JP2010117579A - Liquid crystal display device and method of improving viewing angle characteristic in the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device having improved viewing angle characteristic. <P>SOLUTION: In the liquid crystal display device, a position of a viewer is detected, and white luminance correction or black luminance correction is performed so that a screen state may be the best as seen from the position of the viewer. In the correction, the entire screen is divided into a plurality of blocks and a state of an image of the block (rate of a low-luminance pixel and a rate of a high-luminance pixel) is verified, to decide whether the black luminance correction is performed, whether the white luminance correction is performed or whether the correction is not performed according to the verification. At first, brightness of the entire screen is determined. When the brightness of the entire screen shows a darker condition than specified brightness, or when it shows a brighter condition than the specified brightness, the black luminance correction and the white luminance correction may be performed, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device having improved viewing angle characteristics and a method for improving viewing angle characteristics in the liquid crystal display device.

  In general, a liquid crystal display device has a structure in which two glass substrates are fixed to face each other and liquid crystal is sealed between them, a transparent common electrode is formed on one glass substrate, and a large number are formed on the other glass substrate. Transparent pixel electrodes are formed in a matrix, and a circuit for selectively applying a voltage to each pixel electrode is formed.

  The liquid crystal display device is configured by sandwiching the above structure between polarizing plates, and has a so-called viewing angle characteristic in which contrast and the like decrease depending on the direction in which the liquid crystal display device is viewed. Various proposals have been made to improve the viewing angle characteristics.

  FIGS. 7A, 7B, and 7C illustrate viewing angle characteristics in a VA (Vertical Alignment) mode that is currently widely used as a display device of a liquid crystal television and measures for improving the viewing angle characteristics. In the VA mode, for example, as shown in FIG. 7A, the longitudinal direction of the liquid crystal molecules 100 is perpendicular to the panel surface 101 when off (black display), and the liquid crystal when on (white display). The longitudinal direction of the molecule 100 and the panel surface 101 become horizontal. In the halftone, the liquid crystal molecules 100 are obliquely directed in the same direction. However, since the state of the liquid crystal molecules varies depending on the viewing angle of the display screen, the display image does not look normal depending on the viewing direction of the liquid crystal screen. It becomes a state.

  In order to improve the viewing angle characteristics in such a halftone, particularly, an MVA (Multi-domain VA) mode shown in FIGS. 7B and 7C has been proposed. As a structure of the liquid crystal display device, for example, as shown in FIG. 7B, a structure 102 having a substantially triangular cross section is added on the surfaces of glass substrates 101 and 102, and an alignment film is formed thereon. In the liquid crystal display device having such a structure, when liquid crystal is sealed between the glass substrates 101 and 102 and a driving voltage is applied, the liquid crystal molecules 100 are converted into the triangular structure 102 as shown in FIG. It falls down diagonally along. In this case, the liquid crystal molecules are tilted in two different directions, and the same effect as the so-called divided alignment is obtained, and a wide viewing angle characteristic is obtained.

  Patent Document 1 discloses a technique for improving that the display quality of a liquid crystal display device, in particular, gradation characteristics vary depending on the viewing direction. FIG. 8 shows a configuration example of an active matrix liquid crystal display device 110 for solving the above-described problem disclosed in Patent Document 1. In FIG. In FIG. 8, the liquid crystal display device 110 includes a drive signal generation unit 111, a LUT (Look Up Table) 112, a drive voltage generation unit 113, a source drive circuit 114, a gate drive circuit 115, and a liquid crystal panel 116.

  The drive signal generation unit 111 is a part that generates signals for driving the source drive circuit 114 and the gate drive circuit 115 based on the image data input to the liquid crystal display device 110 and the reference result of the LUT 112. The LUT 112 is a conversion table for converting image data so that a correct gradation curve is obtained when the image data is displayed on the liquid crystal display device, and data relating to a correction amount corresponding to the input image data is stored. Has been.

The image data input to the liquid crystal display device 110 is sent to the LUT 112 together with the drive signal generation unit 111. The LUT 112 refers to the conversion table based on the input image data, and outputs data relating to the correction amount of the gradation curve to the drive signal generator 111. The drive signal generator 111 outputs corrected image data, which is image data having a value for correcting the distortion of the gradation curve, and sends the corrected image data to the source drive circuit 114 and the gate drive circuit 115.
JP 2003-295160 A (publication date October 15, 2003)

  According to the technique described in Patent Document 1, it is possible to eliminate the viewing angle dependency of the relative gradation characteristics, but it is not possible to eliminate the viewing angle dependency of the absolute values of white luminance and black luminance. . In particular, in a large-screen liquid crystal display device, in-plane luminance changes depending on viewing angle characteristics, such as black floating in a peripheral portion of the screen and a portion with a large viewing angle, are conspicuous.

  9, FIG. 10 and FIG. 11 are diagrams for explaining the above-described situation.

  FIG. 9 is a front view of a liquid crystal display device 120 such as a liquid crystal television. As shown in FIG. 9, the entire display screen of the liquid crystal display device is divided into 50 blocks divided in the vertical direction, and for convenience, numbers 1, 2,..., 50 are assigned from the left. FIG. 10 shows how viewers A, B, and C are viewing the display screen of the liquid crystal display device 120. The viewer A is viewing from a distance 3H that is three times the height H of the liquid crystal display device 120 in front of the center of the display screen of the liquid crystal display device 120, and the viewer B is at the viewing position of the viewer A. The viewer C is viewing from a position 15 degrees from the center of a display screen, and the viewer C is viewing from a position 30 degrees from the center of the display screen. In the specification of the present application, the viewing angle is used to mean “the horizontal component of the angle formed by the normal direction of the screen and the viewing direction of the viewer”. Therefore, in FIG. Is a position at a viewing angle of 0 °, and the position of B is a position at a viewing angle of 15 °.

  FIGS. 11A, 11B, and 11C show changes in black luminance and white luminance depending on the viewing position of the display screen when the viewers A, B, and C look at the liquid crystal display device 120. FIG. Yes. In FIGS. 11A, 11B, and 11C, the left vertical axis indicates a relative change in white luminance, and the right vertical axis indicates a relative change in black luminance. The horizontal axis indicates the block positions divided in the column direction (horizontal direction) of the liquid crystal television shown in FIG. 11A, 11B, and 11C, the upper line segment indicates a change in white luminance, and the lower line segment indicates a change in black luminance.

  With reference to Fig.11 (a), the change of the black luminance in the display screen of a liquid crystal display device by a viewing-and-listening position and white luminance is demonstrated. When the liquid crystal display device is viewed from the position of the viewer A, assuming that the white luminance of the front portion (block 25) is 1, the white luminance at both end portions is a value lower than 1 (close to gray). That is, as the viewing angle increases, the white luminance value that should be originally displayed deviates. Similarly, regarding the black luminance, when the black luminance of the front portion is set to 0, the both end portions are largely shifted and a so-called black floating phenomenon occurs.

  FIGS. 11B and 11C show the changes in white luminance and black luminance when the display screen of the liquid crystal display device 120 is viewed from the positions of the viewers B and C. FIG. As is apparent from FIGS. 11B and 11C, it can be seen that as the viewing angle increases, the white luminance decreases and the black luminance increases (black float) increases. As described above, it can be seen that the absolute values of white luminance and black luminance greatly depend on the viewing angle.

  The present invention is in view of the problem of the prior art described in Patent Document 1 and the problem of the viewing angle dependence of the absolute values of white luminance and black luminance that cannot be ignored with the increase in the screen size of the liquid crystal display device described above. It is possible to improve the non-uniform display in the screen, which was of interest in the past, by reducing the change of black floating and white brightness in the display screen due to the viewing angle characteristics. Another object of the present invention is to provide a liquid crystal display device that can perform optimal display according to the position of the viewer and the content of the video.

In order to solve the above-described problem, in the liquid crystal display device according to the present invention,
A liquid crystal display unit, a backlight unit composed of a plurality of unit blocks that divide the display screen of the liquid crystal display unit and capable of controlling the luminance for each unit block, and a luminance correction control unit for correcting and controlling the luminance of the backlight unit A liquid crystal display device comprising:
The brightness correction control unit is positioned at the viewer position based on a viewer position detection unit that detects a viewer position, a viewing angle profile based on the detected viewer position, and a viewing angle characteristic of the liquid crystal display unit. A calculation unit for calculating a corresponding white luminance profile and a black luminance profile, a luminance histogram calculation unit for each block for calculating a luminance histogram of a video signal corresponding to the unit block, and a luminance histogram for a plurality of unit blocks belonging to the same row. The comparison unit, the luminance correction determination unit that determines the suitability of the correction using the comparison result from the comparison unit, and the type of correction, and the backlight unit for each unit block that receives the output from the luminance correction determination unit It is characterized by having an output control unit for controlling.

  According to this, it is possible to improve the viewing angle characteristics of the liquid crystal display device in consideration of the position of the viewer.

In order to solve the above-described problem, in the liquid crystal display device according to the present invention,
The comparison unit compares the ratio of the low gradation part and the ratio of the high gradation part in the luminance histogram of each unit block in the same row, and the ratio of the low gradation degree is higher than Rl in all the unit blocks in the same row. Determine whether the ratio of high gradation is greater than Rh in all unit blocks in the same row,
The luminance correction determination unit performs black luminance correction on the row when the ratio of the low gradation level is larger than Rl in all the unit blocks in the same row, and the high gradation level is applied in all the unit blocks in the same row. When the ratio is larger than Rh, white luminance correction is performed on the row, and in other cases, it is determined that correction is not performed on the row.

  This makes it possible to perform black luminance correction or white luminance correction that is optimum for each row and for that row, and it is possible to improve the viewing angle characteristics that are highly effective.

In order to solve the above-described problem, in the liquid crystal display device according to the present invention,
The low gradation portion ratio Rl is 20%, and the high gradation portion ratio Rh is 30%.

  According to this, it is possible to select black luminance correction or white luminance correction under optimum conditions, and an improvement effect of a large viewing angle characteristic can be expected.

In order to solve the above-described problem, in the liquid crystal display device according to the present invention,
The viewing angle characteristics of the liquid crystal display unit are described in a look-up table.

  According to this, a huge amount of data relating to the viewing angle characteristics of the liquid crystal display unit can be stored in an easy-to-handle form, and the processing efficiency of the liquid crystal display device can be increased.

In order to solve the above-described problem, in the liquid crystal display device according to the present invention,
Further, an arithmetic unit for calculating the average luminance of the entire display screen is provided, and when the average luminance is lower than a predetermined value APL1, black luminance correction is performed on the entire screen, and the average luminance is a predetermined value APL2. If it is higher, white luminance correction can be performed on the entire screen. According to this, the display image quality of the liquid crystal display device can be improved by simple processing.

In order to solve the above-described problem, in the liquid crystal display device according to the present invention,
Only when the average luminance is between APL1 and APL2, correction for the same row is performed in consideration of the output from the comparison unit.

  According to this, it is possible to reduce the “correction for the same row” with a large amount of processing, and to improve the operation efficiency as the liquid crystal display device.

In order to solve the above-described problem, in the liquid crystal display device according to the present invention,
The APL1 is 20%, and APL2 is 70%.

  The above values have been obtained by many experiments. Therefore, this value is effective for improving the display image quality and increasing the processing efficiency.

In order to solve the above-described problem, in the viewing angle characteristic improving method in the liquid crystal display device according to the present invention,
The step of detecting the position of the viewer, the step of calculating the black luminance profile and the white luminance profile of the liquid crystal display unit corresponding to the position of the viewer, the liquid crystal display unit being divided into a plurality of unit blocks, and the luminance for each unit block Comparing the ratio of the low gradation part and the ratio of the high gradation part in the luminance histogram of the plurality of unit blocks belonging to the same row as the step of calculating the histogram, the ratio of the low gradation degree is obtained in all the unit blocks of the same row. A step of determining whether the ratio of the high gradation in all the unit blocks in the same row is greater than Rh, and if the ratio of the low gradation in all the unit blocks in the same row is greater than Rl, the row If the ratio of the high gradation level is higher than Rh in all unit blocks in the same row, the white luminance correction is performed on the row. It is characterized by having a step of determining not to perform correction with respect to the line in other cases.

  According to this, the liquid crystal display which can reduce the black floating and white brightness change in the display screen due to the viewing angle characteristics, and improve the non-uniform display in the screen which has been a concern in the past. It is possible to provide a method for improving the viewing angle characteristics of the device, and it is possible to provide a liquid crystal display device capable of optimal display in accordance with the viewer's position and video content.

  In order to solve the above problem, in the viewing angle characteristic improving method in the liquid crystal display device according to the present invention, the ratio Rl of the low gradation part is 20% and the ratio Rh of the high gradation part is 30%. It is characterized by that.

  According to this, it is possible to select black luminance correction or white luminance correction under optimum conditions, and an improvement effect of a large viewing angle characteristic can be expected.

  In order to solve the above-described problem, in the viewing angle characteristic improving method in the liquid crystal display device according to the present invention, the average luminance of the entire display screen is calculated, and the screen is displayed when the average luminance is lower than a predetermined value APL1. The black luminance correction is performed on the entire screen, and when the average luminance is higher than a predetermined value APL2, the step of performing the white luminance correction on the entire screen is performed first.

  According to this, since a particularly dark screen, particularly a bright screen, is selected and corrected in advance with a light processing amount, the processing efficiency as a liquid crystal display device can be improved, and the overall image quality can be improved. Can be increased.

  In order to solve the above-described problem, in the viewing angle characteristic improving method in the liquid crystal display device according to the present invention, when it is detected that the number of viewers is two or more, only the portion that is effective for two or more viewers is used. It is characterized by having the step which correct | amends.

  According to this, even when there are two or more viewers, the image quality for all viewers can be improved without degrading the original image quality.

As described above, in the liquid crystal display device according to the present invention,
A liquid crystal display unit, a backlight unit composed of a plurality of unit blocks that divide the display screen of the liquid crystal display unit and capable of controlling the luminance for each unit block, and a luminance correction control unit for correcting and controlling the luminance of the backlight unit A liquid crystal display device comprising:
The luminance correction control unit includes a viewer position detection unit that detects a viewer position, a calculation unit that calculates a white luminance profile and a black luminance profile according to a viewing angle based on the detected viewer position, A luminance histogram calculation unit for each block that calculates a luminance histogram of a video signal corresponding to a unit block, a comparison unit that compares luminance histograms of a plurality of unit blocks belonging to the same row, and a correction result using a comparison result from the comparison unit A luminance correction determination unit that determines suitability and type of correction, and an output control unit that receives the output from the luminance correction determination unit and controls the backlight unit for each unit block.

Further, in the viewing angle characteristic improving method in the liquid crystal display device according to another invention of the present application,
The step of detecting the viewer position, the step of calculating the black luminance profile and the white luminance profile of the liquid crystal display unit corresponding to the viewer position, the liquid crystal display unit being divided into a plurality of unit blocks, and the luminance for each unit block Comparing the ratio of the low gradation part and the ratio of the high gradation part in the luminance histogram of the plurality of unit blocks belonging to the same row with the step of calculating the histogram, the proportion of the low gradation degree in all the unit blocks of the same row Determining whether the ratio of high gradation is greater than Rh in all unit blocks in the same row, and if the ratio of low gradation is greater than Rl in all unit blocks in the same row, Black luminance correction is performed on the row, and when the ratio of the high gradation level is higher than Rh in all unit blocks in the same row, white luminance correction is performed on the row, In cases other than the serial is characterized by having a step of determining not to perform correction on the line.

  According to this, the liquid crystal display which can reduce the black floating and white brightness change in the display screen due to the viewing angle characteristics, and improve the non-uniform display in the screen which has been a concern in the past. An apparatus can be provided, and a liquid crystal display device capable of optimal display according to a viewer's position and video content can be provided.

  Before describing the embodiment of the present invention, first, the basic concept of the present invention will be described with reference to FIG.

  FIG. 6 is a diagram showing the viewing angle characteristics of a certain liquid crystal television and the effect of luminance correction according to the present invention when a viewer views a liquid crystal display device, for example, a liquid crystal television, from the position B in FIG. . In FIG. 6, the horizontal axis represents 50 block positions obtained by dividing the display screen shown in FIG. 9 in the vertical direction, the left vertical axis represents white luminance, and the right vertical axis represents black luminance. Represents.

  The line segment W0 indicates the white luminance (255 gradation level at 256 gradations) when correction is not performed, and b0 indicates the black luminance (0 gradation level at 256 gradations) when correction is not performed. Show. In the case where the horizontal scale is larger (see FIG. 9, right end of the display screen of the liquid crystal display device), both the white luminance and the black luminance are almost equal to desired values, but the horizontal memory is small. On the other hand (at the left end of the display screen of the liquid crystal display device), the white luminance is low and the black luminance is high. This is because the viewer B's position is close to the front of the right end of the screen and away from the left end, so that the viewing angle when viewing the left end is increased.

  Human visual characteristics are sensitive to changes in black luminance. In this case, for example, in an image that is almost black, such as the night sky, black floating in the left direction of the screen is a concern. In order to reduce the black float, the brightness of the backlight at this point should be reduced.

  In the invention of the present application, based on the above concept, the backlight unit of the liquid crystal display device is configured by a unit that can be controlled for each block such as an LED backlight, and each block is controlled according to the position of the viewer and the type of the video signal. Control the backlight. b1 and b2 show profiles on the display screen of black luminance when black luminance correction is performed. In order to correct the black luminance, the white luminance is lowered in order to reduce the LED luminance in the area where the black float is caused. When the black luminance is corrected and the black luminance profiles are b1 and b2, the white luminance profiles are W1 and W2, respectively.

  As described above, since the correction of black luminance and the correction of white luminance are in a trade-off relationship, correction according to conditions is necessary, but in general, changes in white luminance are perceived by human visual characteristics. Since it is difficult, correction mainly focusing on black luminance is important.

  In the above description, only the luminance difference in the horizontal direction on the display screen of the liquid crystal display device is corrected, but the correction described in detail in the embodiment is applied to the vertical viewing angle. The correction may be applied to the luminance difference correction based on the correction, and the correction in the row direction block may be performed in consideration of the luminance difference in the vertical direction.

Embodiment
Embodiments according to the present invention will be described below. In the following description, various limitations preferable for carrying out the present invention are given, but the technical scope of the present invention is not limited to the following embodiments and drawings.

  FIG. 1 is a block diagram of an apparatus for correcting black luminance and white luminance in a liquid crystal display device according to the present invention, and FIG. 2 explains whether black luminance correction or white luminance correction is performed on an actual display image. FIG. 3 is a diagram for explaining the correction when the number of viewers is two, FIG. 4 is a flowchart for explaining the operation of the liquid crystal display device of the present invention, and FIG. 2 is a diagram for explaining a viewing angle profile in FIG.

  In FIG. 1, reference numeral 10 denotes a luminance correction control unit that performs black luminance correction or white luminance correction in consideration of the viewer's viewing position, video signal, etc., and 20 denotes a unit block when the display screen is divided into a plurality of blocks. The backlight unit is composed of LEDs or the like that can control the brightness (brightness) for each, and 30 is a display unit made of liquid crystal.

  The brightness correction control unit 10 is a viewer position detection unit 11 that detects the position of the viewer. When the viewer detects that the viewer is at a specific position, the viewing angle state (profile) when the display screen is viewed from that position. ) Viewing angle profile calculation unit 12, viewing angle characteristic LUT13 having a look-up table (LUT) in which data representing the relationship between viewing angle and white luminance or black luminance is entered, and when the display screen is divided into a plurality of blocks A luminance histogram calculation unit 14 for each block for obtaining a luminance distribution (histogram) for each block in a specific input video signal, and a ratio of a low gradation portion and a ratio of a high gradation portion in a luminance histogram within the same block are determined in advance. The comparison unit 15 for comparing with the ratio calculates the average signal level of the input video signal (Average Signal Level). APL calculation unit 16, a luminance correction determination unit 17 that determines whether white luminance correction is actually performed or black luminance correction, and an output calculation unit 18 that calculates an output of an LED or the like necessary for correction.

  The LED backlight unit 20 is composed of a plurality of unit blocks 21, 22..., And each unit block can be individually adjusted in luminance. In this embodiment, the liquid crystal screen shown in FIG. It is provided corresponding to 50 blocks divided in the vertical direction.

  The liquid crystal display unit 30 is a liquid crystal display device such as an MVA mode, and is driven by a drive circuit (not shown) to display an image according to a video signal or the like. A typical example of a liquid crystal display device is a liquid crystal television, and in the following description, a liquid crystal television is described as an example. However, the present invention is not limited to a television, but can be applied to a general liquid crystal display device. Not too long.

  An embodiment of the present invention will be described with reference to FIG. When a viewer sits in front of a liquid crystal display device such as a liquid crystal television, the viewer position detection unit 11 detects where the viewer is sitting in front of the display screen. Various known devices can be used as the detection device. For example, a method based on image recognition using a CCD camera or the like can be used.

  Based on this position information, the viewing angle profile calculation unit 12 calculates a viewing angle profile. The viewing angle profile indicates a “distribution” situation of viewing angles in a screen when a viewer views a television display screen. For example, if the viewer is at a position B in FIG. The viewing angle profile shown in FIG. 5A is obtained. If the viewer is at the position A in FIG. 10, the viewing angle profile shown in FIG. 5B is obtained.

  As described above, data representing the relationship between the viewing angle and the white luminance or the black luminance is entered in the viewing angle characteristic LUT13. More specifically, for example, values of white luminance and black luminance in cd / m2 units may be included for viewing angles of 0 °, 1 °, 2 °,. The relative value when the white luminance at the time is 100 may be included. The data stored in the viewing angle characteristic LUT 13 is obtained for each liquid crystal display unit to be used, and represents the characteristics of the liquid crystal display unit to be used.

  When the output from the viewing angle profile calculation unit 12 is input to the viewing angle characteristic LUT 13, the viewing angle characteristic LUT 13 determines the white luminance status (white luminance profile) and the black luminance status (black) corresponding to a specific viewing angle profile. (Luminance profile) is output. More specifically, if the viewer position is B, profiles corresponding to the white luminance profile W0 and the black luminance profile b0 shown in FIG. 6 are output. Note that the white luminance profile W0 and the black luminance profile b0 are profiles that are not subjected to correction processing.

  On the other hand, when the input video signal is input to the block-by-block luminance histogram calculation unit 14, the block-by-block luminance histogram calculation unit 14, as described above, first, a specific input video signal when the display screen is divided into a plurality of blocks. The luminance distribution (brightness histogram) for each block in is calculated. This is, for example, to obtain the luminance histogram shown in FIG. 2B, and represents the luminance distribution on the display screen from the low gradation (black) to the high gradation (white). In FIG. 2B, the vertical axis direction indicates the number of pixels of a specific gradation. In FIG. 2, the number of blocks in the horizontal direction is five so that the subsequent description is not complicated.

  Further, the luminance histogram calculation unit 14 for each block obtains the ratio of the low gradation part and the ratio of the high gradation part in the luminance histogram in the same block based on the calculated luminance histogram for each block. The ratio of the low gradation part and the ratio of the high gradation part mean the ratio of the pixels belonging to the gradation part in a certain range to the whole pixels as shown in the luminance histogram shown in FIG. ing. More specifically, in a 256 gradation liquid crystal display device, for example, the range of the low gradation part is 0 to (30 to 80), and the range of the high gradation part is (200 to 230) to The ratio of low gradation pixels and the ratio of high gradation pixels that fall within this range are obtained.

  The comparison unit 15 receives “the ratio of the low gradation part and the ratio of the high gradation part in the luminance histogram in the same block” that is the output from the block-specific luminance histogram calculation unit 14, and Compare with luminance histogram.

  Details of the operations of the block-by-block luminance histogram calculation unit 14 and the comparison unit 15 will be described more specifically with reference to FIGS. In FIG. 2A, the display screen 30 of the liquid crystal television is divided into five in the horizontal direction and 11 in the vertical direction. As a result, the display screen 30 is divided into 5 × 11 blocks. Yes.

  The luminance histogram calculation unit 14 for each block analyzes the input video signal in each block to obtain the luminance for each pixel, creates the luminance distribution (luminance histogram) for each block shown in FIG. The ratio of the low gradation part and the ratio of the high gradation part in the histogram are obtained. For example, as shown in FIG. 2C, the ratio of the low gradation part of each block in the row n1 is 10%, 30%, 5%, 5%, 10% from the left, and the ratio of the high gradation part is From the left, they are 30%, 40%, 30%, 30% and 50%. Similarly, the ratio of the low gradation part and the ratio of the high gradation part are obtained for row n2, row n3,.

The comparison unit 15 receives the output from the block-specific luminance histogram calculation unit 14 and compares the luminance histograms between blocks in the same row. Then, it is determined whether one of the following conditions a or b is satisfied or not.
Condition a = the ratio of the low gradation portion is larger than Rl in the “all” region of each block in the same row.
Condition b = The ratio of the high gradation portion is larger than Rh in the “all” region of each block in the same row.

  In this embodiment, 20% is used as the ratio Rl and 30% is used as the ratio Rh. This numerical value is determined as the best numerical value while actually observing the screen. However, the numerical value is not limited to the above numerical value, and can be slightly changed in the vicinity of the above numerical value.

  When the input video signal is input, the APL calculation unit 16 calculates the average signal level (Average Signal Level) of the video signal for one screen, that is, the average brightness of the entire screen. Then, the calculation result APL is sent to the luminance correction determination unit 17.

  The luminance correction determination unit 17 uses the calculation result from the APL calculation unit 16 and the comparison result from the comparison unit 15 to determine whether correction is necessary for the entire screen, for example, specific rows (for example, row n1 and row n2 in FIG. 2). ..)), The type of correction (black luminance correction or white luminance correction, etc.) when correction is necessary is determined. Details are as follows.

  The calculation result from the APL calculation unit 16 indicates the average brightness of the entire screen. If this value is low, the screen displays a dark image as an average, and if the value is high, the image is bright as an average. Will be displayed. Therefore, in this embodiment, first, the brightness correction determination unit 17 determines the overall brightness of the image based on the value of the calculation result from the APL calculation unit 16, and if the calculation result is low, the entire screen is blackened. If it is determined that the luminance is to be corrected, and if the calculation result is high, it is determined that the entire screen is to be corrected for white luminance. For example, if the value of the calculation result is 20% (APL1) or less, the luminance correction determination unit 17 determines that the entire image is a dark image and determines that the entire screen is to be corrected for black luminance. If the value of the result is 70% (assumed to be APL2) or more, it is determined that the overall image is bright, and it is determined that white luminance correction is performed on the entire screen. Further, the luminance correction determination unit 17 determines a correction coefficient indicating how much correction should be performed.

  When the calculation result from the APL calculation unit 16 is between 20% (APL1) and 70% (APL2), the luminance correction determination unit 17 uses the comparison result from the comparison unit 15 to specify a specific “row ni”. The type of correction (black luminance correction or white luminance correction, etc.) to be performed is determined. That is, when a specific “row ni” satisfies the condition a, the luminance correction determination unit 17 determines that black luminance correction is to be performed on the “row ni”, and the condition b Is satisfied, the luminance correction determination unit 17 determines that white luminance correction is to be performed on the “row ni”. In other cases, it is determined that luminance correction is not performed. Further, the luminance correction determination unit 17 determines a correction coefficient indicating how much correction should be performed.

  For example, in FIG. 2C, in the case of row n1, since the ratio of the high gradation portion is 30% or more in all the blocks and the condition b is satisfied, the luminance correction determination unit 17 determines that white It is determined that luminance correction is to be performed. In the case of the row n2, the ratio of the low gradation portion is 20% or more in all the blocks, and the luminance correction determination unit 17 determines to correct the black luminance. In the case of the row n3, since the condition a and the condition b are satisfied at the same time, the luminance correction determination unit 17 determines that no luminance correction is performed. Further, the luminance correction determination unit 17 determines a correction coefficient indicating how much correction should be performed in both cases of black luminance correction and white luminance correction.

  Based on the determination result from the luminance correction determination unit 17, the output calculation unit 18 calculates an LED drive output that enables the determined correction. That is, for example, when black luminance correction or white luminance correction is performed on the entire screen, an output necessary for LED driving is calculated in consideration of a correction coefficient indicating how much correction should be performed from the luminance correction determination unit 17. Is sent to the light source output control unit 19. The light source output control unit 19 controls the LED backlight unit according to a specific correction amount.

  When the calculation result from the APL calculation unit 16 is between 20% (APL1) and 70% (APL2), the output calculation unit 18 outputs the output from the viewing angle characteristic LUT 13 and the output from the luminance correction determination unit 17. Then, a specific correction amount for correcting the specific row ni is calculated and sent to the light source output control unit 19. The light source output control unit 19 controls the output of the unit blocks 21, 22... Of the LED backlight unit 20 according to a specific correction amount.

  For example, the viewing angle characteristic LUT 13 outputs “a luminance profile for a specific row ni according to the viewer's position” indicated by W 0 and b 0 in FIG. 6, and the luminance correction determination unit 17 outputs “black correction”. And a correction coefficient α1 ”that determines a correction amount and a determination result that the correction should be performed are output. In consideration of the output from the viewing angle characteristic LUT13 and the output from the luminance correction determination unit 17, the output calculation unit 18 performs “LED driving for changing the luminance profile b0 (without correction) to the luminance profile b1” shown in FIG. “Necessary output” is calculated and sent to the light source output control unit 19. The light source output control unit 19 controls the output of the unit blocks 21, 22... Of the LED backlight unit 20 according to a specific correction amount.

  The above-mentioned APL1 (20%) and APL2 (70%) are numerical values obtained by examining various videos, and some fluctuations are allowed, but normal video should be corrected effectively. It is a value that can be. That is, when the conditions are relaxed (30% as APL1 and 60% as APL2), the luminance correction has an adverse effect (rather, it emphasizes the black float or unnaturally increases the change in white luminance). It became high. If the conditions are strict, the probability that the luminance correction has an adverse effect is lowered, but this time, the necessary correction may not be applied.

  The values of Rl and Rh described above are Rl = 20% and Rh = 30% in the embodiment, but it is needless to say that some variation is allowed without being limited to these values. Since black is more sensitive to human eyes, the conditions are relaxed.

  The correction process described above can be performed for each screen. However, in the case of an image with a rapidly changing screen, the image quality may be deteriorated. Therefore, it may be controlled by calculating an average value for a specific period. In addition, since it is easy to detect that the screen changes greatly, it is possible to detect this and perform processing according to the video. In addition, in a television, it is easy to determine the type of video by referring to an electronic program guide or the like, so that an optimum value can be selected according to the type of video (for example, animation, drama, etc.). It is also possible to leave.

  In FIG. 2, the number of blocks in the horizontal direction is described as 5, and in FIG. 6, the number of blocks in the horizontal direction is 50. In general, finer correction can be performed by increasing the number of blocks, but the amount of data processing required for correction increases. The same applies to the number of rows in the vertical direction. It may be determined in consideration of the amount of processing.

  The above description is made on the assumption that there is only one viewer. The present invention can be applied even when there are two or more viewers. FIG. 3 is a diagram for explaining a correction method in this case. FIG. 3 shows a case where, for example, the viewer is at a position A (see FIG. 10) at a position 15 (see FIG. 10) deviated from the front by a position A (see FIG. 10). In this case, the luminance profile at position A is as shown in FIG. 3A, and the luminance profile at position B is as shown in FIG. As is clear from FIGS. 3A and 3B, the range that has a correction effect for both the viewers at position A and position B is the “correction range” on the left side of the drawing. In this way, when there are a plurality of viewers, a range in which correction is effective for a plurality of viewers is obtained, and correction is performed only on those portions.

  The operation of the liquid crystal display device according to the present invention will be described with reference to FIGS.

  Referring to FIG. 4, when the viewer position information (distance and angle from the display screen) is obtained from viewer position detector 11 in step 1 (hereinafter referred to as S1), in S2, the viewer It is determined whether or not there is one person.

  When there is only one viewer, in S3, the viewing angle profile calculation unit 12, the viewing angle characteristic LUT 13 and the like calculate the white luminance profile and the black luminance profile in each block with respect to the viewing angle corresponding to the viewing position of the viewer. . Next, in S4, the APL calculation unit 16 calculates APL. When APL <APL1, it is determined that the image is a dark image and the black luminance of the entire screen is corrected (S5). When APL> APL2, The entire screen is corrected for white brightness as an image that is too bright (S6).

  In the case of APL1 ≦ APL ≦ APL2, the process proceeds to S7, and luminance histogram comparison between the same row blocks is performed to correct each row. That is, when “ratio of low gradation part”> Rl, black luminance correction is performed (S5), and when “ratio of high gradation part”> Rh, white luminance correction is performed (S6). In any case, luminance correction is not performed (S8).

  When there are two or more viewers, the same processing as S3 is performed on each viewer in S9. That is, for each viewer, a white luminance profile and a black luminance profile in each block with respect to the viewing angle corresponding to the viewing position of the viewer are calculated. Next, in S10, a block that can obtain the effect of brightness correction is detected for all viewers. After S4, the steps are the same as in the case of one viewer.

  According to the present invention, the industrial utility value is extremely high, such as providing a large-screen liquid crystal television with improved viewing angle characteristics.

It is a block diagram which shows the outline | summary of the liquid crystal display device which concerns on this invention. It is a figure for demonstrating operation | movement of the liquid crystal display device based on this invention. It is a figure for demonstrating the case where there are two or more viewers. 4 is a flowchart for explaining the operation of the liquid crystal display device according to the present invention. It is a figure for demonstrating a viewing angle profile. It is a figure for demonstrating white luminance correction and black luminance correction. It is a figure for demonstrating the state of the liquid crystal molecule in a liquid crystal display device. It is a block diagram which shows the outline of the conventional rear liquid crystal display device. It is a figure for demonstrating the block in the display screen of a liquid crystal television. It is a figure for demonstrating the positional relationship of a liquid crystal television and a viewer. It is a figure which shows a viewer's position and the brightness | luminance profile corresponding to the position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Brightness correction control part 11 Viewer position detection part 12 Viewing angle profile calculation part 13 Viewing angle characteristic LUT
14 luminance histogram calculation unit 15 by block 15 comparison unit 16 APL calculation unit 17 luminance correction determination unit 18 output calculation unit 19 light source output control unit 20 LED backlight units 21 and 22 unit block 30 liquid crystal display unit

Claims (11)

A liquid crystal display unit, a backlight unit configured with a plurality of unit blocks that divide the display screen of the liquid crystal display unit, and capable of controlling the luminance for each unit block, and a luminance correction control unit for correcting and controlling the luminance of the backlight unit A liquid crystal display device comprising:
The brightness correction control unit includes a viewer position detection unit that detects the position of the viewer, a viewing angle profile based on the detected viewer position, and a viewing angle characteristic of the liquid crystal display unit. A calculation unit that calculates a white luminance profile and a black luminance profile according to the unit, a luminance histogram calculation unit for each block that calculates a luminance histogram of a video signal corresponding to the unit block, and a luminance histogram of a plurality of unit blocks belonging to the same row A comparison unit, a luminance correction determination unit that determines the suitability of the correction using the comparison result from the comparison unit, and a type of correction, and the backlight unit that receives the output from the luminance correction determination unit A liquid crystal display device comprising: an output control unit that is separately controlled. The comparison unit compares the ratio of the low gradation part and the ratio of the high gradation part in the luminance histogram of each unit block in the same row, and the ratio of the low gradation degree is higher than Rl in all the unit blocks in the same row. Determine whether the ratio of high gradation is greater than Rh in all unit blocks in the same row,
The luminance correction determination unit performs black luminance correction on the row when the ratio of the low gradation level is larger than Rl in all the unit blocks in the same row, and the high gradation level is applied in all the unit blocks in the same row. 2. The liquid crystal according to claim 1, wherein when the ratio is larger than Rh, white luminance correction is performed on the row, and in other cases, it is determined not to perform correction on the row. Display device.   3. The liquid crystal display device according to claim 2, wherein the ratio Rl of the low gradation part is 20%, and the ratio Rh of the high gradation part is 30%.   4. The liquid crystal display device according to claim 1, wherein the viewing angle characteristics of the liquid crystal display unit are entered in a look-up table.   Further, an arithmetic unit for calculating the average luminance of the entire display screen is provided, and when the average luminance is lower than a predetermined value APL1, black luminance correction is performed on the entire screen, and the average luminance is a predetermined value APL2. 5. The liquid crystal display device according to claim 1, wherein when the height is higher, white luminance correction can be performed on the entire screen. 6.   6. The liquid crystal display device according to claim 5, wherein the correction for the same row is performed in consideration of the output from the comparison unit only when the average luminance is between APL1 and APL2.   7. The liquid crystal display device according to claim 6, wherein APL1 is 20% and APL2 is 70%. Detecting the position of the viewer;
Calculating a black luminance profile and a white luminance profile of the liquid crystal display unit corresponding to the position of the viewer;
Dividing the liquid crystal display unit into multiple unit blocks and calculating the luminance histogram for each unit block and comparing the ratio of the low gradation part and the high gradation part in the luminance histogram of multiple unit blocks belonging to the same row Determining whether the low gradation ratio is higher than Rl in all unit blocks in the same row or whether the high gradation ratio is higher than Rh in all unit blocks in the same row;
When the ratio of low gradation in all unit blocks in the same row is larger than Rl, black luminance correction is performed on the row, and in the case where the ratio of high gradation in all unit blocks in the same row is larger than Rh. Includes a step of performing white luminance correction on the row and determining not to perform correction on the row in cases other than the above, and a method for improving a viewing angle characteristic in a liquid crystal display device.   9. The viewing angle characteristic improving method for a liquid crystal display device according to claim 8, wherein the low gradation portion ratio Rl is 20% and the high gradation portion ratio Rh is 30%.   The average luminance of the entire display screen is calculated, and when the average luminance is lower than the predetermined value APL1, black luminance correction is performed on the entire screen, and when the average luminance is higher than the predetermined value APL2. 10. The method of improving viewing angle characteristics in a liquid crystal display device according to claim 8, wherein the step of performing white luminance correction on the entire screen is first performed.   11. The method according to claim 8, further comprising a step of correcting only a portion that is effective for two or more viewers when it is detected that the number of viewers is two or more. A method of improving viewing angle characteristics in the liquid crystal display device described above.

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