JPH06311391A - Luminance correction method - Google Patents

Abstract

PURPOSE:To form an excellent display pattern on visual sense by reading intermediate correction data from a correction storage section at first, correcting the luminance based on the data, reading final correction data after lapse of a predetermined time succeedingly and correcting the luminance based on the data. CONSTITUTION:A video signal 15 is converted into digital data by an A/D converter section 1 and branched, one data are fed to a gradation detection section 2 and the other are fed to a luminance correction section 7 and a picture element by one frame, e.g. is stored in a frame memory of the inside. Then a detection section 2 detects luminance gradation from data of each picture element and it is inputted to a counter corresponding to luminance gradation provided to each class of the counter section 3 via a control section 10. When the total sum of the contents of the counter section 3 reaches a predetermined number, the count is stopped and frequency data from the counter section 3 are fed to a section 5 via a control section 10 and compared with luminance gradation frequency distribution pattern data from the memory 4 and a discriminated pattern is subject to luminance correction with an output of a correction value storage section 6 at a luminance correction section 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brightness correction method for correcting brightness according to a brightness gradation distribution pattern of a video signal.

[0002]

2. Description of the Related Art A video signal input to a display device such as an LCD, PDP or CRT has a small number of pixels in a low brightness class and a high brightness class as shown in FIG. If the number of
The displayed image has a little highlight brightness and black level brightness, and most of them are in an image state where there is no sharpness due to intermediate brightness. An image with a lack of contrast like this,
The brightness needs to be corrected to correct. Conventionally, a method of correcting the brightness according to the distribution pattern of the brightness gradation of the video signal has been implemented. However, since the correction method executes the final correction once, the display image immediately after the correction is executed, For example, when the contrast changes suddenly,
There was a problem that something was wrong.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a brightness correction method that smoothly and smoothly executes brightness correction.

[0004]

In order to achieve the above object, an AD converter for converting a video signal into digital data, and a gradation detector for detecting the brightness gradation of the digital data output by the AD converter. And a counting unit that counts the digital data output by the gradation detection unit for each predetermined gradation class,
Either the memory that stores the brightness gradation distribution pattern based on the gradation class-specific data counted by the counting unit and the model distribution pattern that is preset, or the model distribution pattern that the brightness gradation distribution pattern stores in advance A determination unit that determines whether or not they correspond, a correction value storage unit that stores correction data that corrects the brightness gradation for each brightness gradation distribution pattern, and the AD conversion unit based on the data read from the correction value storage unit. A brightness correction unit that corrects the brightness gradation of the output digital data, a DA conversion unit that converts the corrected digital data into a video signal, the gradation detection unit, the counting unit,
A memory, a determination unit, a correction value storage unit, and a control unit that controls each unit of the brightness correction unit.

[0005]

With the above configuration, when performing the brightness correction, the intermediate correction data is first read from the correction value storage unit, and the brightness correction unit performs the brightness correction based on the intermediate correction data. The timer measures a predetermined time, for example, a time corresponding to several fields. Then, after a lapse of a predetermined time, the final correction data is read out, and the brightness correction unit finally performs the brightness correction based on the final correction data. That is, the brightness correction is performed in two steps.

[0006]

EXAMPLE A brightness correction method according to the present invention will be described below.
This will be described in detail with reference to the drawings. FIG. 1 is a circuit block diagram of an embodiment of a brightness correction method according to the present invention. Reference numeral 1 denotes an AD converter that converts the video signal 15 into digital data. Two
Is a gradation detection unit that detects the brightness gradation of the digital data output by the AD conversion unit 1. A counting unit 3 counts the digital data output by the gradation detecting unit 2 for each predetermined luminance gradation class. Reference numeral 4 denotes a memory that stores a brightness gradation distribution pattern based on frequency data for each brightness gradation class counted by the counting unit and also stores a preset model distribution pattern. Reference numeral 5 denotes a determination unit that determines which one of the model distribution patterns stored in advance the brightness gradation distribution pattern corresponds to. Reference numeral 6 denotes a correction value storage unit that stores intermediate correction data and final correction data as correction data for correcting the brightness gradation for each brightness gradation distribution pattern. A brightness correction unit 7 corrects the brightness gradation of the digital data output by the AD conversion unit 1 based on the data read from the correction value storage unit 6. Reference numeral 8 is a timer for counting a predetermined time. Reference numeral 9 denotes a DA converter that converts the corrected digital data into the video signal 16. 10
Is the gradation detection unit 2, the counting unit 3, the memory 4, the determination unit 5, the correction value storage unit 6, the brightness correction unit 7, and the timer 8.
Is a control unit that controls each unit of.

The operation of the brightness correction method according to the present invention will be described. The AD conversion unit 1 converts the video signal 15 into digital data, branches the digital data, supplies one to the gradation detection unit 2, and supplies the other to the brightness correction unit 7.
In the frame memory inside the brightness correction unit 7, for example, 1
The pixels for the frame are stored. The gradation detecting unit 2 detects the brightness gradation from the data of each pixel, and inputs it via the control unit 10 to the counter corresponding to the brightness gradation provided for each class of the counting unit 3. . In the counting unit 3, for example,
When the total number of luminance gradations is 256 and the classes are evenly divided into 4 classes, 0 to 63, 64 to 127, 128 to 191,
There are 192-255 classes, a counter is provided for each class, and the frequency of input data is totaled. When the total of the frequencies of the counting unit 3 reaches a predetermined number, for example, the total number of pixels in one frame, the counting is stopped, and the frequency data of each class from the counting unit 3 passes through the control unit 10 to make a determination. The luminance gradation frequency distribution pattern data supplied to the unit 5 and read from the memory 4 via the control unit 10 is compared,
It is determined which pattern has the luminance gradation distribution of the input video signal. The memory 4 has, for example, L for class A, H for class B, and H for class C depending on whether the frequencies of the classes A to D shown in FIG. 2 are higher (H) or lower (L) than the reference value. , A class D is L, and a necessary pattern is stored as a determination model pattern from 16 possible combination patterns.

FIG. 4 is a graph of input luminance (grayscale) versus output luminance (grayscale) characteristics with intermediate correction values of the luminance correction method according to the present invention. For example, when it is determined that the luminance gradation distribution of the input video signal has the pattern shown in FIG.
The intermediate correction data set for each luminance gradation distribution pattern shown by the polygonal line 41 in FIG. 4 is read from the correction value storage unit 6, and the data is supplied to the luminance correction unit 7, and the frame memory of the luminance correction unit 7 is read. The brightness gradation of the video signal stored in is corrected. The timer 8 measures a predetermined time, for example, 5 frame time, and informs the control unit 10, and subsequently,
The final correction data indicated by the polygonal line 40 is read out and finally the brightness is corrected. The chain line 42 represents a straight line having the same input and output. FIG. 3 is a diagram showing a process of correcting the brightness gradation distribution pattern by the brightness correction method according to the present invention. 31
The chain line indicates the luminance gradation frequency of the input video signal shown in FIG. The thin solid line 32 is the luminance gradation frequency that is the luminance gradation correction based on the intermediate correction data (the polygonal line 41 in FIG. 4). The thick solid line of 30 is the final correction data (the polygonal line 4 in FIG. 4).
It is the luminance gradation frequency that is the luminance gradation correction based on 0).
As the luminance gradation distribution pattern of the model used for discrimination, necessary patterns other than the pattern shown in FIG. 2 are stored, and correction values corresponding to the luminance gradation distribution pattern are stored in association with each other. Keep it. Further, the classification of the brightness gradation does not have to be limited to the above four classes, and may be increased or decreased. Further, the brightness correction is not limited to the correction of the contrast, and for example, the brightness of the intermediate class may be lowered and the classes of the dark class and the highlight class may be increased. It may be adapted.

[0009]

As described above, the present invention provides a brightness correction method for smoothly and smoothly correcting brightness. Therefore, the brightness of the display screen can be corrected step by step by using it for the correction of the contrast, which is advantageous in that a visually good display screen can be provided.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment of a brightness correction method according to the present invention.

FIG. 2 is a diagram showing a luminance gradation distribution pattern of a video signal.

FIG. 3 is a diagram showing a process of correcting a luminance gradation distribution pattern by a luminance correction method according to the present invention.

FIG. 4 is a graph of input luminance (grayscale) versus output luminance (grayscale) characteristics with intermediate correction values of the luminance correction method according to the present invention.

[Explanation of symbols]

 1 AD conversion unit 2 Gradation detection unit 3 Counting unit 4 Memory 5 Judgment unit 6 Correction value storage unit 7 Brightness correction unit 8 Timer 9 DA conversion unit 10 Control unit 15 Input video signal 16 Corrected video signal 30 Based on final correction data Corrected luminance gradation degree 31 Luminance gradation degree of input video signal 32 Luminance gradation degree corrected based on intermediate correction data 40 Final correction data 41 Intermediate correction data 42 Straight line with equal input and output

Claims (2)

[Claims] 1. A for converting a video signal into digital data
A D conversion section, a gradation detection section for detecting the brightness gradation of the digital data output by the AD conversion section, a counting section for counting the digital data output by the gradation detection section for each predetermined gradation class, Which corresponds to either a memory that stores a brightness gradation distribution pattern based on the gradation class-specific data counted by the unit and a preset model distribution pattern, or a model distribution pattern that the brightness gradation distribution pattern stores in advance. Output from the AD conversion unit based on the data read from the correction value storage unit, a determination unit that determines whether to perform the correction, a correction value storage unit that stores correction data that corrects the brightness gradation for each luminance gradation distribution pattern, A brightness correction unit for correcting the brightness gradation of the digital data, a DA conversion unit for converting the corrected digital data into a video signal, the gradation detection unit,
In a brightness correction method including a counting unit, a memory, a determination unit, a correction value storage unit, and a control unit that controls each unit of the brightness correction unit, the brightness correction method includes a timer that counts a predetermined time and a brightness in the correction value storage unit. Intermediate correction data and final correction data are stored as correction data for correcting the gradation, and the brightness correction of the input video signal is temporarily corrected once for each brightness gradation distribution pattern, and then the final correction is performed. A brightness correction method characterized by the above. 2. The brightness correction method according to claim 1, further comprising a plurality of sets of the intermediate correction data.