JPH01309491A - Video camera - Google Patents

Abstract

PURPOSE:To reduce the current consumption of a detection section and to reduce malfunction of white balance by operating a color temperature detection section at a prescribed time interval, giving the result to an integration circuit comprising a static capacitance and a resistance and storing the charge to the capacitor. CONSTITUTION:The integration circuit 10 consists of a resistor and a capacitor, and an intermittent circuit 11 switches the resistor connecting between a color temperature detection section 5 and the integration circuit 10 into a high resistance and a low resistance. A system control circuit inputs a brightness component signal S14 from a pickup section 1, outputs signals S12, S13 to switch the resistance of the intermittent circuit 11 into a low resistance at the operation of the color signal detection section 5 and into a high resistance when the section 5 is paused. Moreover, when the illuminance of the light incident to the pickup section 15 comparatively low, the ratio T1/T2 is small and when the illuminance of the light incident to the pickup section is comparatively high, the ratio T1/T2 is increased, where T1 is an effective time of one operation of the color temperature detection section 5 and T2 is the effective time of one pause.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color video camera having an automatic white balance adjustment device.

[Prior Art] Generally, when shooting a color video camera, red and blue are used so that a white subject is reproduced as white.
It is necessary to balance the ratio of each green color signal by adjusting it. Since color reproducibility changes depending on the color temperature of bright light and outside light, white balance adjustment is important in order to obtain accurate colors. However, this adjustment is extremely troublesome and troublesome.

Conventionally, in order to eliminate this hassle, video cameras have been proposed that are equipped with a device that automatically adjusts white balance. FIG. 2 is a block diagram of a conventional video camera. 1 includes an optical system and an imaging system, and R signal S,...
G signal S2. An imaging unit that outputs a B signal S3, 2 a gain control circuit that adjusts the gain of the R signal, 3 a gain control circuit that adjusts the gain of the B signal, and 4 an R' signal S whose gain has been adjusted.
4. The encoder section 5 receives the G signal S2 and the gain-adjusted B' signal S5 and outputs a video composite signal such as an NTSC signal, and detects the color temperature of the subject and the surrounding light. This is a color temperature detection section that outputs an S6 signal indicating a value. Reference numeral 6 denotes a buffer through which a current sufficient to control the gain of the gain control circuit 2 can flow.

7 is an inverting buffer which logically inverts the signal 86 and outputs S8 which controls the gain control circuit 3. The operation will be explained below. White balance needs to be adjusted so that the signal levels of S4, 82, and 35 are equal when the imaging unit photographs a white subject. The color temperature detection section senses the surrounding light, and when the color temperature is low, that is, the light has a large red component, the s6 signal outputs a value close to the 10-'' logic level. In this case, 8° is similarly a value close to the logic level "low" level (hereinafter, logic level "low" will be simply written as "low", and logic level "high" will be simply written as [high J). The gain control circuit 2 works to lower the gain. S8 becomes a value close to the high level, and the gain control circuit 3 moves in the direction of increasing the gain. vice versa,
In the case of light with a high color temperature, that is, with a large amount of blue component, the 36 signal outputs a value close to the "high" level.

In this case, S7 similarly has a value close to the "high" level,
The gain control circuit 2 works to increase the gain. S8 has a value close to the "low" level, and the gain control circuit 3 works to lower the gain. Here, S6. S,, S6 explained the signal level in terms of logic level, but this is only used as a term for explanation, and does not mean that it takes a logical value, but the color of light from "high" to "low". Takes continuous values corresponding to temperature. As described above, when the red component of the light components is large, the gain of Sl is lowered and the gain of S3 is increased. When there are many blue components, the gain of Sl is increased and the gain of S3 is decreased. In this way, the white balance is adjusted so that the levels of the R, B, and G signals are approximately the same. Variable resistors 8 and 9 are used to adjust the gains of gain control circuits 2 and 3 independently from 87 and 58 so that the white balance of the entire system is accurately performed. The light sensing section of the color temperature detection section is generally configured by combining an element sensitive to light with a low color temperature and an element sensitive to light with a high color temperature.

[Problems to be Solved by the Invention] However, in this device, if the light sensing part of the color temperature detection part is accidentally pressed down with the hand and the light is cut off, the gain of the gain control circuit is not adjusted properly. This has the drawback that accurate white balance cannot be achieved. Conversely, if abnormal light enters only the light sensing part of the color temperature detection part,
Similarly, accurate powai [balance] cannot be achieved. Furthermore, since the color temperature detection section operates continuously, it consumes a large amount of current.
As a portable device, this is a major drawback since the battery life is shortened. Further, at low striking power, the sensitivity of the color temperature detecting section decreases and the white balance error increases.

SUMMARY OF THE INVENTION Therefore, the present invention provides a color video camera with an automatic white balance device that eliminates the above-mentioned drawbacks, allows accurate white balance adjustment at all times even during shooting, and minimizes the current consumption required for color temperature detection. It is intended to.

[Means for Solving the Problems] A video camera of the present invention includes at least an imaging section that converts light into an electrical signal, an optical section that guides the light to the imaging section, and a color temperature of the light of the subject and its surroundings. The output signal of the color temperature detection section is input to the circuit section via an integrating circuit composed of at least a capacitance and a resistance, and the pre-color temperature detection section C' is preliminarily set. The connection resistance between the color temperature detection section and the integrating circuit is a relatively low resistance when the color temperature detection section is in operation, and the color (blackness detection section) is repeatedly operated and paused at time intervals. When at rest, it is configured to have a relatively high resistance, and if T1 is the effective time of one operation of the color temperature detection section and T2 is the effective time of one pause, then the light incident on the imaging section is When the illuminance of the light incident on the imaging section is relatively low, T, /T2 becomes small, and when the illuminance of the light incident on the imaging section is relatively high, T, /T2 becomes large. shall be.

[Function] According to the above configuration of the present invention, since the color temperature detection section is operated at certain time intervals, the current consumption of the color temperature detection section becomes extremely small. When the color temperature detection section is in operation, the signal from the color temperature detection section is input to an integrating circuit composed of a capacitance and a resistor, and charges are accumulated in the capacitance. Also,
When the color temperature detecting section is at rest, the connection resistance between the color temperature detecting section and the integrating circuit becomes high resistance, so the charge of the capacitance is accumulated as is. In other words, the charge of the capacitance stores the output of the color temperature detection section as it is, and a sample bold circuit can be realized. Further, by appropriately selecting the operation interval and operation time of the color temperature detection circuit, it is possible to realize a camera that is accurate and has fewer white balance malfunctions. Even if abnormal light enters the color temperature detection unit, if the operating time for each operation is shortened, the change in the amount of charge on the capacitance will be small; This means that white balance malfunctions will not occur. Therefore, it can be said that the video camera according to the present invention is very resistant to noise caused by light. Furthermore, in this invention, the ratio of the effective time of operation and pause of the color temperature detection unit is controlled depending on the illuminance of the subject. In swamp conditions, the rate of operation is reduced, reducing errors in the color temperature detection section in low illuminance.

[Embodiment] FIG. 1 is a block diagram of an embodiment of the present invention, which explains the operation of point balance adjustment of a video camera. 10 is an integrating circuit composed of a resistor and a capacitance; 11 is an intermittent circuit that switches the connection resistance between the color temperature detection section 5 and the integrating circuit 10 between low resistance and high resistance;
Reference numeral 2 denotes a system control circuit that controls the operation and suspension of the balance adjustment circuit. Numbers 1-9 and 81-S8
The explanation of the symbols is exactly the same as in the conventional example shown in FIG.

The system control circuit uses the luminance component signal 514 from the imaging unit 1.
is input, the signals S12 and 313 are outputted, and the operation and pause of the color temperature detection section 5 and the high resistance and low resistance of the intermittent circuit 11 are controlled. 3 is a timing chart of the signals of each part in FIG. 1, and FIG. 4 is a circuit diagram of the intermittent circuit 11 and the integration circuit 10. Fig. 3 Glue, D2. D3. D, and D5 are 8.
. Indicates that the output impedance of the signal increases,
Ml, M2. M, and M4 represent that the output impedance of the S to signal becomes high, and Ml, M2, M3, and M4 represent S. The output impedance of the signal becomes low, indicating that the output of the color temperature detection section 5 is being transmitted. In FIG. 4, 13 is a terminal to which a signal from the system control signal is manually input, 14 is a terminal to which a signal from the color temperature detection section is manually input, and 20 is a terminal to which a signal from the integrating circuit is output.

S9. S, o, S II and 313 are the same as in FIG.

The system control circuit 12 outputs signals S1□ and 313. When S12 becomes "high", a current flows through the color temperature detection section 5, and an operation for detecting the color temperature is performed. When S12 becomes "low", the current is cut off and the operation stops. S13 said “
When the signal SII from the color temperature detection section 5 becomes S, the resistance of the intermittent circuit 11 becomes low. When the signal becomes "low", the intermittent circuit 11 has a high resistance, and the signal from the color temperature detection section 5 is cut off. S1
The "high" section of 3 is completely included in the "high" section of S1□, and the color temperature information in the section where the operation of the color temperature detection unit 5 is unstable at the start and end of its operation is completely included in the "high" section of S1□. Sample characters - Ransista 17 and N Chai, Le MO3I - Ranjisuk]
6 and a NOT circuit 15, and performs high-resistance and low-resistance switching operations. The integrating circuit 10 is composed of a resistor 18 and a capacitor 19, and when the resistance of the 1iJi connection circuit 11 is low, charge is accumulated in the capacitor 19 by the S11 signal, and when the resistance of the intermittent circuit 11 is high, charge is accumulated in the capacitor 19. The charge is held as is. At this time, the buffer circuit 6 connected to the terminal 20
Since the human power impedance of the inverting circuit 7 is set very high, the electric charge of the capacitor 19 is sufficiently high.
be done. The S9 signal thus formed becomes 87 and S8 by the buffer circuit 6 and the inversion circuit 7, and the red signal S
1 and the gain of the green signal S5 are adjusted to achieve white balance.

The above operation is an explanation of the state before t1 in FIG. 3. This difference occurs because the color temperature is in a steady state, so S, , S, and S9
has been maintained at a certain level. For example, in tl.
If you cover the color temperature detection section 5 with your hand or if abnormal light enters, this section is the D3 section, so the color temperature detection section 5 will be in a dormant state, and the color (blackness information will be halted). Therefore, no malfunction will occur.Also, if the same thing occurs at timing t2, the color temperature signal will change from 8.1 to S to This changes the amount of charge in the capacitor 19. This is transmitted to S7 and S8.
, the white balance adjustment status changes.

However, if the time constants of the resistor 18 and capacitor [9] are set large, the amount of change in white balance will be small and there will be no practical problem.

Furthermore, if this time constant is too large, the white balance delay time will increase, so it is important to set the time constant appropriately. In actual usage conditions, color temperature changes are not rapid, so a relatively large time constant is selected.

Next, the system control circuit 12 will be explained in detail.

The system control circuit includes a luminance component signal S from the imaging unit 1.
14 is a manually operated circuit that outputs S12 and 313 which control the entire white balance system. FIG. 5 is a block diagram of the system control circuit 12, and FIG. 6 is a timing chart of signals of each part in FIG. terminal 2
The peak of the S14 signal inputted from S14 is detected by a peak detector 24, and an S19 signal is output. The 519 signal is compared with the S21 signal by a comparator 29 and outputs the S20 signal.

The signal 82 is a signal that determines the comparison level of the comparator 29, and is a signal voltage-divided by the variable resistor 36. In FIG. 6, the signal S 2+ is shown by a broken line. S
The 20 signal becomes 10-'' when S19 is higher than the comparator level, and becomes ``high'' when S19 is lower. On the other hand, the signal from the signal generator 1 is SI5, and the inverted signal is S2□. S2゜S22 is NO
Power is input to the R circuit 30 and outputs S24. S24 becomes 10-'' after S20 is ``high'', and 8□.

When is "low", the signal matches S I5.

S24 and the output signal 316 of the signal generator 2 are connected to the OR circuit 3.
1 and output S12. S1□ is output from the terminal 22. In the manner described above, the S1□ signal is formed. In exactly the same way, the S13 signal is formed and output from terminal 23. Timing chart 1 in Figure 6
The specifics are determined by At the timing of (a), the brightness level is high and the illuminance of the light is high. Therefore, the peak detection signal S4 also has a sufficiently high value. Next, at the timing (b), the brightness level is low, indicating that the illuminance of the light has become low. Therefore, the 319 signal goes low beyond the comparator level S21. At this time, S20 changes from "low 1 to" high.
is reversed. When S20 is 10-”, S1□
was the sum signal of SIG and 318, but when it goes "high", S12 becomes the same signal as 516. Similarly, when S 13 is “low”, S IT
and 518, but when it goes high, S
13 is Sl. It becomes the same signal. As shown in ``2'',
Of the light incident on the imaging unit 1! ] When the temperature is high, the ratio of the effective operating time of the color temperature detection section to the effective resting time increases, and when the illuminance of the light incident on the imaging section 1 is low, the effective operating time of the color 7 blackness detection section increases. ``The ratio of time to time decreases'': controlled.

In this embodiment, the effective operation time and effective pause time of two stages I were controlled, but further control of multiple stages or continuous control is also possible. Moreover, it is also possible to control by changing the effective operation time without changing the effective pause time.

[Effects of the Invention] As described above, according to the present invention, the color temperature detection section repeats operation and rest at preset time intervals, so that the current consumption of the color temperature detection section becomes extremely small. 'Especially in the case of portable video cameras, since they operate on batteries, continuous shooting time can be extended, which is a big advantage.

In addition, since the color temperature detection section of the present invention does not operate continuously, even if abnormal light occasionally enters the color temperature detection section or - light to the color temperature detection section is temporarily interrupted. However, if the color temperature detection section is at rest, the white balance will not change at all. Moreover, even if there is a change, the change is very small because an integrating circuit is used, and the probability of that change is low because of the zumbling operation. Therefore, the white balance of the video camera according to the present invention is highly resistant to noise caused by light size. Furthermore, depending on the brightness of the subject, the ratio of the operating time and rest time of the color temperature detection section is changed to reduce the difference in white balance at low illuminance, achieving good balance even at low illuminance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. FIG. 2 is a block diagram of a conventional video camera. FIG. 3 shows timing diagrams of signals in each part of FIG. 1. Figure 4 is a circuit diagram of an intermittent circuit and an integrating circuit. FIG. 5 is a detailed block diagram of the system control circuit. Figure 6 shows the signal timing diagram i for each part of the 5th ward. tl... Timing t2 of incidence of extraordinary light
Timing of incidence of abnormal light 15 ・NOT circuit 16 ・N channel MO3I-Run Sister 17 ・
・08 transisc 18 between P channels...Resistor 19 ・Capacitor 25 ・-3I! A signal generator 126 that outputs a + signal.
・Signal generator 227 that outputs S16 signal...S
Signal generator 328 that outputs the 17 signal...Signal generator 432 that outputs the 318 signal...NOT circuit 33-NOT circuit 34-NOT circuit 35...OR circuit S23...S Inversion of the logical value of S17 signal S 2
6. More than the inverted signal of the logical value of S13

Claims (1)

[Claims] Consists of at least an imaging section that converts light into an electrical signal, an optical section that guides the light to the imaging section, a color temperature detection section that detects the color temperature of the subject and its surrounding light, and a circuit section that processes the electrical signal. The output signal of the color temperature detection section is input to the circuit section through an integrating circuit composed of at least a capacitance and a resistance, and the color temperature detection section operates and stops at preset time intervals. The connection resistance between the color temperature detection section and the integration circuit is a relatively low resistance when the color temperature detection section is in operation, and a relatively low resistance when the color temperature detection section is inactive. In a video camera configured to have high resistance, if the effective time of one operation of the color temperature detection section is T_1, and the effective time of one pause is T_2, light incident on the imaging section is When the illuminance of is relatively low, T_1/T_2 becomes small,
When the illuminance of the light incident on the imaging section is relatively high,
A video camera characterized in that it is configured such that T_1/T_2 is large.