Patent Application
20080143756
Japanese Patent Application No. 2006-304667 filed on Nov. 10, 2006 and Japanese Patent Application No. 2007-272738 filed on Oct. 19, 2007, are hereby incorporated by reference in their entirety.
The present invention relates to an image display control device and the like. More particularly, the invention relates to an image display control device (image display control LSI) which adaptively reduces the luminance of display lighting corresponding to a display image and corrects an image signal to compensate for deterioration in image quality due to a reduction in luminance, and the like.
JP-A-11-65531 discloses technology which reduces the quantity of light emitted from a backlight aimed at reducing power consumption, and adjusts image data to increase the transmissivity of a liquid crystal display screen as much as possible.
JP-A-2004-310671 discloses an image correction device which uses a look-up table (LUT) in order to correct a luminance signal of a display image.
In order to simultaneously perform a reduction in luminance of lighting (e.g., backlight) and image correction aimed at preventing deterioration in image quality, it is necessary to perform a large number of calculations based on image data. Calculations may be simplified by utilizing a look-up table (LUT) which stores calculation results. However, memory access takes time. Therefore, this method cannot be used when a high-speed capability is required. For example, a method using an LUT is not suitable when a real-time capability is required, such as when reproducing a streaming image distributed by one-segment broadcasting (digital broadcasting for portable telephone terminals) using a portable telephone terminal.
A high-speed capability (real-time capability) can be ensured by causing a plurality of pieces of dedicated hardware to perform specific calculations in parallel. However, the occupied area and the power consumption of the circuit are inevitably increased.
JP-A-11-65531 takes only luminance correction into consideration during image correction which compensates for deterioration in image quality due to a reduction in lighting luminance. However, since the image quality significantly deteriorates when the chroma (color brightness (vividness)) of the image is impaired due to a reduction in lighting luminance, image correction taking not only the luminance but also the chroma into consideration is necessary.
When the amount of reduction in lighting luminance is adaptively determined corresponding to the luminance of the display image, the lighting luminance quickly changes to follow a quick change in luminance of the display image, whereby a flicker occurs. As a result, the image quality of the display image may deteriorate. In particular, since the luminance of an image frequently changes momentarily when reproducing a streaming image, a flicker (visual flicker) may occur. Therefore, it is necessary to suppress a flicker accompanying a scene change.
According to one aspect of the invention, there is provided an image display control device that adaptively reduces a luminance of image display lighting corresponding to a display image and corrects an image signal to compensate for deterioration in image quality due to the reduction in the luminance of the lighting, the image display control device comprising:
a statistical information acquisition section that acquires statistical information of the image signal;
a common calculator that calculates the luminance of the lighting after reduction in luminance using the statistical information of the image signal supplied from the statistical information acquisition section, and generates a correction coefficient to correct the image signal;
a code storage section that stores a plurality of codes, the plurality of codes specifying an operation procedure of the common calculator;
a sequence instruction section that controls an order of output of the plurality of codes from the code storage section; and
a decoder that decodes the plurality of codes output from the code storage section and generates at least one of an instruction and data supplied to the common calculator.
According to another aspect of the invention, there is provided a driver device of an electro-optical device, the driver device including the above image display control device.
According to a further aspect of the invention, there is provided a control device of an electro-optical device, the control device including the above image display control device.
According to a further aspect of the invention, there is provided a drive control device of an electro-optical device, the drive control device including the above image display control device.
According to a further aspect of the invention, there is provided an electronic instrument including the above image display control device.
Aspects of the invention may implement an adaptive reduction in lighting luminance and a highly accurate image correction which compensates for deterioration in image quality due to a reduction in lighting luminance at the same time while achieving a high-speed process (real-time process) and a reduction in power consumption of a circuit and suppressing an increase in circuit scale.
(1) According to one embodiment of the invention, there is provided an image display control device that adaptively reduces a luminance of image display lighting corresponding to a display image and corrects an image signal to compensate for deterioration in image quality due to the reduction in the luminance of the lighting, the image display control device comprising:
a statistical information acquisition section that acquires statistical information of the image signal;
a common calculator that calculates the luminance of the lighting after reduction in luminance using the statistical information of the image signal supplied from the statistical information acquisition section, and generates a correction coefficient to correct the image signal;
a code storage section that stores a plurality of codes, the plurality of codes specifying an operation procedure of the common calculator;
a sequence instruction section that controls an order of output of the plurality of codes from the code storage section; and
a decoder that decodes the plurality of codes output from the code storage section and generates at least one of an instruction and data supplied to the common calculator.
An adaptive reduction in lighting luminance and image correction are implemented by real-time calculations of the common calculator. The image correction coefficient and the lighting luminance after reduction in luminance are calculated in real time by the calculations of the common calculator, and image correction using the calculated correction coefficient is performed. The calculations of the common calculator are controlled by microcodes which specify a signal processing procedure. Real-time calculations can be implemented without parallelly providing the same type of hardware by utilizing the common calculator, whereby high-speed luminance adjustment control and image correction can be implemented using a minimum number of circuits and with minimum power consumption.
(2) In the image display control device according to this embodiment, the code storage section sequentially may output the plurality of codes in the order specified by the sequence instruction section, the decoder may supply the instruction or the data generated as a result of decoding to the common calculator, and the common calculator may determine the luminance of the lighting after reduction in luminance and may generate the correction coefficient to correct the image signal using the instruction or the data, and may output the image signal corrected using the correction coefficient and a signal that indicates the luminance of the lighting after reduction in luminance.
The above configuration specifies the generation procedure of the instruction (operand) and data (e.g., multiplication coefficient) supplied to the common calculator. The sequence instruction section specifies a code table which stores the microcodes, and the codes are sequentially output. An instruction and data are generated by decoding the codes, and supplied to the common calculator. The lighting luminance after reduction in luminance and the correction coefficient are generated by calculations of the common calculator, and output in parallel. The lighting luminance after reduction in luminance and the correction coefficient can be quickly and efficiently generated using the most simplified configuration.
(3) In the image display control device according to this embodiment,
the common calculator may include a first multiplexer and a second multiplexer, an arithmetic logic unit, and a distributor that distributes calculation results of the arithmetic logic unit, and
the decoder may supply a coefficient to the first multiplexer and the second multiplexer, may supply an operation code to the arithmetic logic unit, and may supply destination information to the distributor.
The above configuration gives an example of a specific configuration of the common calculator, and also specifies the instruction or data supplied to each element. According to this embodiment, the common calculator includes a plurality of multiplexers, an arithmetic logic unit (ALU), and a distributor. A coefficient used for calculations is supplied to the multiplexers, an instruction (operation code) is supplied to the ALU, and destination information is supplied to the distributor.
(4) In the image display control device according to this embodiment, the common calculator may further include:
a plurality of output destination registers; and
a feedback path, signals stored in the plurality of output destination registers being at least partially fed back to an input side of the calculator through the feedback path.
The above configuration specifies that the common calculator includes the feedback path through which the calculation results are fed back to the input side. For example, it is possible to perform a process in which the lighting luminance after reduction in luminance is calculated by a first calculation process, the calculation results are fed back to the input side, and the image correction coefficient is calculated based on the calculated lighting luminance. An infinite impulse response (IIR) filtering process can also be performed by providing the feedback path in the common calculator.
(5) In the image display control device according to this embodiment,
the statistical information acquisition section may acquire a statistical value of a luminance and a statistical value of a chroma of the image signal, and
the image display control device may correct the image signal using the correction coefficient by performing an enhancement of the luminance of the image signal corresponding to the reduction in the luminance of the lighting and an enhancement of the chroma of the image signal corresponding to the reduction in the luminance of the lighting.
When correcting an image accompanying a reduction in luminance, the image quality may deteriorate due to a decrease in chroma when merely enhancing the luminance. Specifically, since the entire color gamut is reduced due to a reduction in lighting luminance, the chroma inevitably decreases. According to this embodiment, image correction is performed in which the chroma (red chroma (Cr) and blue chroma (Cb)) is also enhanced in addition to the luminance. For example, chroma correction is enhanced so that the average chroma remains the same as much as possible before and after luminance adjustment. This prevents deterioration in image quality of a vivid image.
(6) In the image display control device according to this embodiment,
the statistical information acquisition section may acquire a statistical value of a luminance of the image signal and a statistical value of a chroma of the image signal, and
when calculating the luminance of the lighting after reduction in luminance, the image display control device may determine whether to give priority to either a reduction in the luminance of the lighting or prevention of a decrease in the chroma based on a relationship between the statistical value of the luminance and the statistical value of the chroma, and may perform luminance reduction control while limiting a reduction in the luminance of the lighting when the image display control device has determined to give priority to prevention of a decrease in the chroma.
When adaptively reducing the luminance of lighting (e.g., backlight) based on the statistical information of the image, if the amount of reduction in luminance is determined merely based on the luminance, the brightness (vividness) of red (R) and blue (B) may be impaired due to too large a reduction in luminance. Specifically, since a dark image is affected by a reduction in luminance to a small extent, the luminance is reduced to a large extent. On the other hand, when a large and bright rose or the like is displayed at the center of a dark image, the amount of reduction in luminance is appropriately limited in order to suppress a decrease in chroma of the rose. However, since red (R) and blue (B) contribute to the luminance (Y) to a small extent, the lighting luminance may be reduced to a large extent when the amount of reduction in luminance is determined merely based on the luminance (Y) (i.e., the image is determined to be a dark image). In order to prevent such an excessive reduction in luminance, the amount of reduction in luminance is determined based on the luminance (Y) and the chroma (red chroma (Cr) and blue chroma (Cb)). When the luminance and the chroma satisfy a specific relationship, the amount of reduction in luminance is limited as a result of giving priority to the chroma. This suppresses a reduction in luminance when the image has a high chroma, whereby a decrease in chroma of the display image is suppressed.
(7) In the image display control device according to this embodiment,
the image display control device may perform a first infinite impulse response filtering process and a second infinite impulse response filtering process during correction that reduces the luminance of the lighting and correction of the image signal using the correction coefficient, respectively, and
a time constant of the first infinite impulse response filtering process performed during the correction that reduces the luminance of the lighting may be set to be larger than a time constant of the second infinite impulse response filtering process performed during the correction of the image signal.
When adaptive lighting luminance adjustment and image correction are performed in each frame of a video image, a visual flicker occurs due to sudden changes in lighting luminance and the amount of image correction accompanying a scene change. Therefore, luminance correction and image correction calculated in frame units are appropriately filtered depending on their characteristics. Specifically, since a change in lighting luminance is a change in black and white and is easily observed visually, a filtering process with a large time constant is performed. On the other hand, since a change in the amount of image correction is a change in halftone and is observed with difficulty, a filtering process with a small time constant is performed taking a quick response to a scene change in a video image into consideration. This makes it possible to effectively suppress a flicker accompanying adaptive luminance correction while achieving image correction which follows a scene change in a video image.
(8) In the image display control device according to this embodiment, the image display control device may calculate the luminance of the lighting after reduction in luminance by performing control of reducing the luminance of the lighting including the first infinite impulse response filtering process based on at least one of the statistical value of the luminance and the statistical value of the chroma, and then may perform correction of the image signal including the second infinite impulse response filtering process based on the calculated luminance of the lighting.
When independently performing the first infinite impulse response filtering process and the second infinite impulse response filtering process, the balance between lighting correction and image correction may be impaired, whereby the image quality may deteriorate. Therefore, the first infinite impulse response filtering process is performed on the lighting luminance calculated in frame units, the amount of image correction is calculated from the results of the first infinite impulse response filtering process, and the second infinite impulse response filtering process is performed on the calculated amount of image correction (i.e., series processing). The balance between the first and second infinite impulse response filtering processes is always maintained by calculating the amount of reduction in lighting luminance and then calculating the amount of image correction depending on the amount of reduction in luminance.
(9) In the image display control device according to this embodiment, the common calculator may include a feedback path, calculation results of the common calculator being at least partially fed back to an input side of the common calculator through the feedback path.
The first and second infinite impulse response filtering processes can be performed by providing the feedback path in the common calculator.
(10) In the image display control device according to this embodiment, the plurality of codes stored in the code storage section may be microcodes obtained by converting an algorithm created using a programming language, the algorithm adaptively reducing the luminance of the image display lighting corresponding to the display image and correcting the image signal to compensate for deterioration in image quality due to the reduction in the luminance of the lighting.
For example, the code table can be efficiently created by collectively converting an algorithm created using a high-level programming language to generate microcodes, and writing the microcodes into a read only memory (ROM). The calculations performed by the common calculator can be relatively easily changed by changing the algorithm (microcodes). This makes it possible to flexibly deal with a change in design.
(11) According to another embodiment of the invention, there is provided a driver device of an electro-optical device, the driver device including one of the above image display control devices.
The image display control device (image display control LSI) according to the embodiment of the invention is mounted on a driver device (driver) of an electro-optical device (including liquid crystal display device). The image display control device (image display control LSI) according to the embodiment of the invention has a real-time capability of processing a video image such as a streaming image and allows a reduction in power consumption and size. Therefore, the added value of the driver device (driver) is increased.
(12) According to a further embodiment of the invention, there is provided a control device of an electro-optical device, the control device including one of the above image display control devices.
The image display control device (image display control LSI) according to the embodiment of the invention is mounted on a control device (controller) of an electro-optical device (including liquid crystal display device). The image display control device (image display control LSI) according to the embodiment of the invention has a real-time capability of processing a video image such as a streaming image and allows a reduction in power consumption and size. Therefore, the added value of the control device (controller) is increased.
(13) According to a further embodiment of the invention, there is provided a drive control device of an electro-optical device, the drive control device including one of the above image display control devices.
The image display control device (image display control LSI) according to the embodiment of the invention is mounted on a drive control device (device in which a driver and a controller are integrated) of an electro-optical device (including liquid crystal display device). The image display control device (image display control LSI) according to the embodiment of the invention has a real-time capability of processing a video image such as a streaming image and allows a reduction in power consumption and size. Therefore, the added value of the drive control device (device in which a driver and a controller are integrated) is increased.
(14) According to a further embodiment of the invention, there is provided an electronic instrument including one of the above image display control devices.
A streaming image distributed by one-segment broadcasting or the like can be displayed with high quality and the life of a battery can be increased by mounting the image display control device (LSI) according to the embodiment of the invention on a portable terminal (including portable telephone terminal, PDA terminal, and portable computer terminal), for example.
Adaptive luminance adjustment control corresponding to a display image and image correction performed by an image display control device (image display control LSI) according to the invention are described below with reference to
Relationship between luminance adjustment control and image correction
According to one aspect of the invention, as shown in
In the invention, as shown in
Amount of Image Correction Accompanying Adaptive Luminance Adjustment
In
The characteristic line A which indicates a change in the backlight luminance reduction rate is analyzed below. As shown in
The characteristic line B which indicates a change in the amount of image correction (Gy) without luminance adjustment is analyzed below. As shown in
The characteristic line C which indicates a change in the amount of image correction (Gy′) with luminance adjustment is analyzed below. As shown in
The characteristic line D which indicates a change in an increase (ΔGy=Gy′−Gy) in the amount of image correction accompanying luminance adjustment is analyzed below. An increase ΔGy in the amount of image correction accompanying luminance adjustment increases as the luminance decreases, and gradually decreases as the luminance increases, as described above. An increase in the amount of image correction gradually increases when the average luminance exceeds about Gammath3. Specifically, since the image quality of an image with a higher luminance may be likely to deteriorate due to a reduction in luminance of the backlight 12, image correction must be enhanced in order to suppress a decrease in luminance of an image with a high average luminance.
Relationship Between Reduction in Power Consumption and ΔGy
As described above, each characteristic line shows a tendency in which an increase ΔGy in the amount of image correction accompanying luminance adjustment increases as the luminance decreases, gradually decreases as the luminance increases, and again increases gradually as the luminance increases. An increase ΔGy in the amount of image correction accompanying luminance adjustment increases as the backlight luminance reduction rate is increased to reduce power consumption.
Enhancement of Chroma Correction
The chroma of the entire screen decreases due to a reduction in luminance of the backlight. Therefore, chroma correction is performed so that the chroma remains the same before and after luminance adjustment. Chroma correction is basically performed according to the following equation (1). The following equation defines the blue chroma (Cb=Y−B). Note that the same equation applies to the red chroma (Cr=Y−R).
Cb[cb]=Fc×Gc+Cb (1)
where, cb indicates a chroma correction input color difference, Cb indicates a chroma correction output color difference, Gc indicates the amount of chroma correction, and Fc indicates a chroma correction coefficient curve.
When the amount of reduction in luminance is determined merely based on the luminance of the image, the brightness (vividness) of red (R) and blue (B) may be impaired due to too large a reduction in luminance. Specifically, since a dark image is affected by a reduction in luminance to a small extent, the luminance is reduced to a large extent. On the other hand, when a large and bright rose or the like is displayed at the center of a dark image, the amount of reduction in luminance is appropriately limited in order to suppress a decrease in chroma of the rose. However, since red (R) and blue (B) contribute to the luminance (Y) to a small extent, the luminance may be reduced to a large extent when the amount of reduction in luminance is determined merely based on the luminance (Y) (i.e., the image is determined to be a dark image). In order to prevent such an excessive reduction in luminance, the amount of reduction in luminance is determined based on the luminance (Y) and the chroma (red chroma (Cr) and blue chroma (Cb)). When the luminance and the chroma satisfy a specific relationship, the amount of reduction in luminance is limited as a result of giving priority to the chroma. This suppresses a reduction in luminance when the image has a high chroma, whereby a decrease in chroma of the display image is suppressed.
In
Filtering Process which Prevents Flicker Accompanying Scene Change
When adaptive lighting luminance adjustment and image correction are performed in each frame of a video image, a visual flicker occurs due to sudden changes in lighting luminance and the amount of image correction accompanying a scene change. Therefore, luminance correction and image correction calculated in frame units are appropriately filtered depending on their characteristics. Specifically, since a change in lighting luminance is a change in black and white and is easily observed visually, a filtering process with a large time constant is performed. On the other hand, since a change in the amount of image correction is a change in halftone and is observed with difficulty, a filtering process with a small time constant is performed taking a quick response to a scene change in a video image into consideration. This makes it possible to effectively suppress a flicker accompanying adaptive luminance correction while achieving image correction following a scene change in a video image.
When independently performing each filtering process, the balance between luminance correction and image correction may be impaired, whereby the image quality may deteriorate. Therefore, a first filtering process is performed on the lighting luminance calculated in frame units, the amount of image correction is calculated from the results of the first filtering process, and a second filtering process is performed on the calculated amount of image correction (i.e., configuration of performing series processing). The balance between the first and second filtering processes is always maintained by calculating the amount of reduction in lighting luminance and then calculating the amount of image correction depending on the amount of reduction in luminance.
As shown in
An image correction amount calculation section 24 calculates the amount of correction Gm of luminance correction and chroma correction based on the final backlight luminance (Kflt). The amount of image correction Gym is filtered using a time-domain filter 26 with a small time constant, whereby the final amount of image correction (Gy′) is calculated. The characteristics of the time-domain filter 26 are controlled based on a filtering coefficient q.
As shown in
The embodiments of the invention are described below with reference to the drawings.
In
In
In
The image display control device (image display control LSI) 108 according to the invention has a real-time capability of processing a video image such as a streaming image and allows a reduction in power consumption and size. Therefore, the added values of the driver device (driver) 110, the control device (controller) 130, the drive control device (device in which a driver and a controller are integrated), and an electronic instrument 100 are increased by mounting the image display control device (image display control LSI) according to the invention.
Entire Configuration of Image Display Control Device
The following description is given on the assumption that the image display control device 108 is mounted on a portable terminal (including portable telephone terminal, PDA terminal, and portable computer terminal). The portable terminal includes the antenna AN which receives one-segment broadcasting, the communication/image processing section 102, and the host computer 106, for example. The host computer 102 supplies the received streaming image signal to the image display control device 108, for example. An image signal captured using a CCD camera may also be supplied to the image display control device 108 (see
As shown in
The image correction core 200 includes a timing section 210 which extracts a synchronization signal from the YUV image signal output from the image input interface (I/F) 150, and generates a timing signal which indicates the operation timing of each section, a histogram creation section (statistical information acquisition section) 212 which acquires statistical information necessary for calculations, a sequence counter 214, a code table 216 which stores microcodes into which a correction algorithm is subdivided, a decoder 217 which decodes the microcodes to generate an instruction and data, a common calculator 218 which includes minimum circuits and is used in common for a luminance adjustment process and an image correction process, a coefficient buffer 220 which temporarily stores an image correction coefficient generated by calculations, and an image correction section 222 which corrects the image signal using the correction coefficient.
The host computer 106 outputs an image signal (RGB format or YUV format). The host computer 106 also outputs the control information including a degree of gamma correction (L1), a degree of contrast (L2), a degree of chroma (L3), an image correction scene weighting coefficient (L4), a backlight luminance reduction rate (degree of reduction in power consumption: L5), and a backlight scene weighting coefficient (L6). The image correction scene weighting coefficient (L4) and the backlight scene weighting coefficient (L6) respectively correspond to the filtering coefficients P and Q shown in
The control information is temporarily stored in the register 152, and supplied to the common calculator 218. The common calculator 218 performs specific calculations using the instruction and data from the decoder 217 based on the supplied control information, and generates the image correction coefficient and the backlight luminance (luminance adjustment coefficient Kflt).
In
The function and the operation of each section of the image correction core 200 shown in
The histogram creation section (statistical information acquisition section) 212 acquires statistical information (i.e., statistical information relating to luminance and statistical information relating to chroma) of an image signal of one frame. A specific internal configuration of the histogram creation section (statistical information acquisition section) 212 is described later in a third embodiment.
The code table (code storage section) 216 stores a plurality of microcodes which specify the operation procedure of the common calculator 218. A procedure of creating the code table 216 is described later in a second embodiment.
The sequence counter (sequence instruction section) 214 specifies the code table 216, and controls the order of output of the microcodes from the code table 216. The decoder 217 decodes the microcodes sequentially output from the code table 216, and generates at least one of an instruction and data (e.g., coefficient) supplied to the common calculator.
The decoder 217 supplies the coefficient used for calculations to the first and second multiplexers (400a and 400b), supplies an operation instruction (operation code) to the arithmetic logic unit (ALU) 402, and supplies destination information to the distributor 404.
The common calculator 218 calculates the image correction coefficient and the backlight luminance (luminance adjustment coefficient Kfit) after reduction in luminance in real time. The digital signal processing described with reference to
The calculations performed by the common calculator 218 are controlled by the microcodes which specify the signal processing procedure, as described above. Real-time calculations can be performed without parallelly providing the same type of hardware by utilizing a common calculator having a minimum circuit configuration. Therefore, high-speed luminance adjustment control and image correction can be implemented using a minimum number of circuits and with minimum power consumption.
The calculation results of the common calculator 218 are temporarily stored in the register groups 408a to 408c classified in output destination units. The calculated backlight luminance (luminance adjustment coefficient Kflt) is output to a backlight (LED) driver, and the correction coefficient is stored in the coefficient buffer 410. The correction coefficient stored in the coefficient buffer 410 is supplied to the image correction section 222 in synchronization with the input of an image signal of the next frame, and image correction (enhancement of luminance and chroma) is performed.
The calculation results stored in the register groups 408a to 408c are at least partially fed back to the input side of the first and second multiplexers (400a and 400b) through the feedback path. The process of calculating the lighting luminance after reduction in luminance, feeding back the calculation results to the input side, and calculating the image correction coefficient based on the calculated luminance is thus performed. The first and second infinite impulse response (IIR) filtering processes are also performed.
This embodiment illustrates a procedure of creating the code table shown in
In
The algorithm created using the programming language is collectively converted to generate microcodes (step S502).
The generated microcodes are written into a read only memory (ROM) (step S502).
The code table 216 can be efficiently created in this manner. Moreover, the calculations of the common calculator 218 can be relatively easily changed by changing the algorithm (microcodes). This makes it possible to flexibly deal with a change in design.
This embodiment illustrates a specific internal configuration of the histogram creation section (statistical information acquisition section) 212 shown in
As described above, the image display control device according to the invention acquires the statistical values relating to the luminance and the chroma of the image signal of one frame, and adaptively corrects the backlight luminance and the image signal (chroma and luminance) based on the statistical values. When the image has a low average luminance but has a high average chroma, the image display control device limits the backlight luminance reduction rate when correcting the image as a result of giving priority to the chroma over a reduction in power consumption. In order to perform such control, it is necessary to quickly acquire the necessary statistical value information relating to the luminance and the chroma.
The luminance signal (Y) of the image signal is parallelly input to the statistical units (EX0 to EX255), and is simultaneously compared by the comparators 1 with the reference luminances (1) to (255) corresponding to the respective grayscales. Each comparator 1 functions as a luminance coincidence detection circuit. The output of the comparator is set at a high level when the input luminance coincides with the reference luminance, whereby an operation clock signal supplied to the other input terminal of the AND gate 3 is supplied to the statistical value buffer 4.
The statistical value buffer 4 acquires and latches the count value of the up-counter 2 at a timing at which the clock signal is supplied. The luminance of each pixel contained in the image signal is thus classified and counted in grayscale units. Since the luminance of the input image is parallelly input to each statistical unit, the statistical values can be acquired at high speed.
A luminance maximum value/minimum value detector 5 calculates the maximum value and the minimum value of the luminance (Y) based on the count value of each statistical unit (EX0 to EX255). A standard deviation calculation section 6 calculates a standard deviation value which indicates the distribution of the luminance (Y). Adaptive luminance adjustment and image correction are performed using the statistical values thus calculated.
As shown in
Specifically, each statistical unit (ES(Y), ES(Cb), and ES(Cr)) includes an adder (7a to 7c) which accumulates the Y, Cb, or Cr values, and a total value buffer (8a to 8c) which stores the accumulated value. Average value calculation sections (9a to 9c) respectively calculate and output the average value of the luminance (Y), the average value of the chroma (Cb), and the average value of the chroma (Cr).
As described with reference to
An AND gate A1 shown at the lower left in
The invention has been described above based on the embodiments. Note that the invention is not limited to the above embodiments. Various modifications, variations, and applications may be made without departing from the spirit and scope of the invention.
According to at least one aspect of the invention, the following effects can be obtained, for example.
(1) Real-time calculations can be implemented without parallelly providing the same type of hardware by utilizing a microprogram-controlled common calculator, whereby high-speed adaptive luminance adjustment control and adaptive image correction can be implemented using a minimum number of circuits and with minimum power consumption.
(2) A decrease in chroma can be suppressed by enhancing not only the luminance but also the chroma, thereby making it possible to more effectively compensate for deterioration in image quality due to a reduction in luminance.
(3) The amount of reduction in luminance is limited when the image has a high chroma by determining the amount of reduction in luminance taking the luminance and the chroma into consideration. This makes it possible to effectively prevent a decrease in chroma due to an excessive reduction in luminance.
(4) A flicker (visual flicker) can be effectively suppressed while ensuring a quick response to a scene change of a video image by performing the infinite impulse response (IIR) filtering process during luminance correction and image correction and increasing the time constant of the filtering process for luminance correction.
(5) The balance between the filtering process accompanying luminance adjustment control and the filtering process accompanying image correction is always maintained by calculating the amount of reduction in lighting luminance and then calculating the amount of image correction depending on the amount of reduction in luminance (i.e., employing series processing).
(6) According to the invention, power consumption can be significantly reduced by adaptive reduction in lighting luminance while minimizing deterioration in image quality (it has been confirmed that power consumption is reduced by 30% at maximum). Since the process can be implemented using minimum hardware, the space occupied by the device can be reduced.
(7) According to the invention, the added values of a driver device (driver), a control device (controller), and a drive control device (device in which a driver and a controller are integrated) of a liquid crystal display device and the like can be increased.
(8) A streaming image distributed by one-segment broadcasting and the like can be displayed with high quality and the life of a battery can be increased by mounting the image display control device (LSI) according to the invention on a portable terminal (including portable telephone terminal, PDA terminal, and portable computer terminal).
(9) According to the invention, adaptive reduction in lighting luminance and highly accurate image correction which compensates for deterioration in image quality due to a reduction in luminance can be implemented at the same time while achieving a high-speed capability (real-time capability), reducing power consumption, and suppressing an increase in circuit scale.
The invention is useful for an image display control device (image display control LSI) which adaptively reduces the luminance of display lighting corresponding to the display image and corrects an image signal to compensate for deterioration in image quality due to a reduction in luminance, a driver device (driver) of a display panel, a control device (controller) of a display panel, a drive control device (device in which a driver and a controller are integrated) of a display panel, an electronic instrument such as a portable terminal, and the like which include the image display control device.
Although only some embodiments of the invention have been described above in detail, those skilled in the art would readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of the invention. Accordingly, such modifications are intended to be included within the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-304667 | Nov 2006 | JP | national |
| 2007-272738 | Oct 2007 | JP | national |
