JP2008139840A - Image display controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously realize the adaptive light reduction of illumination and the unprecedented image correction of high accuracy for making compensation for the degradation in image quality accompanying the light reduction while achieving high speediness (real time properties), low electric power consumption, and the suppression of an increase in circuit scale. <P>SOLUTION: A correction coefficient for illumination luminance after light reduction and image correction are calculated by real time computation of a shared computing unit (218). The shared computing unit (218) is stored in a code table (216) and is controlled by a microcode. On the occasion of the image correction, the enhancement of chroma correction is implemented to suppress the degradation in the chroma due to the light reduction and the flicker is prevented by serial cyclic (IIR) filter processing. Also, even if the average luminance of the image is low, the degradation in the chroma is suppressed by limiting the light reduction of the illumination for the image of the high chroma. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image display control device and the like, and particularly corrects an image signal so as to adaptively reduce the luminance of display illumination in accordance with a display image and to compensate for a reduction in image quality due to the dimming. The present invention relates to an image display control device (image display control LSI) and the like.

  Patent Document 1 discloses a technique for adjusting image data so as to reduce the amount of light emitted from a backlight for power saving while increasing the transmittance of a liquid crystal display screen as much as possible.

Patent Document 2 describes an image correction apparatus that uses a look-up table (LUT) to correct a luminance signal of a display image.
JP-A-11-65531 JP 2004-310671 A

  In order to simultaneously perform illumination correction (backlight etc.) dimming and image correction for preventing deterioration of image quality, it is necessary to perform enormous calculations based on image data at high speed. Although there is a method of simplifying the arithmetic processing using a look-up table (LUT) storing the arithmetic results, it takes time to access the memory. Therefore, it cannot be used when high speed is required. For example, when streaming video by one-segment broadcasting (digital broadcasting for mobile phone terminals) is required to be real-time like when played back on a mobile phone terminal, a method using an LUT is not suitable.

  When a predetermined operation is performed in parallel with a plurality of dedicated hardware, high speed (real-time performance) can be ensured, but the occupied area of the circuit increases and the power consumption of the circuit increases.

  In Patent Document 1 described above, only the luminance correction is considered in the image correction for compensating for the deterioration in image quality due to the dimming of illumination. However, the saturation (color vividness) of the image is reduced by the dimming of illumination. ) Is greatly deteriorated, the image quality is greatly deteriorated. Therefore, it is necessary to perform image correction considering not only luminance but also saturation.

  In addition, if control is performed to adaptively determine the light reduction amount of illumination according to the brightness of the display image, when the brightness of the display image changes at high speed, the illumination brightness changes at high speed following this, and thus flicker occurs. This may cause the display image quality to deteriorate. In particular, when playing a streaming video, there are many scenes in which the luminance of the image changes instantaneously, which may cause flicker (visual flicker). Therefore, it is necessary to devise in order to suppress flicker accompanying a scene change.

  The present invention has been made based on such consideration. According to some aspects of the present invention, while achieving high speed (real-time performance), low power consumption, and suppression of an increase in circuit scale, adaptive dimming of illumination and image quality associated with the dimming are achieved. It is possible to simultaneously realize high-precision image correction that is not conventionally performed to compensate for the decrease.

  The image display control apparatus according to the present invention adaptively diminishes illumination for image display according to a display image, and corrects an image signal so as to compensate for a reduction in image quality due to dimming of the illumination. A control device that obtains the illumination brightness after dimming using a statistical information acquisition unit that acquires statistical information of the image signal and statistical value information of the image signal provided from the statistical information acquisition unit; , A common arithmetic unit that generates a correction coefficient used for correcting the image signal, a code storage unit that stores a plurality of codes for specifying an operation procedure of the common arithmetic unit, and a code storage unit A sequence instructing unit that controls the output order of the codes; and a code that decodes the codes output from the code storage unit and generates at least one of instructions and data to be supplied to the shared arithmetic unit Has an over da, the.

  The adaptive light reduction processing and image correction processing are realized by real-time calculation using a common arithmetic unit (shared arithmetic unit). By the calculation, the correction coefficient for image correction and the illumination brightness after dimming are calculated in real time, and image correction using the calculated correction coefficient is executed. The operation of the shared arithmetic unit is controlled by microcode that encodes the signal processing procedure. By using a common computing unit, real-time computation is possible without the need to install the same type of hardware in parallel, and high-speed dimming control and image correction can be realized with the minimum circuit and minimum power consumption. it can.

  In one aspect of the image display control apparatus of the present invention, the instructions are sequentially output from the code storage unit in the order instructed by the sequence instruction unit, and are generated as a result of decoding by the decoder. Alternatively, the data is supplied to the shared computing unit, and the shared computing unit uses the command or the data to determine the illumination luminance after the dimming and generate a correction coefficient used for correcting the image signal. When executed, the image signal corrected using the correction coefficient and a signal indicating the proof luminance after the dimming are output.

  The procedure for generating instructions (operands) and data (multiplication coefficients, etc.) supplied to the shared arithmetic unit is clarified. The code table in which microcodes are stored is pointed by the sequence instructing unit, the codes are sequentially output, the instructions and data are generated by decoding, supplied to the common arithmetic unit, and the light is reduced by the arithmetic by the common arithmetic unit Later illumination brightness and correction factors are generated and output in parallel. With the most simplified configuration, it is possible to generate the illumination brightness and the correction coefficient after dimming at high speed and efficiently.

  In another aspect of the image display control apparatus of the present invention, the shared arithmetic unit includes first and second multiplexers, an arithmetic logic unit, a distributor that distributes an arithmetic result of the arithmetic logic unit, and an existence unit. From the decoder, coefficients are supplied to the first and second multiplexers, arithmetic instructions are supplied to the arithmetic logic unit, and distribution destination information is supplied to the distributor.

  An example of a specific configuration of the shared arithmetic unit is clarified, and what instruction or data is supplied to each component is clarified. That is, in this aspect, a shared arithmetic unit is configured by a plurality of multiplexers, an arithmetic logic unit (ALU), and a distributor. Coefficients used for calculation are supplied to the multiplexer, instructions (opcodes) are supplied to the ALU, and distribution destination information is supplied to the distributor.

  In another aspect of the image display control apparatus of the present invention, the shared arithmetic unit further feeds back to the input side a plurality of output destination registers and at least some of the signals accumulated in the plurality of output destination registers. And a return path to be made.

  This clarifies that the shared arithmetic unit has a feedback path for returning the operation result to the input side. Accordingly, for example, first, the illumination brightness after dimming is obtained by the first computation process, the computation result is returned to the input side, and the correction coefficient of the image is obtained based on the obtained illumination brightness. Processing becomes possible. In addition, since the shared arithmetic unit has a feedback path, it is possible to perform a cyclic (IIR) filtering process.

  In another aspect of the image display control apparatus of the present invention, the statistical information acquisition unit acquires a statistical value of saturation in addition to a statistical value of luminance of the image signal, and uses the correction coefficient to generate the image using the correction coefficient. In the signal correction, correction for enhancing the luminance corresponding to the dimming of the illumination and correction for enhancing the saturation corresponding to the dimming of the illumination are executed.

  In image correction associated with dimming, only enhancement of luminance (expansion) may cause a decrease in image quality due to a decrease in saturation. That is, since the entire color gamut is reduced due to the dimming of illumination, it is inevitable that the saturation is also lowered. Therefore, in this aspect, image correction is performed not only for luminance expansion but also for saturation (red saturation (Cr), blue saturation (Cb)) (for example, average saturation before and after dimming is possible) Saturation correction is strengthened so that it matches as much as possible), and this prevents the image quality of vivid images from being degraded.

  In another aspect of the image display control apparatus of the present invention, the statistical information acquisition unit acquires the statistical value of the saturation in addition to the statistical value of the luminance of the image signal, and When determining the illumination brightness after dimming, from the relationship between the statistical value of the luminance and the statistical value of the saturation, it is determined whether to prioritize the dimming of the illumination or the prevention of the decrease in saturation, When priority is given to preventing the reduction of saturation, the dimming control is executed after limiting the dimming of the illumination.

  When adaptively dimming the illumination (backlight etc.) according to the statistical information of the image, if the dimming amount is determined based on only the luminance, the dimming will be excessive and red (R) or blue (B) The vividness of the image may be impaired. That is, since dark images are less affected by dimming, it is a general rule that the amount of light dimming increases. However, even if the image is dark, for example, if there is a large and bright rose flower in the center of the screen, it is reasonable to impose a limit on the amount of light that can be reduced to reduce the saturation of the rose. is there. However, since red (R) and blue (B) have a low contribution rate to luminance (Y), if they are judged only by luminance (Y), the illumination is excessively reduced based on the judgment that they are dark images. I will let you. In order to prevent such excessive dimming, dimming is determined based on not only luminance (Y) but also saturation (red saturation (Cr), blue saturation (Cb)). If the saturation satisfies a predetermined relationship, the saturation is prioritized to limit the amount of light reduction. As a result, dimming is suppressed in an image with high saturation, and reduction in saturation of the display image is suppressed.

  In another aspect of the image display control device of the present invention, the first and second cyclic types (IIR) are used for each of the correction for dimming the illumination and the correction of the image signal using the correction coefficient. ) And the time constant of the first cyclic type (IIR) filter processing for correction for dimming the illumination is the second cyclic type for correction of the image signal ( IIR) is set longer than the time constant of the filter processing.

  When adaptive illumination dimming and image correction are performed on each frame of a moving image, visual flicker occurs due to a rapid change in the illumination luminance and the image correction amount accompanying a scene change. Therefore, filter processing suitable for each characteristic is executed for both illumination correction and image correction obtained in units of frames. Since the change in illumination brightness is a change between white and black, which is easy to recognize visually, filter processing with a long time constant is applied.On the other hand, the change in image correction amount is a halftone change that is not noticeable. A filter process with a short time constant is applied with emphasis on quick response to scene changes. As a result, it is possible to effectively suppress flicker associated with adaptive illumination correction while realizing image correction following a scene change of a moving image.

  In another aspect of the image display control apparatus of the present invention, the illumination dimming including the first cyclic filter processing is performed based on at least one of the statistical value of luminance and the statistical value of saturation. Control is executed to determine the proof luminance after dimming, and then the correction of the image signal including the second cyclic filter processing is executed based on the determined illumination luminance.

  If the first cyclic filter process and the second cyclic filter process are performed independently, the balance between the illumination correction and the image correction may be lost, and the image quality may deteriorate. Therefore, the first cyclic filter processing is performed on the illumination luminance obtained in units of frames, the image correction amount is obtained from the result, and the second cyclic filter processing is performed on the image correction amount ( Serial processing). Since the image correction amount adapted to the reduced light amount is calculated after the reduced light amount of the illumination luminance is calculated, the balance between the first and second cyclic filter processing is always ensured.

  In another aspect of the image display control apparatus of the present invention, the shared arithmetic unit has a feedback path for returning at least a part of the operation result to the input side.

  It is clarified that the first and second cyclic filter processing can be executed by providing a feedback path in the shared arithmetic unit.

  In another aspect of the image display control device of the present invention, the code stored in the code storage unit adaptively reduces the illumination for image display according to a display image, and This is microcode obtained by converting the description of an algorithm in a programming language for correcting an image signal so as to compensate for the deterioration in image quality due to dimming.

  For example, an algorithm created in a high-level programming language can be batch converted to generate microcode, and written in a ROM (read only memory), thereby efficiently creating a code table. By changing the algorithm (microcode), it is possible to change the calculation contents by the shared arithmetic unit relatively easily. Therefore, it is possible to flexibly cope with design changes.

  The electro-optical device driving device of the present invention is equipped with the image display control device of the present invention.

  The image display control device (image display control LSI) of the present invention is mounted on a drive device (driver) of an electro-optical device (including a liquid crystal display device). The image display control device (image display control LSI) of the present invention has the characteristics that it can process moving images such as streaming images in real time, has excellent power saving, and can be miniaturized. Therefore, the added value of the driving device (driver) is improved.

  The control device for the electro-optical device of the present invention is equipped with the image display control device of the present invention.

  The image display control device (image display control LSI) of the present invention is mounted on a control device (controller) of an electro-optical device (including a liquid crystal display device). The image display control device (image display control LSI) of the present invention has the characteristics that it can process moving images such as streaming images in real time, has excellent power saving, and can be miniaturized. Therefore, the added value of the control device (controller) is improved.

  The drive control device for the electro-optical device of the present invention is equipped with the image display control device of the present invention.

  The image display control device (image display control LSI) of the present invention is mounted on a drive control device (device in which a driver and a controller are integrated) of an electro-optical device (including a liquid crystal display device). The image display control device (image display control LSI) of the present invention has the characteristics that it can process moving images such as streaming images in real time, has excellent power saving, and can be miniaturized. Therefore, the added value of the drive control device (device in which the driver and the controller are integrated) is improved.

  The electronic device of the present invention is equipped with the image display control device of the present invention.

  For example, by mounting the image display control device (LSI) of the present invention on a mobile terminal (including a mobile phone terminal, a PDA terminal, and a portable computer), a streaming image such as one-segment broadcasting can be displayed with high image quality. And a longer battery life can be realized.

According to at least one embodiment of the present invention, for example, the following effects can be obtained. However, the following effects are not always obtained, and the following list of effects should not be used as a basis for unduly limiting the present invention.
(1) By using a shared computing unit of the microprogram control method, real-time computation is possible without providing the same kind of hardware in parallel, and high-speed adaptive dimming control and adaptation are achieved with the minimum circuit and minimum power consumption. Image correction can be realized.
(2) It is possible to suppress a decrease in saturation by enhancing (expanding) not only the luminance but also the saturation, and more effectively compensate for a decrease in image quality due to dimming.
(3) By determining the amount of light reduction in consideration of both luminance and saturation, the amount of light reduction is limited in an image with high saturation, and a reduction in saturation due to excessive light reduction can be effectively prevented.
(4) In both dimming correction and image correction, cyclic (IIR) filter processing is executed, and the time constant of the filter processing for dimming correction is set to be longer, thereby making it possible to change the scene to a moving image. Generation of flicker (visual flicker) can be effectively suppressed while ensuring responsiveness.
(5) After calculating the light reduction amount of the illumination brightness, calculating the image correction amount adapted to the light reduction amount (adopting serial processing), thereby performing the filter processing accompanying the light control and the adjustment accompanying the image correction. A balance with light processing is always ensured.
(6) The power consumption can be significantly reduced by adaptive dimming of the illumination luminance while suppressing the deterioration of the image quality to the minimum (a reduction of up to 30% has been confirmed). In addition, since it can be realized with a minimum amount of hardware, space can be saved.
(7) It is possible to realize high added value of a drive device (driver) such as a liquid crystal display device, a control device (controller), and a drive control device (device in which a driver and a controller are integrated).
(8) By displaying the image display control device (LSI) of the present invention in a mobile terminal (including a mobile phone terminal, a PDA terminal, and a portable computer), streaming images such as one-segment broadcasting can be displayed with high image quality. In addition, the battery life can be extended. (9) A conventional technique for compensating for the adaptive dimming of illumination and the degradation of image quality due to the dimming while achieving high speed (real time), low power consumption, and suppression of increase in circuit scale. Highly accurate image correction can be realized at the same time.

  Before describing an embodiment of the invention, an adaptive dimming control and an image according to a display image executed by an image display control device (image display control LSI) of the present invention will be described with reference to FIGS. The contents of correction will be described.

(Relation between light control and image correction)
1A to 1C are diagrams for explaining the contents of adaptive dimming control and image correction according to a display image employed in the image display control apparatus (image display control LSI) of the present invention. FIG.

  As shown in FIG. 1A, in the embodiment of the present invention, adaptive image correction of a liquid crystal panel (LCD) 10 and adaptive correction of luminance of an illumination (LED: hereinafter referred to as backlight) 12 ( Adaptive dimming) at the same time. In the figure, Gy ′ is an enhanced image correction amount when there is dimming. This Gy ′ is obtained by adding the image correction amount enhancement amount ΔGy accompanying dimming to the image correction amount Gy when there is no dimming. Gs is a correction amount of the luminance of the backlight 12 due to adaptive dimming.

  FIG. 1B shows the image correction amount Gy when there is no light control. That is, Gy is an image correction amount when the luminance of the backlight 12 is fixed. For example, a correction that raises the luminance is performed on a portion where the luminance is low, and a correction that reduces the luminance is performed on a portion where the luminance is too high.

  FIG. 1C shows the enhancement amount ΔGy of the image correction amount accompanying the light control. Since a dark image is less susceptible to the dimming of the backlight 12 than a bright image, in principle, the dimming amount of the backlight 12 increases in the case of a dark image. However, since the luminance of the display image decreases with dimming, the image correction is strengthened to compensate for the luminance decrease. ΔGy is an image correction enhancement accompanying dimming (Gs).

  In the present invention, as shown in FIG. 1 (A), the backlight 12 is actively dimmed to save power, while the normal image quality is compensated for the image quality degradation accompanying the dimming. The final image correction amount Gy is determined by adding the enhancement (ΔGy) of the image correction amount associated with the light control (Gs) to the image correction amount (Gy).

(Adaptive dimming of image correction amount)
FIG. 2 shows a backlight reduction rate, an image correction amount (Gy) without dimming, an image correction amount (Gy ′) with dimming, and dimming with respect to the average luminance (Yave) of an image of one frame. FIG. 6 is a characteristic diagram illustrating a change in an image correction amount enhancement amount (ΔGy) associated with FIG.

  In the figure, the characteristic line A indicates the characteristic of the backlight luminance reduction rate (%), the characteristic line B indicates the characteristic of the image correction amount (Gy) without dimming, and the characteristic line C indicates dimming. The characteristic of the image correction amount (Gy ′) in the case of being present is shown, and the characteristic line D shows the characteristic of the enhancement (ΔGy) of the image correction amount accompanying the light control.

  First, attention is focused on the characteristic line A indicating the change in the backlight luminance reduction rate. Obviously, the lower the average luminance (Yave), the higher the backlight luminance reduction rate, and the lower the average luminance (Yave), the lower the backlight reduction rate. This is because the higher the average brightness, the greater the effect of backlight dimming.Therefore, for images with a low average brightness, priority is given to power saving and the light is greatly reduced. This is a result of diminishing a small amount in order to give priority to suppression.

  Next, attention is paid to the characteristic line B indicating the change in the image correction amount Gy when there is no light control. As shown in the figure, until the average luminance value Gammath1, almost fixed luminance increase correction is performed, and when the average luminance value increases, the amount of increase in luminance decreases, and when the average luminance value becomes larger than the average luminance value Gammath2, Correction for reducing the brightness is executed. That is, basically, when the average luminance is low, correction is performed to increase the luminance, and when the average luminance is too high, correction is performed to decrease the luminance.

  Next, attention is paid to a characteristic line C indicating a change in the image correction amount Gy ′ when light adjustment is performed. Obviously, the lower the average luminance, the larger the image correction amount, and the higher the average luminance, the smaller the image correction amount. In addition to determining the image correction amount on the basis of the characteristic line B, this further enhances the image correction amount on the low luminance side in order to prevent image quality deterioration on the low luminance side where a large light reduction rate is set. It is necessary.

  Next, attention is focused on the characteristic line D indicating the change in the amount of image correction enhancement (ΔGy = Gy′−Gy) associated with light control. As described above, the enhancement amount ΔGy of the image correction amount associated with the light control increases on the low luminance side and gradually decreases as the luminance value increases. However, the enhancement of the image correction amount gradually increases from around the average luminance value Gammath3. This is because, as the brightness of the backlight 12 is diminished, the higher the brightness of the image, the lower the image quality, so it is necessary to further enhance the image correction in order to suppress the reduction of the brightness of the image having a high average brightness. is there.

(Relationship between power saving strength and ΔGy)
FIG. 3 is a diagram showing how the characteristic line of the image correction amount enhancement (ΔGy = Gy′−Gy) accompanying light adjustment changes according to the luminance reduction rate of the backlight. In FIG. 3, a characteristic line A shows a characteristic line when power saving is high (backlight luminance reduction rate 30%), and a characteristic line B shows a characteristic line when power saving is low (backlight luminance reduction rate 10%). A characteristic line C indicates a characteristic line in the case of normal power saving (backlight luminance reduction rate 20%).

  As described above, in any of the characteristic lines, the enhancement amount ΔGy of the image correction amount accompanying dimming tends to increase on the low luminance side and gradually decrease as the luminance value increases. In the high region, ΔGy tends to gradually increase again. Further, as the power saving performance is enhanced and the luminance reduction rate of the backlight is increased, the image correction amount enhancement amount ΔGy associated with the light control is also increased.

(Enhancement of saturation correction)
Dimming the backlight reduces the saturation across the screen. Therefore, saturation correction is performed so that the saturation before and after dimming is preserved. Basically, the saturation is corrected according to the following equation (1). In the following formula, only blue saturation (Cb = Y−B) is shown, but the same applies to red saturation (Cr = Y−R).
Cb [cb] = Fc × Gc + Cb (1)
In the above equation (1), cb is a saturation correction input color difference, Cb is a saturation correction output color difference, Gc is a saturation correction amount, and Fc is a saturation correction coefficient curve.

  4A to 4C are diagrams for explaining saturation correction. FIG. 4A shows the output color difference (Cb or Cr) with respect to the input color difference (cb or cr). In the figure, the difference between the characteristic line indicated by the solid line and the straight line indicated by the dotted line corresponds to the saturation correction amount Gc in the above equation (1). FIG. 4B shows the characteristic of the correction coefficient (Fc) with respect to the input saturation (cb or cr). However, since the above equation (1) indicates saturation correction without considering dimming, actually, it is necessary to add the saturation correction enhancement ΔGc accompanying dimming to the saturation correction amount Gc. There is. ΔGc can be obtained by solving an equation under the condition that the average saturation is equal before and after dimming.

  Further, when the light reduction amount is determined based on only the luminance, the light reduction is excessive and the vividness of red (R) or blue (B) may be impaired. That is, since dark images are less affected by dimming, it is a general rule that the amount of light dimming increases. However, even if the image is dark, for example, if there is a large and bright rose flower in the center of the screen, it is reasonable to impose a limit on the amount of light that can be reduced to reduce the saturation of the rose. is there. However, since red (R) and blue (B) have a low contribution rate to luminance (Y), if they are judged only by luminance (Y), the illumination is excessively reduced based on the judgment that they are dark images. I will let you. Therefore, in order to prevent such excessive dimming, dimming is determined based not only on luminance (Y) but also on saturation (red saturation (Cr), blue saturation (Cb)). When the luminance and the saturation satisfy a predetermined relationship, the saturation is prioritized to limit the amount of light reduction. As a result, dimming is suppressed in an image with high saturation, and reduction in saturation of the display image is suppressed.

  FIG. 4C is a diagram for explaining processing for determining which of dimming or saturation preservation is to be prioritized using a threshold value determined by the relationship between average luminance and average saturation. As shown in the figure, a threshold value determined by the relationship between the average value of luminance and the average value of color difference (= saturation) is set, and the threshold value is used as a boundary to perform dimming or Based on this, it is determined whether dimming is executed.

  In the drawing, a hatched area ZP2 is a dimming area based on saturation (cr, cb), and ZP1 is a dimming area based on luminance (Y). For example, when the average luminance value is “64”, the image is dark, and therefore the amount of light reduction is considerably increased if only the luminance is determined. However, if the average saturation is, for example, “96”, it is an image with high saturation, and therefore it is necessary to suppress the reduction of saturation due to light reduction. Therefore, in such a case, the amount of light reduction is determined based on the saturation (the amount of light reduction is made smaller than that based on the luminance). In other words, a predetermined limit based on the saturation is provided for the amount of light reduction based on the luminance, thereby suppressing excessive light reduction that extremely reduces the saturation.

  (Filter processing to prevent flicker associated with scene changes)

  When adaptive illumination dimming and image correction are performed on each frame of a moving image, visual flicker occurs due to a rapid change in the illumination luminance and the image correction amount accompanying a scene change. Therefore, filter processing suitable for each characteristic is executed for both illumination correction and image correction obtained in units of frames. Since the change in illumination brightness is a change between white and black, which is easy to recognize visually, filter processing with a long time constant is applied.On the other hand, the change in image correction amount is a halftone change that is not noticeable. A filter process with a short time constant is applied with emphasis on quick response to scene changes. As a result, it is possible to effectively suppress flicker associated with adaptive illumination correction while realizing image correction following a scene change of a moving image.

  In addition, if each filter process is executed independently, the balance between the illumination correction and the image correction may be lost and the image quality may deteriorate. Therefore, the first filter processing is performed on the illumination luminance obtained in frame units, the image correction amount is obtained from the result, and the second filter processing is performed on the image correction amount (execution of serial processing is performed) Adopting a configuration to do). Since the amount of image correction adapted to the reduced light amount is calculated after the reduced amount of illumination luminance is calculated, the balance between the first and second filter processes is always ensured.

  FIG. 5 is a diagram for explaining the outline of the image display control device of the present invention and the contents of the filter processing. FIG. 5A is a block diagram showing the overall configuration of the image display control device, and FIG. FIG. 5B is a block diagram more specifically showing the configuration shown in FIG. 5A, and FIG. 5C is a diagram showing a time constant of filter processing executed in the dimming control. FIG. 5D is a diagram illustrating a time constant of filter processing executed at the time of image correction.

  As shown in FIG. 5A, the maximum value (denoted as Wave) among the average values of luminance (Y), blue saturation (Cb), and red saturation (Cr) is input. The input signal is subjected to linear processing (C) to calculate the backlight luminance (K), and the backlight luminance (K) is filtered by the time axis filter 22 having a long time constant to obtain the final backlight. Light brightness (a dimming coefficient indicating the backlight brightness after dimming) Kflt is obtained. The characteristics of the time axis filter 22 are controlled by the filter coefficient P. The relationship between the value of the filter coefficient P and the change rate (ΔYave) of the average luminance of the image is as shown in FIG.

  Based on the final backlight luminance (Kflt), the image correction amount calculation unit 24 calculates a correction amount Gm for brightness correction and saturation correction. The image correction amount Gym is subjected to a filtering process by the time axis filter 26 having a short time constant, whereby the final image correction amount (Gy ′) is obtained. The characteristics of the time axis filter 26 are controlled by the filter coefficient q. The relationship between the value of the filter coefficient q and the average luminance change rate (ΔYave) is as shown in FIG.

  As shown in FIG. 5B, the backlight time axis filter 22 is a recursive (IIR) filter, and the image correction amount time axis filter 26 is also a recursive (IIR) filter. is there. The transfer function of the time axis filter 22 for backlight is Hbl [z], and the transfer function of the time axis filter 26 for image correction amount is Himg [Z]. Therefore, the transfer function of the filter processing in the image display control apparatus is represented by Hbl [z] · Himg [Z]. The image correction calculation unit 24 is realized by a non-linear transfer function. In FIG. 5B, reference numerals 28 and 30 indicate delay elements.

Next, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
(Mounting mode of image display control device)
6 (A) to 6 (D) are block diagrams for explaining the mounting mode of the image display device of the present invention.

  In FIG. 6A, an image display control device (image display control LSI) is mounted on a mobile phone terminal (an example of an electronic device) 100. The cellular phone terminal 100 includes an antenna AN, a communication / image processing unit 102, a CCD camera 104, a host computer 106, an image display control device (image display control LSI) 108, and a driver 110 (panel driver 112 and back). A display panel (for example, a liquid crystal panel (LCD)) 116, and a backlight (LED) 118.

  In FIG. 6B, an image display control device (image display control LSI) 108 is mounted on the drive device (driver) 110 itself, and the image display control device (image display control LSI) 108 receives an image from the host computer 106. Signals and control information are input.

  In FIG. 6C, the image display control device (image display control LSI) 108 is mounted on the control device (controller) 130 of the driver 110. In FIG. 6D, an image display control device (image display control LSI) 108 is mounted on a drive control device 140 (integrated driver and controller) 140.

  The image display control device (image display control LSI) 108 according to the present invention has the characteristics that it can process a moving image such as a streaming image, can be processed in real time, has excellent power saving performance, and can be downsized. Therefore, by mounting the image display control device (image display control LSI) of the present invention, the drive device (driver) 110, the control device (controller) 130, and the drive control device (device in which the driver and the controller are integrated). In addition, the added value of the electronic device 100 is improved.

(Overall configuration of image display control device)
FIG. 7 is a block diagram showing an outline of the overall configuration of the image display control apparatus (image display control LSI) of the present invention.

  Here, it is assumed that the image display control device 108 is mounted on a mobile terminal (including a mobile phone terminal, a PDA terminal, and a portable computer terminal). The portable terminal includes, for example, an antenna AN that receives one-segment broadcasting, a communication / image processing unit 102, and a host computer 106. For example, the host computer 106 supplies the received streaming video signal to the image display control device 108. Note that the image signal captured by the CCD camera can be supplied to the image display control device 108 (see FIG. 6A), but in FIG. 7, the CCD camera is omitted.

  As shown in the figure, the image display control device 108 receives an image signal (RGB (color signal format) or YUV (luminance signal and color difference signal format)) given from the host computer 106, and the image signal is RGB. Is an image input interface (I / F) 150 for converting into a YUV image signal, a register 152 for temporarily storing control information given from the host computer 106, and a backlight luminance after dimming (dimming coefficient Kflt) And an image correction core 200 that performs an image correction process on the image signal so as to compensate for a decrease in image quality due to dimming, and a YUV format image signal is converted into an RGB format image signal, or a YUV format image signal An image output interface (I / F) 154 that outputs the data as it is.

  The image correction core 200 extracts a synchronization signal from the YUV format image signal output from the image input interface (I / F) 150, generates a timing signal indicating the operation timing of each unit, and is necessary for calculation. A histogram creation unit (statistical information acquisition unit) 212 that acquires statistical information, a sequence counter 214, a code table 216 that stores microcode obtained by subdividing a correction algorithm, and an instruction and data by decoding the microcode. A decoder 217 to be generated, a common arithmetic unit 218 that is configured by a minimum circuit and used in common for each process of light control and image correction, and a correction coefficient for image correction generated by the operation are temporarily A coefficient buffer 220 that accumulates, an image correction unit 222 that corrects an image signal using a correction coefficient, A.

  FIG. 8 is a diagram showing the contents of control signals supplied from the host computer to the image display control device. For example, an image signal conforming to, for example, MPEG4 is input from the communication / image processing unit 102 to the host computer 106, and mode information (for example, a high-definition display mode is designated from the image input interface (I / F) 302). Mode signal) and image quality information (for example, information indicating gamma correction, contrast, intensity of saturation, scene weighting coefficient information, etc.) are input.

  An image signal (RGB format or YUV format) is output from the host computer 106, and gamma correction intensity (L1), contrast intensity (L2), saturation intensity (L3), and image correction scene weight as control information are output. The coefficient (L4), the backlight luminance reduction rate (power saving degree: L5), and the backlight scene weighting coefficient (L6) are output. The scene weighting factor for image correction (L4) and the scene weighting factor for backlight (L6) correspond to the filter coefficients P and Q in FIG.

  The control information described above is temporarily stored in the register 152 and then supplied to the shared arithmetic unit 218. The shared arithmetic unit 218 executes a predetermined operation using instructions and data from the decoder 217 based on the given control information, and performs a correction coefficient for image correction and a backlight luminance (a dimming coefficient Kflt). ) Is generated.

  FIG. 9 is a block diagram showing a specific configuration of the image display control apparatus shown in FIG. In FIG. 9, the configuration of the image correction core 200 is described more specifically. In FIG. 9, the same reference numerals are given to the portions common to FIG.

  In FIG. 9, the shared arithmetic unit 218 includes first and second multiplexers (400a, 400b), an arithmetic logic unit (ALU) 402, a distributor 404 that distributes the arithmetic results of the arithmetic logic unit (ALU), A plurality of output destination registers (destination registers) 406. The output destination register 406 includes register groups 408a to 408c divided for each output destination. Further, a feedback path is formed for returning at least a part of the operation results accumulated in each of the plurality of register groups 408a to 408c to the input side of the first and second multiplexers (400a, 400b).

Hereinafter, the function and operation of each part of the image correction core 200 of FIG. 9 will be described in detail.
A histogram creation unit (statistical information acquisition unit) 212 acquires statistical information (statistical information about luminance and statistical information about saturation) of image signals for one frame. A specific internal configuration of the histogram creation unit (statistical information acquisition unit) 212 will be described in the third embodiment.

  The code table (code storage unit) 216 stores a plurality of microcodes for designating the operation procedure of the shared arithmetic unit 218. The procedure for creating the code table 216 will be described in the second embodiment.

  The sequence counter (sequence instruction unit) 214 points to the code table 216 and controls the output order of the microcode from the code table 216. The decoder 217 sequentially decodes the output microcode from the code table 216 to generate at least one of an instruction and data (such as a coefficient) to be supplied to the shared arithmetic unit.

  The decoder 217 supplies the coefficients used for the operation to the first and second multiplexers (400a, 400b), and supplies the arithmetic instruction (opcode) to the arithmetic logic unit (ALU) 402 for distribution. Distribution destination information (destination information) is supplied to the device 404.

  The common computing unit 218 calculates the correction coefficient for image correction and the backlight luminance after dimming (dimming coefficient Kfit) in real time. As a result, the digital signal processing described with reference to FIGS. 5A to 5D is executed by the calculation of the shared arithmetic unit 218. Also, the saturation enhancement process, the process of limiting the backlight luminance reduction rate to prevent the deterioration of the image quality of the high saturation image, and the first and second cycles described with reference to FIGS. Substantially all the processes for performing the type filter processing in series are executed.

  As described above, the operation of the shared arithmetic unit 218 is controlled by the microcode that encodes the signal processing procedure. By using a shared arithmetic unit having a minimum circuit configuration, real-time arithmetic can be performed without the need to provide the same type of hardware in parallel. Therefore, high-speed light control and image correction can be realized with the minimum circuit and the minimum power consumption.

  The calculation result of the shared arithmetic unit 218 is temporarily stored in the register groups 408a to 408c divided for each output destination. The calculated backlight luminance (dimming coefficient Kflt) is output to the backlight (LED) driver, and the correction coefficient is stored in the coefficient buffer 410. The correction coefficients stored in the coefficient buffer 410 are supplied to the image correction unit 222 in synchronization with the input of the image signal of the next frame, and image correction (enhancement of luminance and saturation) is executed.

  In addition, at least a part of the operation results stored in each of the plurality of register groups 408a to 408c is fed back to the input side of the first and second multiplexers (400a, 400b) via the feedback path. As a result, first, the illumination brightness after dimming is obtained, the calculation result is returned to the input side, and a process for obtaining an image correction coefficient based on the obtained illumination brightness is executed. Further, the first and second cyclic (IIR) filter processes described above are executed.

(Second Embodiment)
In the present embodiment, the procedure for creating the code table shown in FIG. 9 will be described. FIG. 10 is a diagram showing a procedure for creating a code table.

  In FIG. 10, first, a programming language for correcting an image signal so that a backlight for displaying an image is adaptively dimmed according to a display image and image quality deterioration due to dimming of the backlight is compensated. For example, an algorithm (enhancement operation algorithm) using a high-level programming language is prepared (step S500).

  Next, the algorithm created in the programming language is batch converted to generate microcode (step S502).

  Next, the generated microcode is written in a ROM (read only memory) (step S502).

  In this way, the code table 216 can be created efficiently. In addition, by changing the algorithm (microcode), it is possible to relatively easily change the calculation contents of the shared arithmetic unit 218. Therefore, it is possible to flexibly cope with design changes.

(Third embodiment)
In the present embodiment, a specific configuration inside the histogram creation unit (statistical information acquisition unit) 212 in FIG. 9 will be described.

  As described above, in the image display control device of the present invention, statistical values related to the luminance and saturation of the image signal for one frame are acquired, and the backlight luminance and the image signal (saturation and luminance) are based on the statistical values. Is adaptively corrected. Further, as described above, when correcting an image, if the average saturation is high even in an image with low average brightness, priority is given to saturation over power saving, and the backlight dimming rate is limited. Correction is performed. In order to execute such control, it is necessary to acquire necessary brightness and saturation statistics information at high speed.

  FIG. 11 is a circuit diagram showing a specific internal configuration of the histogram creation unit (statistical information acquisition unit) in FIG. 9. As shown in the drawing, a plurality of statistical units (EX0 to EX255) for creating a luminance histogram are provided. All of EX0 to EX255 have the same circuit configuration. That is, each of the plurality of statistical units (EX0 to EX255) for creating the luminance histogram is a comparison that compares the luminance value of the input image signal with the reference luminance value (this reference luminance value is different for each statistical unit). A counter 1, an up counter 2, an AND gate 3, and a statistical value buffer 4. The luminance value is 256 gradations, and each of the reference luminance values (1) to (255) corresponding to each gradation is given to each of the comparators (EX0 to EX255).

  The luminance signal (Y) of the image signal is input in parallel to each statistical unit (EX0 to EX255), and is compared simultaneously with the reference luminance values (1) to (255) corresponding to each gradation by each comparator 1. . Each comparator 1 functions as a luminance value coincidence detection circuit, and when the input luminance value coincides with the reference luminance value, the output of the comparator becomes high level, thereby supplying the other input terminal of the AND gate 3. The operation clock is supplied to the statistical value buffer 4.

  The statistical value buffer 4 fetches and latches the count value of the up counter 2 at the timing when the clock is supplied. In this way, the luminance value of each pixel included in the image signal is classified and counted for each gradation value. Since the luminance value of the input image is input in parallel to each statistical unit, high-speed statistical values can be acquired.

  The luminance maximum value / minimum value detector 5 obtains the maximum value and the minimum value of the luminance (Y) based on the count value of each statistical unit (EX0 to EX255). In addition, the standard deviation calculation unit 6 calculates a standard deviation value indicating the distribution of luminance (Y). Using the statistical values calculated in this way, adaptive light control and image correction are executed.

  Further, as shown in the lower part of FIG. 11, a statistical unit ES (Y) for obtaining an average value of luminance (Y) and a statistical unit ES (Cb) for obtaining an average value of blue saturation (Cb). And a statistical unit ES (Cr) for obtaining an average value of red saturation (Cr). Each statistical unit (ES (Y), ES (Cb), ES (Cr)) has the same configuration.

  That is, each statistical unit (ES (Y), ES (Cb), ES (Cr)) includes an adder (7a-7c) for accumulating the values of Y, Cb, Cr, and a sum for accumulating the accumulated addition value. Value buffers (8a to 8c). The average value calculators (9a to 9c) calculate and output the average value of luminance (Y), the average value of saturation (Cb), and the average value of saturation (Cr), respectively.

  As described in FIG. 4C, depending on the relationship between the luminance (Y) and the saturation (Cb, Cr), either the luminance (Y) or the saturation (Cb, Cr) is calculated for the dimming coefficient. The base is selected. The average value of luminance (Y), the average value of saturation (Cb), and the average value of saturation (Cr) are used for such determination.

  Also, the AND gate A1 shown in the lower left of FIG. 11 is intended to gate the operation clock given to each statistical unit (EX0 to EX255) with a statistical value valid signal and stop the clock supply as necessary. Is provided. Similarly, the AND gate A2 gates the operation clock given to each statistical unit (ES (Y), ES (Cb), ES (Cr)) with the average valid signal, and stops the clock supply as necessary. It is provided for the purpose. When statistical value acquisition is unnecessary, power supply can be reduced by stopping clock supply and statistical value acquisition operation.

  As described above, the present invention has been described using the embodiments. However, the present invention is not limited thereto, and various modifications and applications are possible without departing from the gist of the present invention.

  As described above, according to at least one embodiment of the present invention, for example, the following effects can be obtained. However, the following effects are not always obtained, and the following list of effects should not be used as a basis for unduly limiting the present invention.

  By using a shared computing unit of the microprogram control system, real-time computation is possible without providing the same type of hardware in parallel, and high-speed adaptive dimming control and adaptive image correction are achieved with the minimum circuit and minimum power consumption. Can be realized.

  By enhancing (expanding) not only the luminance but also the saturation, it is possible to suppress a decrease in the saturation, and it is possible to more effectively compensate for a decrease in image quality due to dimming.

  By determining the amount of light reduction in consideration of both luminance and saturation, the amount of light reduction is limited in an image with high saturation, and saturation reduction due to excessive light reduction can be effectively prevented.

  In both dimming correction and image correction, cyclic (IIR) filter processing is executed, and the time constant of the filter processing for dimming correction is set to be longer, thereby improving the responsiveness to a scene change of a moving image. The occurrence of flicker (visual flicker) can be effectively suppressed while ensuring.

  After calculating the amount of light reduction of the illumination brightness, calculating the image correction amount adapted to the amount of light reduction (adopting serial processing), filter processing accompanying dimming control, dimming processing accompanying image correction Is always balanced.

  According to the present invention, power consumption can be greatly reduced by adaptive dimming of illumination luminance while suppressing deterioration in image quality to a minimum (a reduction of up to 30% has been confirmed). Further, since it can be realized with a minimum amount of hardware, space can be saved.

  According to the present invention, it is possible to realize high added value of a drive device (driver) such as a liquid crystal display device, a control device (controller), and a drive control device (device in which a driver and a controller are integrated).

  By installing the image display control device (LSI) of the present invention in a mobile terminal (including a mobile phone terminal, a PDA terminal, and a portable computer), a streaming image such as one-segment broadcasting can be displayed with high image quality. In addition, the battery life can be extended.

  According to the present invention, while achieving high speed (real-time performance), low power consumption, and suppression of an increase in circuit scale, conventional dimming of illumination and compensation for deterioration in image quality due to the dimming are achieved. High-accuracy image correction that is not possible can be realized at the same time.

  The present invention adaptively reduces the luminance of display illumination in accordance with a display image, and corrects an image signal so as to compensate for a reduction in image quality due to the dimming (image display control device). Control LSI) and the like, as well as a display panel drive device (driver) on which the image display control device is mounted, a display panel control device (controller), and a display panel drive control device (a device in which a driver and a controller are integrated) It is useful as an electronic device such as a portable terminal.

1A to 1C are diagrams for explaining the contents of adaptive dimming control and image correction according to a display image employed in the image display control apparatus (image display control LSI) of the present invention. FIG. Backlight reduction rate, image correction amount (Gy) without dimming, image correction amount (Gy ′) with dimming, and image correction accompanying dimming with respect to average luminance (Yave) of an image of one frame It is a characteristic view which shows the change of the reinforcement | strengthening part ((DELTA) Gy) of quantity. It is a figure which shows how the characteristic line of the image correction amount reinforcement | strength ((DELTA) Gy = Gy'-Gy) accompanying light control changes according to the luminance reduction rate of a backlight. 4A to 4C are diagrams for explaining saturation correction. FIG. 5 is a diagram for explaining the outline of the image display control device of the present invention and the contents of filter processing, FIG. 5A is a block diagram showing the overall configuration of the image display control device, and FIG. 5A is a block diagram showing more specifically the configuration shown in FIG. 5A, and FIG. 5C is a diagram showing a time constant of filter processing executed at the time of dimming control, and FIG. FIG. 4 is a diagram showing a time constant of filter processing executed at the time of image correction. 6 (A) to 6 (D) are block diagrams for explaining the mounting mode of the image display device of the present invention. It is a block diagram which shows the outline | summary of the whole structure of the image display control apparatus (image display control LSI) of this invention. It is a figure which shows the content of the control signal which a host computer supplies to an image display control apparatus. It is a block diagram which shows the specific structure of the image display control apparatus shown by FIG. It is a figure which shows the preparation procedure of a code table. FIG. 10 is a circuit diagram showing a specific internal configuration of the histogram creation unit (statistical information acquisition unit) of FIG. 9.

Explanation of symbols

10 LCD panel, 12 Backlight (LED) as illumination,
DESCRIPTION OF SYMBOLS 100 Mobile phone terminal (electronic device) 102 Communication / image processing part 104 CCD camera 106 Host computer 108 Image display control device 110 Driver 112 Panel driver 114 Backlight driver 116 Display panel 118 Backlight ( LED), 150 image input interface (I / F), 152 register for storing control information from the host computer, 154 image output interface (I / F), 200 image correction core, 210 timing unit, 212 histogram creation unit (statistics) Information acquisition unit), 214 sequence counter, 216 code table, 217 decoder, 218 shared arithmetic unit, 220 coefficient buffer, 222 image correction unit, 400a and 400b, first and second multiplexers, 402 arithmetic logic unit (ALU), 404 distributor, 406 distribution destination register, 408a to 408c, register group distinguished for each distribution destination, 410 coefficient buffer

Claims (14)

An image display control device that adaptively diminishes illumination for image display according to a display image, and corrects an image signal so as to compensate for image quality degradation accompanying dimming of the illumination,
A statistical information acquisition unit for acquiring statistical information of the image signal;
Using the statistical value information of the image signal given from the statistical information acquisition unit, obtain the illumination brightness after dimming, and generate a correction coefficient used to correct the image signal,
A code storage unit storing a plurality of codes for designating operation procedures of the shared arithmetic unit;
A sequence instruction unit for controlling the output order of the codes from the code storage unit;
A decoder that decodes the code output from the code storage unit and generates at least one of an instruction and data to be supplied to the shared arithmetic unit;
An image display control device comprising: The image display control device according to claim 1,
The code is sequentially output from the code storage unit in the order instructed by the sequence instruction unit, and the instruction or the data generated as a result of decoding by the decoder is supplied to the shared arithmetic unit, and the instruction Alternatively, determination of the illumination brightness after dimming and generation of a correction coefficient used for correcting the image signal using the data are executed by the shared arithmetic unit, and the image corrected using the correction coefficient An image display control device characterized in that a signal and a signal indicating the proof luminance after dimming are output. The image display control device according to claim 1,
The shared arithmetic unit includes first and second multiplexers, an arithmetic logic unit, and a distributor that distributes the arithmetic result of the arithmetic unit.
A coefficient is supplied from the decoder to the first and second multiplexers, an arithmetic instruction is supplied to the arithmetic logic unit, and distribution destination information is supplied to the distributor. An image display control device. The image display control device according to claim 3,
The shared arithmetic unit further includes:
Multiple output destination registers,
A feedback path for returning at least a part of the signals accumulated in the plurality of output destination registers to the input side;
An image display control device comprising: The image display control device according to any one of claims 1 to 4,
The statistical information acquisition unit acquires a statistical value of saturation in addition to a statistical value of luminance of the image signal,
In the correction of the image signal using the correction coefficient, correction for enhancing luminance corresponding to dimming of the illumination and correction for enhancing saturation corresponding to dimming of the illumination are performed. An image display control device. The image display control device according to any one of claims 1 to 3,
The statistical information acquisition unit acquires the statistical value of the saturation in addition to the statistical value of the luminance of the image signal,
When determining the illumination brightness after the dimming after the dimming, priority is given to either the dimming of the illumination or the prevention of the saturation reduction from the relationship between the statistical value of the luminance and the statistical value of the saturation. An image display control device that determines whether to reduce the saturation and, when priority is given to prevention of a decrease in saturation, executes a dimming control after imposing a limit on the dimming of illumination. The image display control device according to any one of claims 1 to 6,
For each of the correction for dimming the illumination and the correction of the image signal using the correction coefficient, first and second cyclic filter processing is performed,
The time constant of the first cyclic filter processing for correction for dimming the illumination is set longer than the time constant of the second cyclic filter processing for correction of the image signal. An image display control device characterized by that. The image display control device according to claim 7,
Based on at least one of the statistical value of luminance and the statistical value of saturation, the dimming control of the illumination including the first cyclic filter processing is executed, and the proof luminance after the dimming is obtained. Subsequently, the image display control apparatus includes a correction of the image signal including the second cyclic filter processing based on the obtained illumination luminance. The image display control device according to claim 7 or 8,
The image display control apparatus, wherein the shared arithmetic unit has a feedback path for returning at least a part of the operation result to the input side. An image display control device according to any one of claims 1 to 9,
The code stored in the code storage unit adaptively diminishes the illumination for displaying the image according to the display image, and corrects the image signal so as to compensate for the deterioration in image quality due to the dimming of the illumination. An image display control device, characterized in that it is a microcode obtained by converting an algorithm description by a programming language for the purpose.   11. A drive device for an electro-optical device on which the image display control device according to claim 1 is mounted.   11. A control device for an electro-optical device on which the image display control device according to claim 1 is mounted.   11. A drive control device for an electro-optical device on which the image display control device according to claim 1 is mounted.   The electronic device carrying the image display control apparatus in any one of Claims 1-10.

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