JP2009122506A - Driving method of display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method of a display panel capable of displaying an image of high quality following human visual characteristics. <P>SOLUTION: A viewing distance between the display panel for displaying an image corresponding to an input video signal, and a viewer, is measured, and a brightness level of each pixel based on the input video signal is adjusted in accordance with the viewing distance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display panel driving method for displaying an image corresponding to an input video signal.

  2. Description of the Related Art Currently, a display device equipped with a plasma display panel (hereinafter referred to as PDP) or an electroluminescent display panel (hereinafter referred to as ELDP) is known as a thin flat display panel. In these PDPs and ELDPs, the light-emitting element responsible for each pixel has only two states, “ON” and “OFF”. Therefore, in order to obtain halftone luminance corresponding to the input video signal, the display panel such as PDP and ELDP is driven by gradation using the subfield method.

  In the subfield method, one field display period in an input video signal is divided into a plurality of subfields each assigned a light emission count corresponding to a luminance weight. Here, each pixel of the display panel is set to one of the “lighting” and “lighting off” states for each subfield according to the input video signal, and the pixels in the “lighting” state for each subfield. Is emitted for the number of times of light emission assigned to the subfield. According to this driving method, halftone luminance corresponding to the input video signal is expressed by the total number of times of light emission executed in each subfield within one field display period.

  Furthermore, in recent years, luminance frequency data indicating the frequency for each luminance is generated for each screen based on the input video signal, and all luminance areas are targeted based on the luminance frequency data, and subfields are generated according to the frequency. There has been proposed a driving method that adjusts the number of (see, for example, Patent Document 1). With such a driving method, if the number of subfields to be assigned to the luminance division region is increased as the luminance division region including the luminance having a higher frequency, a favorable gradation expression that follows the brightness of the image based on the input video signal ( Smooth brightness change).

However, even when such a driving method is used to display an image, a high quality image may not be visually recognized.
JP 2004-240103 A

  An object of the present invention is to provide a display panel driving method capable of providing a visually high-quality display image.

  The display panel driving method according to claim 1 is a display panel driving method for performing gradation display by selectively causing each pixel of the display panel to emit light in accordance with the input video signal, and the display panel driving method according to the input video signal. By generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution of the frame unit represented, and accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance level. Cumulative luminance frequency data representing the cumulative frequency for each luminance level is generated, a distance between the display panel and a viewer in front of the display panel is measured as a viewing distance, and is represented by the cumulative luminance frequency data according to the viewing distance. Corrected cumulative luminance frequency data is generated by correcting the cumulative frequency for each luminance level, and based on the corrected cumulative luminance frequency data, Adjusting the brightness level of each pixel in the fill power video signal.

  The display panel driving method according to claim 4 is a display panel driving method for performing gradation display by selectively causing each pixel of the display panel to emit light in accordance with an input video signal, wherein the input video is displayed. Generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution of the frame unit represented by the signal, and accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance level; To generate cumulative luminance frequency data representing the cumulative frequency for each luminance level, measure the distance between the display panel and the viewer in front thereof as a viewing distance, and each luminance represented by the cumulative luminance frequency data A predetermined first accumulation that is less than the maximum accumulation frequency within each of the accumulation frequencies for each level and has a value of 90% or more of the maximum accumulation frequency A luminance level corresponding to the degree is detected as a substantial peak luminance level, a correction coefficient is calculated based on the substantial peak luminance level and the viewing distance, and the pixel represented by the input video signal based on the correction coefficient Adjust the brightness level for each.

  The display panel driving method according to claim 7 is a display panel driving method for performing gradation display by selectively causing each pixel of the display panel to emit light according to an input video signal, wherein the input video is displayed. Generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution of the frame unit represented by the signal, and accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance level; To generate cumulative luminance frequency data representing the cumulative frequency for each luminance level, measure the distance between the display panel and the viewer in front thereof as a viewing distance, and each luminance represented by the cumulative luminance frequency data A predetermined first cumulative frequency having a value greater than the lowest cumulative frequency and not more than 10 percent of the maximum cumulative frequency in each of the cumulative frequencies for each level; A corresponding luminance level is detected as a substantial bottom luminance level, a correction coefficient is calculated based on the substantial bottom luminance level and the viewing distance, and each pixel represented by the input video signal is calculated based on the correction coefficient. Adjust the brightness level.

  According to a tenth aspect of the present invention, there is provided a display panel driving method for driving a display panel that performs gradation display by selectively causing each pixel arranged in each display line of the display panel to emit light according to an input video signal. A load amount during light emission by each pixel is calculated for each display line based on the input video signal, and a distance between the display panel and a viewer in front thereof is measured as a viewing distance. A correction coefficient is calculated based on the load amount and the viewing distance for each display line, and a luminance level for each pixel represented by the input video signal is adjusted based on the correction coefficient.

  A display panel driving method according to claim 12 is a display panel driving method for performing gradation display by selectively emitting each pixel of the display panel according to an input video signal, wherein the input video is displayed. Generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution of the frame unit represented by the signal, and accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance level; To generate cumulative luminance frequency data representing the cumulative frequency for each luminance level, measure the distance between the display panel and the viewer in front thereof as a viewing distance, and brightness of the space in which the display panel is installed Is detected as environmental illuminance, and is smaller than the maximum cumulative frequency among the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data. And a luminance level corresponding to a predetermined first cumulative frequency having a value of 90% or more of the maximum cumulative frequency is detected as a substantial peak luminance level, and an average luminance per image frame indicated by the input video signal Based on the display screen, the screen visual luminance that is viewed from the display screen of the display panel is obtained, and the ambient luminance and the screen visual luminance are mixed at a mixing ratio based on the viewing distance to obtain the adaptation luminance that is viewed in the viewing environment. Then, a correction coefficient is calculated based on the substantial peak luminance level and the adaptation luminance, and a luminance level for each pixel represented by the input video signal is adjusted based on the correction coefficient.

  Measure the viewing distance between the display panel that displays the image according to the input video signal and the viewer, and based on the viewing distance, a display image that is visually best under this viewing environment is provided. The luminance level for each pixel based on the input video signal is corrected. Here, in performing the luminance level correction, in the display panel driving method according to the first feature of the present invention, first, the frequency of pixels for each luminance level in the luminance distribution in frame units represented by the input video signal. Are accumulated in order of luminance level to generate accumulated luminance frequency data representing the accumulated frequency for each luminance level. Further, corrected cumulative luminance frequency data is generated by correcting the cumulative frequency for each luminance level represented by the cumulative luminance frequency data according to the viewing distance. Based on the corrected cumulative luminance frequency data, the luminance level for each pixel in the input video signal is adjusted.

  In the display panel driving method according to the second feature of the present invention, first, a predetermined value slightly smaller than the maximum accumulated frequency among the accumulated frequencies for each luminance level represented by the accumulated luminance frequency data. The luminance level corresponding to the cumulative frequency of is detected as the actual peak luminance level. Then, the luminance level for each pixel represented by the input video signal is adjusted based on the substantial peak luminance level and the viewing distance.

  In the display panel driving method according to the third aspect of the present invention, first, a predetermined value slightly larger than the lowest cumulative frequency among the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data. The luminance level corresponding to the cumulative frequency is detected as the actual bottom luminance level. Then, the luminance level for each pixel represented by the input video signal is adjusted based on the substantial bottom luminance level and the viewing distance.

  As described above, the luminance level adjustment according to the display panel driving method according to the first to third features of the present invention is applied to the input video signal so as to increase the degree of contrast enhancement as the viewing distance increases. . As a result, the longer the viewing distance, the more sensitive to the contrast, while the closer the viewing distance, the better the display that follows the human visual characteristics of being more sensitive to the luminance gradation expression ability than the contrast. Images can be provided.

  In the display panel driving method according to the fourth feature of the present invention, first, the load amount at the time of light emission by each pixel is calculated for each display line based on the input video signal. Then, the luminance level for each pixel represented by the input video signal is adjusted based on the load amount and viewing distance for each display line. Therefore, according to such brightness level adjustment, the display image looks relatively bright when the viewing distance is short, so that the screen uniformity is conspicuous. On the other hand, when the viewing distance is far, the display is felt dark. It is possible to provide a good display image that follows the characteristics.

  In the display panel driving method according to the fifth aspect of the present invention, first, the brightness of the space in which the display panel is installed is detected as the environmental illuminance together with the viewing distance as described above. Next, the screen visual brightness that is viewed from the display screen of the display panel is obtained based on the average brightness for each frame of the image indicated by the input video signal. Then, by mixing the ambient illuminance and the screen visual luminance at a mixing ratio based on the viewing distance, an adaptation luminance that is viewed in the viewing environment is obtained, and based on the adaptation luminance and the actual peak luminance level, the input video is obtained. The luminance level for each pixel represented by the signal is adjusted. According to such a brightness level adjustment, the display image is visually perceived as dark overall due to the high adaptation brightness, while the human visual characteristic that the display image feels dazzling because of the low adaptation brightness is good. A display image can be provided.

  FIG. 1 is a diagram showing a configuration of a plasma display apparatus that drives a plasma display panel as a display panel according to a driving method according to the present invention.

In FIG. 1, a PDP 10 as a plasma display panel includes a front transparent substrate and a back substrate (not shown) disposed to face each other with a discharge space in which a discharge gas is sealed. Row electrodes X _{1 to} X _n and row electrodes Y _{1 to} Y _n are formed on the front transparent substrate so as to extend in the horizontal direction (horizontal direction) of the two-dimensional screen. These row electrodes X ₁ to X _n and row electrodes Y ₁ to Y _n, respectively a pair of row electrodes X _i and Y _i: by (i 1 to n), plays a first to n-th display line in the PDP10 Yes. On the back substrate, the column electrodes D are arranged to extend in the vertical direction of the two-dimensional display screen so as to cross the row electrodes X _{1 to} X _n and the row electrodes Y _{1 to} Y _n, respectively. ₁ to D _m are formed. A discharge cell (display cell) P as a pixel is formed at the intersection of each row electrode pair (X, Y) and the column electrode D including the discharge space. That is, the PDP 10 includes (n × m) discharge cells including discharge cells P _{(1,1) in the} first row / first column to discharge cells P _{(n, m) in} the n-th row / m-th column. P is arranged in a matrix.

  The A / D converter 1 converts the input video signal VD into pixel data DD representing the luminance level of, for example, 8 bits for each pixel (discharge cell P), and supplies the pixel data DD to the luminance correction circuit 200.

The viewing distance sensor 2 is installed on the periphery of the display surface 11 of the plasma display device as shown in FIG. The viewing distance sensor 2 detects a distance (hereinafter referred to as viewing distance) between the display screen of the PDP 10 and a viewer existing in front of the display screen so as to view the image displayed on the display screen. supplying a viewing distance signal L _e indicating the distance to the luminance correction circuit 200. The viewing distance sensor 20 includes, for example, a heat ray sensor and an ultrasonic sensor. The heat ray sensor detects the amount of far-infrared rays emitted from an object (floor, wall, chair, etc.) existing in front of the display screen or the human body, and the state where the detected amount exceeds a predetermined amount continues for a certain period A human body detection signal indicating that the presence of a human body has been detected is supplied to the ultrasonic sensor only. While the human body detection signal is not supplied, the ultrasonic sensor irradiates the ultrasonic wave at least once in front of the display screen, and stores the reflected wave pattern as a non-human body reflection pattern. On the other hand, when the human body detection signal is supplied, the ultrasonic sensor emits an ultrasonic wave toward the front of the display screen, and the reflected wave that does not exist in the non-human body reflection pattern from the reflected wave pattern. Is extracted as a human body reflected wave. The ultrasonic sensor measures the time delay from the start of the irradiation of the ultrasonic wave to the human body reflection comes back it to calculate the viewing distance signal L _e indicating the viewing distance on the basis of the delay time. The viewing distance sensor 2 uses a heat ray sensor to detect a human body, but is not limited to this. In short, the human body existing in front of the PDP 10 may be detected by a sensor capable of detecting any specific radiation wave emitted from a radiation wave generation source such as a human body. As the viewing distance sensor 2, a microphone is installed at the viewing position, and the microphone collects the sound emitted from the speaker provided in the plasma display device, whereby the arrival time of the sound from the speaker to the microphone is determined. A configuration may be used in which the viewing distance is detected based on the detection result.

The luminance correction circuit 200, the viewing distance viewing distance signal supplied from the sensor 2 L _e, and based on the brightness level indicated by the one frame of pixel data DD, the luminance correction processing on the pixel data DD of each pixel Apply. Then, the brightness correction circuit 200 supplies the brightness correction pixel data PD obtained by this brightness correction processing to the SF data generation circuit 3. The detailed operation of the luminance correction circuit 200 will be described later.

  The SF data generation circuit 3 first performs multi-gradation processing such as error diffusion processing and dither processing on the luminance correction pixel data PD. For example, the SF data generation circuit 3 regards the upper bit group of the luminance correction pixel data PD as display data and the remaining lower bit group as error data. The SF data generation circuit 3 obtains error diffusion processing pixel data by reflecting the weighted addition of the error data in the pixel data corresponding to each peripheral pixel in the display data (error diffusion processing). Next, the SF data generation circuit 3 assigns dither coefficients each having a different coefficient value to each of the error diffusion processing pixel data corresponding to each pixel for each pixel group including a plurality of adjacent pixels. Then, a predetermined upper bit group in the addition result is obtained as multi-gradation pixel data (dither processing). Next, the SF data generation circuit 3 turns on and discharges the discharge cells P in each of N (N: integer) subfields SF1 to SF (N) as shown in FIG. 3 based on the multi-gradation pixel data. SF data GD is generated for each bit indicating which state in the extinguishing mode is set. The SF data generation circuit 3 sequentially supplies each SF data GD for each pixel to the SF memory 4.

  The SF memory 4 sequentially writes each of the SF data GD for each pixel, and performs the following reading operation every time writing for one frame is completed. That is, the SF memory 4 separates and reads out the bit digit corresponding to the subfield from each SF data GD for one frame in each of the subfields SF1 to SF (N) as shown in FIG. The bit DB is supplied to the address driver 6.

  The drive control circuit 20 supplies various drive control signals for driving the PDP 10 to the panel driver including the address driver 6, the X electrode driver 7, and the Y electrode driver 8 in accordance with the light emission drive sequence shown in FIG. 3. That is, the drive control circuit 20 sets the address process W and the sustain process I in each of the subfields SF1 to SF (N) shown in FIG. 3 every frame or one field display period (hereinafter referred to as a unit display period). Various control signals to be sequentially executed are supplied to the panel driver. In addition, the drive control circuit 20 supplies various control signals to be driven in accordance with the reset process R to the panel driver prior to the address process W only in the first subfield SF1. The panel drivers (address driver 6, X electrode driver 7 and Y electrode driver 8) generate drive pulses according to various control signals supplied from the drive control circuit 20 to generate column electrodes D, row electrodes X and Y of the PDP 10. To supply.

First, in the reset process R of the first subfield SF1, the X electrode driver 7 and the Y electrode driver 8 apply a reset pulse to all the row electrodes X _{1 to} X _n and the row electrodes Y _{1 to} Y _n . In response to the application of the reset pulse, reset discharge is generated in all the discharge cells P, and a predetermined amount of wall charges are formed in all the discharge cells P. Thereby, all the discharge cells P are initialized to the state of lighting mode. In the address process W of each of the subfields SF1 to SF (N), the address driver 6 generates a pixel data pulse having a pulse voltage corresponding to the logic level of the address data bit DB supplied from the SF memory 4. For example, the address driver 6 generates a pixel data pulse of a high voltage when the address data bit DB is a logic level 1 and a low voltage when the address data bit DB is a logic level 0. The address driver 6 applies such pixel data pulses to the column electrodes D _{1 to} D _m as a group of pixel data pulses for each display line (m). Further, in the address process W, the Y electrode driver 8 sequentially applies scan pulses to the row electrodes Y ₁ to Y _n at the same timing as the application timing of each pixel data pulse group. At this time, the discharge selectively occurs only in the discharge cell P at the intersection of the row electrode to which the scan pulse is applied and the column electrode to which the high-voltage pixel data pulse is applied, and remains in the discharge cell P. The wall charge that was stored is erased. That is, the discharge cell P that has lost the wall charge is set to the extinguishing mode. On the other hand, the discharge cell P in which such discharge has not occurred maintains the state immediately before that, that is, the lighting mode or the extinguishing mode.

In the subfields SF1 to SF (N) each sustain stage I, X electrode driver 7 and the Y electrode driver 8, the number of times corresponding to the luminance weight of each subfield, the row electrodes X ₁ to X _n and Y ₁ ~ repeatedly applying a sustain pulse alternately to Y _n. Each time the sustain pulse is applied, the discharge cell P in which the wall charges remain, that is, the discharge cell P in the lighting mode is sustain-discharged, and the light emission state associated with the sustain discharge is maintained.

  As a result of the above driving, sustain discharge is repeatedly generated for each unit display period by the number corresponding to the luminance level indicated by the input video signal VD, and the luminance corresponding to the total number of the sustain discharges is visually recognized.

Here, in the plasma display device shown in FIG. 1, to provide a good display image corresponding to the use environment, based on the viewing distance signal L _e detected by the viewing distance sensor 2, an input image luminance correction circuit 200 A luminance correction process is performed on the signal VD.

  FIG. 4 is a diagram showing an example of the configuration of the luminance correction circuit 200. As shown in FIG.

In FIG. 4, the luminance histogram processing circuit 21 includes storage areas associated with luminance levels “0” to “255” that are luminance ranges that can be expressed by the pixel data DD. Stores the total number of times that the pixel data DD representing the luminance level is supplied, that is, the frequency. For example, every time pixel data DD corresponding to one pixel (corresponding to one discharge cell P) is supplied, the luminance histogram processing circuit 21 stores in a storage area corresponding to the luminance level indicated by the pixel data DD. The stored number is incremented by “1”. Here, every time the above processing on the pixel data DD for one frame (or one field) is completed, the luminance histogram processing circuit 21 reads out the values stored in the respective storage areas, that is, the frequencies, and displays the respective values. As shown in FIG. 5, luminance histogram data H _id1 associated with each of luminance levels “0” to “255” is supplied to the cumulative calculation circuit 22.

The accumulation calculation circuit 22 accumulates the frequencies of the respective luminance levels “0” to “255” represented by the luminance histogram data H _{id1 in} order from the one corresponding to the low luminance (or from the one corresponding to the high luminance). to add. Here, the cumulative calculation circuit 22 sets the cumulative addition result obtained each time the frequency corresponding to one luminance level is cumulatively added as the cumulative frequency corresponding to each of the luminance levels “0” to “255”. For example, the cumulative calculation circuit 22 first _sets the frequency at the luminance level “0” represented by the luminance histogram data H _id1 as the cumulative frequency corresponding to the luminance level “0”. Next, the cumulative calculation circuit 22 sets the addition result obtained by adding the frequency at the luminance level “1” to the cumulative frequency corresponding to the luminance level “0” as the cumulative frequency corresponding to the luminance level “1”. Next, an addition result obtained by adding the frequency at the luminance level “2” to the cumulative frequency corresponding to the luminance level “1” is set as the cumulative frequency corresponding to the luminance level “2”. Next, an addition result obtained by adding the frequency at the luminance level “3” to the cumulative frequency corresponding to the luminance level “2” is set as the cumulative frequency corresponding to the luminance level “3”. The cumulative calculation circuit 22 continues to perform cumulative addition as described above to calculate cumulative frequencies corresponding to the luminance levels “4” to “255”. The cumulative frequency corresponding to the maximum luminance level “255” is always the total number of pixels of the PDP 10 (n · m). The cumulative calculation circuit 22 _generates a luminance-cumulative frequency curve AH _id1 shown in FIG. 6 representing a luminance-cumulative frequency curve in which each of the luminance levels “0” to “255” is associated with each cumulative frequency. 23 and the luminance adjustment circuit 24.

Flattening amount setting circuit 25, the viewing distance indicated by the viewing distance signal L _e, in accordance with a predetermined conversion function CH as shown in FIG. 7, the luminance represented by the cumulative brightness frequency series AH _id1 - linearizing the cumulative frequency curve This _is converted into a flattening correction amount His indicating the degree of the correction (described later), and this is supplied to the flattening processing circuit 23. Incidentally, according to the transformation function CH, viewing distance signal viewing distance indicated by L _e is large, that is becomes far more flattened correction amount H _IS is reduced.

Flattening processing circuit 23, the luminance is represented by the cumulative brightness frequency series AH _id1 as shown in FIG. 6 - relative cumulative frequency curve, the indeed flattened correction amount H _IS large, primary linear as shown in FIG. 6 The flattened cumulative luminance frequency series AH _id2 is obtained by performing the following processing that should be close to the cumulative luminance frequency series FH (one-dot broken line). As shown in FIG. 6, the primary straight line cumulative luminance frequency series FH is a primary straight line that connects the cumulative frequency corresponding to the lowest luminance “0” and the cumulative frequency corresponding to the highest luminance “255” with a straight line. It represents a series of cumulative frequencies for each luminance level assumed above.

That is, the primary linear cumulative luminance frequency series FH is
Cumulative frequency = [(P _H −P _L ) / LM _MAX ] · LM + P _L
P _H : The highest cumulative frequency represented by the cumulative luminance frequency series AH _id1
P _L : the lowest cumulative frequency represented by the cumulative luminance frequency series AH _id1
LM _MAX : Maximum luminance in the cumulative luminance frequency series AH _id1 (255)
LM: Luminance level (0 to 255)
As defined in.

The flattening circuit 23 firstly accumulates each luminance level represented by the accumulated luminance frequency series AH _id1 and each luminance level represented by the linear linear accumulated luminance frequency series FH as shown in FIG. A difference value series obtained by subtracting the accumulated frequencies corresponding to the same luminance is calculated as an accumulated frequency difference value series SK as shown in FIG. Then, flattening processing circuit 23, for the cumulative frequency difference value having a negative value in the cumulative frequency difference value sequence SK, multiplied by a coefficient whose value is small indeed larger in the flattened correction amount H _IS Thus, the shift amount SS for each cumulative frequency difference value is obtained, and this shift amount SS is added to the cumulative frequency difference value. On the other hand, with respect to the cumulative frequency difference value having a positive value in the cumulative frequency difference value sequence SK, the cumulative frequency difference values each by multiplying a coefficient value becomes smaller the more small in the flattening correction amount H _IS Shift amount SS is obtained, and this shift amount SS is subtracted from the accumulated frequency difference value. By the addition and subtraction processing of the shift amount SS as described above, the flattening processing circuit 23 obtains a flattening cumulative frequency difference value series SK _H (shown by a one-dot chain line) as shown in FIG. Then, flattening processing circuit 23, the cumulative frequency difference value between the luminance level for each represented by the flattening cumulative frequency difference value sequence SK _H, a primary linear cumulative brightness frequency series FH as shown in FIG. 6 Is added to those corresponding to the same luminance to generate a flattened cumulative luminance frequency sequence AH _id2 (shown by a broken line) as shown in FIG. , And supplied to the luminance adjustment circuit 24.

In short, in the flattening processing circuit 23, the cumulative frequency for each luminance level represented by the cumulative luminance frequency series AH _id1 is higher than the cumulative frequency shown by the primary linear cumulative luminance frequency series FH as shown in FIG. In this case, a coefficient (less than 1) to reduce this is multiplied by each of the accumulated frequencies for each luminance level in AH _id1 . At this time, the flattening processing circuit 23 sets the coefficient value to a larger value as the viewing distance (Le) increases. On the other hand, when the cumulative frequency for each luminance level represented by the cumulative luminance frequency series AH _id1 is lower than the cumulative frequency indicated by the primary linear cumulative luminance frequency series FH, the flattening processing circuit 23 _Is multiplied by a coefficient (greater than 1) to increase each of the accumulated frequencies for each luminance level in AH _id1 . At this time, the flattening processing circuit 23 sets the coefficient value to a smaller value as the viewing distance (Le) increases.

According to the above processing, as the viewing distance (Le) _decreases , the luminance-cumulative frequency curve represented by the flattened cumulative luminance frequency sequence AH _id2 becomes a linear linear cumulative luminance frequency sequence FH as shown in FIG. A flattened cumulative luminance frequency series AH _id2 having an approaching form is obtained.

  The luminance adjustment circuit 24 obtains luminance correction pixel data PD by performing the following luminance adjustment processing on the luminance level for each pixel (discharge cell P) represented by the pixel data DD, and obtains this as shown in FIG. The data is supplied to the SF data generation circuit 3 as shown.

That is, the luminance adjustment circuit 24 first sets the maximum frequency (n · m) to the maximum luminance (input video) as the cumulative frequency for each luminance level represented by the flattened cumulative luminance frequency series AH _id2 as shown in FIG. In the form in which the lowest frequency coincides with the lowest luminance level 0, and is normalized to a value (referred to as a normalized luminance level). Then, the luminance adjustment circuit 24 _{obtains the} normalized luminance level corresponding to the luminance level represented by the pixel data DD based on the flattened cumulative luminance frequency series AH _id2, and _obtains the pixel data representing the level as the luminance correction pixel. Let it be data PD. For example, when the luminance level represented by the pixel data DD is L1 as shown in FIG. 6, a normalized luminance level L2 corresponding to the luminance level L1 is obtained based on the flattened cumulative luminance frequency series AH _id2 . Then, the luminance adjustment circuit 24 supplies pixel data representing the normalized luminance level L2 to the SF data generation circuit 3 as luminance correction pixel data PD.

  Therefore, according to the luminance correction circuit 200 having the above-described configuration, when the luminance level represented by the pixel data DD is higher than the intermediate luminance level LC as shown in FIG. As the viewing distance (Le) decreases, the luminance-corrected pixel data PD subjected to the luminance adjustment that should reduce the luminance level is obtained. On the other hand, when the luminance level represented by the pixel data DD is lower than the intermediate luminance level LC, as the viewing distance (Le) decreases, the luminance adjustment for increasing the luminance level of the pixel data DD is performed. The applied luminance correction pixel data PD is obtained. In other words, the luminance correction circuit 200 performs a correction process on the supplied pixel data DD so as to reduce the luminance difference between the gradations and increase the luminance gradation expression capability as the viewing distance (Le) decreases. is there.

Further, in the luminance correction circuit 200, as the viewing distance (Le) _decreases , the luminance-cumulative frequency curve represented by the flattened cumulative luminance frequency sequence AH _id2 is represented by a linear linear cumulative luminance frequency sequence FH as shown in FIG. Corrections that should be close to the form are made. At this time, as the brightness-cumulative frequency curve represented by the flattened cumulative brightness frequency series AH _id2 is further away from the form of the linear linear cumulative brightness frequency series FH as shown in FIG. 6, the brightness level (L1) by the pixel data DD is increased. On the other hand, the luminance difference from the intermediate luminance level LC of the luminance level (L2) by the luminance correction pixel data PD becomes large. That is, the degree of contrast enhancement is increased. That is, the luminance correction circuit 200 performs a correction process for increasing the contrast enhancement degree as the viewing distance (Le) increases with respect to the pixel data PC. As a result, it is possible to provide a good display image that follows the human visual characteristic that the sensitivity to contrast becomes more sensitive as the viewing distance increases. At this time, when the viewing distance is short, the human visual characteristics are more sensitive to the expression of luminance gradation than the contrast. Therefore, at this time, the degree of contrast enhancement is lowered by increasing the degree of linearization with respect to the luminance-accumulated frequency curve represented by the flattened accumulated luminance frequency series AH _id2 . As a result, the luminance difference between each gradation is reduced and the luminance gradation expression ability is increased, so that it is good to follow human visual characteristics that the closer the viewing distance is, the more sensitive to the luminance change in the image. A display image is provided.

  When the peak ACL (Automatic Contrast Limiter) process is performed on the pixel data DD in order to automatically adjust the degree of contrast enhancement as described above, the luminance adjustment amount by the peak ACL process is corrected according to the viewing distance. You may make it do. At this time, the peak ACL processing is pixel data corresponding to all the pixels for one frame so that the peak luminance in the input video signal for one frame becomes the highest luminance within the luminance range that can be expressed in the display device. On the other hand, contrast enhancement is performed by performing luminance adjustment processing.

  FIG. 9 is a diagram illustrating an example of an internal configuration of the luminance correction circuit 200 that is employed instead of the configuration illustrated in FIG. 4 when the peak ACL processing is performed in the luminance correction circuit 200.

In FIG. 9, the luminance histogram processing circuit 26 includes storage areas associated with the luminance levels “0” to “255”, which are luminance ranges that can be expressed by the pixel data DD, in each storage area. The total number of times that the pixel data DD representing the luminance level is supplied, that is, the frequency is stored. For example, every time the pixel data DD corresponding to one pixel (corresponding to one discharge cell P) is supplied, the luminance histogram processing circuit 26 stores in the storage area corresponding to the luminance level indicated by the pixel data DD. The stored number is incremented by “1”. Here, every time the above processing on the pixel data DD for one frame (or one field) is completed, the luminance histogram processing circuit 26 reads out the values stored in the respective storage areas, that is, the frequencies, and displays the respective values. and it supplies the cumulative operation circuit 27 as the luminance histogram data H _id representing an association with the luminance level "0" to "255", respectively as shown in 10.

The cumulative calculation circuit 27 sets the frequency for each of the luminance levels “0” to “255” represented by the luminance histogram data H _{id in} order from one corresponding to low luminance (or from one corresponding to high luminance). Cumulative addition. Here, the cumulative calculation circuit 27 sets the cumulative addition result obtained each time the frequency corresponding to one luminance level is cumulatively added to the cumulative frequency corresponding to each of the luminance levels “1” to “255”. For example, the cumulative calculation circuit 27 first corresponds to the luminance level “1” by adding the result of the frequency at the luminance level “0” represented by the luminance histogram data H _id and the frequency at the luminance level “1”. Cumulative frequency. Next, an addition result obtained by adding the frequency at the luminance level “2” to the cumulative frequency corresponding to the luminance level “1” is set as the cumulative frequency corresponding to the luminance level “2”. Next, an addition result obtained by adding the frequency at the luminance level “3” to the cumulative frequency corresponding to the luminance level “2” is set as the cumulative frequency corresponding to the luminance level “3”. The cumulative calculation circuit 27 subsequently calculates the cumulative frequency corresponding to each of the luminance levels “4” to “255” by sequentially executing the cumulative addition as described above. The cumulative frequency corresponding to the maximum luminance level “255” is always the total number of pixels of the PDP 10 (n · m). The cumulative calculation circuit 27 detects a substantial peak luminance from a cumulative luminance frequency series AH _id3 as shown in FIG. 11 representing a luminance-cumulative frequency curve in which each of the luminance levels “1” to “255” is associated with each cumulative frequency. This is supplied to the circuit 28 and the inflection point detection circuit 29.

The substantial peak luminance detection circuit 28 detects the luminance level corresponding to the preset cumulative frequency H _C as shown in FIG. 11 as the substantial peak luminance from the accumulated luminance frequency series AH _{id3 for} each frame, A substantial peak luminance signal PY indicating the luminance level is supplied to the luminance adjustment gain calculation circuit 30. The cumulative frequency H _C is a value of c% (90 ≦ c <100) of the maximum cumulative frequency (n · m). That is, in the real peak luminance detecting circuit 28, a luminance level corresponding to than the maximum cumulative frequency becomes smaller by a predetermined value cumulative frequency (H _C), it is to detect a substantial peak intensity (PY).

The inflection point detection circuit 29 detects the luminance level corresponding to the preset cumulative frequency H _B as shown in FIG. 11 as the inflection point luminance from the cumulative luminance frequency series AH _id3 , and indicates the luminance level. The inflection point luminance signal B is supplied to the luminance adjustment circuit 32. The cumulative frequency H _B is a value of b% (b <c) of the maximum cumulative frequency (n · m).

Correction amount setting circuit 31, the viewing distance indicated by the viewing distance signal L _e, in accordance with a predetermined conversion function COR as shown in FIG. 12, converts the correction amount PG _COR showing a correction amount for the brightness adjustment gain (to be described later) This is supplied to the luminance adjustment gain calculation circuit 30. Incidentally, according to the transformation function COR, viewing distance indicated by the viewing distance signal L _e is large, i.e. increasing distance correction PG _COR increases.

The luminance adjustment gain calculation circuit 30 calculates a luminance adjustment gain signal PG indicating a luminance adjustment gain value from the actual peak luminance signal PY based on a gain calculation linear function F as shown in FIG. Supply. As shown in FIG. 13, the gain calculation linear function F is the lowest luminance adjustment when the peak luminance represented by the actual peak luminance signal PY is equal to the maximum luminance PY _MAX that can be expressed by the plasma display device. The gain value (eg, “1”) is obtained, and the function is such that a larger brightness adjustment gain is obtained as the actual peak brightness (PY) becomes lower.

Here, the luminance adjustment gain calculation circuit 30 calculates the luminance adjustment gain (PG) using the gain calculation linear function F in which the negative slope increases as the correction amount indicated by the correction amount PG _COR increases. . For example, the luminance adjustment gain calculation circuit 30 performs the gain calculation linear function F _UP shown in FIG. 13 when the correction amount PG _COR is relatively large, and the gain calculation linear function shown in FIG. 13 when the correction amount PG _COR is small. and calculates the luminance adjustment gain (PG) using F _DN. At this time, the correction amount PG _COR is proportional to the viewing distance (Le) as shown in FIG. Therefore, a larger luminance adjustment gain (PG) is obtained as the actual peak luminance (PY) is lower, and the luminance adjustment gain (PG) is larger as the viewing distance (Le) is larger.

  When the pixel data DD represents a luminance level equal to or higher than the luminance level indicated by the inflection point luminance signal B, the luminance adjustment circuit 32 sets the luminance adjustment gain signal to the luminance level represented by the pixel data DD. Multiply the brightness adjustment gain indicated by PG. Then, the luminance adjustment circuit 32 generates luminance correction pixel data PD representing the luminance level obtained by the multiplication, and supplies this to the SF data generation circuit 3 as shown in FIG. When the pixel data DD represents a luminance level lower than the luminance level indicated by the inflection point luminance signal B, the luminance adjustment circuit 32 uses the pixel data DD as the luminance correction pixel data PD as it is as SF data. This is supplied to the generation circuit 3.

According to the configuration shown in FIG. 9, as shown in FIG. 13, as the correction amount PG _COR increases, that is, as the viewing distance (Le) increases, the predetermined luminance level (the luminance level indicated by the inflection point luminance signal B). ) The luminance adjustment gain (PG) for the pixel data DD representing the above luminance level is increased. Therefore, high luminance enhancement processing is performed on the pixel data DD so as to make the high luminance level higher. As a result, the greater the viewing distance (Le), the higher the degree of contrast enhancement of the image. Therefore, a good display image that follows the human visual characteristic of being more sensitive to contrast as the viewing distance increases is provided. Will come to be. At this time, when the viewing distance is short, the luminance adjustment gain (PG) is small, so the degree of contrast enhancement is lowered, and the luminance difference between the gradations is small. In other words, the ability to express luminance gradation increases as the luminance difference between each gradation decreases, so a good display image that follows human visual characteristics that the closer the viewing distance is, the more sensitive to changes in luminance in the image. Will be offered.

Here, in the luminance correction circuit 200 shown in FIG. 9, when detecting the peak luminance for each frame in the peak ACL processing, the maximum luminance is not directly detected from the input video signal for one frame. As shown, a luminance level (PY) corresponding to a predetermined cumulative frequency H _C is detected as a substantial peak luminance from the cumulative luminance frequency series AH _id3 . That is, the luminance level (PY) corresponding to the cumulative frequency H _C that is smaller than the maximum cumulative frequency (n · m) by a predetermined value from the cumulative luminance frequency series AH _id3 calculated for each frame is used as the peak luminance. It is trying to detect. This is to prevent the following unnatural display state that occurs when the peak luminance is detected directly from the input video signal for one frame. That is, when a high brightness banner (bunner) such as subtitles or breaking news suddenly appears in the image frame, if the peak brightness is detected directly from the input video signal for one frame, the brightness level in this banner area Will be detected as the peak luminance. Therefore, when luminance adjustment is performed on each pixel data DD for one frame with the luminance adjustment gain (PG) corresponding to the luminance level in the banner area, an image with little luminance change with time change is displayed. Even so, a so-called screen flickering occurs in which the brightness level of the entire screen suddenly changes at the start and end of the banner display.

On the other hand, in the luminance correction circuit 200 as shown in FIG. 9, the luminance level (PY) corresponding to the cumulative frequency H _C that is smaller than the maximum cumulative frequency by a predetermined value from the cumulative luminance frequency series AH _id3 is substantially reduced. Peak brightness. That is, a luminance level slightly smaller than the actual peak luminance in the input video signal (pixel data DD) for one frame is a substantial peak luminance, which is relatively low such as a banner area where subtitles, breaking news, etc. are displayed. The brightness level in a narrow area is not a target for peak brightness detection. Therefore, even when such a banner region suddenly appears in the screen, the peak ACL processing can be performed without causing the screen to flicker.

In the peak ACL processing by the luminance correction circuit 200, each pixel data is set so that the actual peak luminance (PY) for each frame based on the input video signal becomes the maximum luminance that can be expressed in the plasma display device shown in FIG. Brightness adjustment processing is performed on the DD. Accordingly, the luminance levels included between the real peak luminance level (PY) and the maximum luminance level “255” as shown in FIG. 11 are all uniformly expressed as the maximum luminance that can be expressed in the plasma display device. As a result, the image area displayed within the range from the substantial peak luminance level (PY) to the maximum luminance level “255” is displayed as “whiteout”. As the viewing distance (Le) decreases, the “whiteout” is more easily recognized by the viewer and causes a sense of discomfort. Therefore, in the luminance correction circuit 200 shown in FIG. 9, as the correction amount PG _COR is smaller, that is, as the viewing distance (Le) is smaller, the luminance adjustment gain (PG) is decreased as shown in FIG. The occurrence of “white-out” is suppressed. On the other hand, as the viewing distance (Le) increases, this “whiteout” is less likely to be recognized. Conversely, the luminance adjustment gain (PG) is increased to increase the contrast.

  Further, in the luminance correction circuit 200, a luminance level equal to or higher than a predetermined inflection point luminance (B) as shown in FIG. 11 in the input video signal (pixel data DD) is targeted for peak ACL processing. Therefore, since the luminance level indicated by the input video signal is maintained as it is at the intermediate luminance level where the frequency increases, the contrast is maintained while maintaining the gradation reproducibility as compared with the case where all the luminance levels are subjected to the peak ACL processing. It is possible to enhance the feeling.

  Further, since the peak ACL is executed only for a part of high luminance levels equal to or higher than the predetermined inflection point luminance (B), compared to the case where the entire luminance level is the target of the peak ACL processing, It is possible to enhance the contrast while suppressing an increase in power consumption accompanying the increase in luminance.

  In the luminance correction circuit 200 shown in FIG. 9, the pixel data DD having a luminance level equal to or higher than the predetermined inflection point luminance (B) is set as the target of the peak ACL processing as described above. An ACL processing target may also be used. Further, in performing the peak ACL processing for all luminance levels as described above, the luminance adjustment circuit 32 uses the luminance adjustment gain (PG) calculated based on the gain calculation linear function F as shown in FIG. Instead of multiplying the pixel data DD, the brightness correction pixel data PD may be generated by adding the values.

  In the luminance correction circuit 200 shown in FIG. 9, the peak ACL processing for adjusting the high luminance level to higher luminance is performed on the pixel data DD in order to enhance the contrast of the entire display image. However, a process for adjusting a low luminance level to a lower luminance may be performed.

  FIG. 14 is a diagram illustrating a configuration of a luminance correction circuit 200 that is used when black extension processing for adjusting a low luminance level to a lower luminance is performed on the pixel data DD when enhancing the contrast.

In FIG. 14, the luminance histogram processing circuit 36 includes storage areas associated with the luminance levels “0” to “255”, which are luminance ranges that can be represented by the pixel data DD, in each storage area. The total number of times that the pixel data DD representing the luminance level is supplied, that is, the frequency is stored. For example, every time the pixel data DD corresponding to one pixel (corresponding to one discharge cell P) is supplied, the luminance histogram processing circuit 36 stores in the storage area corresponding to the luminance level indicated by the pixel data DD. The stored number is incremented by “1”. Here, every time the above processing on the pixel data DD for one frame (or one field) is completed, the luminance histogram processing circuit 36 reads out the values stored in the respective storage areas, that is, the frequencies, and displays them. luminance level "0" to "255" as shown in 10 and supplies the cumulative operation circuit 37 as the luminance histogram data H _id representing an association with each other.

The cumulative calculation circuit 37 sets the frequency for each of the luminance levels “0” to “255” represented by the luminance histogram data H _{id in} order from the one corresponding to the low luminance (or the one corresponding to the high luminance). Cumulative addition. Here, the cumulative calculation circuit 37 sets the cumulative addition result obtained each time the frequency corresponding to one luminance level is cumulatively added to the cumulative frequency corresponding to each of the luminance levels “1” to “255”. For example, the accumulating circuit 37 first corresponds the result of adding the frequency at the luminance level “0” represented by the luminance histogram data H _id and the frequency at the luminance level “1” to the luminance level “1”. Cumulative frequency. Next, an addition result obtained by adding the frequency at the luminance level “2” to the cumulative frequency corresponding to the luminance level “1” is set as the cumulative frequency corresponding to the luminance level “2”. Next, an addition result obtained by adding the frequency at the luminance level “3” to the cumulative frequency corresponding to the luminance level “2” is set as the cumulative frequency corresponding to the luminance level “3”. The accumulation operation circuit 37 calculates the accumulation frequency corresponding to each of the luminance levels “4” to “255” by sequentially executing the accumulation addition as described above. The cumulative frequency corresponding to the maximum luminance level “255” is always the total number of pixels of the PDP 10 (n · m). The cumulative calculation circuit 37 detects a substantial bottom luminance from a cumulative luminance frequency series AH _id4 as shown in FIG. 15 representing a luminance-cumulative frequency curve in which each of the luminance levels “1” to “255” is associated with each cumulative frequency. This is supplied to the circuit 38 and the inflection point detection circuit 39.

The real bottom luminance detection circuit 38 detects the luminance level corresponding to the preset cumulative frequency H _d from the cumulative luminance frequency series AH _id4 as shown in FIG. 15 as the substantially minimum luminance, and indicates the luminance level. The substantial bottom luminance signal BY is supplied to the luminance adjustment coefficient calculation circuit 40. The cumulative frequency H _d is a value of d% (d <10) of the maximum cumulative frequency (n · m).

Inflection point detection circuit 39, from among the accumulated brightness frequency series AH _id4, the luminance level corresponding to the cumulative frequency H _e, which is set such advance shown in FIG. 15 is detected as an inflection point brightness, indicating the luminance level The inflection point luminance signal E is supplied to the luminance adjustment circuit 42. Incidentally, the cumulative frequency H _e is the value of e% of the maximum cumulative frequency (n · m) (d < e ≦ 50).

Correction amount setting circuit 41, converts the viewing distance indicated by the viewing distance signal L _e, in accordance with a predetermined conversion function COR _K as shown in FIG. 16, the correction amount KG _COR showing a correction amount for the luminance adjustment coefficient (described later) This is supplied to the luminance adjustment coefficient calculation circuit 40. Incidentally, according to the transformation function COR _K, viewing distance indicated by the viewing distance signal L _e is large, i.e. increasing distance correction amount KG _COR increases.

The luminance adjustment coefficient calculation circuit 40 calculates a luminance adjustment coefficient signal KV indicating the luminance adjustment coefficient from the actual bottom luminance signal BY based on the adjustment coefficient calculation linear function G as shown in FIG. Supply. Note that, as shown in FIG. 17, the adjustment coefficient calculation linear function G has the lowest value when the lowest luminance represented by the substantially bottom luminance signal BY is equal to the lowest luminance 0 that can be expressed by this plasma display device. The function is such that a luminance adjustment coefficient is obtained, and as the actual bottom luminance (BY) increases, a larger luminance adjustment coefficient is obtained. Further, the luminance adjustment coefficient calculation circuit 40 calculates the luminance adjustment coefficient (KV) using the adjustment coefficient calculation linear function G in which the inclination increases as the correction amount indicated by the correction amount KG _COR increases. For example, the luminance adjustment coefficient calculation circuit 40 uses the gain calculation function G _UP shown in FIG. 17 when the correction amount KG _COR is relatively large, and the gain calculation function G _DN shown in FIG. 17 when it is small. The luminance adjustment coefficient (KV) is calculated. At this time, the correction amount KG _COR is proportional to the viewing distance (Le) as shown in FIG. Therefore, a larger luminance adjustment coefficient (KV) is obtained as the substantial bottom luminance (BY) is higher, and the luminance adjustment coefficient (KV) is larger as the viewing distance (Le) is larger.

  For each frame of the pixel data DD, the peak luminance detection circuit 43 detects the pixel data DD indicating the highest luminance level in the one frame, and the luminance of the peak luminance signal PK indicating the luminance level as the peak luminance. This is supplied to the adjustment circuit 42.

  When the pixel data DD represents a luminance level equal to or lower than the luminance level indicated by the inflection point luminance signal E, the luminance adjustment circuit 42 performs the following black expansion on the luminance level indicated by the pixel data DD. By performing the calculation, the luminance correction pixel data PD is obtained and supplied to the SF data generation circuit 3 as shown in FIG.

PD = PK- (PK-DD) · KV
PK: Peak luminance indicated by the peak luminance signal PK
KV: the luminance adjustment coefficient indicated by the luminance adjustment coefficient signal KV. Note that the luminance adjustment circuit 42 uses this pixel when the pixel data DD represents a luminance level higher than the luminance level indicated by the inflection point luminance signal E. The data DD is supplied as it is to the SF data generation circuit 3 as the brightness correction pixel data PD.

According to the configuration shown in FIG. 14, as shown in FIG. 17, the predetermined luminance level (the luminance level indicated by the inflection point luminance signal E increases as the correction amount KG _COR increases, that is, the viewing distance (Le) increases. ) The luminance adjustment coefficient (KV) for the pixel data DD representing the following low luminance increases. Therefore, according to the above black expansion calculation, the luminance level indicated by the luminance correction pixel data PD decreases as the luminance adjustment coefficient (KV) increases. In other words, the pixel data DD is subjected to a so-called black expansion process in which a low luminance level is made lower. As a result, the greater the viewing distance (Le), the higher the degree of contrast enhancement of the image. Therefore, a good display image that follows the human visual characteristic of being more sensitive to contrast as the viewing distance increases is provided. Will come to be. At this time, when the viewing distance (Le) is short, the luminance adjustment coefficient (KV) is small, so that the degree of contrast enhancement is lowered, and the luminance difference between the gradations is reduced. Therefore, the ability to express luminance gradations increases as the luminance difference between each gradation decreases, so a good display image that follows human visual characteristics that the closer the viewing distance is, the more sensitive to changes in luminance in the image. Will be offered.

Here, the luminance correction circuit 200 shown in FIG. 14 detects the minimum luminance directly from the input video signal for one frame when detecting the bottom luminance for each frame so as to perform the black expansion processing as described above. Instead, as shown in FIG. 15, the luminance level (BY) corresponding to the cumulative frequency H _d that is d% (d <10) of the maximum cumulative frequency (n · m) is _selected from the cumulative luminance frequency series AH _id4. Detection is made as a substantial bottom luminance. This is to prevent the following unnatural display state that occurs when the minimum luminance is detected directly from the input video signal for one frame. That is, for example, when a banner (bunner) such as subtitles or breaking news with a black background suddenly appears in the image frame, if the minimum luminance is detected directly from the input video signal for one frame, The luminance level 0 corresponding to the black background is detected as the minimum luminance. Therefore, when the luminance adjustment is performed on each pixel data DD for one frame with the luminance adjustment coefficient (KV) corresponding to the luminance level 0 in the banner area, an image with little luminance change with time change is obtained. Even if the image is displayed, a so-called screen flickering occurs in which the brightness level of the entire screen suddenly changes at the display start time and end time of the banner.

On the other hand, as shown in FIG. 15, the luminance correction circuit 200 as shown in FIG. 14 corresponds to the cumulative frequency H _d that is larger than the minimum cumulative frequency 0 by a predetermined value from the cumulative luminance frequency series AH _id4 . The luminance level (BY) is a substantial bottom luminance. That is, a luminance level slightly higher than the actual bottom luminance in the input video signal (pixel data DD) for one frame is a substantial bottom luminance, and is relatively narrow like a banner area where subtitles, breaking news, etc. are displayed. The luminance level in the region is not a target for bottom luminance detection. Therefore, even when such a banner region suddenly appears in the screen, it is possible to perform the black expansion process without causing the screen to flicker.

Further, in the black expansion processing by the luminance correction circuit 200, each pixel data is set so that the actual bottom luminance (BY) for each frame based on the input video signal becomes the minimum luminance that can be expressed in the plasma display device shown in FIG. Brightness adjustment is made to DD. Therefore, the luminance levels included between the real bottom luminance (BY) and the lowest luminance level “0” as shown in FIG. 15 are all uniformly expressed as the lowest luminance that can be expressed in the plasma display device. As a result, as shown in FIG. 15, the image area displayed within the range from the substantial bottom luminance (BY) to the lowest luminance level “0” is displayed as “blackout”. This “blackout” is more easily recognized by the viewer as the viewing distance (Le) becomes shorter, causing a sense of discomfort. Therefore, in the luminance correction circuit 200 shown in FIG. 14, as shown in FIG. 17, the black adjustment factor (KV) is reduced as the correction amount KG _COR is smaller, that is, the viewing distance (Le) is smaller. The amount of decrease in brightness due to the decompression process is suppressed to prevent the occurrence of “blackout”. On the other hand, as the viewing distance (Le) increases, this “blackout” is less likely to be recognized. Conversely, in order to increase the contrast feeling, the luminance adjustment coefficient (KV) is increased to reduce the luminance reduction amount due to the black expansion processing. Increase it.

  In addition, in the luminance correction circuit 200 shown in FIG. 14, a luminance level equal to or lower than a predetermined inflection point luminance (E) as shown in FIG. 15 in the input video signal (pixel data DD) is targeted for black expansion processing. Therefore, since the luminance level indicated by the input video signal is maintained as it is at the intermediate luminance level where the frequency is increased, the contrast is maintained while maintaining the gradation reproducibility as compared with the case where all the luminance levels are subjected to the black expansion processing. It is possible to enhance the feeling.

In the luminance correction circuit 200 shown in FIG. 14, as described above, the pixel data DD having a luminance level equal to or lower than the predetermined inflection point luminance (E) is the target of the black extension processing. It may be the target of decompression processing. Further, in performing the black expansion processing for all the luminance levels as described above, the luminance adjustment circuit 42 applies the pixel data DD to the pixel data DD.
PD = DD-KV
The luminance correction pixel data PD may be obtained by performing the black expansion calculation process. In other words, the luminance level expressed by each frame of pixel data DD is multiplied by an offset that should uniformly reduce the luminance level by the luminance adjustment coefficient (KV).

  FIG. 18 is a diagram showing another configuration of the plasma display apparatus for driving the plasma display panel according to the driving method of the present invention.

  The plasma display device shown in FIG. 18 employs a luminance correction circuit 300 that performs luminance correction for suppressing streaking, which is a stripe-like distortion in an image, instead of the luminance correction circuit 200 shown in FIG. . The streaking is a luminance variation phenomenon in units of display lines caused by a decrease in sustain pulse voltage as a display line having a larger light emission load when a light emission load is different for each display line.

  18 is the same as that shown in FIG. 1 except for the point that the luminance correction circuit 300 is adopted, and the operation will be described below with a focus on the operation of the luminance correction circuit 300.

  FIG. 19 is a diagram showing an internal configuration of the luminance correction circuit 300. As shown in FIG.

  In FIG. 19, the drive data generation circuit 301 first performs multi-gradation processing including error diffusion processing and dither processing on the pixel data DD supplied from the A / D converter 1. For example, the drive data generation circuit 301 regards the upper bit group of the pixel data DD as display data and the remaining lower bit group as error data. At this time, the drive data generation circuit 301 obtains error diffusion processing pixel data by reflecting the weighted addition of the error data in the pixel data corresponding to each peripheral pixel in the display data (error diffusion processing). Next, for each pixel group composed of a plurality of adjacent pixels, each of the error diffusion processing pixel data corresponding to each pixel is assigned with a dither coefficient composed of a different coefficient value, and is added. A predetermined upper bit group is obtained as multi-gradation pixel data (dither processing). The drive data generation circuit 301 turns on and off the discharge cells P in each of N (N: integer) subfields SF1 to SF (N) as shown in FIG. 3 based on the multi-gradation pixel data. Drive data GDD indicating which state is set in each mode is generated and supplied to the cell number calculation circuit 302 and the correction coefficient generation circuit 303 sequentially. For example, the first to Nth bits of the drive data GDD correspond to each of the subfields SF1 to SF (N), and when the bit digit is at the logic level 1, the subbit corresponding to this bit digit is assigned. While the discharge cell P is set in the lighting mode state in the field SF, the logic level 0 indicates that the discharge cell P is set in the extinguishing mode state.

  Based on the drive data GDD supplied from the drive data generation circuit 301, the cell number calculation circuit 302 calculates the total number of discharge cells P set in the lighting mode state for each display line in the PDP 10 for each subfield. Counting is performed for each emission color (red, blue, and green), and count data LN indicating the count value LN (i, c) is supplied to the correction factor generation circuit 304. In the LN (i, c), i represents a subfield number, and c represents the emission color (R, G, or B) of the discharge cell P. At this time, the load on the display line increases as the number of discharge cells set in the lighting mode state among the discharge cells P belonging to the display line for each display line increases. In the present embodiment, the count value LN (i, c) itself is calculated as a load, but the present invention is not limited to this. For example, instead of the count value LN (i, c), a value such as an impedance corresponding to the count value LN (i, c) may be used as the load.

  The correction factor generation circuit 304 calculates correction factor data SG for each emission color for each display line based on the count data LN. Specifically, the correction factor data SG includes data of 3 × M SF correction factors SG (i, c) (i: subfield number, c: R, B or G), and SF correction factor SG ( i, c) is calculated according to the following equation (1), for example.

α (i, c): Positive weighting factor
R (i): Effective load
m: Total number of discharge cells P belonging to one display line
ω: exponent (eg “2”)
Here, in the above equation (1), the effective load R (i) is given by the following equation (1A), for example.

  Β (i, R), β (i, G), and β (i, B) are positive weighting factors, and have characteristics such as luminance saturation characteristics, color purity, and deterioration characteristics of the phosphor for each color. This is a coefficient determined based on this. At this time, it is desirable that the coefficients β (i, R), β (i, G), β (i, B) and the effective load R (i) comply with the following constraint conditions (1B) and (1C).

  Further, instead of the above equation (1), a value calculated by using the value given by the above equation (1), for example, the 1/2 power of SG (i, c) may be used as the SF correction factor. According to the above equation (1), when all the discharge cells P in the display line to be processed (hereinafter referred to as a current display line) are set to the lighting mode state, the SF correction factor SG (i, c) is the minimum value “1”, and when all the discharge cells P are set to the extinguishing mode, the SF correction factor SG (i, c) is the maximum value “1 + α (i, c)”. Therefore, the SF correction factor SG (i, c) is smaller as the load is larger, and the SF correction factor SG (i, c) is larger as the load is smaller.

  The correction coefficient generation circuit 303 emits light with the emission color c in each display line based on the correction factor data SG supplied from the correction factor generation circuit 304 and the drive data GDD supplied from the drive data generation circuit 301. A correction coefficient G (Q, c) (Q = 1 to m) corresponding to the discharge cell P in the Qth column is calculated. The drive data GDD is supplied from the drive data generation circuit 301 to the correction coefficient generation circuit 303 via a delay circuit (not shown). The correction coefficient G (Q, c) is calculated according to the following equation (2), for example.

1 / γ: exponent (for example, 1/2)
g (Q, c): Correction factor per field (field correction factor)
Note that g (Q, c) is given by the following equation (2A).

  In the above equation (2A), the coefficients EN (i) and CF (i) are given by the following equations (2B) and (2C), respectively.

T (i): Sustain period or the number of sustain discharges of the i-th subfield SFi B (i): A value indicating the mode state (lighted or turned off) of the discharge cell P to be corrected. The ratio of the sustain period or the number of sustain discharges in the i-th subfield in FIG. When all the EN (i) values are zero, it is defined that CF (i) = 0.

  The correction coefficient generation circuit 303 supplies coefficient data CD indicating the correction coefficient G (Q, c) calculated as described above to the multiplier 305.

Suppression coefficient calculation circuit 306, a viewing distance indicated by the viewing distance signal L _e, in accordance with a predetermined conversion function COL as shown in FIG. 20, converts the suppression coefficient K indicating the degree to weaken the streaking correction, which multiplier 305 is supplied.

  The multiplier 305 supplies the multiplication result obtained by multiplying the correction coefficient G (Q, c) indicated by the coefficient data CD by the suppression coefficient K to the multiplier 307 as the streaking correction coefficient KCD.

  The delay memory 308 supplies the pixel data DD delayed by a time corresponding to one display line to the multiplier 307 and the adder 309, respectively.

  The multiplier 307 and the adder 309 calculate the brightness adjustment pixel data PD by calculation according to the following equation (3).

  The PD (Q, c) indicates the luminance value (gradation value) of the pixel data DD corresponding to the Qth discharge cell P having the emission color c in the current display line. Since the above equation (3) can be transformed into the following equation (3A), a configuration according to the following equation (3A) may be adopted instead of the configuration according to the above equation (3).

  According to the configuration as described above, for example, when all the discharge cells P in the current display line emit light, that is, when the load is maximized, the correction amount with respect to the luminance of the pixel data DD is minimized. DD is sent out as brightness adjustment pixel data PD as it is without correcting the brightness value. On the other hand, when all the discharge cells P in the current display line do not emit light, that is, when the load is minimum, the correction amount of the luminance value is maximized.

  That is, the luminance correction circuit 300 adjusts the luminance level for the pixel data DD corresponding to the display line with a correction amount that decreases as the light emission load amount on the display line increases for each display line. is there. Therefore, according to the luminance correction circuit 300, the light emission of the discharge cell P is reduced for each display line so as to reduce the luminance variation in units of display lines due to the difference in the light emission load amount of each display line, that is, to suppress the streaking. For each color, the luminance adjustment is performed on the pixel data DD. The luminance correction circuit 300 supplies the luminance adjustment pixel data PD obtained by the luminance adjustment to the SF data generation circuit 3. The SF data generation circuit 3 performs the same processing as that of the drive data generation circuit 301 on the luminance adjustment pixel data PD, so that the N subfields SF1 to SF (N) as shown in FIG. Then, the SF data GD is generated for each bit indicating whether the discharge cell P is set in the on or off mode.

  Therefore, in the plasma display device shown in FIG. 18, even if the luminance saturation characteristics are different for each of the R, G, and B phosphors in the discharge cell P, streaking is suppressed without causing color misregistration. It becomes like this.

  Here, in the luminance correction circuit 300, when performing the luminance correction for suppressing the streaking as described above, the suppression coefficient K for which the correction amount should be decreased as the viewing distance (Le) is increased. The coefficient data CD indicating c) is multiplied.

  That is, when the viewing distance is short, the display image looks relatively bright, and the lack of screen uniformity is conspicuous. Therefore, when the viewing distance is short as described above, the coefficient data CD is multiplied by a small suppression coefficient K in order to increase the streaking correction that results in a screen with uniform brightness. On the other hand, when the viewing distance is long, the adverse effect of darkening the display is more conspicuous than the effect of improving the screen uniformity by streaking correction. Therefore, when the viewing distance is long as described above, the coefficient data CD is multiplied by a large suppression coefficient K in order to prevent the display image from becoming darker than necessary. Reduce streaking correction.

  Therefore, according to the luminance correction circuit 300 as shown in FIG. 19, a good image in which a decrease in luminance of the display image is suppressed can be provided while performing luminance correction for suppressing streaking.

  FIG. 21 is a diagram showing another configuration of the plasma display apparatus for driving the plasma display panel according to the driving method of the present invention.

  The plasma display device shown in FIG. 21 adds a illuminance sensor 2a to the configuration shown in FIG. 1, and performs luminance correction that follows human adaptation luminance instead of the luminance correction circuit 200 shown in FIG. The correction circuit 400 is employed. The adaptation luminance is luminance that is viewed when the viewer looks at the display screen of the PDP 10 in the viewing environment. For example, the higher the adaptation brightness (brighter), the higher the sensitivity of the dynamic range of the human eye, and the displayed image will appear darker overall, while the lower the adaptation brightness (darker), the brighter the display image will be. I can feel it.

  21 is the same as that shown in FIG. 1 except for the point that the illuminance sensor 2a and the luminance correction circuit 400 are employed. Therefore, the operation will be described below with a focus on the illuminance sensor 2a and the luminance correction circuit 400.

  For example, as shown in FIG. 2, the illuminance sensor 2 a is installed on the periphery of the display surface 11 of the plasma display device body, that is, on the surface of the screen frame 12. The illuminance sensor 2a detects the brightness of the space in which the plasma display device is installed (hereinafter referred to as environmental illuminance), and supplies an environmental illuminance signal Y indicating the brightness to the luminance correction circuit 400. The environmental illuminance does not include the influence of light emitted from the screen of the plasma display device.

  FIG. 22 is a diagram showing an internal configuration of the luminance correction circuit 400. As shown in FIG.

In FIG. 22, the luminance histogram processing circuit 406 includes storage areas associated with the luminance levels “0” to “255”, which are luminance ranges that can be expressed by the pixel data DD. The total number of times that the pixel data DD representing the luminance level is supplied, that is, the frequency is stored. For example, each time the pixel data DD corresponding to one pixel (corresponding to one discharge cell P) is supplied, the luminance histogram processing circuit 406 stores in the storage area corresponding to the luminance level indicated by the pixel data DD. The stored number is incremented by “1”. Here, every time the above processing on the pixel data DD for one frame (or one field) is completed, the luminance histogram processing circuit 406 reads out the values stored in the respective storage areas, that is, the frequencies, and displays them. and it supplies the cumulative operation circuit 407 as brightness histogram data H _id representing an association with the luminance level "0" to "255", respectively as shown in 10.

The cumulative calculation circuit 407 sets the frequency for each of the luminance levels “0” to “255” represented by the luminance histogram data H _{id in} order from the one corresponding to the low luminance (or the one corresponding to the high luminance). Cumulative addition. Here, the cumulative calculation circuit 407 sets the cumulative addition result obtained each time the frequency corresponding to one luminance level is cumulatively added to the cumulative frequency corresponding to each of the luminance levels “1” to “255”. For example, the accumulating circuit 407 first corresponds the result of adding the frequency at the luminance level “0” represented by the luminance histogram data H _id and the frequency at the luminance level “1” to the luminance level “1”. Cumulative frequency. Next, an addition result obtained by adding the frequency at the luminance level “2” to the cumulative frequency corresponding to the luminance level “1” is set as the cumulative frequency corresponding to the luminance level “2”. Next, an addition result obtained by adding the frequency at the luminance level “3” to the cumulative frequency corresponding to the luminance level “2” is set as the cumulative frequency corresponding to the luminance level “3”. The cumulative calculation circuit 27 subsequently calculates the cumulative frequency corresponding to each of the luminance levels “4” to “255” by sequentially executing the cumulative addition as described above. The cumulative frequency corresponding to the maximum luminance level “255” is always the total number of pixels of the PDP 10 (n · m). The cumulative calculation circuit 407 detects a substantial peak luminance from a cumulative luminance frequency series AH _id3 as shown in FIG. 11 representing a luminance-cumulative frequency curve in which each of the luminance levels “1” to “255” is associated with each cumulative frequency. This is supplied to the circuit 408 and the inflection point detection circuit 409.

The substantial peak luminance detection circuit 408 detects the luminance level corresponding to the preset cumulative frequency H _C as shown in FIG. 11 as the substantial peak luminance from the accumulated luminance frequency series AH _{id3 for} each frame, A substantial peak luminance signal PY indicating the luminance level is supplied to the luminance adjustment gain calculation circuit 410. The cumulative frequency H _C is a value of c% (90 ≦ c <100) of the maximum cumulative frequency (n · m).

The adaptive luminance calculation circuit 411 first calculates the luminance (hereinafter referred to as “screen visual luminance”) actually viewed when the viewer views the display screen of the PDP 10 based on the pixel data DD for each frame. Calculate as follows. That is, even if the average luminance of one frame image based on the input video signal VD is constant, when the peak luminance in the image is high, the image is felt brighter than when it is low. That is, the higher the peak luminance, the higher the screen visual luminance. Therefore, in order to obtain the screen visual luminance, the adaptive luminance calculation circuit 411 detects the average luminance APL and the peak luminance Y _PK for each frame (or one field) of the image based on the pixel data DD for each frame. . Next, the adaptive luminance calculation circuit 411 calculates the screen visual luminance correction value CC from the peak luminance Y _PK based on the linear function α as shown in FIG. Then, the adaptive luminance calculation circuit 411 calculates a screen visual luminance signal Y _DSP representing the screen visual luminance from the average luminance APL based on the linear function β as shown in FIG. At this time, the adaptive luminance calculation circuit 411 sets the slope of the linear function β based on the screen visual luminance correction value CC, as shown in FIG. That is, when the screen visual luminance correction value CC matches the predetermined value, the screen visual luminance signal Y _DSP is calculated based on the linear function β indicated by the solid line in FIG. Further, when the screen visual luminance correction value CC is larger than a predetermined value, the linear function β ₁ (one point) in which the slope of the linear function β (indicated by a solid line) is increased by an amount corresponding to the difference value between the two. The screen visual luminance signal Y _DSP is calculated based on (shown by a chain line). On the other hand, when the screen visual luminance correction value CC is smaller than a predetermined value, the linear function β ₃ (dashed line) in which the slope of the linear function β (shown by a solid line) is reduced by an amount corresponding to the difference between the two. The screen visual luminance signal Y _DSP is calculated based on That is, by correcting the average luminance APL for one frame according to the peak luminance Y _PK in the image, the luminance of the display screen that the viewer will see, the so-called screen visual luminance (Y _DSP ) is obtained. It is.

The adaptive luminance calculation circuit 411 is based on the ambient illuminance signal Y supplied from the illuminance sensor 2a, the viewing distance signal Le supplied from the viewing distance sensor 2, and the screen visual luminance signal Y _DSP. An adaptation luminance La that is viewed when a person looks at the display screen of the PDP 10 is calculated based on the following arithmetic expression and supplied to the correction amount setting circuit 412.

La = {Y · Le + Y _DSP (Le _(MAX) −Le)} / Le _(MAX)
Le _(MAX) : Maximum viewing distance capable of image recognition In other words, the adaptive luminance calculation circuit 411 mixes the ambient illuminance (Y) and the screen visual luminance (Y _DSP ) at a mixing ratio based on the viewing distance (Le). Thus, the luminance (La) that is actually viewed when the viewer looks at the display screen of the PDP 10 is obtained in consideration of the viewing environment (environmental illuminance, viewing distance). The adaptation luminance calculation circuit 411 supplies the adaptation luminance La to the correction amount setting circuit 412.

The correction amount setting circuit 412 converts the adaptation luminance La into a correction amount PG _COR indicating a correction amount for a luminance adjustment gain (described later) according to a predetermined conversion function CORa as shown in FIG. This is supplied to the calculation circuit 410. According to the conversion function CORa, the correction amount PG _COR increases as the adaptation luminance La increases.

The luminance adjustment gain calculation circuit 410 calculates a luminance adjustment gain signal PG corresponding to the actual peak luminance signal PY supplied from the actual peak luminance detection circuit 408 based on the gain calculation linear function F as shown in FIG. Is supplied to the luminance adjustment circuit 413. As shown in FIG. 25, the gain calculation linear function F is the lowest luminance adjustment when the peak luminance represented by the actual peak luminance signal PY is equal to the maximum luminance PY _MAX that can be expressed by this plasma display device. The gain value (for example, “1”) is obtained, and the function is such that a larger brightness adjustment gain is obtained as the actual peak brightness PY becomes lower.

Here, the brightness adjustment gain calculation circuit 410 calculates the brightness adjustment gain PG based on the gain calculation linear function F in which the negative slope increases as the correction amount indicated by the correction amount PG _COR increases. For example, the brightness adjustment gain calculation circuit 410 has a gain calculation linear function F _UP shown in FIG. 25 when the correction amount PG _COR is relatively large, and a gain calculation linear function shown in FIG. 25 when the correction amount PG _COR is small. Based on F _DN , the brightness adjustment gain PG is calculated. At this time, the correction amount PG _COR is proportional to the adaptation luminance La as shown in FIG. Therefore, the luminance adjustment gain PG increases as the actual peak luminance PY decreases, and the luminance adjustment gain PG increases as the adaptation luminance La increases.

As shown in FIG. 11, the inflection point detection circuit 409 detects the luminance level corresponding to the preset cumulative frequency H _B from the cumulative luminance frequency series AH _id3 supplied from the cumulative calculation circuit 407 as the inflection point luminance. Then, the inflection point luminance signal B indicating the luminance level is supplied to the luminance adjustment circuit 413. The cumulative frequency H _B is a value of b% (b <c) of the maximum cumulative frequency (n · m).

  When the pixel data DD represents a luminance level equal to or higher than the luminance level indicated by the inflection point luminance signal B, the luminance adjustment circuit 413 increases the luminance adjustment gain signal to the luminance level represented by the pixel data DD. Multiply the brightness adjustment gain indicated by PG. Then, the luminance adjustment circuit 413 generates luminance correction pixel data PD representing the luminance level obtained by such multiplication, and supplies this to the SF data generation circuit 3 as shown in FIG. When the pixel data DD represents a luminance level lower than the luminance level indicated by the inflection point luminance signal B, the luminance adjustment circuit 413 generates SF data using the pixel data DD as it is as the luminance correction pixel data PD. Supply to circuit 3.

According to the luminance correction circuit 400 having the above configuration, the peak ACL processing similar to the luminance correction circuit 200 shown in FIG. 9 is performed on the pixel data DD according to the adaptation luminance La. That is, as shown in FIG. 25, as the correction amount PG _COR is increased, that is, as the adaptation luminance La is higher, pixel data DD representing a luminance level equal to or higher than a predetermined luminance level (the luminance level indicated by the inflection point luminance signal B). The luminance adjustment gain PG with respect to is increased. Therefore, in a situation where the adaptation brightness is high, in which the display image is visually perceived as dark overall, brightness adjustment is automatically performed to brighten the entire display image, while the adaptation brightness is low, such that the display image feels dazzling Then, the brightness adjustment that should darken the entire display image is automatically performed. This makes it possible to provide a display image that is always easy to see, regardless of the adaptation brightness of the viewer.

Here, the luminance correction circuit 400 shown in FIG. 22 does not directly detect the maximum luminance from the input video signal for one frame when detecting the peak luminance for each frame so as to perform the peak ACL processing. As shown in FIG. 11, a luminance level PY corresponding to a predetermined cumulative frequency H _C is detected as a substantial peak luminance from the cumulative luminance frequency series AH _id3 . That is, the luminance level corresponding to the cumulative frequency H _C that is smaller than the maximum cumulative frequency (n · m) by a predetermined value is detected as the peak luminance from the cumulative luminance frequency series AH _id3 calculated for each frame. It is. This is to prevent the following unnatural display state that occurs when the peak luminance is detected directly from the input video signal for one frame. That is, when a high brightness banner (bunner) such as subtitles or breaking news suddenly appears in the image frame, if the peak brightness is detected directly from the input video signal for one frame, the brightness level in this banner area Will be detected as the peak luminance. Therefore, when luminance adjustment is performed on each pixel data DD for one frame with the luminance adjustment gain (PG) corresponding to the luminance level in the banner area, an image with little luminance change with time change is displayed. Even so, a so-called screen flickering occurs in which the brightness level of the entire screen suddenly changes at the start and end of the banner display.

On the other hand, in the luminance correction circuit 400 shown in FIG. 22, the luminance level corresponding to the cumulative frequency H _C that is smaller than the maximum cumulative frequency by a predetermined value from the cumulative luminance frequency series AH _id3 is set as a substantial peak luminance. Yes. That is, a luminance level slightly smaller than the actual peak luminance in the input video signal (pixel data DD) for one frame is a substantial peak luminance, which is relatively low such as a banner area where subtitles, breaking news, etc. are displayed. The brightness level in a narrow area is not a target for peak brightness detection. Therefore, even when such a banner region suddenly appears in the screen, the peak ACL processing can be performed without causing the screen to flicker.

In the peak ACL processing by the brightness correction circuit 400, brightness adjustment is performed on each pixel data DD so that the actual peak brightness PY for each frame based on the input video signal becomes the maximum brightness that can be expressed in the plasma display device. Processing is done. Therefore, the luminance levels included between the real peak luminance level PY and the maximum luminance level “255” as shown in FIG. 11 are all uniformly expressed as the maximum luminance that can be expressed in the plasma display device. As a result, the image area displayed within the range from the substantial peak luminance level PY to the maximum luminance level “255” is displayed as “whiteout”. This “whiteout” is more easily recognized by the viewer as the adaptation luminance La is lower, and causes a sense of incongruity. Therefore, in the luminance correction circuit 400 shown in FIG. 22, as the correction amount PG _COR is smaller, that is, the adaptation luminance La is smaller, the “whiteout” is reduced by decreasing the luminance adjustment gain PG as shown in FIG. Is suppressed. On the other hand, as the adaptation luminance La increases, this “whiteout” is less likely to be recognized. Conversely, the luminance adjustment gain PG is increased to increase the contrast.

  Further, in the luminance correction circuit 400, a luminance level equal to or higher than a predetermined inflection point luminance (B) as shown in FIG. 11 in the input video signal (pixel data DD) is targeted for peak ACL processing. Therefore, since the luminance level indicated by the input video signal is maintained as it is at the intermediate luminance level where the frequency increases, the contrast is maintained while maintaining the gradation reproducibility as compared with the case where all the luminance levels are subjected to the peak ACL processing. It is possible to enhance the feeling.

  Further, since the peak ACL is executed only for a part of high luminance levels equal to or higher than the predetermined inflection point luminance (B), compared to the case where the entire luminance level is the target of the peak ACL processing, It is possible to enhance the contrast while suppressing an increase in power consumption accompanying the increase in luminance.

  In the luminance adjustment circuit 400 shown in FIG. 22, the pixel data DD having the luminance level equal to or higher than the predetermined inflection point luminance (B) is set as the target of the peak ACL processing as described above. An ACL processing target may also be used. Further, in performing the peak ACL processing for all luminance levels as described above, the luminance adjustment circuit 413 uses the luminance adjustment gain PG calculated based on the gain calculation linear function F as shown in FIG. The brightness correction pixel data PD may be generated by adding the values instead of multiplying the DD.

It is a figure which shows schematic structure of the plasma display apparatus based on this invention. It is a figure which shows an example of the installation location of the viewing distance sensor 2 and the illumination intensity sensor 2a. It is a figure which shows an example of the light emission drive sequence at the time of driving PDP10. It is a figure which shows an example of an internal structure of the brightness correction circuit 200 shown by FIG. It is a figure which shows an example of the frequency for each luminance level represented by the luminance histogram data _Hid1 produced _| generated in the luminance histogram processing circuit 21. FIG. It is a figure showing the operation _{| movement of the} accumulation brightness frequency series _{AHid1 produced |} generated by the accumulation calculating circuit 22, and the accumulation flattening processing circuit 23. FIG. It is a figure which shows an example of the conversion function CH for calculating | requiring the flattening amount His corresponding to viewing distance Le. 6 is a diagram for explaining the operation of the flattening processing circuit 23. FIG. 6 is a diagram illustrating another example of the internal configuration of the luminance correction circuit 200. FIG. It is a diagram illustrating an example of frequency of each luminance level for each represented by the luminance histogram data H _id generated in the luminance histogram processing circuit (26,36,406). It is a figure which shows an example of the accumulation brightness frequency series AH _id3 produced | generated by the accumulation calculating circuit (27,407). It is a figure which shows an example of the conversion function COR for calculating | requiring the correction amount PG _COR corresponding to viewing distance Le. 6 is a diagram for explaining the operation of a luminance adjustment gain calculation circuit 30. FIG. 6 is a diagram illustrating another example of the internal configuration of the luminance correction circuit 200. FIG. It is a figure which shows an example of the accumulation brightness frequency series AH _{id4 produced |} generated by the accumulation calculating circuit 37. FIG. Is a diagram illustrating an example of a conversion function COR _K for obtaining a correction amount KG _COR corresponding to the viewing distance Le. 7 is a diagram for explaining the operation of a luminance adjustment coefficient calculation circuit 40. FIG. It is a figure which shows another example of schematic structure of a plasma display apparatus. It is a figure which shows the internal structure of the brightness correction circuit 300 in the plasma display apparatus shown by FIG. It is a figure which shows an example of the conversion function COL for calculating | requiring the suppression coefficient K corresponding to viewing distance Le. It is a figure which shows another example of schematic structure of a plasma display apparatus. It is a figure which shows the internal structure of the brightness correction circuit 400 in the plasma display apparatus shown by FIG. FIG. 6 is a diagram for explaining the operation of an adaptive luminance calculation circuit 411. It is a figure which shows an example of the conversion function CORa for calculating | requiring the correction amount PG _COR corresponding to the adaptation brightness | luminance La. 6 is a diagram for explaining the operation of a luminance adjustment gain calculation circuit 410. FIG.

Explanation of main part codes

2 Viewing distance sensor 2a Illuminance sensor 10 PDP
200,300,400 Brightness correction circuit

Claims (14)

A display panel driving method for performing gradation display by selectively causing each pixel of a display panel to emit light according to an input video signal,
Generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution in frame units represented by the input video signal;
Generating cumulative luminance frequency data representing the cumulative frequency for each luminance level by accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance levels;
Measure the distance between the display panel and the viewer in front of it as the viewing distance,
Generating corrected cumulative luminance frequency data by correcting the cumulative frequency for each luminance level represented by the cumulative luminance frequency data according to the viewing distance;
A display panel driving method comprising adjusting a luminance level for each pixel in the input video signal based on the corrected cumulative luminance frequency data. The cumulative frequency series for each luminance level represented by the cumulative luminance frequency data is an amount corresponding to the viewing distance,
Cumulative frequency = [(P _H −P _L ) / LM _MAX ] · LM + P _L
P _H : highest cumulative frequency represented by the cumulative luminance frequency data
P _L : the lowest cumulative frequency represented by the cumulative luminance frequency data
LM _MAX : Maximum luminance level in the cumulative luminance frequency data
LM: Luminance level (0 to LM _MAX )
The corrected accumulated luminance frequency data is generated by performing correction on the accumulated luminance frequency data to be approximated to a linear linear accumulated luminance frequency series in which the accumulated frequency for each luminance level is represented by 2. A method for driving a display panel according to 1.   When the cumulative frequency for each luminance level represented by the cumulative luminance frequency data is higher than the cumulative frequency for each luminance level represented by the primary linear cumulative luminance frequency series, the cumulative luminance frequency data The cumulative frequency for each luminance level represented by the cumulative luminance frequency data is represented by the primary linear cumulative luminance frequency series, while performing correction to reduce the cumulative frequency for each luminance level represented by 3. The display according to claim 2, wherein when the cumulative frequency is lower than the cumulative frequency for each luminance level, correction is performed to increase the cumulative frequency for each luminance level represented by the cumulative luminance frequency data. Panel drive method. A display panel driving method for performing gradation display by selectively causing each pixel of a display panel to emit light according to an input video signal,
Generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution in frame units represented by the input video signal;
Generating cumulative luminance frequency data representing the cumulative frequency for each luminance level by accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance levels;
Measure the distance between the display panel and the viewer in front of it as the viewing distance,
A predetermined first cumulative frequency that is smaller than the maximum cumulative frequency among each of the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data and has a value of 90% or more of the maximum cumulative frequency. The brightness level corresponding to is detected as the actual peak brightness level,
Calculating a correction coefficient based on the substantial peak luminance level and the viewing distance;
A display panel driving method, comprising: adjusting a luminance level of each pixel represented by the input video signal based on the correction coefficient.   The display panel driving method according to claim 4, wherein the correction coefficient that prompts the adjustment to increase the luminance level for each pixel is calculated as the viewing distance increases. A luminance level corresponding to a predetermined second cumulative frequency smaller than the first cumulative frequency is detected as an inflection point luminance level in each of the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data. ,
The luminance level based on the correction coefficient is adjusted only for a luminance level equal to or higher than the inflection point luminance level among luminance levels for each pixel represented by the input video signal. 5. A method for driving a display panel according to 4. A display panel driving method for performing gradation display by selectively causing each pixel of a display panel to emit light according to an input video signal,
Generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution in frame units represented by the input video signal;
Generating cumulative luminance frequency data representing the cumulative frequency for each luminance level by accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance levels;
Measure the distance between the display panel and the viewer in front of it as the viewing distance,
A predetermined first cumulative frequency having a value greater than the lowest cumulative frequency and not more than 10 percent of the maximum cumulative frequency among each of the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data. The corresponding brightness level is detected as the actual bottom brightness level,
Calculating a correction coefficient based on the substantial bottom luminance level and the viewing distance;
A display panel driving method, comprising: adjusting a luminance level of each pixel represented by the input video signal based on the correction coefficient.   8. The method of driving a display panel according to claim 7, wherein the correction coefficient that prompts the adjustment for lowering the luminance level of each pixel is calculated as the viewing distance increases. A brightness level corresponding to a predetermined second cumulative frequency larger than the first cumulative frequency is detected as an inflection point luminance level among the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data. ,
The luminance level based on the correction coefficient is adjusted only for a luminance level equal to or lower than the inflection point luminance level among the luminance levels for each pixel represented by the input video signal. 8. A method for driving a display panel according to 7. A display panel driving method for performing gradation display by selectively causing each pixel arranged in each display line of a display panel to emit light according to an input video signal,
A load amount at the time of light emission by each of the pixels is calculated for each display line based on the input video signal,
Measure the distance between the display panel and the viewer in front of it as the viewing distance,
Calculating a correction coefficient based on the load amount and the viewing distance for each display line;
A display panel driving method, comprising: adjusting a luminance level of each pixel represented by the input video signal based on the correction coefficient.   The display panel driving method according to claim 10, wherein the correction coefficient that prompts the adjustment to lower the luminance level of each pixel is calculated as the viewing distance becomes shorter. A display panel driving method for performing gradation display by selectively causing each pixel of a display panel to emit light according to an input video signal,
Generating luminance frequency data representing the frequency of pixels for each luminance level in the luminance distribution in frame units represented by the input video signal;
Generating cumulative luminance frequency data representing the cumulative frequency for each luminance level by accumulating the frequencies for each luminance level represented by the luminance frequency data in order of luminance levels;
Measure the distance between the display panel and the viewer in front of it as the viewing distance and detect the brightness of the space where the display panel is installed as the environmental illuminance,
A predetermined first cumulative frequency that is smaller than the maximum cumulative frequency among each of the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data and has a value of 90% or more of the maximum cumulative frequency. The brightness level corresponding to is detected as the actual peak brightness level,
Obtaining a screen visual brightness that is viewed from the display screen of the display panel based on an average brightness for each frame of the image indicated by the input video signal;
Obtaining the adaptation luminance that is viewed in the viewing environment by mixing the ambient illuminance and the screen visual luminance at a mixing ratio based on the viewing distance,
Calculating a correction coefficient based on the substantial peak luminance level and the adaptation luminance;
A display panel driving method, comprising: adjusting a luminance level of each pixel represented by the input video signal based on the correction coefficient.   13. The display panel driving method according to claim 12, wherein the correction coefficient that promotes the adjustment to increase the luminance level of each pixel as the adaptation luminance increases is calculated. A brightness level corresponding to a predetermined second cumulative frequency larger than the first cumulative frequency is detected as an inflection point luminance level among the cumulative frequencies for each luminance level represented by the cumulative luminance frequency data. ,
The luminance level based on the correction coefficient is adjusted only for a luminance level equal to or lower than the inflection point luminance level among the luminance levels for each pixel represented by the input video signal. 13. A method for driving a display panel according to 12.

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