JPH0962227A - Image level correcting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance reproducibility of colors of the signals in a plasma display panel to which personal computer signals of 8-color display or the like are inputted. SOLUTION: Respective analog picture signals of red, green and blue from a personal computer are converted into digital picture signals by an A/D converting circuit 1b or the like after necessary processing is performed by an analog signal processing circuit 1a or the like. After necessary processing is performed on the digital picture signals by a digital signal processing circuit 1c, a level is corrected by a level correcting circuit 1e or the like. A level converting characteristic such as signal components not more than an intermediate value are all set on a zero level and signal components exceeding the intermediate value are set on a peak level of a dynamic range with a substantially intermediate value of the dynamic range as a boundary, is given to this level correcting circuit 1e or the like. Respective signals of red, green and blue becomes signals uniform in the peak level from the zero level by this level correction, and the degradation of reproducibility of colors by nonuniformity of levels can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video level correction circuit, and more particularly to digital video processing of a plasma display panel (hereinafter referred to as "PDP") which displays an image based on a digital video signal.

[0002]

2. Description of the Related Art FIG.
As shown in (A), there is one that outputs a color video signal in a form in which each of the red, green, and blue analog video signals has a value of either a black level or a peak level.
This signal corresponds to a luminance-order color bar signal in a general color video signal and has a maximum of eight colors (white, yellow, cyan, green, magenta, red, blue, and black). On the other hand, a video processing circuit of a PDP which displays an image based on a digital video signal is conventionally configured as shown in FIG. In the figure, the input analog video signal is subjected to required analog processing by an analog signal processing circuit 21, and then converted from an analog video signal to a digital video signal by an A / D conversion solution 22. The digital video signal is subjected to required digital processing by the digital signal processing circuit 23, and then gamma corrected by the gamma (γ) correction ROM 24. This gamma correction is performed in order to obtain an appropriate white balance in accordance with the emission characteristics of PDP. This gamma-corrected signal is sent to the PDP to display an image.

[0003]

However, the above-mentioned maximum of 8
When a personal computer signal composed of colors is displayed on the PDP, if gamma correction is performed in the same manner as with a normal video signal, correct coloration will not be achieved due to the peculiarity of this signal, and color reproducibility will be poor. Further, during A / D conversion, the red, green, and blue levels become uneven due to the influence of the power supply voltage of the A / D conversion circuit, etc., and the color reproducibility is further deteriorated. Therefore, PD
When a video signal such as the personal computer signal is displayed at P without degrading the color reproducibility, a process different from the conventional process is required. The present invention has been made under such a background, and mainly targets a personal computer signal,
An object of the present invention is to provide a video level correction circuit that prevents deterioration of color reproducibility.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a plasma for displaying an image based on a digital video signal converted from the analog video signal by using each of the analog video signals of red, green and blue such as a personal computer output as an input signal. In the digital image processing circuit of the display panel, the level is corrected so that all the digital signal components below the required level are set to the zero level, and the digital signal components exceeding the required level are set to the peak level in the digital image processing circuit. The present invention provides a video level correction circuit in which the level correction circuit is provided in the path of each of the red, green and blue digital video processing circuits.

[0005]

The red, green and blue analog video signals from the personal computer are converted into digital video signals by the A / D conversion circuit after the required analog signal processing. A level correction circuit corrects the level of the digital video signal after the required digital processing. This level correction circuit sets a level such that the signal level below the intermediate value is set to zero level, and the signal level above the intermediate value is set to the peak level of the dynamic range, with the value at the intermediate value of the dynamic range as a boundary. It has a conversion characteristic. By this level correction, each of the red, green and blue signals becomes a signal having a uniform peak level from the zero level.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A video level correction circuit according to the present invention will be described below with reference to the drawings. 1 is a block diagram of an essential part showing an embodiment of a video level correction circuit according to the present invention.
FIG. 6 is a level conversion characteristic diagram for each color signal for explaining the image level correction. FIG. 3 is a block diagram of the essential parts showing another embodiment of the video level correction circuit according to the present invention. In FIG. 1, 1 is a processing circuit for red video signals, 2 is a processing circuit for green video signals, and 3 is a processing circuit for blue video signals. Since these processing circuits have the same configuration, the configuration diagram of the green video signal processing circuit 2 and the blue video signal processing circuit 3 is omitted. In the red video signal processing circuit 1, 1a is an analog signal processing circuit that performs required processing for an input red video signal, 1b is an A / D conversion circuit that converts an analog signal from the analog signal processing circuit 1a into a digital signal, and 1c is A digital signal processing circuit for performing required processing on the digital signal from the A / D conversion circuit 1b. 1d is a level correction (1e) or gamma (γ) correction for the digital signal from the digital signal processing circuit 1c depending on the type of the signal. This is a conversion ROM that is any one of (1f).

In FIG. 3, 11 to 13 are the same as in FIG.
These are processing circuits for red video signals, green video signals, and blue video signals. For the same reason as in FIG. 1, the configuration diagram of the green video signal processing circuit 12 and the blue video signal processing circuit 13 is omitted. In the red video signal processing circuit 11, 11a, 11b and 11c are equivalent to 1a, 1b and 1c in FIG. 1, and 11d is a judgment of zero level or peak level for the signal level from the digital signal processing circuit. Section 11e is a first setting section for setting the output to zero level when the judgment of the judging section 11d is zero level, and 11f is a second setting section for setting the output to peak level when the judgment is peak level.
Is a setting unit.

Next, the operation of the present invention will be described by focusing on the red image signal. First, FIG. 1 will be described. In FIG. 1, the input red video signal is an analog signal processing circuit.
After the required analog processing in 1a, it is converted into a digital signal in the A / D conversion circuit 1b. The digital signal processing circuit 1c performs required digital processing on the digitized signal. The process up to this process is the same as the conventional process. The video signal processed by the digital signal processing circuit 1c is R for conversion.
Although it is sent to the OM1d, the ROM1d of FIG. 1 has two kinds of conversion characteristics, which are switched and used according to an input signal. That is, it is possible to process both a normal video signal and a personal computer signal (8 colors) as an input signal, and in the case of the former signal, a gamma correction unit 1f that performs gamma correction similar to the conventional one is used. In the case of the latter signal, the level correction unit 1e having the input / output conversion characteristic shown in FIG. 2 is used. The use of the two may be switched according to the input signal by the illustrated address signal. If the target input signal is only a personal computer signal, the ROM 1d need only be the level correction unit 1e.

The input / output conversion characteristic of the level correction unit 1e is the characteristic shown in FIG. FIG. 2 is an input / output conversion characteristic diagram when the digital video signal has an 8-bit configuration.
(B) and (C) are for red, green, and blue video signals, respectively. As shown, (A), (B) and (C) all have the same characteristics. In the case of the 8-bit configuration, the dynamic range is "0 to 255" and the intermediate value is "128". With this intermediate value (required level) as the boundary, the conversion output is set to zero level for input signal components below the intermediate value,
Input signal components exceeding the intermediate value are output as peak level "255". Even when the digital signal is other than the above-mentioned 8 bits, it is converted to a zero level or a peak level at a boundary between the approximately intermediate values of the dynamic range determined by the number of bits. By using such conversion characteristics, for example, as shown in FIG. 4A, red before level correction,
Of the green and blue video signals, even when the red video signal has a smaller amplitude than the green and blue video signals, the output of each level correction unit is 3 as shown in FIG. The colors are also adjusted to the same level of signal. By displaying the level-corrected signal on the PDP, deterioration of color reproducibility is prevented.
Also, when the levels of other color signals are low, the levels are similarly aligned. If the zero level or the peak level is an 8-bit signal, the former is “000000”.
00 ”and the latter is“ 11111111 ”(FIG. 4 etc.).

Next, FIG. 3 will be described. FIG. 3 is a block diagram when only the above-mentioned personal computer signals (8 colors) are targeted. Analog signal processing circuit 11a, A / D conversion circuit 11b
The digital signal processing circuit 11c has the same function as those of FIG. The judging section 11d judges the level of the signal from the digital signal processing circuit 11c as in the case of FIG.
That is, the determination unit 11d uses the required level as a reference, determines that all the digital signal components below the reference level are zero levels, and determines that the same signal components that exceed the reference level are peak levels. Output a judgment signal. Here, the required level is set to a substantially intermediate value of the dynamic range determined by the number of bits of the video signal, as in FIG. 1 (“128” for 8 bits). This determination unit 11
Based on the determination of d, when the zero level is determined, the output is set to the zero level by the first setting unit 11e. When the peak level is determined, the output is set to zero level by the second setting section 11f. This level correction is performed for each of the red, green and blue video signals. This achieves the same purpose as in FIG.

[0011]

As described above, according to the present invention, each analog video signal of red, green and blue takes a value of either zero level or peak level, such as a personal computer output. Input the same analog video signal (8 colors) as the input signal and below the required level in the digital video processing of the plasma display panel that displays an image based on the digital video signal converted from the analog video signal. All signal components are converted to zero level, and the same signal components exceeding the same required level are converted to peak levels, so that even if there is a level mismatch between red, green, and blue video signals, they are aligned to the same level. be able to. As a result, the problem of color reproducibility deterioration due to uneven level is solved, and a proper color image can be displayed. As described above, the present invention can contribute to improving the performance of the PDP in which the personal computer signal is input.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts showing an embodiment of a video level correction circuit according to the present invention.

FIG. 2 is an input / output level conversion characteristic diagram for explaining FIG. 1, in which (A), (B), and (C) are for a red video signal, a green video signal, and a blue video signal, respectively.

FIG. 3 is a block diagram of a main part of another embodiment of the video level correction circuit according to the present invention.

FIG. 4 is an explanatory diagram of a personal computer signal before and after level correction.

FIG. 5 is a principal block diagram showing an example of a conventional video processing circuit in a PDP.

[Explanation of symbols]

 1 Red video signal processing circuit 1a Analog signal processing circuit 1b A / D conversion circuit 1c Digital signal processing circuit 1d Conversion ROM 1e Level correction unit 1f Gamma (γ) correction unit 2 Green video signal processing circuit 3 Blue video signal processing circuit 11 Red video signal processing circuit 11d Judgment unit 11e First setting unit 11f Second setting unit

Claims (5)

[Claims] 1. A digital video processing circuit of a plasma display panel for displaying an image based on a digital video signal converted from the analog video signal for each of the red, green and blue analog video signals such as a personal computer output. , A level correction circuit that makes a level correction so that all the digital signal components below the required level are set to zero level and all the signal components exceeding the required level are set to the peak level are red. An image level correction circuit, which is provided in the path of each of the green and blue digital image processing circuits. 2. The video level correction circuit according to claim 1, wherein the level correction circuit is composed of a ROM. 3. The level correction circuit is composed of a ROM having both the characteristic required for gamma correction of a conventional general video signal and the characteristic required for level correction, and is switched to the required characteristic by addressing. The image level correction circuit according to claim 1, wherein 4. A digital video processing circuit of a plasma display panel for displaying an image based on a digital video signal converted from the analog video signal by using each of the red, green and blue analog video signals as an input signal for personal computer output or the like. Based on the required level, all the digital signal components below the reference level are determined to be zero level, and the same signal components exceeding the reference level are determined to be peak levels, and the determination signals are output respectively. A determination unit, a first setting unit that sets the output to a zero level when the determination signal from the determination unit represents a zero level, and an output to a peak level when the determination signal from the determination unit represents a peak level. The second setting section to set to red,
An image level correction circuit provided on the path of each of the green and blue digital image processing circuits. 5. The video level correction circuit according to claim 1, wherein the required level as the boundary is an intermediate value of a dynamic range determined by the number of bits of the digital video signal.