JP2013029691A - Image output device and backlight control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which reduces degradation of display at the time of failure by correcting an image on the basis of failure information of a backlight.SOLUTION: An image output device includes: a backlight unit which irradiates an image display unit from the back or the side and transmits failure information; a lighting amount determination unit which receives the failure information to determine a lighting amount of the backlight unit; and a pixel correction unit which corrects pixels with respect to the image display unit on the basis of the lighting amount. In a backlight control method for an image output device including a backlight unit which irradiates an image display unit displaying an image based on image frames, from the back or the side, the backlight unit transmits failure information, and the failure information is received to determine a lighting amount of the backlight unit, and pixels are corrected with respect to the image display unit on the basis of the lighting amount.

Description

  Embodiments described herein relate generally to a video output device and a backlight control method.

  In recent years, a video output device using an LCD panel using LEDs (light emitting diodes) as a backlight for illuminating a liquid crystal display (LCD) from the back has been developed. According to such a video output device using an LED for the backlight, it is possible to realize a video with a high contrast ratio by performing dimming that increases or decreases the light emission luminance of the backlight in accordance with the video.

  In particular, a technique of local dimming has been used. For example, Patent Document 1 proposes basic local dimming and determines lighting of a backlight from video information.

  In addition, as a countermeasure for failure, there is also a proposal to achieve uniformity by partially turning off the light uniformly including the non-failed blocks and increasing the amount of light in the remaining blocks when the backlight fails (for example, patents) Reference 2).

  However, the control target is not limited to the backlight, but there is a request to correct the image based on the failure information to alleviate the display failure at the time of the failure. Means for realizing such a request is known. Absent.

Japanese Patent Laying-Open No. 2005-92184 (Claim 1, FIG. 5) JP 2003-338387 A

  An object of the embodiment of the present invention is to provide a technique for correcting an image based on backlight failure information and mitigating display failure at the time of failure.

  In order to solve the above-described problem, according to the embodiment, the video output device includes a backlight unit that emits failure information by irradiating the video display unit from the back surface or the side surface, and a lighting amount of the backlight unit that receives the failure information. And a pixel correction unit that corrects the pixels of the video display unit based on the lighting amount.

1 is an external perspective view showing an example of a digital television according to an embodiment of the present invention. The block block diagram which shows the signal processing system of the digital television of the embodiment. Explanatory drawing when a failure arises in a backlight by the local dimming process of the point 1 of the embodiment. Explanatory drawing when a failure occurs in the backlight in the local dimming process of point 2 of the embodiment. The figure which shows the flowchart of the lighting amount determination part A of the point 1 used for embodiment. The figure which shows the flowchart of the lighting amount determination part B of the point 2 of embodiment.

Hereinafter, embodiments will be described.
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is an external perspective view showing an example of a digital television 1 which is a video output apparatus according to the first embodiment. As shown in FIG. 1, the digital television 1 has a rectangular appearance when viewed from the front (when viewed from the front). The digital television 1 includes a housing 2 and an LCD (Liquid Crystal Display) panel 3. The LCD panel 3 receives a video signal from a video processing unit 20 (see FIG. 2) described later, and displays a video such as a still image or a moving image. The housing 2 is supported by the support portion 4. The LCD panel 3 may be configured to be externally attached or a separate housing.

  FIG. 2 is a block diagram showing a signal processing system of the digital television 1. The digital television 1 not only performs video display based on a normal planar (two-dimensional) display video signal, but also performs video display based on a stereoscopic (three-dimensional) display video signal. It may be configured to be able to.

  As shown in FIG. 2, the digital television 1 selects a broadcast signal of a desired channel by supplying the digital television broadcast signal received by the antenna 12 to the tuner unit 14 via the input terminal 13. It is possible. The digital television 1 supplies the broadcast signal selected by the tuner unit 14 to the demodulation / decoding unit 15 and restores it to a digital video signal, an audio signal, etc., and then outputs it to the signal processing unit 16.

  The signal processing unit 16 performs predetermined digital signal processing on the digital video signal and audio signal supplied from the demodulation / decoding unit 15. The predetermined digital signal processing performed by the signal processing unit 16 includes processing for converting a normal planar (two-dimensional) display video signal into a stereoscopic (three-dimensional) display video signal, and stereoscopic display. The process etc. which convert the video signal for video into the video signal for planar view display are included.

  The signal processing unit 16 outputs a digital video signal to the synthesis processing unit 17 and outputs a digital audio signal to the audio processing unit 18. Among them, the composition processing unit 17 superimposes subtitles, GUI (Graphical User Interface), OSD, and the like generated by the OSD (On Screen Display) signal generation unit 19 on the digital video signal supplied from the signal processing unit 16. An OSD signal that is a video signal for use is superimposed and output. In this case, if the video signal supplied from the signal processing unit 16 is a video signal for normal planar view display, the synthesis processing unit 17 uses the OSD signal supplied from the OSD signal generation unit 19 as it is. It is superimposed and output. In addition, when the video signal supplied from the signal processing unit 16 is a video signal for stereoscopic display, the synthesis processing unit 17 receives the input stereoscopic video from the OSD signal supplied from the OSD signal generation unit 19. After performing the stereoscopic display signal processing corresponding to the display video signal, the OSD signal is superimposed on the input video signal and output.

  The digital television 1 supplies the digital video signal output from the synthesis processing unit 17 to the video processing unit 20. The video processing unit 20 outputs the input digital video signal and backlight control signal. In the LCD panel 3, these are converted into analog video signals in a displayable format by an internal timing controller (not shown). The digital television 1 supplies a signal from the video processing unit 20 to the LCD panel 3 for video display.

  As shown in FIG. 2, the LCD panel 3 includes an LCD 3a that functions as an image display unit, a backlight 3b that irradiates the LCD 3a from the back surface, and a backlight driving unit 3c that drives the backlight 3b. The backlight 3b employs a large number of LEDs (light emitting diodes) as a light source, and light emission control for each area is possible by the backlight driving unit 3c. The backlight unit includes a backlight 3b and a backlight drive unit 3c.

  The audio processing unit 18 converts the input digital audio signal into an analog audio signal in a format that can be reproduced by the speaker 22. The analog audio signal output from the audio processing unit 18 is supplied to the speaker 22 for audio reproduction.

  Here, the digital television 1 comprehensively controls all the operations including the above-described various reception operations by the control unit 23. The control unit 23 incorporates a CPU (Central Processing Unit) 23a, receives operation information from the operation unit 24 installed in the main body of the digital television 1, or is sent from the remote controller 25 and receives the reception unit.

In response to the operation information received at 26, each unit is controlled so that the operation content is reflected.
The control unit 23 uses the memory unit 23b. The memory unit 23b mainly includes a ROM (Read Only Memory) storing a control program executed by the CPU 23a, a RAM (Random Access Memory) for providing a work area to the CPU 23a, various setting information, control information, and the like. Is stored in a non-volatile memory. Further, a disk drive unit 27 is connected to the control unit 23. The disk drive unit 27 is a unit that allows an optical disk 28 such as a DVD (Digital Versatile Disk) to be detachable, and has a function of recording / reproducing digital data on the mounted optical disk 28.

  The control unit 23 encrypts the digital video signal and audio signal obtained from the demodulation / decoding unit 15 by the recording / playback processing unit 29 based on the operation of the operation unit 24 and the remote controller 25 by the viewer, and puts it into a predetermined recording format. After the conversion, it can be controlled to be supplied to the disk drive unit 27 and recorded on the optical disk 28.

  Further, the control unit 23 causes the disc drive unit 27 to read out digital video signals and audio signals from the optical disc 28 based on the operation of the operation unit 24 and the remote controller 25 by the viewer, and the recording / playback processing unit 29 After decoding, the signal is supplied to the signal processing unit 16 so that it can be controlled to be used for the video display and the audio reproduction described above.

  An HDD (Hard Disk Drive) 30 is connected to the control unit 23. The control unit 23 encrypts the digital video signal and audio signal obtained from the demodulation / decoding unit 15 by the recording / playback processing unit 29 based on the operation of the operation unit 24 and the remote controller 25 by the viewer, and puts it into a predetermined recording format. After the conversion, it can be controlled to be supplied to the HDD 30 and recorded on the hard disk 30a.

  Further, the control unit 23 causes the HDD 30 to read out digital video signals and audio signals from the hard disk 30 a based on the operation of the operation unit 24 and the remote controller 25 by the viewer, and decodes them by the recording / reproduction processing unit 29. By supplying the signal to the signal processing unit 16, it can be controlled to be used for the video display and the audio reproduction described above.

  Furthermore, an input terminal 31 is connected to the digital television 1. The input terminal 31 is for directly inputting digital video signals and audio signals from the outside of the digital television 1. The digital video signal and audio signal input via the input terminal 31 are supplied to the signal processing unit 16 through the recording / reproducing processing unit 29 based on the control of the control unit 23, and thereafter For video display and audio playback.

  Further, the digital video signal and audio signal input through the input terminal 31 pass through the recording / playback processing unit 29 based on the control of the control unit 23, and then are applied to the optical disk 28 by the disk drive unit 27. It is used for recording / reproduction and recording / reproduction for the hard disk 30 a by the HDD 30.

  The control unit 23 receives digital video signals and audio signals recorded on the optical disk 28 between the disk drive unit 27 and the HDD 30 based on the operation of the operation unit 24 and the remote controller 25 by the viewer. It also controls recording on the optical disc 28 and recording of digital video signals and audio signals recorded on the hard disk 30a.

  A network interface 32 is connected to the control unit 23. The network interface 32 is connected to an external network 34 via an input / output terminal 33. The network 34 is connected to a plurality (two in the illustrated case) of network servers 35 and 36 for providing various services using the communication function via the network 34. Therefore, the control unit 23 accesses the desired network servers 35 and 36 via the network interface 32, the input / output terminal 33 and the network 34 to perform information communication, thereby using the service provided there. Be able to.

  The digital television 1 operates the playback stop key and playback / pause key of the remote controller 25 for information such as video and audio acquired from the disk drive unit 27 and the HDD 30 to play, stop, and pause. It is possible to stop. In addition, the digital television 1 operates the backward skip key or the forward skip key of the remote controller 25 to thereby display information such as video and audio reproduced on the disk drive unit 27 and the HDD 30 in the reproduction direction. On the other hand, it is possible to perform so-called reverse skip or forward skip, in which a predetermined amount is skipped in the reverse direction or the forward direction. Furthermore, the digital television 1 operates the fast reverse key, fast forward key, and the like of the remote controller 25 to display information such as video and audio reproduced on the disk drive unit 27 and the HDD 30 in the reproduction direction. It is possible to perform so-called fast-rewind playback and fast-forward playback, in which playback is performed at high speed continuously in the reverse direction or forward direction.

(Existing technology)
First, basic local dimming processing will be described as an existing technique.
This technology is implemented as one of the functions of video display devices such as TV and PC displays, especially a liquid crystal display with a backlight. By suppressing unnecessary lighting, power consumption is reduced and screen contrast is greatly increased. Has the effect of improving.

  The input video information is pixel value information (RGB, YCbCr, etc.) of each pixel in the screen, and may be a signal received by a tuner or the like or other externally input signal if it is a TV.

  In the existing local dimming, the lighting amount determining unit determines the lighting amount for each backlight area based on this video information. As a determination method, the luminance necessary for displaying a target video for each region is determined by measuring a histogram, a peak luminance, or the like. For example, if the pixels in or near the area are only dark, the lighting amount may be a small value, and if the pixel includes a high luminance, the lighting amount is set to a large value.

  The number and position of the backlight areas are physically determined by the backlight used, and the backlight control unit controls the backlight according to the lighting amount.

  Here, if only the brightness of the backlight is controlled, when the liquid crystal is illuminated with the backlight, the original video information may be disturbed due to variations in brightness for each area, Depending on the luminance difference of the pixels, a portion where the intended luminance and color can be reproduced and a portion where it cannot be reproduced are generated. For this reason, the video information is not directly displayed on the liquid crystal via the timing controller unit, but must be corrected in accordance with the luminance of the backlight.

  For example, if the backlight brightness is maximum, the video information can be displayed correctly without any correction, but if the backlight brightness decreases, the original video information should be Compared to Therefore, by correcting the pixel value to a value larger than the original video information, the aperture of the liquid crystal is widened to increase the transmittance of the irradiation light from the backlight. This makes it possible to obtain the luminance that a pixel should display.

  The backlight control is a lighting amount control for each area, but the brightness of the backlight actually obtained is not always uniform in the area even if the difference in the aperture ratio of the liquid crystal is ignored. This is because there is leaked light that leaks between regions in order to avoid a sudden change in luminance at the region boundary.

The pixel unit backlight luminance estimation unit estimates the luminance of the backlight in pixel units in consideration of the lighting amount for each region and the leakage light between the regions, and outputs it to the pixel correction unit.
The pixel correction unit corrects the video information in units of pixels using the luminance estimation value received from the pixel unit backlight luminance estimation unit.
The corrected video information is transmitted to the liquid crystal via the timing controller unit, and the aperture (transmittance) of each pixel is adjusted.
Here, what is important is that the pattern of one screen of the actual luminance of the backlight matches the pattern of one screen of the estimated luminance value used for pixel correction. If they match, a good local dimming image is obtained. If they do not match, incorrect pixel correction is performed, and the image is distorted.

(Problems with existing technology)
Next, as a problem of the existing technology, a situation that occurs when a failure occurs in the backlight will be described.
The backlight is composed of a lamp, an LED, or the like for each region, and emits light with a relatively high voltage and high luminance. Therefore, the backlight often generates heat, which is one cause of failure. Even if there is no physical damage depending on the backlight control unit, overheating or the like may be detected, and the corresponding area may be turned off to prevent failure in advance. Regardless of the type of cause, if an area with a backlight breaks down, that is, it cannot emit light, the backlight is lit in a part of the lighting state that is different from the value determined by the lighting amount determination unit according to the video information. Become. As a result, the luminance estimated value pattern in pixel units obtained from the lighting amount does not match the actual luminance pattern of the backlight. As a result, the following problem occurs, and there is a high possibility that the image is disturbed.

(A) Insufficient brightness cannot be obtained in the area where the failure occurred (the degree depends on the required brightness and the state of ambient light leakage)
(B) Incorrect correction that does not match the luminance pattern of the backlight is performed. For example, when local dimming is performed according to the video information, the area of the failure portion is lit with high luminance, and other areas are illuminated. When the lighting amount is determined so as to be turned off, the failure of (a) is remarkable.

(Solution)
In this embodiment, the problem of the existing technique is solved by point 1 described later. This will be described based on FIG. 3 and FIG. FIG. 3 is a functional block diagram of the present embodiment.

  This block includes a pixel correction unit C, a pixel unit backlight luminance estimation unit L, a timing controller unit T, a liquid crystal LQ, a lighting amount determination unit A, a backlight control unit BC, and a backlight BL.

These functions are shared by the video processing unit 20, the control unit 23, the video display unit 3a, the backlight units 3b and 3c, and the like.
FIG. 5 is a flowchart illustrating the process of the lighting amount determination unit A for the operation of point 1. First, in this embodiment, when a failure does not occur, an operation similar to that of the existing technology is performed.

  Next, when a failure occurs in the backlight BL, the backlight BL according to the present embodiment has means for detecting the failure and notifying the backlight control unit BC of the failure information. The failure information includes at least information indicating which region has failed.

  The failure information is passed to the lighting amount determination unit A through the backlight control unit BC. It is important that the failure information is passed to the lighting amount determination unit A. Depending on the configuration of the device, the configuration may be such that the lighting amount determination unit A is notified directly from the backlight BL without passing through the backlight control unit BC. .

  As shown in the flowchart of FIG. 5, the lighting amount determination unit A first receives failure information (step S1), determines whether a failure has occurred, and branches the process (step S2). If no failure has occurred, video information is acquired as a normal local dimming operation (step S3), and the lighting amount for each region is determined from the video information (step S4). On the other hand, if a failure has occurred, the amount of lighting in the failed area is turned off to the lowest extinction state, and the other areas are turned on to the maximum luminance (step S5). The reason why the other areas are set to the maximum brightness is that it is expected that the brightness can be obtained also at the failure location by the leaked light. This lighting amount may be a value set in advance instead of the maximum luminance.

The lighting amount determined in this way is transmitted to the backlight control unit BC both during normal operation and when a failure is detected, and the backlight is turned on with a specified luminance.
Similarly, the determined lighting amount is also notified to the pixel unit backlight luminance estimation unit L. The operation of the backlight luminance estimation unit L is the same during normal operation and when a failure is detected, but the value notified at the time of failure detection is that the failure location is turned off, and the actual luminance of the backlight is A matching luminance estimate is generated.

  The operation of the pixel correction unit C is the same during normal operation and when a failure is detected. The image information for one screen is corrected in pixel units using the corresponding luminance estimated value for one screen.

  The corrected video information is transmitted to the liquid crystal via the timing controller to control the pixel aperture. By these processes, the problem (a) of the existing technology is greatly alleviated and (b) is solved.

  In order for (a) to be sufficiently solved by this method, it is necessary to obtain sufficient luminance in the area of the failure location with ambient leakage light, which depends on the characteristics of the backlight. However, for any backlight in the presence of leakage light, relaxation can be expected for (a) by the proposed solution.

  With this point 1, it is possible to mitigate image quality degradation when a backlight failure occurs. Point 1 is a general and stable method that can handle various failure patterns as compared with point 2 described below.

(Second Embodiment)
A second embodiment will be described with reference to FIGS. Description of the parts common to the first embodiment is omitted.
FIG. 4 is a block diagram of the proposal. FIG. 6 is a flowchart for explaining the processing of the lighting amount determination unit B in the operation of point 2 described later.
Point 2 is a point in which local dimming processing omitted for simplification of processing coexists with point 1 of the first embodiment. At the time of failure information detection, local dimming is always performed with respect to point 1 where video information is not used for determining the lighting amount, at point 2 regardless of whether normal operation or failure information is detected. Further, when failure information is detected, the lighting amount is redetermined taking into account the failure location.

The difference from the processing and configuration point 1 is only the lighting amount determination unit B, and the other points are the same, and the description is omitted.
As shown in the flowchart of FIG. 6, the lighting amount determination unit B at point 2 first acquires video information as a local dimming operation (step S11), and determines the lighting amount for each region from the video information (step S12). Next, failure information is received (step S13), it is determined whether a failure has occurred, and the process branches (step S14). If no failure has occurred, the determined lighting amount is output as it is (step S16). On the other hand, if a failure has occurred, the lighting amount of the faulty area is set to the lowest extinction state, and instead the lighting amount reduced in the faulty area is distributed (added) to the surrounding area (step) S15). The surrounding area here is basically an area adjacent to the failed area, but it may be regarded as the surrounding area as long as it is an area where leaked light reaches. In the distribution of the lighting amount, the lighting amount required in the failure area calculated in the initial lighting amount determination is basically used as a reference, but the total lighting amount distributed around is the same as the lighting amount required in the failure area. Since the brightness may be insufficient if it is simply selected, the necessary lighting amount will be multiplied several times and then distributed or multiplied by the gain according to the positional relationship with the failed area according to the leakage light pattern. It may be added to these areas.

  By these processes, the problems of the existing technology are improved in the same manner as point 1, and local dimming is applied as much as possible, so that reduction of power consumption and improvement of contrast can be expected.

Point 2 can alleviate the deterioration of image quality when a backlight failure occurs and can also use the existing local dimming effect.
The video display apparatus having the following components has been described above.
(1) A backlight which is located on the back surface of the video display device (unit) and irradiates the liquid crystal screen from the back surface (or from the edge), and is divided into a plurality of regions and can be controlled individually. Has the function of notifying that the block is unlit or unsuitable for lighting (failure information)

(2) A backlight control unit that controls lighting of the backlight according to the lighting amount indicated by the lighting amount determination unit, and has a function of feeding back failure information generated in the backlight to the lighting amount determination unit.

(3-1) The lighting amount determination unit that determines and outputs the lighting amount of each block of the backlight according to the video information. When the failure information is received, the failure area is turned off without referring to the video information. Has a function to switch the calculation method to the method of determining the lighting amount so that the area of the light is lit at the maximum luminance or a predetermined luminance determined in advance

(3-2) In the lighting amount determination unit that determines and outputs the lighting amount of each block of the backlight according to the video information, upon receiving the failure information, the failure area of the lighting amount determined from the video information is turned off, A function to re-determine the lighting amount by allocating the lighting amount assigned to the failure area to the peripheral area of the failure area

(4) A pixel unit backlight luminance estimation unit that estimates the luminance of the backlight in pixel units from the lighting amount indicated by the lighting amount determination unit, and outputs the luminance to the pixel correction unit. A pixel correction unit having a function of correcting the pixel value according to the estimated value. (6) A timing controller unit for driving the liquid crystal according to the corrected video information received from the pixel correction unit. (7) For controlling the timing controller. According to the embodiment described above, the lighting amount for each region is determined based on failure information from the backlight at the time of failure. As an effect of this, it is possible to alleviate display failure at the time of failure.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can implement in various modifications. For example, this may be sensed when a part of the connection cable with the backlight BL is missing and handled in the same manner as the occurrence of a failure.

  Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements according to different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 Image | video output apparatus 3a Image | video display part 3b, 3c Backlight part 401 Dimming value production | generation part 403 Dimming value correction | amendment part 405 Division | segmentation control part

Claims (6)

A backlight unit that emits failure information by irradiating the video display unit from the back or side; and
A lighting amount determination unit that determines the lighting amount of the backlight unit in response to the failure information;
A video output device comprising: a pixel correction unit that performs pixel correction on the video display unit based on the lighting amount.   The lighting amount determination unit determines the lighting amount so that a region of the backlight unit corresponding to the failure information is extinguished and a region of the backlight unit other than this region is lit with a predetermined luminance. The video output device described.   The lighting amount determination unit extinguishes the region of the backlight unit corresponding to the failure information and determines the lighting amount assigned to this region based on the input video information to the region of the backlight unit other than this region The video output device according to claim 1, wherein the lighting amount is re-determined according to the distribution.   The video output device according to claim 1, wherein the pixel correction unit corrects a pixel by reflecting the failure information.   The video output device according to claim 1, further comprising the video display unit. A backlight control method in a video output device including a backlight unit that irradiates a video display unit that displays video based on a video frame from the back side or from a side surface,
The backlight unit emits failure information,
A backlight control method for receiving the failure information, determining a lighting amount of the backlight unit, and correcting pixels of the video display unit based on the lighting amount.

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