JPH09252423A - High sensitivity tv camera - Google Patents

Abstract

[PROBLEMS] To provide a compact and highly sensitive television camera capable of highly sensitive shooting by using an image sensor capable of controlling exposure time. SOLUTION: A solid-state image sensor 1 capable of controlling an exposure time is used, and a slow shutter control circuit 101 is provided in which the exposure time is a plurality of field periods of a television signal and the signal extraction time is one field period. A small and high-sensitivity television camera is realized by repeatedly storing the same video signal stored in the field memory 104 during the next exposure time while storing it in the field memory 104.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television camera using an image pickup device whose exposure time can be controlled, and particularly to a television camera having high sensitivity.

[0002]

2. Description of the Related Art The following is known as a means for increasing the sensitivity in a dark place in a television camera or a camera body type VTR using a standard television system. The first means is to increase the aperture of the taking lens,
The second means is to increase the light receiving area of the image sensor. However, it is not easy to increase the sensitivity several times by these techniques.

In a special camera such as a night-vision camera, there is known a means for increasing the exposure time until the image sensor is exposed with an amount of light that can be taken out as an electric signal. It is self-evident that a long exposure time can capture a dark subject as long as it is not buried in noise, and the special camera is based on this idea. However, in order to obtain a conventional TV camera with a long exposure function, the deflection frequency of the image pickup tube must be lowered.
Although a method of lowering the clock frequency of a solid-state image sensor is known, it is difficult to change the frequency drastically, and further, conversion to a standard television system has not been easy.

For example, a video tape recorder (VT)
R) requires a special device such as once recording and high-speed reproduction, or A / D conversion for time compression, and D / A conversion for extraction.

[0005]

According to the prior art,
In order to achieve high sensitivity, there is a drawback that the TV camera becomes heavy and large. In addition, the special camera system has a drawback that a standard television signal such as NTSC cannot be easily extracted. Further, in order to realize a television camera with a long-time exposure function, a special device is required, which is generally difficult to implement.

[0006]

When an image pickup device capable of controlling an exposure time, a detection device for detecting an output signal level of the image pickup device, and an output signal determined by the detection device is below a predetermined level An exposure time control means for automatically controlling the exposure time of the image pickup device so as to be continuous for a plurality of field periods; and a storage device for receiving an output of the image pickup device and storing a video signal for one field or one frame. Switching means for selecting and outputting the output of the image pickup element and the output of the storage device, and recording means for sharing the storage device and recording the output selected by the switching means on a recording medium. When the output signal is below a predetermined level and the exposure time of the image sensor is controlled to continue for a plurality of field periods, the output of the image sensor to the storage device is performed. Said from the storage device to output the same video signal to constitute a high-sensitivity television camera to be recorded on the recording means stores the to solve the above problems.

That is, an image pickup device whose exposure time can be controlled (for example, a so-called solid-state image pickup device with an electronic shutter function)
Is used to provide a slow shutter control circuit that operates when the subject is dark. The storage device is also used for variable speed reproduction and slow shutter.

The slow shutter control circuit controls the image pickup device as follows. It is assumed that the television signal is continuously exposed for a plurality of fields or a plurality of frames, and the video signal obtained by the exposure is taken out for one field or one frame of the television signal. The video signal is stored in a storage device and is output as a television signal. During the next exposure time, that is, until the image sensor completes the previous exposure and outputs the next video signal, the previously stored same video signal is repeated every field period or frame period of the television signal. read out. By repeating this operation, a high-sensitivity TV camera is obtained.

Since the slow shutter control circuit is provided by using the image pickup device whose exposure time can be controlled, it is possible to perform exposure for a plurality of field periods without lowering the operation clock frequency of the image pickup device. In the slow shutter control circuit, for example, by thinning out a charge transfer pulse for extracting a signal charge generated by light reception compared to once per field during normal photographing, an integer multiple of one field period is continuously generated, The signal charges are accumulated in the light receiving portion of the image sensor.

Further, since the operation clock frequency is not lowered when the signal charge is taken out, the signal charge can be taken out in the same time as one field during normal photographing. Along with this, one field of the television signal can be taken out by using the conventional peripheral circuit without performing a special operation such as time compression.

Further, the signal for one field is output and stored in the storage device, and the same video signal is repeatedly read out for every one field period from the storage device during the next exposure period and is interpolated. Therefore, a continuous signal can be obtained as a television signal. Especially when shooting a dark subject, since the unnaturalness of the motion of the image due to the interpolation is often less affected, a high-sensitivity, large-diameter lens or a special device is not required, and the storage device is designed for variable speed reproduction or the like. A small and lightweight television camera can be obtained because the invention is switched to use for the slow shutter of the invention. Although the above description has dealt with handling in units of one field, the same applies even if the whole or one part is in units of one frame.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an embodiment applied to a camera-integrated VTR, and a portion surrounded by a dotted line is a portion newly added to a conventional camera-integrated VTR. FIG. 2 is a timing diagram. The configuration will be described first with reference to FIG.
The solid-state image sensor 1 is known to be of a MOS type, a CCD type, or the like, but in the present embodiment, the exposure time can be controlled by operating the extraction timing of the signal generated by light reception or the sweeping timing of the excess signal charge (so-called). Use electronic shutter function).

The image sensor control circuit 2, the high-speed shutter timing generator 3, and the reference oscillator 4 are circuits for driving and controlling the solid-state image sensor 1 having an electronic shutter function. An image pickup signal output from the solid-state image pickup device 1 is converted by a camera signal processing circuit 5 into a normal television signal such as NTSC. Up to this point, it is a TV camera unit with an electronic shutter. The recording signal processing circuit 6 performs signal processing for recording and sends it to the video head 7.

Next, the structure of the portion newly added in the embodiment of FIG. 1 will be described. First, in the slow shutter control circuit 101, the conventional (high speed) electronic shutter is 1 /
It is a circuit for detecting the darkness of the subject and setting the shutter speed to about 1/6 second to 1/30 second, while it is about 60 seconds to 1/2000 second. The circuit is composed of a level detector 11, a shutter switching circuit 12, and a low speed shutter timing generator 13.

The brightness of the subject is detected by the level detection 11 using the signal level of the camera signal processing circuit 5, and when the subject is dark, the shutter switching circuit 12 changes the timing generator from the high speed shutter 3 to the low speed shutter. Switch to 13.

The field memory unit 102 is a circuit which stores the video signal from the camera signal processing circuit 5 and can read out the necessary number of times for each field of a normal television signal. The circuit includes an A / D converter 103, a field memory 104, a memory controller 105, a D / A converter 106 and the like.

The memory controller 105 is a circuit for controlling a clock and a control signal for writing or reading in the field memory 104.
A switching signal for the switching circuit 108 is also generated from this circuit.

The clock and control signal generation circuit 107 obtains a timing pulse from the slow shutter control circuit 101 to take out continuous television signals even during slow shutter operation, such as time control of memory writing or reading of the field memory unit 102. It is also responsible for generating the clock and control signals.

The switching circuit 108 is a switching circuit for switching between sending the output of the camera signal processing circuit 5 directly to the recording signal processing circuit 6 and sending the output from the field memory unit 102.

The detailed structure and operation will be described below.
When the solid-state imaging device 1 uses, for example, an interline CCD, a video signal in units of one field is often output using the field blanking period. And one field of a normal television signal is in the case of NTSC system,
1/60 second, shutter speed is 1/6 naturally
0 seconds is common.

In the case of having an electronic shutter function, in the high-speed shutter, the signal charge accumulation time from once sweeping out the signal charges of the light receiving portion of the solid-state image pickup device 1 to emptying and starting transfer is shortened to less than 1/60 second, This is often achieved by discarding the excess charge. It is important that the timing generator 13 for the low-speed shutter in the slow shutter control circuit 101 of the present embodiment performs a completely opposite operation as compared with the high-speed shutter 3. That is, without transferring charges for a plurality of field periods, charges are continuously stored in the light receiving portion for a plurality of field periods, and then charges are transferred for signal extraction.

As an exposure time control method, even when an image pickup device is used in which the sweeping-out timing of surplus signal charges is changed, by thinning out the signal charge transfer pulses for reading, a plurality of field periods can be continuously generated. The signal charges can be accumulated by using the above.

As a result, the shutter can be released slower than 1/60 second, and the sensitivity can be increased several times as compared with the case where the light receiving portion of the solid-state image pickup device 1 is widened or the image pickup lens having a large aperture is used. You can Further, even if exposure is performed for a plurality of field periods, charge transfer for signal extraction is performed at the same time as transfer of one field of the television signal, and therefore, the signal is transferred via the camera signal processing circuit 5 without adding a special circuit. A video signal for one field of the television signal is taken out.

However, according to the above-mentioned means, there is a blank period until the next video signal for one field is output. For example, when exposure is performed for 10 field periods (1/6 second), a blank period of 9 field periods occurs. Therefore, the output of the camera signal processing circuit 5 is sent to the recording signal processing circuit 6 via the switching circuit 108, and at the same time, sent to the field memory unit 102, stored in the field memory 104 via the A / D converter 103, and further D / A
Read through the converter 106, the blank period mentioned above,
The same video signal is continuously sent to the recording signal processing circuit 6 via the switching circuit 108 once in one field period.

As a result, the recording signal processing circuit 6 can obtain an interpolated television signal without the blank period, although the same video signal is repeated during the continuous time required for the exposure. FIG. 2 shows the timing diagram described above.

In the above, the charge transfer is carried out in the unit of one field, but it may be carried out in the unit of one frame, in which case the general shutter speed is 1/30 in NTSC. Although the field memory unit 102 is used, it may be advantageous to use the frame memory. In that case, the field memory 104 may be replaced with the frame memory.

The field memory unit 102
The switching circuit 108 and the switching circuit 108 are arranged in the TV camera section.
It may be provided in the R portion. In that case, a memory unit provided for the purpose of variable speed reproduction (slow, still, etc.) can be switched and used.

With the above implementation, a television camera can be obtained which detects the brightness level of a subject and automatically switches to a low-speed shutter when the subject is dark to enable high-sensitivity photography several times as high as the conventional one.

[0029]

According to the embodiments of the present invention, that is, the slow shutter control circuit is provided by using the image pickup device capable of controlling the exposure time, the signal output of the image pickup device is stored, and repeatedly read out and interpolated during the continuous exposure period. As a result, a compact and highly sensitive television camera can be obtained. The television camera does not require a large-diameter lens or a large-area image pickup device, does not require a special device, and has a configuration in which a conventional television camera is provided with an additional circuit in front of it. High-sensitivity shooting is possible. This television camera is particularly suitable for use in a camera body type VTR.

[Brief description of drawings]

1 is an example of an embodiment in which the present invention is applied to a camera body type VTR, and a dotted line portion is a portion newly added in comparison with a conventional example.

FIG. 2 shows a timing diagram of an example embodiment.

[Explanation of symbols]

1 ... Solid-state image sensor, 2 ... Image sensor control circuit, 3 ... High-speed shutter timing generator, 4 ... Reference oscillator, 5 ... Camera signal processing circuit, 6 ... Recording signal processing circuit, 7 ... Video head, 8 ... Monitor Signal processing circuit,
9 ... Monitor, 11 ... Level detection, 12 ... Shutter switching circuit, 13 ... Low speed shutter timing generator, 101 ... Slow shutter control circuit, 102 ... Field memory unit, 103 ... A / D converter, 104 ... Field memory, 105 ... Memory controller, 106 ... D / A converter, 107 ...
Clock and control signal generation circuit, 108 ... Switching circuit

Claims (1)

[Claims] 1. An image pickup device capable of controlling an exposure time, a detection device for detecting an output signal level of the image pickup device, and the image pickup device when the output signal is judged to be below a predetermined level by the detection device. An exposure time control means for automatically controlling the exposure time of the element so as to be continuous for a plurality of fields; a storage device for receiving the output of the image sensor and storing a video signal for one field or one frame; Of the output of the storage device and a switching device for selecting and outputting the output of the storage device, and a recording device for sharing the storage device and recording the output selected by the switching device on a recording medium. When the exposure time of the image pickup device is below a predetermined level and is controlled so as to continue for a plurality of field periods, the output of the image pickup device is stored in the storage device. A high-sensitivity television camera, which is configured to output the same video signal from the storage device and record the same in the recording means.