JP2007121541A - Image display device and image display method - Google Patents

Abstract

An image display apparatus and an image display method capable of efficiently suppressing a pseudo contour that occurs with expansion of a gradation range are provided.
An edge comparison unit (76) detects a pseudo contour generated by an expansion process by comparing two edge image data input from first and second edge detection units (74, 75), respectively. An extension adjustment value corresponding to the generation state of the pseudo contour is derived. The correction amount calculation unit 72 inputs the feature amount of the target frame from the feature amount extraction unit 71, derives a provisional extension rate based on this, and then extends the previous frame input from the edge comparison unit 76. The expansion rate is adjusted using the value, and the final expansion rate is calculated. The expansion processing unit 73 performs correction by multiplying the luminance value of each pixel included in the image data by the expansion rate calculated by the correction amount calculation unit 72, and outputs the corrected image data to the light valve driving unit 77. To do.
[Selection] Figure 1

Description

The present invention relates to an image display device that inputs an image signal and displays an image corresponding to the image signal, and an image display method.

As one form of an image display device, light emitted from a light source is modulated in accordance with an image signal by a light modulation device (liquid crystal light valve or the like), and the modulated light is enlarged and projected onto a screen or the like to display an image. It has been known. The light modulation device includes a plurality of pixels, and forms an image according to the image signal by controlling the light transmittance for each pixel according to the gradation information represented by the image signal.

Further, there has been proposed a projector provided with expansion means for correcting the gradation (transmittance) of each pixel in order to extend the effective gradation range (for example, Patent Document 1). According to this, for example, when displaying a dark image, the gradation range is expanded to the white side (bright side), thereby increasing the number of effective gradations (expanding the dynamic range) and improving the contrast. It becomes possible to make it. On the other hand, since the expansion process amplifies a subtle luminance change, it has a problem that a pseudo contour is likely to be generated in a region in the image where the luminance change is gradual. For this reason, the projector described in Patent Document 1 determines the proportion of non-natural images (images in which pseudo contours tend to occur) in the image by analyzing the histogram of the image. If the proportion is large, the expansion process is performed. Do not do.

JP 2004-101552 A

However, in the projector described in Patent Document 1, even when a pseudo contour does not actually occur, depending on the histogram of the image, the expansion process may not be performed. Have the problem of

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image display device and an image display method capable of efficiently suppressing a pseudo contour that occurs with expansion of a gradation range. There is.

The image display device of the present invention is characterized in that a first edge detection unit that detects a contour based on image data representing gradation information for each pixel, and that extracts a feature amount corresponding to the gradation information from the image data. An amount extraction unit; an expansion processing unit that corrects the image data based on the feature amount to expand the gradation range of the gradation information; and an image corresponding to the image data corrected by the expansion processing unit An edge for comparing the detection results of the first and second edge detectors, a second edge detector for detecting a contour based on the image data corrected by the decompression processor, A comparison unit and a correction amount adjustment unit that adjusts a correction amount by the extension processing unit based on a comparison result by the edge comparison unit so that extension of the gradation range is suppressed are provided.

According to this image display device, the correction amount adjustment unit is configured according to the comparison result by the edge comparison unit.
Since the correction amount for the image data is adjusted, it is possible to perform appropriate correction according to the generation state of the pseudo contour accompanying the decompression process, and the pseudo contour can be efficiently suppressed.

In this image display device, the edge comparison unit detects a contour generated by correction by the extension processing unit by comparing detection results of the first and second edge detection units, and the correction amount adjustment unit It is preferable that the correction amount be adjusted only when the edge comparison unit detects the contour generated by the correction.

According to this image display apparatus, only when the edge comparison unit detects a pseudo contour generated along with the expansion process, the correction amount adjustment unit adjusts the correction amount, so that no pseudo contour is generated. Nevertheless, the expansion of the gradation range is not suppressed.

The image display device of the present invention is characterized in that a first edge detection unit that detects a contour based on image data representing gradation information for each pixel, and that extracts a feature amount corresponding to the gradation information from the image data. An amount extraction unit; an expansion processing unit that corrects the image data based on the feature amount to expand a gradation range of the gradation information; and an outline based on the image data corrected by the expansion processing unit The extension processing unit corrects the second edge detection unit based on the comparison result of the second edge detection unit that detects the detection result, the edge comparison unit that compares the detection results of the first and second edge detection units, and the edge comparison unit. A smoothing processing unit that performs adjustment for smoothing gradation information on image data, and an image display unit that displays an image according to the image data adjusted by the smoothing processing unit. And

According to this image display device, since the smoothing unit adjusts the image data according to the comparison result by the edge comparison unit, it is possible to make an appropriate adjustment according to the generation state of the pseudo contour accompanying the expansion process. Thus, it becomes possible to efficiently suppress the pseudo contour generated in accordance with the expansion process.

In this image display device, the edge comparison unit detects a contour generated by correction by the extension processing unit by comparing detection results of the first and second edge detection units, and the smoothing processing unit It is preferable that the adjustment is performed on the image data only when the edge comparison unit detects the contour generated by the correction.

According to this image display device, since the smoothing unit adjusts (smooths) the image data only when the edge comparison unit detects the pseudo contour generated in the expansion process, the pseudo contour is generated. When there is no image, it is possible to suppress blurring of the image due to unnecessary smoothing processing.

In this image display device, the edge comparison unit compares the detection results of the first and second edge detection units, specifies the position of the contour generated by the correction by the extension processing unit, and performs the smoothing process. It is desirable that the unit adjusts gradation information in the vicinity of the specified position.

According to this image display apparatus, since the smoothing processing unit performs adjustment near the position where the pseudo contour is generated by the expansion process, it is possible to suppress the influence of the adjustment except near the position, and unnecessary smoothing processing is performed. This makes it possible to suppress blurring of the image.

In this image display device, the image display unit includes a light source, a light modulation device that modulates light emitted from the light source based on the input image data, light incident on the light modulation device,
And a light control means for adjusting at least one light amount of the light modulated by the light modulation device in accordance with a correction amount in the extension processing unit.

According to this image display apparatus, since the light control means is provided, it is possible to suppress a change in luminance due to expansion of the gradation range by light control by the light control means.

The image display method of the present invention includes a first edge detection step for detecting a contour based on image data representing gradation information for each pixel, and a feature for extracting a feature amount corresponding to the gradation information from the image data. An amount extraction step, an expansion processing step for correcting the image data based on the feature amount in order to expand the gradation range of the gradation information, and an image corresponding to the image data corrected in the expansion processing step The detection results of the first and second edge detection steps are compared with the image display step of displaying the image, the second edge detection step of detecting the contour based on the image data corrected in the extension processing step And a correction amount adjusting step of adjusting a correction amount for the image data in the extension processing step based on a comparison result in the edge comparison step so that extension of the gradation range is suppressed. Characterized in that it comprises.

According to this image display method, in the correction amount adjustment step, the correction amount for the image data is adjusted according to the comparison result in the edge comparison step. The pseudo contour can be efficiently suppressed.

The image display method of the present invention includes a first edge detection step for detecting a contour based on image data representing gradation information for each pixel, and a feature for extracting a feature amount corresponding to the gradation information from the image data. An amount extraction step; an expansion processing step for correcting the image data based on the feature amount to expand a gradation range of the gradation information; and an outline based on the image data corrected in the expansion processing step. Correction in the extension processing step based on the comparison result in the edge comparison step, the edge comparison step in which the detection results in the first and second edge detection steps are compared, and the comparison result in the edge comparison step A smoothing process for adjusting the gradation information for the image data that has been adjusted, and an image display process for displaying an image according to the image data adjusted in the smoothing process Features To.

According to this image display method, in the smoothing process step, the image data is adjusted according to the comparison result in the edge comparison step. Therefore, it is possible to make an appropriate adjustment according to the generation state of the pseudo contour accompanying the expansion process. Thus, the pseudo contour can be efficiently suppressed.

Further, when the image display device and the image display method described above are constructed using a computer provided in the image display device, the present invention provides a program for realizing the function, or the program as described above. It is also possible to configure in the form of a recording medium recorded so as to be readable by a computer. Recording media include flexible disks and CD-ROMs
Readable by the computer such as magneto-optical disk, IC card, ROM cartridge, punch card, printed matter printed with barcodes, internal storage device of the projector (memory such as RAM and ROM), external storage device, etc. Various types of media can be used.

(First embodiment)
Hereinafter, as an image display apparatus according to the first embodiment of the present invention, a projector that modulates light emitted from a light source according to an image signal and enlarges and projects the modulated light onto a screen or the like will be described. . The projector according to the present embodiment can expand (enlarge) the gradation range of the image to the bright side (white side) when displaying a dark image, thereby increasing the number of effective gradations. (The dynamic range is expanded) and the contrast can be improved. In addition, a light control means capable of reducing (light control) the amount of light from the light source is provided, and it is possible to suppress a change in luminance associated with the expansion process.

FIG. 1 is a block diagram for explaining a circuit configuration of the projector according to the present embodiment.
As shown in FIG. 1, the projector 1 includes an image signal processing unit 70, a feature amount extraction unit 71, a correction amount calculation unit 72, an expansion processing unit 73, a first edge detection unit 74, a second edge detection unit 75, An edge comparison unit 76, a light valve driving unit 77, a dimming element driving unit 78, an optical device 80, and the like are provided. The projector 1 includes a computer including a CPU, a ROM, a RAM, and the like, and each of the units 70 to 76 is realized by the CPU operating according to a control program stored in the ROM.

First, the optical device 80 will be described in detail with reference to the drawings.
FIG. 2 is a configuration diagram showing a schematic configuration of the optical device 80, and shows an optical path from the light emitted from the light source to the screen.
As shown in FIG. 2, the optical device 80 includes an illumination optical system 10, a color light separation optical system 20, a relay optical system 30, three liquid crystal light valves 40R, 40G, and 40B as light modulation devices, and a cross dichroic. A prism 50 and a projection lens 60 are provided.

The illumination optical system 10 includes a light source 11 including a discharge type light source lamp such as an ultrahigh pressure mercury lamp and a metal halide lamp, a first lens array 12, a second lens array 13, a polarization conversion element 14, and a superimposing lens 15. And a light control element 16. The light bundle emitted from the light source 11 is divided into a number of minute light bundles by the first lens array 12 in which minute lenses 12a are arranged in a matrix. The second lens array 13 and the superimposing lens 15 have three liquid crystal light valves 40R, 40G, each of which the divided light bundles are illumination targets.
It is equipped to irradiate the entire 40B. For this reason, each light bundle is superimposed by the liquid crystal light valves 40R, 40G, and 40B, and the entire liquid crystal light valves 40R, 40G, and 40B are illuminated almost uniformly.

Here, a dimming element 16 is provided in the optical path between the first and second lens arrays 12 and 13. The light control element 16 can narrow the light emitted from the first lens array 12 by the rotation of the louver 16a, and blocks a part of the light beam divided by the first lens array 12. be able to. For this reason, the amount of light that illuminates the liquid crystal light valves 40R, 40G, and 40B is substantially uniformly limited in accordance with the aperture amount of the light control element 16.

The polarization conversion element 14 has a function of aligning with polarized light having a specific polarization direction so that the light from the light source 11 can be efficiently used by the liquid crystal light valves 40R, 40G, and 40B. The polarized light emitted from the illumination optical system 10 enters the color light separation optical system 20.

The color light separation optical system 20 includes a first dichroic mirror 21, a first reflection mirror 22, and a second dichroic mirror 23, and the light emitted from the illumination optical system 10 has a different wavelength range. Separate into three colors of light. The first dichroic mirror 21 transmits substantially red light and reflects light having a shorter wavelength than the transmitted light. The red light R that has passed through the first dichroic mirror 21 is reflected by the first reflecting mirror 22 to illuminate the liquid crystal light valve 40R for red light.

Of the light reflected by the first dichroic mirror 21, green light G is reflected by the second dichroic mirror 23 and illuminates the liquid crystal light valve 40G for green light. Further, the blue light B passes through the second dichroic mirror 23, passes through the relay optical system 30, and illuminates the liquid crystal light valve 40B for blue light.

In addition, since the path | route of blue light B becomes long compared with the path | route of other color lights, in order to suppress that the illumination efficiency to liquid crystal light valve 40B falls by the divergence of a light beam, blue light B The relay optical system 30 is provided in the path. The relay optical system 30 includes an incident side lens 31, a second reflection mirror 32, a relay lens 33, a third reflection mirror 34,
An exit side lens 35 is provided. The blue light B emitted from the color light separation optical system 20 converges in the vicinity of the relay lens 33 by the incident side lens 31 and diverges toward the emission side lens 35.

Each of the liquid crystal light valves 40R, 40G, and 40B includes a liquid crystal panel 41 in which liquid crystal is sealed between a pair of transparent substrates, and the liquid crystal panel 41 has an inner surface for each minute region (pixel) with respect to the liquid crystal. Transparent electrodes (pixel electrodes) to which a driving voltage can be applied are formed in a matrix. An incident-side polarizing plate 42 and an emitting-side polarizing plate 43 are attached to the incident-side surface and the emitting-side surface of the liquid crystal panel 41, respectively. The incident side polarizing plate 42 and the exit side polarizing plate 43 can transmit only polarized light in a specific polarization direction, respectively, and the incident side polarizing plate 42 transmits polarized light in the polarization direction aligned by the polarization conversion element 14. It is possible. Therefore, most of each color light incident on each of the liquid crystal light valves 40R, 40G, and 40B is transmitted through the incident-side polarizing plate 42 and is incident on the liquid crystal panel 41.

Here, when a driving voltage corresponding to an image signal is applied to each pixel of the liquid crystal panel 41, light incident on the liquid crystal panel 41 is modulated according to the driving voltage and has a different polarization direction for each pixel. It becomes polarized light. Of this polarized light, only the polarization component that can be transmitted through the exit-side polarizing plate 43 is emitted from the liquid crystal light valves 40R, 40G, and 40B. That is, the liquid crystal light valve 40R
, 40G, 40B transmit incident light with different transmittances for each pixel according to the image signal, so that an optical image having a gradation is formed for each color light. Liquid crystal light valve 40R, 40
Optical images made up of the respective color lights emitted from G and 40B are incident on the cross dichroic prism 50.

The cross dichroic prism 50 combines the optical images of the respective colors emitted from the liquid crystal light valves 40R, 40G, and 40B for each pixel to form an optical image representing a color image. The optical image synthesized by the cross dichroic prism 50 is enlarged and projected on the screen SC by the projection lens 60 and displayed as an image.

Returning to FIG. 1, the image signal processing unit 70 can input image signals of various formats from the outside. The input image signals are converted into luminance values (floor levels) of the pixels of the liquid crystal light valves 40R, 40G, and 40B. To digital image data consisting of key information). The converted image data is output to the feature amount extraction unit 71, the decompression processing unit 73, and the first edge detection unit 74.

The feature amount extraction unit 71 extracts various feature amounts based on the brightness of the image, that is, the luminance value of each pixel, for each frame (one screen) from the input image data. As feature amounts, the maximum luminance value (white peak value) within one frame and APL (Averag) representing the average luminance within one frame
e Picture Level: average image level) is extracted or derived, and is output to the correction amount calculation unit 72.

The correction amount calculation unit 72 inputs the white peak value and APL extracted by the feature amount extraction unit 71, and also inputs an expansion adjustment value (to be described later) from the edge comparison unit 76, and sets a correction amount for correcting the image data. Guide (details will be described later). As the correction amount, a magnification (expansion rate) when expanding each luminance value of the image data and a dimming amount (reduced light amount) by the dimming element 16 are calculated for each frame. It is output to the element driving unit 78. In the present embodiment, the expansion rate is determined to be in the range of 1 to 2 times.

The expansion processing unit 73 performs expansion processing on the image data input from the image signal processing unit 70 to expand the luminance value of each pixel at the expansion rate calculated by the correction amount calculation unit 72, and the processed image data Is output to the second edge detecting unit 75 and the light valve driving unit 77.

The first and second edge detection units 74 and 75 are configured by digital filters that function as Laplacian filters, for example, and detect the contours included in the image based on the input image data, as contour information. Edge image data is generated. Edge image data
Data representing edge strength for each pixel. The first edge detection unit 74 generates edge image data based on image data input from the image signal processing unit 70, that is, image data before decompression processing. The edge image data is output to the edge comparison unit 76. The second edge detection unit 75 receives the image data after the expansion processing from the expansion processing unit 73 to generate edge image data, and outputs the edge image data to the edge comparison unit 76.

The edge comparison unit 76 inputs 2 from the first and second edge detection units 74 and 75, respectively.
By comparing the two edge image data, the pseudo contour generated in accordance with the expansion process is detected. Specifically, with respect to two edge image data, a difference in edge strength is taken for each pixel, and it is determined that a pseudo contour is generated in an area (pixel group) where the difference exceeds a predetermined value (threshold value). . After that, the expansion adjustment value α corresponding to the number of pixels constituting the pseudo contour is set as an LUT (Look Up Table).
) Etc. and output to the correction amount calculation unit 72. Here, the expansion adjustment value α is set in a range of 0 to 1, and is 1 when a pseudo contour is not generated. When the pseudo contour is generated, the larger the number of pixels constituting the pseudo contour is, the more the extension adjustment value α is. It takes a small value.

Here, the method by which the correction amount calculation unit 72 derives the correction amount (expansion rate, light control amount) will be described in detail.
First, the correction amount calculation unit 72 receives the feature quantity of the frame of interest from the feature amount extraction unit 71, derives the extension ratio G ₀ provisional based on this. When extending the brightness value to the white side,
If it is excessively expanded, whiteout occurs and the image is deteriorated. However, if the white peak value is small, it is possible to extend the luminance value greatly without generating whiteout. For this reason, it is desirable to increase the expansion rate G ₀ for a frame with a smaller white peak value. Also,
As the value of APL is away from small white peak value, since overexposure is limited pixel generated by the expansion process, as the frame APL is small, it is desirable to consideration to extension ratio G ₀ increases.

Next, the correction amount calculation unit 72 uses the expansion adjustment value α one frame before input from the edge comparison unit 76 and adjusts the expansion rate G ₀ by the following equation (1), thereby obtaining a final expansion rate G _New.
To decide.
G _New = 1 + α (G ₀ −1) (1)
As shown in the equation (1), when the expansion adjustment value α is 1, that is, when no pseudo contour is generated, G _New = G ₀ , and the provisional expansion rate G ₀ based on the feature amount is final as it is. The expansion rate is G _New . Further, the final expansion rate G _New is smaller than the provisional expansion rate G _{0 as} the expansion adjustment value α is smaller (the number of pixels constituting the pseudo contour is larger), so that the expansion process is suppressed. When the expansion adjustment value α is 0, G _New = 1 and no expansion process is performed. When calculating the expansion rate G _New for the first frame, since the expansion adjustment value α is undetermined, the final expansion rate G _New is determined only from the feature amount of the frame (G _New = G
₀ ). As described above, the correction amount calculation unit 72 adjusts the provisional expansion rate G ₀ based on the feature amount according to the comparison result by the edge comparison unit 76, and thus, as the correction amount adjustment unit of the present invention. Function.

Thereafter, the correction amount calculation unit 72 guides the light control amount by the light control element 16. Here, the derivation to be the amount of dimming varies depending on the expansion ratio G _New (extension ratio G _New there is a need to reduce the amount of light larger) for, to derive the quantity of light adjustment based on the expansion rate G _New You may do it, and the expansion rate G _New
Similarly to the above, it may be derived based on the feature amount and the extension adjustment value α.

The expansion processing unit 73 applies a correction amount calculation unit 72 to the luminance value of each pixel included in the image data.
When the correction is performed by multiplying the expansion rate G _New calculated in step S4 and the corrected image data is output to the light valve driving unit 77, the light valve driving unit 77 responds to the image data by the liquid crystal light valves 40R, 40G, and 40B. Drive. In addition, the dimmer element driving unit 78 causes the louver 1 of the dimmer element 16 so that the dimmer element 16 reduces the light amount by the dimming amount calculated by the correction amount calculator 72.
6a is driven.
Through the above operation, an image with an enhanced contrast feeling and an enhanced contrast feeling is displayed on the screen SC with appropriate luminance. The optical device 80, the light valve driving unit 77, and the dimming element driving unit 78 function as an image display unit of the present invention.

As described above, according to the projector 1 of the present embodiment, the following effects can be obtained.

(1) According to the projector 1 of the present embodiment, the correction amount calculation unit 72 reduces the expansion rate G _New in the next frame as the number of pixels constituting the pseudo contour generated by the expansion processing decreases, and the expansion processing unit The expansion process by 73 is suppressed. That is, since appropriate correction is performed according to the occurrence state of the pseudo contour, the pseudo contour can be efficiently suppressed.
(2) According to the projector 1 of the present embodiment, the correction amount calculation unit 72 includes the edge comparison unit 76.
Compares the edge image data before and after the expansion process, and only when it is determined that a pseudo contour has occurred, the expansion process by the expansion processing unit 73 is suppressed. For this reason, when the pseudo contour is not generated, the improvement of the contrast feeling due to the expansion process is not suppressed.

(3) According to the projector 1 of the present embodiment, since the light control means (the light control element 16 and the light control element driving unit 78 for driving the light control element 16) is provided, the change in luminance accompanying the expansion of the gradation range is detected. It is possible to suppress the light by the light control by the light control means.

(Second Embodiment)
The image display apparatus (projector) according to the second embodiment of the present invention will be described below.
FIG. 3 is a block diagram for explaining a circuit configuration of the projector according to the present embodiment.
As shown in FIG. 3, the projector 1 of this embodiment includes a smoothing processing unit 79 in addition to the components of the projector of the first embodiment. The smoothing processing unit 79 is configured by a digital filter or the like that functions as a low-pass filter. By smoothing the luminance value of each pixel included in the image data, it is possible to suppress the pseudo contour generated by the expansion processing. It has become.

The correction amount calculation unit 72 calculates the expansion rate and the dimming amount based on the feature amount extracted by the feature amount extraction unit 71, and outputs them to the expansion processing unit 73 and the dimming element driving unit 78. Decompression processing unit 73
Performs an expansion process on the image data using the input expansion rate, and outputs the processed image data to the second edge detection unit 75 and the smoothing processing unit 79.

As in the first embodiment, the edge comparison unit 76 compares the edge image data before and after the expansion process input from the first and second edge detection units 74 and 75 and determines whether or not a pseudo contour is generated by the expansion process. Detect. Specifically, for two edge image data, a difference in edge strength is taken for each pixel, and it is determined that a pseudo contour is generated in a region where the difference exceeds a predetermined value (threshold value). The edge comparison unit 76 specifies the position of the region where the pseudo contour is generated based on the position of each pixel, and sets the filter constant of the smoothing processing unit 79 to the number of pixels constituting the pseudo contour using an LUT or the like. In response, the position information and the filter constant are output to the smoothing processing unit 79.
Here, the filter constant is determined so that the cut-off frequency of the low-pass filter decreases as the number of pixels constituting the pseudo contour increases. That is, the stronger the smoothing process is performed, the more pseudo contours are generated. Further, when it is determined that no pseudo contour has occurred, the filter constant is determined so that the smoothing process is not substantially performed.

Based on the position information and filter constant input from the edge comparison unit 76, the smoothing processing unit 79 performs filter processing using a low-pass filter in the vicinity of the region where the pseudo contour is generated on the image data input from the expansion processing unit 73. By performing the smoothing process), the luminance value is smoothed to suppress the false contour (make it inconspicuous). The processed image data is output to the light valve driving unit 77 and projected as an image.

As described above, according to the projector 1 of the present embodiment, the following effects can be obtained.

(1) According to the projector 1 of the present embodiment, the smoothing processing unit 79 performs stronger smoothing processing as the number of pixels constituting the pseudo contour generated by the expansion processing increases. That is, since an appropriate smoothing process is performed in accordance with the generation state of the pseudo contour, the pseudo contour can be efficiently suppressed.
(2) According to the projector 1 of the present embodiment, only when the edge comparison unit 76 compares the edge image data before and after the extension processing and determines that a pseudo contour has occurred, the smoothing processing unit 7
9 is subjected to the smoothing process. For this reason, it is possible to suppress blurring of an image due to unnecessary smoothing processing when no pseudo contour has occurred.

(3) According to the projector 1 of the present embodiment, when the edge comparison unit 76 compares the edge image data before and after the extension process and determines that a pseudo contour has occurred, the smoothing processing unit 79 Since the smoothing process is performed in the vicinity of the area where the contour is generated, the influence of the smoothing can be suppressed in the area other than the vicinity of the area, and the blurring of the image due to the unnecessary smoothing process can be suppressed. It becomes possible.

(Modification)
In addition, you may change embodiment of this invention as follows.
In the first embodiment, the provisional expansion rate G ₀ derived from the feature amount in the target frame and 1
From the extension adjustment value α derived based on the edge image data obtained in the previous frame, the equation (1)
) Determines the expansion rate G _New by, but used for one frame, and decompression processing performed in extension ratio G ₀ interim in order to determine the expansion rate G _New, the determined expansion rate G _New The decompression process may be performed twice, and the image data after the second process may be output to the light valve driving unit 77. According to this, it becomes possible to suppress the pseudo contour without being delayed by one frame.

In the embodiment, the expansion rate G _New and the cut-off frequency of the low-pass filter are changed according to the number of pixels constituting the pseudo contour, but these are changed according to the edge strength after the expansion processing. You may make it do.

In the second embodiment, the filter size of the low-pass filter may be changed according to the number of pixels constituting the pseudo contour. Further, the attenuation rate of the filter may be increased instead of decreasing the filter cutoff frequency in accordance with the number of pixels constituting the pseudo contour.

In the above-described embodiment, edge detection is performed using a Laplacian filter, but detection may be performed using other methods such as Fourier transform and wavelet transform.

In the embodiment, the white peak value and A are used as the feature values for deriving the expansion rate and the light control amount.
Although PL is used, the feature amount to be used is not limited to the above. For example, various statistical values such as the minimum luminance value (black peak value), the most frequent luminance value, and the variance in one frame may be used. Is possible.

In the above-described embodiment, the configuration in which the gradation range is expanded to the white side (bright side) has been described.
It is good also as a structure which can expand | extend to the black side (dark side), and can extend | expand to both sides of black and white. When only the black side is expanded, there is no need for dimming by the dimmer 16.

In the above embodiment, a discharge type light source lamp such as an ultra-high pressure mercury lamp or a metal halide lamp is used as the light source 11, but other light sources such as an LED light source composed of an LED (light emitting diode) may be used.

In the above-described embodiment, a projector that projects an image on an external screen or the like is described as an example of the image display device. However, a rear screen that integrally includes a transmissive screen and projects an image on the back side thereof. It can also be applied to a projector. The present invention can also be applied to other image display devices such as a liquid crystal display device.

In the above-described embodiment, the dimming element 16 that reduces the amount of light by the louver 16a is used for dimming the light of the light source 11, but other diaphragm mechanisms such as diaphragm blades, or light emission of the light source and the backlight A control circuit capable of controlling the amount of light can also be used. Further, a liquid crystal element or electrochromic glass whose light transmittance can be changed according to the applied voltage is used, in the middle of the optical path from the light source 11 to the transmissive screen SC, or when the screen SC is transmissive. May be provided on the front surface thereof.

In the embodiment, as the light modulation device, transmissive liquid crystal light valves 40R, 40G,
40B is used, but LCOS (Liquid Crystal On Silico) is a reflection type light modulator.
n) etc. can also be used. Also, a DMD (registered trademark of Texas Instruments) (digital micromirror device) that modulates the light emitted from the light source by controlling the emission direction of the incident light for each micromirror can be used. .

FIG. 2 is a block diagram for explaining a circuit configuration of the projector according to the first embodiment. The block diagram which shows schematic structure of an optical apparatus. The block diagram for demonstrating the circuit structure of the projector which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projector, 11 ... Light source, 16 ... Light control element, 40R, 40G, 40B ... Liquid crystal light valve, 70 ... Image signal processing part, 71 ... Feature-value extraction part, 72 ... Correction amount calculation part, 73 ... Decompression processing part , 74 ... 1st edge detection part, 75 ... 2nd edge detection part, 76 ... Edge comparison part, 77 ... Light valve drive part, 78 ... Dimming element drive part, 79 ... Smoothing process part, 80 ... Optical apparatus .

Claims (8)

A first edge detection unit for detecting a contour based on image data representing gradation information for each pixel;
A feature amount extraction unit that extracts a feature amount according to the gradation information from the image data;
An expansion processing unit for correcting the image data based on the feature amount in order to expand the gradation range of the gradation information;
An image display unit for displaying an image according to the image data corrected by the expansion processing unit;
A second edge detection unit for detecting a contour based on the image data corrected by the extension processing unit;
An edge comparison unit for comparing detection results of the first and second edge detection units;
A correction amount adjustment unit that adjusts a correction amount by the extension processing unit based on a comparison result by the edge comparison unit so that extension of the gradation range is suppressed;
An image display device comprising: The image display device according to claim 1, wherein the edge comparison unit detects a contour generated by correction by the extension processing unit by comparing detection results of the first and second edge detection units. The correction amount adjustment unit adjusts the correction amount only when the edge comparison unit detects the contour generated by the correction. A first edge detection unit for detecting a contour based on image data representing gradation information for each pixel;
A feature amount extraction unit that extracts a feature amount according to the gradation information from the image data;
An expansion processing unit for correcting the image data based on the feature amount in order to expand the gradation range of the gradation information;
A second edge detection unit for detecting a contour based on the image data corrected by the extension processing unit;
An edge comparison unit for comparing detection results of the first and second edge detection units;
A smoothing unit that performs adjustment for smoothing gradation information on the image data corrected by the extension processing unit based on the comparison result by the edge comparison unit;
An image display unit for displaying an image according to the image data adjusted by the smoothing unit;
An image display device comprising: The image display device according to claim 3, wherein the edge comparison unit detects a contour generated by correction by the extension processing unit by comparing detection results of the first and second edge detection units. The smoothing processing unit performs the adjustment on the image data only when the edge comparison unit detects the contour generated by the correction. 5. The image display device according to claim 3, wherein the edge comparison unit compares the detection results of the first and second edge detection units, and the contour generated by correction by the extension processing unit. And the smoothing processing unit adjusts gradation information in the vicinity of the specified position. The image display device according to any one of claims 1 to 5,
The image display unit
A light source;
A light modulation device that modulates light emitted from the light source based on the input image data;
A light control means for adjusting at least one light amount of light incident on the light modulation device and light modulated by the light modulation device according to a correction amount in the extension processing unit;
An image display device comprising: A first edge detection step of detecting a contour based on image data representing gradation information for each pixel;
A feature amount extraction step of extracting a feature amount according to the gradation information from the image data;
An expansion process step of correcting the image data based on the feature amount in order to expand the gradation range of the gradation information;
An image display step for displaying an image according to the image data corrected in the expansion processing step;
A second edge detection step of detecting a contour based on the image data corrected in the extension processing step;
An edge comparison step for comparing the detection results in the first and second edge detection steps;
A correction amount adjustment step of adjusting a correction amount for the image data in the extension processing step based on a comparison result in the edge comparison step so that extension of the gradation range is suppressed;
An image display method comprising: A first edge detection step of detecting a contour based on image data representing gradation information for each pixel;
A feature amount extraction step of extracting a feature amount according to the gradation information from the image data;
An expansion process step of correcting the image data based on the feature amount in order to expand the gradation range of the gradation information;
A second edge detecting step of detecting a contour based on the image data corrected in the extension processing step;
An edge comparison step for comparing the detection results in the first and second edge detection steps;
Based on the comparison result in the edge comparison step, a smoothing process step for performing adjustment for smoothing gradation information on the image data corrected in the extension processing step;
An image display step for displaying an image according to the image data adjusted in the smoothing step;
An image display method comprising:

Images