JPH10105115A - Gradation adaptive type error diffusion processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an accurate gradation adaptive type error diffusing process by eliminating errors between light emission luminance characteristics used for error diffusion and light emission luminance characteristics of a display panel. SOLUTION: When an error diffusing circuit 11 performs an error diffusing process for an (n)-bit input video signal and inputs the result as an (m)-bit display signal to a panel driving circuit 42, a panel driving signal outputted from this panel driving circuit 42 is inputted to a display panel 44 (e.g. PDP) to display an artificial half-tone image. When a pulse driving state signal outputted from a panel driving monitor circuit 46 which monitors the driving state of the display panel 44 is inputted to a luminance deviation quantity arithmetic circuit 32, this luminance deviation quantity arithmetic circuit 32 finds a luminance deviation quantity (value corresponding to light emission luminance characteristics) based on the panel driving state signal and outputs it as a signal for an error diffusing processing to the error diffusing circuit 11, so the driving state of the display panel 44 can correctly be grasped to find light emission luminance characteristics used for the error diffusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error diffusion processing device for displaying a pseudo halftone image by error diffusion in a display device such as a PDP display device.

[0002]

2. Description of the Related Art Recently, as a thin and lightweight display device, P
DP (plasma display panel) has been attracting attention. The driving method of this PDP is completely different from the conventional CRT driving method, and is a direct driving method using digitized video input signals. Therefore, the luminance gradation emitted from the panel surface is determined by the number of bits of the signal to be handled.

[0003] PDPs are AC type and DC having fundamental characteristics different from each other.
Type. In the AC type PDP, there was only a report on the gradation display up to a maximum of 64 gradations at the prototype level, but a future 256 gradation method using the address / display separation type driving method (ADS subfield method) has been proposed. I have.

One frame (or one field) in the ADS subfield method is composed of eight subfields having relative luminance ratios of, for example, 1, 2, 4, 8, 16, 32, 64, and 128. Display of 256 gradations is performed by a combination of screen luminances. Each subfield is composed of an address period in which data for one refreshed screen is written and a sustain period for determining a luminance level of the subfield. In the address period, first, wall charges are initially formed on each pixel at the same time for the entire screen, and then a sustain pulse is applied to the entire screen to perform display. The brightness of the subfield is proportional to the number of sustain pulses and is set to a predetermined brightness. In this way 2
56 gradation display is realized.

In the above-described AC driving method, as the number of gradations increases, the number of bits in an address period as a preparation period for lighting and emitting light in the panel within one frame period increases. The period becomes relatively short, and the maximum luminance decreases. As described above, since the luminance gradation emitted from the panel surface is determined by the number of bits of the signal to be handled, if the number of bits of the signal to be handled is increased, the image quality is improved, but the emission luminance is reduced, and conversely, the signal to be handled is reduced. If the number of bits is reduced, the light emission luminance increases, but the gradation display decreases and the image quality deteriorates.

The error diffusion process for minimizing the shading error between the input signal and the emission luminance while reducing the number of bits of the output drive signal from the number of bits of the input signal is a process for expressing a pseudo halftone. , Which is used when expressing gradation with a small number of gradations.

FIG. 2 shows a conventional general error diffusion processing apparatus.
As shown in FIG. 1, the apparatus includes an error diffusion circuit 11 including an error amount calculation unit 12 and a processing circuit unit 13, and a light emission luminance characteristic measurement unit 14. The processing circuit unit 13 outputs n (for example, The reproduction error generated in the past from the original pixel is added to the video signal of the original pixel of 8 bits, and converted into video data (display signal) of m (for example, 4) bits (m ≦ n−1).
The error amount is output to the DP (display panel of the image display unit) side, and the error amount calculation unit 12 calculates an error amount from the video data using the emission luminance characteristic from the emission luminance characteristic measurement unit 14 and processes it as a reproduction error signal. The image is output to the circuit unit 13, and the PDP displays a pseudo halftone image due to error diffusion. The light emission luminance characteristic measuring section 14 is mainly composed of a ROM or the like, and measures and stores the light emission luminance characteristic of the PDP from representative input data (drive signal) as shown in FIG.

As a result, as shown in FIG. 3, despite the instantaneous light emission luminance level as shown by the solid line staircase, the light emission luminance level is actually recognized in an averaged state. = X corrected luminance line.

However, the light emission luminance characteristic of a display device such as a PDP changes depending on data to be displayed, and may be the light emission luminance characteristic as shown in FIG. In such a case, in the method of adjusting to the typical light emission luminance characteristics as shown in FIG. 3, data other than when the representative characteristics are obtained cannot be adapted to the gradation characteristics. There has been a problem that a pseudo contour due to gradation non-adaptation appears.

[0010]

In order to solve such a problem, the present applicant has already proposed a gradation adaptive type error diffusion processing apparatus as shown in FIG.
6279). In the device shown in FIG. 5, instead of the light emission luminance characteristic provided from the ROM as in the prior art, 1
Alternatively, the light emission luminance characteristic for each of a plurality of frames is calculated based on a luminance deviation characteristic obtained from a load factor of input data of a display device such as a PDP, and the error diffusion is performed by updating the light emission luminance characteristic for each one or a plurality of frames. , Pseudo contours are prevented from appearing.

More specifically, a video processing section 16 for outputting video data to a video display section mainly composed of a PDP.
Is composed of an error diffusion circuit 11 and a light emission luminance characteristic acquisition circuit 20, the error diffusion circuit 11 is composed of a processing circuit unit 13 and an error amount calculation unit 12, and the light emission luminance characteristic acquisition circuit 20 is a display number counter 21, It comprises a display area ratio calculation unit 22, a light emission luminance deviation characteristic measurement unit 23, and a luminance deviation amount calculation unit 24.

The processing circuit section 13 adds a reproduction error generated in the past from the original pixel to the n (for example, 8) bit video signal of the original pixel input to the input terminal 10, and outputs m (for example, 4) bit video data. And output it to the PDP side. The error amount calculation unit 12 uses the light emission luminance characteristics (characteristics corresponding to the luminance deviation amount) output from the light emission luminance characteristic acquisition circuit 20,
An error amount with respect to the video data output from the processing circuit unit 13 is calculated and output to the processing circuit unit 13 as a reproduction error signal.

The number-of-displays counter 21 counts the number of displays in one or a plurality of frames based on video data output from the processing circuit unit 13 to the PDP side. The display area ratio (Sk) is obtained by dividing the count number (display dot number) by the total dot number. Then, the luminance deviation characteristic of each bit is obtained by the light emission luminance deviation characteristic measuring section 23, and the luminance deviation amount of each level is obtained by the luminance deviation amount calculating section 24 based on the luminance deviation characteristic. This luminance deviation amount is updated every one or a plurality of frames and transmitted to the error amount calculation unit 12 of the error diffusion circuit 11.
The error diffusion circuit 11 performs an error diffusion process based on the emission luminance characteristic of the luminance deviation amount, and outputs the result to the PDP side.

As described above, the luminance deviation amount is determined by the error diffusion circuit 11.
Is fed back to the error amount calculation unit 12, and an error diffusion process based on the emission luminance characteristic corresponding to the luminance deviation amount is performed. For this reason, even if the light emission luminance characteristic changes depending on the data to be displayed, the light emission luminance characteristic does not match the typical light emission luminance characteristic, so that the gradation characteristic can be sufficiently adapted to ever-changing display data. Things.

However, in the proposed tone-adaptive error diffusion processing device shown in FIG. 5, since the light emission luminance characteristic is predicted and calculated by the video processor 16, an error between the light emission luminance characteristic and the actual light emission luminance characteristic of the PDP occurs. There was a slight problem that there was.

The present invention has been made in view of the above-mentioned problems, and eliminates an error from the light emission luminance characteristics of an actual display panel (for example, a PDP) so that a more accurate error diffusion process can be performed. It is an object of the present invention to obtain a key adaptive error diffusion processing device.

[0017]

The invention according to claim 1 is
An error diffusion circuit that performs an error diffusion process on an input video signal, a panel drive circuit that outputs a drive signal to a display panel based on an output signal of the error diffusion circuit, and a pseudo-halftone based on an output signal of the panel drive circuit A display panel that displays an image, and a panel drive monitoring circuit that monitors a drive state of the display panel and outputs a panel drive state signal,
The error diffusion circuit performs an error diffusion process using an output signal of the panel drive monitoring circuit.

When an input video signal is subjected to error diffusion processing by an error diffusion circuit and input to a panel drive circuit, a drive signal is input from the panel drive circuit to a display panel, and a pseudo halftone image is displayed on the display panel. When the panel driving monitoring circuit monitors the driving state of the display panel and outputs a panel driving state signal, the error diffusion circuit performs error diffusion processing using the panel driving state signal, so that the driving state of the display panel can be correctly grasped. , Accurate error diffusion processing can be performed.

According to a second aspect of the present invention, there is provided an error diffusion circuit for performing an error diffusion process on an input video signal, a panel drive circuit for outputting a drive signal to a display panel based on an output signal of the error diffusion circuit, and the panel drive circuit. A display panel for displaying a pseudo halftone image based on an output signal of the driving circuit, a panel driving monitoring circuit for monitoring a driving state of the display panel and outputting a panel driving state signal, and an output signal of the panel driving monitoring circuit And a luminance deviation calculating circuit for obtaining a luminance deviation amount based on the error diffusion amount and outputting the luminance deviation amount to the error diffusion circuit as a signal for error diffusion processing.

When an input video signal is subjected to error diffusion processing by an error diffusion circuit and input to a panel driving circuit, a driving signal is input from the panel driving circuit to a display panel, and a pseudo halftone image is displayed on the display panel. When the panel drive state signal from the panel drive monitoring circuit is input to the luminance deviation amount calculation circuit, the luminance deviation amount (a value corresponding to the light emission luminance characteristic) obtained based on the panel drive state signal is input to the error diffusion circuit. Therefore, the driving state of the display panel can be correctly grasped to determine the light emission luminance characteristics, and more accurate error diffusion processing can be performed.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, the error diffusion circuit adds a reproduction error generated in the past from the original pixel to the input video signal of the n-bit original pixel, and outputs the m-bit image signal. A processing circuit unit for converting and outputting the display signal of (m ≦ n-1), an error amount calculating unit for calculating an error amount from an output signal of the processing circuit unit and the luminance deviation amount, and outputting the calculated error amount to the processing circuit unit; It consists of.

According to a fourth, fifth, sixth or seventh aspect of the present invention, in the first, second or third aspect of the invention, a panel drive current and a panel drive voltage for outputting a panel drive state signal from a panel drive circuit to a display panel. A signal obtained by converting the panel drive current or the panel drive voltage into a digital signal or constant data obtained by converting the digital signal using the CPU.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIG. In FIG. 1, reference numeral 30 denotes a video processing unit, and 40 denotes a video display unit. The image processing unit 30 includes an error diffusion circuit 11
And the luminance deviation amount calculation unit 32.
Reference numeral 1 denotes an error amount calculation unit 12 and a processing circuit unit 13. The image display unit 40 includes a panel driving unit 42, a PDP
And a panel drive monitoring unit 46. The panel drive monitoring unit 46 includes an A / D conversion circuit 4
8 and a CPU 50.

The processing circuit section 13 of the error diffusion circuit 11
As in the case of FIG. 5, the reproduction error generated in the past from the original pixel is added to the n-bit video signal of the original pixel input to the input terminal 10 and converted into an m-bit display signal (video data). Output to the image display unit 40 side. The error amount calculation unit 12 of the error diffusion circuit 11
Using the luminance deviation amount (a value corresponding to the light emission luminance characteristic) output from the luminance deviation amount calculation unit 32, the processing circuit unit 1
3 is configured to calculate an error amount with respect to a display signal output from the processing circuit 3 and output the same to the processing circuit unit 13 as a reproduction error signal.

The panel drive unit 42 of the video display unit 40
Is configured to convert an m-bit display signal output from the processing circuit unit 13 into an m-bit sub-field screen display signal, and output this to the display panel 44 as a drive signal.

The panel drive monitoring section 46 has an A / D
A conversion circuit 48 converts a panel drive signal such as a panel drive current or a panel drive voltage output from the panel drive section 42 to the display panel 44 into a digital signal,
U50 is configured to convert the digital signal output from the A / D conversion circuit 48 into corresponding constant data, and to output this as a panel drive state signal to the luminance deviation amount calculation unit 32. The constant data is, for example, data that becomes 0 for a panel drive signal in the case of no load, and 1, 2, 3,... For a panel drive signal in the case of a load that increases stepwise from no load. These data are set and stored in a memory (for example, an LUT) using the panel drive signal as an address, and are read out by the CPU 50.

Next, the operation of the above embodiment will be described.
As in the case of FIG. 5, the n-bit video signal input to the input terminal 10 is added with a reproduction error that occurred in the past from the original pixel in the processing circuit unit 13 and converted into an m-bit display signal. The signal is input to the drive unit 42 and is input to the error amount calculation unit 12.

The error amount calculator 12 is provided with a luminance deviation amount calculator 3.
Using the luminance deviation amount (a value corresponding to the light emission luminance characteristic) output from the second processing unit 2, an error amount with respect to the display signal output from the processing circuit unit 13 is calculated, and the processing circuit unit 13 calculates a reproduction error signal.
Output to The panel drive unit 42 converts the m-bit display signal output from the processing circuit unit 13 into an m-bit sub-field screen display signal and outputs the signal to the display panel 44. Display tonal images.

The panel drive monitoring section 46 converts a panel drive signal output from the panel drive section 42 to the display panel 44 into a digital signal by the A / D conversion circuit 48 for each frame or a plurality of frames. The digital signal output from the A / D conversion circuit 48 is converted into corresponding constant data (luminance constant) and output to the luminance deviation amount calculation unit 32 as a panel driving state signal. Then, the luminance deviation amount calculation circuit 32 obtains the luminance deviation amount (a value corresponding to the light emission luminance characteristic) based on the panel driving state signal and outputs this to the error amount calculation unit 12, so that the display panel driving state is obtained. , And the light emission luminance characteristic can be obtained, and more accurate error diffusion processing can be performed.

In the above embodiment, the panel drive signal output from the panel drive circuit to the display panel is converted into a digital signal, and the converted signal is converted by the CPU into constant data. The case where the panel drive state signal is output to the arithmetic unit has been described, but the present invention is not limited to this. The panel drive state signal is a signal that indicates the panel drive state by monitoring the display panel drive state. Good. For example, a panel drive current or a panel drive voltage output from the panel drive circuit to the display panel may be used as a panel drive state signal, or a signal obtained by converting a panel drive signal (panel drive current or panel drive voltage) into a digital signal is used for panel drive. It may be a status signal.

In the above embodiment, the error diffusion circuit is set to n
A processing circuit unit that adds a reproduction error generated in the past from the original pixel to the input video signal of the original pixel, converts the display signal into an m-bit (m ≦ n−1) display signal, and outputs the display signal. Although the description has been given of the case where the error diffusion unit is configured to calculate the error amount from the output signal and the luminance deviation amount and output the calculated error amount to the processing circuit unit, the present invention is not limited thereto. Any method may be used as long as the error diffusion processing is performed.

In the above embodiment, the CPU of the panel drive monitoring section converts the digital signal output from the A / D conversion circuit into the corresponding constant data (luminance constant), and sends it as a panel drive state signal to the luminance deviation amount calculation section. Although the present invention is configured to output the data, the present invention is not limited to this.
The CPU of the panel drive monitoring unit may be configured to perform the calculation of the luminance deviation amount calculation unit by using the calculation function described above, and the luminance deviation amount calculation unit may be omitted. Alternatively, the CPU of the panel drive monitoring unit may be configured to perform calculations of the luminance deviation amount calculation unit and the error amount calculation unit, and the luminance deviation amount calculation unit and the error amount calculation unit may be omitted.

In the above embodiment, the case where the display panel of the video display unit is a PDP has been described. However, the present invention is not limited to this, and the present invention is also applicable to the case of a digital display panel (for example, a liquid crystal display panel). Can be.

[0034]

According to the present invention, claim 1 and dependent claims 3 to 3
The invention according to 7 includes an error diffusion circuit, a panel drive circuit, a display panel, and a panel drive monitoring circuit. When an input video signal is subjected to error diffusion processing by the error diffusion circuit and input to the panel drive circuit, the panel drive circuit When a drive signal is input to the display panel, a pseudo halftone image is displayed on the display panel, and a panel drive status signal is output from the panel drive monitoring circuit, the error diffusion circuit performs an error diffusion process using the panel drive status signal. With this configuration, it is possible to accurately grasp the driving state of the display panel and perform accurate error diffusion processing, and to prevent the appearance of a false contour as in the case of the proposed invention shown in FIG. Can be.

Claim 2 and dependent claims 3 to 7
The invention according to the present invention comprises an error diffusion circuit, a panel drive circuit, a display panel, a panel drive monitoring circuit and a luminance deviation amount calculation circuit, and when an input video signal is subjected to error diffusion processing by the error diffusion circuit and input to the panel drive circuit, When a driving signal is input from the panel driving circuit to the display panel, a pseudo halftone image is displayed on the display panel, and a panel driving state signal from the panel driving monitoring circuit is input to the luminance deviation calculating circuit, the luminance deviation calculating is performed. Since the luminance deviation amount (value corresponding to the light emission luminance characteristic) obtained from the circuit based on the panel drive state signal is input to the error diffusion circuit, the drive state of the display panel is correctly grasped and the light emission luminance characteristic is obtained. Can be requested. Therefore, more accurate error diffusion processing can be performed, and the appearance of a pseudo contour can be prevented as in the case of the already proposed invention shown in FIG.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a gradation adaptive error diffusion processing device according to the present invention.

FIG. 2 is a block diagram of a conventional error diffusion processing device.

FIG. 3 is a characteristic diagram showing a typical example of light emission luminance characteristics.

FIG. 4 is a characteristic diagram showing another example of light emission luminance characteristics.

FIG. 5 is a block diagram of a previously proposed error diffusion processing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Input terminal, 11 ... Error diffusion circuit, 12 ... Error amount calculation part, 13 ... Processing circuit part, 14 ... Emission luminance characteristic measurement part, 16, 30 ... Video processing part, 20 ... Emission luminance characteristic acquisition circuit, 21 ... Display number counter, 22: display area ratio calculation unit, 23: emission luminance deviation characteristic measurement unit, 24
... Luminance deviation amount calculation unit 32 ... Luminance deviation amount calculation circuit
40: image display unit, 42: panel drive unit, 44: display panel (for example, PDP), 46: panel drive monitoring unit, 48: A / D conversion circuit, 50: CPU, PDP
... Plasma display panel.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiji Matsunaga 1116 Suenaga, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu General Limited (72) Inventor Toru Aida 1116 Suenaga, Takatsu-ku, Kawasaki-shi, Kanagawa Fujitsu General Limited

Claims (7)

[Claims] An error diffusion circuit for performing an error diffusion process on an input video signal, a panel drive circuit for outputting a drive signal to a display panel based on an output signal of the error diffusion circuit, and an output signal of the panel drive circuit A display panel that displays a pseudo halftone image based on the display panel, and a panel drive monitoring circuit that monitors a drive state of the display panel and outputs a panel drive state signal. A gradation adaptive type error diffusion processing device, wherein an error diffusion process is performed using an output signal. 2. An error diffusion circuit for performing an error diffusion process on an input video signal, a panel drive circuit for outputting a drive signal to a display panel based on an output signal of the error diffusion circuit, and an output signal of the panel drive circuit. A display panel for displaying a pseudo-halftone image based on the display panel; a panel drive monitoring circuit for monitoring a drive state of the display panel and outputting a panel drive state signal; and a luminance deviation amount based on an output signal of the panel drive monitor circuit. And a luminance deviation amount calculation circuit for outputting the signal as a signal for error diffusion processing to the error diffusion circuit. 3. An error diffusion circuit adds a reproduction error generated in the past from an original pixel to an input video signal of an n-bit original pixel,
a processing circuit unit for converting the display signal into an m-bit (m ≦ n-1) display signal and outputting the converted signal; an error amount calculated from the output signal of the processing circuit unit and the luminance deviation amount and output to the processing circuit unit 3. The gradation adaptive error diffusion processing device according to claim 1, further comprising an arithmetic unit. 4. A gradation adaptive error diffusion processing device according to claim 1, wherein the panel drive state signal is a panel drive current output from the panel drive circuit to the display panel. 5. A gradation adaptive error diffusion processor according to claim 1, wherein the panel drive state signal is a panel drive voltage output from the panel drive circuit to the display panel. 6. A gradation adaptive error according to claim 1, wherein the panel drive state signal is a signal obtained by converting a panel drive current or a panel drive voltage output from the panel drive circuit to the display panel into a digital signal. Diffusion processing equipment. 7. A panel drive state signal converts a panel drive current or a panel drive voltage output from a panel drive circuit to a display panel into a digital signal, and converts the converted signal to a CPU signal.
4. The gradation adaptive error diffusion processing device according to claim 1, wherein the data is converted into constant data by using a constant.