JP2000338922A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor capable of expressing rich gradation and capable of displaying image of rich contrast. SOLUTION: An image condition detecting part 9 of this image processor divides an amplitude level into a plurality of areas and classifies image conditions into a plurality of classifications depending on how much of the amplitude level of an inputted picture signal is included in each of the plurality of areas. A control part 10 controls an inverse gamma correction part 4 so as to apply an inverse gamma correction to the inputted picture signal in accordance with the classifications by the image condition detecting part 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode ray tube (CR)
T) Image processing devices used for matrix type display devices other than display devices, for example, plasma display panel display devices (PDP), field emission display devices (FED), liquid crystal display devices (LCD), etc., and in particular, inverse gamma correction The present invention relates to a video processing device capable of displaying a good video by using the same.

[0002]

2. Description of the Related Art An image signal such as a television signal has a CR signal.
Assuming display on a T display device, a non-linear process called gamma correction has been performed in advance. Therefore, in the case of a CRT display device, a correct (linear) luminance gradation is displayed without correcting the image signal. However, in the case of a PDP, FED, LCD, or the like other than the CRT display device, the image signal is displayed as an image signal. On the other hand, it is necessary to perform optimal correction for each display device. For example, in the case of a PDP, since the light emission characteristics are approximately proportional, it is necessary to provide an inverse gamma correction circuit to perform the inverse gamma correction.

A case of a PDP will be described as a conventional video processing apparatus. FIG. 6 is a block diagram showing a conventional PDP. Analog video signals (R, G, B) are input to the input terminals 1R, 1G, 1B, respectively. The A / D converter 2 converts the input R, G, B analog video signals into digital video signals. When the input signal is an interlace signal, the pixel conversion unit 3 converts the input signal into a progressive signal, and further converts the number of pixels in the horizontal and vertical directions into the number of display pixels of the display panel 6.

The inverse gamma correction unit 4 receives the input R, G,
Inverse gamma correction is performed on the B digital video signal. The gain control unit 5 controls the gain of the input R, G, B digital video signals. The display panel 6 has a driving unit 61, and the driving unit 61 drives the display panel 6 based on the input R, G, B digital video signals to display video.

[0005] In FIG. 7, (A) shows gamma: 1 /
This is a standard gamma correction characteristic of 2.2, which is a characteristic of input R, G, B analog video signals.
(B) is an inverse gamma correction characteristic of the inverse gamma: 2.2 applied by the inverse gamma correction unit 4. When inverse gamma correction of the characteristic shown in (B) is performed on a video signal having the characteristic shown in (A),
As shown in (C), the characteristic becomes linear.

Returning to FIG. 6, the output of the inverse gamma correction unit 4 is also input to the APL detection unit 7. The APL detection unit 7
An APL (average video level) of the input digital video signal is detected. The output of the ABL detection unit 7 is input to the control unit 8, and the control unit 8 transmits the AP detected by the ABL detection unit 7.
The gain in the gain control unit 5 is controlled according to L. As a result, the luminance of the digital video signal input to the display panel 6 is automatically limited according to the level of APL.
FIG. 8 shows a gain control characteristic by the APL. When the input level is 100% of the maximum luminance (that is, 25 for 8 bits)
In the case of 5), the luminance level (gain) is limited to, for example, 50%.

Normally, in a CRT display device, the number of gradations of an input image signal is 8 bits, that is, 256 gradations, which is sufficient for practical use. In a CRT display device, the ratio between the minimum value and the maximum value of the actual light emission luminance is determined by the fact that the input image signal is 25%.
Even at 6 gradations, it is larger than 1: 256 due to the inverse gamma characteristic of the CRT. In the case of a CRT display device, the maximum brightness of a relatively bright image having a high APL can be suppressed to a relatively low level by a beam limiter or the like.
In the case of an image having a locally bright portion in an image having a low PL and being relatively dark, the maximum luminance can be further increased.

On the other hand, in a PDP, gradation is controlled by the number of times of light emission, and the light emission luminance is approximately proportional to the number of times of light emission. That is, in the PDP, the displayable gradation is a linear 25
1: 256 for 6 gradations. Therefore, in PDP, C
The contrast is insufficient compared with the RT display device. Also,
In particular, the gradation of the dark part of the image is insufficient. In PDP,
Since the maximum luminance is limited to a constant value, when automatic luminance restriction is applied to a video having a high APL, the power is restricted by reducing the maximum luminance, so that the contrast is further reduced. As shown in FIG. 8, the gain is limited to a maximum of 50%.

[0009]

As described above, the PD
In matrix-type display devices other than CRT display devices such as P, FED, and LCD, there is a problem that the expressible gradation is insufficient and the contrast is low.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an image processing apparatus capable of displaying an image with rich gradation and high contrast that can be expressed.

[0011]

In order to solve the above-mentioned problems of the prior art, the present invention provides (a) an inverse gamma correction section (4) for applying an inverse gamma correction to an input video signal and outputting the result. ) And a gain control unit (5) for controlling the gain of the video signal input to the display unit (6), the amplitude level is divided into a plurality of regions, A video situation detection unit (9) for classifying the video situation of the input video signal into a plurality of categories depending on how much the amplitude level is included in each of the plurality of regions, and a classification by the video situation detection unit A control unit (10) for controlling the inverse gamma correction unit so as to perform inverse gamma correction on the input video signal in accordance with the following. (B) entered Inverse gamma correction unit (4), a display unit for outputting by performing inverse gamma correction on the image signal (6)
Control section (5) for controlling the gain of the video signal input to the video signal
An average video level detection unit (9) for detecting an average video level of the input video signal, and an average video level detected by the average video level detection unit. A control unit (10) for controlling the inverse gamma correction unit so as to vary the characteristic of the inverse gamma correction in the inverse gamma correction unit, and controlling the gain control unit to vary the characteristic of the gain control in the gain control unit; And a video processing apparatus characterized in that the video processing apparatus comprises:

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration example of a video processing device of the present invention, FIG. 2 is a diagram for explaining the operation of the video processing device of the present invention, and FIG. 3 is a diagram of a first embodiment of the video processing device of the present invention. FIG. 4 is a characteristic diagram for explaining the operation of the video processing device according to the second embodiment of the present invention, and FIG. 5 is a characteristic diagram for explaining the operation of the video processing device according to the third embodiment of the present invention. FIG. 4 is a characteristic diagram for explaining. In FIG. 1, the same parts as those in FIG. 6 are denoted by the same reference numerals.

In FIG. 1, input terminals 1R, 1G, 1B
Are respectively supplied with analog video signals (R, G, B). The A / D converter 2 converts the input R, G, B analog video signals into digital video signals. When the input signal is an interlace signal, the pixel conversion unit 3 converts the input signal into a progressive signal, and further converts the number of pixels in the horizontal and vertical directions into the number of display pixels of the display panel 6.

The inverse gamma correction unit 4 receives the input R, G,
Inverse gamma correction is performed on the B digital video signal. The gain control unit 5 controls the gain of the input R, G, B digital video signals. The display panel 6 has a drive unit 61. The drive unit 61 drives the display panel 6 based on the input R, G, B digital video signals to display video.

[0015] Further, R,
The G and B digital video signals are input to a video situation detection unit 9 newly provided according to the present invention. A in FIG.
The operation of the PL detection unit 7 is included in the video situation detection unit 9. The video status detection unit 9 detects the status of the input digital video signal as follows.

As shown in FIG. 2A, the video situation detecting section 9 obtains amplitude data at M points in the horizontal direction and N points in the vertical direction on the screen. Data in one horizontal period is shown in FIG.
become that way. Therefore, the data of FIG. 2B obtained in each horizontal period is divided into a plurality of regions, for example, three regions, by the amplitude level. And the area,
Find the ratio included in The ratios of the regions are defined as X%, Y%, and Z%, respectively. The video situation detection unit 9
At the same time, the APL is detected based on the amplitude data at the M × N points. The APL may be an average of one frame, an average of a plurality of frames, or an average of a plurality of lines.

Further, the image situation detecting section 9 includes an area,
The video contents are classified into, for example, the following five categories from the data analyzed for each of the. a: image with many dark parts ... Z> 50 b: image with many bright parts ... X> 50 c: image with many bright parts and dark parts ... X + Z> 50 and X, Z <30 d: light and dark parts Little video ... Y> 70 e: Standard video ... Other

The APL detected as described above and the classifications a to e
Is input to the control unit 10. The control unit 10 performs classification a to
The inverse gamma correction unit 4 is controlled according to e and APL. The control unit 10 controls the gain control unit 5 according to the APL as in the conventional case.

First Embodiment First, the inverse gamma correction in the inverse gamma correction unit 4 according to the classifications a to e will be described in detail. FIG. 3 shows the characteristics after the correction by the inverse gamma correction unit 4. The horizontal axis represents the input level, and the vertical axis represents the output of the inverse gamma correction unit 4. Inverse gamma correction curves a to e shown in FIG. 3 indicate characteristics selected by classifications a to e, respectively. The curve a has a large slope up to the input level P,
When the input level P is exceeded, the inclination is small. This is suitable for an image having many dark parts, which is classified as a. Curve b
Is a characteristic in which the inclination is small up to the input level Q and becomes large when the input level Q is exceeded.

The curve c has a characteristic that the inclination is large up to the input level P and higher than the input level Q, and the inclination is small in the middle of the curve c. The curve d has a characteristic that the slope is small up to the input level P and higher than the input level Q, and the slope is large in the middle of the curve d, and is suitable for an image having few bright and dark portions of the classification d. Curve e is the inverse gamma shown in FIG.
This is a standard linear characteristic when 2.2 is applied, and is suitable for a standard image of classification e.

As described above, the control unit 10 controls the inverse gamma correction unit 4 in accordance with the classifications a to e representing the state of the image detected by the image state detection unit 9, and controls the low-level portion up to the input level P. (I.e., a dark part), a large level part (i.e., a bright part) equal to or higher than the input level Q, and an input level P
The gradient of the inverse gamma correction curve is optimally set in the intermediate level portions from to Q. For example, in the case of the curve a, since the gradation of a dark part is emphasized, an image with a richer gradation can be expressed even with an image having many dark parts. Similarly, for the other curves b to e, an image rich in gradation suitable for each image is expressed. As described above, it is possible to express an image with rich gradation and high contrast.

<Second Embodiment> In the second embodiment, the control unit 1
0 controls the inverse gamma correction curve according to the APL as follows. FIG. 4A shows the APL in the gain control unit 5.
, And is the same as FIG. FIG.
(B) and (C) show characteristics when the inverse gamma correction curve is controlled according to the APL.

As shown in FIG. 4B, if the average video level (APL) exceeds R1, the slope is small up to the input level Q1, and if the average video level (APL) exceeds the input level Q1, the curve r1 has a large slope. If APL exceeds R2, which is larger than R1, the slope is even smaller until the input level Q2, and the input level Q2
Is greater than the curve r2, the slope is further increased. APL
If R exceeds R3 which is larger than R2, the slope is further smaller up to the input level Q3, and if it exceeds the input level Q3, the curve r3 has a larger slope.

As described above, when the gain is controlled by the gain control section 5, the inverse gamma correction curve is varied in accordance with the gain control amount, and the gradation of a bright portion is emphasized. Then
A decrease in contrast and a decrease in maximum luminance can be minimized without increasing power consumption. FIG.
(B) is a level detection point R of the average video level (APL).
1, R2, R3 and inflection points Q1, Q of the inverse gamma correction curve
2 and Q3 are matched, but as shown in FIG. 4C, the level detection points R1, R2, R
3 and the inflection points P1, P2, and P3 of the inverse gamma correction curve do not have to match.

<Third Embodiment> As in the second embodiment, when the gain is controlled by the gain control unit 5 and the gamma correction curve is varied according to the gain control amount, the gamma correction curve has a time constant. And change it gradually. As described above, if the APL is the maximum, the gain controller 5 reduces the gain to 50%. At this time, the gain control unit 5 does not rapidly change the gain from 100% to 50%.
As shown in (A), a predetermined time constant is provided, and the time is gradually changed continuously or in a plurality of steps. Along with this, the inverse gamma correction unit 4 also gradually changes the inverse gamma correction curve sequentially or continuously in a plurality of steps with a predetermined time constant, as shown in FIG. 5B. In this way, the gain and the inverse gamma correction curve change naturally due to the APL, and it is possible to eliminate a sense of discomfort.

As another embodiment, according to the value of APL,
The reverse gamma correction curves a to e shown in FIG. 3 may be selected. Further, when a plurality of video signals such as a personal computer signal, a game signal, and a broadcast signal are selectively inputted, and there is a certain tendency in the status of each video, FIG. 3 shows in accordance with the selected video signal. Inverse gamma correction curve a ~
e may be selected.

[0027]

As described in detail above, the video processing apparatus of the present invention divides the amplitude level into a plurality of regions, and to what extent the amplitude level of the input video signal is included in each of the plurality of regions. A video situation detection unit that classifies the video situation of the input video signal into a plurality of categories, and performs inverse gamma correction on the input video signal according to the classification by the video situation detection unit Since the control unit for controlling the inverse gamma correction unit is provided as described above, it is possible to display an image with rich gradation and high contrast that can be expressed.

An average video level detector for detecting the average video level of the input video signal, and characteristics of the inverse gamma correction in the inverse gamma corrector according to the average video level detected by the video level detector. While controlling the inverse gamma correction unit so as to vary, and a control unit that controls the gain control unit to vary the characteristics of the gain control in the gain control unit, the power consumption is suppressed,
A high-contrast image with rich expressable tones can be displayed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

FIG. 3 is a characteristic diagram for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a characteristic diagram for explaining the operation of the second embodiment of the present invention.

FIG. 5 is a characteristic diagram for explaining the operation of the third embodiment of the present invention.

FIG. 6 is a block diagram showing a conventional example.

FIG. 7 is a diagram for explaining inverse gamma correction.

FIG. 8 is a characteristic diagram showing gain control characteristics.

[Explanation of symbols]

 4 Inverse gamma correction unit 5 Gain control unit 6 Display panel (display unit) 9 Image condition detection unit (average image level detection unit) 10 Control unit 61 Drive unit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) BB05 CC03 DD03 EE29 FF09 GG01 GG09 JJ02 JJ04 JJ05

Claims (3)

[Claims] 1. An image processing apparatus comprising: an inverse gamma correction unit that performs inverse gamma correction on an input video signal and outputs the result; and a gain control unit that controls a gain of the video signal input to a display unit. Dividing the amplitude level into a plurality of regions, and classifying the video status of the input video signal into a plurality of classifications according to how much the amplitude level of the input video signal is included in each of the plurality of regions. And a control unit that controls the inverse gamma correction unit to perform inverse gamma correction on the input video signal according to the classification by the video status detection unit. A video processing device characterized by the above-mentioned. 2. An image processing apparatus comprising: an inverse gamma correction unit that performs inverse gamma correction on an input video signal and outputs the result; and a gain control unit that controls a gain of the video signal input to a display unit. An average video level detection unit that detects an average video level of the input video signal; and, based on the average video level detected by the average video level detection unit, a characteristic of the inverse gamma correction in the inverse gamma correction unit. A video processing apparatus comprising: a control unit that controls the inverse gamma correction unit so as to change the gain, and a control unit that controls the gain control unit so as to change a characteristic of gain control in the gain control unit. 3. A method according to claim 1, wherein when the characteristic of the inverse gamma correction in the inverse gamma correction unit and the characteristic of the gain control in the gain control unit are varied according to the average image level detected by the average image level detection unit. 3. The video processing apparatus according to claim 2, wherein the inverse gamma correction characteristic and the gain control characteristic are sequentially changed by giving the time constant of: