JP3015132B2 - Automatic white balance tracking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TTL color difference integration type white balance automatic tracking apparatus for automatically adjusting the white balance of a color video camera in response to a change in color temperature.

[0002]

2. Description of the Related Art FIG. 5 shows the configuration of a conventional white balance automatic tracking apparatus of this type. 1 is a solid-state imaging device, and 2 is a luminance signal processing circuit. Reference numerals 3 and 4 denote integrators, which produce color difference signals through a color difference signal creation circuit 5, modulate them with a carrier modulator 6, and multiplex them with a luminance signal from a luminance signal processing circuit 2 by an adder 7 to produce a composite image. Output as a signal.

On the other hand, two color difference signals RY and BY from the color difference signal generation circuit 5 are supplied to a low-pass filter (LP
F) Averaged through 8, 9 and 2 in comparators 10, 11
The signal is converted into a value signal and input to the microcomputer 12. In the microcomputer 12, output data is controlled by software processing, and after being converted into an analog signal by the D / A converter 13, the analog amplifiers 14, 15
To control the gain of the integrators 3 and 4 to adjust the white balance.

FIG. 6 shows an example of software installed in the microcomputer 12. When the gain of the integrators 3 and 4 is increased and the average value of the color difference signals RY and BY rises above the reference value, the outputs of the comparators 10 and 11 become "H". Now, when the average value of the color difference signal RY from the color difference signal generation circuit 5 is larger than the reference value of the comparator 11 and the comparator 11 outputs “H”, the microcomputer 12 sets the output data to −1. Control to decrease the gain. The average value of the color difference signal RY is smaller than the reference value of the comparator 11, and the comparator 11 outputs "L".
Is output, the output data is set to +1 to control the gain to be increased. In this way, the gain is adjusted for the color difference signal RY, and the gain is similarly adjusted for the color difference signal BY to automatically adjust the white balance.

[0005]

However, since the above-mentioned conventional automatic white balance tracking device always follows the automatic white balance tracking device, even after reaching the optimum white balance state,
Since the following operation is performed to maintain the optimum point, there is a problem that the white balance vibrates above and below the optimum point and becomes unstable.

The present invention is to solve such a conventional problem. After the white balance reaches an optimum point, the white balance can be maintained in a completely stopped state and a stable operation can be performed. It is intended to provide a device.

[0007]

According to the present invention, in order to attain the above object, after a color temperature tracking is completed, a vibration exceeding a certain level is detected and the tracking operation is stopped, so that a change in the color temperature is detected. Unless otherwise, fixed data is output to the integrator for white balance adjustment to maintain a stable state. Further, when the change of the color temperature is detected after the stop of the following, the following operation is started again.

[0008]

[Action] After integrating the color difference signals with a filter and averaging them,
The value is compared with a reference potential by a comparator and input to the microcomputer as a binary output. This input is made for two systems of RY signal and BY signal.
Based on the value information, the gain of the white balance adjustment integrator that is currently being output is increased or decreased by the parameter constant for determining the level of the color temperature to determine the gain, and this is repeated to optimize the white balance. Get closer.

When the integrator gain is near the proper state, the average value of the color difference signal fluctuates around the reference potential, and the output of the comparator keeps reversing little by little. In the conventional device, since this state is set as the follow-up completion state, the white balance constantly vibrates. On the other hand, according to the present invention, the tracking operation is stopped when both of the comparator outputs of the two systems repeat the inversion more than a certain number of times. Therefore, once the tracking is completed, a completely stable state can be maintained. .

After the following operation is stopped in this way, when the color temperature changes, it is necessary to start the following operation again. The detection of the state in which the color temperature has changed is also performed based on the output state of the two comparators. That is, when the output of the comparator is observed in the time of one vertical cycle, the filter characteristic for averaging is related, but when the white balance is matched, the state of the comparator output always changes in one vertical cycle. ing.

Therefore, in the present invention, the comparator output information before one vertical cycle is maintained, the same comparator output information is fetched at two points at the head and the middle point during the next one vertical cycle, and the change in the polarity is observed. Is used to determine a change in color temperature. That is, if the polarity changes at any one of the two points in the next cycle with respect to the information before one vertical cycle, it is determined that the color temperature has not changed, the stop state is continued, and the change is made at two points. When the color temperature has changed for a certain vertical period or longer and the two systems have not changed, the tracking operation is started again.

[0012] In this manner, by continuously repeating the stop operation and the restart operation, stable automatic color temperature tracking becomes possible when the tracking is completed.

[0013]

FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a solid-state imaging device using a complementary color filter. The output of the solid-state imaging device is subjected to gain and gamma correction by an AGC / γ correction circuit 12, and then converted to a digital signal by an A / D converter 13 for digital processing. And
Separate the luminance signal and the color difference signal. Of these, the luminance signal enters the luminance signal processor 14 and the color difference signal passes through the white balance correcting integrators 15 and 16 and enters the color difference signal creation circuit 17 where the color difference signals RY and BY are created. You. The color difference signal from the color difference signal generation circuit 17 is D / A
After being converted into an analog color difference signal by the converter 18 and modulated by the carrier modulator 19, it is mixed with the luminance signal from the luminance signal processing circuit 14 by the adder 20 and output as a composite video signal.

On the other hand, the color difference signals RY and BY output from the D / A converter 18 are supplied to a low-pass filter (LP
F) Averaged by 21 and 22 and input to the microcomputer 25 as binary information by the comparators 23 and 24. Then, the data is processed inside the microcomputer 25 and gain data for the integrators 15 and 16 is output.

Next, an example of internal processing in the microcomputer 25 will be described with reference to FIGS. FIG. 4 shows the comparator outputs and their fetch timings. The outputs of the comparators 23 and 24 are fetched as the first input data and the second input data at the beginning and middle of one field. Follow-up operation and stop operation of the white balance according to the flow of (1).

In FIG. 2, steps 31 to 39 are tracking restart processing, and steps 40 to 46 are tracking operation stop processing. Steps 47 to 49 and 51 to 53 in FIG. 3 are processes for operating the parameters T _R and T _B for calculating the gains of the white balance adjustment integrators 15 and 16.
Processes 54 and 55 calculate and output the gain using the parameters.

In the conventional white balance tracking operation, the parameters are constantly changing at the convergence point of the white balance. In this embodiment, the following operation stop processing from step 40 to 46, first, the parameters T _R, T
_{When the} amount i for changing _B is not zero but one (step 3
1, 40), for the color difference signal RY, the parameter T _R is obtained by looking at the first binary information taken in at the head of one field.
It is determined whether or not RY is inverted (step 41).
One is added to the value Rn of the signal counter register (step 42), and then the parameter T is set for the color difference signal BY.
It is determined whether _B is inverted (step 43),
If it is inverted, B-
One is added to the value Bn of the counter register for the Y signal (step 44). Then, when such inversion continues eight times or more for each field (step 45), it is determined that convergence has been completed, the parameter increase / decrease amount i is set to zero, the operation is stopped, and a stable state is maintained (step 46).

When the color temperature changes from such a stable state, a follow-up restart process from steps 31 to 39 is performed. In this process, the binary information of the first input data and the binary information of the second input data shown in FIG. 4 are used. That is, in a state where the white balance is matched as in the comparator output of FIG. 4, the color difference signals are near the upper and lower sides of the reference voltage of the comparator input, so that the outputs of the comparators 23 and 24 are approximately within one field. The output is inverted in small increments and becomes a pulse output. Conversely, when the white balance is not matched, the outputs of the comparators 23 and 24 always output a constant value.

Therefore, in the following restart process, first, when the following operation is stopped in which the parameter increase / decrease amount i is zero (step 31), the color difference signal RY is set to the first in each field.
It is determined whether the input data and the second input data are the same as the previous data one field before (steps 32 and 33). Only when the input data is the same as the previous data, the counter for the RY signal in the microcomputer 25. One is added to the value Rn of the register (step 34). Color difference signal B-
Similarly, Y is compared with the previous data (steps 35 and 36), and only when it is the same as the previous data, 1 is added to the value Bn of the BY signal counter register Bn in the microcomputer 25 (step 37). . In this way, when the same state as the previous data continues for more than 32 vertical cycles for both the RY signal and the BY signal (step 3).
8) For the first time, it is determined that the color temperature has changed, and the parameter increase / decrease amount i is set to 1 and restarted (step 39), and the processing shifts to the following operation stop processing of steps 40 to 46.

Next, in the processing of steps 47 to 55 in FIG. 3, the direction of increase or decrease of the parameters T _R and T _B is determined based on the first input data at the head of the field. The operation is the same as the conventional flow shown in FIG.
The parameter increase / decrease i is zero when the operation is stopped, and is 1 during normal operation. And if the case the first input data is larger than the reference value, the parameter T _R, increment or decrement i is reduced to T _B, smaller than the reference value, the parameter T _R, T
_The increase / decrease amount i is added to _B.

Next, steps 50 and 54, 55 are applied to the parameters T _R and T _B determined in this way.
, The gains of the white balance integrators 15 and 16 and the color difference gain for color temperature correction for color reproduction are calculated and output, and the integrators 15 and 16 are controlled.

As described above, according to the above-described embodiment, the state in which the white balance has been completely followed is detected and completely stopped by the processing of steps 40 to 46 in FIG. 2, so that the stable following completion state can be maintained. it can. In addition, the tracking is automatically restarted by the processes of steps 31 to 39 in FIG. 2, so that the automatic color temperature tracking becomes possible.

[0023]

According to the present invention, as is apparent from the above embodiment, the state in which the tracking of the white balance is completed is detected, the output data is fixed, and the operation is completely stopped. Can be kept in condition. In addition, since the restart is not performed unless the color temperature is completely changed, the set state is not disturbed by a slight change of the subject or the like. Further, since the vehicle completely stops in the following state, it is possible to converge at the maximum speed.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a white balance automatic tracking device according to an embodiment of the present invention.

FIG. 2 is a flowchart of a follow-up restart process and a follow-up operation stop process operation in the embodiment.

FIG. 3 is a flowchart of a gain calculation processing operation in the embodiment.

FIG. 4 is a timing chart showing comparator output fetch timing in the embodiment.

FIG. 5 is a schematic block diagram of a conventional automatic white balance tracking device.

FIG. 6 is a flowchart showing a processing operation of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Solid-state image sensor 12 AGC / gamma correction circuit 13 A / D converter 14 Luminance signal processing circuit 15, 16 Integrator for white balance adjustment 17 Color difference signal creation circuit 18 D / A converter 19 Carrier modulator 20 Adder 21 , 22 Low-pass filter (LPF) 23, 24 Comparator 25 Microcomputer

Claims (1)

(57) [Claims] 1. An integrator for white balance adjustment, a filter for averaging a color difference signal output from the integrator, and a comparator for converting a signal from the filter into a binary signal, respectively. 2 for -Y and BY signals
System comprising a microcomputer for outputting data to input the output from each comparator controls the gain of the white balance adjustment integrator is, one vertical of the two systems
For the output information from the comparator before the cycle, the next vertical
If the polarity changes at any of the two points in the period
The color temperature has not changed and stops following the color temperature
Perform the operation, none of the two points change, and
A state in which the two systems do not change continues for a certain vertical cycle or more
An automatic white balance tracking device, comprising means for determining that the color temperature has changed when the color temperature has changed and performing a restart operation.