CN1326404C - Automatic colour temp regulating method and device - Google Patents

Abstract

The automatic color temperature adjustment method and device relate to electronic technology, in particular to digital processing technology of analog video signals. According to the value of the output signal after A/D conversion, the present invention feeds back to the input signal before A/D conversion to adjust its input. The beneficial effect of the present invention is that under the premise that the parameters of the liquid crystal screens are consistent, each liquid crystal display can obtain the same brightness-color temperature characteristics, and it is not necessary to perform OFFSET and GAIN of the A/D converter during the production process. debugging. The invention can remarkably improve the display picture quality, ensure the color temperature consistency of batch products, and improve production efficiency at the same time.

Description

Automatic color temperature adjustment method and device

technical field

The invention relates to electronic technology, in particular to digital processing technology of analog video signal.

Background technique

A display, especially a liquid crystal display circuit is generally composed of a CPU, an A/D converter and a display format converter. Under the control and management of the CPU, it first converts the analog R, G, and B signals output by the PC display adapter to A/D, and then converts the digital plane display format, and then sends the signal to the LCD screen for display.

Due to the discreteness of the performance of the A/D converter and the inconsistency of the analog R, G, and B signal amplitudes output by different PC display adapters, when changing different LCD monitors or PC signal sources, the brightness of the LCD monitor—— If the color temperature characteristics change, automatic color temperature adjustment is required to ensure the display effect.

However, some LCD chip suppliers, such as PIXELWORKS of the United States, do not describe the automatic color temperature adjustment function in the relevant specifications and technical documents of their PW13X series LCD ASICs.

The results of the actual test show that:

1. For the same display signal, different PC display adapters have inconsistent output amplitudes;

2. Different A/D converters may have different zero points and full scales of digital image signals.

Therefore, for LCD monitors that do not have the function of automatic color temperature adjustment, when connecting with different computer hosts (display adapters): 1) Due to the inconsistent amplitude of the analog signal output by the display adapter, the digital image output by the A/D converter The signal will also change accordingly, resulting in a change in the brightness-color temperature characteristics of the liquid crystal display; 2) Due to the discreteness of the performance of the A/D converter, the offset (OFFSET) of each A/D converter is required in the production process ) and gain (GAIN) for debugging.

Contents of the invention

The technical problem to be solved by the present invention is to provide a general realization method of automatic color temperature adjustment for displays without automatic color temperature adjustment function, especially liquid crystal displays.

The technical solution adopted by the present invention to solve the technical problem is to provide an automatic color temperature adjustment method, which feeds back the input signal before A/D conversion according to the value of the output signal after A/D conversion, and adjusts its input.

The signals include signals of R, G, and B channels. The present invention adjusts the OFFSET and GAIN of the input signal according to the maximum and minimum values of the R, G, and B signals output by A/D conversion, so that the maximum value of each signal is the maximum standard, and the minimum value is the minimum standard. Include the following steps:

1) The gain of the A/D converter R, G, and B channels is set to a fixed value;

2) Adjust the offset of the R, G, and B channels until the values of a group of registers of R, G, and B are just equal to their standards;

3) Adjust the gain of the R, G, and B channels until the values of another set of registers of R, G, and B are just equal to their standards;

4) Write the adjusted gain and offset values of the R, G, and B channels into the EEPROM.

The R, G, and B registers are divided into two groups, which are the 3 minimum value registers of R, G, and B and the 3 maximum value registers of R, G, and B;

The standard of the value of the minimum value register is the minimum standard of the black level value of analog R, G, B transformed into digital R, G, B by A/D;

The standard of the value of the maximum value register is the maximum standard of the white level value of analog R, G, B transformed into digital R, G, B by A/D.

The maximum standard of the numbers R, G, B is FFH, and the minimum standard of the numbers R, G, B is 00H.

The concrete steps of step 2) are:

a) The offset of the A/D converter R, G, and B channels is set to a minimum value;

b) Increase the R, G, and B channel offset values gradually, and monitor the three minimum value register values at the same time. When a certain register value is just equal to 00H, the corresponding offset will not be increased; continue to increase other offset values until 3 register values are exactly equal to 00H.

The concrete steps of step 3) are:

c) setting the gain of the A/D converter R, G, and B channels to the maximum value FFH;

d) Gradually reduce the gain values of R, G, and B channels respectively, and monitor the 3 maximum register values at the same time. When a certain register value is just equal to FF, the corresponding gain will not be reduced; continue to reduce other gain values until The 3 register values are exactly equal to FFH.

The present invention increases or decreases offset and gain stepwise or convergently. The fixed value is an intermediate value.

The present invention increases or decreases offset and gain stepwise or convergently.

The present invention also provides an automatic color temperature adjustment device, including a CPU, amplifier, A/D converter and 6 registers, the analog signal is input to the A/D converter through the amplifier, and the output of the A/D converter is fed back to the amplifier through the CPU ; The 6 registers record the maximum and minimum values of R, G, and B channels respectively, and the CPU adjusts the gain and offset of the A/D input signal according to the values in the 6 registers until each channel The maximum value of the signal is the maximum standard, and the minimum value is the minimum standard. The maximum standard is FFH, and the minimum standard is 00H.

The 6 registers record the maximum value register and the minimum value register of R, G, and B channels respectively;

The amplifier is used to adjust the offset and gain of the R, G, and B channels;

The CPU adjusts the amplifier according to the values in the six registers.

The amplifier is an adjustable gain amplifier.

The beneficial effect of the present invention is that under the premise that the parameters of the liquid crystal screens are consistent, each liquid crystal display can obtain the same brightness-color temperature characteristics, and it is not necessary to perform OFFSET and GAIN of the A/D converter during the production process. debugging. Not using the liquid crystal display of the present invention, the inconsistency of the output signal amplitude of the PC display adapter and the discreteness of the performance of the A/D converter will be reflected together on the image signal data output by the A/D converter, and finally reflected in the aforementioned technology Among the 6 registers mentioned in the scheme, the present invention automatically adjusts according to the data values of the 6 registers, so these two problems are solved together. The invention can remarkably improve the display picture quality, ensure the color temperature consistency of batch products, and improve production efficiency at the same time.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

Fig. 2 is a schematic diagram of the device of the present invention.

Detailed ways

When the liquid crystal display normally receives and processes analog signals from the PC, the A/D converter outputs 3×8-bit (R, G, B) digital image signals in real time. In the format conversion integrated circuit, G PORT has three 8-bit maximum value registers and three 8-bit minimum value registers, which respectively record the maximum and minimum values of R, G, and B data in the previous frame image, that is, the White level value and black level value. Ideally, these two values should be exactly FFH and 00H. According to actual test results in actual applications, these two values deviate from FFH and 00H, and the system does not grasp the analog R, G from the PC display adapter. , the degree of inconsistency of B and the degree of discreteness of the A/D converter, so the use of other external compensation methods lacks basis and is difficult to implement. Since the black signal can be obtained through the reverse process, when we are sure that there is a white signal in a frame image, the system only needs to adjust the two deviated values back to the ideal value, and naturally realize the input and output characteristics of the entire signal. calibration. Specifically, the system control software adjusts and sets the OFFSET and GAIN of the front-end of the A/D converter according to the data of these 6 registers, so as to change the front-end signal OFFSET and GAIN of the A/D converter, so that the signal added to the A/D The starting point and amplitude of the signal at the entrance of the D converter change, so that the output of the A/D converter also changes, and the data of the register changes accordingly; and then continue to adjust the front end of the A/D converter according to the changes in the register data OFFSET and GAIN until the minimum value register is just 00H or a value close to 00H; the maximum value register is just the hexadecimal number FFH or close to FFH, so as to achieve the purpose of automatic color temperature adjustment. The method of adjustment can be step-by-step (fixed step size) or convergent (step size from large to small).

As a specific embodiment of the present invention, the PW13X series liquid crystal display circuit platform of American PIXELWORKS is taken as an example to describe the implementation of the present invention in detail, see FIG. 1 and FIG. 2 .

When the liquid crystal display composed of the PW13X series integrated circuit platform is working normally, its built-in A/D converter first converts the analog signal R, G, B from the PC into a 3×8-bit real-time digital signal, and completes a frame of image data After the A/D conversion, write the maximum and minimum values of R, G, and B into the following 6 G PORT registers:

G PORT register base address Base Address＝Byte 40h

Red minimum value register offset address REDMIN(7:0) Byte offset 0E

Red maximum value register offset address REDMAX(7:0) Byte offset 0F

Green minimum value register offset address GRNMIN(7:0) Byte offset 10

Green maximum value register offset address GRNMAX(7:0) Byte offset 11

Blue minimum value register offset address BLUMIN(7:0) Byte offset 12

Blue maximum register offset address BLUMAX(7:0) Byte offset 13

Among them, the values of the 3 minimum value registers correspond to the black or inverse part of the image, and the 3 maximum value registers correspond to the white part of the image, which is the part with the highest brightness. Because different PC display adapters have inconsistent output amplitudes and different PW13X The A/D converter of series integrated circuit has these two reasons of different digital image signal zero point and full scale, cause minimum value register not necessarily just to be 00H, maximum value register not necessarily just to be FFH, now carry out by the method of the present invention Adjustment, these adjustments are realized through the system control software:

1) Set the GAIN of the R, G, and B channels of the A/D converter to an intermediate value of 80H;

2) Set the OFFSET of the R, G, and B channels of the A/D converter to the minimum value 00H;

3) Gradually increase the OFFSET values of R, G, and B channels respectively, and monitor the three minimum value registers at the same time. When a certain register value is just equal to 0, the corresponding OFFSET will not be increased; continue to increase other OFFSET values until the three register values Both are exactly equal to 00H;

4) The GAIN of the R, G, and B channels of the A/D converter is set to the maximum value FFH;

5) Decrease the GAIN values of R, G, and B channels gradually, and monitor the 3 maximum registers at the same time. When a certain register value is just equal to FFH, the corresponding GAIN will not be reduced; continue to reduce the other GAIN values until 3 All register values are exactly equal to FFH;

6) After the automatic color temperature adjustment is completed, the 6 adjusted data values are written into the EEPROM for use when the device is turned on next time.

In the above-mentioned step 5), if the output of the A/D converter exceeds the maximum value, then limit to FFH, and the value of the maximum value register is also FFH at this time, so specifically when adjusting GAIN, first reduce GAIN so that the value of the maximum value register The value starts to change (decrease) from FFH, and then fine-tunes GAIN so that the A/D output is exactly FFH.

The above-mentioned increasing or decreasing algorithm can adopt a stepwise method, that is, increase or decrease with a step size of 1; or a convergent method, that is, the step size changes from large to small.

The implementation of convergent adjustment is as follows: (Take PW13X of PIXELWORKS in the United States as an example)

1. Set the GAIN of the R, G, and B channels of the A/D converter to an intermediate value of 80H;

2. Set the OFFSET of the R, G, and B channels of the A/D converter to the minimum value of 00H;

3. Set the R, G, and B channel OFFSET values to 40H, and monitor the three minimum value registers at the same time. If the register value is greater than 00H, then increase the R, G, and B channel OFFSET values by the absolute value of the aforementioned set value increment Half of it is set to 60H; if the register value is equal to 00H, then reduce the OFFSET value of the R, G, and B channels by half of the absolute value of the aforementioned set value increment, which is 20H, and monitor the three minimum value registers at the same time, repeat the above steps ( The step size of the increase or decrease of the set value is 20H, 10H, 8H, 4H, 2H, 1H) until the register value is just equal to 00H;

4. The GAIN of the R, G, and B channels of the A/D converter is set to the maximum value of FFH;

5. Set the GAIN value of the R, G, and B channels to 80H respectively, and monitor the three maximum value registers at the same time. If the register value is less than FFH, then increase the GAIN value of the R, G, and B channels by the absolute value of the aforementioned setting value increment Half of it is set to 60H; if the register value is equal to FFH, then reduce the GAIN value of the R, G, and B channels by half of the absolute value of the aforementioned set value increment, which is 40H, and monitor the three maximum value registers at the same time, repeat the above steps ( The increment and decrement steps of the set value are 40H, 20H, 10H, 8H, 4H, 2H, 1H) until the register value is just equal to FFH; the automatic color temperature adjustment is completed;

6) Write 6 adjustment data values into EEPROM for the next boot.

The embodiment of the device of the present invention is shown in FIG. 2 . The present embodiment comprises a CPU, amplifier, A/D converter and 6 registers, the analog signal is input into the A/D converter through the amplifier, and the output of the A/D converter is fed back to the amplifier; the 6 registers respectively record R, The maximum and minimum values of G and B channels, the CPU adjusts the gain and/or offset of the A/D converter input signal according to the values in the 6 registers until the maximum value of each channel signal is the maximum standard , the minimum value is the minimum standard. The maximum standard in this embodiment is FFH, that is, white with the highest brightness, which means that the minimum standard is 00H, that is, black with the lowest brightness. The amplifier is an adjustable gain amplifier.

The "maximum standard" and "minimum standard" mentioned in the present invention are for the final display effect. For an 8-bit memory, the ideal maximum standard is FF, and the minimum standard is 00. As for the value close to FFH or 00H, although its value is not 00H and FFH, it is still based on the idea of the present invention, and the display effect is the same as that of the present invention, and also belongs to the scope of the present invention. Similarly, for a memory based on the idea of the present invention but using other bit numbers, for example, a 16-bit memory, the maximum standard is FFFFH, and the minimum standard is 0000H, which is also within the scope of the present invention.

Claims (9)

1, automatic color temperature adjusting method is characterized in that, may further comprise the steps:

1) gain with A/D converter R, G, B passage is set to fixed value;

2) regulate the skew of R, G, B passage, all just equal its standard up to the value of one group of register of R, G, B;

3) regulate the gain of R, G, B passage, all just equal its standard up to value of another group register of R, G, B;

4) R, G, the yield value of B passage, the deviant after will regulating writes EEPROM.

R, G, B-register are divided into two groups, are respectively 3 maximum value register of 3 minimum value register of R, G, B and R, G, B;

The standard of the value of minimum value register is that simulation R, G, B are transformed to the minimum sandards of the black level value of digital R, G, B through A/D;

The standard of the value of maximum value register is that simulation R, G, B are transformed to the maximum standard of the white level value of digital R, G, B through A/D.

2, automatic color temperature adjusting method as claimed in claim 1 is characterized in that, the maximum standard of described digital R, G, B is FFH, and the minimum sandards of digital R, G, B is 00H.

3, automatic color temperature adjusting method as claimed in claim 2 is characterized in that step

2) concrete steps are:

A) skew with A/D converter R, G, B passage is set to minimum value;

B) progressively increase R, G, B channel offset value respectively, monitor 3 minimum value register values simultaneously, just equaling 00H to some register values then no longer increases corresponding skew; Continuing increases other deviant, all just equals 00H up to 3 register values.

4, automatic color temperature adjusting method as claimed in claim 3 is characterized in that, adopts stepping or reducing-pitch thread to increase skew.

5, automatic color temperature adjusting method as claimed in claim 2 is characterized in that step

3) concrete steps are:

C) gain with A/D converter R, G, B passage is set to maximum FFH;

D) progressively reduce R, G, B channel gain value respectively, monitor 3 maximum value register values simultaneously, just equal FF to some register values and then no longer reduce corresponding gain; Continue to reduce other yield value, all just equal FFH up to 3 register values.

6, automatic color temperature adjusting method as claimed in claim 5, tool are characterised in that, adopt stepping or reducing-pitch thread to reduce gain.

7, as any described automatic color temperature adjusting method of claim 1 to 6, it is characterized in that described fixed value is a median.

8, automatic color temperature regulator is characterized in that, comprises a CPU, amplifier, A/D converter and 6 registers, and analog signal is through amplifier input A/D converter, and the output of A/D converter feeds back to amplifier through CPU;

Described 6 registers write down the maximum value register and the minimum value register of R, G, B passage respectively;

Described amplifier is used to regulate the skew and the gain of R, G, B passage;

Described CPU is according to the numerical value in described 6 registers, resonance-amplifier.

9, automatic color temperature regulator as claimed in claim 8 is characterized in that, described amplifier is a variable gain amplifier.