JP2010152265A - Image processor, image display device and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor, an image display device, and an image processing method, improving the view of image details regardless of use environment. <P>SOLUTION: This image processor, which corrects an image signal supplied to an image display section, includes: an luminance component correction quantity calculation section which calculates the correction quantity of luminance component of the image signal according to the viewing environment only for the image signal within a given range of luminance levels in a given spatial frequency band; and a luminance component correction section which corrects the luminance quantity of the image signal using the correction quantity calculated by the luminance component correction quantity calculation section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing device, an image display device, and an image processing method.

In recent years, there has been a demand for an image display device having a wider color gamut due to higher quality of content images. However, even in an image display device that adopts advanced color reproduction technology, when used in a bright environment such as illumination, the color reproduction range becomes narrow due to reflection of illumination, etc. It often becomes an image.

Therefore, for example, a technique in which the brightness of the environment in which the image display device is used is measured by a sensor and the processing for enhancing the saturation of the image according to the brightness of the environment using the measurement result of the sensor is performed. 1 is disclosed.

In Patent Document 1, the brightness and color of external illumination reflected on an image display device is measured by a sensor, the color correction table is rewritten so as to cancel the influence, and color correction for an image signal is performed according to the rewritten color correction table. Techniques for performing are disclosed.

JP 2002-91415 A

However, in the technique disclosed in Patent Document 1, since uniform correction is performed on the entire screen, the brightness and saturation contrast of the image can be improved, but the details of the image are expressed in a crushed manner. There is a problem of end.

The present invention has been made in view of the technical problems as described above, and one of its purposes is as follows.
An object of the present invention is to provide an image processing device, an image display device, and an image processing method that improve the appearance of image details regardless of the use environment.

In order to solve the above problems, the present invention is an image processing apparatus that corrects an image signal supplied to an image display unit, and only for an image signal in a given luminance level range in a given spatial frequency band. The luminance component correction amount calculation unit that calculates the correction amount of the luminance component of the image signal according to the viewing environment, and the luminance amount of the image signal using the correction amount calculated by the luminance component correction amount calculation unit The present invention relates to an image processing apparatus including a luminance component correction unit that corrects components.

According to the present invention, since the luminance component of the image signal is corrected only for the image signal in the given luminance level range in the given spatial frequency band, uniform correction is performed on the entire screen. Even when the dark part and the bright part are mixed, the image signal can be corrected so that the details of both the dark part and the bright part can be expressed. In addition, since the correction amount of the luminance component is calculated according to the viewing environment, it is possible to provide an image processing apparatus that improves the appearance of image details regardless of the usage environment.

In the image processing apparatus according to the present invention, the luminance component correction amount calculation unit can calculate the correction amount using a luminance ratio between external light and output light from the image display unit as the visual environment.

According to the present invention, since the luminance ratio between the external light and the output light of the image display unit is adopted as the visual environment, the image processing apparatus improves the appearance of image details with a simple configuration regardless of the usage environment. Will be able to provide.

The image processing apparatus according to the present invention further includes a signal extraction circuit that extracts a signal in the spatial frequency band from the luminance component of the image signal, and the luminance component correction amount calculation unit sets the luminance component level of the image signal to a level. A luminance gain calculation circuit for calculating a corresponding luminance gain, based on the spatial frequency band signal extracted by the signal extraction circuit, the luminance gain calculated by the luminance gain calculation circuit, and the luminance ratio; Thus, the correction amount of the luminance component can be calculated.

According to the present invention, a signal in a given spatial frequency band can be extracted by the signal extraction circuit, and a signal in the level range of the given luminance component can be specified by the luminance gain calculation circuit. Thus, with a simple configuration, the luminance component of the image signal can be corrected only for the image signal in a given luminance level range in a given spatial frequency band.

The image processing apparatus according to the present invention further includes a multistage filter circuit that extracts the spatial frequency band signal from the luminance component of the image signal, and the luminance component correction amount calculation unit is provided for each output of the multistage filter circuit. A plurality of tables for outputting a gain corresponding to the level of the luminance component before correction and the luminance ratio, and provided for each output of the multistage filter circuit, and constitutes the outputs of the multistage filter circuit and the plurality of tables. A plurality of multipliers for multiplying the output of each table; and an adder for adding the multiplication results of the multipliers constituting the plurality of multipliers, and using the output of the adder as a correction amount for the luminance component Can be calculated.

According to the present invention, when correcting the luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band, a plurality of filters provided for each output of the multistage filter circuit are provided. Since the gain is output by the table, in addition to the above effect, the number of multipliers can be reduced, and the power consumption and the cost can be reduced.

The image processing apparatus according to the present invention further includes a signal extraction circuit that extracts a signal in the spatial frequency band from the luminance component of the image signal, and the luminance component correction amount calculation unit outputs the output of the signal extraction circuit and the signal before correction. A table for outputting a correction amount of the luminance component corresponding to the level of the luminance component and the luminance ratio.

According to the present invention, when correcting a luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band, the correction amount of the luminance component is output from the table. Therefore, in addition to the above effect, the multiplier can be eliminated, and a significant reduction in power consumption and cost can be achieved.

The image processing apparatus according to the present invention further includes a frequency analysis unit that analyzes a spatial frequency of the luminance component of the image signal, and the luminance component correction amount calculation unit determines the correction amount of the luminance component of the image signal as the luminance It can be calculated according to the ratio and the analysis result of the frequency analysis unit.

According to the present invention, the spatial frequency of the luminance component of the image signal is analyzed, and the luminance component of the image signal is converted into the luminance ratio only for the image signal in the given luminance level range in the given spatial frequency band. Since the correction amount is calculated according to the analysis result of the spatial frequency of the luminance component and the luminance component is corrected using the correction amount, the dark portion and the bright portion are not corrected without performing uniform correction on the entire screen. Even in the case where the part is mixed, the image signal can be corrected so that the details of both the dark part and the bright part can be expressed. Furthermore, since it is possible to distinguish the details of the dark portion of the image from the luminance noise, it is possible to avoid a situation where the luminance noise is emphasized together with the details of the dark portion.

In the image processing apparatus according to the present invention, the frequency analysis unit includes a high-frequency component extraction unit that extracts a given high-frequency component of the luminance component of the image signal, and the luminance component correction amount calculation unit includes the high-frequency component. A frequency gain calculation unit that calculates a frequency gain corresponding to the high-frequency component extracted by the extraction unit, the luminance component in a given luminance level range in the spatial frequency band, and the frequency gain calculation unit The correction amount of the luminance component can be calculated based on the frequency gain and the luminance ratio.

According to the present invention, a high-frequency component of a luminance component is extracted, based on a frequency gain corresponding to the high-frequency component, a luminance component in a given luminance level range in a given spatial frequency band, and the above-described luminance ratio. In addition to the effects described above, a simple process is used to distinguish between dark details and luminance noise and avoid the situation where luminance noise is emphasized together with dark details. become able to.

Further, in the image processing device according to the present invention, the luminance component correction amount calculating unit includes a luminance gain calculating unit that calculates a luminance gain corresponding to a level of the luminance component of the image signal, and the signal of the spatial frequency band; The correction amount of the luminance component can be calculated based on the frequency gain, the luminance gain calculated by the luminance gain calculation unit, and the luminance ratio.

According to the present invention, a signal in a level range of a given luminance component can be specified by a luminance gain for a signal in a given spatial frequency band. The luminance component of the image signal can be corrected according to the use environment only for the luminance component in the given luminance level range in the given spatial frequency band.

The image processing apparatus according to the present invention may further include a signal extracting unit that extracts the spatial frequency band signal from the luminance component of the image signal.

According to the present invention, in addition to the above effects, components in a given spatial frequency band can be extracted from luminance components in a given luminance level range with a simple configuration.

In the image processing apparatus according to the present invention, the frequency analysis unit includes a luminance noise removal unit that removes a given luminance noise component from the luminance component of the image signal, and the luminance component correction unit calculates the correction amount. The luminance component of the image signal from which the luminance noise component has been removed by the luminance noise removing unit can be corrected.

According to the present invention, since the luminance component from which the luminance noise has been removed is corrected using the correction amount calculated by the luminance component correction unit, in addition to the above effects, the dark portion and the bright portion are corrected. It is possible to perform high-precision correction of an image signal that expresses both details and distinguishes the detail in the dark portion of the image from the luminance noise.

In the image processing apparatus according to the present invention, xy before and after correction by the luminance component correction unit.
A color difference component correction unit that corrects the color difference component of the image signal so that the value of chromaticity does not change may be included.

According to the present invention, since the chrominance component is corrected in conjunction with the correction of the luminance component so that the value of the xy chromaticity before and after the correction of the luminance component does not change, in addition to the above effect, It is possible to avoid a situation in which the chromaticity changes and the overall color tendency of the screen changes, and it is possible to maintain the color tendency of the entire screen when expressing image details.

In the image processing apparatus according to the present invention, the correction amount of the color difference component of the image signal is calculated based on the luminance component of the image signal before and after correction by the luminance component correction unit so that the value of the xy chromaticity does not change. A color difference component correction amount calculation unit that performs correction of the color difference component of the image signal using the color difference component correction amount calculated by the color difference component correction amount calculation unit. .

According to the present invention, the chrominance component is corrected according to the correction amount of the luminance component in conjunction with the correction of the luminance component of the image signal, so that the value of the xy chromaticity before and after the correction of the luminance component is changed. Therefore, it is possible to correct an image signal that can express details of a dark part and a bright part of an image.

The image processing apparatus according to the present invention further includes an adjustment parameter storage unit that stores the adjustment parameter of the color difference component, wherein the luminance component before correction is Yin and the luminance component after correction is You.
t, where b is the adjustment parameter, the color difference component correction unit is (1-b × (1-Yo
ut / Yin)) as a color difference gain, the color difference component of the image signal can be corrected by multiplying the color difference component by the color difference gain.

According to the present invention, the correction of the color difference component linked to the correction of the luminance component of the image signal can be realized by a simple process.

According to another aspect of the present invention, there is provided an image display device that displays an image based on an image signal, the image processing device according to any one of the above-described methods for correcting the image signal, and the image signal corrected by the image processing device. The present invention relates to an image display device including an image display unit that displays an image.

According to the present invention, it is possible to provide an image display apparatus that improves the appearance of image details regardless of the use environment.

The image display device according to the present invention may include a sensor for measuring the luminance of the output light of the image display unit and the luminance of the external light.

According to the present invention, it is possible to provide an image display device that improves the appearance of the details of an image regardless of the use environment at a low cost by the integrated sensor.

The present invention is also an image processing method for correcting an image signal supplied to an image display unit, wherein the luminance of the image signal is only applied to an image signal in a given luminance level range in a given spatial frequency band. A luminance component correction amount calculating step for calculating a component correction amount according to a visual environment, and a luminance component for correcting the luminance component of the image signal using the correction amount calculated in the luminance component correction amount calculation step. And an image processing method including a correction step.

According to the present invention, since the luminance component of the image signal is corrected only for the image signal in the given luminance level range in the given spatial frequency band, uniform correction is performed on the entire screen. Even when the dark part and the bright part are mixed, the image signal can be corrected so that the details of both the dark part and the bright part can be expressed. Moreover, since the correction amount of the luminance component is calculated according to the luminance ratio between the external light and the output light of the image display unit, it is possible to provide an image processing method that improves the appearance of image details regardless of the use environment. become.

In the image processing method according to the present invention, the luminance component correction amount calculating step can calculate the correction amount using a luminance ratio between external light and output light from the image display unit as the visual environment.

According to the present invention, since the luminance ratio between the external light and the output light of the image display unit is adopted as the viewing environment, an image processing method for improving the appearance of image details in a simple manner regardless of the use environment Will be able to provide.

The image processing method according to the present invention further includes a frequency analysis step of analyzing a spatial frequency of the luminance component of the image signal, and the luminance component correction amount calculating step sets the correction amount of the luminance component of the image signal as the luminance It can be calculated according to the ratio and the analysis result of the frequency analysis step.

According to the present invention, the spatial frequency of the luminance component of the image signal is analyzed, and the luminance component of the image signal is converted into the luminance ratio only for the image signal in the given luminance level range in the given spatial frequency band. Since the correction amount is calculated according to the analysis result of the spatial frequency of the luminance component and the luminance component is corrected using the correction amount, the dark portion and the bright portion are not corrected without performing uniform correction on the entire screen. Even in the case where the part is mixed, the image signal can be corrected so that the details of both the dark part and the bright part can be expressed. Furthermore, since it is possible to distinguish the details of the dark portion of the image from the luminance noise, it is possible to avoid a situation where the luminance noise is emphasized together with the details of the dark portion.

In the image processing method according to the present invention, the luminance ratio may be calculated based on luminance when the image display unit displays a black image and luminance when the image display unit displays a white image. it can.

  According to the present invention, the luminance ratio can be calculated by a simple method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

Hereinafter, a projector will be described as an example of the image display device according to the present invention, but the image display device according to the present invention is not limited to the projector.

[Embodiment 1]
FIG. 1 is a block diagram showing a configuration example of an image display system according to the first embodiment of the present invention.

The image display system 10 includes a projector (an image display device in a broad sense) 20 and a screen SCR. The projector 20 modulates light from a light source (not shown) based on the input image signal, and displays the image by projecting the modulated light onto the screen SCR.

The projector 20 includes an image processing unit 30 (an image processing device in a broad sense) and a projection unit 100.
(An image display unit in a broad sense), a sensor 300, and a correction intensity calculation unit 310 are included. In FIG. 1, the sensor 300 and the correction intensity calculation unit 310 are illustrated as being built in the projector 20, but at least one of the sensor 300 and the correction intensity calculation unit 310 may be provided outside the projector 20. Alternatively, at least one of the sensor 300 and the correction intensity calculation unit 310 may be incorporated in the image processing unit 30 or the projection unit 100.

The sensor 300 measures the luminance in the projection area of the usage environment (ambient light, external light) of the projector 20 and the maximum output luminance of the projection unit 100. Such a function of the sensor 300 is realized by a known measuring device such as a so-called image sensor or luminance meter. Based on the luminance measured by the sensor 300, the correction strength calculation unit 310 calculates the correction strength HS of the input image signal by the image processing unit 30 and outputs the correction strength HS to the image processing unit 30.

The image processing unit 30 uses the correction intensity HS from the correction intensity calculation unit 310 to input the input image signal so that the details of the dark part and the bright part of the display image can be expressed without affecting the luminance area that is not to be corrected. The corrected image signal is output to the projection unit 100. The projection unit 100
The light modulated based on the image signal from the image processing unit 30 is projected onto the screen SCR.

FIG. 2 is an explanatory diagram of the gradation correction processing performed in the image processing unit 30 of FIG. In FIG. 2, the horizontal axis represents the horizontal position of the image and the vertical axis represents the luminance level as the characteristics of the image represented by each image signal during gradation correction processing.

The input image IMGin is, for example, an image having a low luminance (low gradation) on the left side and a high luminance (high gradation) on the right side, and has a small gradation change even in a low luminance region, and in a high luminance region. Also have a slight gradation change. Signal extracting means L1, of the luminance component of the image signal of the input image IMGin, extracts a signal Y _H of the luminance component of the predetermined spatial frequency band. In Figure 2, corresponding to the spatial frequency is set gain, signal extracting means L1 are extracts a signal Y _H of the luminance components of the gain is large spatial frequency band.

Further, the luminance gain calculating means G1 calculates a gain coefficient g (luminance gain coefficient. In a broad sense, a luminance gain. The same applies hereinafter) corresponding to the level of the luminance component of the image signal of the input image. In FIG. 2, the luminance gain calculating means G1 calculates a gain coefficient g that becomes large in a region where the luminance component level is low and becomes almost zero in a region where the luminance component level is high.

As a result, the multiplier M1 generates a signal gY _H obtained by multiplying the gain coefficient g calculated for the signal Y _H extracted by the signal extracting unit L1 by the brightness gain calculating unit G1. The signal gY _H is a signal corresponding to the correction amount of the luminance component of the input image signal. The adder A1 adds the luminance signal Yin and the signal gY _H of the input image signal, and outputs a luminance signal Yout constituting the image signal after the gradation correction.

In the first embodiment, the detail emphasis process is varied depending on the correction strength corresponding to the usage environment of the projector 20 in any of the processes of FIG.

FIG. 3 is a diagram for explaining the operation of the image processing unit 30 in FIG. In FIG. 3, the vertical axis represents the luminance component of the input image signal, and the horizontal axis represents the spatial frequency of the luminance component.

The image processing unit 30 in FIG. 1 calculates only the correction amount of the luminance component of the image signal in the spatial frequency band Far (a given spatial frequency band) according to the use environment (viewing environment) of the projector 20, and the correction is performed. The luminance component of the image signal is corrected using the quantity. More specifically, the image processing unit 30 uses, for example, external light and the projection unit 10 of the projector 20 as a use environment (viewing environment) of the projector 20.
A luminance ratio of 0 output light is adopted. Then, the image processing unit 30 outputs a signal in a given level range Yar of the luminance component Yin of the input image signal calculated by the luminance gain calculating unit G1 in the spatial frequency band Far extracted by the signal extracting unit L1 (FIG. 3). Then the range Sar
) Is corrected according to the luminance ratio. As a result, regardless of the usage environment,
A given level range of the luminance component Yin of the input image signal, which is the spatial frequency band Far extracted by the signal extraction unit L1 and is calculated by the luminance gain calculation unit G1, without changing the overall luminance trend. Only Yar can change the luminance component.

Since the spatial frequency band extracted by the signal extraction unit L1 and the level range of the luminance component for which the gain coefficient g is calculated by the luminance gain calculation unit G1 can be specified, respectively.
The luminance change of the input image signal can be amplified only in the level range of the designated luminance component in the designated spatial frequency band. For this reason, for example, in the luminance gain calculation means G1, by increasing the luminance gain coefficient with respect to the low-luminance luminance component that is a dark portion, the details of the dark portion can be expressed without reducing the luminance range of other gradations. Become. In addition, since uniform correction is not performed on the entire screen, even if dark portions and bright portions are mixed, for example, the brightness of the dark portions is uniformly increased or the brightness of the bright portions is uniformly decreased. This makes it possible to express both dark and bright details without having to.

Hereinafter, a configuration example of the projector 20 according to the first embodiment that realizes such gradation correction will be described in detail. Hereinafter, an example in which the image signal is composed of the luminance signal Y and the color difference signals U and V will be described, but the image signal according to the present invention is not limited to this.

FIG. 4 is an explanatory diagram of the sensor 300 and the correction intensity calculation unit 310 of FIG. 4 is similar to FIG.
In the image display system 10, a diagram schematically showing a state in which the projector 20 projects an image on the screen SCR from the lateral direction is shown. In FIG. 4, the same parts as those in FIG.

For example, it is assumed that the projector 20 projects an image on the screen SCR under illumination by the external illumination 350. At this time, since the external illumination 350 is reflected on the screen SCR, the appearance of the projected image on the screen SCR is greatly different. Therefore, sensor 3
00 obtains the luminance Yi of the external light from the external illumination 350 and the maximum luminance Yd of the output light of the projection unit 100 of the projector 20, and the correction intensity calculation unit 310 calculates the correction intensity HS based on the luminances Yi and Yd. To do.

In the first embodiment, the sensor 300 is directed toward the projection area of the projector 20, and the projector 20 displays a black image and a white image. When a black image is projected, light leaked from the projector 20 is ignored, and the measurement result of the sensor 300 is determined as the luminance Ys1 (Ys1≈Yi) corresponding to the luminance Yi of the external illumination 350. On the other hand, when a white image is projected, the sensor 3
The measurement result of 00 is determined as the luminance Ys2 (Ys2≈Yi + Yd) obtained by adding the luminance Yi of the external illumination 350 to the maximum luminance Yd of the output light of the projector 20 (projection unit 100). Therefore,
By subtracting the luminance Ys1 from the luminance Ys2, the projector 20 (projection unit 100)
The maximum luminance Yd of the output light can be obtained. The correction intensity calculation unit 310 calculates the brightness Y of external light.
The correction intensity corresponding to the luminance ratio R (= Yi / Yd) between i and the luminance Yd of the output light of the projection unit 100 is calculated.

  FIG. 5 is a diagram for explaining the operation of the correction strength calculation unit 310 in FIG.

The correction intensity calculation unit 310 is realized by a look-up table (hereinafter referred to as LUT) in which the input is the luminance ratio R and the output is the correction intensity HS. For this reason, the correction intensity calculation unit 310 stores the correction intensity HS corresponding to the luminance ratios Ra, Rb, Rc,.
a, HSb, HSc,... are stored, and when a luminance ratio R is input, a correction intensity corresponding to the luminance ratio R is output.

The correction intensity calculation unit 310 preferably stores the correction intensity HS corresponding to the luminance ratio R so that the correction intensity becomes stronger as the luminance ratio becomes larger (external light becomes brighter). By doing so, it becomes possible to reliably prevent influences such as a decrease in luminance contrast when the use environment is bright (when the luminance Yi is large).

The luminance ratio R may be output to the corrected intensity calculating unit 310 after the sensor 300 calculates based on its own measurement results (luminance Yi, Yd), or the corrected intensity calculating unit 310 may calculate the luminance ratio R. After calculating the luminance ratio R based on the measurement results (luminance Yi, Yd), the correction intensity HS corresponding to the luminance ratio R may be output.

FIG. 6 shows a block diagram of a hardware configuration example of the image processing unit 30 in FIG. In FIG.
A correction intensity calculation unit 310 provided outside the image processing unit 30 is also illustrated.

The image processing unit 30 includes a line memory 32, a multistage filter circuit (signal extraction circuit) 40, a luminance signal correction amount calculation circuit (luminance component correction amount calculation unit) 50, and a luminance signal correction circuit (luminance component correction unit) 60. Further, the image processing unit 30 includes a line memory 34, a color difference gain calculation circuit (color difference component correction amount calculation unit) 80, and a color difference signal correction circuit (color difference component correction unit) 90.

The line memory 32 is a luminance signal Y (luminance component of the input image signal) constituting the input image signal.
Is stored. The line memory 32 stores the luminance signal Y by the number of lines necessary for the multistage filter circuit 40.

The multistage filter circuit 40 extracts a signal in a given spatial frequency band from the luminance signal Y (luminance component of the image signal) stored in the line memory 32. This multistage filter circuit 40 is shown in FIG.
The function of the signal extraction means L1 can be realized.

The luminance signal correction amount calculation circuit 50 calculates the correction amount of the luminance signal based on the output of the multistage filter circuit 40, the luminance signal stored in the line memory 32, and the correction strength HS from the correction strength calculation unit 310. calculate. The luminance signal correction amount calculation circuit 50 includes a multistage filter circuit 40.
The correction amount for the luminance signal in the given luminance level range among the luminance signals in the given spatial frequency band extracted by the above can be calculated according to the correction strength HS from the correction strength calculation unit 310. The luminance signal correction amount calculation circuit 50 can realize the function of the luminance gain calculation means G1 shown in FIG.

The luminance signal correction circuit 60 corrects the luminance signal stored in the line memory 32 using the correction amount calculated by the luminance signal correction amount calculation circuit 50, and outputs the corrected luminance signal Y1.

The image processing unit 30 can correct the color difference signal in conjunction with the correction of the luminance signal. Therefore, the line memory 34 stores the color difference signals U and V (color difference components of the input image signal) corresponding to the luminance signal in synchronization with the timing at which the luminance signal Y is stored in the line memory 32.

The chrominance gain calculation circuit 80 generates luminance signals Y and Y1 before and after correction by the luminance signal correction circuit 60.
For example, the correction amounts of the color difference signals U and V are calculated so that the xy chromaticity value of the XYZ color system (CIE 1931 standard colorimetric system) does not change. Here, the color difference gain calculation circuit 80 calculates a gain coefficient corresponding to the correction amount of the color difference signal.

The color difference signal correction circuit 90 corrects the color difference signals U and V stored in the line memory 34 using the correction amount calculated by the color difference gain calculation circuit 80, and the corrected color difference signals U1 and V1.
Output as. Thereby, the color difference signal correction circuit 90 can correct the color difference signals U and V so that the value of the xy chromaticity does not change before and after the correction by the luminance signal correction circuit 60.

As described above, the image processing unit 30 can correct the luminance signal according to the use environment of the projector 20 only for the luminance signal of a given luminance level in a given spatial frequency band. Further, the image processing unit 30 can correct the color difference signal according to the correction amount of the luminance signal in conjunction with the correction of the luminance signal.

  Next, each block constituting the image processing unit 30 will be described.

FIG. 7 shows a block diagram of a configuration example of the multistage filter circuit 40 of FIG. 7, the same parts as those in FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

The multistage filter circuit 40 includes first to third filter circuits 4 having different filter sizes.
2, 44, 46. FIG. 7 illustrates an example in which the multistage filter circuit 40 performs filter processing with three types of filter circuits, but the present invention is not limited to the number of filter circuits.

The multistage filter circuit 40 includes a plurality of filter circuits having different frequency bands of signals to be extracted, and each filter circuit includes pixel values of pixels arranged in the horizontal direction and the vertical direction of an image,
The result of the convolution operation with the filter coefficient matrix is output.

The first filter circuit 42 can output the filtered result according to the following equation.

In the above equation, the output of the first filter circuit 42 is FO1, the luminance signal of the coordinates (x, y) is Y (x, y), the filter coefficients are a, (i, j) are relative to the target pixel. Take the range of the above equation in coordinates and let the filter size be s. Each filter circuit receives a luminance signal having the number of lines (the number of vertical scanning lines) corresponding to the filter size.

Although the above equation shows the output of the first filter circuit 42, the second and third filter circuits 44 and 46 can also output the same filter processing result as the above equation (output FO2).
, FO3).

In FIG. 7, the filter size of the first filter circuit 42 is “3”, and the second filter circuit 4
Although the filter size of 4 is “5” and the filter size of the third filter circuit 46 is “7”, the present invention is not limited to the filter size.

FIG. 8 shows a block diagram of a configuration example of the luminance signal correction amount calculation circuit 50 of FIG. In FIG. 8, the same parts as those of FIG. In FIG. 8, the image processing unit 3
A correction intensity calculation unit 310 provided outside 0 is also illustrated.
FIG. 9 is an operation explanatory diagram of the weighting calculation circuit 52 of FIG.
FIG. 10 is an operation explanatory diagram of the luminance gain calculation circuit 56 of FIG.
FIGS. 11A and 11B are explanatory diagrams of the luminance gain coefficient h calculated by the luminance gain calculation circuit 56 of FIG. In FIGS. 11A and 11B, the horizontal axis represents luminance, and the vertical axis represents luminance gain coefficient h.

The luminance signal correction amount calculation circuit 50 includes a weighting calculation circuit 52, multipliers 53 _{1 to} 53 ₃ , an adder 54, a luminance gain calculation circuit 56, and multipliers 55 and 57.

The weight calculation circuit 52 receives the outputs of the filter circuits of the first to third filter circuits 42 to 46 constituting the multistage filter circuit 40. The weight calculation circuit 52
As shown in FIG. 9, according to the combination of the output of the first to third filter circuits of the filter circuit 42-46 calculates the weighting coefficients _g 1 to g _3.

Such a weight calculation circuit 52 is realized by an LUT having inputs as outputs of the filter circuits of the first to third filter circuits 42 to 46 and outputs as weighting coefficients g _{1 to} g ₃ . Therefore, the weight calculating circuit 52, in advance weighting coefficient corresponding to a combination of outputs of the filter circuit of the first to third filter circuits _{42~46 (g 1 a, g 2} a, g 3 a),
(G ₁ b, g ₂ b, g ₃ b), (g ₁ c, g ₂ c, g ₃ c), ... are stored,
When outputs FO1 to FO3 of the filter circuits of the first to third filter circuits 42 to 46 are inputted, weighting coefficients corresponding to these combinations are outputted.

Weighting factor _{g 1} is the multiplier 53 ₁ outputs FO1 of the first filter circuit 42 is input
Is input. The multiplier 53 _1, the weighting factor g to output FO1 of the first filter circuit 42
_The result of multiplying ₁ is output to the adder 54.

The weighting coefficient g ₂ is a multiplier 53 ₂ to which the output FO 2 of the second filter circuit 44 is input.
Is input. The multiplier 53 _2, the weighting factor g to output FO2 of the second filter circuit 44
_The result of multiplying ₂ is output to the adder 54.

The weighting coefficient g ₃ is a multiplier 53 ₃ to which the output FO 3 of the third filter circuit 46 is input.
Is input. The multiplier 53 _3, the weighting factor g to the output FO3 of the third filter circuit 46
_The result of multiplying ₃ is output to the adder 54.

The adder 54 adds the multiplication results of the multipliers 53 _{1 to} 53 ₃ and adds the addition result to the multiplier 5.
5 is output. The multiplier 55 receives the luminance gain coefficient h calculated by the luminance gain calculation circuit 56.

A luminance signal constituting the input image signal is input to the luminance gain calculation circuit 56. Then, as shown in FIG. 10, the luminance gain calculation circuit 56 calculates a luminance gain coefficient h (luminance gain) corresponding to the level of the luminance signal (the level of the luminance component of the image signal).

Such a luminance gain calculation circuit 56 uses the input as a luminance signal (luminance component of the image signal),
This is realized by an LUT whose output is a luminance gain coefficient h. Therefore, the luminance gain calculation circuit 56 stores in advance luminance gain coefficients ha, hb, hc,... Corresponding to the luminance signals (input luminance signals) constituting the input image signal, and constitutes the input image signal. When a luminance signal to be input is input, a luminance gain coefficient corresponding to the luminance signal is output. In this luminance gain calculation circuit 56, a luminance gain coefficient corresponding to a desired luminance signal can be designated, so that a correction amount can be generated only for the designated gradation.

For example, as shown in FIG. 11A, the luminance gain calculation circuit 56 desirably outputs a luminance gain coefficient h that is large in the high luminance region and the low luminance region and is substantially zero in the intermediate luminance region. Alternatively, it is desirable that the luminance gain calculation circuit 56 outputs a luminance gain coefficient h that is large in the low luminance region and substantially zero in other luminance regions as shown in FIG. 11B, for example. By doing so, it becomes possible to correct the input image signal so that the details of the dark portion and the bright portion of the display image can be expressed without affecting other luminance regions.

The multiplier 55 multiplies the addition result of the adder 54 by the luminance gain coefficient h from the luminance gain calculation circuit 56. The multiplication result of the multiplier 55 is input to the multiplier 57. The multiplier 57 includes
The correction strength HS obtained as described above by the correction strength calculation unit 310 is input.
The multiplier 57 outputs a correction signal VA corresponding to the correction amount of the luminance signal by multiplying the multiplication result of the multiplier 55 by the correction strength HS. The correction signal VA is input to the luminance signal correction circuit 60.

As described above, the luminance signal correction amount calculation circuit 50 includes the signal of the given spatial frequency band extracted by the multistage filter circuit 40 (signal extraction circuit in a broad sense) and the luminance gain calculated by the luminance gain calculation circuit 56. The correction amount of the luminance signal can be calculated based on the coefficient and the correction strength HS from the correction strength calculation unit 310 corresponding to the usage environment of the projector 20. Since the correction intensity HS corresponds to the luminance ratio R, the luminance signal correction amount calculation circuit 50 corrects the luminance signal based on the signal in the given spatial frequency band, the luminance gain coefficient, and the luminance ratio. The amount can be calculated. Then, the luminance signal correction circuit 60 outputs the corrected luminance signal Y1 by adding the correction signal VA from the luminance signal correction amount calculation circuit 50 to, for example, the luminance signal constituting the input image signal.

In addition, the correction processing of the color difference signal according to the correction amount of the luminance signal in conjunction with the correction of the luminance signal is as follows:
This can be realized with the following configuration.

FIG. 12 is a block diagram showing a configuration example of the color difference gain calculation circuit 80 shown in FIG. In FIG. 12, the same parts as those of FIG.

The color difference gain calculation circuit 80 includes a color difference signal adjustment circuit 82 and an adjustment parameter storage unit 84. The color difference signal adjustment circuit 82 stores the luminance signal (the luminance component of the input image signal) Yin constituting the input image signal, the luminance signal Yout corrected as described above, and the adjustment parameter storage unit 84. The adjustment parameter b is input. Then, the color difference signal adjustment circuit 82 calculates a color difference gain coefficient (color difference gain) gc using the luminance signals Yin and Yout and the adjustment parameter b.

More specifically, the color difference gain calculation circuit 80 calculates the color difference gain coefficient gc according to the following equation.

In the above equation, the adjustment parameter b is a parameter for adjusting the chromaticity. When the adjustment parameter b is “0”, the color difference signal (color difference component) constituting the input image signal is output as it is without being corrected. On the other hand, when the adjustment parameter b is “1”, the chrominance signal is also corrected according to the correction amount of the luminance signal so that the chromaticity does not change before and after the correction of the luminance signal of the input image signal. The adjustment parameter b can be a value larger than “0” and smaller than “1”, but in the first embodiment, the adjustment parameter b is preferably “1”.

FIG. 13 is an explanatory diagram of an operation example of the color difference gain calculation circuit 80 of FIG. In FIG. 13, it is assumed that the adjustment parameter b is “1”.

When the color space indicating the luminance signal on the vertical axis and the color difference signal on the horizontal axis is represented, the R component, the G component, and the B component of RGB are defined in the directions shown in FIG. Here, the area DISP represents a color gamut that can be reproduced by a display device. At this time, when the color of the input image signal is the coordinate P0, the values in the xy chromaticity diagram are equal on the isoline SV passing through the coordinate P0.

However, if the luminance signal constituting the input image signal is corrected as described above, it moves to the coordinate P1. For this reason, the coordinate P1 does not exist on the isoline SV, and the color tendency after the luminance signal is corrected changes.

Therefore, in the color difference gain calculation circuit 80, the color difference gain coefficient gc is used to correct the color difference signal in accordance with the correction amount of the luminance signal so as to convert the color of the input signal at the coordinate P0 into the coordinate P2 on the isoline SV. Is calculated. As a result, even if the luminance signal is corrected, the color tendency of the entire screen can be maintained without changing the corrected luminance level. Therefore, natural correction can be realized without changing the chromaticity of each pixel before and after correction.

The color difference gain coefficient gc calculated in this way is input to the color difference signal correction circuit 90. The color difference signal correction circuit 90 multiplies the color difference signal U from the line memory 34 by the color difference gain coefficient gc and also multiplies the color difference signal V from the line memory 34 by the color difference gain coefficient gc. The color difference signals U and V corrected in this way are input to the projection unit 100.

As described above, the image processing unit 30 can correct not only the luminance signal but also the color difference signal in conjunction with the luminance signal. This avoids a situation in which the chromaticity of each pixel changes according to the correction amount of the luminance signal and the overall color tendency of the screen changes, and when the details of the image are expressed, The tendency can be maintained.

The processing of the image processing unit 30 in the first embodiment can also be realized by software processing. In this case, the image processing unit 30 has a central processing unit (Central Processing Unit).
: Hereinafter referred to as CPU), read only memory (hereinafter referred to as ROM) or random access memory (hereinafter referred to as RAM),
The CPU that has read the program stored in the ROM or RAM executes the processing corresponding to the program to control the hardware such as the multiplier and the adder, thereby performing the correction processing of the luminance component and the color difference component. Do.

FIG. 14 is a flowchart illustrating an example of luminance signal correction processing performed by the image processing unit 30 according to the first embodiment. When the processing in FIG. 14 is realized by software, a program for realizing the processing shown in FIG. 14 is stored in a ROM or RAM built in the image processing unit 30.

First, as the input luminance signal accumulation step, the image processing unit 30 accumulates a luminance signal (input luminance signal) constituting the input image signal (step S10). In this case, the luminance signal is stored in the line memory 32 or a RAM that realizes the function of the line memory 32.

Next, as the use environment information acquisition step, the image processing unit 30 calculates a luminance ratio (used in a broad sense) based on the luminance of the external illumination measured by the sensor 300 and the maximum luminance of the output light of the projection unit 100. Environmental information, visual environment) is acquired (step S12). For example, as described above, the brightness and the projection unit 100 when the projection unit 100 of the projector 20 displays a black image.
The luminance ratio R can be calculated based on the luminance when displaying a white image.

Subsequently, the image processing unit 30 extracts a specific spatial frequency band of the luminance signal as a signal extraction step (step S14). For example, a luminance signal in a given spatial frequency band is extracted by the multistage filter circuit 40. Alternatively, in the case of realizing by software processing, the CPU extracts a luminance signal in the above spatial frequency band by controlling a multiplier or an adder that realizes the function of the multistage filter circuit 40.

Thereafter, the image processing unit 30 calculates the correction amount of the luminance signal as the luminance component correction amount calculation step (step S16). In other words, the luminance signal correction amount calculation circuit 50 is weighted according to the signal extracted by the multistage filter circuit 40, and then multiplied by a coefficient corresponding to the luminance level of the luminance signal constituting the input image signal. Is output. Alternatively, when realized by software processing, the CPU weights the signal according to the signal extracted by the signal extraction processing, and then multiplies the correction signal VA by a coefficient corresponding to the luminance level of the luminance signal constituting the input image signal.
Is generated. That is, in step S16, as a luminance gain calculation step, a luminance gain corresponding to the level of the luminance component of the image signal is calculated. Then, the correction amount of the luminance component is calculated based on the spatial frequency band signal extracted in step S14 and the luminance gain calculated in step S16.

Then, as the luminance component correction step, the image processing unit 30 corrects the luminance signal constituting the input image signal using the correction amount calculated in step S16 (step S18), and outputs the corrected luminance signal. (Step S20), and the series of processing ends (end). That is,
In step S18, the luminance signal correction circuit 60 adds the correction signal VA to the luminance signal constituting the input image signal to generate a corrected luminance signal. Alternatively, when realized by software processing, the CPU adds the correction signal VA to the luminance signal constituting the input image signal to generate a corrected luminance signal.

Note that the same processing can be realized even if the order of step S12 and step S14 is changed.

FIG. 15 is a flowchart illustrating an example of color difference signal correction processing performed by the image processing unit 30 according to the first exemplary embodiment. When the processing in FIG. 15 is realized by software, a program for realizing the processing shown in FIG. 15 is stored in a ROM or RAM built in the image processing unit 30.

First, as the input color difference signal accumulation step, the image processing unit 30 accumulates color difference signals (input color difference signals) constituting the input image signal (step S30). In this case, the color difference signal is stored in the line memory 32 or a RAM that realizes the function of the line memory 32.

Next, as the color difference component correction amount calculation step, the image processing unit 30 calculates a color difference gain coefficient for adjusting the color difference signal according to the luminance signal before and after correction in the luminance signal correction processing of FIG. 14 (step S32). . For example, the color difference signal adjustment circuit 82 outputs the color difference gain coefficient gc corresponding to the luminance signal before and after the correction and the adjustment parameter designated in advance. Alternatively, when realized by software processing, the CPU outputs the color difference gain coefficient gc according to the above equation (2) using the predetermined adjustment parameter b. As described above, in step S32, the correction amount of the color difference component of the image signal is calculated so that the value of the xy chromaticity does not change before and after the correction in the luminance component correction step.

Subsequently, as the color difference component correction step, the image processing unit 30 uses the color difference component correction amount (color difference gain coefficient) calculated in step S32 to correct the color difference signal constituting the input image signal (step S34). Then, the corrected color difference signal is output (step S36), and a series of processing ends (end). That is, in step S34, the color difference signal correction circuit 90 multiplies the color difference signal constituting the input image signal by the color difference gain coefficient calculated in step S32 to generate a corrected color difference signal. Alternatively, when realized by software processing, the CPU
The corrected color difference signal is generated by multiplying the color difference signal constituting the input image signal by the above color difference gain coefficient. As described above, in step S34, the color difference component of the image signal is corrected so that the value of the xy chromaticity does not change before and after the correction in the luminance component correction step.

The luminance signal Y1 and the color difference signals U1 and V1 corrected by the image processing unit 30 are the projection unit 10
Output to 0. The projection unit 100 can modulate light from the light source based on the luminance signal Y1 and the color difference signals U1 and V1, and project the modulated light onto the screen SCR.

FIG. 16 shows a diagram of a configuration example of the projection unit 100 of FIG. In FIG. 16, the projection unit 100 according to the first embodiment is described as being configured by a so-called three-plate type liquid crystal projector, but the projection unit of the image display device according to the present invention is configured by a so-called three-plate type liquid crystal projector. It is not limited to things. That is, in the following, one pixel is an R component sub-pixel,
The description will be made assuming that the pixel is composed of a G component sub-pixel and a B component sub-pixel, but the number of sub-pixels (number of color components) constituting one pixel is not limited.

In FIG. 16, the luminance signal Y1 and the color difference signals U1, V1 input from the image processing unit 30 are also shown.
Are converted into image signals of RGB color components, and then light from the light source is modulated for each color component. In this case, the RGB signal conversion circuit may be included in the image processing unit 30 or the projection unit 100.

The projection unit 100 according to the first embodiment includes a light source 110 and integrator lenses 112 and 11.
4. Polarization conversion element 116, superimposing lens 118, R dichroic mirror 120R, G dichroic mirror 120G, reflection mirror 122, R field lens 124R, G
Field lens 124G, R liquid crystal panel 130R (first light modulation element), G liquid crystal panel 130G (second light modulation element), B liquid crystal panel 130B (third light modulation element),
A relay optical system 140, a cross dichroic prism 160, and a projection lens 170 are included.
The liquid crystal panels used as the R liquid crystal panel 130R, the G liquid crystal panel 130G, and the B liquid crystal panel 130B are transmissive liquid crystal display devices. The relay optical system 140 includes relay lenses 142, 144, and 146 and reflection mirrors 148 and 150.

The light source 110 is composed of, for example, an ultra-high pressure mercury lamp, and emits light including at least R component light, G component light, and B component light. The integrator lens 112 has a plurality of small lenses for dividing the light from the light source 110 into a plurality of partial lights. The integrator lens 114 has a plurality of small lenses corresponding to the plurality of small lenses of the integrator lens 112. The superimposing lens 118 superimposes the partial light emitted from the plurality of small lenses of the integrator lens 112 on the liquid crystal panel.

The polarization conversion element 116 includes a polarization beam splitter array and a λ / 2 plate.
The light from 10 is converted into substantially one type of polarized light. The polarization beam splitter array includes a polarization separation film that separates the partial light divided by the integrator lens 112 into p-polarized light and s-polarized light,
It has a structure in which reflection films that change the direction of light from the polarization separation film are alternately arranged. The polarization direction of the two types of polarized light separated by the polarization separation film is aligned by the λ / 2 plate. Light that has been converted into substantially one type of polarized light by the polarization conversion element 116 is applied to the superimposing lens 118.

The light from the superimposing lens 118 enters the R dichroic mirror 120R. The R dichroic mirror 120R has a function of reflecting R component light and transmitting G component and B component light. The light transmitted through the R dichroic mirror 120R is applied to the G dichroic mirror 120G, and the light reflected by the R dichroic mirror 120R is reflected by the reflection mirror 122 and guided to the R field lens 124R.

The dichroic mirror for G 120G has a function of reflecting G component light and transmitting B component light. The light transmitted through the dichroic mirror for G 120G is transmitted to the relay optical system 14
The light incident on 0 and reflected by the G dichroic mirror 120G is guided to the G field lens 124G.

In the relay optical system 140, in order to minimize the difference between the optical path length of the B component light transmitted through the G dichroic mirror 120G and the optical path length of the other R component and G component light, the relay lenses 142, 144, 146 is used to correct the difference in optical path length. Relay lens 14
2 is guided to the relay lens 144 by the reflection mirror 148. The light transmitted through the relay lens 144 is guided to the relay lens 146 by the reflection mirror 150. The light transmitted through the relay lens 146 is applied to the B liquid crystal panel 130B.

The light applied to the R field lens 124R is converted into parallel light and is incident on the R liquid crystal panel 130R. The R liquid crystal panel 130R functions as a light modulation element (light modulation unit), and the transmittance (passage rate, modulation rate) changes based on the R image signal. Accordingly, the light (first color component light) incident on the R liquid crystal panel 130R is modulated based on the R image signal, and the modulated light is incident on the cross dichroic prism 160.

The light applied to the G field lens 124G is converted into parallel light and is incident on the G liquid crystal panel 130G. The G liquid crystal panel 130G functions as a light modulation element (light modulation unit), and the transmittance (passage rate, modulation rate) changes based on the G image signal. Therefore, the light (second color component light) incident on the G liquid crystal panel 130G is modulated based on the G image signal, and the modulated light is incident on the cross dichroic prism 160.

The B liquid crystal panel 130B irradiated with the light converted into parallel light by the relay lenses 142, 144, and 146 functions as a light modulation element (light modulation unit), and has a transmittance (passage rate) based on the B image signal. , Modulation rate) is changed. Therefore, the light (third color component light) incident on the B liquid crystal panel 130B is modulated based on the B image signal, and the modulated light is incident on the cross dichroic prism 160.

The R liquid crystal panel 130R, the G liquid crystal panel 130G, and the B liquid crystal panel 130B have the same configuration. Each liquid crystal panel is a liquid crystal, which is an electro-optical material, sealed in a pair of transparent glass substrates. For example, a polysilicon thin film transistor is used as a switching element, and the transmittance of each color light corresponding to the image signal of each sub-pixel. Modulate.

In the first embodiment, a liquid crystal panel serving as a light modulation element is provided for each color component constituting one pixel, and the transmittance of each liquid crystal panel is controlled by an image signal corresponding to a sub pixel. That is, the image signal for the R component sub-pixel is used to control the transmittance (transmission rate, modulation factor) of the R liquid crystal panel 130R, and the image signal for the G component sub pixel is used for the G liquid crystal panel 130G. The B component sub-pixel image signal is used to control the transmittance of the B liquid crystal panel 130B.

The cross dichroic prism 160 includes an R liquid crystal panel 130R and a G liquid crystal panel 1.
It has a function of outputting combined light obtained by combining incident light from the 30G and B liquid crystal panels 130B as outgoing light. The projection lens 170 is a lens that enlarges and forms an output image on the screen SCR.

After performing the gradation correction process in the first embodiment, by controlling the projection unit 100 as an image display step and displaying an image based on the image signal corrected in the gradation correction process, It is possible to provide an image display method that improves the expression of image details without affecting other luminance regions.

As described above, in the first embodiment, not only the luminance signal but also the color difference signal is corrected in conjunction with the luminance signal. At this time, the luminance signal is corrected in accordance with the usage environment of the projector 20, and the correction target is limited to only a luminance signal in a given luminance level range in a given spatial frequency band.

[First Modification of Embodiment 1]
In the image processing unit 30 according to the first embodiment, the luminance signal correction amount calculation circuit 50 includes a weighting calculation circuit 52 and a luminance gain calculation circuit 56 as illustrated in FIG. 8, and multiplies the weighting coefficient and the luminance gain coefficient. The correction signal VA is generated by the multiplier, but the present invention is not limited to this.

FIG. 17 is a block diagram illustrating a configuration example of the luminance signal correction amount calculation circuit according to the first modification of the first embodiment. For example, instead of the luminance signal correction amount calculation circuit 50 in the first embodiment, FIG.
Is incorporated in the image processing unit 30 of FIG.

The luminance signal correction amount calculation circuit 200 includes first to third LUTs 202 _{1 to} 202 ₃ , a multiplier 2.
04 _{1 to} 204 ₃ , and an adder 206 is included. The luminance signal correction amount calculation circuit 200 includes first to first
After the luminance gain coefficients from the respective LUTs of the _third LUTs 202 _{1 to} 202 ₃ are multiplied by the respective outputs of the multistage filter circuit 40, the multiplication results are added and output as a correction signal VA.

18A, 18B, and 18C, the _first to third LUTs 202 _{1 in} FIG.
To 202 illustrative of the operation of the _3.

The first LUT 202 ₁ receives the correction intensity HS calculated by the correction intensity calculation unit 310 and the luminance signal constituting the input image signal, and outputs the luminance gain coefficient j ₁ corresponding to the luminance signal and the correction intensity HS. To do. Therefore, the luminance gain coefficients j ₁ a, j ₁ b, j ₁ c... Corresponding to the luminance signal and the correction intensity HS are stored in the first LUT 202 ₁ in advance, and the luminance signal and the correction intensity HS are stored in the first LUT 202 _1. the brightness gain coefficient corresponding to the brightness signal and the correction intensity HS when inputted is output as the brightness gain coefficient j _1.

The second LUT 202 _2, correction correction intensity HS is calculated by the intensity calculation unit 310 and a brightness signal which forms the input image signal is input, the luminance signal and the correction intensity HS brightness gain coefficient j ₂ corresponding to the output To do. Therefore, the second LUT 202 ₂ stores in advance the luminance gain coefficients j ₂ a, j ₂ b, j ₂ c... Corresponding to the luminance signal and the correction intensity HS, and the luminance signal and the correction intensity HS are stored in the second LUT 202 _2. the brightness gain coefficient corresponding to the brightness signal and the correction intensity HS when inputted is output as the brightness gain coefficient j _2.

The third LUT 202 ₃ receives the correction intensity HS calculated by the correction intensity calculation unit 310 and the luminance signal constituting the input image signal, and outputs the luminance gain coefficient j ₃ corresponding to the luminance signal and the correction intensity HS. To do. Therefore, the third LUT 202 ₃ stores in advance luminance gain coefficients j ₃ a, j ₃ b, j ₃ c... Corresponding to the luminance signal and the correction intensity HS, and the luminance signal and the correction intensity HS are stored in the third LUT 202 _3. the brightness gain coefficient corresponding to the brightness signal and the correction intensity HS when inputted is output as the brightness gain coefficient j _3.

17, the multiplier 204 ₁ multiplies the brightness gain coefficient _{j 1} from the output FO1 the first LUT 202 ₁ of the first filter circuit 42 constituting the multi-stage filter circuit 40, adds the multiplication results 206 Output to. The multiplier 204 _2, brightness gain coefficients from the output FO2 and the second LUT 202 ₂ of the second filter circuit 44 constituting the multi-stage filter circuit 40 _{j 2}
And the multiplication result is output to the adder 206. The multiplier 204 ₃ multiplies the brightness gain coefficient _{j 3} from the output FO3 the third LUT 202 ₃ of the third filter circuit 46 constituting the multi-stage filter circuit 40, and outputs the multiplication result to the adder 206.

The adder 206 adds the multiplication results of the multipliers 204 _{1 to} 204 ₃ and outputs the addition result as a correction signal VA.

As described above, the image processing unit in the first modification of the first embodiment includes the multistage filter circuit 40 that extracts a signal in a given spatial frequency band from the luminance component of the image signal, and includes a luminance signal correction amount calculation circuit. 200 is provided for each output of the multistage filter circuit 40, and is provided with a plurality of tables for outputting gains corresponding to the correction intensity HS and the level of the luminance component before correction, and for each output of the multistage filter circuit 40. A plurality of multipliers for multiplying the output of 40 and the output of each table constituting the plurality of tables, and an adder for adding the multiplication results of the plurality of multipliers. It can be calculated as a correction amount. Since the correction strength HS corresponds to the luminance ratio R, the luminance signal correction amount calculation circuit 200 is provided for each output of the multistage filter circuit 40, and the gain corresponding to the luminance ratio R and the level of the luminance component before correction. Is provided with a plurality of tables for outputting.

In the first modification of the first embodiment, as in the first embodiment, only a luminance signal in a given luminance level range in a given spatial frequency band can be corrected according to the use environment of the projector 20. At the same time, not only the luminance signal but also the color difference signal can be corrected in conjunction with the luminance signal. This avoids a situation in which the chromaticity of each pixel changes according to the correction amount of the luminance signal and the overall color tendency of the screen changes, and when the details of the image are expressed, The tendency can be maintained.

Further, according to the first modification of the first embodiment, the number of multipliers built in the luminance signal correction amount calculation circuit can be reduced as compared with the first embodiment. Cost can be reduced.

[Second Modification of Embodiment 1]
As shown in FIG. 17, the luminance signal correction amount calculation circuit 200 according to the first modification of the first embodiment includes first to third LUTs 202 _{1 to} 202 ₃ , multipliers 204 _{1 to} 204 _3, and an adder. 206, and the multiplication results of the multipliers using the luminance gain coefficients from the _first to third LUTs 202 _{1 to} 202 ₃ are added, but the present invention is not limited to this. .

FIG. 19 is a block diagram illustrating a configuration example of the luminance signal correction amount calculation circuit according to the second modification of the first embodiment. For example, instead of the luminance signal correction amount calculation circuit 50 in the first embodiment, FIG.
The luminance signal correction amount calculation circuit 250 shown in FIG.

The luminance signal correction amount calculation circuit 250 includes an LUT 252. The luminance signal correction amount calculation circuit 250 outputs the output from the LUT 252 as the correction signal VA.

  FIG. 20 is a diagram for explaining the operation of the LUT 252 in FIG.

In the LUT 252, the correction intensity HS calculated by the correction intensity calculation unit 310 and the luminance signal constituting the input image signal and the filter circuits of the first to third filter circuits 42 to 44 constituting the multistage filter circuit 40 are stored. Outputs FO1 to FO3 are input, and a correction amount corresponding to the combination of the correction strength HS, the luminance signal, and the output of each filter circuit is output. This correction amount is output as a correction signal VA. Therefore, in the LUT 252, the correction amount VAa corresponding to the combination of the correction intensity HS, the luminance signal, and the outputs FO1 to FO3 of each filter circuit in advance.
, VAb,..., VAc, VAd,..., VAe, VAf,... Are stored, and when the correction intensity HS, the luminance signal, and the output of each filter circuit are input, these combinations are combined. The corresponding correction amount is output.

As described above, the image processing unit in the second modification of the first embodiment extracts a signal in a given spatial frequency band from the luminance component of the image signal (signal extraction circuit in a broad sense).
40, the luminance signal correction amount calculation circuit 250 can include a table that outputs the correction amount of the luminance component corresponding to the output of the multi-stage filter circuit 40, the correction strength HS, and the level of the luminance component before correction. Since the correction strength HS corresponds to the luminance ratio R, the luminance signal correction amount calculation circuit 250 corrects the luminance component corresponding to the output of the multistage filter circuit 40, the luminance ratio R, and the level of the luminance component before correction. It means to include a table that outputs quantity. Then, the correction amount output by this table is output as the correction signal VA.

In the second modification of the first embodiment, as in the first modification of the first embodiment or the first embodiment,
Only a luminance signal in a given luminance level range in a given spatial frequency band is supplied to the projector 2
It can be corrected according to the usage environment of 0, and not only the luminance signal but also the color difference signal can be corrected in conjunction with the luminance signal. This avoids a situation in which the chromaticity of each pixel changes according to the correction amount of the luminance signal and the overall color tendency of the screen changes, and when the details of the image are expressed, The tendency can be maintained.

Further, according to the second modification of the first embodiment, the multiplier and the adder built in the luminance signal correction amount calculation circuit are eliminated as compared with the first modification of the first embodiment or the first embodiment. Therefore, a significant reduction in power consumption and cost can be achieved.

[Embodiment 2]
In the first embodiment or its modification, tone correction processing is performed on an input luminance signal without distinguishing between image details and luminance noise, but the present invention is not limited to this. In Embodiment 2 according to the present invention, according to the high frequency component of the luminance component of the input image signal,
By changing the gradation correction intensity, gradation correction processing is performed on the input luminance signal while distinguishing between image details and luminance noise.

The image processing unit 400 according to the second embodiment is replaced with the image processing unit 30 in FIG.
The projector 20 having the sensor 300 and the correction intensity calculation unit 310 is mounted. The image processing unit 400 is not illustrated in consideration of the luminance noise amount included in the luminance component of the image signal of the input image IMGin when performing the same gradation correction processing as in the first embodiment as shown in FIG. The gain coefficient f (frequency gain coefficient. Frequency gain in a broad sense) by the frequency gain calculation means.
Hereinafter the same) is calculated, the gain factor f, By multiplying the signal gY _H, distinguishes and dark detail and luminance noise, so that only dark detail display image is enhanced.

FIG. 21 is an operation explanatory diagram of the image processing unit 400 according to the second embodiment. In FIG. 21, 3
In the dimensional coordinate system, the luminance component of the input image signal, the spatial frequency of the luminance component, and the signal Y _HPF of the high frequency component of the luminance component are schematically shown.

The image processing unit 400 in the second embodiment analyzes the spatial frequency of the luminance component of the image signal,
The correction amount of the luminance component of the image signal only in the spatial frequency band Far (a given spatial frequency band), the luminance ratio (or correction intensity) corresponding to the use environment of the projector, and the spatial frequency analysis result of the luminance component of the image signal And the luminance component of the image signal is corrected using the correction amount. More specifically, the image processing unit 400 uses the luminance signal Yin of the input image signal calculated by the luminance gain calculation unit G1 in the spatial frequency band Far of the luminance component of the image signal extracted by the signal extraction unit L1. Tone correction is performed on a signal in a given level range Yar (range Sar in FIG. 21). At this time, the gradation correction intensity is varied according to the high-frequency component of the luminance component of the input image signal and the luminance ratio (or correction intensity) corresponding to the usage environment of the projector. For example, assuming that the projector is used in the same environment, when there are many high-frequency components of the luminance component, it is determined that there are many desired signal components and little luminance noise, and the correction strength is increased to increase the high-frequency component of the luminance component. When there is little, it is judged that there are few desired signal components and there are many luminance component noises, and the correction intensity is weakened. Thus, the spatial frequency band Far extracted by the signal extraction unit L1 without changing the overall luminance trend without enhancing the luminance noise of the image, and calculated by the luminance gain calculation unit G1. The luminance component can be changed only in a given level range Yar of the luminance signal Yin constituting the input image signal.

The spatial frequency band extracted by the signal extraction means L1, the level range of the luminance component for which the gain coefficient g is calculated by the luminance gain calculation means G1, the high frequency band of the luminance component and the correction intensity can be specified. Only in the level range of the designated luminance component in the spatial frequency band, the luminance change of the input image signal can be amplified in accordance with the luminance noise amount.
For this reason, for example, in the luminance gain calculation means G1, by increasing the luminance gain coefficient with respect to the low-luminance luminance component that is a dark portion, the details of the dark portion can be expressed without reducing the luminance range of other gradations. Become.

In addition, since uniform correction is not performed on the entire screen, even if dark portions and bright portions are mixed, for example, the brightness of the dark portions is uniformly increased or the brightness of the bright portions is uniformly decreased. This makes it possible to express both dark and bright details without having to. For example, FIG.
In the case of 1, since the luminance of the input image signal is corrected from the middle frequency band to the high frequency band, only the details can be enhanced without changing the overall brightness of the input image. Furthermore, since it is possible to distinguish the details of the dark portion of the image from the luminance noise, it is possible to avoid a situation where the luminance noise is emphasized together with the details of the dark portion.

Hereinafter, a configuration example and a processing example of the projector according to the second embodiment for realizing such gradation correction will be described. However, the same parts as those of the projector 20 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

FIG. 22 is a block diagram illustrating a hardware configuration example of the image processing unit 400 according to the second embodiment. 22, the same parts as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. FIG.
In FIG. 2, a correction intensity calculation unit 310 provided outside the image processing unit 400 is also illustrated.

The image processing unit 400 in FIG. 22 is different from the image processing unit 30 in FIG. 6 in that a frequency analysis circuit (frequency analysis unit) 70 in which the image processing unit 400 functions as a high frequency component extraction circuit and a luminance noise removal circuit is added. Instead of the luminance signal correction amount calculation circuit 50, the luminance signal correction amount calculation circuit 45 is replaced.
This is a point where 0 is provided.

The frequency analysis circuit 70 analyzes the spatial frequency of the luminance signal stored in the line memory 32. More specifically, the frequency analysis circuit 70 can extract a high frequency component of the luminance signal and remove luminance noise from the luminance signal from the line memory 32. The output highY, which is the absolute value of the high frequency component of the luminance signal extracted by the frequency analysis circuit 70, is
The result of analysis by the frequency analysis circuit 70 is supplied to the luminance signal correction amount calculation circuit 450. The luminance signal from which luminance noise has been removed by the frequency analysis circuit 70 is supplied to the luminance signal correction circuit 60 as a luminance signal NR.

The luminance signal correction amount calculation circuit 450 outputs the output of the multistage filter circuit 40 and the line memory 32.
, The analysis result of the frequency analysis circuit 70, and the correction strength calculation unit 310.
The correction signal VA corresponding to the correction amount of the luminance signal is calculated on the basis of the correction intensity HS. The luminance signal correction amount calculation circuit 450 is configured to output a given luminance level among luminance signals in a given spatial frequency band extracted by the multistage filter circuit 40 in accordance with the output highY and the correction strength HS (or luminance ratio R). The correction amount for the luminance signal in the range can be calculated.

Here, the output highY is a signal corresponding to the detail of the dark portion of the input image and the luminance noise. That is, when used in the same environment, the luminance signal correction amount calculation circuit 450 generates a correction amount so that the correction strength is increased when it is determined that the luminance noise is small according to the level of the output highY. When it is determined that the luminance noise is large, the correction amount can be generated so that the correction strength becomes weak. The luminance signal correction amount calculation circuit 450 can realize the functions of the luminance gain calculation unit G1 in FIG. 2 and a frequency gain calculation unit (not shown).

The luminance signal correction circuit 60 corrects the luminance signal NR from which luminance noise has been removed by the frequency analysis circuit 70, using the correction signal VA calculated by the luminance signal correction amount calculation circuit 450, and as a corrected luminance signal Y1. Output.

As described above, the image processing unit 400 outputs a luminance signal only for a luminance signal having a given luminance level in a given spatial frequency band according to the spatial frequency analysis result of the luminance signal of the input image and the correction strength HS. It can be corrected. Further, the image processing unit 400 can correct the color difference signal according to the correction amount of the luminance signal in conjunction with the correction of the luminance signal.

Next, since the other blocks are the same as the corresponding blocks of the image processing unit 30, the frequency analysis circuit 70 and the luminance signal correction amount calculation circuit 450, which are blocks specific to the image processing unit 400, will be described.

FIG. 23 shows a block diagram of a configuration example of the frequency analysis circuit 70 of FIG. In FIG. 23, the same parts as those in FIG.

The frequency analysis circuit 70 includes a high-frequency component extraction circuit (high-frequency component extraction unit) 72 and a luminance noise removal circuit (luminance noise removal unit) 74. The high frequency component extraction circuit 72 extracts a given high frequency component including the details of the dark portion of the image and the luminance noise from the luminance signal stored in the line memory 32, and outputs the absolute value as an output highY. The luminance noise removal circuit 74 generates a luminance signal NR from which luminance noise has been removed from the luminance signal accumulated in the line memory 32. Here, the luminance noise removal circuit 74 generates the luminance signal NR using the high frequency component extracted by the high frequency component extraction circuit 72.

The high frequency component extraction circuit 72 includes an HPF (High Pass Filter) circuit 73. The HPF circuit 73 receives the luminance signal from the line memory 32, and outputs the absolute value of the high-frequency component of the luminance signal as an output highY to the luminance signal correction amount calculation circuit 50 and the luminance noise removal circuit 74. Such an HPF circuit 73 outputs a high signal according to the following equation by known HPF processing.
hY is output as the absolute value of the high frequency component.

Here, highY is the output of the HPF circuit 73, Y is the input luminance signal, (x, y) is the coordinates of the target pixel, a _HPF is the filter coefficient, and (u, v) is the relative coordinates around the target pixel. Taking the above range in the system, s represents the size of the filter. For example, s may be “3”, but may be other than “3”.

The luminance noise removal circuit 74 includes an LPF (Low Pass Filter) circuit 75, a weighting calculation circuit 76, multipliers 77 and 78, and an adder 79. The LPF circuit 75 receives the luminance signal from the line memory 32 and passes the low frequency component of the luminance signal. Such an LPF circuit 75 includes:
The output lowY is output according to the following equation by a known LPF process.

Here, lowY is the output of the LPF circuit 75, Y is the input luminance signal, (x, y) is the coordinates of the target pixel, a _LPF is the filter coefficient, and (u, v) is the relative coordinates centered on the target pixel. Taking the above range in the system, s represents the size of the filter. For example, s may be “5”, but may be other than “5”, and is preferably larger than the filter size of the HPF circuit 73.

FIG. 24 shows an example of the filter characteristics of the HPF circuit 73 and the LPF circuit 75 of FIG. In FIG. 24, the horizontal axis represents the frequency of the luminance signal and the vertical axis represents the gain.

The output of the HPF circuit 73 is small in the region where the spatial frequency of the luminance signal is low, and is large in the region where the spatial frequency of the luminance signal is high (T1 in FIG. 24). The cutoff frequency of the HPF circuit 73 is ω _HPF . On the other hand, the output of the LPF circuit 75 increases in a region where the spatial frequency of the luminance signal is low, and decreases in a region where the spatial frequency of the luminance signal is high (T2 in FIG. 24). The cut-off frequency of the LPF circuit 75 is ω _LPF . Here, it is desirable that the cutoff frequency of the HPF circuit 73 is equal to the cutoff frequency of the LPF circuit 75 (ω _HPF = ω _LPF = ω _cut ). As a result, the luminance signal can be corrected without losing the information of the original luminance signal.

In FIG. 23, the weight calculation circuit 76 calculates a weight amount in accordance with the output from the high frequency component extraction circuit 72. The weight calculation circuit 76 outputs the output highY of the HPF circuit 73.
Is stored in the LUT format so that a value corresponding to the output from the HPF circuit 73 can be read out or a plurality of values corresponding to the output from the HPF circuit 73 can be interpolated and output. It has become.

  FIG. 25 is a diagram for explaining the operation of the weight calculation circuit 76.

The weight calculation circuit 76 outputs a weighting coefficient α _LPF to the multiplier 77 and outputs a weighting coefficient α _HPF to the multiplier 78 in accordance with the output of the HPF circuit 73. More specifically, the weighting calculation circuit 76 stores weighting coefficients α _HPF and α _LPF corresponding to the output from the HPF circuit 73 in advance in the LUT format. That is, the weighting calculation circuit 76 has a weighting coefficient (α _HPF a,
.alpha. _LPF a), (.alpha. _HPF b, .alpha. _LPF b), (.alpha. _HPF c, .alpha. _LPF c),... are stored, and when the output highY of the HPF circuit 73 is inputted, it corresponds to this. The weighting coefficients α _HPF and α _LPF are output.

FIG. 26 is an explanatory diagram of the weighting coefficients α _HPF and α _LPF output from the weight calculation circuit 76. In FIG. 26, the horizontal axis represents the output of the HPF circuit 73, and the vertical axis represents the weighting coefficients α _HPF and α _LPF as the weighting amounts output from the weight calculation circuit 76.

As the output highY of the HPF circuit 73 increases, the weighting calculation circuit 76
The weighting coefficient α _HPF that increases in value is stored (T10 in FIG. 26), and the weighting coefficient α _LPF that decreases in value as the output highY of the HPF circuit 73 increases (T11 in FIG. 26). In FIG. 26, the weighting factor alpha _HPF according to the output highY HPF circuit 73, alpha _LPF but has increased or decreased linearly weighting factor alpha _HPF, alpha _LPF is increased or decreased in accordance with a given function It may be.

In FIG. 23, the multiplier 77 outputs the multiplication result of the output of the LPF circuit 75 and the weighting coefficient α _LPF from the weight calculation circuit 76 and outputs the result to the adder 79. Multiplier 78 is H
The multiplication result of the output of the PF circuit 73 and the weighting coefficient α _HPF from the weight calculation circuit 76 is output and output to the adder 79. The adder 79 adds the multiplication result of the multiplier 77 and the multiplication result of the multiplier 78, and outputs the result as a luminance signal NR after removing luminance noise. That is, the luminance noise removal circuit 74 outputs the luminance signal NR according to the following equation.

In the above equation, highY is the output of the HPF circuit 73, and lowY is the LPF circuit 75.
Output.

Since the weighting calculation circuit 76 outputs the weighting coefficients α _HPF and α _LPF as shown in FIG. 26, the luminance signal NR is a signal from which high-frequency luminance noise has been removed. That is, HP
The region where the output highY of the F circuit 73 is small mainly corresponds to the luminance signal distributed in the low frequency band, and the luminance noise is emphasized by reducing the weighting coefficient α _HPF and increasing the weighting coefficient α _LPF. And a desired luminance signal NR can be obtained. On the other hand, the region where the output highY of the HPF circuit 73 is large corresponds to luminance signals distributed mainly in the high frequency band, and the edge information is maintained by increasing the weighting coefficient α _HPF and decreasing the weighting coefficient α _LPF. Or it can be emphasized to obtain the desired luminance signal NR.

In FIG. 23, the frequency analysis circuit 70 has been described as having a configuration including the high frequency component extraction circuit 72 and the luminance noise removal circuit 74. However, the frequency analysis circuit 70 includes only the high frequency component extraction circuit 72. The luminance signal accumulated in the line memory 32 may be supplied to the luminance signal correction circuit 60 as the luminance signal NR as it is.

FIG. 27 shows a block diagram of a configuration example of the luminance signal correction amount calculation circuit 450 of FIG. FIG.
7, the same parts as those in FIG. 8 or FIG. FIG.
7 also illustrates a correction intensity calculation unit 310 provided outside the image processing unit.
FIG. 28 is an operation explanatory diagram of the frequency gain calculation circuit of FIG.

The luminance signal correction amount calculation circuit 450 includes a weighting coefficient storage circuit 452 and multipliers 53 _{1 to} 53.
₃ , an adder 54, a multiplier 55, a luminance gain calculation circuit (luminance gain calculation unit) 56, a frequency gain calculation circuit (frequency gain calculation unit) 458, and multipliers 57 and 59. The luminance signal correction amount calculation circuit 450 is different from the luminance signal correction amount calculation circuit 50 shown in FIG. 8 in that a weighting coefficient storage circuit 452 is provided instead of the weighting calculation circuit 52, and a frequency gain calculation circuit 458 and a multiplier are provided. 59 is added, and the correction signal VA taking into account the frequency gain coefficient f is generated.

In such a luminance signal correction amount calculation circuit 450, the weighting coefficient storage circuit 452 includes:
Weighting coefficients g _{1 to} g ₃ that are predetermined constant values are stored. The weighting factor g ₁ is
Output FO1 of the first filter circuit 42 is input to the multiplier 53 ₁ to be input. Multiplier 5
3 ₁ outputs the result of multiplying the output FO 1 of the first filter circuit 42 by the weighting coefficient g ₁ to the adder 54.

The weighting coefficient g ₂ is a multiplier 53 ₂ to which the output FO 2 of the second filter circuit 44 is input.
Is input. The multiplier 53 _2, the weighting factor g to output FO2 of the second filter circuit 44
_The result of multiplying ₂ is output to the adder 54.

The weighting coefficient g ₃ is a multiplier 53 ₃ to which the output FO 3 of the third filter circuit 46 is input.
Is input. The multiplier 53 _3, the weighting factor g to the output FO3 of the third filter circuit 46
_The result of multiplying ₃ is output to the adder 54.

The adder 54 adds the multiplication results of the multipliers 53 _{1 to} 53 ₃ and adds the addition result to the multiplier 5.
5 is output. The multiplier 55 receives the luminance gain coefficient h calculated by the luminance gain calculation circuit 56.

The frequency gain coefficient f calculated by the frequency gain calculation circuit 458 is input to the multiplier 59 to which the multiplication result of the multiplier 55 is input. The frequency gain calculation circuit 458 receives the output highY from the HPF circuit 73 of FIG. Then, the frequency gain calculating circuit 458 calculates a frequency gain coefficient f (frequency gain) corresponding to the level of the output highY of the HPF circuit 73 as shown in FIG.

Such a frequency gain calculation circuit 458 is realized by an LUT in which the input is the output highY of the HPF circuit 73 and the output is the frequency gain coefficient f. Therefore, the frequency gain calculation circuit 458 has frequency gain coefficients fa, fb, fc corresponding to the output highY in advance.
Are stored, and when the output highY from the HPF circuit 73 is input, a frequency gain coefficient corresponding to the output highY is output. In this frequency gain calculation circuit 458, the frequency gain coefficient corresponding to the desired output highY can be designated, so that the correction amount can be generated only for the designated high frequency band.

Multiplier 59 multiplies the multiplication result of multiplier 55 by frequency gain coefficient f from frequency gain calculation circuit 458. The multiplication result of the multiplier 59 is input to the multiplier 57. This multiplier 5
7, the correction strength HS obtained by the correction strength calculation unit 310 is input as in the first embodiment. The multiplier 57 outputs a correction signal VA corresponding to the correction amount of the luminance signal by multiplying the multiplication result of the multiplier 59 by the correction strength HS. The correction signal VA is input to the luminance signal correction circuit 60.

In this way, the luminance signal correction amount calculation circuit 450 and the signal of the given spatial frequency band extracted by the multistage filter circuit 40 (signal extraction circuit in a broad sense) and the luminance gain calculation circuit 56 are used.
Based on the luminance gain coefficient calculated by the frequency gain calculation circuit 58, the correction gain HS (or the luminance ratio R) from the correction intensity calculation unit 310 corresponding to the usage environment of the projector 20. Thus, the correction amount of the luminance signal can be calculated. Then, the luminance signal correction circuit 60 adds the correction signal VA from the luminance signal correction amount calculation circuit 450 to the luminance signal from which the luminance signal or luminance noise component constituting the input image signal is removed, for example, after correction. Luminance signal Y1 is output. As a result, the correction can be performed only when the luminance noise is small, so that it is possible to prevent the luminance noise from being amplified by the correction.

Note that the luminance signal correction amount calculation circuit 450 does not need to calculate the luminance gain coefficient, and the luminance signal correction amount calculation circuit 450 has a given luminance level range in a given spatial frequency band extracted by the multistage filter circuit 40 (signal extraction circuit in a broad sense). Luminance signal, the frequency gain coefficient calculated by the frequency gain calculation circuit 58, and the correction intensity HS (or the luminance ratio R) from the correction intensity calculation unit 310 corresponding to the environment in which the projector 20 is used. The amount of correction may be calculated.

In the second embodiment, the correction process of the color difference signal corresponding to the correction amount of the luminance signal in conjunction with the correction of the luminance signal can be performed in the same manner as in the first embodiment, and thus the description thereof is omitted. Therefore, the image processing unit 400 can correct not only the luminance signal but also the color difference signal in conjunction with the luminance signal. This avoids a situation in which the chromaticity of each pixel changes according to the correction amount of the luminance signal and the overall color tendency of the screen changes, and when the details of the image are expressed, The tendency can be maintained.

The processing of the image processing unit 400 in the second embodiment can also be realized by software processing. In this case, the image processing unit 400 includes a CPU, a ROM, and a RAM, and a CPU that reads a program stored in the ROM or RAM executes a process corresponding to the program so that a multiplier, an adder, and the like are executed. The hardware is controlled to correct the luminance component and the color difference component.

FIG. 29 is a flowchart illustrating an example of luminance signal correction processing performed by the image processing unit 400 according to the second embodiment. When the processing of FIG. 29 is realized by software, the ROM built in the image processing unit 400
Alternatively, a program for realizing the processing shown in FIG. 29 is stored in the RAM.

First, as the input luminance signal accumulation step, the image processing unit 400 accumulates a luminance signal (input luminance signal) constituting the input image signal (step S40). In this case, the luminance signal is stored in the line memory 32 or a RAM that realizes the function of the line memory 32.

Next, as the use environment information acquisition step, the image processing unit 400 calculates a luminance ratio (used in a broad sense) based on the luminance of the external illumination measured by the sensor 300 and the maximum luminance of the output light of the projection unit 100. Environmental information) is acquired (step S42).

Subsequently, as a signal extraction step, the image processing unit 400 extracts a luminance signal in a specific spatial frequency band from the luminance signal stored in the line memory 32 or the like (step S44). For example, a luminance signal in a given spatial frequency band is extracted by the multistage filter circuit 40. Or
When implemented by software processing, the CPU extracts a luminance signal in the spatial frequency band by controlling a multiplier or an adder that implements the function of the multistage filter circuit 40.

Thereafter, the image processing unit 400 analyzes the spatial frequency of the luminance signal in the specific spatial frequency band extracted in step S44 as a frequency analysis step (steps S46 and S48). More specifically, in step S46, as a high frequency component extraction step, a luminance signal of a given high frequency component is extracted from the specific spatial frequency band extracted in step S44. In step S48, as a luminance noise removal step, luminance noise components are removed from the luminance signal stored in the line memory 32 or the like.

Then, the image processing unit 400 calculates the correction amount of the luminance signal as the luminance component correction amount calculation step (Step S50, Step S52, Step S54). More specifically, in step S50, as the luminance gain calculation step, the luminance signal extracted in step S44 is weighted and multiplied by a coefficient corresponding to the luminance level of the luminance signal constituting the input image signal. . In step S52, as the frequency gain calculation step, the luminance signal of the high frequency component extracted in step S46 (output highY of the HPF circuit 73).
) Is multiplied by the luminance signal multiplied by the coefficient corresponding to the luminance level in step S50. As a result, in step S56, the correction signal VA corresponding to the correction amount of the luminance signal.
Is generated. Alternatively, in the case of realizing by software processing, after the CPU weights the luminance signal extracted by the signal extraction processing, a coefficient corresponding to the luminance level of the luminance signal constituting the input image signal, and step S46 The luminance signal (H
The result of multiplication using a coefficient corresponding to the output highY) of the PF circuit 73 is generated as a correction signal VA corresponding to the correction amount of the luminance signal. As described above, in step S54, the correction amount of the luminance component is determined based on the spatial frequency band signal extracted in step S46, the luminance gain calculated in step S50, and the frequency gain calculated in step S52. Calculated.

Then, as the luminance component correction step, the image processing unit 400 corrects the luminance signal from which luminance noise has been removed in step S48, using the correction amount calculated in step S54 (step S56), and the corrected luminance signal. Is output (step S58), and a series of processing ends (end). That is, in step S56, the luminance signal correction circuit 60 performs step S4.
In step 8, the correction signal VA is added to the luminance signal from which luminance noise has been removed to generate a corrected luminance signal. Alternatively, when realized by software processing, the CPU performs step S
In 48, the correction signal VA is added to the luminance signal from which luminance noise has been removed to generate a corrected luminance signal.

In the second embodiment, the order of steps S46 and S48 in FIG. 29 may be interchanged, or the order of steps S50 and S52 in FIG. 29 may be interchanged.
It is not limited to the processing order shown in FIG.

The image processing unit 400 according to the second embodiment can perform a color difference signal correction process as in the first embodiment. The color difference signal correction processing by the image processing unit 400 is the same as that in the first embodiment.
Because of this, illustration and description are omitted.

That is, also in the second embodiment, after performing the above-described tone correction processing, the projection unit 100 is controlled as an image display step, and an image is obtained based on the image signal corrected in the above-described tone correction processing. By displaying, it is possible to provide an image display method that improves the expression of image details without affecting other luminance regions.

As described above, also in the second embodiment, not only the luminance signal but also the color difference signal is corrected in conjunction with the luminance signal. At this time, the luminance signal is corrected in accordance with the usage environment of the projector 20, and the correction target is limited to only a luminance signal in a given luminance level range in a given spatial frequency band.

[First Modification of Embodiment 2]
In the second embodiment, the first to third filter circuits 42 and 4 constituting the multistage filter circuit 40 are used.
Although the ratio of the output FO1 to FO3 of 4, 46 could not be changed, the present invention is not limited to this. In the first modification example of the second embodiment, the first to the first stages constituting the multistage filter circuit 40.
The ratio of the outputs FO <b> 1 to FO <b> 3 of the third filter circuits 42, 44, 46 can be changed according to the output highY of the HPF circuit 73.

The difference between the image processing unit in the first modification of the second embodiment and the image processing unit 400 in the second embodiment is the configuration of the luminance signal correction amount calculation circuit. So, in the following,
The points common to the second embodiment are not shown and described, and the luminance signal correction amount calculation circuit of the image processing unit in the first modification of the second embodiment will be described.

FIG. 30 is a block diagram illustrating a configuration example of the luminance signal correction amount calculation circuit according to the first modification of the second embodiment. In FIG. 30, the same parts as those in FIG. 27 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. FIG. 30 also illustrates a correction strength calculation unit 310 provided outside the image processing unit.
FIG. 31 is an operation explanatory diagram of the weighting calculation circuit of FIG.

The luminance signal correction amount calculation circuit 490 in the first modification of the second embodiment includes a weighting calculation circuit 492, multipliers 53 _{1 to} 53 ₃ , an adder 54, multipliers 55 and 57, and a luminance gain calculation circuit 56.

The weight calculation circuit 492 includes an HPF of the high frequency component extraction circuit 72 of the frequency analysis circuit 70.
The output highY generated by the circuit 73 is input. The weight calculation circuit 4
As shown in FIG. 31, 92 calculates weighting coefficients g _{1 to} g ₃ in accordance with the output highY from the HPF circuit 73.

Such a weight calculation circuit 492 is realized by an LUT in which the input is the output highY from the HPF circuit 73 and the outputs are the weighting coefficients g _{1 to} g ₃ . Therefore, the weighting calculation circuit 492 has weighting coefficients (g ₁ a, g ₂ a, g ₃ a), (g ₁ b, g ₂ b, g ₃ b) corresponding to the output highY from the HPF circuit 73 in advance. (G ₁ c, g ₂ c, g ₃ c
),... Are stored, and when an output highY is input from the HPF circuit 73, a weighting coefficient corresponding to the output highY is output.

The adder 54 adds the multiplication results of the multipliers 53 _{1 to} 53 ₃ and adds the addition result to the multiplier 5.
5 is output. The multiplier 55 receives the luminance gain coefficient h calculated by the luminance gain calculation circuit 56. The multiplication result of the multiplier 55 is input to the multiplier 57. As in FIG. 27, the multiplier 57 receives the correction strength HS obtained by the correction strength calculation unit 310. The multiplier 57 outputs a correction signal VA corresponding to the correction amount of the luminance signal by multiplying the multiplication result of the multiplier 55 by the correction strength HS. The correction signal VA is input to the luminance signal correction circuit 60.

Thus, the luminance signal correction amount calculation circuit 490 outputs the output highY from the HPF circuit 73.
The correction intensity from the correction intensity calculation unit 310 corresponding to the use environment of the projector 20, the signal of the given spatial frequency band extracted by the multistage filter circuit 40 (signal extraction circuit in a broad sense), the luminance gain coefficient, and the like. The correction amount of the luminance signal can be calculated based on HS. Then, the luminance signal correction circuit 60 adds the correction signal VA from the luminance signal correction amount calculation circuit 490 to the luminance signal from which the luminance signal or luminance noise component constituting the input image signal has been removed, for example, after correction. Luminance signal Y1 is output.

FIG. 32 is an operation explanatory diagram of the image processing unit in the first modification of the second embodiment. FIG.
In FIG. 21, the same parts as those in FIG.

In the first modification of the second embodiment, as in the second embodiment, the spatial frequency of the luminance component of the image signal is analyzed, and the luminance component of the image signal is analyzed only in the spatial frequency band Far (a given spatial frequency band). A correction amount is calculated according to a luminance ratio (or correction intensity) corresponding to the use environment of the projector and a spatial frequency analysis result of the luminance component of the image signal, and the luminance component of the image signal is corrected using the correction amount. . At this time, the gradation correction strength is varied according to the high-frequency component of the luminance component of the input image signal. Furthermore, in the first modification of the second embodiment, since the ratio of the outputs FO1 to FO3 of the first to third filter circuits 42, 44, and 46 that constitute the multistage filter circuit 40 can be changed, as shown in FIG. In addition, the luminance signal can be extracted so that the spatial frequency band becomes narrower as the level of the high frequency component decreases and the luminance noise increases. Then, by giving the luminance gain so that the gain becomes large at low luminance, only the details of the dark part can be amplified.

As described above, according to the first modification of the second embodiment, in addition to the effect of the second embodiment, the spatial frequency band extracted according to the luminance noise amount can be narrowed, so that the luminance existing in the high frequency band can be reduced. Noise can be prevented from being amplified.

[Second Modification of Embodiment 2]
In the image processing unit according to the second embodiment or the first modification of the second embodiment, the luminance signal correction amount calculation circuit includes a weighting coefficient storage circuit 452, a weighting calculation circuit 492, and a luminance gain calculation circuit 56. However, the present invention is not limited to this, although the correction signal VA is generated by a multiplier that multiplies the luminance gain coefficient.

FIG. 33 is a block diagram illustrating a configuration example of the luminance signal correction amount calculation circuit according to the second modification of the second embodiment. For example, instead of the luminance signal correction amount calculation circuit 450 in the second embodiment, FIG.
3 is incorporated in the image processing unit 400 of FIG.

The luminance signal correction amount calculation circuit 500 includes first to third LUTs 502 _{1 to} 502 ₃ and a multiplier 5.
04 _{1 to} 504 ₃ , and an adder 506. Each L of the _first to third LUTs 502 _{1 to} 502 ₃
The UT receives the luminance signal that constitutes the input image signal and the output highY from the HPF circuit 73. Each LUT stores a luminance gain coefficient corresponding to the combination of the correction strength HS corresponding to the use environment of the projector, the luminance signal constituting the input image signal, and the output highY from the HPF circuit 73. This luminance signal correction amount calculation circuit 500 uses the multistage filter circuit 4 to calculate the luminance gain coefficient from each of the _{first to third} LUTs 502 _{1 to} 502 _3.
After multiplying each output of 0, the multiplication results are added and output as a correction signal VA.

34A, 34B, and 34C show the _first to third LUTs 502 _{1 in} FIG.
To 502 illustrative of the operation of the _3.

As shown in FIG. 34 (A), the first LUT 502 _1, and the output highY from the luminance signal and the HPF circuit 73 which forms the input image signal and the correction intensity HS is input, the luminance signal,
A luminance gain coefficient j ₁ corresponding to the combination of the output highY and the correction strength HS is output. Therefore, the first LUT 502 _1, advance the luminance signal, the output highY and correction intensity H
The luminance gain coefficients j ₁ a, j ₁ b, j ₁ c... Corresponding to the combination of S are stored, and when the luminance signal, the output highY, and the correction intensity HS are input, the luminance signal and the HPF circuit 73 are stored. and output as the brightness gain coefficient j ₁ the brightness gain coefficient corresponding to the combination of the output highY and correction intensity HS from.

As shown in FIG. 34 (B), the second LUT 502 _2, and output highY from the luminance signal and the HPF circuit 73 which forms the input image signal and the correction intensity HS is input, the luminance signal,
And it outputs the brightness gain coefficient _{j 2} corresponding to the combination of the output highY and correction intensity HS. Therefore, the second LUT 502 _2, previously luminance signal output highY and correction intensity H
The luminance gain coefficients j ₂ a, j ₂ b, j ₂ c... Corresponding to the combination of S are stored, and when the luminance signal, the output highY, and the correction strength HS are input, the luminance signal and the HPF circuit 73 are stored. which is output as the brightness gain coefficient j ₂ the brightness gain coefficient corresponding to the combination of the output highY and correction intensity HS from.

As shown in FIG. 34 (C), the third LUT 502 _3, and the output highY from the luminance signal and the HPF circuit 73 which forms the input image signal and the correction intensity HS is input, the luminance signal,
And it outputs the brightness gain coefficient _{j 3} corresponding to the combination of the output highY and correction intensity HS. Therefore, the third LUT 502 _3, previously luminance signal output highY and correction intensity H
The luminance gain coefficients j ₃ a, j ₃ b, j ₃ c... Corresponding to the combination of S are stored, and when the luminance signal, the output highY, and the correction intensity HS are input, the luminance signal and the HPF circuit 73 are stored. and output as the brightness gain coefficient j ₃ the brightness gain coefficient corresponding to the combination of the output highY and correction intensity HS from.

In FIG. 33, a multiplier 504 ₁ multiplies the output FO1 of the _first filter circuit 42 constituting the multistage filter circuit 40 by the luminance gain coefficient j ₁ from the first LUT 5021, and the multiplication result is added to the adder 506. Output to. The multiplier 504 _2, brightness gain coefficients from the output FO2 and the second LUT 502 ₂ of the second filter circuit 44 constituting the multi-stage filter circuit 40 _{j 2}
And the multiplication result is output to the adder 506. The multiplier 504 ₃ multiplies the output FO 3 of the third filter circuit 46 constituting the multistage filter circuit 40 by the luminance gain coefficient j ₃ from the third LUT 502 _3, and outputs the multiplication result to the adder 506.

The adder 506 adds the multiplication results of the multipliers 504 _{1 to} 504 ₃ and outputs the addition result as a correction signal VA.

As described above, the image processing unit in the second modification of the second embodiment includes the multistage filter circuit 40 that extracts a signal in a given spatial frequency band from the luminance component of the image signal, and includes a luminance signal correction amount calculation circuit. 500 is provided for each output of the multistage filter circuit 40 and outputs a gain corresponding to the level of the luminance component before correction; the output of the multistage filter circuit 40 provided for each output of the multistage filter circuit 40; A plurality of multipliers for multiplying the outputs of the tables constituting the plurality of tables, and an adder for adding the multiplication results of the plurality of multipliers, and calculating the output of the adder as a correction amount of the luminance component be able to.

In the second modification of the second embodiment, not only the luminance signal but also the color difference signal can be corrected in conjunction with the luminance signal, as in the first modification of the second or second embodiment. .

According to the second modification example of the second embodiment, the number of multipliers incorporated in the luminance signal correction amount calculation circuit is reduced as compared with the first modification example of the second embodiment or the second embodiment. Therefore, low power consumption and low cost can be achieved.

[Third Modification of Embodiment 2]
As shown in FIG. 33, the luminance signal correction amount calculation circuit 500 according to the second modification of the second embodiment includes _first to third LUTs 502 _{1 to} 502 ₃ , multipliers 504 _{1 to} 504 _3, and an adder. 506, and the multiplication results of the multipliers using the luminance gain coefficients from the _first to third LUTs 502 _{1 to} 502 ₃ are added. However, the present invention is not limited to this. .

FIG. 35 is a block diagram showing a configuration example of the luminance signal correction amount calculation circuit in the third modification of the second embodiment. For example, instead of the luminance signal correction amount calculation circuit 50 in the second embodiment, FIG.
Is incorporated in the image processing unit 400 of FIG.

The luminance signal correction amount calculation circuit 550 includes an LUT 552. The luminance signal correction amount calculation circuit 550 outputs the output from the LUT 552 as the correction signal VA.

  FIG. 36 is a diagram for explaining the operation of the LUT 552 in FIG.

The LUT 552 includes a luminance signal constituting the input image signal and an output hi from the HPF circuit 73.
ghY, the outputs FO1 to FO3 and the correction intensity HS of the filter circuits of the first to third filter circuits 42 to 44 constituting the multistage filter circuit 40 are input, and the luminance signal and the output highY
The correction amount corresponding to the combination of the output of each filter circuit and the correction strength HS is output.
This correction amount is output as a correction signal VA. Therefore, in the LUT 552, correction amounts (correction signals) VAa, VAb,..., VAc, VAd,.・,
VAe, VAf,... Are stored, and when a luminance signal, an output highY, an output of each filter circuit, and a correction strength HS are input, a correction amount corresponding to the combination thereof is output. .

Also in the third modification of the second embodiment, not only the luminance signal but also the color difference signal can be corrected in conjunction with the luminance signal, as in the second embodiment or its modification.

According to the third modified example of the second embodiment, the multiplier and the adder built in the luminance signal correction amount calculation circuit can be eliminated as compared with the second embodiment or the modified example. Significantly lower power consumption and cost can be achieved.

The image processing apparatus, the image display apparatus, and the image processing method according to the present invention have been described based on the above embodiment, but the present invention is not limited to the above embodiment and does not depart from the gist thereof. The present invention can be implemented in various modes within the scope, and for example, the following modifications are possible.

(1) In each of the above-described embodiments or modifications thereof, the projector has been described as an example of the image display device, but the present invention is not limited to this. The image display device according to the present invention can be applied to all devices that perform image display, such as liquid crystal display devices, plasma display devices, and organic EL display devices.

(2) In each of the above-described embodiments or modifications thereof, it has been described that a light valve using a transmissive liquid crystal panel is used as the light modulation element, but the present invention is not limited to this. As a light modulation element, for example, DLP (Digital Light Processing) (registered trademark), L
COS (Liquid Crystal On Silicon) or the like may be employed.

(3) In each of the above-described embodiments or modifications thereof, a light valve using a so-called three-plate transmissive liquid crystal panel as the light modulation element has been described as an example, but a single-plate liquid crystal panel, two plates, or four You may employ | adopt the light valve using the transmissive liquid crystal panel more than a plate type.

(4) In each of the above embodiments or modifications thereof, one pixel has been described as being composed of three color component sub-pixels, but the present invention is not limited to this. The number of color components constituting one pixel may be 2, or 4 or more.

(5) In each of the above-described embodiments or modifications thereof, the luminance gain and the frequency gain are calculated. However, the present invention is not limited to this. That is, when correcting the input luminance signal, at least one of the luminance gain and the frequency gain may be calculated, and the input luminance signal may be corrected using the calculation result.

(6) Although the present invention has been described as an image processing apparatus, an image display apparatus, and an image processing method in each of the above-described embodiments or modifications thereof, the present invention is not limited to this. For example, an image display system including the image processing apparatus and the image display apparatus described above may be used. Alternatively, for example, a program describing a processing method of an image processing apparatus (image processing method) for realizing the present invention or a processing procedure of an image display apparatus processing method (image display method) for realizing the present invention Alternatively, it may be a recording medium on which the program is recorded.

1 is a block diagram of a configuration example of an image display system in Embodiment 1. FIG. FIG. 3 is an explanatory diagram of gradation correction processing performed in the image processing unit of FIG. 1. FIG. 3 is an operation explanatory diagram of the image processing unit in FIG. 1. Explanatory drawing of the sensor and correction | amendment intensity | strength calculation part of FIG. Operation | movement explanatory drawing of the correction | amendment intensity | strength calculation part of FIG. The block diagram of the hardware structural example of the image process part of FIG. The block diagram of the structural example of the multistage filter circuit of FIG. FIG. 7 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit in FIG. 6. FIG. 9 is an operation explanatory diagram of the weight calculation circuit of FIG. 8. FIG. 9 is an operation explanatory diagram of the luminance gain calculation circuit of FIG. 8. 11A and 11B are explanatory diagrams of luminance gain coefficients calculated by the luminance gain calculation circuit of FIG. FIG. 7 is a block diagram of a configuration example of a color difference gain calculation circuit in FIG. 6. FIG. 13 is an explanatory diagram of an operation example of the color difference gain calculation circuit of FIG. 12. FIG. 3 is a flowchart of a luminance signal correction process example of the image processing unit according to the first embodiment. FIG. 3 is a flowchart of a color difference signal correction process example of the image processing unit according to the first embodiment. The figure of the structural example of the projection part of FIG. FIG. 6 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit according to a first modification of the first embodiment. 18A, 18B, and 18C are explanatory diagrams of operations of the first to third LUTs in FIG. FIG. 10 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit according to a second modification of the first embodiment. FIG. 20 is an operation explanatory diagram of the LUT in FIG. 19. FIG. 9 is an operation explanatory diagram of an image processing unit according to the second embodiment. FIG. 4 is a block diagram of a hardware configuration example of an image processing unit according to the second embodiment. The block diagram of the structural example of the frequency analysis circuit of FIG. The figure which shows an example of the filter characteristic of the HPF circuit of FIG. 23, and an LPF circuit. The operation explanatory view of a weighting calculation circuit. Explanatory drawing of the weighting coefficient which a weighting calculation circuit outputs. FIG. 23 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit in FIG. 22. FIG. 28 is an operation explanatory diagram of the frequency gain calculation circuit of FIG. 27. FIG. 9 is a flowchart of a luminance signal correction process example of an image processing unit according to the second embodiment. FIG. 10 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit according to a first modification of the second embodiment. FIG. 31 is an operation explanatory diagram of the weight calculation circuit of FIG. 30. FIG. 10 is an operation explanatory diagram of an image processing unit in a first modification of the second embodiment. FIG. 10 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit according to a second modification of the second embodiment. 34 (A), 34 (B), and 34 (C) are operation explanatory views of the first to third LUTs of FIG. FIG. 10 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit according to a third modification of the second embodiment. FIG. 36 is an operation explanatory diagram of the LUT in FIG. 35.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image display system, 20 ... Projector, 30,400 ... Image processing part,
32, 34 ... line memory, 40 ... multistage filter circuit, 42 ... first filter circuit,
44 ... 2nd filter circuit, 46 ... 3rd filter circuit,
50, 200, 250, 450, 490, 500, 550 ... luminance signal correction amount calculation circuit,
52, 76, 492 ... weighting calculation circuit,
53 _{1 to} 53 ₃ , 55, 57, 59, 77, 78, 204 _{1 to} 204 ₃ , 504 ₁ to 50
4 ₃ ... multiplier,
54, 79, 206, 506 ... adder, 56 ... luminance gain calculation circuit,
60 ... Luminance signal correction circuit, 70 ... Frequency analysis circuit, 72 ... High frequency component extraction circuit,
73 ... HPF circuit, 74 ... Luminance noise elimination circuit, 75 ... LPF circuit,
80: Color difference gain calculation circuit, 82: Color difference signal adjustment circuit,
84 ... Adjustment parameter storage unit, 90 ... Color difference signal correction circuit, 100 ... Projection unit,
110: Light source 112, 114: Integrator lens 116: Polarization conversion element
118 ... Superimposing lens, 120R ... R dichroic mirror,
120G ... Dichroic mirror for G, 122,148,150 ... Reflective mirror,
124R ... R field lens, 124G ... G field lens,
130R ... R liquid crystal panel, 130G ... G liquid crystal panel,
130B ... Liquid crystal panel for B, 140 ... Relay optical system,
142, 144, 146 ... relay lens, 160 ... cross dichroic prism,
170 ... projection lens, 202 ₁ , 502 ₁ ... first LUT,
202 ₂ , 502 ₂ ... 2nd LUT, 202 ₃ , 502 ₃ ... 3rd LUT,
252,552 ... LUT, 300 ... sensor, 310 ... correction intensity calculation unit,
350 ... external illumination, 452 ... weighting coefficient storage circuit,
458: Frequency gain calculation circuit, SCR: Screen

Claims (19)

An image processing apparatus that corrects an image signal supplied to an image display unit,
A luminance component correction amount calculation unit that calculates the correction amount of the luminance component of the image signal only in accordance with the visual environment only for the image signal in the given luminance level range in the given spatial frequency band;
An image processing apparatus comprising: a luminance component correction unit that corrects a luminance component of the image signal using the correction amount calculated by the luminance component correction amount calculation unit. In claim 1,
The luminance component correction amount calculation unit,
An image processing apparatus, wherein the correction amount is calculated using a luminance ratio of external light and output light of the image display unit as the visual environment. In claim 2,
A signal extraction circuit for extracting a signal of the spatial frequency band from a luminance component of the image signal;
The luminance component correction amount calculation unit
A luminance gain calculation circuit for calculating a luminance gain corresponding to the level of the luminance component of the image signal;
A correction amount of the luminance component is calculated based on the signal in the spatial frequency band extracted by the signal extraction circuit, the luminance gain calculated by the luminance gain calculation circuit, and the luminance ratio. An image processing apparatus. In claim 2,
A multi-stage filter circuit for extracting a signal of the spatial frequency band from a luminance component of the image signal;
The luminance component correction amount calculation unit
A plurality of tables that are provided for each output of the multi-stage filter circuit and that output a gain corresponding to the level of the luminance component before correction and the luminance ratio;
A plurality of multipliers that are provided for each output of the multi-stage filter circuit, and multiply the outputs of the multi-stage filter circuit and the outputs of the tables constituting the plurality of tables;
An adder for adding the multiplication results of each multiplier constituting the plurality of multipliers,
An image processing apparatus that calculates an output of the adder as a correction amount of the luminance component. In claim 2,
A signal extraction circuit for extracting a signal of the spatial frequency band from a luminance component of the image signal;
The luminance component correction amount calculation unit
An image processing apparatus comprising: a table for outputting a correction amount of the luminance component corresponding to the output of the signal extraction circuit, the level of the luminance component before correction, and the luminance ratio. In claim 2,
A frequency analysis unit that analyzes a spatial frequency of a luminance component of the image signal;
The luminance component correction amount calculation unit,
An image processing apparatus that calculates a correction amount of a luminance component of the image signal in accordance with the luminance ratio and an analysis result of the frequency analysis unit. In claim 6,
The frequency analysis unit
A high frequency component extraction unit for extracting a given high frequency component of the luminance component of the image signal;
The luminance component correction amount calculation unit
A frequency gain calculation unit that calculates a frequency gain corresponding to the high frequency component extracted by the high frequency component extraction unit;
A correction amount of the luminance component is calculated based on a luminance component in a given luminance level range in the spatial frequency band, the frequency gain calculated by the frequency gain calculation unit, and the luminance ratio. An image processing apparatus. In claim 7,
The luminance component correction amount calculation unit
A luminance gain calculation unit for calculating a luminance gain corresponding to the level of the luminance component of the image signal;
A correction amount of the luminance component is calculated based on the spatial frequency band signal, the frequency gain, the luminance gain calculated by the luminance gain calculation unit, and the luminance ratio. Processing equipment. In any of claims 6 to 8,
An image processing apparatus comprising: a signal extraction unit that extracts a signal in the spatial frequency band from a luminance component of the image signal. In any one of Claims 6 thru | or 9.
The frequency analysis unit
A luminance noise removing unit for removing a given luminance noise component from the luminance component of the image signal;
The luminance component correction unit is
An image processing apparatus that corrects a luminance component of the image signal from which the luminance noise component has been removed by the luminance noise removing unit, using the correction amount. In any one of Claims 1 thru | or 10.
An image processing apparatus comprising: a color difference component correction unit that corrects a color difference component of the image signal so that an xy chromaticity value does not change before and after correction by the luminance component correction unit. In claim 11,
A color difference component correction amount calculation unit that calculates a correction amount of the color difference component of the image signal based on the luminance component of the image signal before and after correction by the luminance component correction unit so that the value of xy chromaticity does not change;
The color difference component correction unit is
An image processing apparatus that corrects a color difference component of the image signal using a correction amount of the color difference component calculated by the color difference component correction amount calculation unit. In claim 12,
An adjustment parameter storage unit that stores adjustment parameters of the color difference component;
When the luminance component before correction is Yin, the luminance component after correction is Yout, and the adjustment parameter is b,
The color difference component correction unit
An image processing apparatus, wherein (1-b × (1-Yout / Yin)) is used as a color difference gain, and the color difference component is corrected by multiplying the color difference component of the image signal by the color difference gain. An image display device that displays an image based on an image signal,
The image processing apparatus according to claim 1, wherein the image signal is corrected.
An image display device comprising: an image display unit that displays an image based on the image signal corrected by the image processing device. In claim 14,
An image display device comprising: a sensor for measuring a luminance of output light of the image display unit and a luminance of the external light. An image processing method for correcting an image signal supplied to an image display unit,
A luminance component correction amount calculating step for calculating a correction amount of a luminance component of the image signal only in accordance with a visual environment only for an image signal in a given luminance level range in a given spatial frequency band;
And a luminance component correction step of correcting the luminance component of the image signal using the correction amount calculated in the luminance component correction amount calculation step. In claim 16,
The luminance component correction amount calculating step includes:
An image processing method, wherein the correction amount is calculated by using a luminance ratio of external light and output light of the image display unit as the visual environment. In claim 17,
A frequency analysis step of analyzing a spatial frequency of a luminance component of the image signal,
The luminance component correction amount calculating step includes:
An image processing method, wherein a correction amount of a luminance component of the image signal is calculated according to the luminance ratio and an analysis result of the frequency analysis step. In claim 17 or 18,
An image processing method, wherein the luminance ratio is calculated based on luminance when the image display unit displays a black image and luminance when the image display unit displays a white image.