JPH01233969A - Imaging device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an imaging device equipped with an infrared light source for illuminating an object.

(Prior Art) Night vision video cameras and night surveillance cameras equipped with an infrared light source for illumination such as an infrared lamp or an IRED (near infrared light emitting device) have been known. In these imaging devices, For example, when using an inexpensive IRED, a solid-state image sensor that senses near-infrared light is used, and image signals are sequentially read from this solid-state image sensor.

FIG. 6 is a conventional circuit configuration diagram showing the current supply system of the infrared light source. In the figure, 1 is an I R provided as an infrared light source.
In the ED, the anode side is connected to a DC power supply line, and a resistor R1 and a transistor Q are connected in series between the cathode side and ground. A control signal for controlling energization of I RED 1 is applied to the base of transistor Q+ from the outside.

FIGS. 7(a) and 7(b) show the above control signals and I
This shows the amount of light emitted by RED 1. As shown in the figure, the control signal supplied to transistor Q is constant, and IREDI is supplied with a constant continuous current determined by the value of resistor R3. flows. This current is controlled in consideration of the life cycle of I RED 1, and its peak value, that is, I RED 1
The emission peak of the river is limited.

The continuous energization causes the IREDI to emit light continuously to illuminate the subject, thereby making it possible to photograph the subject even in a dark place, such as at night.

[Problem to be solved by the invention]

However, in conventional imaging devices equipped with an infrared light source, since the infrared light source is used for continuous emission as mentioned above, there is a limit to the peak amount of light emission, and there is a problem that there is a limit to the illumination distance. There was a point. For example, in the case of I RED 1, the illumination distance is generally several meters, and it is 20 to 30 meters.
In order to provide illumination, a considerable number of IREDs must be used, resulting in large current consumption and a large device.

The present invention has been made in view of these problems, and provides an imaging device that can have a large emission peak amount of an infrared light source, has a long illumination distance, consumes little current, and can be made smaller. It is something.

[Means to solve the problem]

The imaging device of the present invention is provided with a light emission control device that causes an infrared light source for illuminating a subject to emit light intermittently and changes the peak amount of light emission.

Further, the imaging device of the present invention is configured to be able to vary the period of the intermittent light emission, and is further provided with a memory that stores an imaging signal during the intermittent light emission for each intermittent cycle.

[Effect]

In the imaging device of the present invention, since the infrared light source can emit light intermittently to increase its peak amount, a long illumination distance can be obtained within the allowable range of the infrared light source. In addition, by varying the period of intermittent light emission, it is possible to reduce the applied current when sufficient light quantity necessary for imaging is obtained, and by providing a memory that stores the imaging signal for each intermittent period. , you can see a stable image.

〔Example〕

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. In the figure, 1 is an IRED which is an infrared light source for illuminating the subject.
Then, connect resistor R2 and transistor Q2 to this I RED 1.
A series circuit of resistor R3 and transistor Q3 is connected in parallel. 2 is a light emission control device that causes IR and EDI to emit light intermittently and changes the peak amount of light emission; one transistor Q2 is supplied with a control signal for continuous light emission, and the other transistor Q3 is outputted a control signal for intermittent light emission. do.

FIG. 2 shows the external appearance of a video camera 3 having the above-mentioned circuit configuration, and a lamp hook 4 having an I RED 1 is attached to the top thereof. And I RED
Near-infrared light is emitted from 1 to the subject 5 as shown by the arrow in the figure.
An image of this subject 5 can be obtained through the lens 6. In addition, the rear of the video camera 3 is equipped with an NTS
Output terminal 7 for outputting as a C signal and input terminal 8 for power supply
Although not shown, the video camera 3 is further provided with a solid-state image sensor that senses near-infrared light from the subject 5 and its signal processing circuit.

Next, the operation will be explained.

When a continuous light emission control signal is applied from the light emission control device 2 to the transistor Q2, a continuous current flows through IRED1, and IREDI emits light continuously. Also,
When an intermittent light emission control signal is applied to transistor Q3, an intermittent current flows through IRED1,
I RED 1 emits light intermittently. Here, the resistance values of the resistors R2 and R3 connected to the transistors Q2 and Q3 are different, and the current values are different between the continuous energization and the intermittent energization. That is, the light emission peak amounts of I RED 1 are different from each other, and the light emission peak amount during intermittent light emission is larger than that during continuous light emission.

FIG. 3 is a diagram showing the relationship between each control signal and the light emission peak amount of I RED 1 in the case of continuous light emission and intermittent light emission. As mentioned above, the control signal in the case of continuous light emission (see Fig. 3(b)) is a constant continuous signal (Hl).
The light emission peak amount Ll (see FIG. 3(C)) is also constant.

At this time, the current flowing through I RED 1 is a current determined by resistor R2 in FIG. 1, that is, a current that takes the life of I RED 1 into consideration. On the other hand, in the case of intermittent light emission, a control signal (see Figure 3 (d)) is output in synchronization with a field signal (see Figure 3 (a)), and the I RE
D1 emits light intermittently during the T2 period (see FIG. 3(e)). The light emission peak ffi L2 of IREDl at this time is thicker than the light emission amount during the above continuous light emission (L2 >
Ll >, if one field period is T1, then Tl x
It has the relationship L,=T2xL,2. That is, in the case of intermittent light emission, the light emission peak amount can be increased within the allowable range of I RED 1 compared to the case of continuous light emission,
Therefore, the illumination distance can be made longer than in the case of continuous light emission. At this time, the larger the emission peak firefly is, the longer the period of intermittent light emission of I RED 1 (the interval period from one light emission to the next light emission) will be taken.

Furthermore, since the current consumption is not as large as in the case of continuous light emission, the device does not become large.

Furthermore, when emitting light every several fields as shown in FIG. 4 (see FIG. 4(a)), the image signal output from the video camera 3 (see FIG. 4(d)) is Since only one image is output, the flickering on the monitor becomes intense and unnatural. Therefore, a frame memory (not shown) is provided to store image signals for each period of intermittent light emission, and the image signal when I RED 1 emits light is stored in this memory. (No) Replace with field signal. With this, it is possible to obtain a natural screen without flicker on the monitor. At this time, the period of the control signal (see Fig. 4(b)),
In other words, the period of light emission is the light emission peak L3 (Fig. 4 (C
).

FIG. 5 is a circuit configuration diagram showing another example of the present invention. In this embodiment, a series circuit of a plurality of resistors R3 to R6 and transistors Q3 to Q6 is connected to I RED 1 in parallel. And each transistor Q3 to Q6
IREDI is limited by resistors R3 to R6, respectively.
energizing current flows.

With this configuration, each transistor Q3 to Q6 is selected when the level of the video image signal from a night vision camera, etc. is sufficient (a certain level or higher) when intermittent light emission is performed every one field or every few fields. By applying electricity, the light emission peak amount of I RED 1 can be varied, and the video signal can be kept constant. That is, I RED 1
By lowering the duty ratio of the energizing current (current-constant) or by lowering the current, there is less consumption. The lighting distance can be increased using electric current, and the entire system can be constructed economically.

〔Effect of the invention〕

As explained above, according to the present invention, since the infrared light source is made to emit light intermittently and the light emission peak amount can be changed, the light emission peak amount of the infrared light source can be increased, the illumination distance is longer, and the consumption is increased. The effect is that the current is small and miniaturization is possible.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing one embodiment of the present invention, FIG. 2 is an outline diagram of a video camera having the circuit configuration of FIG. 1, and FIG.
The figure is a waveform diagram showing the relationship between the control signal and the amount of light emitted, Figure 4 is a waveform diagram showing the case where frame memory is used, and Figure 5 is a waveform diagram showing the relationship between the control signal and the amount of light emitted.
6 is a circuit configuration diagram showing another embodiment of the present invention, FIG. 6 is a circuit configuration diagram showing a current supply system of a conventional imaging device, and FIG.
FIG. 3 is a waveform diagram showing the operation of the circuit shown in the figure. 1-----IRED (infrared light source) 2...Light emission control device 3, -...Video camera 5...Subject

Claims (3)

[Claims] (1) An imaging device equipped with an infrared light source for illuminating a subject, characterized in that the imaging device is provided with a light emission control device that causes the infrared light source to emit light intermittently and changes the peak amount of light emission. (2) The imaging device according to claim 1, wherein the light emission control device is capable of varying the period of intermittent light emission. (3) The imaging device according to claim 1 or 2, further comprising a memory that stores signals captured during intermittent light emission for each period of intermittent light emission.