JPS6123915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic white balance adjustment device for a color television receiver, and an object of the present invention is to provide a device that can automatically and efficiently adjust the white balance of a color television receiver in a manufacturing factory. With the goal.

Conventionally, this type of adjustment was performed manually using five adjustment variable resistors provided in a color television receiver. However, since these variable resistors interact with each other, complete adjustment cannot be made in one go, and even if repeated several times, the result will not be fully satisfactory.The white balance will vary between color television receivers, and the image quality will be affected. There was a problem at this point. The present invention provides a device that can automatically perform such adjustments mechanically, and one embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a color picture tube of a color television receiver, and a highlight light receiving element 2 and a low light receiving element 3 are installed on the front of the color picture tube 1 so that they can each receive raster light. The outputs of the light receiving elements 2 and 3 are applied to the automatic highlight adjustment voltage generation section 4 and the automatic low light adjustment voltage generation section 5, respectively. Both of the above light receiving elements 2 and 3 are R (red), G (green) and B, respectively.
It has a (blue) gelatin filter on the front, and a total of six outputs, three for each color, including highlights and lowlights, are extracted. Both voltage generators 4 and 5 convert the six signals into DC signals and apply them to the motor controller 6.

Since the motor control section 6 has four outputs for motor rotation, these outputs can be used to control the four drivers 12.
The color picture tube 1 is rotated and the four variable resistors 13 connected to the color picture tube 1 are turned for automatic adjustment. When the switch 11 connected to the motor control section 6 is pressed, the motor control section 6 operates and starts rotating the driver 12, and when the adjustment is completed, the adjustment completion lamp display section 7 displays.

On the other hand, the outputs of the two voltage generators 4 and 5 are applied to a brightness controller 8 and applied to an antenna terminal 10 of a color television receiver via an RF modulator 9 to control the brightness of the color picture tube 1. It automatically works to keep it constant.

What is shown in FIG. 2 is the pattern screen of the color picture tube 1, where the upper half is bright and the light receiving element 2 for highlights can receive light, and the lower half is dark so that the light receiving element 3 for low lights can receive light.

FIG. 3 shows details of the voltage generators 4 and 5 for automatic highlight and low light adjustment. Here, only one voltage generating section 4 will be described, but the same applies to the other. Output G of the light receiving element 2,
R and B are amplified by amplifiers 14, 14a, 14b, respectively, and limiter amplifiers 15, 15a, 15.
b, peak hold circuit 16, 16a, 16b,
It is converted into DC by a DC regeneration circuit consisting of sample and hold circuits 17, 17a, 17b and amplifiers 18, 18a, 18b and then sent to meters 19, 19a, 19b.
is applied to In particular, this DC regeneration circuit uses a peak hold circuit and a sample hold circuit instead of an RC integration circuit, so the DC regeneration time can be shortened.

The amplifiers 14, 14a, and 14b amplify the electrical signals of the light receiving elements 2 and 3, and in particular, in the case of low light, amplification is performed by 6000 to 8000 times.
The DC regeneration circuit converts the ripple waveform of the input signal into a complete DC, and its operation will be explained using the waveform diagram in FIG. Amplifier 14, 14a, 1
The output of 4b (FIG. 4A) is sent to the limiter amplifier 15,
15a and 15b form the waveform shown in FIG. 4B. The outputs of the limiter amplifiers 15, 15a, 15b are peak hold circuits 16, 16a, 16b.
is applied to sample and hold circuit 1.
7, 17a, 17b to obtain a reset pulse (C in Fig. 4) and a sample pulse (D in Fig. 4) to obtain a waveform (E in Fig. 4) at the output of the peak hold circuits 16, 16a, 16b. , a DC output (FIG. 4F) corresponding to the input is obtained from the outputs of the sample and hold circuits 17, 17a, and 17b. The output of each sample hold circuit 17, 17a, 17b is sent to the meter 1 via an amplifier 18, 18a, 18b.
Among them, the amplifier 18 amplifies the G output as it is, so the G meter 19 (0 to 100 μA meter) displays the G output as it is, and the amplifiers 18a and 18b amplify the G output as it is.
This is a zero point detection amplifier that obtains the difference between R-G and B-G based on the output, and this difference is displayed by an R meter 19a and a G meter 19b (±50 μA meter). The outputs of the amplifiers 18, 18a, 18b are applied to the motor control section 6.

FIG. 5 shows details of the motor control section 6. G obtained from the highlight automatic adjustment voltage generator 4,
The three outputs RG and BG are applied to a comparator 20 and amplifiers 21 and 21a. If this comparator 20 is for highlighting, the highlight G output is 70±5μ
It prevents the motors 12, 12a from rotating unless the low light G output reaches 50±5 μA, and the output is It is applied to the switch circuits 23 and 23a. 0 above
The outputs of the amplifiers 21 and 21a that improve the point accuracy are those in which the motor stop circuits 22 and 22a output an output to brake the motor and stop it when the outputs of R-G and B-G each become 0. An OV type comparator is used.

The zero point adjustment accuracy is maintained within ±2 μA. 2
3 and 23a apply rotation signals to amplifiers 24 and 24a only when all motor rotation conditions are satisfied.
It is a switch circuit consisting of FET, and the conditions are as follows.
If the G level is constant, it means that BG and RG are not at 0 points and that the switch 11 is closed. The amplifiers 24, 24a are the motors 12, 12a.
The circuit is designed to rotate, and the circuit is simplified by using high-power OPs and ICs instead of using transistors. Furthermore, in order to prevent the variable resistors rotated by the motors 12, 12a from turning too much, a current limiting circuit is also connected to measure the breakdown current of the variable resistors and to prevent any more current from flowing.

When the switch 11 is turned on in this way,
Using G as a reference, screen variable resistors for R and B, and drive variable resistors for R and B.
One is directly rotated by a motor, and when the brightness of R and G becomes equal to the standard brightness of G, the motor stops and the adjustment is completed. This adjustment was completed in about 1 second after the switch 11 was turned on, resulting in a significant improvement in efficiency.

FIG. 7 shows a perspective view of the motor section. The motors 12 and 12a for low lights are drivers 25 and 25.
The low light motors 12b, 12c rotate the drive variable resistors R, B via drivers 25b, 25c. Reference numeral 26 denotes a printed circuit board to which the variable resistor is attached, and is usually provided at the rear of the color picture tube 1.

FIG. 6 shows the brightness control section 8. Brightness control is a white balance adjustment that uses the G level signal from the light receiving element to adjust the bright areas of the screen to, for example, a (NIT) and the dark areas to b (NIT). The brightness of the screen is automatically kept constant. The highlight G level and low light G level obtained from the automatic highlight adjustment voltage generation section 4 and the automatic low light adjustment voltage generation section 5 are the highlight reference brightness setting circuit 27 and the lowlight reference brightness, respectively. It is applied to the setting circuit 27a. Both setting circuit 2
7, 27a is a circuit designed so that when the highlight G output becomes a (NIT) or when the low light G output becomes b (NIT), an output corresponding to the deviation is output at OV. The reference value is set by the reference variable resistors 27b and 27c. The highlight reference modulation bias circuit 28 and the low light reference modulation bias circuit 28a are circuits that determine the degree of modulation of the television signal and determine the brightness.
For example, bright parts of the screen are a%, dark parts are b
% and the degree of modulation is determined in advance. This modulation reference can be set by variable resistors 28b and 28c. The vertical synchronization switch circuit 29 divides the screen of the television receiver into upper and lower halves based on the vertical synchronization signal obtained from the synchronization signal generation circuit 33 of the television receiver, and displays a highlight pattern on the top and a lowlight pattern on the bottom. This is a circuit that allows the images to be displayed. The output of this circuit 29 is amplified by an amplifier 30, and a limiter circuit 31 applies a limiter to prevent the modulation degree from increasing beyond a certain modulation degree when no input signal is input. The mixing circuit 32 mixes the output of the limiter circuit 31 with the horizontal synchronization signal and blanking signal from the synchronization signal generation circuit 33 to create a video signal, and this output is
The signal is modulated by the RF modulator 9 and applied to the antenna terminal 10 of the television receiver, and the white balance adjustment pattern shown in FIG. 2 is projected on the screen. The brightness of this pattern is always kept constant in both the highlight and lowlight areas and is extremely easy to adjust.

As described above, according to the present invention, when adjusting the white balance of a color television receiver, the variable resistors for the screen and the drive are automatically rotated by the motor, and when the balance is achieved, the motor is automatically stopped. This makes it possible to perform work extremely efficiently without relying on human hands.

Furthermore, when adjusting white balance, it is important to always maintain the brightness of bright and dark areas at a predetermined level for accurate adjustment, but according to the present invention, detection from a photoelectric element Since the screen brightness is controlled to a predetermined value using the output, even if the screen brightness changes as the adjustment progresses, that change can be automatically compensated for and remains constant from beginning to end. Accurate automatic adjustment of brightness can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an automatic white balance adjustment device according to an embodiment of the present invention, FIG. 2 is a pattern diagram of a television screen, FIG. 3 is a block diagram of the automatic adjustment voltage generating section of the same device, and FIG. Figure A,
B, C, D, E, F are waveform diagrams of each part in Fig. 3, Fig. 5
This figure is a block diagram of the motor control section of the same device, FIG. 6 is a block diagram of the brightness control section, and FIG. 7 is a perspective view of the main parts of the same device. 1... Color picture tube, 2, 3... Light receiving element, 4
... Highlight automatic adjustment voltage generation section, 5 ... Low light automatic adjustment voltage generation section, 6 ... Motor control section, 8 ... Brightness control section, 9 ... RF modulator.

Claims (1)

[Scope of Claims] 1. Projection means for projecting bright and dark parts on the screen of a color television receiver; A first light-receiving element that outputs an output according to
a second light-receiving element that outputs an output according to the brightness of each color component of B, and R of the first and second light-receiving elements;
The G and B outputs are each converted to DC, and the R, G,
The first voltage generating means for the bright portion and the second voltage generating means for the dark portion extract the difference between the output of one of the colors B as a reference and the output of the other color; A means for rotating a variable resistor for adjusting the white balance of the color picture tube by rotating a motor by the output of the second voltage generating means, and outputting a reference color from the first and second voltage generating means. and brightness control means for controlling the brightness of the bright and dark areas on the screen to a predetermined value based on the output thereof. 2. The brightness control means extracts the reference color output from the first and second voltage generation means, compares this output with a constant level in the first and second reference brightness setting circuits, and sets the constant level. A modulation bias is set using the comparison output, a synchronization signal is superimposed on the obtained signal, and RF modulation is performed to create a television signal for the measurement pattern that has bright and dark areas.The color television receiver to be measured 2. The automatic white balance adjustment device according to claim 1, wherein: