KR20050089517A - Apparatus for gray scale conversion of video signal and converting method thereof - Google Patents

Abstract

The present invention provides a method for converting grayscale data of a video signal and a grayscale data converting apparatus capable of solving both a problem of pseudo contour due to a parallax method and a problem of increasing frequency due to a sequential method. A method of generating RGB grayscale data by converting RGB (Red, Green, Blue) image data, which is a signal, by n-bit (n is a natural number) grayscale conversion having a PWM (Pulse Width Modulation) format, the grayscale by the parallax method during the grayscale conversion. Determining a lower number of steps x (x is a natural number less than n) to be; Determining a total number of steps to be used in gradation conversion by x and n, wherein the total number of steps is x + 2 ^nx (lower x steps and upper 2 ^nx steps); Reading the image data; Determining whether the image data corresponds to the lower x steps; Gray-level converting the image data by a parallax method as the image data corresponds to lower x steps; Gradually converting the image data in a sequential manner as the image data corresponds to upper 2 ^nx steps; And selectively outputting the gray-converted signal by the parallax method and the gray-converted signal by the sequential method.

In addition, the present invention provides an gradation signal conversion device for a video signal.

Description

Gradation converter and video conversion method of video signal {APPARATUS FOR GRAY SCALE CONVERSION OF VIDEO SIGNAL AND CONVERTING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a gray scale conversion method of video data, and more particularly, to a gray scale data conversion and control method of a video signal, and a gray data conversion apparatus.

In order to display the image data on a display device such as a plasma display panel (PDP), liquid crystal display (LCD), or an electronic board, image data is taken. Since the captured image data is an optical signal, a photoelectric conversion device such as a photodiode is used again. It is converted into an electrical signal and processed again through a plurality of processing steps.

In general, in addition to the RGB format used for color television, the digital color image may be represented by a YUV format, a YIQ format, or a YCrCb format used in a broadcast system, and a CMYK format used in a color printer.

The RGB format expresses colors as data signals of R (Red), G (Green), and B (Blue), which implement colors, but the YUV format uses the Y signal, which is the brightness component, and the two U and V signals, which are the color components. To transmit color data.

On the other hand, the YUV signal is a signal system mainly used in the PAL method, and the PAL method is a standard method of broadcasting signals used in other European countries except France and some eastern European countries. It is a method of inverting and modulating each scan line, which is incompatible with black-and-white television, but has a feature of less influence of a video signal on phase distortion caused by recording or transmission paths.

In order to express the above-described YUV signal, for example, on a television screen, it is necessary to convert it to an RGB signal. The standardization standard for this conversion is shown in ISO / IEC 13818-2.

R = (70639 (Y-16) + 117504 (V-128) + 32768) / 2 ¹⁶

G = (70639 (Y-16)-13954 (U-128)-34903 (V-128) + 32768) / 2 ¹⁶

B = (70639 (Y-16) + 138453 (U-128) + 32768) / 2 ¹⁶

That is, each signal of RGB is calculated through a calculation process such as multiplying or dividing each signal of YUV by a predetermined value.

 In a method of expressing image data on a display device including an electronic display board, the transmitting side transmits the image data in a luminance + color difference format such as YUV or YCrCb, and the receiving side, that is, the standardization standard such as Equation 1 described above on the display device. Logic operation that satisfies, i.e., color space change, gamma correction, etc. must be converted to RBG for display, or image data can be converted to RGB in advance, and each has advantages and disadvantages.

For example, when the transmission side converts and transmits an image signal in RGB format in advance, each image signal of RGB given as a digital value is converted into a signal having PWM (Pulse Width Modulation) format to display the transmitted RGB format image signal. Will be converted.

The RGB signal converted into the PWM signal is hereinafter referred to as gradation data, and the gradation data is separated and used for each RGB color.

There are largely a parallax (or weight) method and a sequential method for generating such grayscale data.

1 is a diagram illustrating a relationship between a frame and a gray scale.

Referring to FIG. 1, a unit constituting an image signal is a frame in a process of scanning or reconstructing an image signal as if the pixels are assembled, and each frame 1F is a vertical synchronization signal V. -Sync). For example, in a horizontal scanning method in which the scanning line frequency is 60 Hz, 60 frames are scanned on the screen per second, and thus, one frame 1F is displayed for 1/60 seconds.

If image data is displayed, for example, in 10-bit grayscale, there are 2 ¹⁰ grayscales, and one frame 1F having a time of 1/60 second is further divided into 1024 grayscales.

Therefore, RGB image data given numerically should be converted to fit the n-bit gray level 2 ⁿ and output as gray data.

2 is a diagram for explaining a principle of generating grayscale data in a sequential manner.

Referring to FIG. 2A, in the case of the sequential method for 10-bit gradation conversion, when image data corresponding to one frame is inputted, steps indicating the lighting time of 1 to 1024 steps are sequentially increased and decreased. Gray data having a width corresponding to the video data is output.

Referring to FIG. 2B, it can be seen that grayscale data is output as a PWM signal corresponding to brightness of each frame, that is, brightness.

Here, it can be seen that when a gray level satisfies 1024 steps in one frame, the gray level is 100% in the frame, and when the gray level satisfies 512 steps, the gray level is 50%.

On the other hand, it is necessary to adjust not only the brightness of each RGB color corresponding to each unit pixel represented by the lighting time, but also the luminance component that is the brightness of each of the R, G, and B colors, and to adjust each step of 1024 gray levels. If the luminance is to be adjusted in bit units, for example, M bits, to be divided into 2 ^M unit luminance intervals. Therefore, in the case of the sequential method, as the unit to control the gradation and brightness increases, the frequency of the necessary system clock increases exponentially, which causes the electromagnetic interference and the frequency response characteristic of the device to deteriorate.

3 is a diagram for explaining a principle of generating grayscale data in a parallax manner.

Unlike the sequential method, in the case of the parallax method, unlike the sequential method, when the RGB image data given by the weight is input and the numerical value is input, the sum of each step given by the weight is expressed in the PWM format so that the corresponding image data becomes. will be.

For example, in the case of an R signal having a gradient value of 527, since the sum of 1 (2 ⁰ ), 8 (2 ³ ), and 512 (2 ⁹ ), the R signal having a gradient value of 527 has a gray level as shown in FIG. Is converted to data.

Referring to FIG. 3B, it can be seen that grayscale data is output as a PWM signal corresponding to the brightness of each frame, that is, the brightness.

The parallax method is advantageous in terms of frequency since the number of steps per frame can be reduced compared to the sequential method.

However, in the case of parallax, there is a significant disadvantage of pseudo contour generation.

4 is a diagram for explaining a principle of generating a pseudo contour in a parallax system.

Referring to FIG. 4, when the R signal having the lighting time of 513 and the R signal having the lighting time of 143 are respectively converted into grayscale data for successive times t _a and t _b , the weight corresponding to t _a is 512 (2 ^9). ) And the weight 15 (2 ⁰ +2 ¹ +2 ² +2 ³ ) part corresponding to t _b are regarded as one frame (512 + 15 = 527), so that the displayed image is different from the actual image. Problems arise, usually called pseudo contours.

Such pseudo contours do not cause serious problems in the case of still images, but mainly occur in the case of moving images.

On the other hand, in order to solve the pseudo contour problem, the arrangement of each frame is zigzag, that is, the steps are arranged in the order of 1 → 1024 in one frame, and the steps are arranged in the order of 1024 → 1, which is the opposite in 2 frames. You can also use it, but it's not a fundamental solution.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems, and provides a gray scale data converting method and a gray scale data converting apparatus capable of solving both a problem of pseudo contour due to a parallax method and a problem of increasing frequency due to a sequential method. Its purpose is to provide.

In order to achieve the above object, the present invention provides a method of generating RGB grayscale data by converting RGB (Red, Green, Blue) image data, which is a digital signal, with n-bit (n is a natural number) grayscale conversion having a PWM (Pulse Width Modulation) format. Determining a lower number of steps x (x is a natural number less than n) to be grayed out by the parallax method in the gray level conversion; Determining a total number of steps to be used in gradation conversion by x and n, wherein the total number of steps is x + 2 ^nx (lower x steps and upper 2 ^nx steps); Reading the image data; Determining whether the image data corresponds to the lower x steps; Gray-level converting the image data by a parallax method as the image data corresponds to lower x steps; Gradually converting the image data in a sequential manner as the image data corresponds to upper 2 ^nx steps; And selectively outputting the gray-converted signal by the parallax method and the gray-converted signal by the sequential method.

In order to achieve the above object, the present invention provides an apparatus for generating RGB grayscale data by converting RGB image data, which is a digital signal, with n-bit grayscale conversion having a PWM format, comprising: a memory unit for storing the image data; The number of lower steps x to be gradated by the parallax method during the gradation conversion by reading the image data from the memory unit, and the total number of steps to be used during gradation conversion by x and n x + 2 ^nx (lower x steps and upper 2 ^nx A discrimination unit for determining whether the video data corresponds to the lower x steps or the upper 2 ^nx steps through information; A parallax gradation unit for gradually converting the image data by a parallax method as the image data corresponds to lower x steps; A sequential gradation unit for gradually converting the image data by the sequential method as the image data corresponds to the upper 2 ^nx steps; And a selector for selectively outputting the gray-converted signal by the parallax method and the gray-converted signal by the sequential method.

The present invention converts RGB grayscale data by mixing a parallax method and a sequential method. At this time, the least significant step of the parallax method is used repeatedly, and the enable signal of each RGB module is added to this part. For example, the enable signal is valid only for 1/8, 1/4, 1/2 in the reverse order of d0, d1, and d2 for the lowest three steps when displaying gray scale with 10 bits. (Active).

For this purpose, if the reference clock is used in the upper step during the luminance control, the clock signal obtained by dividing the reference clock into 1/8, 1/4, and 1/2 at d0, d1, and d2 in the lowest three steps, respectively, is used. use.

In addition, since the upper step is applied to the sequential method, since the upper part is 7 bits, when 2 ⁷ (128) steps are applied, the total number of steps becomes 131, so the number of steps can be reduced, thereby solving the problem of frequency increase.

In addition, by applying a parallax method using an enable signal in the lower bits and applying a sequential method in the upper bits, the distribution of data in the output waveform of the gray scale data is shaped into a dense portion, thereby suppressing generation of pseudo contours.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. .

12 is a flowchart illustrating a gradation conversion method of image data according to the present invention.

12 is an n-bit (n is a natural number) gray level conversion process of converting RGB image data, which is a digital signal, into RGB gray level data having a PWM format, in a step of 'x (x is a natural number smaller than n) + 2 ^nx '. The gray scale conversion process is shown.

Referring to FIG. 12, a gray level conversion process of image data first determines x, which is a lower step number to be grayed out by a parallax method during gray level conversion, and then determines a total number of steps to be used in gray level conversion by x and n.

In this case, the number of steps corresponding to the lower bits to which the parallax method is to be applied is 'x', and since the number of upper steps to which the sequential method is to be applied is '2 ^nx ', the total number of steps becomes 'x + 2 ^nx '. In addition, it is also determined how to implement the luminance for each RGB color for each step.

The image data given as the numerical digital value for each RGB color gradient is written to the memory (S120), and then the RGB image data stored in the memory is read (S121) for the gray level conversion. A read operation is called a refresh. In general, a memory is composed of two banks, and when a write operation is performed in one bank, a read operation is performed in another bank.

Normally, the write operation is done once per 1/60 second, and the refresh is performed 2 ⁿ times per 1/60 second (per one light). For example, in the case of 10-bit gradation, 2 ¹⁰ (1024) refreshes are performed.

Subsequently, it is determined whether the read image data corresponds to the lower x steps (S122). As a result of the determination, when the image data corresponds to the lower x steps, the image data is grayscale converted by the parallax method (S123). When the image data corresponds to the upper 2 ^nx steps, the image data is grayscale converted by the sequential method (S124). .

Subsequently, the image data gradated by the parallax method and the image data gradated by the sequential method are synthesized, and the data gradated to n bits, that is, the gradation data are output.

Here, when the gray level conversion is performed by the parallax method, the effective data section of one step from the lowest is in the order of 1/2 ^x , 1/2 ^x-1 , ...., 1/2 ² , 1/2 ¹ . do. For example, if the parallax method is applied only to the lower 3 bits during the 10-bit gradation conversion, the three steps from the lowest are valid only in the sections of 1/2 ³ , 1/2 ² , and 1/2, respectively (active). Therefore, the upper 7 bits are 2 ^nx , n is 10 and x is 7, so only 128 steps of 2 ⁷ need to be applied. Therefore, the total number of steps is 131 steps plus the lower 3 + upper 128.

In the step S125 of synthesizing, the image data that has been grayscale-converted by different methods are selectively output, and are controlled by k grayscale switching signals satisfying ^2k = x + 1 (k is a natural number).

That is, in the above example, since 'x = 3', 'k = 2', and the gray level switching signal is two. Therefore, it is possible to switch four states including the lower 1/8, 1/4, 1/2 and the upper one by the logical combination of the two gray level switching signals.

On the other hand, the steps are divided by a plurality of step pulses, respectively.

FIG. 13 is a flowchart illustrating a brightness control method of the present invention, and a brightness control process will be described with reference to the flowchart.

When performing gradation conversion by using a parallax method and a sequential method, the brightness is adjusted for each RGB color by M bits (M is a natural number), that is, 2 ^M unit brightness adjustment steps. This is to adjust the brightness of each displayed RGB collectively, not to adjust the brightness of the image data according to each step.

Thus, in adjusting the luminance, in the upper 2 ^nx steps of gradation conversion by the sequential method, the luminance is adjusted in 2 ^M unit brightness adjustment steps by using the reference clock, which is a periodic square wave signal, and the lower gradation conversion by the parallax method. In the x steps, x division clocks having a cycle of (1/2 ¹ , 1/2 ² , ...., 1/2 ^x-1 , 1/2 ^x ) divided by the reference clock are used (S130). ). At this time, the step of valid data interval ^x 1/2, 1/2 ^x-1, ...., ² 1/2, 2 ^M to sequentially correspond to the frequency division clock and the station to be used by ¹ 1/2 Brightness is adjusted by two unit brightness adjustment steps.

After determining whether to use the divided clock or the reference clock to adjust the luminance (S131), select a clock signal according to the sequential method or parallax method according to the determination result, and correspond to the lower x steps using the selected clock signal. In the parallax gray level, the luminance is adjusted by using the divided clock, and in the sequential gray level corresponding to the upper 2 ^nx steps, the luminance is adjusted by using the reference clock.

At this time, in varying the brightness control according to the sequential method and the parallax method, a clock to be used for the brightness control in the corresponding step in the reference clock or the divided clocks is selected using k gray level switching signals.

That is, in the above example, since 'x = 3', 'k = 2', and the gray level switching signal is two. Therefore, the reference clock, 1/2 frequency division clock, and 1/4 frequency division corresponding to four states including the lower 1/8, 1/4, 1/2, and the upper one, respectively, by the logical combination of the two gray level switching signals. It will switch to use clock, 1/8 frequency clock.

In adjusting the luminance, a clock (reference clock, 1/2 frequency division clock, 1/4 frequency division clock, 1/8 frequency division clock) to be used for luminance adjustment and luminance control signal corresponding to each preset or programmed RGB color are used. Adjust brightness by comparison. The luminance control signal is provided by a microprocessor or the like.

Hereinafter, a gradation conversion apparatus capable of performing the above-described gradation process will be described with reference to an embodiment.

FIG. 6 is a block diagram illustrating a gradation generating device for generating gradation data by performing gradation conversion of image data.

Referring to FIG. 6, the gray scale generator includes a memory block 60 and a memory control and gray data generating logic 61.

The gradation generating device receives the RGB image data separated by the data separating unit, the dot clock, the vertical / horizontal synchronization signal, and the display control signal to generate the gradation data necessary for displaying an image to a module such as an LED.

The RGB image data is written (stored) in the memory block 60 according to the dot clock, the vertical / horizontal sync signal, and the display control signal, and the image data stored in the memory block 60 is grayed out so that the control logic may be controlled according to an algorithm. It is generated as data that can gradate the image in the module. In the case of 10-bit gradation conversion, it is 10 bits in each color RGB, so when this is expressed as a gradation step, 2 ¹⁰ = 1024 steps.

FIG. 7 is a block diagram illustrating the gray scale generating apparatus of FIG. 6 separated into RGB colors, and divided into three colors.

Referring to FIG. 7, the grayscale generator includes an address and grayscale switching signal generator 611 and respective RGB grayscale generators 610a, 610b, and 610c.

Serially transmitted RGB image data (SDI; Serial Data Input) is input, which is in turn converted to parallel data through the serial-parallel conversion unit 71 to form each RGB gray level generator in the form of digital values R, G, and B. 610a, 610b, and 610c. Each of the RGB grayscale generators 610a, 610b, and 610c includes a refresh address Ref, a gradient address Grad, a counter clock CCLK, and a grayscale switching signal s1, provided from the address and grayscale switching signal generator 611. Controlled by s2) outputs the gray scale data R ', G', and B '.

On the other hand, as in the above example, if the parallax method is applied only to the lower 3 bits during the 10-bit grayscale conversion, the three steps from the lowest are only applied to the sections of 1/2 ³ , 1/2 ² , and 1/2 respectively. The data is valid (active), which means that the upper 7 bits are 2 ^nx to n is 10 and x is 7, so you only need to apply 128 steps, which are 2 ⁷ . Therefore, the total number of steps becomes 131 steps by adding the lower 3 + upper 128 and k gray level switching signals satisfying 2 ^k = x + 1 (k is a natural number) are 'x = 3', so 'k = 2' Since the gradation switching signal is two of s1 and s2, the four combinations including the lower 1/8, 1/4, 1/2 and the upper one are determined by the logical combination of the two gradation switching signals s1 and s2. The state can be switched.

The oscillator 72 (OSC) oscillates and provides the fundamental frequency required by the address and grayscale switching signal generator 611.

8 is a detailed block diagram illustrating an example of each gray scale generator of FIG. 7.

The gray scale generator shown in FIG. 8 is an apparatus for generating RGB gray scale data by converting RGB image data, which is a digital signal, by n-bit gray scale conversion having a PWM format.

Referring to FIG. 8, the RGB gray scale data generating apparatus according to an exemplary embodiment of the present invention includes a memory unit 80 for storing input image data, and a parallax scheme when gray scale conversion by reading image data from the memory unit 80. The image data is converted into the lower x steps through the number of lower steps x to be grayed by and the total number of steps x + 2 ^nx (lower x steps and upper 2 ^nx steps) to be used for gray level conversion by x and n. Or a judging unit 81 for judging whether or not the image corresponds to the upper 2 ^nx steps, and a parallax gradation unit for gradation conversion of the image data by the parallax method as the determination result image data corresponds to the lower x steps ( 82), and determined that the image data is changed by using the gray level and the gray-scale sequential portion 83 for converting gradation of image data according to corresponding to the top of step 2 ^nx in the sequential method, a differential method and the sequential method And a signal for each step M-bit brightness control section 84 for controlling the luminance for each of RGB colors to (M is a natural number) in other words, 2 ^M of unit brightness adjustment step, a by a differential manner gradation conversion signal and And a selector 85 for selectively outputting the gray-converted signal by the sequential method.

Here, the parallax gradation unit 82 is such that the effective data section of the one step from the lowest is in the order of 1/2 ^x , 1/2 ^x-1 ,..., 1/2 ² , 1/2 ¹ . The gradation conversion is performed, and the selection unit 85 is controlled by k gradation switching signals satisfying 2 ^k = x + 1.

The brightness control unit 84 adjusts the luminance of the reference clock to 2 ^M unit luminance adjustment steps in the upper 2 ^nx steps of gray conversion by the sequential method, and the reference clocks in the lower x steps of gray conversion by the parallax method. X divided clocks having a cycle of (1/2 ¹ , 1/2 ² , ...., 1/2 ^x-1 , 1/2 ^x ) divided by 1 are used.

In other words, 2 ^M unit luminances are applied so that the effective data section of one step sequentially reverses each other 1/2 ^x , 1/2 ^x-1 , ...., 1/2 ² , 1/2 ^1. The adjustment step adjusts the brightness, and the step is divided by a plurality of step pulses, respectively.

FIG. 10 is a detailed block diagram illustrating the luminance control unit of FIG. 8.

Referring to FIG. 10, the luminance controller 84 divides the reference clock SCLK to generate x division clocks, and k to change luminance according to sequential and parallax schemes. A selector 102 for selecting a clock to be used for luminance adjustment in a corresponding step from the reference clock SCLK or the divided clocks under the control of the gray scale switching signals s1 and s2, and a clock selected by the step pulse sp A plurality of comparators (104a, 104b, 104c) for comparing the M-bit counter (100) for counting the < RTI ID = 0.0 > and < / RTI > the output of the counter (100) with the luminance control signal corresponding to each of the predetermined or programmed RGB colors; Each of the plurality of comparators corresponds to one-to-one, and the plurality of luminance signals MROE, which are enabled when the step pulse sp is applied and are disabled when the outputs of the corresponding comparators 104a, 104b, and 104c are enabled, respectively MGOE, MBOE) Further included is a flip-flop (103a, 103b, 103c) to.

Here, as an example of the flip-flops 103a, 103b, and 103c, the output of the comparators 103a, 103b, and 103c is a reset (R) input, and the step pulse (sp) is a set (S) input. Although flip-flops are taken as an example, various flip-flops such as D-flip-flops may be used.

FIG. 5 is a timing diagram showing a signal waveform when gray scale conversion is performed in x + 2 ^nx steps according to the present invention, and FIG. 9 is a signal waveform of an example in which gray scale conversion is performed in 3 + 2 ⁷ (131) steps. FIG. 11 is a timing diagram showing a waveform in which luminance is controlled according to an embodiment of the present invention.

Hereinafter, operations of the gradation conversion neglecting and luminance control unit having the configurations of FIGS. 8 and 10 will be described with reference to FIGS. 5, 9, and 11.

After the image data R, G, and B given as digital values are written to the memory unit 80, the RGB image data stored in the memory for gradation conversion is read or refreshed in response to the refresh address signal Ref. do.

Subsequently, the determination unit 81 determines whether the read image data corresponds to the lower x steps. If the determination result image data corresponds to the lower x steps, the parallax gradation unit 82 determines the gradient signal Grad. In response to this, the video data is grayscale-converted by a parallax method. If the judgment result image data corresponds to the top 2 ^nx steps, the sequential gradation unit 83 performs gradation conversion of the image data by the sequential method.

The operation of the brightness control unit 84 will be described later with reference to FIG. 10.

The selecting unit 85 synthesizes the image data gradated by the parallax method and the image data gradated by the sequential method, that is, the gradation data is converted into n bits by selectively outputting, ie, the grayscale data R 'and G'. , B ').

Referring to FIG. 5, in the present invention, one frame divided by the vertical synchronization signal V-Sync is mixed with a parallax method and a sequential method to generate RGB grayscale data.

Since the number of steps corresponding to the lower bits to which the parallax method is to be applied is 'x' and the number of upper steps to which the sequential method is to be applied is '2 ^nx ', the total number of steps becomes 'x + 2 ^nx '. Here n represents n-bit gradation conversion.

At this time, the least significant step of the parallax method is repeatedly used for the lower bits, and a module enable signal (MOE) for each of RGB is added to this part.

The module enable signal MOE indicates that the lighting section of the corresponding gradation is valid (active). In the lower steps to which the parallax is applied, 1/2 ^x , 1/2 ^x-1 , ..., 1 Has only a valid interval of / 2.

FIG. 9 illustrates an example in which the lower three bits are applied to the parallax method during the 10-bit grayscale conversion. When the grayscale conversion is performed by the parallax method, the effective data section of one step from the lowest is 1/2 ^x , 1/2 ^x-1 , ...., 1/2 ² , 1/2 ¹ For example, if the parallax method is applied only to the lower 3 bits during the 10-bit gradation conversion, the three steps from the lowest are valid only in the sections of 1/2 ³ , 1/2 ² , and 1/2, respectively (active). Therefore, the upper 7 bits are 2 ^nx , n is 10 and x is 7, so only 128 steps of 2 ⁷ need to be applied. Therefore, the total number of steps is 131 steps plus the lower 3 + upper 128.

Therefore, since the total number of steps becomes 131 (3 + 128), the number of steps can be reduced and the problem of frequency increase can be solved.

In addition, by applying a parallax method using an enable signal in the lower bits and applying a sequential method in the upper bits, the distribution of data in the output waveform of the gray scale data is shaped into a dense portion, thereby suppressing generation of pseudo contours.

The selecting unit 85 selectively outputs the grayscale-converted image data by different methods, and is controlled by k grayscale switching signals satisfying ^2k = x + 1 (k is a natural number). Since 'x = 3', 'k = 2' and gradation switching signals are two of 's1 and s2'. Therefore, it is possible to switch four states including the lower 1/8, 1/4, 1/2 and the upper one by the logical combination of the two gray level switching signals.

Referring to FIG. 11, when performing gradation conversion using a parallax method and a sequential method, each step of 'x + 2 ^nx ' constituting one frame is M bits (M is a natural number), that is, 2 ^M units. In the luminance adjusting step (b), the luminance is adjusted for each RGB color, and the luminance controller 84 having the configuration of FIG. 10 performs this operation. Here, one step is divided by a step pulse sp.

In the upper 2 ^nx steps of gray level conversion by the sequential method, luminance is adjusted in 2 ^M unit brightness adjustment steps by using the reference clock (SCLK), which is a periodic square wave signal, and in the lower x steps of gray level conversion by the parallax method. X divided clocks having a cycle of (1/2 ¹ , 1/2 ² ,..., 1/2 ^x-1 , 1/2 ^x ) times divided by the reference clock are used (S130). At this time, the step of valid data interval ^x 1/2, 1/2 ^x-1, ...., ² 1/2, 2 ^M to sequentially correspond to the frequency division clock and the station to be used by ¹ 1/2 Brightness is adjusted by two unit brightness adjustment steps. In addition, after determining whether to use a division clock or a reference clock to adjust luminance, a clock signal according to a sequential method or a parallax method is selected according to the determination result, and the clock signal corresponding to the lower x steps is selected using the selected clock signal. In the parallax gray level, the brightness is adjusted using a division clock, and in the sequential gray level corresponding to the upper 2 ^nx steps, the brightness is adjusted using the reference clock.

At this time, in varying the brightness control according to the sequential method and the parallax method, a clock to be used for the brightness control in the corresponding step in the reference clock or the divided clocks is selected using k gray level switching signals.

In the example of FIG. 10, since 'x = 3', 'k = 2' and the gray level switching signals are two, s1 and s2. Therefore, the reference clock corresponding to each of the four states including the lower 1/8, 1/4, 1/2 and the upper one is divided by the logical combination of the two gray level switching signals s1 and s2. It will switch to use the 1/4 division clock and 1/8 division clock.

When the step pulse sp is applied, the divider 101 divides the reference clock SCLK and outputs a plurality of divided clocks.

At this time, the state in which the reference clock is output without being divided corresponds to the state N in which the selector 102 is not divided, and is used when adjusting the upper 2 ^nx luminance corresponding to the gradation conversion of the sequential method. In this case, the 10-bit gray scale conversion is taken as an example, so the upper 10 bits of D3 to D9 correspond to this. D2, which is just below the upper D3 to D9, is divided into 1/2 division clock, D1 is 1/4 division clock, and D0 is 1 /. Corresponds to the 1/8 frequency divider, which is 2 ^x (x = 3).

In adjusting the luminance, the clock to be used for the luminance adjustment (reference clock, 1/2 division clock, 1/4 division clock, 1/8 division clock) and luminance control signal corresponding to each of the preset or programmed RGB colors ( RBC, GBC, BBC (RGB Brightness Control) is compared to adjust the brightness. The luminance control signal is provided by a microprocessor or the like.

In response to the gray scale switching signals s1 and s2, the selector 102 selects a corresponding clock for adjusting brightness, and an output OUT of the selector 102 is input to the M bit counter 100. When the counter 100 counts and outputs the clock, which is the output OUT of the selector 102, for M bits, the comparators 104a, 104b, and 104c corresponding to the respective RGB output the respective luminance control signals RBC, GBC, and BBC. And the output of the counter 100 are compared. That is, the comparators 104a, 104b, and 104c corresponding to each RGB have an output of 'logic low' so that the output of the counter 100 corresponds to a section in which the luminance control signals RBC, GBC, and BBC are enabled (lighted). While maintaining a constant state, a signal of changing logic state to 'logic high' at the end of the enable is provided to the reset input of each flip-flop 103a, 103b, 103c.

Each flip-flop 103a, 103b, 103c is set as the step pulse sp is applied to maintain 'logic high' (in this case logic high is enabled) and then as the reset input becomes 'logic high' Each luminance signal (MROE, MGOE, MBOE) transitioned to logic low '(disabled) is output.

FIG. 11B shows the concept of the unit luminance adjustment step b. In FIG. 11C, the luminance signals MROE, MGOE, and MBOE in the unit luminance adjustment steps t1, t2 and t3 are shown in FIG. Indicates.

Here, the luminance signal (MROE, MGOE, MBOE) has indicated that they fold equivalence pulse, in the luminance control step t3 unit R is can be seen that having a luminance of 100% by representing a 2 ^M bit.

According to the present invention made as described above, by converting the RGB grayscale data by mixing different parallaxes and sequential methods to upper bits and lower bits, the sequential method is applied to higher steps. The problem can be solved, and by applying the parallax method using the enable signal in the lower bit and the sequential method in the upper bit, the distribution of the data in the output waveform of the gradation data is shaped into a dense part to suppress the generation of pseudo contours. It can be seen through the examples that it can be.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The present invention made as described above can suppress the problem of frequency increase of pseudo contour and system clock when converting the gray level of RGB image data, thereby improving the image quality of the image data and achieving device stabilization.

1 is a diagram showing a relationship between a frame and gradation.

2 is a diagram for explaining a principle of generating gradation data in a sequential manner.

3 is a view for explaining a principle of generating grayscale data in a parallax manner;

4 is a diagram for explaining a principle of generating pseudo contours in a parallax system.

Fig. 5 is a timing chart showing signal waveforms when gradation conversion is performed in steps of x + 2 ^nx according to the present invention.

FIG. 6 is a block diagram showing a gradation generating device for generating gradation data by gradation conversion of image data; FIG.

FIG. 7 is a block diagram illustrating the gray scale generating apparatus of FIG. 6 separated into RGB colors and subdivided.

FIG. 8 is a detailed block diagram illustrating an example of each gray scale generator of FIG. 7. FIG.

Fig. 9 is a timing diagram showing signal waveforms of an example in which gray scale conversion is performed in 3 + 2 ⁷ (131) steps.

FIG. 10 is a detailed block diagram illustrating the luminance control unit of FIG. 8. FIG.

Fig. 11 is a timing chart showing waveforms in which luminance is controlled according to an embodiment of the present invention.

12 is a flowchart showing a gray scale conversion method of image data according to the present invention;

13 is a flowchart showing a luminance adjustment method of the present invention.

* Description of the main parts of the drawing

80 memory unit 81 discrimination unit

82: parallax gradation unit 83: sequential gradation unit

84: luminance control unit 85: selection unit

Claims (15)

In the RGB (Red, Green, Blue) image data as a digital signal to generate RGB grayscale data by n-bit (n is a natural number) grayscale conversion having a PWM (Pulse Width Modulation) format, Determining a lower number of steps x (x is a natural number smaller than n) to be grayed out by the parallax method in the gray level conversion; Determining a total number of steps to be used in gradation conversion by x and n, wherein the total number of steps is x + 2 ^nx (lower x steps and upper 2 ^nx steps); Reading the image data; Determining whether the image data corresponds to the lower x steps; Gray-level converting the image data by a parallax method as the image data corresponds to lower x steps; Gradually converting the image data in a sequential manner as the image data corresponds to upper 2 ^nx steps; And Selectively outputting the gray-converted signal by the parallax method and the gray-converted signal by the sequential method Gray level conversion method of a video signal comprising a. The method of claim 1, In the gradation conversion by the parallax method, Gray level conversion of a video signal characterized in that the effective data section of the one step from the lowest is in the order of 1/2 ^x , 1/2 ^x-1 , ...., 1/2 ² , 1/2 ¹ Way. The method of claim 2, Selectively outputting the gray-converted signal, A gray level conversion method of an image signal, characterized by being controlled by k gray level switching signals satisfying 2 ^k = x + 1 (k is a natural number). The method of claim 3, wherein In the gradation conversion using the parallax method and the sequential method, The gray level conversion method of the video signal, characterized in that the brightness is adjusted for each RGB color by M bits (M is a natural number), that is, 2 ^M unit brightness adjustment steps. The method of claim 4, wherein In adjusting the brightness, In the upper 2 ^nx steps of performing gradation conversion by the sequential method, the reference clock is controlled by 2 ^M unit brightness adjustment steps. In the lower x steps of gray level conversion by the parallax method, the reference clock is divided by (1/2 ¹ , 1/2 ² ,..., 1/2 ^x-1 , 1/2 ^x ) times. X division clocks having a period are used, and the effective data interval of one step is sequentially reversed to each other by 1/2 ^x , 1/2 ^x-1 , ...., 1/2 ² , 1/2 ¹ The gray level conversion method of the video signal, characterized in that for adjusting the luminance in ^2M unit luminance adjustment step to correspond. The method of claim 5, In varying the brightness control according to the sequential method and the parallax method, And using the k gray level switching signals, selects a clock to be used for brightness adjustment in the corresponding step in the reference clock or the divided clocks. The method of claim 6, In adjusting the brightness, And adjusting luminance by comparing a clock to be used for luminance adjustment with a luminance control signal corresponding to each of predetermined or programmed RGB colors. The method according to any one of claims 1 to 7, And the step is divided by a plurality of step pulses, respectively. An apparatus for generating RGB grayscale data by converting RGB image data, which is a digital signal, with n-bit grayscale conversion having a PWM format, Memory means for storing the image data; The number of lower steps x to be gradated by the parallax method during the gradation conversion by reading the image data from the memory means, and the total number of steps to be used during gradation conversion by x and n x + 2 ^nx (lower x steps and upper 2 ^nx Discriminating means for discriminating whether or not the video data corresponds to the lower x steps or the upper 2 ^nx steps through information; Disparity gradation means for gradation conversion of the image data by a parallax method as the image data corresponds to lower x steps; Sequential gradation means for gradation conversion of the image data by a sequential method as the image data corresponds to upper 2 ^nx steps; And Selection means for selectively outputting the gray-converted signal by the parallax method and the gray-converted signal by the sequential method Gray level conversion apparatus of the video signal comprising a. The method of claim 9, In the time difference gradation means, The gray level conversion is performed so that the effective data section of the one step from the lowest is in the order of 1/2 ^x , 1/2 ^x-1 ,..., 1/2 ² , 1/2 ¹ . Gradation converter. The method of claim 10, And the selection means is controlled by k gradation switching signals satisfying 2 ^k = x + 1. The method according to any one of claims 9 to 11, Luminance control means for adjusting the luminance of each RGB color by the M bits (M is a natural number), that is, 2 ^M unit luminance adjustment steps, for the gray-converted signal using the parallax method and the sequential method. Gray level conversion method of the video signal, characterized in that it further comprises. The method of claim 12, The brightness control means, In the upper 2 ^nx steps of performing gradation conversion by the sequential method, the reference clock is controlled by 2 ^M unit brightness adjustment steps. In the lower x steps of gray level conversion by the parallax method, the reference clock is divided by (1/2 ¹ , 1/2 ² ,..., 1/2 ^x-1 , 1/2 ^x ) times. X division clocks having a period are used, and the effective data interval of one step is sequentially reversed to each other by 1/2 ^x , 1/2 ^x-1 , ...., 1/2 ² , 1/2 ¹ And gradation control of the frequency division clock in 2 ^M unit luminance adjustment steps so as to correspond to each other. The method of claim 13, The steps are each divided by a plurality of step pulses, The brightness control means, A divider for dividing the reference clock to generate the x divided clocks; A selector for selecting a clock to be used for luminance adjustment in a corresponding step from the reference clock or the division clocks under the control of the k gradation switching signals in order to change the luminance adjustment according to the sequential method and the parallax method; An M bit counter for counting the clock selected by the step pulse; A plurality of comparators for comparing the output of the counter with a luminance control signal corresponding to each of predetermined or programmed RGB colors; And One-to-one correspondence to the plurality of comparators, the flip-flop being enabled as the step pulse is applied and outputting a plurality of luminance signals disabled as the outputs of the corresponding comparators are enabled. Gray level conversion apparatus of the video signal comprising a. The method of claim 14, The flip flop, And an RS (Reset Set) -flip-flop, wherein the output of the comparator is a reset input and the step pulse is a set input.