JP2007300184A - Color temperature correcting circuit and television set employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimally correct a white color temperature, depending on an area of a white region in an image. <P>SOLUTION: A circuit includes a white color degree detector for detecting the white color degree from an RGB luminance signal; a white region area calculator for calculating the area of a continuous white region to be displayed on a display unit from an output of the white degree detector; and a color temperature corrector for correcting the color temperature of the continuous white region, on the basis of the area of the continuous white region calculated by the white region area calculator. In the circuit, the color temperature is corrected depending on the area of a white color in an image, and thus, the color temperature is preferably corrected even if the area is small or large. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a color temperature correction circuit, a television apparatus using the same, a program, and a recording medium.

  2. Description of the Related Art Conventionally, in a color television apparatus, a color temperature is set to be high in order to match white color reproduction with viewers' preference. However, there is a problem that if the color temperature is set high, the reproducibility of colors other than white deteriorates.Therefore, various methods have been considered in which the color temperature is corrected only in the white part and no correction is applied to the colored part. Yes.

  As an example, Japanese Patent Application Laid-Open No. 2004-228867 describes a method for obtaining whiteness from the maximum and minimum values of RGB three primary colors of an input video signal and correcting the color temperature according to the whiteness.

  In order to compensate for the poor white appearance due to the decrease in screen brightness when the average video level (APL) is high in a plasma display, a method for increasing the color temperature of white when the APL is high is described below. It is described in Patent Document 2.

  Further, in Patent Document 3 below, the luminance of an original image is corrected on the basis of a blurred image that lowers the luminance of a high-luminance portion that occupies a predetermined area or more and lowers the contrast of the portion. It is described to adapt to the sensitivity of the eyes.

JP 2005-051745 A JP 09-281927 A JP 2001-344601 A

  By adopting the method as described in the conventional example, it is possible to increase the color temperature of only white and colors close to white. However, the preferred white color temperature tends to depend on the size of the white region, and even a white having a preferred color temperature with a small area may be too unfavorable because it is too blue.

  In Patent Document 1, since white is uniformly corrected regardless of the area occupied in the image, a large area of white is displayed when the correction amount is set large in order to enhance the correction effect on the small area of white. Sometimes it becomes overcorrected. For this reason, the correction amount of the color temperature is set so as to be appropriate in displaying a large area white, and there is a problem that a higher correction effect cannot be obtained for a small area white.

Moreover, in patent document 2, since control which raises the color temperature of white when APL is high was performed, there existed a problem that white of a small area could not be displayed favorably. Further, Patent Document 3 discloses correction of luminance, but does not disclose correction of color temperature. Therefore, there is a problem that cannot be referred to when correcting color temperature.
The present invention has been made in view of the above-described problems, and an object of the present invention is to optimally correct the white color temperature in accordance with the white area in the image.

  The color temperature correction circuit of the present invention is a color temperature correction circuit used in a display device that inputs an RGB luminance signal and displays a color image on a display unit, and detects whiteness from the RGB luminance signal. A white area calculating unit that calculates an area of a continuous white region displayed on the display unit from an output of the whiteness detecting unit, and an area of the continuous white region calculated by the white area calculating unit And a color temperature correction unit for correcting the color temperature of the continuous white area.

  The television apparatus of the present invention includes the color temperature correction circuit described above.

  The color temperature correction method of the present invention is a color temperature correction method used in a display device that inputs an RGB luminance signal and displays a color image on a display unit, and detects whiteness from the RGB luminance signal. A white area calculating step of calculating an area of a continuous white region displayed on the display unit from an output detected in the whiteness detecting step, and a continuous white calculated in the white area calculating step And a color temperature correction step of correcting the color temperature of the continuous white area based on the area of the area.

  The program of the present invention is a program for causing a computer to execute a color temperature correction method used in a display device that inputs an RGB luminance signal and displays a color image on a display unit, and detects whiteness from the RGB luminance signal. A whiteness detecting step, a white area calculating step of calculating an area of a continuous white region displayed on the display unit from an output detected in the whiteness detecting step, and a continuous calculated in the white area calculating step And a color temperature correction method including a color temperature correction step of correcting the color temperature of the continuous white area based on the area of a typical white area.

  According to the present invention, the whiteness is detected from the RGB luminance signal, the area of the continuous white region displayed on the display unit is calculated from the output of the whiteness detection result, and the calculated continuous Since the color temperature of the continuous white area is corrected based on the area of the white area, when the white color temperature is corrected, an optimal correction according to the white area in the image is performed. be able to.

(First embodiment)
FIG. 1 is a block diagram for explaining a first embodiment of the present invention. In FIG. 1, 1 is a whiteness detection unit, 2 is a white area calculation unit, 3 is a color temperature correction value calculation unit, and 4 is a white color temperature correction unit.

  The whiteness detection unit 1 is a circuit similar to that shown in Patent Document 1, and obtains and outputs whiteness from an input RGB signal. The whiteness is calculated from the maximum value Max (R, G, B) and minimum value Min (R, G, B) of the input RGB signal to `` a * Min (R, G, B) -b * Max (R, G, B (A and b are coefficients satisfying a> 0, b> 0, and a> b. For example, a = 1.125 and b = 1 are preferable). This whiteness takes a larger positive value as the difference between the maximum and minimum R, G, B values of the target pixel is smaller, that is, closer to white, and is negative when the difference in R, G, B values is large and far from white. Take the value of Therefore, it is assumed that a pixel whose whiteness is a positive value is determined to be white, and the white area calculation unit 2 determines the white area in one screen from the number of pixels whose whiteness is positive in the whiteness detection unit 1. calculate.

  Specifically, the number of pixels determined to be white is integrated for one screen, and the result obtained by dividing by the total number of pixels on one screen is normalized to be the white area. Therefore, if the entire surface is white, the white area is “1”. In order to perform integration for one screen, the output of the white area calculation unit 2 is updated every one screen period. In the configuration of FIG. 1, the white area output to the color temperature correction value calculation unit 3 is the previous screen. The color temperature correction value calculation unit 3 calculates and outputs a color temperature correction value from the output from the whiteness detection unit 1 and the output from the white area calculation unit 2.

FIG. 2 shows a detailed configuration example of the color temperature correction value calculation unit 3.
The whiteness correction value calculation circuit 31 calculates a correction value by applying an appropriate gain to the whiteness signal. Also, the white area gain calculation circuit 32 has the characteristics shown in FIG. 3A, and becomes maximum when the white area is small, and the gain decreases as the white area increases. The multiplier 33 multiplies the outputs of the two circuits and outputs the result. Therefore, the output of the color temperature correction value calculation unit 3 is corrected to be smaller and output when the white area increases.

  The characteristic shown in FIG. 3A is an example, and it is sufficient that the gain is smaller when the white area is larger than when the white area is small. For example, with the characteristics shown in FIG. 3B, the change due to the expansion of the area is moderate at first, but the gain suddenly decreases when the area becomes larger than a certain area. Can do.

  The white color temperature correction unit 4 corrects the color temperature by changing the white color balance according to the output of the color temperature correction value calculation unit 3. For this reason, when the white area on the screen is small, the white color temperature is largely corrected. However, when the white area is large, the correction is small, so that the white color temperature is not excessively corrected. Can be.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
FIG. 4 shows a block diagram of the present embodiment. In the present embodiment, the RGB signal input to the whiteness detection unit 1 and the white color temperature correction unit 4 passes the color difference signal through the video delay unit 5 and the color conversion unit 6. Thereby, the output RGB signal is delayed by one screen or more with respect to the input color difference signal. Further, the white area calculation unit 2 of the first embodiment is changed to a low saturation area calculation unit 7, and an input of the low saturation area calculation unit 7 is a color difference signal before being converted into an RGB signal. The other whiteness detection unit 1, color temperature correction value calculation unit 3, and white color temperature correction unit 4 have the same configuration and operation as in FIG.

  The low saturation part area calculation unit 5 calculates the white area by counting the number of pixels with low saturation in the color difference signal. Specifically, a pixel in which the absolute values of RY and BY representing the color component of the color difference signal are both smaller than a predetermined value is determined to be white, and the number is counted. This is integrated for one screen and divided by the number of pixels on one screen to calculate the white area. Also in this case, if it is determined that the entire surface is white, the area of white is “1”.

  The method for correcting the white color temperature based on the white area is the same as in the first embodiment. However, since the RGB signal is delayed by one screen or more with respect to the color difference signal, the information on the screen currently being processed can be used as the area information, and correction without a sense of incongruity can be performed. .

  In many television circuits, an input color difference signal is subjected to processing using a frame memory such as pixel number conversion or interlace-progressive conversion, and then converted to an RGB signal. Therefore, the video delay unit 5 may also be used for processing using these frame memories.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
FIG. 5 shows a block diagram of the present embodiment. The difference between the present embodiment and the second embodiment is that the low saturation area calculation unit 7 is changed to an average video level calculation unit 8. Other than that, the configuration and operation are the same as those in FIG. 4, and the same reference numerals are given to the same circuits.

  The average video level calculation unit 8 calculates the average video level (APL) by integrating the Y signal for one screen and dividing by the total number of pixels for one screen. In the present embodiment, this APL is input as a white area to the color temperature correction value calculation unit 3 to control white color temperature correction.

  Since the APL increases when the white area is large, excessive color temperature correction for a large white area can be prevented by reducing the degree of color temperature correction when the APL is high.

  Since the average video level APL is obtained by integrating the analog video signal other than the configuration shown in FIG. 5, it can be obtained more easily than the saturation information of the second embodiment. However, when the APL is handled as an area, the APL becomes lower when the area of white with low luminance is large. Therefore, the effect of suppressing overcorrection with a large area is smaller than that of the second embodiment for white with low luminance. Become.

  FIG. 6 is a block diagram illustrating a configuration example of a television device according to the present invention. The receiving circuit 20 includes a tuner, a decoder, and the like, receives a television signal such as satellite broadcast or terrestrial wave, a data broadcast via a network, and outputs the decoded video data to the image processing unit.

  The image processing unit 21 includes the color temperature correction circuit described above, converts the video data into a display format of the display device, and outputs the image data to the display device. The display device includes a display panel, a drive circuit, and a control circuit. The control circuit 22 performs signal processing such as correction processing suitable for the display panel on the input image data, and outputs the image data and various control signals to the drive circuit 23. The drive circuit 23 outputs a drive signal to the display panel 24 based on the input image data, and a television image is displayed.

  The receiving circuit 20 and the image processing unit 21 may be housed in a separate housing from the display device 25 as a set-top box (STB), or in the same housing as the display device 25. May be.

(Other embodiments according to the present invention)
Each means constituting the color temperature correction circuit and each step of the color temperature correction method in the embodiment of the present invention described above can be realized by operating a program stored in a RAM or ROM of a computer. This program and a computer-readable recording medium recording the program are included in the present invention.

  Further, the present invention can be embodied as a system, apparatus, method, program, storage medium, or the like. Specifically, the present invention may be applied to a system composed of a plurality of devices, or may be applied to an apparatus composed of a single device.

Next, an example of the color temperature correction method will be described with reference to the flowchart of FIG.
First, in step S71, whiteness is obtained from the input RGB signal and output. As described above, the whiteness detection is performed by the whiteness detection unit 1. The whiteness takes a larger positive value as the color of the target pixel is closer to white, and is negative when far from white. Take the value.

  Next, proceeding to step S72, the white area in one screen is calculated. This calculation is performed by the white area calculation unit 2 and is performed based on the number of pixels (whiteness is positive) determined as white by the whiteness detection unit 1. Specifically, the number of pixels determined to be white is integrated for one screen, and the result obtained by dividing the total by the total number of pixels on one screen is the white area. Therefore, if all of one screen is white, the white area is “1”.

  In step S73, a color temperature correction value is calculated. In the present embodiment, the color temperature correction value is calculated by the color temperature correction value calculation unit 3 from the whiteness output from the whiteness detection unit 1 and the white area output from the white area calculation unit 2.

  Next, the process proceeds to step S74, and white color temperature correction is performed using the color temperature correction value calculated in step S73. In the present embodiment, the color temperature is corrected by changing the white color balance in accordance with the correction value acquired in step S73. For this reason, correction according to the area of white can be performed, and since the correction is weakened when the area is large, the color temperature can be prevented from being excessively corrected.

  In the present invention, a software program (in the embodiment, a program corresponding to the flowchart shown in FIG. 7) that realizes the functions of the above-described embodiments may be directly applied to the system or apparatus. Alternatively, it may be achieved by supplying from a remote location and the computer of the system or apparatus reads and executes the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, and the like.

  Examples of the recording medium for supplying the program include a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, and CD-RW. Moreover, a magnetic tape, a non-volatile memory card, ROM, DVD (DVD-ROM, DVD-R), etc. are also included.

  As another program supply method, the program can be supplied by connecting to a homepage on the Internet using a browser of a client computer and downloading the computer program of the present invention from the homepage. Alternatively, it can be supplied by downloading a compressed file including an automatic installation function to a recording medium such as a hard disk.

  It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. Let It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. In addition, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can also be realized by the processing.

  Further, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing based on the instructions of the program, and the functions of the above-described embodiments are realized by the processing.

1 is a block diagram illustrating a configuration example of a color temperature correction circuit according to a first embodiment of this invention. FIG. It is a block diagram which shows the 1st Embodiment of this invention and shows the detailed structural example of a correction value calculation part. It is a figure which shows the 1st Embodiment of this invention and shows the characteristic of a white area gain calculation circuit. It is a block diagram which shows the 2nd Embodiment of this invention and shows a structure. It is a block diagram which shows the structure of the 3rd Embodiment of this invention. It is a block diagram which shows the structural example of the television apparatus with which the color temperature correction circuit of this invention is applied. It is a flowchart explaining an example of a color temperature correction method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Whiteness detection part 2 White area calculation part 3 Color temperature correction value calculation part 4 White color temperature correction part 5 Image delay part 6 Color conversion part 7 Low chroma area calculation part 8 Average video level calculation part 31 Whiteness correction value calculation Circuit 32 White area gain calculation circuit 33 Multiplier

Claims (10)

A color temperature correction circuit used in a display device for inputting a RGB luminance signal and displaying a color image on a display unit,
A whiteness detection unit for detecting whiteness from the RGB luminance signal;
A white area calculation unit for calculating an area of a continuous white region displayed on the display unit from an output of the whiteness detection unit;
A color temperature correction circuit comprising: a color temperature correction unit that corrects the color temperature of the continuous white area based on the area of the continuous white area calculated by the white area calculation unit.   2. The white area calculation unit according to claim 1, wherein the white area calculation unit adds the number of pixels determined to be white for one screen and divides the total by the total number of pixels of one screen to obtain a white area. The described color temperature correction circuit.   The white area calculation unit determines that a pixel whose absolute value of the color signal of the color difference signal before conversion into the RGB video signal is smaller than a predetermined value is white, and the pixel determined to be white is one screen 2. The color temperature correction circuit according to claim 1, wherein the white area is calculated by dividing and dividing by a total number of pixels of one screen.   The color temperature correction circuit according to claim 1, wherein the white area calculation unit calculates a white area from an average luminance level of an image obtained from a color difference signal before being converted into the RGB video signal.   A television apparatus comprising the color temperature correction circuit according to claim 1. A color temperature correction method used in a display device that inputs RGB luminance signals and displays a color image on a display unit,
A whiteness detection step of detecting whiteness from the RGB luminance signal;
A white area calculating step of calculating an area of a continuous white region displayed on the display unit from an output detected in the whiteness detecting step;
A color temperature correction method comprising: a color temperature correction step of correcting the color temperature of the continuous white region based on the area of the continuous white region calculated in the white area calculation step.   7. The white area calculating step, wherein the number of pixels determined to be white is integrated for one screen, and the result obtained by dividing the total by the total number of pixels on one screen is used as a white area. The color temperature correction method described in 1.   In the white area calculating step, a pixel whose absolute value of the color signal of the color difference signal before conversion into the RGB video signal is smaller than a predetermined value is determined to be white, and a pixel determined to be white is 1 The color temperature correction method according to claim 6, wherein the white area is calculated by integrating the screen and dividing the total by the total number of pixels of one screen.   7. The color temperature correction method according to claim 6, wherein, in the white area calculating step, a white area is calculated from an average luminance level of an image obtained from a color difference signal before being converted into the RGB video signal. A program that causes a computer to execute a color temperature correction method used in a display device that inputs RGB luminance signals and displays a color image on a display unit,
A whiteness detection step of detecting whiteness from the RGB luminance signal;
A white area calculating step of calculating an area of a continuous white region displayed on the display unit from an output detected in the whiteness detecting step;
Causing the computer to execute a color temperature correction method including a color temperature correction step of correcting the color temperature of the continuous white region based on the area of the continuous white region calculated in the white area calculation step. A featured program.

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