JPS60253936A - Color camera - Google Patents

Abstract

PURPOSE:To improve deterioration in picture quality due to a flicker of a light source, etc., and to perform high-sensitivity color temperature tracking by comparing the output of a color temperature information detector with the contents of a storage means during blanking periods and obtaining and storing optimum color temperature information. CONSTITUTION:The output of a color temperature-voltage converting circuit 11 is compared with the output of a microcomputer 19 which outputs the contents of a counter means which are obtained one vertical period before through comparators 15 and 16 in vertical blanking periods to decide whether the counter means counts up or down. The contents of a single-time storage means are compared with the contents of the counter means in 32-fold vertical periods. When the output of an external sensor 10 is not normal owing to low illuminance and high brightness, the operation of the counter means is stopped and an optimum gain control voltage is outputted from the computer 19 to R and B gain control circuits 5 and 6 in video period to perform white balance control.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color camera capable of white balance control.

Conventional configuration and problems thereof FIG. 1 shows the configuration of a conventional color camera that detects an external light source. The image converted into an electric signal by the image pickup tube 1 is amplified by a brilliance amplifier 2, and then enters a luminance signal processing circuit 3 and a chroma signal processing circuit 4. The luminance signal processing circuit 3 includes a chroma signal processing circuit 4 that extracts the luminance component from the input video signal.
Now, the YL multiplied signals R signal and B signal are separated from the input video signal.

The R signal and B signal enter an R gain control circuit 5 and a B gain control circuit 6, respectively.

On the other hand, the color temperature information obtained from the external light sensing sensor 10 is converted into voltage by the color temperature information-voltage conversion circuit 11, and R
, B are input to gain control circuits 5 and 6 to take white balance. gain controlled R,
The B signal enters subtracters 7 and 8 and subtracts the YL multiplied signal to produce one color difference signal RYL multiplied signal B-YL multiplied signal. The R-YL multiplied signal B Y+ signal is modulated by a modulator 9, and added together with a synchronization signal generated by a synchronization signal generator 12 and a luminance signal from a luminance signal processing circuit 3 in an adder 13. Adder 1
An NTSCφ signal 14 is obtained at the output of 3.

However, in the above conventional example, the output of the sensor 10 directly controls the R/B gain through the color temperature-voltage conversion circuit 11, so if the output of the sensor 10 fluctuates due to flicker of the light source or various other factors, If the level detection area of the sensor is exceeded, such as high brightness, it will directly affect the R-B gain control and the image quality will deteriorate significantly.

OBJECTS OF THE INVENTION The present invention aims to eliminate the drawbacks of the above-mentioned conventional examples, and to perform white balance control while maintaining a high level of image quality. The output of the color temperature information detector and the contents of the storage means are compared during the blanking period to obtain optimal color temperature information, which is stored, and the gain of each color signal is adjusted during the unblanking period based on the stored contents. It is configured to control the control circuit to perform accurate white balance control, and to limit white balance control when abnormal light is detected.

DESCRIPTION OF THE EMBODIMENT FIG. 2 is a functional block diagram of an embodiment of the present invention. Comparators 15 and 16 are B-channel signals (hereinafter referred to as B-ch) obtained through the color temperature-voltage conversion circuit 11.
, the R channel signal (hereinafter referred to as R-ch) and the counter means (A) converted by the D/A converter 17.18 (A)
′ is compared. Hereinafter, since the processing for R-ch and B-ch is the same, the description will focus on B-ch.

The counter means (a) operates by one change during the vertical blanking period, and the output switching means) stores the contents of the counter means (a) during the vertical blanking period and the contents of the storage means (c) during the video period. Output. Further, the numerical comparison means (e) and the storage content change determination means (b) operate once every 32 times the vertical period. When the vertical blanking period begins, the contents of the counter means (a) are outputted to the output switching means (a). In the comparator 15, the information of the color temperature-voltage conversion circuit 11,
The contents of the counter means (a) converted by the D/A converter 17 are compared, and only the counter means becomes larger, resulting in the new contents of the counter means (a). Before the end of the vertical blanking period, the above operation is completed and the output switching means) outputs the contents of the storage means 0→. After 32 times the vertical period, the contents of the counter means (a) and the contents of the storage means (c) (when the power is turned on, the preset value is stored) are compared by the numerical comparison means (e), and the level is determined. In the difference, (1)
The contents of the counter means (a) are entered into the contents of the storage means (c). (2) Bring the contents of the storage means (c) closer to the contents of the counter means (b) one count at a time. (3) Storage means (
The contents of c) will not be changed. The three judgments are made by the storage content change judgment means (b). The contents of the new storage means (c) are set as B-ch gain control information, and outputted from the output switching means. B-ch, R- during the video period
The gain control voltage of channel is stable because the contents of the storage means (c) (c)' are outputted to the output switching means)'through)'. Further, the high-intensity detection means (c) and the low-intensity detection means (g) detect high-intensity information from the external light sensing sensor 10.

Detects low light information, and if either one is detected, O
Counter stop information is outputted by the R means 4, and the counter means (a) and (a)' stop operating.

When the information from the high-intensity detection means (f) and the low-intensity detection means (g) disappears, the operation of the counter means (a) and (a)' is released. That is, in a region outside the dynamic range of the external light sensing sensor 10, the operation of the counter means (a) and (a)' is stopped to stabilize the gain control voltage.

FIG. 3 is a concrete block diagram of an embodiment of the present invention. In Figure 3, the same parts as Figures 1 and 2 are:
Identical and indicated by code. A microcomputer 19 mainly consists of a memory '20, a microprocessor 21, and an interface 22.

The output terminals 23 and 24 of the external light sensor 10 output high-luminance information and low-illuminance information, respectively. During the vertical blanking period, the output of the color temperature-voltage conversion circuit 11 and the output of the micro converter 17 which outputs the contents of the counter means (A) and (A)' obtained one vertical period ago are set to 7V.
-Tal 5. 16, and it is determined whether the contents of the counter means (a) and (a)' should be incremented or decremented by one. The contents of the storage means (c) (c)' are compared with the contents of the counter means (a) (a)' once every 32 times the vertical period, and the optimal information is always stored in the storage means () → (c)'. When the output of the external light sensor 1o is not normal due to low illuminance and high brightness, the counter means (a) and (a)' are stopped and the optimum gain control voltage is adjusted during the video period. R-E gain from microcomputer 17
It outputs to control circuits 5 and 6 and performs white balance control.

A flowchart of control for outputting the optimum gain control voltage is shown in FIG. Note that 81 to S in the figure indicate each step of the flowchart.

Here, the control is executed once per vertical period.

Let the contents of the counter means (a) be C6, and the contents of the storage means (c) be Me. At Sl, control execution begins;
In S2, it is confirmed whether it is the vertical blanking period.

In S3, it is checked whether the output of the OR means 4 is HIGH upon receiving the high brightness information/low illuminance information. If either information is input and the output of the OR means 4 is HIGH, the process goes to S19 and the present control ends. In S4,
The content C8 of the counter means (a) is output. The comparator 15 compares the output of the color temperature-voltage conversion circuit 11 and the value of C6 voltage-converted by the D/A converter 17, and if the value of Co is larger, the output of the comparator 15 becomes Low.
On the other hand, if the value of co is smaller, the output of the comparator 15 becomes High. In S5, comparator 15
Checking the output of
The value of 6 is subtracted by 1 count. In S8, ■1 is a value for counting 32 times the vertical period, and 3
If twice the vertical period has not elapsed, in S9,
■Add one count to the value of 1 and jump to Sl8. After 32 times the vertical period, the value of Co is compared with the value of the content Me of the storage means (c) at SIO, and the absolute value of the difference between the two is set as A. In step 811, if the value of A is 8 or more, in step S12, the content C6 of the counter means (a) is
is entered in the storage means (c), and the value of Me becomes the value of C8. At 813, if the value of A is less than 4, the value of Co is not changed. In 814, if the value of Co is smaller than the value of Me, the value of Me is subtracted by one count in S15, and if the value of co is larger than the value of Me, 816
1 count is added to the value of Me. That is, if the difference between the value of C6 and the value of Me is less than 8 and 4 or more, the value of Me is brought closer to the value of C8 by one count. In S1□, 32
Clear the value of ■1, which is the double vertical period counter, and
At 18, the output of the micro converter 19 is
The value of o is switched to the value of Me, and the execution ends at S,9.

If the output of the color temperature voltage conversion circuit 11 fluctuates regardless of the color temperature change of the light source due to the above control, the gain
The voltage applied to the control circuits 5 and 6 does not change,
The gain control voltage quickly follows changes in the color temperature of the light source.

If the dynamic range of light reception by the external light sensor 10 is exceeded during image capture under low-intensity or high-intensity lighting, and the sensor information malfunctions, the state before the malfunction will be maintained and the gain control voltage will change. refrain from doing
Limits the white balance from being significantly distorted.

In this embodiment, high-luminance information and low-illuminance information are detected, but the present invention can be achieved by using either one of them depending on the dynamic range of the external light sensing sensor.

Effects of the Invention As described above with reference to embodiments, the present invention can improve image quality instability due to flickering of the light source, change in shooting scene, unexpected sensor blockage, and deterioration of image quality due to incidence of high-brightness light. A color camera that can track color temperature with high precision can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional color camera, FIG. 2 is a functional block diagram of a color camera according to an embodiment of the present invention, FIG. 3 is a block diagram showing the specific configuration of the above embodiment, and FIG. The figure is a flow chart diagram showing the operation of the above embodiment. 5.6. Gain control circuit, 10. External light detection sensor, 13.14... Comparator, 19. Microcomputer. Name of agent: Patent attorney Toshio Nakao (1st person)
figure

Claims (1)

[Claims] A color temperature information detector, a comparator having one input as the output of the detector, a counter means for counting the output of the comparator, a storage means for storing the contents of the counter means, and a combination of the counter means and the storage means. Numerical comparison means for comparing contents; storage content change determination means for determining whether or not the contents of the storage means should be changed to the contents of the counter means based on the comparison results; an output switching means for guiding the contents of the storage means as a control signal to a gain control circuit for each color signal during an unblanking period, and for stopping the counting operation of the counter means when abnormal light is detected; A color camera comprising a detection means.