JP3593799B2 - Error diffusion circuit of multiple screen display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a digital display device (display device) having a non-linear gradation characteristic such as a PDP (plasma display panel) or an LCD (liquid crystal display panel) for displaying a plurality of pseudo halftone screens by an error diffusion method. It relates to an error diffusion circuit.
[0002]
[Prior art]
Recently, PDPs have attracted attention as thin and lightweight display devices. The driving method of this PDP is completely different from the conventional CRT driving method, and is a direct driving method using a digitized video input signal. 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 classified into two types, AC type and DC type, which have different basic characteristics.
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 by the address / display separation type driving method (ADS subfield method) has been proposed. I have.
[0004]
One frame (or one field) in the ADS subfield method is composed of eight subfields having a relative luminance ratio of, for example, 1, 2, 4, 8, 16, 32, 64, 128, and has a luminance of eight screens. Is performed to display 256 gradations. Each subfield includes 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. Thus, 256 gradation display is realized.
[0005]
In the AC driving method described above, as the number of gradations increases, the number of bits in the address period as a preparation period for lighting and emitting light in the panel within one frame period increases. And the maximum brightness decreases.
[0006]
As described above, the luminance gradation emitted from the panel surface is determined by the number of bits of the signal to be handled. Therefore, 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 If the number of bits is reduced, the light emission luminance increases, but the gradation display is reduced and the image quality is reduced.
[0007]
In order to solve the above problem, a circuit for performing an error diffusion process is used. This error diffusion process is a process for expressing a pseudo halftone, and is used for expressing shading with a small number of gradations. A circuit that uses such an error diffusion process for a multi-screen display device has conventionally been configured as shown in FIG. 8 or FIG.
[0008]
In FIG. 8, a video signal a for a screen A (for example, a moving image) and a video signal b for a screen B (for example, a still image) are synthesized by a synthesis circuit 10, and the synthesized signal is input via an input terminal 12 to an error diffusion circuit. Input to 14. In the error diffusion circuit 14, the vertical adder 16 and the horizontal adder 18 incorporate a reproduction error that has occurred in the past into the composite signal input to the input terminal 12 to obtain a diffused output signal, which is led to the output terminal 20, and An error component is detected from the diffused output signal by the component detection unit 22, and the detected error component is sent to an m-line delay unit 24 and a first coefficient unit (a coefficient unit for multiplying a coefficient K1 (for example, 1/2) smaller than 1) 26. The detected error component is output to the vertical adder 16 via an n-dot delay unit 28 and a second coefficient unit (a coefficient unit for multiplying a coefficient K2 (for example, 1/2) smaller than 1) 30 by the horizontal direction. By outputting to the direction adding unit 18, a reproduction error generated in the past is incorporated.
[0009]
The spread output signal output from the output terminal 20 is supplied to the PDP via a bit conversion circuit (not shown) that performs a process of reducing the number of bits. Therefore, when a composite video signal for two screens (for screens A and B) of p (for example, 8) bits is input to the input terminal, the error diffusion circuit 14 performs an error diffusion process, and a bit conversion circuit (not shown). The number of bits is reduced to q (for example, 4) bits, and the PDP displays two screens, screen A and screen B, in one screen as shown in FIG.
[0010]
However, when the error diffusion circuit 14 performs an error diffusion process on video signals (for example, a and b) for a plurality of screens and displays a plurality of screens based on pseudo halftone display, the error component of one screen becomes the error component of another screen. There is a problem in that the image quality is adversely affected and the image quality is reduced. For example, in the error diffusion circuit 14 shown in FIG. 8, in the screen A and the screen B in which the pseudo halftone is displayed by the error diffusion processing, as shown in FIG. There is a problem that the image on the screen B, which should be present, flickers.
[0011]
Also, in FIG. 10, video signals a, b, c, and d for screens A, B, C, and D are synthesized by a synthesizing circuit 10a, and a pseudo intermediate signal is input to the output side of the synthesizing circuit 10a with respect to the input video signal. A through circuit 32 that passes the image signal without performing the halftone process, a halftone display circuit 34 that performs a pseudotone process on the input video signal by the systematic dither method, and a pseudo halftone process by the error diffusion method on the input video signal. The output side of these circuits 32, 34 and 14a is connected via a selection circuit 36 to a PDP (not shown) as a display device.
[0012]
The error diffusion circuit 14a is configured similarly to the error diffusion circuit 14 of FIG. 8 and performs the same operation. The selection circuit 36 selects which halftone display circuit to use based on the supplied processing selection signal. For example, the processing selection signal is composed of 2-bit signals “00”, “01”, and “10” for selecting use of the through circuit 32, the halftone display circuit 34, and the error diffusion circuit 14a. Which of the error diffusion circuit 14a, the halftone display circuit 34, and the through circuit 32 is applied to each of the video signals a, b, c, and d based on the processing selection signals "10", "01", and "00". Select whether to use.
[0013]
For example, the use of the error diffusion circuit 14a for the input video signals a and b, the use of the halftone display circuit 34 for the input video signal c, and the use of the through circuit 32 for the input video signal d. Are respectively selected. For this reason, as shown in FIG. 11, the PDP is displayed in a screen A (for example, a moving image) and a screen B (for example, a still image) displayed in pseudo halftone by the error diffusion method, and displayed in pseudo halftone by the systematic dither method. Four screens, a screen C and a screen D in which pseudo halftone processing is not performed, are displayed.
[0014]
However, as in the case of FIG. 8, there is a problem that an error component of a certain screen adversely affects an error component of another screen, thereby deteriorating the image quality. For example, in the error diffusion circuit 14a in FIG. 10, in the screen A and the screen B in which pseudo halftone display is performed by the error diffusion method, as shown in FIG. There is a problem that the image on the screen B, which should be present, flickers.
[0015]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and in a multi-screen display apparatus that displays a plurality of pseudo halftone screens by performing error diffusion processing on a video signal for multi-screen display, It is an object of the present invention to display a plurality of pseudo halftone screens without being affected by components.
[0016]
[Means for Solving the Problems]
The invention according to claim 1 is an error diffusion circuit that performs an error diffusion process on an input video signal for a plurality of screens and displays a plurality of pseudo halftone screens on a display device. An adding unit that obtains a diffused output signal by incorporating the error component detecting unit that detects an error component from the diffused output signal obtained by the adding unit;A screen switching detection unit that detects a screen switching signal for switching each screen of the plurality of pseudo halftone screens,thisScreen switching detectorofScreen switching signalWhen there is a constant value irrelevant to the error component detected by the error component detection unit,Screen switching signalWhen there is no error component control unit, an error component control unit that outputs an error component detected by the error component detection unit, and a delay unit that delays an output signal of the error component control unit and outputs the signal to the addition unit as an error component generated in the past. It is characterized by becoming.
[0017]
The addition unit incorporates an error component generated in the past into the input video signal and outputs a diffusion output signal, and the error component detection unit detects an error component from the diffusion output signal,The screen switching detection unit detects a screen switching signal for switching each of the plurality of pseudo halftone screens.thisScreen switching detectorofScreen switching signalWhen there is, the error component control unit outputs a constant value (for example, “0”) irrelevant to the error component detected by the error component detection unit,Screen switching detectorofScreen switching signalWhen there is no error component, the error component control unit outputs the error component detected by the error component detection unit. The delay unit delays the output signal of the error component control unit and outputs the delayed signal to the adding unit as an error component generated in the past.
[0018]
For this reason, when a pseudo halftone screen is displayed by a plurality of error diffusion processes by outputting a diffusion output signal to a display device (for example, a PDP), an error component incorporated in the input video signal has a constant value at the boundary between the screens. (For example, “0”), and the influence of the error component generated in the error diffusion processing of a certain screen does not propagate to another screen. In an area other than the boundary between screens, an error component incorporated in the input video signal becomes an error component detected by the error component detection unit, and error diffusion processing is performed.
Therefore, each of the plurality of screens displayed by the multi-screen display device can perform pseudo halftone display by the error diffusion method without being affected by the error components of each other, and the image quality can be improved.
[0019]
The screen switching signal detected by the screen switching detection unit isFor example, a plurality of types of input video signals (for example, a plurality of channels) can be easily extracted from a synthesis circuit that generates input video signals for a plurality of screens by synthesizing the input video signals.Therefore, the point where the screen switching is performed can be easily detected.
[0020]
Claim2The invention according to the error diffusion circuit comprises a plurality of halftone display circuits for performing pseudo halftone processing on input video signals for a plurality of screens, a selection circuit is coupled to the output side of the plurality of halftone display circuits, and A video signal for displaying a plurality of pseudo halftone screens from the output side of the selection circuit by supplying a selection signal to the selection circuit for selecting which of a plurality of halftone display circuits to use for each of the signals Wherein the plurality of halftone display circuits include an error diffusion circuit, and the processing selection signal selects the use of the error diffusion circuit for two or more of the input video signals. The error diffusion circuit includes a processing selection signal, and the error diffusion circuit incorporates an error component generated in the past into the input video signal to obtain a diffusion output signal, and detects an error component from the diffusion output signal obtained by the addition unit. An error component detection unit, a process selection detection unit that detects switching of a process selection signal for selecting the use of an error diffusion circuit, and a constant output irrespective of the error component of the error component detection unit when there is a detection output from the process selection detection unit. An error component control unit that outputs a value and outputs an error component of the error component detection unit when there is no detection output, and a delay unit that delays an output signal of the error component control unit and outputs the output signal to the addition unit. It is characterized by becoming.
[0021]
For this reason, when a plurality of pseudo halftone screens are displayed by error diffusion processing by outputting a diffusion output signal to a multi-screen display device (for example, a PDP), an error component incorporated in the input video signal is present at the boundary between the screens. It becomes a constant value (for example, “0”), and an error component generated in the error diffusion processing of a certain screen does not propagate to another screen via a boundary. In an area other than the boundary between screens, an error component incorporated in the input video signal becomes an error component detected by the error component detection unit, and error diffusion processing is performed.
Therefore, each of the plurality of screens displayed by the multi-screen display device can perform pseudo halftone display by the error diffusion method without being affected by the error components of each other, and the image quality can be improved.
[0022]
Claim3The invention according to claim1 or 2In the invention, the addition unit is weighted and added to the output target pixel by the multi-valued error of the surrounding pixels, and the addition unit is further provided with a vertical addition unit and a horizontal addition unit in order to further reduce the grayscale error between the input video signal and the emission luminance. And an m-line delay unit for delaying the output signal of the error component control unit by m (m is a positive integer) lines, and an output signal of the error component control unit by n (n is a positive integer) A first coefficient unit configured to multiply the output of the m-line delay unit by a coefficient K1 (a constant equal to or less than 1) and output the result to the vertical adder unit, and an output of the n-dot delay unit Multiplied by a coefficient K2 (K1 + K2 = 1), and outputs the result to the horizontal addition unit.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a first embodiment of the present invention, in which the same parts as those in FIG.
In FIG. 1, reference numeral 10 denotes a combining circuit that combines a video signal a for a screen A (for example, a moving image) and a video signal b for a screen B (for example, a still image).
[0024]
An error diffusion circuit 40 has an input terminal 12 to which a composite video signal synthesized by the synthesis circuit 10 is input. A vertical adder 16 and a horizontal adder 18 are sequentially connected to the input terminal 12. An output terminal 20 is connected to an output side of the horizontal adder 18 and an error component detector 22. Are combined. An error component control unit 42 is coupled to an output side of the error component detection unit 22. An m-line delay unit 24 and a first coefficient unit 26 are sequentially coupled to an output side of the error component control unit 42. The n-dot delay unit 28 and the second coefficient unit 30 are sequentially connected, and the output side of the first and second coefficient units 26 and 28 is connected to the vertical addition unit 16 and the horizontal addition unit 18.
[0025]
A screen switching detection unit 44 detects a screen switching signal for switching between the screen A and the screen B. The detection signal detected by the screen switching detection unit 44 is supplied to the error component control unit 42 as a control signal. ing. The error component control unit 42 outputs a constant value “0” irrelevant to the error component detected by the error component detection unit 22 when there is a detection signal of the screen switching detection unit 44, When there is no detection signal 44, the error component detected by the error component detection unit 22 is output.
[0026]
Next, the operation of the embodiment of FIG. 1 will be described with reference to FIGS.
The video signal a for the screen A and the video signal b for the screen B are combined by the combining circuit 10, and the combined signal is input to the error diffusion circuit 40 via the input terminal 12. The error diffusion circuit 40 outputs a video signal from the output terminal 20 by incorporating the error component generated in the past into the composite signal input to the input terminal 12 by the vertical direction addition unit 16 and the horizontal direction addition unit 18. Outputs to a PDP via a bit conversion circuit (a circuit for reducing the number of bits, not shown), so that the PDP is composed of two screens A and B in one screen as shown in FIG. indicate.
[0027]
The error component detection unit 22 detects an error component from the diffused output signal obtained on the output side of the horizontal direction addition unit 18 and outputs the error component to the error component control unit 42.
The screen switching detection unit 44 detects screen switching by differentiating the input screen switching signal as shown in FIG. 2A, and uses the screen switching detection signal as shown in FIG. 2B as a control signal. Output to the error component control unit 42.
Therefore, when the screen switching detection signal is input (when there is a pulse signal), the error component control unit 42 outputs “0” irrespective of the error component output from the error component detection unit 22 as an error component. However, when there is no input of the screen switching detection signal (when there is no pulse signal), the error component output from the error component detection unit 22 is output as it is.
[0028]
The error component output from the error component control unit 42 is delayed by m lines by the m-line delay unit 24, multiplied by the coefficient K1 (for example, １ ／) by the first coefficient unit 26, and input to the vertical direction addition unit 16. An n-dot delay unit 28 delays the signal by n dots, a second coefficient unit 30 multiplies the coefficient by K2 (for example, １ ／), and inputs the result to the horizontal adder 18, where an error component generated in the past is incorporated.
[0029]
As described above, the screen switching detection section 44 detects a screen switching signal for switching between the screen A and the screen B, and when there is no detection signal, the error component detected by the error component detecting section 22 is detected by the delay sections 24 and 28 and Output to the adders 16 and 18 via the coefficient units 26 and 30, and when there is a detection signal, output from the error component detection unit 22 to the adders 16 and 18 via the delay units 24 and 28 and the coefficient units 26 and 30. Since the error component is set to “0”, the error component becomes “0” at the boundary area (a) between the screen A and the screen B as shown in FIG. To the screens B and A of FIG.
[0030]
In the above-described embodiment, the case where a composite signal of the video signals a and b for the two screens A and B is input and two screens are displayed on the same screen of the PDP has been described, but the present invention is not limited to this. Instead, it can be used in a case where a video signal for a plurality of screens is input and a plurality of screens are displayed on the same screen of a PDP. For example, as shown in FIGS. 4 and 5, the video signals a, b, and c for the three screens A, B, and C are synthesized by the synthesis circuit 10a, and the synthesized signal is subjected to error diffusion processing by the error diffusion circuit 40. And outputs the video signal for pseudo halftone display to the PDP, and sets the error component output from the error component detection unit 22 to the addition units 16 and 18 to “0” when there is a screen switching signal detection signal. I do. For this reason, the error component is set to “0” in the regions (b), (c), and (d) at the boundaries of the three screens A, B, and C, and the error components due to the error diffusion processing of the screens A, B, and C are changed to other screens. Can be prevented.
[0031]
In the above embodiment, when the detection signal of the screen switching detection unit is present, the error component control unit sets “0” irrelevant to the value of the error component detected by the error component detection unit as the error component, and Is output to the addition unit via the delay unit. However, the present invention is not limited to this, and when there is a detection signal of the screen switching detection unit, there is no relation to the error component detected by the error component detection unit. What is necessary is just to output a certain constant value (for example, “1” or “2”) to the addition unit via the delay unit.
[0032]
In the above-described embodiment, a screen switching detection unit for detecting a screen switching signal for switching each of a plurality of pseudo halftone screens is provided. The constant value irrelevant to the error component is output to the addition unit via the delay unit. However, the present invention is not limited to this. A signal corresponding to the boundary between each of the plurality of pseudo halftone screens And a constant value irrelevant to the error component detected by the error component detection unit when the detection signal of the screen boundary detection unit is present is output to the addition unit via the delay unit. Just fine.
[0033]
FIG. 6 shows a second embodiment of the present invention, in which the same parts as those in FIG.
In FIG. 6, reference numeral 10a denotes a synthesizing circuit for synthesizing video signals a, b, c, and d for screens A, B, C, and D, and performs pseudo halftone processing on the output side of the synthesizing circuit 10a. A through circuit 32 that passes through the circuit as it is, a halftone display circuit 34 that performs pseudo halftone processing by the systematic dither method, and an error diffusion circuit 40a that performs pseudo halftone processing by the error diffusion method are coupled. The output side of the circuits 32, 34, and 40a is connected to a PDP (not shown) as a multi-screen display device via a selection circuit 36 controlled by a process selection signal. The selection circuit 36 performs a circuit for each of the input video signals a, b, c, and d based on the supplied 2-bit processing selection signals “10”, “11”, “01”, and “00”. It is configured to select the use of 40a, 40a, 34, 32.
[0034]
The error diffusion circuit 40a is configured as follows. Reference numeral 12 denotes an input terminal. A vertical adder 16 and a horizontal adder 18 are sequentially connected to the input terminal 12, and an output terminal 20 is connected to an output side of the horizontal adder 18. , And an error component detection unit 22. An error component control unit 42 is coupled to an output side of the error component detection unit 22. An m-line delay unit 24 and a first coefficient unit 26 are sequentially coupled to an output side of the error component control unit 42. The n-dot delay unit 28 and the second coefficient unit 30 are sequentially connected, and the output side of the first and second coefficient units 26 and 28 is connected to the vertical addition unit 16 and the horizontal addition unit 18.
[0035]
Reference numeral 46 denotes a process selection detection unit that detects switching of the process selection signal. The detection signal detected by the process selection detection unit 46 is supplied to the error component control unit 42 as a control signal. When there is a detection signal from the process selection detection unit 46, the error component control unit 42 sets a constant value (for example, “0”, “1”, or “2”) irrelevant to the error component detected by the error component detection unit 22. )), And outputs the error component detected by the error component detection unit 22 when there is no detection signal from the process selection detection unit 46.
[0036]
Next, the operation of the embodiment of FIG. 6 will be described with reference to FIG.
The video signals a, b, c, and d for the screens A, B, C, and D are combined by the combining circuit 10a, and the combined signal is input to the error diffusion circuit 40a via the input terminal 12. The error diffusion circuit 40a incorporates an error component that has occurred in the past into the composite signal input to the input terminal 12 and outputs a video signal from the output terminal 20 by the vertical direction addition unit 16 and the horizontal direction addition unit 18. The signal passes through a bit conversion circuit (a circuit for reducing the number of bits, not shown) and is output to a PDP via a selection circuit 36. The selection circuit 36 generates a circuit 40a for each of the input video signals a, b, c, and d based on the supplied 2-bit processing selection signals "10", "11", "01", and "00". , 40a, 34, 32. For this reason, the PDP includes a screen A (for example, a moving image subjected to error diffusion processing), a screen B (for example, a still image subjected to error diffusion processing), and a screen C (organized dither processing screen) in one screen as shown in FIG. , Screen D (through screen).
[0037]
The error component detection unit 22 detects an error component from the diffused output signal obtained on the output side of the horizontal direction addition unit 18 and outputs the error component to the error component control unit 42.
The process selection detection unit 46 detects switching between the process selection signals “10” and “11”, and outputs this detection signal to the error component control unit 42 as a control signal.
Therefore, when there is a detection signal from the process selection detection unit 46, the error component control unit 42 outputs “0” irrelevant to the error component output from the error component detection unit 22 as an error component, and there is no detection signal. Sometimes, the error component output from the error component detection unit 22 is output as it is.
[0038]
The error component output from the error component control unit 42 is delayed by m lines by the m-line delay unit 24, multiplied by the coefficient K1 (for example, １ ／) by the first coefficient unit 26, and input to the vertical direction addition unit 16. An n-dot delay unit 28 delays the signal by n dots, a second coefficient unit 30 multiplies the coefficient by K2 (for example, １ ／), and inputs the result to the horizontal adder 18, where an error component generated in the past is incorporated.
[0039]
As described above, when the process selection detection unit 46 detects the switching between the process selection signals “10” and “11”, the error component control unit 42 sets “0” irrespective of the error component output from the error component detection unit 22 to “0”. Since the error component is output (feedback) to the adders 16 and 18 via the delay units 24 and 28 and the first and second coefficient units 26 and 30, as shown in FIG. In the region (e), the error component becomes “0”, and the error component due to the error diffusion processing of the screens A and B can be prevented from propagating to the other screens B and A.
[0040]
In the above embodiment, a through circuit that passes through without performing pseudo halftone processing, a halftone display circuit that performs pseudo halftone processing by the systematic dither method, and an error diffusion circuit that performs pseudo halftone processing by the error diffusion method Are connected to the input side of the selection circuit, and one through screen, three pseudo halftone screens (one pseudo halftone screen by one systematic dither method and two error diffusions) are output from the output side of the selection circuit. A multi-screen display device for obtaining a video signal for displaying a pseudo-halftone screen according to the method has been described. However, the present invention is not limited to this. A plurality of halftone display circuits for processing (including an error diffusion circuit) are coupled to an input side of the selection circuit, and a plurality of halftone screens including at least two pseudo halftone screens by the error diffusion method are output from the output side of the selection circuit. It can be utilized for multiple screen display device to obtain an image signal for displaying a halftone screen.
[0041]
In the above embodiment, the error component control unit, when there is a detection signal of the process selection detection unit, sets “0” irrelevant to the value of the error component detected by the error component detection unit as the error component, Is output to the addition unit via the delay unit. However, the present invention is not limited to this. When there is a detection signal of the processing selection detection unit, there is no relation to the error component detected by the error component detection unit. What is necessary is just to output a certain constant value (for example, “1” or “2”) to the addition unit via the delay unit.
[0042]
In the above-described embodiment, the addition unit is added to the vertical addition unit and the horizontal addition unit in order to further reduce the grayscale error between the input video signal and the emission luminance by weighting and adding the multilevel error of the peripheral pixels to the output target pixel. The delay unit is configured by an m-line delay unit and an n-dot delay unit, but the present invention is not limited to this.
For example, the addition unit may be configured as one of a vertical addition unit and a horizontal addition unit, and the delay unit may be configured as one of a corresponding m-line delay unit and an n-dot delay unit. In this case, the first and second coefficient units can be omitted.
Alternatively, the addition unit may be configured by an oblique addition unit, a vertical addition unit, and a horizontal addition unit, and the delay unit may be configured by a p-line / q-dot delay unit, an m-line delay unit, and an n-dot delay unit. In this case, corresponding first, second, and third coefficient units are required as coefficient units.
[0043]
In the above-described embodiment, the case where the display device is a PDP has been described. However, the present invention is not limited to this, and can be used for a digital display panel (for example, a liquid crystal display panel).
[0044]
【The invention's effect】
According to a first aspect of the present invention, there is provided an error diffusion circuit for displaying a pseudo halftone screen by a plurality of error diffusion processes on a display device, wherein a diffusion output signal is generated by incorporating an error component generated in the past into an input video signal for a plurality of screens. An adding unit, an error component detecting unit that detects an error component from the diffused output signal,A screen switching detection unit that detects a screen switching signal for switching each screen of the plurality of pseudo halftone screens,thisScreen switching detectorofScreen switching signalWhen there is, a constant value (for example, “0”) irrelevant to the error component detected by the error component detection unit is output,Screen switching signalWhen there is no error component, an error component control unit that outputs an error component detected by the error component detection unit, and a delay unit that delays an output signal of the error component control unit and outputs the signal to the addition unit as an error component generated in the past. It is characterized by becoming.
[0045]
For this reason, when a plurality of pseudo halftone screens are displayed by error diffusion processing by outputting a diffusion output signal to a display device (for example, a PDP), the error component incorporated in the input video signal is a constant value at the boundary between the screens. (For example, “0”), and the influence of the error component generated in the error diffusion processing of a certain screen does not propagate to another screen. In an area other than the boundary between screens, an error component incorporated in the input video signal becomes an error component detected by the error component detection unit, and error diffusion processing is performed.
Therefore, each of the plurality of screens displayed by the multi-screen display device can perform pseudo halftone display by the error diffusion method without being affected by the error components of each other, and the image quality can be improved.
Furthermore, the screen switching signal detected by the screen switching detection unit can be easily extracted from, for example, a combining circuit that combines input video signals of a plurality of types (for example, a plurality of channels) to create an input video signal for a plurality of screens. Therefore, the point where the screen switching is performed can be easily detected.
[0047]
Claim2In the invention relating to the error diffusion circuit, a plurality of halftone display circuits are connected to the input side of the selection circuit, and which of the plurality of halftone display circuits is used for each of the input video signals for a plurality of screens is selected. In a multi-screen display device configured to obtain a video signal for displaying a plurality of pseudo halftone screens from an output side of the selection circuit by supplying a processing selection signal to the selection circuit, the plurality of halftone display circuits may have an error. A processing selection signal for selecting the use of the error diffusion circuit for two or more input video signals of the input video signals, wherein the error diffusion circuit includes an adder, Unit, a process selection detecting unit that detects switching of a process selection signal for selecting use of an error diffusion circuit, and a constant value irrelevant to an error component of the error component detecting unit when there is a detection output of the process selection detecting unit. An error component control unit that outputs an error component of the error component detection unit when there is no detection output, and a delay unit that delays an output signal of the error component control unit and outputs the delayed signal to an addition unit. It is characterized.
[0048]
For this reason, when the multiple screen display device (for example, PDP) displays a plurality of pseudo halftone display screens including two or more error diffusion processing screens, the input image is displayed at the boundary between the screens in the two or more error diffusion processing screens. The error component included in the signal has a constant value (for example, “0”), and the influence of the error component generated in the error diffusion processing of one screen does not propagate to another screen. In an area other than the boundary between screens, an error component incorporated in the input video signal becomes an error component detected by the error component detection unit, and error diffusion processing is performed.
Therefore, each of the two or more error diffusion processing screens displayed on the multi-screen display device can perform pseudo halftone display by the error diffusion method without being influenced by mutual error components, thereby improving image quality. .
[0049]
Claim3The invention according to claim1 or 2In the invention, the addition unit comprises a vertical addition unit and a horizontal addition unit, and the delay unit delays the output signal of the error component control unit by m (m is a positive integer) lines, An n-dot delay unit for delaying the output signal of the component control unit by n (n is a positive integer) dots, multiplying the output of the m-line delay unit by a coefficient K1 (a constant of 1 or less) to the vertical adder A first coefficient unit for outputting the data, and a second coefficient unit for multiplying the output of the n-dot delay unit by a coefficient K2 (K1 + K2 = 1) and outputting the result to the horizontal addition unit. The multi-level error of the pixel is weighted and added, so that the density error between the input video signal and the light emission luminance can be further reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of an error diffusion circuit of a multi-screen display device according to the present invention.
FIG. 2 is a waveform diagram of a screen switching signal and a screen switching detection signal in FIG.
FIG. 3 is an explanatory diagram of a display example when a plurality of screens are displayed on a display device coupled to an output side of the circuit of FIG. 1;
FIG. 4 is a block diagram showing a modification of FIG. 1;
FIG. 5 is an explanatory diagram of a display example when a plurality of screens are displayed on a display device coupled to an output side of the circuit of FIG. 4;
FIG. 6 is a block diagram showing a second embodiment of the error diffusion circuit of the multi-screen display device according to the present invention.
7 is an explanatory diagram of a display example when a plurality of screens are displayed on a display device coupled to the output side of the circuit in FIG. 6;
FIG. 8 is a block diagram showing a conventional example.
9 is an explanatory diagram of a display example when a plurality of screens are displayed on a display device coupled to the output side of the circuit in FIG. 8;
FIG. 10 is a block diagram showing another conventional example.
11 is an explanatory diagram of a display example when a plurality of screens are displayed on a display device coupled to the output side of the circuit in FIG.
[Explanation of symbols]
10, 10a, 10b: synthesis circuit, 12: input terminal, 14, 14a, 40, 40a: error diffusion circuit, 16: vertical direction adder, 18: horizontal direction adder, 20: output terminal, 22: error component detection 24, m-line delay unit, 26, first coefficient unit, 28, n-dot delay unit, 30, second coefficient unit, 32, through circuit, 34, halftone display circuit (pseudo halftone by systematic dither method) 36: selection circuit, 42: error component control unit, 44: screen switching detection unit, 46: processing selection detection unit, a, b, c, d: input video signal, A, B, C, D: display screen, (a), (b), (c), (d), (e): border area of the display screen.

Claims (3)

An error diffusion circuit for performing an error diffusion process on an input video signal for a plurality of screens, and displaying a plurality of pseudo halftone screens on a display device, to obtain a diffusion output signal by incorporating an error component generated in the past into the input video signal. An addition unit, an error component detection unit that detects an error component from the diffused output signal obtained by the addition unit, and a screen switching detection unit that detects a screen switching signal for switching each of a plurality of pseudo halftone screens. this screen switching換検 when the output unit screen switching signal is present the output unrelated constant value to the error component detected by said error component detecting unit, when there is no screen switching signal outputs the error component detected by said error component detecting unit And a delay unit that delays an output signal of the error component control unit and outputs the delayed signal to the addition unit as an error component generated in the past. Error diffusion circuit of the plurality screen display device. A plurality of halftone display circuits that perform pseudo halftone processing on input video signals for a plurality of screens are provided, and a selection circuit is coupled to an output side of the plurality of halftone display circuits, and the plurality of halftone display circuits are provided for each of the input video signals. By supplying a processing selection signal for selecting which of the halftone display circuits to use to the selection circuit, an image signal for displaying a plurality of pseudo halftone screens is obtained from the output side of the selection circuit. In the multi-screen display device described above, the plurality of halftone display circuits include an error diffusion circuit, and the processing selection signal is a processing for selecting use of the error diffusion circuit for two or more input video signals of the input video signals. The error diffusion circuit includes a selection signal, the error diffusion circuit includes an error component generated in the past in the input video signal to obtain a diffused output signal, and an error diffusion circuit based on the diffused output signal obtained by the adder. An error component detector for detecting a component; a process selection detector for detecting switching of a process selection signal for selecting the use of the error diffusion circuit; and an error of the error component detector when there is a detection output from the process selection detector. An error component control unit that outputs a constant value irrelevant to the component and outputs an error component of the error component detection unit when there is no detection output; and an output signal of the error component control unit is delayed and output to the addition unit An error diffusion circuit for a multi-screen display device, comprising: a delay unit. The adder includes a vertical adder and a horizontal adder. The delay unit includes an m-line delay unit that delays the output signal of the error component control unit by m (m is a positive integer) lines, and the error component control unit. And an n-dot delay unit for delaying the output signal of n by n (n is a positive integer) dots. The output of the m-line delay unit is multiplied by a coefficient K1 (a constant of 1 or less) and output to the vertical addition unit. to a first coefficient unit, the n factor to the output of the dot delay unit K2 (K1 + K2 = 1) a multiply by the horizontal output direction adding unit formed by and a second coefficient unit according to claim 1 or 2, wherein Error diffusion circuit for multiple screen display devices.

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