KR20050115183A - Apparatus and method for compensation of correlated color temperature of gray scale in lce - Google Patents

Abstract

The present invention provides an LCD gray level correlation color temperature correction apparatus, comprising: a camera for photographing an external image; A memory in which the captured image and screen data are stored; An image processor for outputting an RGB signal by correcting a correlated color temperature of an image input through the camera and screen data read from the memory according to a gray level correlation color temperature correction control signal; A display unit which receives the RGB signal having the correlated color temperature corrected and displays screen data of an LCD according to the RGB three primary colors; And a controller for controlling the image processor with a gray level correlation color temperature correction control signal of the screen data read out from the camera module and the memory.

Description

LCD Level Correlated Color Temperature Correction Device and Method {APPARATUS AND METHOD FOR COMPENSATION OF CORRELATED COLOR TEMPERATURE OF GRAY SCALE IN LCE}

The present invention relates to an LCD, and more particularly, to a method of correcting a gray level correlation color temperature of an LCD in which a constant correlation color temperature is maintained according to a change in an input value of a gray level by adjusting values of RGB three primary colors.

Recently, liquid crystal displays (LCDs, hereinafter referred to as "LCDs") have been adopted as various display devices such as monitors and TVs of personal computers because of their excellent characteristics such as thin, light, high quality, high resolution, and low power consumption. However, in terms of color reproducibility, the physical and electro-optical properties of liquid crystals are still falling short of the performance of conventional cathode ray tubes (CRTs).

In general, CRTI has almost no change in the chromaticity coordinates of the three primary colors and the correlated color temperature (CCT) of the gray scale according to the change of the RGB primary colors input, and thus accurate color reproduction is possible. The change occurs largely depending on the value, and accurate color reproduction is impossible. The color temperature is defined as the absolute temperature of a complete radiator (black body) having the same chromaticity as any light source as the color temperature of the light source, and the color temperature close to the trajectory of the black body is referred to as the correlated color temperature.

The color coordinates of the three primary colors of the LCD mounted in the conventional portable terminal are as shown in FIG.

In general, the color reproduction characteristic of LCDs is that the lower the input digital value, the higher the correlated color temperature of the gray level.

1 is an exemplary view showing three primary colors and gray level chromaticity coordinates of a conventional LCD.

Referring to FIG. 1, first, (a) and (b) of FIG. 1 indicate that black (R {0}, G {0}, As the gray level is lowered, the chromaticity coordinates are biased toward B as the gray level decreases according to the change of the input digital value of B {0}). In addition, when the input digital value is increased to change to White (R {255}, G {255}, B {255}), the chromaticity coordinates of the three primary colors RGB may be distorted.

2 is a view for explaining the characteristics of the RGB three primary colors of the conventional LCD, Figure 2 (a) is the input digital value (Input Digital Value) from 0 to 255 by increasing the ⓐ waveform of White and ⓑ waveform of Red And it can be seen that the luminance (Luminance [cd / m ² ]) in the characteristic curve, such as ⓒ waveform of Green and ⓓ waveform of Blue.

The result of adding the ⓑ to ⓓ waveforms in FIG. 2 (a) should be the same as the ⓔ waveform of White indicating relative luminance [%] according to the input digital value. However, as can be seen from (b) of Figure 2 has the same error as the ⓕ waveform. Thus, as shown in FIG. 3A having a target value of 6500k and FIG. 3B having a target value of 7500k as the correlated color temperature, as the input digital value described above is lower, the correlated color temperature of the gray level is increased, so that the color of the image is darker. It can be seen that out of the target color temperature target value of 6500k and 7500k.

Accordingly, the conventional LCD has a problem in that accurate color reproduction is impossible due to a large change in the chromaticity coordinates of the three primary colors and the correlated color temperature (CCT) of the gray scale according to the change of the RGB three primary color input values.

Accordingly, the present invention has been created to solve the above problems, by adjusting the input digital values of each of the three RGB primary colors to maintain a constant correlation color temperature in accordance with the change of the input value of the gray level, it is possible to accurate color reproduction The purpose of the present invention is to provide a method for correcting the gray level correlation color temperature of an LCD.

In order to achieve the above object, the present invention provides a gray level correlation color temperature correction apparatus of LCD, comprising: a camera for photographing an external image; A memory in which the captured image and screen data are stored; An image processor for outputting an RGB signal by correcting a correlated color temperature of an image input through the camera and screen data read from the memory according to a gray level correlation color temperature correction control signal; A display unit which receives the RGB signal having the correlated color temperature corrected and displays screen data of an LCD according to the RGB three primary colors; And a controller for controlling the image processor with a gray level correlation color temperature correction control signal of the screen data read out from the camera module and the memory.

In addition, the present invention for achieving the above object, in the gray level correlation color temperature correction method of the LCD, the luminance signal (Y) and the color difference signal (Cr, Cb) corresponding to the image to be displayed on the LCD RGB signal And converting the number of bits of the converted RGB signal into a predetermined number of bits; Correcting the RGB signal by increasing the R signal by increasing the RGB signal adjusted to the predetermined number of bits and reducing the B input value; And displaying the corresponding image on the LCD using the corrected RGB input value.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It should be noted that in the following description, only parts necessary for understanding the operation and operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

In the following description specific details regarding the correlated color temperature correction of the present invention are presented to provide a more general understanding of the present invention. It will be apparent to one of ordinary skill in the art that the present invention may be readily practiced without these specific details and also by their modifications.

In the following description, the correlated color temperature of the gray level is adjusted to the input RGB digital value in the range of 6500 ~ 8000K.

Thus, for explaining the operation of the present invention will be described an example of a portable terminal basically equipped with an LCD.

4 is a diagram illustrating a configuration of a portable terminal to which an LCD gray level correlation color temperature correction device according to an embodiment of the present invention is applied. Here, the portable terminal may be a portable telephone.

Referring to FIG. 4, the RF unit 21 performs communication of the portable terminal. The RF unit 21 includes an RF transmitter for upconverting and amplifying a frequency of a transmitted signal, and an RF receiver for low noise amplifying and downconverting a received signal.

The data processor 23 includes a transmitter for encoding and modulating the transmitted signal and a receiver for demodulating and decoding the received signal. That is, the data processor 23 may include a modem and a codec. The codec includes a data codec for processing packet data and an audio codec for processing an audio signal such as voice.

The audio processor 23 plays a function of reproducing the received audio signal output from the data processor 23 or transmitting a transmission audio signal generated from the microphone MIC to the data processor 23. The audio processor 23 converts audio data from the data received from the data processor 22 into an audible sound through a speaker SPK, and outputs the audio signal input from the microphone MIC to the data processor 22.

The keypad 27 has keys for inputting numeric and text information and function keys for setting various functions.

The memory 29 may be composed of program memory and data memories. The program memory includes programs for controlling a general operation of the portable terminal and changes in input values of gray levels without deterioration in characteristics such as correlated color temperature, gamma, brightness, and contrast ratio according to input RGB of the display unit according to an exemplary embodiment of the present invention. Programs for adjusting the input digital value of each of the RGB three primary colors for adjusting the change in the correlation color temperature according to In addition, the data memory temporarily stores data generated during the execution of the programs.

The controller 10 performs a function of controlling the overall operation of the portable terminal. In addition, the controller 10 may include the data processor 23. In addition, the control unit 10 controls the overall operation according to the control of the input digital value of each of the RGB three primary colors for correcting the change in the correlated color temperature according to the change in the input value of the gray level in accordance with an embodiment of the present invention. In addition, the control unit 10 controls to maintain a constant color temperature by using a look-up table (LUT) of the present invention to improve the gray level according to the value of the RGB three primary colors according to an embodiment of the present invention.

The camera 50 photographs image data and includes a camera sensor that converts the photographed optical signal into an electrical signal. It is assumed here that the camera sensor is a CCD sensor.

The signal processor 60 converts the video signal output from the camera 50 into an image signal. The signal processor 60 may be implemented by a digital signal processor (DSP). In this case, the signal processor 60 converts an electrical signal into an image signal according to a sampling period. In addition, a video signal converted from an electrical signal is output through a Bayer pattern inferring lost pixel information for each pixel by using neighboring pixel information. Here, the camera module 100 is used to collectively mean the camera 50 and the signal processor 60.

The image processor 70 performs a function of generating screen data for displaying an image signal output from the signal processor 60. The image processor 70 transmits the image signal received under the control of the controller 10 or the image data captured by the camera 50 in accordance with the standard of the display unit 80, and compresses and extends the image data. In addition, the image processor 70 outputs image data by adjusting input digital values of respective RGB primary colors for correcting a change in a correlated color temperature according to a change in an input value of a gray level according to the control of the controller 10 according to an embodiment of the present invention. . In addition, the sound image processing unit 70 increases the R input value and decreases the B input value based on the G input value of the input digital value according to an embodiment of the present invention to maintain the same brightness of the gray level of the input digital value. While adjusting the RGB value so that the correlated color temperature is around 6500K or 7500K, the output is adjusted.

The display unit 80 displays messages generated during program execution under the control of the controller 10. In addition, the display unit 80 displays an image signal output from the image processing unit 70 on a screen in the camera photographing mode, and displays user data output from the control unit 10. Here, the user data refers to an icon representing the remaining battery capacity, reception rate, bell / vibration, and the like. In addition, the display unit 80 displays the screen data through the RGB three primary colors which are corrected according to the change in the correlated color temperature according to the change in the input value of the gray level of the image processor 70 according to the exemplary embodiment of the present invention. The display unit 80 may use an LCD. In this case, the display unit 80 may include an LCD controller, a memory capable of storing image data, and an LCD display element. Here, when the LCD is implemented in a touch screen manner, the keypad 27 and the LCD may be input units.

Looking at the operation of the portable terminal with reference to FIG. 4, when the user performs a dialing operation through the keypad 27 when the call is set, the dialing mode is set, the controller 10 detects this and receives the dial information received through the data processor 23. After processing the RF signal through the RF unit 21 to output. Thereafter, when the other subscriber generates the response signal, the counter subscriber detects it through the RF unit 21 and the data processor 23. Thereafter, a user establishes a voice call path through the audio processor 25 to perform a communication function. In addition, in the incoming mode, the controller 10 detects the incoming mode through the data processor 23 and generates a ring signal through the audio processor 25. Thereafter, when the user responds, the controller 10 detects this, and a voice call path is formed through the audio processor 25 to perform a communication function. In the outgoing and incoming modes, voice communication is described as an example, but a data communication function for communicating packet data and image data in addition to the voice communication may be performed. In addition, when performing a standby mode or text communication, the controller 10 displays text data processed by the data processor 23 on the display 80.

Also, the portable terminal may perform an operation of capturing a person or an environment and displaying or transmitting the image on a video screen. First, the camera 50 may be mounted on a portable terminal or connected to a predetermined location outside. That is, the camera 50 may be an external camera or an internal camera. The camera 50 may use a charge coupled device (CCD) sensor. The image captured by the camera 50 is converted into an electrical signal by an internal CCD sensor and then applied to the signal processor 60. Then, the signal processor 60 converts the image signal into digital image data and outputs the image signal to the image processor 70.

Referring to the operation of correcting the chromaticity coordinates of the RGB three primary colors and the correlated color temperature of the gray levels of the portable terminal, first, an image captured by the camera 50 is controlled as an image signal through the signal processor and the image processor 70 under the control of the controller 10. Is converted. Then, a digital value of the corresponding RGB three primary colors is output to the display unit 80 by using a LUT adjusting an input digital value of each of the three RGB primary colors to correct a change in the correlation color temperature to have a constant correlation color temperature. In addition, the image captured by the camera 50 may be coded through the image processor 70 under the control of the controller 10, and the coded image data may be stored in the memory 29. Then, the controller 10 reads the image data stored in the memory 29 and the screen data according to menus and modes from the memory 29 and outputs the image data to the image processor 70. The image processor 70 outputs the adjusted input digital value to the display unit 80 by using an LUT that adjusts input digital values of each of the three RGB primary colors so as to correct the change in the correlation color temperature for the screen data so as to have a constant correlation color temperature. Then, the display unit 80 accurately reproduces the colors displayed on the screen data. The image processing unit 70 is provided with an internal configuration as shown in FIG.

That is, as shown in FIG. 5, the image codec 71 codes (MPEG, JPEG) data of the image captured by the camera 50 and outputs the digital luminance signal Y and the CrCb of the color difference signal as 8 bits, respectively.

The color space conversion unit 72 receives 8-bit data of the output YCrCb of the image codec 71 and converts it into RGB and outputs the number of bits of the RGB three primary colors as R: 8, G: 8, and B: 8.

The first image signal adjusting unit 73 receives the 8-bit image signal of each of the RGB three primary colors, and erases three bits from the least significant bit (LSB) among the three primary colors, and removes two bits from the least significant bit (LSB) of the three primary colors. Erase. This reduces the number of bits, because the image must be processed only with bits that are limitedly input. In this case, since G represents luminance information, one bit of information is additionally provided than the color information of R and B. Accordingly, the number of bits of the RGB three primary colors becomes R: 5, G: 6, B: 5, and is input to the correlated color temperature correction unit 74.

The correlated color temperature correction unit 74 has an internal configuration as shown in FIG.

The second image signal adjusting unit 74a sets the number of input digital bits of the RGB three primary colors in R: 5, G: 6, B: 5 to R: 6, G: 6, so that the luminance is a constant correlation color temperature while maintaining the original value. Adjust to B: 6 and output. That is, the G leaves the number of bits as it is, adds one bit as the least significant bit to the number of bits of the R and B, makes the number of bits six, and outputs the LUT74b.

The LUT74b receives RGB output signals of the second image signal controller 74a sequentially and converts the gray level chromaticity coordinates according to preset 6-bit RGB information under the control of the controller 10, and adjusts the RGB to maintain a correlated color temperature. RGB 6 bits are output to the display unit 80 using the LUT.

The above-described correlated color temperature correction unit 74 of FIG. 6 is included in the controller 10 to output the R: 5, G: 6, and B: 5 bits output from the first image signal adjusting unit 73 of the image processing unit 70 using the LUT74b. It is also possible to configure the display unit 80 to output 6-bit RGB corresponding to the bit indicated by each RGB.

7 is a flowchart illustrating a gray level correlation color temperature correction method of an LCD according to an embodiment of the present invention.

Referring to FIG. 7, in step 711, the controller 10 determines whether a mode according to a key input is a camera mode.

As a result of the determination, if it is not the camera mode, in step 713, the controller 10 recognizes the mode and reads image data according to the recognized mode from the memory 29.

In step 715, the controller 10 codes the read image data to control the luminance signal Y and the color difference signals Cr and Cb to be output as image signals.

In contrast, in the camera mode, in step 717, the controller 10 codes the image signal captured by the camera 50. In step 719, the controller 10 controls the luminance signal Y and the color difference signals Cr and Cb to be output as coded image signals. In this case, the image data of the image image captured according to whether the user stores the image is coded and stored in the memory 29 under the control of the controller. Here, the image data stored in the memory 29 is recognized as not the camera mode, and the image data stored in the memory 20 is read and the same process as in steps 711 to 715 is performed. The correlated color temperature is corrected.

After performing steps 715 and 719, in step 721, the controller 10 converts the image signal for YCrCb into RGB. Since the method of converting the YCrCb signal into an RGB signal uses a general equation, a detailed description thereof will be omitted.

In step 723, the control unit 10 controls 3 bits to be erased from the least significant bit of the 8 bits of the R and B input signals among the respective RGB 8 bit input signals, and controls 2 bits to be erased from the least significant bit of the 8 bits of the G signal.

Then, in step 725, the control unit 10 adjusts the video signals for R: 5 bits, G: 6 bits, and B: 5 bits obtained in step 723 to be 6 bits, respectively.

That is, 6 bits for the G signal are kept as they are, and one least significant bit is added to the R and B signals of the 5 bits.

In operation 727, the controller 10 reads from the LUT74b an RGB input value corresponding to the 6-bit RGB input value and outputs the RGB input value. Here, the LUT74b has a different LUT74b according to the correlated color temperature.

That is, as shown in FIG. 8A of the LUT74b with the correlated color temperature set to 6500K, and 8B of the LUT74b with the correlated color temperature set to 7500K.

As shown in FIG. 8A and FIG. 8B, it can be seen that the R input value increases and the B input value decreases around the G value, and the correlation color temperatures are located at almost 6500K and 7500K. In addition, it can be seen that chromaticity coordinates according to RGB input values are also located at almost one place. FIG. 9 shows the curve of the LUT74b used for the gray level correlation color temperature correction. That is, as can be seen from the drawing of FIG. 9, it can be seen that the R input value ② is increased and the B input value ③ is decreased based on the G input value ①. In addition, the waveform shown in Fig. 10 is considered to compensate for the gamma characteristic curve n generated by the LCD itself shown in Fig. 10.

As a result, this can be clearly seen by the gray chromaticity coordinates according to the gray level correlation color temperature correction according to the correlation color temperature 6500K corresponding to FIG. 8A as shown in FIG. 11A, and through the constant range of the gray chromaticity coordinates. 11b can be clearly seen by gray chromaticity coordinates according to gray level correlation color temperature correction according to the correlation color temperature 7500K corresponding to FIG. 8b.

In step 729, the control unit 10 outputs the RGB input value read from the LUT74b to the display unit 80 of the LCD in step 727. Then, the display unit 80 corrects the RGB input value of the image captured by the camera 50 in the camera mode or the screen data displayed in the normal mode other than the camera mode to the RGB input value whose correlated color temperature of gray level is corrected by the LUT74b. Can be reproduced accurately. 12A and 12B are exemplary views showing correlation color temperatures according to RGB inputs at target correlation color temperatures 6500K and 7500K according to an exemplary embodiment of the present invention. 12A and 12B do not correct a dark region having a large difference in correlation color temperature because the color recognition ability decreases when the brightness decreases due to visual characteristics.

Therefore, in the gray level correlation color temperature correction method of the LCD of the present invention, the input RGB digital value is adjusted through the LUT so that the correlation color temperature of the gray level falls within the range of 6500K to 8000K. The luminance is maintained and the correlated color temperature is adjusted to be nearly constant according to the chromaticity coordinates and input values of the RGB three primary colors of gray level.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described in detail above, the present invention adjusts the input digital value of each of the three RGB primary colors and displays the LCD through the adjusted RGB input digital value, thereby maintaining a constant correlation color temperature according to the change of the input value of the gray level. Since color can be reproduced, there is an effect that accurate color can be reproduced through LCD.

In addition, since accurate color reproduction is possible, the user can receive a realistic image through the LCD.

1 is an exemplary view showing three primary colors and gray level chromaticity coordinates of a conventional LCD.

2 is a view for explaining the luminance characteristics according to the three primary colors of the conventional LCD.

3A and 3B are exemplary diagrams showing a correlation color temperature according to a digital input at conventional target correlation color temperatures 6500K and 7500K.

4 is a diagram illustrating a configuration of a portable terminal to which an LCD gray level correlation color temperature correction apparatus according to an embodiment of the present invention is applied.

FIG. 5 is an exemplary view illustrating an internal configuration of the image processor of FIG. 4. FIG.

6 is an exemplary view showing the internal configuration of the correlated color temperature correction unit in FIG.

7 is a flowchart illustrating a gray level correlation color temperature correction method of an LCD according to an embodiment of the present invention.

8A and 8B are exemplary views showing LUTs at target correlation color temperatures 6500K and 7500K in FIG. 5;

9 is a diagram showing a LUT curve used for correlated color temperature correction of gray levels of the present invention.

10 is a view for explaining the gamma characteristics when the gray level correlation color temperature correction of the LCD of the present invention.

11A and 11B show gray chromaticity coordinates according to gray level correlation color temperature correction at target correlation color temperatures 6500K and 7500K.

12A and 12B are exemplary diagrams showing correlation color temperatures according to RGB inputs at target correlation color temperatures 6500K and 7500K according to an exemplary embodiment of the present invention.

*** Explanation of symbols for main parts of drawing ***

10: control unit 21: RF unit

23: data processor 25: audio processor

27: keypad 29: memory

50: camera 60: signal processing unit

70: image processor 71: video codec

72: color space conversion unit 73: first production signal adjustment unit

74: correlated color temperature correction unit 74a: second video signal adjustment unit

74b: LUT 100: camera module

80: display unit ANT: antenna

MIC: Microphone SPK: Speaker

Claims (15)

In LCD gray level correlation color temperature correction device, A camera for capturing an external image; A memory in which the captured image and screen data are stored; An image processor for outputting an RGB signal by correcting a correlated color temperature of an image input through the camera and screen data read from the memory according to a gray level correlation color temperature correction control signal; A display unit which receives the RGB signal having the correlated color temperature corrected and displays screen data of an LCD according to the RGB three primary colors; And a controller configured to control an image processor by a gray level correlation color temperature correction control signal of screen data read from the camera module and the memory. The image processing apparatus of claim 1, wherein the image processor comprises: an image codec for coding an image to be displayed on an LCD and outputting a luminance signal (Y) and a color difference signal (Cr, Cb) corresponding to the image; A color space converter which receives the luminance signal Y and the color difference signals Cr and Cb and converts them into RGB signals having a predetermined bit; A first image signal adjusting unit which removes a predetermined number from the least significant bit of the RGB signal, adjusts the predetermined number of bits, and outputs an adjusted RGB signal; And a correlated color temperature correction unit that receives the RGB signal adjusted to the predetermined number of bits, increases the R signal based on the G signal, and decreases the B input value. The display apparatus of claim 2, wherein the correlated color temperature corrector comprises: a second image signal adjuster configured to output an RGB signal adjusted to a predetermined number of bits by increasing a least significant bit of the RGB signal; Maintain the luminance value of the gray level of the RGB signal input from the second image signal adjusting unit as it is, and correct the RGB signal input to the LCD so that the correlated color temperature and the gray level chromaticity coordinate are maintained in a constant area according to the RGB signal. And a lookup table (LUT) for outputting the RGB signal to the LCD. The method of claim 3, wherein the second video signal adjusting unit adjusts and outputs the number of input digital bits of RGB three primary colors from R: 5, G: 6, and B: 5 to R: 6, G: 6, and B: 6. Said device. 4. The apparatus as claimed in claim 3, wherein the second image signal adjusting unit adds one bit to the least significant bit of the R and B signals among the 5-bit R and B signals and the 6-bit G signal. The apparatus of claim 1, wherein the look-up table (LUT) is a table of RGB signals corrected according to an output value of a second video signal. 7. The apparatus as claimed in claim 6, wherein the corrected RGB signals each consist of 6 bits. 7. The apparatus as claimed in claim 6, wherein the lookup table (LUT) is an RGB signal corrected for a gray level correlation color temperature between 6000K and 8000K. The apparatus of claim 1, wherein the image processor corrects the RGB signal based on a gray level correlation color temperature between 6000K and 8000K. In the gray level correlation color temperature correction method of LCD, Converting the luminance signal Y and the color difference signals Cr and Cb corresponding to the image to be displayed on the LCD into an RGB signal, and adjusting the number of bits of the converted RGB signal to a predetermined number of bits; Correcting the RGB signal by increasing the R signal by increasing the RGB signal adjusted to the predetermined number of bits and reducing the B input value; And displaying the corresponding image on the LCD using the corrected RGB input value. The method of claim 10, wherein the correcting of the RGB signal maintains the luminance value of the gray level before correction and corrects the RGB signal input to the LCD such that the correlated color temperature and the gray level chromaticity coordinate are maintained in a predetermined area according to the RGB signal. Said method, characterized in that. 11. The method of claim 10, wherein the adjusting to the predetermined number of bits comprises: erasing three bits from the least significant bit of the R and B signals among the eight bits of the RGB signal, and two bits from the least significant bit of the G signal; And adjusting the number of bits by adding one bit to the least significant bit for each of the R and B signals having a 5: 6: 5 bit number for the RGB signal. The method as claimed in claim 10, wherein the corrected RGB signal is obtained from a look-up table (LUT) consisting of a corrected RGB signal corresponding to the RGB signal adjusted by a certain number of bits. The method as claimed in claim 13, wherein each of the corrected RGB signals consists of 6 bits. The method as claimed in claim 10, wherein the corrected RGB signal is an RGB signal corrected for a gray level correlation color temperature between 6000K and 8000K.