JP2014109710A - Method for manufacturing display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress luminance reduction without damaging display quality during white balance adjustment of a display device.SOLUTION: A white balance adjustment device 50 includes a white balance adjustment step for performing white balance adjustment by adjusting respective gradations of RGB three primary colors for a prescribed input video signal displayed in a display device (S1), a first determination step for determining whether screen luminance after the white balance adjustment is less than reference luminance (S3), a second determination step for determining whether the gradation of one color among the RGB three primary colors is fixed in the white balance adjustment in the case that the screen luminance after the white balance adjustment is determined to be less than the reference luminance (S4), and a white balance readjustment step for readjusting the gradation of at least one color between remaining two colors high in the case that the gradation of one color among the RGB three primary colors is fixed (S5).

Description

  The present invention relates to a display device manufacturing method including a step of adjusting white balance of a display device.

  2. Description of the Related Art Conventionally, in a production line of a liquid crystal television that is one of thin display devices, white balance adjustment is performed to correct chromaticity variations between liquid crystal panels. In this white balance adjustment, a reference image (test pattern) composed of an R image signal, a G image signal, and a B image signal is input, and the chromaticity on the screen of the reference image is measured by a predetermined measuring instrument, and the measured color is measured. Adjustment values for adjusting each value of R, G, and B are set so that the degree falls within the allowable range.

  Regarding the technique for adjusting the above white balance, for example, in Patent Document 1, the ratio of R, G, B when adjusting to the target white balance is calculated, the target luminance rate characteristic is changed, and the adjustment is performed. A white balance control unit that adjusts the white balance according to the luminance rate characteristic, a gamma correction value recording unit that records R, G, and B gamma correction values generated by the white balance control unit, a target white balance, and a target There is described a liquid crystal display device including a target value recording device section for recording the luminance rate characteristics of the above. Thereby, the speed of white balance adjustment can be increased.

JP 2009-225440 A

  However, for example, when white balance adjustment is performed in an 8-bit system, the maximum gradation of white cannot be increased to 255 gradations or more, so adjustment is performed by lowering the R, G, and B gradations. Absent. Therefore, luminance is always reduced when white balance adjustment is performed. That is, there is a problem that as the difference between the target chromaticity of the white balance and the chromaticity before adjustment is larger, the amount of gradation reduction at the time of adjustment is larger and the luminance is also lowered.

  On the other hand, the technique described in Patent Document 1 is designed to reduce the time required for white balance adjustment by measuring chromaticity only once at the beginning, thereby reducing the brightness caused by white balance adjustment. It is not a suppression, and the above problems cannot be solved.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a display device that can suppress a decrease in luminance without degrading display quality when white balance is adjusted. To do.

  In order to solve the above problems, a first technical means of the present invention is a method for manufacturing a display device including a step of adjusting a white balance of the display device, wherein the step is a predetermined display displayed on the display device. A white balance adjustment step for adjusting white balance by adjusting the gradation of each of the three primary colors of RGB for the input video signal, and whether the screen brightness of the display device after the white balance adjustment is less than a reference brightness In the first determination step of determining whether the screen brightness of the display device after the white balance adjustment is less than a reference brightness, the gradation of any one of the three primary colors of RGB in the white balance adjustment step A second determination step for determining whether or not the color is fixed, and the gradation of any one of the RGB three primary colors is fixed If it is determined that is obtained by comprising the white balance readjustment step of readjusting increase at least one color tone of the remaining two colors.

  According to a second technical means, in the first technical means, the white balance readjustment step re-adjusts the G gradation and the B gradation when the R gradation is fixed among the three primary colors of RGB. In addition, when the B gradation is fixed among the three primary colors of RGB, the G gradation and the R gradation are readjusted to be high.

  According to a third technical means, in the second technical means, the white balance readjustment step includes adjusting the G gradation and the B gradation, or the G gradation and the R gradation with a predetermined adjustment rate. Alternatively, the adjustment amount is increased.

  According to a fourth technical means, in the second technical means, the white balance readjustment step calculates a gradation when the screen luminance of the display device becomes the reference luminance with respect to the G gradation, The calculated gradation is used as the G gradation after the readjustment, and the B gradation or the R gradation is increased by an adjustment rate or adjustment amount determined from the G gradation before and after the readjustment. It is a feature.

  According to a fifth technical means, in any one of the first to fourth technical means, the white balance readjustment step is such that the screen chromaticity of the display device after the white balance readjustment falls within an allowable range. In addition, the adjustment rate or the adjustment amount when the gradation of at least one of the remaining two colors is readjusted is limited.

  According to the present invention, the gradation lowered by the normal white balance adjustment can be readjusted to a certain extent, so that a decrease in luminance can be suppressed without impairing display quality during white balance adjustment.

It is a block diagram which shows the structural example of the display apparatus and white balance adjustment apparatus which concern on this invention. It is a figure for demonstrating an example of the white balance adjustment method by this invention. It is a flowchart for demonstrating an example of the manufacturing method of the display apparatus by this invention. It is a flowchart for demonstrating an example of the specific process in step S4, S5 of FIG. It is a figure which shows the area | region of the white vicinity on xy chromaticity diagram (CIE chromaticity diagram).

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments according to a method for manufacturing a display device according to the invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a configuration example of a display device and a white balance adjustment device according to the present invention, in which 10 denotes a display device and 50 denotes a white balance adjustment device. The display device 10 can be exemplified as a television receiver, for example, and will be described as the television receiver 10 below. The television receiver 10 receives video / audio data transmitted by terrestrial digital broadcasting and video / audio data transmitted by satellite broadcasting. In order to receive each video / audio data, a digital terrestrial broadcasting antenna 32 and a satellite broadcasting antenna 33 are provided outside the television receiver 10.

  Video / audio data transmitted by terrestrial digital broadcasting is supplied from the terrestrial digital broadcasting antenna 32 to the terrestrial digital broadcasting tuner 11. The terrestrial digital broadcast tuner 11 selects a channel designated by the user from a plurality of channels in the terrestrial digital broadcast, and supplies video / audio data of the channel to the selector 14.

  Video / audio data transmitted by satellite broadcasting is supplied from the satellite broadcasting antenna 33 to the satellite broadcasting tuner 12. The satellite broadcast tuner 12 selects a channel designated by the user from a plurality of channels in the satellite broadcast, and supplies video / audio data of the channel to the selector 14.

  The television receiver 10 may further include an external input terminal 13. The external input terminal 13 is an interface for connecting an external device such as an HD (Hard Disk) recorder and a BD (Blu-ray Disk) to the television receiver 10. The interface is one in which the television receiver 10 receives video / audio data from the external device, and conforms to a standard capable of connecting the television receiver 10 and the external device. It is. Examples of such interface standards include HDMI and HDV (IEEE 1394). When an external device is connected to the television receiver 10, video / audio data recorded in the external device is supplied to the selector 14 via the external input terminal 13.

  The user can select a video / audio data supply source to be viewed via the remote control 31 or an operation panel (not shown). An operation signal output from the remote controller 31 when operated by the user is supplied to the control unit 22 via the infrared light receiving unit 21. The control unit 22 controls the selector 14 based on the operation signal. For example, when the user selects viewing of the terrestrial digital broadcast using the remote controller 31, the remote controller 31 outputs an operation signal corresponding to the operation. Upon receiving the operation signal, the control unit 22 controls the selector 14 so that the selector 14 selects the terrestrial digital broadcast tuner 11 as an input source of video / audio data.

  The selector 14 supplies the audio / video data from the terrestrial digital broadcast tuner 11 selected as the input source to the decoding unit 15. The decoding unit 15 first separates the supplied video / audio data into video data, audio data, and character information data. The data for character information includes data for EPG and OSD display. Next, the decoding unit 15 decodes the video data and the audio data. The audio data decoded by the decoding unit 15 is output as audio from the speaker 17 via the audio signal processing unit 16.

  On the other hand, the video data decoded by the decoding unit 15 is supplied to the video signal processing unit 18. The video signal processing unit 18 appropriately performs A / D conversion processing, YI separation processing, IP conversion processing, matrix conversion processing, and other video processing on the supplied video data as necessary. As a result, the video signal processing unit 18 supplies the RGB signal converted from the video data to the image quality adjustment unit 19.

  The image quality adjustment unit 19 adjusts the white balance (hereinafter also simply referred to as WB) by adjusting the gains of the RGB color signals supplied from the video signal processing unit 18. The image quality adjustment unit 19 may also be configured to execute gamma correction processing. The image quality adjustment unit 19 refers to the WB adjustment value when performing WB adjustment on the supplied RGB signal. The adjustment value of WB is stored in the nonvolatile memory 23, for example.

  The WB adjustment value defines the gain of each of the R, G, and B signals according to the gradation of the RGB signal supplied to the image quality adjustment unit 19. The image quality adjustment unit 19 refers to, for example, a look-up table (LUT) as a correspondence between each gradation of the supplied RGB signal and the gain of each R, G, B signal. Hereinafter, this LUT is referred to as a WB adjustment LUT. The location where the WB adjustment LUT is stored is not limited to the memory 23, and the image quality adjustment unit 19 may include a unique nonvolatile memory.

  The RGB signal whose WB has been adjusted by the image quality adjustment unit 19 is supplied to the LCD module 20, and the LCD module 20 displays an image corresponding to the RGB signal whose WB has been adjusted.

  Before each television receiver 10 is shipped from the manufacturing factory, the WB is adjusted using the white balance adjustment method according to the embodiment of the present invention. That is, the white balance adjustment method is executed as one of the manufacturing processes of the television receiver 10. By adjusting the WB, the adjustment value of the WB is stored in the nonvolatile memory 23 as the WB adjustment LUT. For example, when the television receiver 10 reaches the user, the user may want to adjust the WB in order to obtain a desired color. For this reason, the WB of the television receiver 10 may be configured to be adjustable by the user via the remote controller 31 or the operation panel. At this time, the WB adjustment value customized by the user may be stored in the nonvolatile memory 23 as a separate WB adjustment LUT.

  The television receiver 10 includes an LCD module 20 as display means for displaying video. The LCD module 20 includes a liquid crystal panel and a backlight. The liquid crystal panel drives the liquid crystal included in each sub-pixel according to the RGB signals supplied from the image quality adjustment unit 19. Thus, the luminance of the color displayed by each sub-pixel is determined, and as a result, an image is displayed on the LCD module 20. As the backlight, a cold cathode fluorescent lamp (CCFL) or an LED can be used. Moreover, it can also be set as a backlight by using CCFL and LED together.

  Next, a configuration example of the white balance adjustment device 50 used when adjusting the WB of the television receiver 10 will be described below with reference to FIG. The white balance adjustment device 50 includes a light detection unit 51, a control unit 52, a memory 53, and an output unit 54.

  As the light detection unit 51, a device generally called a color meter can be used. This color meter is roughly classified into a spectroscopic type and a stimulus value direct reading type based on the measurement principle. The spectroscopic colorimeter can measure the chromaticity point with high accuracy, but has the disadvantage that the time required for the measurement is long. On the other hand, the stimulus value direct-reading type colorimeter is inferior to the spectroscopic method in terms of accuracy, but has an advantage that the chromaticity point can be measured in a short time. In order to improve the manufacturing efficiency of the television receiver 10, it is preferable to use a stimulus value direct-reading color meter as the light detection unit 51.

  The light detection unit 51 is disposed at a position facing a predetermined region in the LCD module 20. The light detection unit 51 detects the light emitted from the LCD module 20 and supplies light intensity at predetermined wavelengths R, G, and B to the control unit 52 as a signal.

  The controller 52 calculates R, G, and B tristimulus values (X, Y, and Z) from the light intensities of the R, G, and B wavelengths. Furthermore, the control unit 52 calculates chromaticity points (xi, yi) on the xy chromaticity diagram based on the calculated tristimulus values (X, Y, Z). The chromaticity point (xi, yi) is a parameter that reflects the hue and saturation of light emitted from the LCD module 20.

  In addition, in order for the control unit 52 to calculate the chromaticity point (xi, yi) of the LCD module 20, the predetermined region measured by the light detection unit 51 may be one region or a plurality of regions. There may be. For example, the chromaticity point (xi, yi) of the area located at the center of the LCD module 20 may be used as the chromaticity point (xi, yi) of the LCD module 20. As another method, for example, the light detection unit 51 may measure a total of five areas of the center and four corners of the LCD module 20. The control unit 52 may use the chromaticity point obtained by averaging the chromaticity points in the five regions as the chromaticity point (xi, yi) of the LCD module 20.

  Then, the control unit 52 sets the R, G, and B gains so that the chromaticity point (xi, yi) on the xy chromaticity diagram calculated above becomes the target chromaticity point (x0, y0). Determine an adjustment value for adjustment. As the target chromaticity point (x0, y0), for example, a chromaticity point with a color temperature of 12000K can be considered. The adjustment value determined by the control unit 52 is supplied to the output unit 54, and the output unit 54 supplies the adjustment value supplied from the control unit 52 to the television receiver 10 via the adjustment terminal 24. The adjustment value is stored in the WB adjustment LUT in the memory 23.

  The image quality adjustment unit 19 of the television receiver 10 adjusts the R, G, and B gains for the RGB signals based on the adjustment values stored in the WB adjustment LUT of the memory 23. In this way, normal WB adjustment is performed on the television receiver 10, but the maximum gradation of white cannot be raised to 255 gradations or more, so the gradation of each RGB color is lowered. Adjusted in direction. For this reason, there is a problem that the luminance is always lowered by the WB adjustment.

  On the other hand, a main object of the present invention is to suppress a decrease in luminance without impairing display quality during white balance adjustment. As a configuration for this, the white balance adjustment device 50 adjusts the gradation of each of the RGB three primary colors with respect to a predetermined input video signal (for example, a WB adjustment pattern signal) displayed on the television receiver 10. Means for performing WB adjustment, means for determining whether or not the screen brightness after WB adjustment is less than the reference brightness, and if the screen brightness after WB adjustment is determined to be less than the reference brightness, RGB3 is determined by the WB adjustment. If it is determined that the gradation of any one of the primary colors is fixed and the gradation of any one of the RGB three primary colors is fixed, of the remaining two colors Means for readjusting the gradation of at least one color high. Each of these means is realized as one function of the control unit 52. Specifically, a program for executing each of the above means is stored in the memory 53, and the controller 52 reads and executes this program when executing the white balance adjustment method according to the present invention.

  FIG. 2 is a diagram for explaining an example of a white balance adjustment method according to the present invention. As described above, this white balance adjustment method is executed as one of the manufacturing steps of the television receiver 10. FIG. 2A shows input / output characteristics without adjustment. FIG. 2B shows the input / output characteristics during normal adjustment, and FIG. 2C shows the input / output characteristics during readjustment. In the figure, the horizontal axis indicates input, and the vertical axis indicates output. First, in order to perform normal WB adjustment, the television receiver 10 inputs a WB adjustment pattern signal (that is, a white image pattern) in which the maximum gradation of the RGB three primary colors is (255, 255, 255), This is displayed on the screen. The input / output characteristics at this time are in an unadjusted state, and as shown in FIG.

Next, the white balance adjusting device 50 measures the screen brightness (cd / m ² ) and the screen chromaticity (xi, yi) with respect to the non-adjusted screen displayed on the television receiver 10, and measures the measured screen. For example, adjustment values for adjusting each gradation of the RGB three primary colors are determined so that the chromaticity (xi, yi) becomes, for example, the target chromaticity (x0, y0) of the color temperature 12000K. The determined adjustment value is stored in the memory 53 and also in the memory 23 of the television receiver 10.

  The image quality adjustment unit 19 of the television receiver 10 adjusts the gradation of each RGB signal based on the adjustment value stored in the memory 23 as shown in FIG. 2B, for example. In other words, the R gradation is fixed, and the G gradation and the B gradation are adjusted in a decreasing direction. This is a normal WB adjustment (hereinafter simply referred to as a normal WB adjustment), whereby the chromaticity on the screen of the television receiver 10 is adjusted to the target chromaticity.

Next, the white balance adjustment device 50 measures the screen luminance after the normal WB adjustment by the light detection unit 51 and the control unit 52, and determines whether the screen luminance after the normal WB adjustment is less than the reference luminance. The reference luminance is stored in advance in the memory 53 as 450 cd / m ² , for example. In this example, the screen brightness Y after the normal WB adjustment is 428.6 cd / m ^2, which is about 22 cd / m ² short of the reference brightness (450 cd / m ² ). Therefore, the screen brightness Y is less than the reference brightness. Determined.

Here, the gamma characteristic of the LCD module 20 is 2.2, 8-bit system (0 to 255), the maximum luminance of the primary colors RGB is Y _R , Y _G , Y _B respectively, and the gradation after normal WB adjustment is (Ri) , Gi, Bi), when the screen brightness after normal WB adjustment is Y (cd / m ² ), the following equation (1) is established.
Y = (Y _R × Ri ^2.2 + Y _G × Gi ^2.2 + Y _B × Bi ^2.2 ) / 255 ^2.2・ ・ ・ Formula (1)

For example, if the screen brightness (white brightness) at the time of no adjustment is 500 cd / m ² and the RGB primary color brightness ratios are 0.2, 0.7, and 0.1, respectively, the maximum brightness (Y _R , Y _G , Y _B ) is 100, 350, and 50 cd / m ² , respectively. When the gradation (Ri, Gi, Bi) after the normal WB adjustment is 255, 235, and 220, when these values are substituted into the above equation (1), the screen brightness Y after the normal WB adjustment is 428. .6 cd / m ² . The gradation (Ri, Gi, Bi) after the normal WB adjustment is obtained from the maximum gradation (255, 255, 55) in the non-adjustment state and the adjustment value (memory 53) used for the normal WB adjustment. be able to.

As described above, the control unit 52 compares the screen brightness Y after the normal WB adjustment with the reference brightness (450 cd / m ² here) stored in advance, and determines that the screen brightness Y is equal to or higher than the reference brightness. In this case, no further WB adjustment is performed, and the process is terminated. Therefore, the adjustment value by the normal WB adjustment is set as it is in the television receiver 10.

  Further, when the control unit 52 determines that the screen luminance Y is less than the reference luminance, the control unit 52 determines whether the gradation of any one of the RGB three primary colors is fixed. This determination can be made based on the adjustment value stored in the memory 53. That is, it can be determined that the gradation is fixed for the color having the adjustment value of 0 among the adjustment values of the RGB three primary colors. When the control unit 52 determines that the gradation of any one of the three RGB primary colors is fixed, an adjustment value for readjusting the gradation of at least one of the remaining two colors to be high is set. decide. In the example of FIG. 2C, since the R gradation is fixed, the remaining two colors G gradation and B gradation are readjusted. The adjustment value used for this readjustment is output from the output unit 54 to the television receiver 10 and stored in the memory 23 of the television receiver 10. In other words, the adjustment value used for the normal WB adjustment is already stored in the memory 23, but separately, the adjustment value used for the readjustment after the normal WB adjustment is stored.

  From the above, since the gradation lowered by the normal WB adjustment can be raised to some extent, a decrease in luminance can be suppressed. Since the G gradation contributes most to the improvement in luminance, it is desirable to raise at least the G gradation and fix the R gradation or the B gradation. That is, when the R gradation is fixed among the RGB three primary colors, the G gradation and the B gradation are readjusted to be high, and when the B gradation is fixed among the RGB three primary colors, the G gradation and R are adjusted. It is desirable to readjust the gradation to a higher level.

  Specifically, the G gradation and the B gradation, or the G gradation and the R gradation are increased by a predetermined adjustment rate or adjustment amount. In the case of the adjustment rate, a gradation obtained by multiplying the gradation before readjustment by 1.1, for example, is used as the gradation after readjustment. In the case of the adjustment amount, for example, 30 is added to the gradation before readjustment, and the gradation after readjustment is set. In this example, the gradation of the two colors is adjusted to be high. However, for example, only one of the colors such as the G gradation may be adjusted to be high.

  Here, if the tone is readjusted based on a fixed adjustment rate or adjustment amount as described above, the chromaticity after the readjustment may deviate from the target chromaticity because it approaches the no adjustment state, which may impair the display quality. There is. Therefore, as a method of minimizing the chromaticity deviation, the gradation may be raised by an amount necessary to reach the reference luminance. That is, the control unit 52 calculates a gradation when the screen luminance of the television receiver 10 becomes the reference luminance with respect to the G gradation, and uses the calculated gradation as the G gradation after readjustment. At the same time, the B gradation or R gradation is increased by an adjustment rate or adjustment amount determined from the G gradation before and after readjustment.

The case where the R gradation is fixed during WB adjustment and the G gradation and the B gradation are readjusted will be described as an example. Assuming that the R gradation, G gradation, and B gradation after readjustment are Ri ′, Gi ′, Bi ′, and the brightness after readjustment is Y ′, the following expression (2) is obtained from the above expression (1). ) Holds.
Y ′ = (Y _R × Ri ′ ^2.2 + Y _G × Gi ′ ^2.2 + Y _B × Bi ′ ^2.2 ) / 255 ^2.2・ ・ ・ Formula (2)

Here, since the R gradation Ri ′ after readjustment is fixed, Ri ′ = Ri. Further, when the B gradation Bi ′ after readjustment is Bi × Gi ′ / Gi based on the ratio of the G gradation, the above equation (2) is
Y ′ = (Y _R × Ri ′ ^2.2 + Y _G × Gi ′ ^2.2 + Y _B × (Bi × Gi ′ / Gi) ^2.2 ) / 255 ^2.2 (3)
And
Accordingly, the G gradation Gi ′ necessary for realizing the readjusted luminance Y ′ can be obtained from the following equation (4).
Gi ′ = {(Y ′ × 255 ^2.2 -Y _R × Ri ^2.2 ) / (Y _G + Y _B × (Bi / Gi) ^2.2 )} ^{1 / 2.2} Formula (4)

As a calculation example, the brightness Y ′ after readjustment is 450 cd / m ² (reference brightness), the maximum brightness of primary colors RGB (Y _R , Y _G , Y _B ) is 100, 350, 50 cd / m ² , and after normal WB adjustment When the gradation (Ri, Gi, Bi) of (before readjustment) is 255, 235, 220, the G gradation Gi ′ after readjustment is obtained from the equation (4):
Gi ′ = {(450 × 255 ^2.2 -100 × 255 ^2.2 ) / (350 + 50 × (220/235) ^2.2 )} ^{1 / 2.2}
= 242
Furthermore, the B gradation Bi ′ after readjustment is
Bi ′ = 220 × 242/235
= 226
It can be asked.

From the above, the gradation (Ri ′, Gi ′, Bi ′) after readjustment is (255, 242, 226). In this case, the control unit 52 of the white balance adjustment device 50 obtains the ratio between the G gradation after the normal WB adjustment and the G gradation after the readjustment as an adjustment rate. This adjustment rate is supplied to the television receiver 10 and stored in the memory 23. The image quality adjustment unit 19 of the television receiver 10 performs RGB processing based on the adjustment rate stored in the memory 23 for the input / output characteristics (illustrated in FIG. 2B) of the RGB colors after the normal WB adjustment. The input / output characteristic of each color is adjusted, and this is set as the final input / output characteristic of each RGB color (illustrated in FIG. 2C). In this calculation example, the adjustment rate is obtained from the ratio between the G gradation after the normal WB adjustment and the G gradation after the readjustment. However, the G gradation after the normal WB adjustment and the G gradation after the readjustment are obtained. The amount of adjustment may be obtained from the difference between. Further, although the reference luminance is 450 cd / m ² , it is not limited to this.

  As described above, since the gradation lowered by the normal white balance adjustment can be readjusted to a certain extent, a decrease in luminance can be suppressed without impairing display quality at the time of white balance adjustment.

  FIG. 3 is a flowchart for explaining an example of a method for manufacturing a display device according to the present invention. This display device manufacturing method includes a step of adjusting white balance, and the step will be described below. First, the television receiver 10 displays a predetermined input video signal (for example, a WB adjustment pattern signal) on the screen of the LCD module 20, and the white balance adjustment device 50 is displayed on the television receiver 10. Normal WB adjustment is performed by adjusting the gradations of the three primary colors of RGB for the input video signal (step S1: white balance adjustment step). Then, the white balance adjustment device 50 measures the screen brightness of the television receiver 10 after the normal WB adjustment (step S2).

  Next, the white balance adjusting device 50 performs a process of determining whether or not the screen brightness measured in step S2 is less than the reference brightness (step S3: first determination step), and if the screen brightness is less than the reference brightness. If not, that is, if it is determined that the screen brightness is equal to or higher than the reference brightness (in the case of NO), no further WB adjustment is performed, and the process ends. Further, when it is determined in step S3 that the screen luminance is less than the reference luminance (in the case of YES), a process for determining whether any one of the three primary colors of RGB is fixed by the WB adjustment in step S1. It performs (step S4: 2nd determination step). If it is determined that any one of the three primary colors RGB is not fixed (NO), the process ends. If it is determined in step S4 that one of the three primary colors of RGB is fixed (in the case of YES), the gradation of at least one of the remaining two colors is adjusted again (step S5). : White balance readjustment step).

  FIG. 4 is a flowchart for explaining an example of specific processing in steps S4 and S5 of FIG. First, the white balance adjustment device 50 determines whether or not the G gradation is fixed for the RGB three primary colors after the normal WB adjustment (step S11), and when it is determined that the G gradation is fixed (YES) In this case, the gradation of at least one of the R gradation and the B gradation is readjusted (step S12). If it is determined in step S11 that the G gradation is not fixed (in the case of NO), it is determined whether or not the R gradation is fixed (step S13), and the R gradation is fixed. (YES), the gradation of at least one of the G gradation and the B gradation is readjusted (step S14).

  If the white balance adjusting device 50 determines in step S13 that the R gradation is not fixed (in the case of NO), it determines whether or not the B gradation is fixed (step S15). If it is determined that the gradation is fixed (in the case of YES), the gradation of at least one of the G gradation and the R gradation is readjusted (step S16). If it is determined in step S15 that the B gradation is not fixed (NO), the process ends.

  Here, as described above, a chromaticity shift occurs due to the readjustment of the gradation to be high. In order to suppress the chromaticity shift, the screen chromaticity after the WB readjustment is within an allowable range. Furthermore, the adjustment rate or adjustment amount when readjusting the gradation may be limited. In the case of the adjustment rate, for example, a value larger than 1.1 cannot be set. In the case of the adjustment amount, for example, a value larger than 30 cannot be set. In this way, by limiting the adjustment rate or the adjustment amount, it is possible to suppress a chromaticity shift while suppressing a decrease in luminance.

  Further, an upper limit value may be set for the gradation to be readjusted. For example, when the upper limit is 230 gradations, the gradation after readjustment is limited to 230 or less. In other words, when the gradation after readjustment is 240, for example, it exceeds 230, which is the upper limit, and is automatically limited to 230. As described above, by setting the upper limit value for the gradation, it is possible to suppress the chromaticity shift while suppressing the decrease in the luminance as described above.

  Next, a specific example of how to determine the allowable chromaticity deviation range for the color temperature of 12000K will be described with reference to FIG.

  FIG. 5 is a diagram showing a region near white on the xy chromaticity diagram (CIE chromaticity diagram). On the xy chromaticity diagram of FIG. 5, a black body locus, which is the chromaticity of black body radiation at each color temperature, a uniform color temperature line, and an equal deviation line are drawn. Each pixel included in the television receiver 10 includes, for example, red (R), green (G), and blue (B) sub-pixels. The television receiver 10 illuminates each of the R, G, and B sub-pixels with the gradation readjusted by the white balance adjustment method of the present invention, so that one of the xy chromaticity diagrams shown in FIG. The color corresponding to the chromaticity point is displayed. The chromaticity point at this time is defined as a chromaticity point (x, y) after readjustment.

  The chromaticity point (x, y) after readjustment in each television receiver 10 varies from individual to individual. An adjustment rate or an adjustment amount is calculated in advance so that the chromaticity point (x, y) after re-adjustment, which varies, falls within a predetermined target range (allowable range) on the chromaticity diagram. Set.

  The predetermined target range is set, for example, in a region H shown in FIG. The region H is a quadrilateral having two sides along each of two equal deviation lines sandwiching the black body locus and another two sides in the same color temperature line direction. As shown in FIG. 5, the region H preferably has the black body locus direction as the longitudinal direction.

  When the region H that is the predetermined target range is set to a narrow range, variations in color temperature and hue in the plurality of television receivers 10 can be suppressed. However, this also means that the time required for WB adjustment of one television receiver 10 becomes longer. That is, it means that the manufacturing efficiency in the manufacturing process of the television receiver 10 is lowered.

  On the other hand, when the area H is set to a wide range, the time required for the WB adjustment of one television receiver 10 is shortened, and the manufacturing efficiency is improved. However, if the region H is set too large, variations in color temperature and hue in each television receiver 10 will increase. That is, it has an undesirable effect on the quality of the product.

  Therefore, it is preferable to set the region H in as wide a range as possible in order to improve the manufacturing efficiency in the manufacturing process within the range of variations in color temperature and hue acceptable for the product. When setting the region H, the shape of the region H is an important factor along with the size of the region H.

  The shape and area of the region H can be determined based on the result of the subjective evaluation experiment. A typical product of the television receiver 10 is extracted from the production line, and the television receiver 10 is caused to display white of the maximum gradation among the displayable gradations. In a state where white of the maximum gradation is displayed, as normal WB adjustment processing, the gains of R, G, and B are adjusted so that the white chromaticity becomes a predetermined chromaticity point. The predetermined chromaticity point can be arbitrarily set, but is assumed to be a chromaticity point on a black body locus and having a color temperature of 12000K. The television receiver 10 adjusted to the predetermined chromaticity point is referred to as a standard television receiver 10a.

  In addition, when adjusting each gain of RGB, in order to measure the chromaticity point of the television receiver 10, it is preferable to use a spectroscopic colorimeter (radiometer). By using a spectroscopic colorimeter, it is possible to measure the chromaticity point with high accuracy.

  Next, a plurality of images in which the color temperature and the deviation from the black body locus are changed from the standard monoscopic image and skin color image are created by image processing. Using the standard television receiver 10a, the tester compares the standard monosco image and skin color image with a plurality of images having different color temperature and deviation from the black body locus.

  The tester compares the reference image with the image-processed image, and subjectively evaluates the acceptable color temperature and the range of deviation from the black body locus without feeling uncomfortable.

  From the above subjective evaluation experiment, the region H is set to a quadrilateral region surrounded by four points P1 to P4 (see FIG. 5). The points where the color temperature is 9000 K and the deviations from the black body locus are +0.005 Δuv and −0.005 Δuv are defined as P1 and P2, respectively. The points where the color temperature is 18000 K and the deviations from the black body locus are +0.005 Δuv and −0.005 Δuv are defined as P3 and P4, respectively.

  The coordinates of P1 on the xy chromaticity diagram are expressed as (xP1, yP1). Similarly, the coordinates of P2 are represented as (xP2, yP2), the coordinates of P3 are represented as (xP3, yP3), and the coordinates of P4 are represented as (xP4, yP4). The coordinates of P1 to P4 are as follows.

(XP1, yP1) = (0.2842, 0.3021)
(XP2, yP2) = (0.2896, 0.2894)
(XP3, yP3) = (0.2627, 0.2567)
(XP4, yP4) = (0.2548, 0.2651)

  Human vision recognizes the color on the black body locus as white over a wide range. For this reason, it is difficult for humans to feel uncomfortable even when viewing an image in which the color temperature has changed to some extent. Accordingly, the length of the region H in the direction of the black body locus can be set long.

  On the other hand, humans are sensitive to changes in the deviation direction with respect to the blackbody locus. When the deviation from the black body locus is shifted in the positive direction, the image appears greenish. Conversely, when the deviation is negative, the image appears reddish. Therefore, it is preferable that the length of the black body locus in the region H in the deviation direction is set short.

  Thus, the region H that is the target range is preferably a quadrilateral that is long in the black body locus direction and short in the deviation direction with respect to the black body locus, that is, a quadrilateral whose longitudinal direction is the black body locus direction. As a result, a region as wide as possible can be set as the region H within a range in which the viewer does not feel discomfort.

  When the area H set as described above is set as the allowable range, an adjustment rate or adjustment amount for adjusting the gradation is set so that the chromaticity point after the WB readjustment falls within the area H. That's fine. Specifically, the correspondence with chromaticity points is calculated in advance for several adjustment rates or adjustment amounts. Then, it is conceivable to determine whether or not each calculated chromaticity point falls within the region H, and to set the adjustment rate or adjustment amount within the range that falls within the region H.

  Up to now, the display device manufacturing method has been exemplified and described as an embodiment of the present invention. However, the present invention is not limited to a form of a white balance adjustment device that performs white balance adjustment in a display device manufacturing method or a display device. It is good also as a form of the program for making a computer perform a manufacturing method, or the form of the computer-readable recording medium which recorded this program.

  Specific examples of the recording medium include CD-ROM (-R / -RW), magneto-optical disk, HD (hard disk), DVD-ROM (-R / -RW / -RAM), and FD (flexible disk). ), A flash memory, a memory card, a memory stick, and various other ROMs and RAMs can be assumed, and a program for causing a computer to execute the manufacturing method of the display device according to the present invention described above is recorded and distributed on these recording media. This facilitates the realization of the method. Then, the recording medium as described above is mounted on an information processing apparatus such as a computer and the program is read by the information processing apparatus, or the program is stored in a storage medium provided in the information processing apparatus. By reading, the manufacturing method of the display device according to the present invention can be executed.

  As described above, the method for manufacturing a display device according to the present invention is a method for manufacturing a display device including a step of adjusting the white balance of the display device, wherein the step includes a predetermined display displayed on the display device. A white balance adjustment step for adjusting white balance by adjusting the gradations of the three primary colors of RGB for the input video signal, and whether or not the screen brightness of the display device after the white balance adjustment is less than a reference brightness When it is determined that the screen brightness of the display device after the white balance adjustment is less than a reference brightness in the first determination step, the gradation of any one of the three primary colors of RGB is determined in the white balance adjustment step. A second determination step for determining whether or not the color is fixed, and the gradation of any one of the RGB three primary colors is fixed If it is determined to be, and a white balance readjustment step of readjusting increase at least one color tone of the remaining two colors. As a result, the gradation lowered by the normal white balance adjustment can be readjusted to a certain extent, so that a decrease in luminance can be suppressed without impairing display quality during white balance adjustment.

  In the white balance readjustment step, when the R gradation of the RGB three primary colors is fixed, the G gradation and the B gradation are adjusted again, and the B gradation of the RGB three primary colors is fixed. If so, it is desirable to readjust the G gradation and the R gradation to be high. As a result, the gradation of two colors including the G gradation that contributes most to the luminance improvement among the RGB three primary colors can be adjusted to a high level. Therefore, the luminance can be reduced without degrading the display quality when adjusting the white balance. Can be suppressed.

  In the white balance readjustment step, it is preferable that the G gradation and the B gradation, or the G gradation and the R gradation are increased by a predetermined adjustment rate or adjustment amount. Thus, with a simple configuration, it is possible to suppress a decrease in luminance without degrading display quality during white balance adjustment.

  The white balance readjustment step calculates a gray level when the screen luminance of the display device becomes the reference luminance with respect to the G gray level, and the calculated gray level is calculated after the readjustment. It is desirable to set the G gradation and the B gradation or the R gradation higher by an adjustment rate or adjustment amount determined from the G gradation before and after readjustment. As a result, the gradation can be increased by an amount necessary for the reference luminance, so that a decrease in luminance can be suppressed while suppressing a chromaticity shift accompanying readjustment.

  In the white balance readjustment step, the gradation of at least one of the remaining two colors is readjusted so that the screen chromaticity of the display device after the white balance readjustment falls within an allowable range. It is desirable to limit the adjustment rate or the adjustment amount. Thereby, it is possible to suppress a decrease in luminance while suppressing a chromaticity shift accompanying readjustment.

  In the white balance readjustment step, an upper limit value is set for the gradation of at least one of the remaining two colors so that the screen chromaticity of the display device after the white balance readjustment falls within an allowable range. It is desirable to set. Thereby, similarly to the above, it is possible to suppress a decrease in luminance while suppressing a chromaticity shift accompanying readjustment.

  The white balance adjustment device according to the present invention is a white balance adjustment device that adjusts the white balance of a display device, and adjusts the gradations of the three primary colors of RGB for a predetermined input video signal displayed on the display device. Means for adjusting white balance by adjusting; means for determining whether or not the screen brightness of the display device after the white balance adjustment is less than a reference brightness; and the screen of the display device after the white balance adjustment When it is determined that the luminance is less than the reference luminance, a unit for determining whether or not the gradation of any one of the three primary colors of RGB is fixed by the white balance adjustment, and any one of the three primary colors of RGB Means for re-adjusting the gradation of at least one of the remaining two colors to a higher level when it is determined that the gradation is fixed.As a result, the gradation lowered by the normal white balance adjustment can be readjusted to a certain extent, so that a decrease in luminance can be suppressed without impairing display quality during white balance adjustment.

  The display device according to the present invention is a display device having a function of performing white balance adjustment by adjusting the gradation of each of the RGB primary colors with respect to a predetermined input video signal, and each gradation of the RGB three primary colors. The gradation of any one of the three primary colors of RGB is fixed and the floor of at least one of the remaining two colors is set so that the screen brightness of the display device after the white balance adjustment is equal to or higher than a reference brightness. The tone is readjusted higher than the gradation after the white balance adjustment.

DESCRIPTION OF SYMBOLS 10 ... Display apparatus (television receiver), 11 ... Digital terrestrial broadcast tuner, 12 ... Satellite broadcast tuner, 13 ... External input terminal, 14 ... Selector, 15 ... Decoding part, 16 ... Audio signal processing part, 17 ... Speaker, DESCRIPTION OF SYMBOLS 18 ... Video signal processing part, 19 ... Image quality adjustment part, 20 ... LCD module, 21 ... Infrared light-receiving part, 22 ... Control part, 23 ... Memory, 24 ... Adjustment terminal, 31 ... Remote control, 32 ... Terrestrial digital broadcasting antenna 33 ... Satellite broadcasting antenna, 50 ... White balance adjusting device, 51 ... Light detection unit, 52 ... Control unit, 53 ... Memory, 54 ... Output unit.

Claims (5)

A method for manufacturing a display device, comprising the step of adjusting the white balance of the display device,
The step includes a white balance adjustment step of adjusting white balance by adjusting the gradations of the three primary colors of RGB for a predetermined input video signal displayed on the display device, and the display device after the white balance adjustment. In the first determination step of determining whether or not the screen brightness of the display device is less than the reference brightness, and when the screen brightness of the display device after the white balance adjustment is determined to be less than the reference brightness, the white balance adjustment step A second determination step for determining whether the gradation of any one of the RGB three primary colors is fixed, and a case where it is determined that the gradation of any one of the RGB three primary colors is fixed And a white balance readjustment step for readjusting the gradation of at least one of the remaining two colors to a higher level. Method for manufacturing a display device.   2. The display device manufacturing method according to claim 1, wherein in the white balance readjustment step, when the R tone is fixed among the three primary colors of RGB, the G tone and the B tone are readjusted high, and A method of manufacturing a display device, wherein, when the B gradation is fixed among the three primary colors of RGB, the G gradation and the R gradation are readjusted to a high level.   3. The method of manufacturing a display device according to claim 2, wherein the white balance readjustment step uses a predetermined adjustment rate or the G gradation and the B gradation, or the G gradation and the R gradation. A method of manufacturing a display device, wherein the adjustment amount is increased.   3. The method of manufacturing a display device according to claim 2, wherein the white balance readjustment step calculates a gradation when the screen luminance of the display device becomes the reference luminance with respect to the G gradation, The calculated gradation is used as the G gradation after readjustment, and the B gradation or the R gradation is increased by an adjustment rate or adjustment amount determined from the G gradation before and after readjustment. A method for manufacturing a display device.   5. The display device manufacturing method according to claim 1, wherein in the white balance readjustment step, the screen chromaticity of the display device after the white balance readjustment falls within an allowable range. A method of manufacturing a display device, characterized by limiting an adjustment rate or an adjustment amount when readjusting a gradation of at least one of the remaining two colors.

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