JP2007114306A - Television receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device equipped with a PDP (Plasma Display Panel) module capable of preventing a phenomenon of a regular pattern light emission inside a window shape image by influence of error diffusion processing and dither processing performed in an image signal processing section in the PDP module, when a low to intermediate gradation image of the window shape is displayed with dark background. <P>SOLUTION: The image display device equipped with the PDP module having a function for performing image signal processing in order to reinforce gradation expression of a low gradation section, and a reverse gamma correction means for performing reverse gamma correction on an image input signal, is provided with a means for controlling a reverse gamma correction characteristic of the reversed gamma correction means according to a signal state of the image input signal to the image display device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a video display device provided with a PDPModule (PDP module).

  A PDP (Plasma Display Panel) module includes a PDP panel, a PDP panel drive circuit, and a video signal output processing unit. In the PDP module, the sustain discharge phenomenon is induced between the X electrode and the Y electrode provided in each cell in the PDP panel, and the ultraviolet rays generated by the discharge are applied to the ribs in each cell. Sustained light emission is performed by exciting the phosphor. The brightness of the screen as a video expression is determined by the number of sustain discharges. The driving circuit of the PDP panel applies a driving voltage between XY electrodes provided in each cell in the PDP panel. The video signal output processing unit controls the sustain discharge between the XY electrodes in each cell.

  In a PDP module using the subfield driving method, one field period is usually composed of about ten subfields (SF). An image is expressed by superimposing SFs having different brightnesses. When one field is composed of eight subfields, the brightness of the first to eighth subfields is set as follows, for example.

Brightness of first SF = 2 ⁰ Brightness = Brightness level “1”
2nd SF brightness = 2 ¹ brightness = brightness level "2"
Brightness = 2 ² brightness = brightness level of the 3SF "4"
4th SF brightness = 2 ³ brightness = brightness level “8”
Brightness of the 5SF = 2 ⁴ brightness = brightness level "16"
Brightness of 6th SF = 2 ⁵ brightness = brightness level “32”
7th SF brightness = 2 ⁶ brightness = brightness level “64”
8th SF brightness = 2 ⁷ brightness = brightness level “128”

  When the first SF to the eighth SF are continuously emitted during one field period, the brightness of the one field period is “225”. By emitting light by arbitrarily combining eight types of SF in one field period, it is possible to express gradations of “0” to “225”.

  In a video signal processing unit in a PDP module, error diffusion processing and dither processing are generally performed to supplement the number of gradations that can be expressed by the number of sustain discharges. As a result, the number of gradation representations of the PDP module is the number of gradation representations based on the difference in the number of sustain discharges in a pure cell, and the gradations additionally represented by error diffusion processing and dither processing performed in the video signal output processing unit. The number of gradations is the sum of the number of expressions.

  When the video input signal to the video signal processing unit in the PDP module is 10 bits (1023 gradations), for example, 700 gradations, which is the gradation expression number due to the difference in the number of sustain discharges in a pure cell, and the video signal A total of 1023 gradations is expressed by adding up to 323 gradations, which is the number of gradation representations additionally expressed by error diffusion processing and dither processing performed in the output processing unit.

  In the PDP module, it is technically difficult to express the gradation of the low gradation part (in the case of a maximum of 255 gradations, around 0 to 150 gradations) only by the difference in the number of sustain discharges. By adding error diffusion processing and dither processing to the low gradation portion, the final number of gradation representations is secured.

  By the way, the detailed contents (algorithms) of error diffusion processing and dither processing performed in the video signal processing unit in the PDP module are technologies specific to the manufacturer of each PDP module, and in most cases, development of video display equipment or Information is not disclosed to the manufacturer.

  Video display device development and manufacturers receive the PDP module supply from the PDP module manufacturer, complete the video display device by designing and developing the various circuits in the video display device and the entire casing. Yes. In the video display device thus completed, the window-like video interior has a regular pattern under certain video display conditions due to error diffusion processing and dither processing performed in the video signal processing unit in the PDP module. It was found that the phenomenon of light emission appears.

A certain video condition is a situation in which a background image is black and a window-like image of low gradation to intermediate gradation is displayed. Specifically, a case where a channel banner display video is displayed when there is no signal in digital broadcasting, and a case where a video menu is displayed when there is no signal of AV input (or PC input) are applicable.
JP-A-6-54173

  In the present invention, when a window-like image having a black background and a low gradation to an intermediate gradation is displayed, the window is affected by an error diffusion process and a dither process performed in the video signal processing unit in the PDP module. An object of the present invention is to provide a video display device including a PDP module that can avoid the phenomenon that the inside of a video image emits light in a regular pattern.

  According to the first aspect of the present invention, there is provided a PDP module having a function of performing video signal processing for reinforcing gradation expression of a low gradation part, and an inverse γ obtained by performing inverse γ correction on a video input signal. The video display device including the correction unit includes a unit that controls the reverse γ correction characteristic of the reverse γ correction unit according to the signal state of the video input signal to the video display device.

  According to the second aspect of the present invention, there is provided a PDP module having a function of performing video signal processing for reinforcing gradation expression in a low gradation part, and an inverse γ for performing inverse γ correction on a video input signal. Means for determining whether the signal state of the video input signal to the video display device is a signal present state or no signal state, and a signal of the video input signal to the video display device. When the state is a signal present state, the means for setting the reverse γ correction characteristic of the reverse γ correction means to the normal first reverse γ correction characteristic, and the signal state of the video input signal to the video display device is no signal. In this state, there is provided means for setting the reverse γ correction characteristic of the reverse γ correction means to the second reverse γ correction characteristic so that the pattern display caused by the video signal processing in the PDP module does not occur. It is characterized by.

  The invention according to claim 3 is the invention according to claim 2, wherein the second inverse γ correction characteristic is such that the low gradation part of the input video signal is forced to zero. And

  According to a fourth aspect of the present invention, there is provided a video display device including a PDP module having a function of performing video signal processing for reinforcing gradation expression of a low gradation portion and a function of turning on and off the function. Means for discriminating whether the signal state of the video input signal to the video signal is a signal present state or no signal state, and when the signal state of the video input signal to the video display device is a signal present state, in the PDP module When the signal state of the video input signal to the video display device and the means for controlling the PDP module so that the video signal processing to reinforce the gradation expression of the low gradation part is performed The PDP module has means for controlling the PDP module so that the video signal processing for reinforcing the gradation expression of the low gradation portion is not performed. And butterflies.

  According to the present invention, when a window-like image having a black background and a low gradation to an intermediate gradation is displayed, due to the influence of error diffusion processing and dither processing performed in the video signal processing unit in the PDP module. Thus, it is possible to avoid the phenomenon that the inside of the window-like image emits light in a regular pattern.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows the configuration of a video display device.

  The video display device 100 includes an analog tuner 1 for receiving an analog TV broadcast and a digital tuner 2 for receiving a digital TV broadcast (BS digital broadcast, CS digital broadcast, terrestrial digital broadcast). AV input terminal for inputting video source from DVD player, VHS VTR, game, digital movie, PC input terminal for inputting video source from personal computer, SD input terminal for inputting video source from digital camera Etc.

  Video signals obtained from the analog tuner 1, the digital tuner 2, and various video input terminals are sent to the input signal switching circuit 3. The designation of the video source is performed by the user operating the remote control transmitter 6. A remote control signal from the remote control transmitter 6 is sent to the microcomputer 10 via the remote control light receiving circuit 7. The microcomputer 10 controls the input signal switching circuit 3 so as to select the video source designated by the user.

  The video signal selected by the input signal switching circuit 3 is sent to the video signal processing circuit 4. The video signal processing circuit 4 includes an inverse γ correction circuit 4a. The video signal processing circuit 4 performs scanning conversion processing (scaling processing), inverse γ correction processing, and the like according to the input video signal, converts the video signal into an LVDS signal, and sends the signal to the PDP module 20.

  The PDP module 20 includes a logic board (video signal output processing unit) 21, a PDP panel drive circuit 22, and a PDP panel 23. The Logic Board 21 includes an inverse γ correction circuit 21a. The Logic Board 21 performs reverse γ correction processing, error diffusion processing, dither processing, and the like on the LVDS signal sent from the video signal processing circuit 4 to generate a drive signal for driving the PDP panel drive circuit 22. Then, it is given to the PDP panel drive circuit 22.

  The PDP panel drive circuit 22 includes a display electrode (X electrode), a display electrode (Y electrode), and a DATA electrode (address electrode) provided in the glass substrate of the PDP panel 23 according to a drive signal supplied from the Logic Board 21. In addition, a drive voltage (discharge voltage) is supplied. In the PDP panel 23, a drive voltage (discharge voltage) is applied to the display electrode (X electrode), the display electrode (Y electrode), and the DATA electrode (address electrode) provided in the glass substrate, so that each cell Sustain discharge occurs in the inside, and the ultraviolet rays generated by the sustain discharge excite the phosphor (R / G / B) applied to each cell to emit light. As a result, a video corresponding to the input video signal is displayed.

  Each unit in the video display device 100 is controlled by the microcomputer 10. The power supply of each unit in the video display device 100 is generated by the power supply circuit 5. An AC power supply 8 is supplied to the power supply circuit 5.

  The overall inverse γ correction characteristics of the video display device are the inverse γ correction characteristics of the inverse γ correction circuit 4 a in the video signal processing circuit 4 and the inverse γ correction of the inverse γ correction circuit 21 a in the Logic Board 21 of the PDP module 20. Determined by the characteristics. In this embodiment, the inverse γ correction characteristic of the inverse γ correction circuit 21 a in the Logic Board 21 of the PDP module 20 is fixed, and the inverse γ correction characteristic of the inverse γ correction circuit 4 a in the video signal processing circuit 4 is changed. Thus, the overall inverse γ correction characteristic of the video display device is changed.

  As described above, when a channel banner display video is displayed when there is no signal in digital broadcasting or when a video menu is displayed when there is no signal during AV input (or PC input), the channel banner display video area or video menu is displayed. There is a problem that a phenomenon occurs in which the display area emits light in a regular pattern.

  In this embodiment, in order to solve this problem, the applicant of the present invention uses the inverse γ correction circuit 4a in the video signal processing circuit 4 when there is no signal for digital broadcasting and no signal for AV input (or PC input). By changing the inverse γ correction characteristic, the overall inverse γ correction characteristic of the video display device is changed to a characteristic different from the normal characteristic.

  As the overall inverse γ correction characteristic of the video display device, normally, the first inverse γ correction characteristic (Ganma 2.2) indicated by the curve S1 in FIG. 2 is set. At the time of no signal of digital broadcasting and no signal of AV input (or PC input), in the banner display part at the time of no signal of digital broadcasting or the video menu display part at the time of no signal of AV input (or PC input), The characteristic can be changed so that the pattern display does not occur. In this embodiment, when there is no signal for digital broadcasting and no signal for AV input (or PC input), the overall inverse γ correction characteristic of the video display device is the second inverse γ correction indicated by a curve S2 in FIG. It can be changed to the characteristic (Ganma2.6).

  The microcomputer 10 determines whether or not the digital broadcast is in a no-signal state based on the monitoring result of the digital tuner 2. That is, when digital broadcast is selected as the video source to be viewed, the digital tuner 2 monitors whether there is a digital broadcast video for the currently selected service, and the data broadcast is being broadcast. Whether or not it exists is monitored, and the monitoring result is output to the microcomputer 10. The microcomputer 10 determines that the digital broadcast is in a no-signal state when there is no digital broadcast video and the data broadcast is not being broadcast, and otherwise determines that the digital broadcast is in a reception state.

  Whether the AV input (or PC input) is in the no-signal state is determined by the microcomputer 10 based on the monitoring result of the input signal switching circuit 3. That is, when AV input (or PC input) is selected as the video source to be viewed, the input signal switching circuit 3 corresponds to the video source for which the period of the synchronizing signal of AV input (or PC input) is selected. Whether or not it coincides with the cycle, and outputs the monitoring result to the microcomputer 10. The microcomputer 10 determines that the AV input (or PC input) is in the no-signal state (asynchronous) when the period of the synchronizing signal does not match the period according to the selected video source, and the period of the synchronizing signal is selected. If the period corresponds to the video source, the AV input (or PC input) is determined to be in a signal present state (synchronized).

  FIG. 3 shows the relationship between the signal state and the inverse gamma correction characteristic set according to the signal state for each of digital broadcasting, AV input (or PC input), digital camera playback, and analog broadcasting.

  When digital broadcasting is selected as the video source to be viewed and the signal state is “reception state”, the first inverse γ correction characteristic is set as the overall inverse γ correction characteristic of the video display device. When the signal state is “no signal state”, the second inverse γ correction characteristic is set as the overall inverse γ correction characteristic of the video display device.

  When AV input (or PC input) is selected as the video source to be viewed, if the signal state is “synchronized”, that is, a signal is present, the overall inverse γ correction characteristic of the video display device is When the reverse γ correction characteristic of 1 is set and the signal state is “asynchronous”, that is, no signal state, the second reverse γ correction characteristic is set as the overall reverse γ correction characteristic of the video display device.

  When digital camera playback or analog broadcasting is selected as the video source to be viewed, the entire background does not become black even in the no-signal state, so the first inverse gamma correction characteristic is set regardless of the signal state. .

  FIG. 4 shows an inverse γ correction characteristic control processing procedure by the microcomputer 10.

  First, the currently selected video source to be viewed is determined (step S1). Specifically, the currently selected video source to be viewed is any one of (a) digital broadcasting, (b) AV input (or PC input), (c) digital camera playback, and (d) analog broadcasting. Is determined.

  If the currently selected video source to be viewed is digital broadcasting (step S2), the currently selected channel is selected based on the monitoring results of the digital tuner 2 (the presence / absence of digital broadcasting video and the presence / absence of data broadcasting). It is determined whether the digital broadcast of the service being received is in a reception state or no signal state (step S3).

  When it is determined that the digital broadcast of the currently selected service is in a receiving state, after setting the first inverse γ correction characteristic as the overall inverse γ correction characteristic of the video display device (step S4), Return to step S1.

  In step S3, when it is determined that the digital broadcast of the currently selected service is in a no-signal state, the second inverse γ correction characteristic is set as the overall inverse γ correction characteristic of the video display device. After (step S5), the process returns to step S1. In this embodiment, the overall reverse γ correction characteristic of the video display device is changed by changing the reverse γ correction characteristic of the reverse γ correction circuit 4 a in the video signal processing circuit 4.

  If it is determined in step S1 that the currently selected video source to be viewed is AV input (or PC input) (step S6), the monitoring result (AV input (or PC input) of the input signal switching circuit 3 is determined. (The monitoring result of whether or not the period of the synchronization signal of the input) matches the period according to the selected video source), the currently selected AV input (or PC input) is in the presence of signal (synchronization) Or whether there is no signal (asynchronous) (step S7).

  When it is determined that the currently selected AV input (or PC input) is in the presence of a signal (synchronization), the first reverse γ correction characteristic is set as the overall reverse γ correction characteristic of the video display device. After (step S8), the process returns to step S1.

  If it is determined in step S7 that the currently selected AV input (or PC input) is in the no-signal state (asynchronous), the second inverse γ is used as the overall inverse γ correction characteristic of the video display device. After setting the correction characteristics (step S9), the process returns to step S1.

  If it is determined in step S1 that the currently selected video source to be viewed is digital camera playback (step S10), the first inverse γ correction characteristic as the overall inverse γ correction characteristic of the video display device. Is set (step S11), the process returns to step S1.

  If it is determined in step S1 that the currently selected video source to be viewed is analog broadcasting (step S12), the first inverse γ correction characteristic is used as the overall inverse γ correction characteristic of the video display device. (Step S13), the process returns to step S1.

  In the above embodiment, the second inverse γ correction characteristic (Ganma2.6) shown by the curve S2 in FIG. 2 is used as the second inverse γ correction characteristic. In FIG. 5, the inverse γ correction characteristic indicated by the curve S3 may be used. When the inverse γ correction characteristic indicated by the curve S3 in FIG. 5 is used, the input signal of the low gradation part is forcibly set to 0 (black). If the input signal of the low gradation part is forced to 0 (black) in this way, the effect of error diffusion processing and dither processing performed to reinforce the gradation expression of the low gradation part is lost. Patterns resulting from error diffusion processing and dither processing do not appear.

  Further, as the second reverse γ correction characteristic, the reverse γ correction characteristic indicated by the curve S4 in FIG. 6 may be used. When the inverse γ correction characteristic indicated by the curve S4 in FIG. 6 is used, the output gradation of the low gradation portion corresponding to black of the input signal (in this example, the low gradation portion of 5 gradations or less) is This is higher than when the first inverse γ correction characteristic is used. Therefore, when the background of the screen is black, the brightness of the black background increases, so that error diffusion processing and dither processing are performed on the entire screen, and patterns resulting from error diffusion processing and dither processing do not appear. .

  In the above embodiment, the overall reverse γ correction characteristic of the video display device is changed by changing the reverse γ correction characteristic of the reverse γ correction circuit 4 a in the video signal processing circuit 4. The overall inverse γ correction characteristic of the video display device may be changed by changing the inverse γ correction characteristic of the inverse γ correction circuit 21 a in the image 21, or the inverse γ correction circuit in the image signal processing circuit 4. The overall inverse γ correction characteristics of the video display device may be changed by changing the inverse γ correction characteristics of both 4a and the inverse γ correction circuit 21a in the Logic Board 21.

  When the PDP module has a function that can turn on / off error diffusion processing and dither processing performed by a logic board (video signal output processing unit) in the PDP module, and when there is no digital broadcast signal and AV When there is no input (or PC input) signal, error diffusion processing and dither processing performed by the Logic Board (video signal output processing unit) in the PDP module may be turned off. In this case, it is not necessary to control the inverse γ correction characteristic.

It is a block diagram which shows the structure of a video display apparatus. Reverse γ correction characteristic (first reverse γ correction characteristic) used at normal time, and reverse γ correction characteristic (second reverse γ correction characteristic) used when there is no signal of digital broadcasting and when there is no signal of AV input (or PC input) It is a graph which shows an example with a characteristic. It is a table | surface which shows the relationship between a signal state and the reverse gamma correction characteristic set according to the signal state for every digital broadcasting, AV input (or PC input), digital camera reproduction | regeneration, and analog broadcasting. 4 is a flowchart showing a reverse γ correction characteristic control processing procedure by the microcomputer 10. It is a graph which shows the other example of the reverse (gamma) correction characteristic (2nd reverse (gamma) correction characteristic) used at the time of no signal of digital broadcasting and AV input (or PC input). It is a graph which shows the further another example of the reverse (gamma) correction characteristic (2nd reverse (gamma) correction characteristic) used at the time of no signal of digital broadcasting and AV input (or PC input).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Analog tuner 2 Digital tuner 3 Input signal switching circuit 4 Video signal processing circuit 4a Reverse gamma correction circuit 10 Microcomputer 20 PDP module 21 Logic Board (Video signal output processing part)
21a Inverse γ correction circuit 22 PDP panel drive circuit 23 PDP panel 100 Video display device

Claims (4)

Video display device comprising a PDP module having a function of performing video signal processing to reinforce gradation expression of a low gradation part, and reverse γ correction means for performing reverse γ correction on a video input signal In
An image display device comprising means for controlling the inverse γ correction characteristic of the inverse γ correction means in accordance with a signal state of a video input signal to the image display device. Video display device comprising a PDP module having a function of performing video signal processing to reinforce gradation expression of a low gradation part, and reverse γ correction means for performing reverse γ correction on a video input signal In
Means for determining whether the signal state of the video input signal to the video display device is a signal present state or a no signal state;
When the signal state of the video input signal to the video display device is a signal present state, the reverse γ correction characteristic of the reverse γ correction means is set to the normal first reverse γ correction characteristic, and the video display device When the signal state of the video input signal is a no-signal state, the reverse γ correction characteristic of the reverse γ correction means is set to the second so that the pattern display resulting from the video signal processing in the PDP module does not occur. Means for setting reverse γ correction characteristics;
A video display device characterized by comprising: The video display device according to claim 2, wherein the second inverse γ correction characteristic is a characteristic that forcibly sets a low gradation part of an input video signal to zero. In a video display device including a PDP module having a function of performing video signal processing for reinforcing gradation expression of a low gradation part and a function of turning on and off the function,
Means for determining whether the signal state of the video input signal to the video display device is a signal present state or a no signal state;
When the signal state of the video input signal to the video display device is a signal present state, the PDP module is controlled so that the video signal processing for reinforcing the gradation expression of the low gradation portion is performed in the PDP module. And when the signal state of the video input signal to the video display device is a no-signal state, the PDP module does not perform video signal processing to reinforce the gradation expression of the low gradation part. , Means for controlling the PDP module,
A video display device characterized by comprising:

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