JP2012013787A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of preventing occurrence of a pseudo contour and improving display quality even when response time of a liquid crystal display panel is different in each part.SOLUTION: A liquid crystal display device is configured such that, in parts of a liquid crystal display panel being opposed to respective light source units 5a to 5h, transition time is calculated based on gradation change between one image and the other image which are sequentially displayed, time of starting light-out and light-out time of the light source units 5a to 5h are set based on the calculated transition time, and the light source units 5a to 5h are turned off while an alignment state of liquid crystal elements changes in the parts of the liquid crystal display panel.

Description

  The present invention relates to a liquid crystal display device that controls the alignment state of liquid crystals and the lighting time of a light source.

  Liquid crystal display devices that occupy a small indoor area compared to the size of the display screen are widely used because they can effectively use a limited indoor space. The liquid crystal display device irradiates light from a light source unit accommodated in a rear cabinet to a liquid crystal display panel that displays an image arranged inside the front cabinet, and is based on input image information (image frame). It is configured to display an image.

  Since the liquid crystal display panel holds an image based on an input image frame for a predetermined time, so-called moving image blur is likely to occur, and in order to improve the moving image blur, there is a technique of turning off the light source unit intermittently (for example, a patent) Reference 1). In this technique, in order to improve display quality, the light source unit is turned off while the liquid crystal element arrangement state is changing on the liquid crystal display panel, and the change in the arrangement state of the liquid crystal element is visually recognized by the user as a so-called pseudo contour. It is necessary to prevent it from being done.

JP 2009-180933 A

  The liquid crystal display panel sequentially displays images based on sequentially input image frames. The gradation change in the same pixel between one image and another image displayed next to the one image is Different for each pixel. Therefore, the response time of each part of the liquid crystal display panel corresponding to each part of the image also increases or decreases according to the change in gradation in each part of the image. However, in the liquid crystal display device described in Patent Document 1, fixed values indicating the light extinction start time and the light extinction time of the light source unit are set in advance, and the difference in response time in each part of the image is not taken into consideration.

  As a result, depending on the position of the liquid crystal display panel, a response may be made at a time earlier than the light source unit turn-off start time, and a response may be finished at a time later than the light turn-off end time. For this reason, there is a problem in that the light source unit is turned on while the alignment state of the liquid crystal elements is changing, a pseudo contour is generated, and the display quality is deteriorated.

  The present invention has been made in view of such circumstances, and even when the response time of the liquid crystal display panel varies from part to part, a liquid crystal display device capable of preventing the generation of pseudo contours and improving the display quality is provided. The purpose is to provide.

  The liquid crystal display device according to the present invention includes a liquid crystal display panel that displays sequentially input images, and a plurality of light sources that are arranged in parallel to face the liquid crystal display panel and emit light toward the liquid crystal display panel. In the liquid crystal display device in which the plurality of light sources are intermittently lit during a display period in which the input image is displayed on the liquid crystal display panel, each of the portions of the liquid crystal display panel facing each light source Based on the gradation change of the first partial image in the displayed one image and the second partial image in the next sequential image, the response time calculating means for calculating the response time and the response time calculating means And a light extinction period setting means for setting a light extinction period of the light source in the display period based on the response time.

  In the present invention, in each part of the liquid crystal display panel facing the light source, the response time of the liquid crystal display panel corresponding to the change in gradation between one image displayed sequentially and the other image is calculated and calculated. Based on the response time, an extinguishing period of the light source is set, and the light source is extinguished while the arrangement state of the liquid crystal elements is changed in the portion of the liquid crystal display panel.

  The liquid crystal display device according to the present invention is characterized in that the response time calculating means calculates a change in gradation of the first partial image and the second partial image.

  In the present invention, the gradation change of the first partial image and the second partial image is obtained, and the response time of the liquid crystal display panel at the position corresponding to the first partial image and the second partial image is obtained based on the obtained gradation change. Is calculated.

  In the liquid crystal display device according to the present invention, the response time calculation unit corresponds to each of a plurality of image areas constituting the first partial image and a plurality of image areas constituting the first partial image, and the second part Means for obtaining a gradation change with each of a plurality of image areas constituting the image for each corresponding image area; and means for extracting a maximum response time based on the plurality of gradation changes obtained by the means; It is characterized by providing.

  In the present invention, the gradation change of the first partial image and the second partial image displayed in each part of the liquid crystal display panel is obtained for each corresponding image area, and based on the obtained maximum gradation change, The light source extinction period is set, and the light source is extinguished until the response of the liquid crystal element is finished in each part of the liquid crystal display panel.

  The liquid crystal display device according to the present invention includes current value control means for controlling the drive current of the light source facing the facing portion based on the response time calculated by the response time calculation means. .

  In the present invention, the driving current of the light source is controlled in correspondence with the extinguishing period set based on the response time, and the uniformization of the luminance in the entire liquid crystal display panel is promoted.

  The liquid crystal display device according to the present invention is characterized in that the current value control means increases or decreases the drive current according to the length of the extinction period set by the extinction period setting means.

  In the present invention, in each part of the liquid crystal display panel, when the set extinction period is long, the drive current at the time of lighting is increased to increase the luminance of the light source, and when the set extinction period is short, at the time of lighting The drive current is reduced to reduce the luminance of the light source, and the luminance during the period in which the image is held on the liquid crystal display panel (display period) is made uniform.

  In the liquid crystal display device according to the present invention, in each part of the liquid crystal display panel facing the light source, the response time corresponding to the gradation change between the sequentially displayed one image and the next image is calculated. . Based on the calculated response time, the light source is turned off, and the light source is turned off while the arrangement state of the liquid crystal elements is changing in each part of the liquid crystal display panel. Even when the response time varies from part to part, it is possible to prevent the occurrence of pseudo contours and improve the display quality.

It is a perspective view which shows the external appearance of a liquid crystal display device. It is a front view which briefly shows a light source unit. It is a block diagram which briefly shows the structure near a backlight control part and a video processing part. It is a block diagram which briefly shows the structure of a video analysis processing part. It is a conceptual diagram which shows one structural example of ROM. It is a conceptual diagram which shows the other structural example of ROM. FIG. 3 is a block diagram schematically showing a light source driving circuit. It is a timing chart which shows the relationship between a vertical synchronizing signal and an LED driver. It is a schematic diagram which shows the response characteristic of a liquid crystal display panel in case the response time before and behind a transition is early in the case where the image displayed on a liquid crystal display panel changes. It is a schematic diagram which shows the response characteristic of a liquid crystal display panel when the response time before and after transition is slow when the image displayed on a liquid crystal display panel changes.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating a liquid crystal display device according to an embodiment. FIG. 1 is a perspective view showing an appearance of a liquid crystal display device, and FIG. 2 is a front view schematically showing a light source unit.

  In the figure, reference numeral 1 denotes a rectangular liquid crystal display panel including a liquid crystal and a TFT (Thin Film Transistor). The liquid crystal display panel 1 controls the voltage applied to the liquid crystal by controlling the operation of the TFT, and changes the alignment state of the liquid crystal elements to adjust the light transmittance. By adjusting the light transmittance, a predetermined image is displayed on the front surface of the liquid crystal display panel 1.

  The liquid crystal display panel 1 has a peripheral edge sandwiched between a front holding frame and a rear holding frame (both not shown) and is housed in a rectangular frame-shaped front cabinet 2. The front cabinet 2 is disposed around the front holding frame and the rear holding frame. The front cabinet 2 has a rectangular opening, and the dimension of the opening corresponds to the liquid crystal display panel 1.

  On the rear side of the liquid crystal display panel 1, a rectangular plate-like backlight chassis 4 is disposed. A plurality (eight in the present embodiment) of light source units 5 a to 5 h are supported at the front portion of the backlight chassis 4. The light source units 5 a to 5 h and the backlight chassis 4 are accommodated in the rear cabinet 3. The front edge of the rear cabinet 3 is provided with an engaging convex part (not shown), and the rear edge part of the front cabinet 2 is provided with an engaging concave part (not shown). The engaging concave part and the engaging convex part are engaged with each other. The front cabinet 2 and the rear cabinet 3 are connected.

  The light source units 5a to 5h are lined up and down, the light source unit 5a is located at the top, and the light source unit 5h is located at the bottom. The light source units 5 a to 5 h include a rectangular horizontally long substrate 50 and a plurality of LEDs (Light Emitting Diodes) 51, 51,... 51 mounted on the substrate 50. The LEDs 51, 51,..., 51 are arranged in the horizontal direction at equal intervals on the substrate 50, and are connected in series. In addition, each part of the liquid crystal display panel 1 which opposes each of the light source units 5a-5h is shown as the 1st part 1a-the 8th part 1h in FIG.

  On the rear side of the backlight chassis 4, a backlight control unit 70 that controls driving of the LEDs 51, a video processing unit 10 that performs various processes on an image frame input to the liquid crystal display panel 1, and the like are provided. FIG. 3 is a block diagram schematically showing the configuration in the vicinity of the backlight control unit 70 and the video processing unit 10.

An image frame is input to the liquid crystal display panel 1 through a video processing unit 10, a double speed processing unit 20, an OS (Over Shoot) processing unit 30, a video analysis processing unit 40, and a liquid crystal display panel timing generation unit 50.
An image frame indicating an image is input to the video processing unit 10 from a terminal (not shown) such as a tuner and HDMI (High Definition Multimedia Interface). The video processing unit 10 performs contrast correction, color correction processing, and the like on the input image frame and outputs the result to the double speed processing unit 20.

The double speed processing unit 20 executes a process of doubling the number of images transmitted within a predetermined time based on the input image frame, and outputs the image frame to the OS processing unit 30.
The OS processing unit 30 performs processing for generating and adding overshoot or undershoot to the signal related to the input image frame, and outputs the image frame to the video analysis processing unit 40.

  Based on the sequentially input image frames, the video analysis processing unit 40 changes the gradation between one image and another image displayed on the liquid crystal display panel 1 next to the one image. Based on the calculated response time, a response time based on the light source units 5a to 5h is calculated, and based on the calculated response time, the light source units 5a to 5a in a period (display period) in which one image is held in the liquid crystal display panel 1 The lighting start time and the lighting time of each 5h are obtained, the magnitude of the driving current of each of the light source units 5a to 5h is obtained, and the information indicating the obtained lighting start time, the lighting time and the magnitude of the driving current is backlight controlled. To the unit 70.

Here, the gradation change is a numerical value that depends on each gradation value before and after the change, and corresponds to the transition time of the liquid crystal element, and the difference between the gradation value before the change and the gradation value after the change. Does not mean (absolute value). For example, the transition time of the liquid crystal element when the gradation changes from the gradation value 128 to the gradation value 0 and the transition time of the liquid crystal element when the gradation value changes from the gradation value 228 to the gradation value 100 If they are different, the absolute value in the former is equal to the absolute value in the latter, but the gradation change in the former and the gradation change in the latter are different.
The gradation change can be obtained based on various calculation methods. For example, each gradation value before and after the change is calculated by multiplying each gradation value by a predetermined correction coefficient, and the gradation change is calculated based on each calculated value, or each gradation value before and after the change is applied to a predetermined function and calculated. Then, the gradation change can be obtained based on the calculated values.

  The backlight control unit 70 includes an MPU (Micro Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) (not shown), and further includes a light source driving circuit 71 that drives the light source units 5a to 5h. The MPU of the backlight control unit 70 controls the operation of the light source driving circuit 71 and controls the driving of the light source units 5a to 5h based on the input information indicating the light extinction start time, the light extinction time, and the magnitude of the drive current. To do.

  The video analysis processing unit 40 outputs the image frame to the liquid crystal display panel timing generation unit 50. The liquid crystal display panel timing generation unit 50 includes a clock (not shown), and outputs a vertical synchronization signal VS and a horizontal synchronization signal HS to the liquid crystal display panel timing generation unit 50 based on the clocking result of the clock. The liquid crystal display panel timing generation unit 50 outputs an image frame to the liquid crystal display panel 1.

  The vertical synchronization signal VS and the horizontal synchronization signal HS are pulse waves, and the period of the pulse wave of the vertical synchronization signal VS is equal to the period in which the image frame is output from the liquid crystal display panel timing generation unit 50. The liquid crystal display panel 1 displays an image based on the image frame input from the liquid crystal display panel timing generation unit 50, and after the pulse wave of the vertical synchronization signal VS is input until the next pulse wave is input. , Keep the same image.

  Next, the configuration of the video analysis processing unit 40 will be described. FIG. 4 is a block diagram schematically showing the configuration of the video analysis processing unit 40, FIG. 5 is a conceptual diagram showing one configuration example of the ROM, and FIG. 6 is a conceptual diagram showing another configuration example of the ROM.

  The video analysis processing unit 40 includes an MPU 41, a ROM 42 that stores a control program, a RAM 43 that temporarily stores information, an input I / F (InterFace) 44, and an output I / F 45 that are mutually connected via a common bus. ing. The MPU 41 reads the control program stored in the ROM 42 into the RAM 43 and executes it.

  An image frame is input from the OS processing unit 30 to the video analysis processing unit 40 via the input I / F 44. Further, an image frame is output to the liquid crystal display panel timing generation unit 50 via the output I / F 45, and information indicating the turn-off start time and turn-off time of each of the light source units 5a to 5h, and the light source unit 5a are output to the backlight control unit 70. Information indicating the magnitude of each of the driving currents of ~ 5h is output.

  The ROM 42 includes an LUT (Look Up Table) 42a indicating the relationship between a gradation change described later and a response time corresponding to the gradation change, a turn-off start time, a turn-off time, and the magnitude of the drive current. In the ROM 42, storage areas 420, 421,... Are set for each image frame sequentially input from the OS processing unit 30. The storage areas 420, 421,... Include segments corresponding to the first part 1a to the eighth part 1h described above.

  The MPU 41 divides the image frame and stores it in each segment of the storage area. Then, the MPU 41 obtains a gradation change between sequentially input image frames for each segment, calculates a response time based on the obtained gradation change, and calculates the turn-off start time, the turn-off time, and the magnitude of the drive current. Information is generated and output to the backlight control unit 70.

  For example, the MPU 41 divides information indicating one image related to the input image frame so as to correspond to the first portion 1a to the eighth portion 1h, and stores the divided information in the segments 420a to 420h of the storage area 420. . Further, an image frame indicating another image displayed on the liquid crystal display panel 1 next to one image is divided corresponding to each of the first portion 1a to the eighth portion 1h, and the divided image frames are stored in the storage areas 421. Store in segments 421a-421h.

  Based on the image frames stored in the segments 420a to 420h, the MPU 41 is a gradation of a partial image (first partial image) constituting one image displayed in each of the first part 1a to the eighth part 1h. Is calculated for each of the first part 1a to the eighth part 1h. Further, based on the image frames stored in the segments 421a to 421h, the gradations of partial images (second partial images) constituting other images displayed in the first part 1a to the eighth part 1h, respectively, Calculation is performed for each of the first part 1a to the eighth part 1h. Then, for each of the first part 1a to the eighth part 1h, the gradation change of the corresponding first partial image and second partial image is obtained.

  Next, the MPU 41 refers to the LUT 42a, determines the response time corresponding to the obtained gradation change, acquires the turn-off start time, the turn-off time, and the magnitude of the drive current from the determined response time, Information indicating the turn-off time and the magnitude of the drive current is output to the backlight control unit 70. The LUT 42a stores, for example, information indicating that the turn-off start time becomes earlier as the response time becomes smaller for each of the first portion 1a to the eighth portion 1h, and the drive current increases as the response time becomes larger. Stores information indicating that the size increases.

  Note that the above processing for calculating the response time based on the gradation change and outputting information indicating the magnitude of the light extinction start time, the light extinction time, and the drive current to the backlight control unit 70 is the light extinction start time, the light extinction time, and the drive current. It is an example of the process which outputs the information which shows the magnitude | size to the backlight control part 70, Comprising: It is not limited to this.

  For example, as shown by a broken line in FIG. 6, each segment of the ROM 42 is divided into units S corresponding to image areas to be described later so that image frames can be distinguished, and an extraction to be described later is performed in the LUT 42a. Information indicating the relationship between the maximum gradation change and its response time, the start time of turn-off, the turn-off time, and the magnitude of the drive current may be stored, and the following processing may be performed.

  The MPU 41 recognizes the image frames stored in the segments 420a to 420h for each unit S, and calculates the gradation of the image related to the unit S. The unit S corresponds to an image area composed of a predetermined number of pixels.

  The MPU 41 corresponds to the image area related to the unit S included in the segment 420a and the unit S included in the segment 420a, and changes the gradation between the image area related to the unit S included in the segment 421a. Calculation is performed for each S, and a gradation change that requires the most time for transition of the liquid crystal element, that is, a gradation change having the longest response time is extracted. For example, when the magnitude of the gradation change corresponds to the response time, the maximum gradation change is extracted. Note that the gradation change to be extracted may be a gradation change with the longest response time. The MPU 41 similarly performs such extraction processing for the other segments 420b to 420h and 421b to 421h. Note that when the unit S corresponds to an image region composed of a single pixel, the gradation change is calculated for each pixel.

  Then, the MPU 41 refers to the LUT 42a, determines the response time corresponding to the extracted gradation change, acquires the turn-off start time, the turn-off time, and the magnitude of the drive current from the determined response time, and turns off the turn-off start time and the turn-off time. Information indicating the time and the magnitude of the drive current is output to the backlight control unit 70.

  Next, the configuration of the light source driving circuit 71 will be described. FIG. 7 is a block diagram schematically showing the light source driving circuit 71. The light source driving circuit 71 includes counters 75a to 75h corresponding to the light source units 5a to 5h, pulse generation circuits 76a to 76h, and LED drivers 77a to 77h having constant current circuits. The counters 75a to 75h, the pulse generation circuits 76a to 76h, and the LED drivers 77a to 77h are connected in series in this order.

The LED drivers 77a to 77h can turn on / off the light source units 5a to 5h and change the drive current based on a control signal input via an I ² C (Inter-Integrated Circuit) bus or the like. The LED drivers 77a to 77h are connected to the light source units 5a to 5h, and a power source 80 is connected to the light source units 5a to 5h.

Information indicating the magnitude of the drive current corresponding to each of the light source units 5a to 5h acquired from the video analysis processing unit 40 is a constant current of the LED drivers 77a to 77h according to a control signal input via the I ² C bus or the like. For example, a drive current having a magnitude of E1 or E2 (see FIG. 8) described later is set. In addition, a lighting period and an extinguishing period are determined by a PWM (Pulse Width Modulation) signal output from the pulse generation circuits 76a to 76h, and the light source units 5a to 5h are turned on or off.

  The counters 75a to 75h receive the horizontal synchronization signal HS from the liquid crystal display panel timing generation unit 50, and also receive the vertical synchronization signal VS from the liquid crystal display panel timing generation unit 50 via a frequency divider (not shown). Yes. In addition, the counters 75a to 75h have a period from when the vertical synchronization signal VS is input to the counters 75a to 75h based on the information indicating the turn-off start time and the turn-off time acquired from the video analysis processing unit 40. The number of pulses of the horizontal synchronization signal HS to be counted (hereinafter referred to as the first count number) and the number of pulses of the horizontal synchronization signal HS to be counted from the start of turning off to the end of turning off (hereinafter referred to as the second count number). Is called count number).

  The counters 75a to 75h count the number of pulses of the horizontal synchronization signal HS using the input of the vertical synchronization signal VS as a trigger. The counters 75a to 75h output the first signal to the pulse generation circuits 76a to 76h when the first count is finished after the vertical synchronization signal VS is input. The counters 75a to 75h output the second signal to the pulse generation circuits 76a to 76h when the second count number is counted after the first count number is counted.

  When the first signal is input from the counters 75a to 75h, the pulse generation circuits 76a to 76h output a low level signal to the LED drivers 77a to 77h. The LED drivers 77a to 77h are turned off when a low level signal is input, the current is cut off, and the light source units 5a to 5h are turned off.

  On the other hand, when the second signal is input from the counters 75a to 75h, the pulse generation circuits 76a to 76h output a high level signal to the LED drivers 77a to 77h. The LED drivers 77a to 77h are turned on when a high level signal is input, and the current set in the constant current circuits of the LED drivers 77a to 77h flows to the light source units 5a to 5h, and the light source units 5a to 5h. Lights up.

  FIG. 8 is a timing chart showing the relationship between the vertical synchronization signal VS and the LED drivers 77a to 77h. FIG. 8A shows a pulse wave of the vertical synchronization signal VS, and V shown in FIG. 8A represents a cycle of the pulse wave. FIG. 8B shows the on and off states of the LED drivers 77a to 77h, where H shown in FIG. 8B represents the on state and L represents the off state. The height of the waveform in FIG. 8B indicates the magnitude of current supplied from the power supply 80 to the light source units 5a to 5h. FIG. 8B shows, as an example, an on state or an off state of the LED drivers 77a, 77b, 77c, and 77h.

  In FIG. 8B, a waveform 200 indicating the on state and the off state of 77a and 77h indicates a waveform when the response time before and after the transition is early when the image displayed on the liquid crystal display panel 1 transitions. A broken line 150 indicates the on-state timing and the off-state timing when the response time is medium. When the response time is early, the light source units 5a and 5h are compared to when the response time is medium. The point in time when the light source starts to turn off is a predetermined time earlier, and the point in time when the light source units 5a and 5h are turned on after the light is turned off is also advanced by the same time. Note that Pa indicates the off-state time in the waveform 200, and Pb indicates the on-state time in the waveform 200. In this example, Pa and Pb indicate substantially the same time. E1 indicates the magnitude of the drive current when the light source units 5a and 5h are driven at the timing indicated by the waveform 200. The transition time of the image corresponds to the transition time of the liquid crystal element.

  In FIG. 8B, a waveform 201 indicating the on state and the off state of 77b and 77c indicates a waveform when the response time before and after the transition is slow when the image displayed on the liquid crystal display panel 1 transitions. Note that Qa represents the off-state time in the waveform 201, Qb represents the on-state time in the waveform 201, and Qa is longer than Qb. That is, when the response time before and after the transition is slow, the turn-off time of the light source units 5b and 5c is longer than the turn-on time.

  E2 indicates the magnitude of the drive current when the light source units 5b and 5c are driven at the timing indicated by the waveform 201, and is larger than E1. The brightness of the light source units 5b and 5c at the time of lighting is normally darker as the turn-off time becomes longer. However, since the drive current E2 is larger than E1, the second part 1b and the third part corresponding to the light source units 5b and 5c. The luminance of 1c does not decrease compared to the luminance of the first portion 1a and the eighth portion 1h corresponding to the light source units 5a and 5h, and the luminance of the entire liquid crystal display panel 1 can be made uniform.

  FIG. 9 is a schematic diagram illustrating the response characteristics of the liquid crystal display panel 1 when the response time before and after the transition is fast when the image displayed on the liquid crystal display panel 1 transitions. The horizontal axis is an axis indicating the holding time for which the image is held in the liquid crystal display panel 1, and the vertical axis is an axis indicating the gradation.

  FIG. 9A shows the response characteristics of the liquid crystal display panel 1 when the gradation of the image becomes higher after the transition, and 300 is a characteristic curve showing the response characteristics. FIG. 9B shows the response characteristic of the liquid crystal display panel 1 when the gradation of the image becomes low after the transition, and 301 is a characteristic curve indicating the response characteristic. 9A and 9B show a waveform 200. FIG.

  As shown in FIGS. 9A and 9B, when the response time before and after the transition is fast, the characteristic curves 300 and 301 are rapidly increased or decreased from the current gradation toward the target gradation, and the target gradation is short-time. To reach. As shown in FIG. 8B described above, when the response time before and after the transition is early, the point in time when the light source units 5a to 5h start to turn off is advanced by a predetermined time. Therefore, as shown by the waveform 200, the light source units 5a to 5h are extinguished immediately after the change of the gradation from the current gradation toward the target gradation in the first part 1a to the eighth part 1h, and the target is turned off. Lights after the gradation is reached. For this reason, while the image is changing in the first part 1a to the eighth part 1h, the user does not visually recognize the image and can prevent the generation of the pseudo contour.

  FIG. 10 is a schematic diagram illustrating the response characteristics of the liquid crystal display panel 1 when the response time before and after the transition is slow when the image displayed on the liquid crystal display panel 1 transitions. The horizontal axis is an axis indicating the holding time for which the image is held in the liquid crystal display panel 1, and the vertical axis is an axis indicating the gradation.

  FIG. 10A shows the response characteristics of the liquid crystal display panel 1 when the gradation of the image becomes higher after the transition, and 302 is a characteristic curve showing the response characteristics. FIG. 10B shows the response characteristic of the liquid crystal display panel 1 when the gradation of the image becomes low after the transition, and 303 is a characteristic curve indicating the response characteristic. Also, a waveform 201 is shown in FIGS. 10A and 10B.

  As shown in FIGS. 10A and 10B, when the response time before and after the transition is slow, the characteristic curves 302 and 303 gradually increase or decrease from the current gradation toward the target gradation and reach the target gradation. Takes a long time. As shown in FIG. 8B described above, when the response time before and after the transition is slow, the turn-off time Qa of the light source units 5a to 5h is longer than the turn-on time Qb. Therefore, as indicated by the waveform 201, the light source units 5a to 5h are turned off and turned off immediately after the first part 1a to the eighth part 1h start to change from the current gradation to the target gradation. Lights after time Qa has elapsed. For this reason, the user does not visually recognize an image until the transition of the image is almost completed in the first part 1a to the eighth part 1h, and the generation of the pseudo contour can be suppressed.

  In the liquid crystal display device according to the embodiment, gradation change between one image sequentially displayed and another image in the first portion 1a to the eighth portion 1h facing the light source units 5a to 5h. The response time corresponding to is calculated. Then, based on the calculated response time, the light source units 5a to 5h are set to the turn-off start time and the turn-off time. While the arrangement state of the liquid crystal elements is changed in the first portion 1a to the eighth portion 1h, Since the light source units 5a to 5h are turned off, even when the response time of the liquid crystal display panel 1 varies from part to part, generation of pseudo contours can be prevented and display quality can be improved.

  In addition, a response time is calculated based on the gradation change, a turn-off time is determined according to the calculated response time, a drive current of the light source units 5a to 5h is controlled according to the determined turn-off time, and liquid crystal Uniform brightness can be promoted throughout the display panel 1.

  In each of the first part 1a to the eighth part 1h, when the set turn-off time is long, the drive current at the time of lighting is increased to increase the luminance of the light source unit, and when the set turn-off time is short, when the light is turned on The luminance of the light source unit is reduced by reducing the driving current at, so that the luminance is uniform while one image is held on the liquid crystal display panel 1.

  In addition, the gradations of the first partial image and the second partial image displayed in the first part 1a to the eighth part 1h are obtained, and the light source units 5a to 5a are obtained based on the response times corresponding to the obtained gradation changes. The lighting start time and the lighting time for 5 h are set, and the luminance of the entire liquid crystal display panel 1 is made uniform.

  Further, the gradation change of the first partial image and the second partial image displayed in the first part 1a to the eighth part 1h is obtained for each corresponding image area, and a predetermined magnitude is obtained from each of the obtained gradation changes. The gradation change is extracted. For example, when the magnitude of the gradation change corresponds to the length of the response time, the maximum gradation change is extracted, and based on the response time (longest response time) corresponding to the extracted gradation change, the light source units 5a to 5a. A light-off start time and a light-off time of 5h are set, and the light source units 5a to 5h are turned off until the response of the liquid crystal element is completed in the first part 1a to the eighth part 1h. Note that the gradation change to be extracted may be a gradation change with the longest response time.

  The embodiment described above is an exemplification of the present invention, and the present invention can be implemented in variously modified forms within the scope determined based on the description of the claims.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel 1a-1h 1st part-8th part 5a-5h Light source unit (light source)
DESCRIPTION OF SYMBOLS 10 Image | video process part 20 Double speed process part 30 OS process part 40 Image | video analysis process part 50 Liquid crystal display panel timing generation part 70 Backlight control part 71 Light source drive circuit

The liquid crystal display device according to the present invention includes a liquid crystal display panel that displays sequentially input images, and a plurality of light sources that are arranged in parallel to face the liquid crystal display panel and emit light toward the liquid crystal display panel. In the liquid crystal display device in which the plurality of light sources are intermittently lit during a display period in which the input image is displayed on the liquid crystal display panel, each of the portions of the liquid crystal display panel facing each light source Based on the gradation change of the first partial image in the displayed one image and the second partial image in the next sequential image, the response time calculating means for calculating the response time and the response time calculating means depending on the late / early response time, and characterized in that it comprises a turn-off period setting means for setting a turn-off period of the light source in the display period to slow to / faster the off start time of the light source That.

In the present invention, in each part of the liquid crystal display panel facing the light source, the response time of the liquid crystal display panel corresponding to the change in gradation between one image displayed sequentially and the other image is calculated and calculated. Based on the response time, an extinguishing period of the light source is set, and the light source is extinguished while the arrangement state of the liquid crystal elements is changed in the portion of the liquid crystal display panel. Also, the light source turn-off start time is delayed / accelerated according to the response time delay / early.

Claims (5)

A liquid crystal display panel that displays images that are sequentially input, and a plurality of light sources that are arranged in parallel to face the liquid crystal display panel and emit light toward the liquid crystal display panel. In the liquid crystal display device in which the plurality of light sources are intermittently lit during a display period in which an image is displayed on the liquid crystal display panel.
Response time calculation for calculating a response time based on the gradation change of the first partial image in one image and the second partial image in the next image displayed on each of the liquid crystal display panels facing each light source. Means,
A liquid crystal display device comprising: an extinguishing period setting unit that sets an extinguishing period of the light source in the display period based on the response time calculated by the response time calculating unit.   The liquid crystal display device according to claim 1, wherein the response time calculating unit calculates a change in gradation of the first partial image and the second partial image. The response time calculating means includes
The gradation change between each of the plurality of image areas constituting the first partial image and each of the plurality of image areas constituting the second partial image corresponding to the plurality of image areas constituting the first partial image, Means for obtaining corresponding image areas;
The liquid crystal display device according to claim 1, further comprising: means for extracting a maximum value of response time based on a plurality of gradation changes obtained by the means. 4. The apparatus according to claim 1, further comprising a current value control unit configured to control a driving current of the light source facing the facing portion based on the response time calculated by the response time calculating unit. Liquid crystal display device described in 1. 5. The liquid crystal display device according to claim 4, wherein the current value control unit is configured to increase or decrease a drive current according to the length of the extinguishing period set by the extinguishing period setting unit.

Images