible to select an optimal color correction process even for ambient light having an unknown spectrum or a reflection spectrum of a projection surface.

It is a block diagram of the image projection apparatus of one Embodiment. It is an example of the spectrum which the colorimetric sensor of one Embodiment measures. It is a flowchart of one embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Example 1
FIG. 1 is a block diagram showing an embodiment of the present invention. The image projection apparatus is composed of a liquid crystal projector 2 that projects an image onto a projection surface 1.

  The image projection apparatus receives an input video signal such as DVI, HDMI (registered trademark), or analog from an image supply apparatus such as a personal computer (PC) or video equipment (not shown) by the input IF unit 100. Various input video signals such as WXG, SXGA, and WUVGA received are converted into digital video signals in a predetermined format by the input signal processing unit 101. The panel driving unit 102 generates a liquid crystal panel driving signal by performing resolution conversion processing, frame rate conversion processing, and the like suitable for driving the liquid crystal panel 103 as an image display element on the digital video signal. The color correction processing unit 104 corrects the digital video signal.

  The liquid crystal panel 103 is illuminated by light emitted from an illumination optical system 105 including a light source such as a high-pressure mercury lamp and a laser element, and modulates incident light based on control by a liquid crystal panel drive signal from the panel drive unit 102. In general, the liquid crystal panel 103 is composed of three pieces for red, green, and blue, but the difference is irrelevant to the present invention, and thus the description thereof is omitted. The light beam emitted from the liquid crystal panel 103 is projected from the projection lens 106 onto the projection surface 1 as projection light L1.

  The colorimetric sensor 107 is a spectroscopic sensor, has sensitivity in a plurality of different wavelength regions, and detects a visible spectrum (380 to 780 nm) from reflected light from the projection surface. The colorimetric sensor 107 is composed of an optical system (not shown) so that only the spectrum of the reflected light from the projection surface 1 can be detected. Note that the detection range of the colorimetric sensor 107 is not limited to the entire projection surface, and may be measured by being divided into center positions or areas.

  Now consider the projection environment of the projector. The spectral reflectance of the projection surface 1 is R1. The value A detected by the colorimetric sensor 107 when ambient light that is ambient light such as illumination or sunlight is present in a non-projected state is the value that the ambient light L2 is reflected by the projection surface 1 at R1. Become. When the projection light is emitted from the projector, the value B detected by the colorimetric sensor 107 is reflected by the projection surface 1 in the same way as the ambient light, so the projected light L1 and the ambient light L2 are reflected by R1, respectively. It becomes the sum of light.

  Here, the light intensity for each wavelength of the projection light L1 is obtained from the following conditions. First, the distance information C is acquired by the distance measuring sensor 108 and passed to the projection light calculation unit 109. Next, the projection light calculation unit 109 reads the projection light table 111 based on predetermined video data stored in the nonvolatile memory 110. At this time, the projection light table 111 updates values from light source deterioration information, zoom ratio, color correction information set by the user, image mode, lens information (interchangeable lens), and the like. Based on the acquired distance information C and the value of the projection light table 111, the projection light calculation unit 109 calculates the light intensity of the projection light L1.

  FIG. 2 is an example of light existing in the projection environment. 2A shows the spectrum of the projection light L1, FIG. 2B shows the spectrum of the ambient light L2, and FIG. 2C shows an example of the spectral reflectance R1 of the projection surface 1. FIG. In this case, examples of the values of the spectra A and B actually detected by the colorimetric sensor 107 are (d) and (e). (f) is a spectrum L1 × R1 that can be detected when projected in the absence of ambient light. In the case of (e), it is assumed that the ambient light is sufficiently bright so that the influence on the projection light cannot be ignored. It can be seen from A and B detected at this time that the spectrum of the ambient light L2 and the spectral reflectance R1 of the projection surface 1 cannot be distinguished. That is, it cannot be distinguished whether the detection light in this case depends on the object color (R1) of the projection surface or the light source color (L2 spectrum) of the ambient light.

  This problem will be explained. When the detection light depends only on the object color on the projection surface as shown in FIG. 3 (f), it is sufficient to simply adjust the R, G, and B gain values of the projection light. However, for example, when depending on the light source color as shown in FIG. 3 (e), ambient light may exist in a range (650 nm or more) other than the light of the projection light. Further, since the offset is applied by the ambient light, the contrast is lowered. Therefore, when the light source color becomes a problem, not only gain correction but also color correction such as color gamut correction and color temperature correction is required without reducing luminance as much as possible. Therefore, a means for discriminating these and selecting an appropriate correction method is required.

Here, the relation between A and B is expressed as follows.
A (λ) = L2 (λ) × R1 (λ) (2a)
B (λ) = (L1 (λ) + L2 (λ)) × R1 (λ) (2b)
L1 (λ): Projected light output at wavelength λ
L2 (λ): Ambient light output at wavelength λ
R1 (λ): Spectral reflectance of projection surface at wavelength λ
A (λ): Output at the wavelength λ detected during non-projection
B (λ): Output at wavelength λ detected during projection

  In the above equation, the light intensity is calculated by dividing the wavelength unit by Δλ (for example, every 20 nm). Δλ depends on the resolution of the colorimetric sensor. Here, in the above two formulas (2a) and (2b), if the light intensity of the projection light L1 is known, the variable is only binary and R1 and L2 can be calculated.

In this case, transform the expression
L2 (λ) = A (λ) / (B (λ) -A (λ)) L1 (λ) (2c)
R1 (λ) = (B (λ) -A (λ)) / L1 (λ) (2d)
It becomes.

  Therefore, information on the light intensity of the projection light L1 is necessary to correct with high accuracy. Here, since the light intensity attenuates in inverse proportion to the square of the distance, the distance information C is acquired by the distance measuring sensor 108 as described above. Here, the distance measuring means is not limited, and the user may input distance information.

  Next, the projection light calculation unit 109 calculates using the projection light table 111 stored in the non-volatile memory 110 and the distance information C to calculate L1. Here, the projection light table 111 is an output table obtained by the colorimetric sensor 107 when predetermined reference white projection light is projected onto the reference projection surface from several reference distances, and is measured in an adjustment process in a factory or the like. This value is stored in the nonvolatile memory 110. Although described as an output table, it may be a coefficient of an approximate function. In order to perform calculation with higher accuracy, data is updated from values such as light source deterioration information, zoom ratio, color correction information set by the user, image mode, and lens information.

  Next, the detection data calculation unit 112 uses the projection light L1 calculated by the projection light calculation unit 109 and the values A and B detected by the colorimetric sensor 107, and the spectrum and light intensity of the ambient light L2 for each wavelength. Each of the reflection spectra R1 is calculated. Here, the above-described equations (2c) and (2d) are used as the calculation method.

  Next, the correction processing method determination unit 113 determines the correction method by comparing the calculated spectrum shape and light intensity of the projection light L1, the ambient light L2, and the reflection spectrum R1 of the projection surface. At this time, parameters necessary for correction are also calculated and passed to the color correction processing unit 104.

  For example, if the influence of ambient light is small and only the reflection spectrum R1 of the projection surface contributes to the appearance, calculate the parameter of which wavelength of reflection on the projection surface is large, and 1D- with only R, G, B gain Select the color correction method (ambient light correction) using the LUT brightness correction table. If the influence of the ambient light L2 is greater than or equal to the reference value, calculate a parameter indicating which wavelength component of the ambient light L2 is large, and include 3D- including color gamut correction and color temperature correction to correct the influence of the ambient light A color correction method (wall color correction) is selected based on the LUT color correction table and the R, G, B 1D-LUT luminance correction table described above.

  The color correction processing unit 104 has a plurality of correction processing methods and reference chromaticities inside, and based on the correction processing method and parameters determined by the correction processing determination unit 113, correction processing is performed so that the digital video signal has the reference chromaticity. To do.

FIG. 3 is a flowchart of automatic color correction according to this embodiment.
First, in step S01, distance information C with respect to the projection surface is acquired. As described above, the distance information C is measured by the distance measuring sensor 108. Alternatively, the user inputs on the menu screen.

  In step S02, the projection light table 111 stored in the nonvolatile memory 110 is read out. At this time, as described above, the projection light table 111 updates values from the light source deterioration information, the zoom ratio, the color correction information set by the user, the image mode, the lens information, and the like.

  In step S03, the spectrum and light intensity of the projection light L1 are calculated based on the acquired distance information C and the value of the projection light table 111. When only distance information is used, the value shown in FIG. 2A can be derived simply by calculating a value inversely proportional to the square of the distance for the stored reference projection light table. When information such as light source deterioration information is used, the calculation is performed in consideration of the fact that the spectrum shape changes in accordance with the deterioration information or the like.

  Next, in step S04, when the projector is in the projection state, the projection is stopped or changed to the black projection state, and the colorimetric sensor 107 is driven to detect the spectrum A. At this time, the accumulation time of the colorimetric sensor 107 is controlled by a microcomputer (not shown). In order to avoid saturation in the next step S05, the accumulation time is determined based on the value of the projection light L1 obtained in step S03.

  In step S05, the reference white projection light is projected from the projection lens 106, and the colorimetric sensor 107 detects the spectrum B at the time of projection. In order to compare the light intensities, the accumulation time is the same as that in step S04.

  In the next step S06, if the colorimetric sensor is saturated in the measurement of B, the accumulation time is shortened in S06a and the process returns to S04. In the next step S07, if any one of the R, G, and B wavelength bands adjustable by the projector cannot be detected from the B value, color correction cannot be performed, so a warning display is issued in S07a and the process ends. . This is because, for example, color correction cannot be performed on the projection surface that reflects only B because R and G do not exist.

  Next, in step S08, the spectrum shape and light intensity of ambient light L2 are calculated from the obtained values A and B based on equation (2c), and in step S09, the calculated L2 value and equation (2d) are used to calculate the projection surface. The reflection spectrum R1 is calculated. Thereby, (b) and (c) in FIG. 2 can be obtained.

  Step S10 is an operation of the correction processing method determination unit 113, and determines a correction method based on the obtained spectrum information. First, it is analyzed from the information of the ambient light L2 obtained in S08 whether the luminance is larger than the reference value. This reference value is 30% or less with respect to the luminance of the projection light L1. Specifically, a color matching function is applied to each of the spectral information of L1 and L2 in FIG. 2 and converted into XYZ color space coordinates for determination. If it is equal to or greater than the reference value, the process proceeds to step S11a for performing ambient light correction, and if it is equal to or less than the reference value, the process proceeds to step S11b for performing wall color correction. The reference value is not limited to 30% or less.

  Step S11a is an operation of an ambient light correction processing unit (not shown) in the color correction processing unit 104. In S11a, first, which wavelength component of L2 is large is analyzed. For example, in L2 of FIG. 2, there are sharp peaks near 450 nm (blue) and 550 nm (green), so it is necessary to raise the G and B gains. There is also light in the range of 650 nm or more. Therefore, since the R, G, and B gains alone cannot be used, it is necessary to adjust parameters such as color gamut correction, γ adjustment, and color temperature correction. These items are stored in a memory (not shown) in the correction processing method determination unit 113.

  Next, B is converted into the XYZ color space to obtain chromaticity, and the above-mentioned parameter value for ambient light correction is determined in order to match the target chromaticity. However, since the contrast is reduced by ambient light, correction is made so that it does not decrease as much as possible. For this reason, if the luminance decreases when the target chromaticity is corrected, an allowable color difference is set and the luminance is prioritized. Further, the spectral reflectance R1 of the projection surface is analyzed, and the R, G, and B gains are changed according to the spectral reflectance so that the ambient light parameter does not collapse.

  Step S11b is an operation of a wall color correction processing unit (not shown) in the color correction processing unit 104. In step S11b, since the observed image is in the state shown in FIG. 2 (f), the R, G, B gain is simply changed in accordance with the reflectance of each wavelength. Here, the correction processing method is determined by selecting one of the two methods. However, the correction processing method is not limited to the ambient light correction and the wall color correction, and may be determined in an analog manner, or may have a plurality of correction processing methods.

  In this embodiment, the colorimetric sensor 107 is a spectroscopic sensor. However, for example, a color sensor or a camera may be used, and the sensor is not limited.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1: Projection surface
2: LCD projector
104: Color correction processor
107: Colorimetric sensor
108: Distance sensor
109: Projection light calculation unit
111: Projection light table
112: Detection data calculator
113: Correction processing method determination unit
L1: Projection light
L2: Ambient light
R1: Spectral reflectance of projection surface
A: Spectrum detected by the colorimetric sensor 107 during non-projection
B: Spectrum detected by the colorimetric sensor 107 during projection

Claims (8)

An image projection apparatus for displaying an image on a projection surface,
A colorimetric means for detecting spectral information of the projection surface;
Ranging means for detecting the distance between the image projection device and the projection surface;
First computing means for computing the spectrum of the projected light;
The first color measurement result detected by the color measurement means when the image projection apparatus is not projecting, the second color measurement result detected by the color measurement means when the image projection apparatus is projected, and the distance measurement detected by the distance measurement means Correction processing determination means for switching the color correction method based on the information;
Have
An image projection apparatus that performs wall color correction or external light correction according to a determination result of a correction processing determination unit.   The reference table for calculating the spectrum of the projection light, wherein the first calculation means calculates the spectrum of the projection light based on the reference table and the distance measurement information. The image projection apparatus described.   The image projection apparatus according to claim 2, wherein the reference table stores lamp deterioration information and lens zoom ratio information, a user-set color correction status, an image mode, and lens information, and updates the reference table.   Measurement value storage means for storing the first and second color measurement results, and an environment using the spectrum of the projection light obtained by the first calculation means and the first and second color measurement results 4. The image projection apparatus according to claim 1, further comprising a second computing unit that computes a light spectrum and a reflection spectrum of the projection surface. 5.   The correction processing determination means switches the color correction method according to the spectrum shape and light intensity of the projection light and the ambient light obtained from the first and second calculation means, and the reflection spectrum of the projection surface. The image projection apparatus according to claim 4.   The image projection apparatus according to claim 1, wherein the distance measuring unit uses a distance measuring sensor.   The image projection apparatus according to claim 1, wherein the distance measurement information is input by a user from a menu screen.   The image projection apparatus according to claim 1, wherein the color measurement unit is performed by one sensor.

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