JPH03217176A - Light control circuit for video camera with built-in vtr - Google Patents

Abstract

PURPOSE:To prevent hunting without fail when light is turned on/off by providing a light quantity detecting means in addition to a solid-state image pickup element, turning the light on by one output and turning the light off by the other output. CONSTITUTION:The output of a white balance sensor 7 is synthesized by an adder 8, further amplified by an amplifier 9 and supplied to a light control circuit 10 afterwards. The output of a solid-state image pickup element 3 is sampled/held, further AGC amplified and supplied to the light control circuit 10 afterwards. The light control circuit 10 executes control so as to turn light L on based on the output of the above-mentioned amplifier 9 and to turn the light L off based on the output of an AGC circuit 6. Since the light can be controlled to be turned on/off by a histresis loop while using the two light quantity detecting means, the hunting can be prevented without fail differently from the conventional use of the same input signal (the output of AGC).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a VTR-type video camera that incorporates a light for illuminating an image pickup body when it is dark, a video camera, and a VTR.

[Prior art] Conventionally, a small integrated video camera (hereinafter referred to as an OC using a video camera circuit) is a compact integrated video camera that integrates a light, a video camera, and a VTR.
Since the gain can be adjusted even if the output level of T is a little low, it is possible to take images even in a certain degree of darkness. However, the only way to get a satisfactory image in a dark place is to turn on the light. In general, there are two ways to turn on a light: (1) attach a switch to the outside of the light and turn it on manually when the light becomes low, and (2) detect the brightness level of the video signal inside the camera and turn on the light. One method is to create a signal and use this signal to turn on the light.

[Problems to be Solved by the Invention] However, when the above manual light switch is used to turn on the light, there are the following problems.

That is, it is necessary to manually turn on the light when it gets dark and turn it off when it becomes bright, which not only makes the operation cumbersome, but also makes it difficult to determine whether the illuminance is at an appropriate level to turn on the light. Also, when it gets bright (when it's not needed), it's easy to forget to turn off the switch, and in this case, the battery drains quickly.

The above method (2) improves the manual disadvantage of the above (1). According to this method, the light can be turned on and off automatically using the image signal inside the camera. This eliminates the inconvenience of manually turning on and off the light. However, in this case, since the amount of light incident on the lens is used, there is a drawback that hunting is likely to occur when the light is turned on and off.

The present invention has been made in view of the above problems, and is a VT that can prevent hunting that occurs when a light is automatically turned on and off using an image signal inside a camera.
An object of the present invention is to provide a light control circuit for an R-integrated video camera.

[Means for Solving the Problems] In order to achieve the above object, a light control circuit for a VTR-integrated video camera according to the present invention provides a VT incorporating a light for illuminating an image pickup body when it is dark, a video camera, and a VTR.
The R-integrated video camera includes a light amount detection means for detecting the amount of incident light, a detection output of the light amount detection means and an output of a solid-state image sensor as inputs, and turns off the light according to an input signal of either one. The present invention is characterized in that it has a light control means for turning on the light in response to one of the other input signals.

[Operation of the Invention] According to the present invention having the above configuration, the amount of incident light is detected by the light amount detection means, and the detection output is given to the light control means. Further, the output of the CCD image sensor is also input to the light control means, and the light control means turns off the light according to the level of the output of the light amount detection means or the output of the solid-state image sensor. Further, the light is turned on in accordance with the input level of the other of the output of the solid-state image sensor or the output of the light amount detection means. That is, when one of the signals is used to turn off the light, the other input signal is used to turn on the light, and by using different input signals, it is possible to prevent hunting when the light is turned on and off.

[Embodiments] Hereinafter, a light control circuit for a video camera according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

Referring to the figure, the parts related to light control are an iris blade 1, a lens 2, a solid-state image sensor 3, a sample hold circuit 4, an iris control circuit 5, an AGC circuit 6, a white balance sensor 7, an adder 8, and an amplifier. 9, a light control circuit 10, and a light L; a luminance signal processing section 11, a chroma signal processing section 12, an encoder circuit 13, a logarithmic amplifier 14, and a differential amplifier 15 are parts related to signal processing of the camera.

Incident light is restricted by the iris blades 1 and is input to the solid-state image sensor 3 through the lens 2. The solid-state image sensor 3 is C
It has hundreds of thousands of photosensors made of CDs, MOS, etc., and the photosensor 5 converts the light incident through the lens 2 into an electrical signal, which is then supplied to the sampling and holding circuit 4. The sampling and holding circuit 4 samples and holds the output of the solid-state image sensor 3 pixel by pixel, and supplies it to the iris control circuit 5 and the AGC circuit 6. The iris controller 5 drives the iris blade 1 according to the output of the sampling hold circuit 4. The iris blade 1 is automatically adjusted by the controller 5, and when the amount of incident light is large, the aperture is reduced, and when the amount of incident light is small, the aperture is expanded. A that receives the output of the sampling hold circuit 4
The GC circuit 6 automatically adjusts the gain of the luminance signal and carrier signal according to the luminance signal level. This AGC output is supplied to a luminance signal processing section 11, a chroma signal processing section 12, and a light control circuit 10. The luminance signal processing unit 11 that receives the AGC output performs γ correction on the AGC output, and further generates a luminance signal through a low-pass filter and supplies it to the encoder circuit 13. Further, the chroma signal processing section 12 that receives the AGC output performs color separation, one horizontal six pulse delay, synchronization, auto white balance control, matrix calculation, etc. to generate a chroma signal and supplies it to the encoder circuit 13. Note that this chroma signal processing section 12 receives a white balance control signal 1ogB, which will be described later.
/G, IogB/G are input. The chroma signal processing unit 12 thereby automatically controls the white balance, further performs matrix calculation, and generates the chroma signal (R-Y
, B-Y).

The white balance sensor 7 consists of diodes R, G, and B for respectively detecting the amount of red, green, and blue light from among the light incident through a white diffuser plate (not shown), and the outputs of each diode are added together. 8 and a logarithmic amplifier 14. The output of the adder 8 is amplified by an amplifier 9 and then supplied to a write controller circuit 10. The logarithmic amplifier 14 includes a diode R,
The outputs of G and B are expressed as logarithms (logR, logG, log
B), and these respective values are supplied to the differential amplifier 15. The differential amplifier 15 has IogG and 10g, respectively.
The difference with R and the difference between IogG and IogB are taken and amplified, and these are supplied to the chroma signal processing section 12 described above. That is, instead of using the photoelectric conversion output of the white balance sensor 7 as it is, the amount of change is detected only based on the change in the spectral characteristics of the light source, and this is supplied to the chroma signal processing section 12 as a white balance control amount.

Here, to summarize the light control system, the outputs of the white balance sensor 7 are combined by an adder 8, further amplified by an amplifier 9, and then supplied to a light control circuit 10. Further, the output of the solid-state image sensor 3 is sampled and held, further AGC amplified, and then supplied to the write control circuit 10. The light control circuit 10 controls the light L based on the output of the amplifier 9.
The light L is turned on, and the light L is controlled to be turned off based on the output of the AGC circuit 6.

FIG. 2 is a circuit diagram of the write control circuit 10. Referring to the figure, terminal A is connected to amplifier 9, and terminal B is connected to AGC circuit 6. R1 and C1 integrate the output of the amplifier 9, and R2 and C2 integrate the output of the AGC circuit 6. R3, R4, and R5 divide the DC voltage and set the comparator ■C1, IC2 threshold level as
, bs (where bs>as). The threshold level aS is set so that when the output level of the amplifier 9 becomes below a certain value, the output of the IC1 becomes "H" level. Also, the threshold level bs is
The output of IC2 is set to be "L" when the level of C circuit 6 exceeds a certain value (see FIG. 3). R
8, C3 is a time constant circuit that holds the output of IC1 for a predetermined period of time.

Further, D1 is a diode for discharging the charge of C3 when it is turned off, and Q2 and Q3 are transistors that drive the transistor Q1 for lighting the light.

Next, the operation of the write control section having the above configuration will be explained based on FIG. 3. Note that FIG. 3 is a graph in which the vertical axis represents the output level of the amplifier 9 and the AGC circuit 6, and the horizontal axis represents the illuminance, and a timing chart showing the output timings of the ICI and IC2.

In the figure, a indicates the output level of the amplifier 9, and b indicates the output level of the AGC circuit 6. A solid line indicates a transition from a bright state to a dark state, and a broken line indicates a state from a dark state to a bright state. now,
The hunting prevention operation when the bright state becomes dark and then becomes bright again will be explained.

First, when it becomes dark from a bright state, the AGC circuit 6
The output level b1 of the amplifier 9 and the output level a of the amplifier 9 both decrease. The output level b of the AGC circuit 6 first becomes below the threshold level bs, the IC2 goes to the "H" level, and the Q3 turns on.

However, the output level of the amplifier 9 is still below the threshold level as, and the output of the ICI is at the "L" level. Therefore, Q1 is OFF, and the light L is off (the part marked ■ in the figure).

Furthermore, when the amount of incident light decreases and the output level a of the amplifier 9 becomes below the threshold level a$, the output of IC1 becomes "H" level, Q2 turns ON10, Q1 is driven by Q2Q3, and light L lights up. (Part marked ■ in the figure).

Next, when the light L is turned on and becomes brighter, the amount of incident light increases, and the outputs of the AGC circuit 6 and amplifier 9 both increase (
When the output level b of the AGC exceeds the threshold level bs, the output level of the IC2 becomes "L" level, and Q3 is turned off. In response to this, Q1 is turned off and the light L is turned off, so that the outputs of the AGC circuit 6 and amplifier 9 are reduced (the part marked ■ in the figure).

As described above, by using the two light intensity detection means, it is possible to control the turning on and off of the light with the hysteresis loop of ■→■→■→■. Unlike using the output), it is possible to reliably prevent hunting.

Note that the light amount detection level can be made higher than the output level of the AGC circuit 6 by increasing the amplification degree of the amplifier 9. In that case, the light L is turned off based on the output level of the amplifier 9, and the AGC circuit 6 is turned off based on the output level of the amplifier 9. The light is turned on based on the output level of the circuit 116.

Further, instead of the white balance sensor 7, a photo sensor may be used as the light amount detection means.

Furthermore, in place of the output of the AGC circuit 6, the output of the sample and hold circuit 4 can be used as a light amount detection output, and various other design changes can be made without changing the gist of the invention. be.

[Effects of the Invention] According to the present invention, the light amount detection means is provided outside the solid-state image sensor, and one output turns on the light and the other output turns off the light. Hunting can be reliably prevented when the light is turned on or off by using the level difference between the output of the solid-state image sensor and the output of the solid-state image sensor.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram of a write control circuit, and FIG. 3 is an input/output characteristic diagram for explaining the operation of the write control circuit. 12 In the figure, 3 is a solid-state image sensor, 4 is a sampling hold circuit, 6 is an AGC circuit, 7 is a white balance sensor, 8 is an adder, 9 is an amplifier, and 10 is a light control circuit. 13

Claims (1)

[Claims] A light that irradiates an image pickup object when it is dark, a video camera,
In a VTR-integrated video camera incorporating a VTR, a light amount detection means for detecting the amount of incident light, a detection output of this light amount detection means, and an output of a solid-state image sensor are input, and the light is turned on according to the input signal of either one. 1. A light control circuit for a VTR-integrated video camera, comprising a light control means for turning off the light and turning on the light according to an input signal of the other.