JP2012220717A - Image processing circuit, semiconductor device, and image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing circuit capable of performing backlight control based on an image analysis result and an illuminance detection result and to provide a semiconductor device and an image processing device.SOLUTION: An image processing IC 20 includes: a luminance correction part 21 performing luminance correction of an input image, to produce an output image; a luminance average value calculation part 22 calculating a luminance average value of the output image; a luminance average value calculation part 23 calculating a luminance average value of the input image; a selector 24; a difference calculation part 25 calculating a difference between the luminance average values; a duty value calculation part 26 deciding a duty value based on the luminance average values or the difference value; a resister 27 storing a table used for deciding the duty value; a duty value calculation part 28 calculating the duty value of an input PWM signal; and a cooperative processing part 29 to which a plurality of control signals indicating the duty value are inputted to decide the duty value of an output PWM signal based on the duty value indicated by both control signals.

Description

  The present invention relates to an image processing circuit, a semiconductor device formed by integrating the image processing circuit, and an image processing apparatus using the same.

  Conventionally, a backlight control of LCD (Liquid Crystal Display) when displaying an image has disclosed a control method for performing backlight control based on the result of analyzing the gradation of the image and the illuminance detected by the illuminance sensor. It has been proposed (see, for example, Patent Document 1 and Patent Document 2).

JP 2009-294323 A International Publication No. 2008/117784

  However, the conventional backlight control IC can perform only one of the backlight control based on the image analysis result or the backlight control based on the detection result of the illuminance sensor.

  On the other hand, an image processing apparatus including an LCD includes an image processing IC in addition to the backlight control IC. The image processing IC generates output image data by performing luminance conversion processing or the like on the input image data. However, the conventional image processing IC only supplies output image data to the LCD, and the backlight control of the LCD (particularly the backlight control according to the image analysis result and the detection result of the illuminance sensor). It was not a consideration for compatibility with light control.

  In view of the above problems found by the inventors of the present application, the present invention achieves both backlight control based on image analysis results and backlight control based on illuminance detection results in addition to image data analysis processing. It is an object of the present invention to provide an image processing circuit that can be used, a semiconductor device in which the image processing circuit is integrated, and an image processing apparatus using the same.

  In order to achieve the above object, an image processing circuit according to the present invention includes an image processing unit that performs image processing on input image data to generate output image data, and a duty of an externally input PWM (Pulse Width Modulation) signal. A first duty control unit for determining a value and generating a first control signal indicating the duty value; a duty value based on a processing result of the image processing unit; and a second control signal indicating the duty value A configuration (first configuration) including: a second duty control unit to be generated; and a cooperative processing unit that determines a duty value of a PWM signal to be output based on the first control signal and the second control signal; Has been.

  In the image processing circuit having the first configuration, the cooperative processing unit multiplies the duty value indicated by the first control signal by the duty value indicated by the second control signal, and outputs the PWM signal. It is preferable to adopt a configuration (second configuration) for determining the duty value.

  In the image processing circuit having the second configuration, the first duty control unit receives the PWM signal generated based on the illuminance detection result of the illuminance sensor, determines the duty value of the PWM signal, and The first control signal indicating the duty value may be generated (third configuration).

  In the image processing circuit having the third configuration, the image processing unit generates the output image data from the input image data based on a luminance histogram of the input image data, and the image processing circuit A first luminance average value calculating unit that calculates a luminance average value of the output image data; and the second duty control unit determines a duty value based on the luminance average value and indicates the duty value. It is preferable to adopt a configuration (fourth configuration) characterized in that two control signals are generated.

  The image processing circuit having the fourth configuration further includes a register for storing a first table in which the luminance average value and the duty value of the output image data are associated with each other, and the second duty control unit has a duty cycle It is preferable to use a configuration (fifth configuration) in which the first table is referred to when determining a value.

  The image processing circuit having the fifth configuration is calculated by the second luminance average value calculation unit that calculates the luminance average value of the input image data and the first luminance average value calculation unit. A difference calculating unit that calculates a difference value between the average luminance value calculated and the average luminance value calculated by the second average luminance value calculating unit, wherein the second duty control unit is based on the differential value. It is preferable to adopt a configuration (sixth configuration) that determines the duty value and generates the second control signal indicating the duty value.

  The image processing circuit having the sixth configuration further includes a register that stores a second table in which the difference value and the duty value are associated, and the second duty control unit is configured to determine the duty value when determining the duty value. A configuration referring to the second table (seventh configuration) may be employed.

  The semiconductor device according to the present invention has a configuration (eighth configuration) in which the image processing circuits having any one of the first to seventh configurations are integrated.

  An image processing apparatus according to the present invention has a configuration (ninth configuration) including the semiconductor device having the eighth configuration and an image input unit that supplies the input image data to the semiconductor device. Yes.

  The image processing apparatus having the ninth configuration may further include an interface unit (tenth configuration) for rewriting the contents of the first table and the second table.

  According to the present invention, there are provided an image processing circuit capable of performing luminance control in cooperation with an illuminance detection result and an image analysis result, a semiconductor device integrated with the image processing circuit, and an image processing device using the image processing circuit. It becomes possible to do.

1 is a block diagram showing a first embodiment of an image processing apparatus according to the present invention. Time chart for explaining the overall flow of image processing Flowchart for explaining calculation processing of luminance conversion coefficient Schematic diagram for explaining the mode of area division Schematic diagram for explaining a state in which a virtual area is set Schematic diagram for explaining the mode of the low-pass filter Schematic diagram for explaining bilinear calculation The block diagram which shows 2nd Embodiment of the image processing apparatus which concerns on this invention. Schematic diagram showing the first conversion table Schematic diagram showing the second conversion table Waveform diagram showing the waveform of the PWM signal

<First Embodiment>
FIG. 1 is a block diagram showing a first embodiment of an image processing apparatus according to the present invention. The image processing apparatus 1 according to the first embodiment includes an imaging unit 10, a luminance conversion processing unit 11, a luminance conversion coefficient calculation unit 12, a luminance conversion coefficient storage unit 13, and an output unit 14.

  The imaging unit 10 includes a predetermined lens group, an imaging device (for example, a CMOS [Complementary Metal-Oxide Semiconductor] sensor or a CCD [Charge Coupled Devices] sensor), and the like, and forms an optical image of the subject. Imaging processing (for example, moving image capturing at 30 frames per second). The input image data generated by the imaging unit 10 is sequentially output to the luminance conversion processing unit 11 and the luminance conversion coefficient calculation unit 12. The means for generating input image data is not limited to the imaging unit 10, and other image input units (such as a media playback device or a broadcast receiving device) may be used.

  The luminance conversion processing unit 11 performs luminance conversion processing on the input image data from the imaging unit 10 to generate output image data. This luminance conversion process is performed by converting the luminance value of each pixel included in the input image data according to the luminance conversion coefficient stored in the luminance conversion coefficient storage unit 13. Note that the output image data generated by the luminance conversion processing unit 11 is sequentially output to the output unit 14.

  The luminance conversion coefficient calculation unit 12 calculates the luminance conversion coefficient used for the luminance conversion processing based on the image data (input image) for each frame input from the imaging unit 10. The content of the luminance conversion coefficient and the method for calculating the luminance conversion coefficient will be described later.

  The luminance conversion coefficient storage unit 13 stores the luminance conversion coefficient calculated by the luminance conversion coefficient calculation unit 12 at least until the luminance conversion process related to the next frame is executed. This stored content is used in the luminance conversion processing in the luminance conversion processing unit 11.

  The output unit 14 includes a display such as an LCD [Liquid Crystal Display] (for example, an in-vehicle monitor), and sequentially displays output image data that has been subjected to luminance conversion processing by the luminance conversion processing unit 11.

  The image processing apparatus 1 configured as described above performs predetermined luminance conversion processing on the input image data obtained by the imaging unit to generate output image data, and performs video display according to the output image data.

  Of the above-described components, the luminance conversion processing unit 11, the luminance conversion coefficient calculation unit 12, and the luminance conversion coefficient storage unit 13 may be integrated in a semiconductor device.

  Next, the overall flow of image processing in the image processing apparatus 1 will be described with reference to FIG.

  FIG. 2 is a diagram for explaining the overall flow of image processing in the image processing apparatus 1. As shown in this figure, when input image data related to the nth frame arrives, the luminance conversion coefficient calculation unit 12 calculates a luminance conversion coefficient based on the input image data. As a result, a luminance conversion coefficient determined based on the nth frame is obtained, and is temporarily stored in the luminance conversion coefficient storage unit 13.

  On the other hand, the luminance conversion processing unit 11 determines the input image data related to the incoming nth frame based on the (n−1) th frame already stored in the luminance conversion coefficient storage unit 13. Luminance conversion processing is performed using the obtained luminance conversion coefficient.

More specifically, for a pixel at coordinates (i, j) in the nth frame, the luminance before luminance conversion processing is Iij (n), the luminance after luminance conversion processing is Oij (n), and (n−1) ) If the luminance conversion coefficient determined for the pixel at coordinates (i, j) based on the first frame is Tij (n−1), the luminance related to each pixel in each frame is (1) Conversion processing is performed based on the expression. Then, the output image data that has been subjected to the luminance conversion processing by the luminance conversion processing unit 11 is output through the output unit 14.
Oij (n) = Tij (n−1) × Iij (n) (1)

  As described above, the image processing apparatus 1 according to the present embodiment uses the luminance conversion coefficient determined based on the (n−1) th frame for the input image data related to the nth frame. It is set as the structure which performs a conversion process. Therefore, it is possible to execute the nth luminance conversion process and the image output without waiting for the calculation of the nth luminance conversion coefficient. As a result, it is possible to output the output image data obtained by subjecting the input image data to the luminance conversion process at the earliest possible time, and it is possible to output an image near real time.

  Note that it is possible to perform luminance conversion processing on the input image data related to the nth frame using a luminance conversion coefficient determined based on the (n−2) th and previous frames. It should be noted that the accuracy of conversion processing becomes a problem when luminance conversion coefficients based on very old frames are used. This problem is particularly noticeable when moving image data having a large movement as input image data. Also, for example, when still image data is handled as input image data, the luminance is calculated using the luminance conversion coefficient determined based on the nth frame for the input image data related to the nth frame. Conversion processing may be performed.

  Next, the content of the luminance conversion coefficient calculation process will be described with reference to the flowchart of FIG.

  FIG. 3 is a flowchart for explaining the luminance conversion coefficient calculation processing in the image processing apparatus 1. In the process exemplified in this flowchart, first, area division is performed on input image data for one frame (step S11).

  FIG. 4 is a diagram for explaining a mode of area division in the image processing apparatus 1. In the example of this figure, it is assumed that one frame is composed of 40 × 64 (= 2560) pixels, and one area is 8 × 8 pixels in size. Accordingly, the total number of areas is 5 vertical areas × 8 horizontal areas = 40 areas. Each area will be referred to as A0, A1,..., An,.

  When the area division is completed, the area-specific conversion coefficient is calculated (step S12 in FIG. 3). This area-specific conversion coefficient is determined for each area, and is common to each pixel in the area. When calculating the conversion coefficient for each area, a luminance histogram for each area is calculated instead of the luminance histogram for the entire frame, and then the conversion coefficient is calculated based on the luminance histogram for each area. According to the area-specific conversion coefficients calculated in this way, for each divided area, the wider the luminance range in the input image data, the wider the luminance range in the output image data.

  In step S12 of FIG. 3, area-specific conversion coefficients are calculated for all areas in the image area. That is, a unique area-specific conversion coefficient is determined for each area. Then, the area-specific conversion coefficient may be directly used as the luminance conversion coefficient, and the luminance conversion processing of the input image data may be executed. As a result, even when a portion having a large luminance difference as compared with the entire image partially exists, a good contrast including the portion can be obtained.

  However, the area-specific conversion coefficient does not basically consider luminance information outside the area, that is, other areas. For this reason, the difference in luminance is conspicuous (brightness distribution has a high frequency) at the boundary between areas, and an image that is not good in terms of smoothness may be output. Therefore, in this embodiment, filter processing or the like is performed on the area-specific conversion coefficients calculated for each area. The contents of this process will be specifically described.

  First, prior to execution of filter processing or the like, a virtual area having the same scale as the above-described area is set outside the image area.

  FIG. 5 is a diagram for explaining a state in which virtual areas (A40 to A69 in the figure) are set.

  Then, virtual area-specific conversion coefficients (hereinafter referred to as virtual coefficients) are set for these virtual areas A40 to A69 (step S13 in FIG. 3). As will be described later, this virtual coefficient is used to allow normal filtering processing to be performed on an area near the outer edge of the image area, and takes the same form as the area-specific conversion coefficient. Is.

  The virtual coefficient is set with reference to each area adjacent to the virtual area (each area located at the outer edge of the image area) with reference to the area-specific conversion coefficient of the area existing at a symmetric position with the virtual area. . For example, since A41 is symmetric with A8 with respect to A0, the virtual coefficient of A41 has the same value as the area-specific conversion coefficient of A8. Similarly, since A42 is symmetric with A9 with respect to A1, the virtual coefficient of A42 is set to the same value as the area-specific conversion coefficient of A9. On the other hand, since A40 located at the four corners is symmetrical with A9 with respect to A0, the virtual coefficient of A40 has the same value as the area-specific conversion coefficient of A9.

  In addition to the above, the virtual coefficient setting method may be set to be symmetric with respect to the outer edge of the image area (thick line in FIG. 5), for example. In this case, since A41 is symmetrical with A0 with respect to the outer edge of the image area, the virtual coefficient of A40 is set to the same value as the area-specific conversion coefficient of A0. Similarly, since A42 is symmetric with A1 with respect to the outer edge of the image area, the virtual coefficient of A42 is set to the same value as the area-specific conversion coefficient of A1. On the other hand, A40 located at the four corners is symmetric with A0 with respect to the outer edge of the image area, so the virtual coefficient of A40 is the same value as the area-specific conversion coefficient of A0.

  After setting the virtual coefficient for each virtual area in this way, next, a process (filter process) for applying a low-pass filter in the image space is performed on the area-specific conversion coefficient in each area in the image area (FIG. 5). 3 step S14).

  FIG. 6 is a diagram for explaining an aspect of the low-pass filter.

  According to this, when a filter is applied to a certain area of interest, the area-specific conversion coefficients of areas existing in a predetermined range around the area of interest (in this case, the four areas on the top, bottom, left and right) are used. However, when a part of the predetermined range protrudes from the image area, the virtual coefficient assigned to the virtual area at that position is assumed to be the area-specific conversion coefficient.

For example, the area-specific conversion coefficient a ′ (0) after the filtering process in the area A0 is as follows. Note that a (n) represents the area-specific conversion coefficient in the area An (n = 0, 1, 8, 41, 50) before the filter processing. Further, a (41) and a (50) are virtual coefficients in the virtual areas A41 and A50, respectively.
a ′ (0) = a (0) / 2 + {a (1) + a (8) + a (41) + a (50)} / 8

  Such a filtering process can reduce the difference in luminance even when the difference in luminance is conspicuous at the boundary between areas. In the present embodiment, the low-pass filter shown in FIG. 6 has been described. However, the conversion coefficient for each area relating to the area up to which range is considered, and how the weighting for each area in the filter is performed. About etc., it can be set as various aspects.

  The area-specific conversion coefficient that has been subjected to the filtering process described above may be directly used as the luminance conversion coefficient, and the luminance conversion process of the input image data may be executed. However, in this embodiment, in order to further obtain the smoothness of the output image, a pixel-specific conversion coefficient determined for each pixel (not necessarily common to each pixel even in the same area) is calculated (step in FIG. 3). S15), and this is applied as a luminance conversion coefficient (step S16 in FIG. 3).

  Here, a calculation method (bilinear calculation) of the conversion coefficient for each pixel will be described with reference to FIG.

  FIG. 7 is a diagram for explaining bilinear calculation. In determining the pixel-specific conversion coefficient for a certain target pixel, attention is paid to four areas related to the vicinity of the pixel. For example, when the pixel P in FIG. 7 is the target pixel, attention is paid to the areas A0, A1, A8, and A9. In other words, four areas are selected so that each area shares one vertex and the pixel of interest is located inside a quadrilateral formed by connecting the centers of the areas.

  The pixel-by-pixel conversion coefficients of the target pixel P are the area-specific conversion coefficients {a ′ (0), a ′ (1), a ′ (8), a ′ () after the filtering process in each of these four areas. 9)}, the position of the target pixel P, and the center position in each of the four areas.

More specifically, as shown in FIG. 7, the horizontal distance between the areas is X, the vertical distance between the areas is Y, the horizontal distance between the center of the area A0 and the target pixel P is a, and the vertical distance is the same. When the distance in the direction is b, the pixel-by-pixel conversion coefficient p (P) of the target pixel P is obtained as follows.
p (P) = {a ′ (0) × (X−a) × (Y−b)
+ A ′ (1) × a × (Y−b)
+ A ′ (8) × (X−a) × b
+ A ′ (9) × a × b} / (X × Y)

  Even in the bilinear calculation, if the target pixel is in the vicinity of the outer edge of the image area, it is conceivable that a part of the four areas of interest will protrude from the image area. Even in such a case, a normal bilinear calculation can be performed by setting a virtual area and a virtual coefficient as in the case of the filter processing described above.

  With this method, pixel-specific conversion coefficients are calculated for all pixels in the image area, and these are used as luminance conversion coefficients for the corresponding pixels. Accordingly, the pixel-specific conversion coefficient is calculated based on the area-specific conversion coefficient so that the luminance change is smooth including the boundary portion between the areas. As a result, it is possible to avoid the occurrence of a discontinuous portion of luminance change as much as possible, and it becomes easy to output a more beautiful image.

  As described above, in the case of the image processing apparatus 1 according to the present embodiment, even if there is a portion related to the luminance (or luminance range) having a low appearance frequency when viewed from the entire image, a good contrast including the portion is obtained. Can be obtained.

Second Embodiment
Next, a second embodiment of the image processing circuit according to the present invention will be described in detail. FIG. 8 is a block diagram showing a second embodiment of the image processing circuit according to the present invention.

  The image processing IC 20 calculates a luminance conversion coefficient based on the luminance histogram of the input image obtained by the imaging unit 10, and performs a luminance conversion process corresponding to the luminance conversion coefficient on each pixel constituting the input image. A semiconductor device that generates a desired output image. As shown in FIG. 8, the image processing IC 20 performs a luminance conversion process on DI that is an input image signal input from the imaging unit 10 or the like, and generates and outputs DO that is an output image signal.

  First, a device externally connected to the image processing IC 20 will be described. The illuminance sensor 90 generates a detection signal corresponding to the illuminance of ambient light and sends it to the CPU 91. Note that the illuminance sensor 90 is desirably disposed as close to the image processing apparatus 1 as possible in order to accurately measure the illuminance of ambient light incident on the image processing apparatus 1. A photodiode or a phototransistor can be used as the light receiving element of the illuminance sensor 90.

  Further, the image processing IC 20 performs cooperative processing described later on PWMI that is an input PWM signal input from the CPU 91 or the like, generates PWMO that is an output PWM signal, and outputs the PWMO to the backlight 30.

  Based on the detection signal obtained by the illuminance sensor 90, the CPU 91 determines a duty value for generating a PWM signal for backlight control. Then, using the determined duty value, PWMI is generated and sent to the image processing IC 20.

  The interface unit 92 is for the user to rewrite information stored in a register 27 described later. More specifically, it is configured to include operation buttons, control signal input terminals (both not shown), or the like.

  The image processing IC 20 includes a luminance correction unit 21, a luminance average value calculation unit 22, a luminance average value calculation unit 23, a selector 24, a difference calculation unit 25, a duty value calculation unit 26, a register 27, and a duty value. The calculation unit 28 and the cooperation processing unit 29 are integrated.

  The luminance correction unit 21 performs luminance correction on DI to generate DO, and outputs the DO to the output unit 14 and a luminance average value calculation unit 22 described below. The details of the luminance correction processing performed by the luminance correction unit 21 are the same as the processing performed by the luminance conversion processing unit 11, the luminance conversion coefficient calculation unit 12, and the luminance conversion coefficient 13 of the first embodiment. Description is omitted.

  The luminance average value calculation unit 22 calculates the luminance average value of the output image by monitoring the luminance component included in the DO. Then, the calculated luminance average value is sent to the duty value calculation unit 26 via the selector 24. The above-described calculation of the luminance average value is performed by acquiring a luminance histogram included in DO, for example. Alternatively, it may be calculated by adding the luminance value of each pixel of DO and dividing by the total number of pixels.

  The luminance average value calculation unit 23 acquires the luminance histogram of the input image by monitoring the luminance average included in the DI, and calculates the luminance average value. Then, the calculated luminance average value is sent to the difference calculation unit 25. The details of the process performed by the luminance average value calculation unit 23 are the same as those of the luminance average value calculation unit 22.

  The selector 24 outputs only one of the signal input from the luminance average value calculation unit 22 and the signal input from the difference calculation unit 25 to the duty value calculation unit 26. That is, only one of the signal indicating the calculation result of the luminance average value of the output image and the signal indicating the difference value of the luminance average value is output to the duty value calculation unit 26. The determination of which to output is made based on the user designation received using the interface unit 92 or the like.

  For example, when the user wants to determine the duty value using the luminance average value by operating the selector 24, the user can switch to send the signal input from the luminance average value calculation unit 22 to the duty value calculation unit 26. Is possible. In addition, when it is desired to determine the duty value using the luminance average value difference, it is possible to switch so that a signal input from the difference calculation unit 25 is sent to the duty value calculation unit 26.

  The difference calculation unit 25 calculates a difference value between the luminance average value calculated with the luminance average value 22 and the luminance average value calculated with the luminance average value 23. Then, a signal indicating the calculated difference value is sent to the duty value calculation unit 26 via the selector 24.

  The duty value calculation unit 26 calculates the duty value of the PWM signal used for controlling the backlight 30 based on the luminance average value input from the luminance average value 22 or the luminance average value difference input from the difference calculation unit 25. calculate. Then, a control signal S2 (second control signal) indicating the calculated duty value is output to the cooperation processing unit 29 described later.

  More specifically, the duty value calculation unit 26 determines the duty value of the PWM signal by performing table conversion on the luminance average value input from the luminance average value 22. The first table used for conversion is stored in the register 27 in advance.

  The duty value calculation unit 26 determines the duty value of the PWM signal by performing table conversion on the luminance average value difference input from the difference calculation unit 25. The second table used for conversion is stored in the register 27 in advance.

  Note that which of the above two processes the duty value calculation unit 26 performs is determined according to the type of input data. That is, when the luminance average value is input, the first table is referred to, and when the luminance average value difference is input, the second table is referred to.

  The register 27 is a first table (FIG. 9) that associates the average luminance value of the input image data with the duty value (FIG. 9), and a second table (FIG. 10) that associates the difference value calculated by the difference calculation unit 25 with the duty value. ) And. The duty value calculation unit 26 refers to the first table or the second table when determining the duty value.

  FIG. 9 is a diagram illustrating an example of a first table used by the duty value calculation unit 26. Note that the horizontal axis of FIG. 9 indicates the luminance average value obtained by the luminance average value calculation unit 22, and the vertical axis indicates the duty value of the PWM signal.

  FIG. 10 is a diagram illustrating an example of the second table used in the duty value calculation unit 26. In addition, the horizontal axis of FIG. 10 has shown the brightness | luminance average value difference obtained by the difference value calculation part 25, and the vertical axis | shaft has shown the duty value of the PWM signal.

  By using the above conversion table, it is possible to arbitrarily set the correlation between the luminance average value or luminance average value difference and the duty value of the PWM signal, and thus the high level width (H width) of the PWM signal. It becomes possible. Further, the above conversion table is arbitrarily rewritten by the user using the interface unit 92.

  The duty value calculation unit 28 measures the PWMI waveform and calculates the PWMI duty value. Then, the control signal S1 (first control signal) indicating the calculated duty value is output to the cooperation processing unit 29.

  The cooperation processing unit 29 inputs S1 and S2, and determines the duty value of PWMO based on the duty value indicated by both control signals. Then, PWMO with the determined duty value is generated and sent to the backlight 30.

  More specifically, the cooperation processing unit 29 determines the duty value of PWMO by multiplying the duty values indicated by the both control signals. An example of this calculation process will be described with reference to FIG.

  FIG. 11A shows the waveform of PWMI, and the duty value of PWMI schematically represents a PWM signal that can be generated based on S1. FIG. 11B shows the waveform of PWMO. FIG. 11C schematically shows a PWM signal that can be generated based on S2.

  As shown in FIG. 11, the PWM signal is a pulse signal that alternately repeats a high level period (on period) and a low level period (off period) in a predetermined cycle. By variably controlling the duty value, it is possible to adjust the average value of the drive current flowing through the backlight 30. That is, the backlight 30 becomes brighter as the duty value of the PWM signal is increased, and the backlight 30 is darker as the duty value of the PWM signal is decreased.

When the duty value indicated by S1 is d (S1), the duty value indicated by S2 is d (S2), and the duty value of PWMO is d (S3), the cooperative processing unit 29 sets d (S3) as follows: Ask.
d (S3) = d (S1) × d (S2)

For example, as shown on the left side of the figure, when the duty value of S1 is 50% and the duty value of S2 is 100%, the cooperative processing unit 29 performs the calculation as follows.
(50/100) × (100/100) = (50/100)
As a result, the duty value of PWMO is 50%.

For example, as shown in the center of the figure, when the duty value of S1 is 50% and the duty value of S2 is 50%, the cooperative processing unit 29 performs the calculation as follows.
(50/100) × (50/100) = (25/100)
As a result, the duty value of PWMO is 25%.

For example, as shown on the right side of the figure, when the duty value of S1 is 50% and the duty value of S2 is 25%, the cooperative processing unit 29 performs the calculation as follows.
(50/100) × (25/100) = (12.5 / 100)
As a result, the duty value of PWMO is 12.5%.

As described above, by multiplying the duty value indicated by S1 and the duty value indicated by S2, a PWM signal is generated in consideration of both the detection result by the illuminance sensor 90 and the luminance correction result by the luminance correction unit 21. It is possible. Thereby, it is possible to implement luminance control in which the illuminance detection result and the image analysis result are coordinated.
<Other variations>

  The configuration of the present invention can be variously modified in addition to the above-described embodiment without departing from the gist of the invention. That is, the above-described embodiment is an example in all respects and should not be considered as limiting, and the technical scope of the present invention is not the description of the above-described embodiment, but the claims. It should be understood that all modifications that come within the meaning and range of equivalents of the claims are included.

  Note that the above embodiment is premised on luminance control in units of frames, and therefore local dimming is not performed. However, the luminance control according to the present invention may be implemented in local dimming in which luminance control is performed in units of pixels (or areas). At this time, the content of the conversion table can be changed as appropriate in accordance with the control content of the local dimming.

  In the above embodiment, S2 is generated based on the luminance correction result by the luminance correction unit 21. However, S2 may be generated based on other image processing results, for example, processing results such as color tone conversion processing. Good.

  As the image processing apparatus of the present invention, for example, a personal computer or the like having a video content playback function provided via the Internet can be used in addition to apparatuses such as a television apparatus, a hard disk recorder, and a video camera.

  The present invention relates to an image processing circuit that generates input image data by performing luminance conversion processing on input image data, a semiconductor device integrated with the image processing circuit, and an image processing device using the image processing circuit. It is a useful technique for enhancing.

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 10 Imaging part 11 Luminance conversion process part 12 Luminance conversion coefficient calculation part 13 Luminance conversion coefficient memory | storage part 14 Output part 20 Image processing IC (semiconductor device)
21 Brightness correction unit (image processing unit)
22 Luminance average value calculation unit (first luminance average value calculation unit)
23 Luminance average value calculation unit (second luminance average value calculation unit)
24 selector 25 difference calculation unit 26 duty value calculation unit (second duty control unit)
27 Register 28 Duty Value Calculation Unit (First Duty Control Unit)
29 Cooperative Processing Unit 30 Backlight 90 Illuminance Sensor 91 CPU
92 Interface part

Claims (10)

An image processing unit that performs image processing on input image data to generate output image data;
A first duty control unit for determining a duty value of an externally input PWM (Pulse Width Modulation) signal and generating a first control signal indicating the duty value;
A second duty control unit that determines a duty value based on a processing result of the image processing unit and generates a second control signal indicating the duty value;
An image processing circuit comprising: a cooperative processing unit that determines a duty value of a PWM signal to be output based on the first control signal and the second control signal.   The said cooperation processing part determines the duty value of the PWM signal to output by multiplying the duty value which the said 1st control signal shows, and the duty value which the said 2nd control signal shows. An image processing circuit according to 1.   The first duty control unit receives the PWM signal generated based on the illuminance detection result of the illuminance sensor, determines the duty value of the PWM signal, and generates the first control signal indicating the duty value. The image processing circuit according to claim 2, wherein: The image processing unit generates the output image data from the input image data based on a luminance histogram of the input image data;
The image processing circuit further includes a first luminance average value calculation unit that calculates a luminance average value of the output image data,
The image processing circuit according to claim 3, wherein the second duty control unit determines a duty value based on the average luminance value and generates the second control signal indicating the duty value. A register that stores a first table that associates a luminance average value and a duty value of the output image data;
The image processing circuit according to claim 4, wherein the second duty control unit refers to the first table when determining a duty value. The image processing circuit includes a second luminance average value calculating unit that calculates a luminance average value of the input image data, a luminance average value calculated by the first luminance average value calculating unit, and the second luminance average value calculating unit. A difference calculation unit that calculates a difference value from the luminance average value calculated by
The image processing circuit according to claim 5, wherein the second duty control unit determines a duty value based on the difference value and generates the second control signal indicating the duty value. A register for storing a second table associating the difference value with the duty value;
The image processing circuit according to claim 6, wherein the second duty control unit refers to the second table when determining a duty value.   8. A semiconductor device, wherein the image processing circuit according to claim 1 is integrated.   An image processing apparatus comprising: the semiconductor device according to claim 8; and an image input unit that supplies the input image data to the semiconductor device.   The image processing apparatus according to claim 9, further comprising an interface unit for rewriting contents of the first table and the second table.