JPH0983945A - Video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it hard to generate blur caused by hand shake or the moving of a screen and to be influenced by flickering under a fluorescent lamp by increasing the shutter speed in a still picture recording mode in a camera capable of setting a still picture mode. SOLUTION: The shutter of a moving picture mode is set to 1/60sec, e.g. In the still picture mode, the shutter speed is set higher than this value. As the shutter speed is high in the still picture mode, blur is hardly generated. At the time of corresponding to the brightness of a room at the time of recording a still picture, the shutter speed is set to 1/100sec. Thereby flickering is not generated even under the fluorescent lamp turned on through the use of the power source of 50Hz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a video camera device suitable for use in a camera-integrated VTR having a still image recording mode.

[0002]

2. Description of the Related Art Development of a digital video recording camera integrated type VTR in which a digital video signal based on an image pickup signal is compressed by DCT (Discrete Cosine Transform) conversion and a variable length code and recorded on a magnetic tape by a rotary head. ing. Such a digital recording camera-integrated VTR is provided with a still image recording mode as well as a moving image recording mode. When the still image recording mode is set, the image signal of one frame is repeatedly recorded for about 5 seconds. Since the still image recording mode can record a still image as digital data, it can be used when the still image is captured in a personal computer for processing or is directly printed out.

In such a digital VTR of the digital recording system, a CCD image pickup device is used as an image pickup device. The shutter speed of this CCD image sensor is 1/60 second in the normal NTSC system. That is, in the CCD image pickup device, the photocharges generated by the incident light are accumulated only for one field and transferred during the vertical blanking period. In the NTSC system, an image of 60 fields is sent per second, so the exposure time is 1/60
Seconds. Therefore, in the NTSC system, the CCD is usually used.
The shutter time of the image sensor is 1/60 second.

As described above, the digital recording type VT
In R, a still image recording mode is prepared. When recording a still image, when the shutter speed is 1/60, blurring due to camera shake or screen movement is likely to occur. Therefore, in the case of a digital-recording camera-integrated VTR capable of recording a still image, it is conceivable to increase the shutter speed when recording in the still image mode.

[0005]

If the shutter speed is set high when recording in the still image mode, blurring due to camera shake or screen movement is less likely to occur when shooting outdoors, and good results are obtained. Is obtained.

However, if the shutter speed is set to a high speed in recording in the still image mode as described above, when recording is performed in a room under a fluorescent lamp, a change in brightness or a color is generated due to the flicker of the fluorescent lamp. easy.

It is known that flicker does not occur at a shutter speed of 1/100 second under a fluorescent lamp lit by an AC power supply of 50 Hz.
Determine if the user is shooting under fluorescent lights,
It is not convenient to change the shutter speed manually.

Therefore, an object of the present invention is to increase the shutter speed in the still image recording mode so that blurring due to camera shake or screen movement is less likely to occur, and the video is less susceptible to flicker under fluorescent light. It is to provide a camera device.

[0009]

According to the present invention, there is provided an image pickup means having a variable shutter speed, an exposure control means for detecting an image pickup output level from the image pickup means, and performing an exposure control according to the image pickup output level. A video camera device comprising: a recording unit that can set a moving image mode and a still image mode; and a control unit that controls an operation state of an exposure control unit according to the moving image mode and the still image mode. .

The shutter speed in the moving image mode is, for example,
It is set to 1/60 seconds. In still image mode, the shutter speed is set higher than this. In the still image mode, since the shutter speed is fast, blurring is less likely to occur.

Further, at the time of recording a still image, when the brightness corresponds to the indoor brightness, the shutter speed is set to 1/100 second. As a result, flicker does not occur even under a fluorescent lamp that is lit using a power source with a frequency of 50 Hz.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, subject image light is incident through a lens 1. This object image light is
An image is formed on the light receiving surface of the CCD image pickup device 3 via the diaphragm 2. The opening and closing of the diaphragm 2 is controlled by the microcomputer 5. By controlling the opening and closing of the diaphragm 2, the CCD
The amount of incident light on the image sensor 3 can be adjusted.

As the CCD image pickup device 3, there is used a device capable of varying the shutter speed by sweeping away unnecessary charges by using a sweeping drain. The shutter speed is changed by the output of the timing generator 4 under the control of the microcomputer 5.

The subject image light is photoelectrically converted by the CCD image pickup device 3. The output of the CCD image pickup device 2 is supplied to the AGC amplifier 6. The gain of the AGC amplifier 6 is controlled by the output of the microcomputer 5. The output of the AGC amplifier 6 is supplied to the camera signal processing circuit 7 and the detector 8. The detector 8 detects the amount of incident light. The output of the detector 8 is supplied to the microcomputer 5.

The camera signal processing circuit 8 performs gamma correction, aperture correction, and the like. Further, the camera signal processing circuit 8 forms a component color video signal from the image pickup signal. The output of the camera signal processing circuit 8 is supplied to the compression circuit 9. The compression circuit 9 compresses the video signal by using the DCT and the variable length code. The output of the compression circuit 9 is supplied to the error correction coding circuit 10. The error correction coding circuit 10 performs error correction coding processing. The output of the error correction coding circuit 10 is supplied to the channel coder 11. The recording data is modulated by the channel coder 11. Channel coder 11
Is supplied to the head 13 via the recording amplifier 12. A digital video signal is recorded on the magnetic tape 14 by the head 13.

In this embodiment, mode setting signals for normal recording mode and still image mode can be set. In the moving image mode, a moving image captured by the CCD image sensor 3 is recorded. An image of one frame is recorded on 10 tracks, for example. In the still image mode, one frame image is continuously recorded for 5 seconds, for example.

The microcomputer 5 includes a detector 8
Depending on the amount of incident light detected by
Exposure control is performed by changing the shutter speed of the image sensor 3 and the gain of the AGC amplifier 6. That is, when the amount of incident light is large, the aperture 2 is closed, the shutter speed is increased, and the gain of the AGC amplifier 6 is reduced, whereby the amount of incident light can be reduced. When the amount of incident light is small, the amount of incident light can be increased by opening the diaphragm 2, slowing the shutter speed, and increasing the gain of the AGC amplifier 6. As a result, exposure control can be automatically performed. The input terminal 15
Is supplied with mode setting signals for the normal recording mode and the still image mode. As will be described later, the operation state of the exposure control is switched according to this mode.

As described above, depending on the amount of incident light, the diaphragm 2
The automatic exposure control can be performed by opening and closing and changing the gain of the AGC amplifier 6. Further, when the CCD image pickup device 3 whose shutter speed can be changed is used, automatic exposure control can be performed by changing the shutter speed according to the amount of incident light. When performing automatic exposure control in this way, it is necessary to pay attention to the following points (1) to (3).

(1) When the gain of the AGC amplifier 6 is increased, noise becomes conspicuous. Therefore, the gain of the AGC amplifier 6 is set to 0 dB as much as possible.

(2) When recording a moving image, the shutter speed is 1 /
Even for 60 seconds, blurring due to camera shake or screen movement is less noticeable, but in still image recording, blurring due to camera shake or screen movement is likely to occur. Therefore, it is desired to increase the shutter speed in the still image mode.

(3) Under a fluorescent lamp in a room, if the shutter speed is increased, the change in brightness due to flicker tends to stand out. For example, under a fluorescent lamp lit by using an AC power supply with a frequency of 50 Hz, if the shutter speed is set to 1/100 second, it is less likely to be affected by flicker.

In one embodiment of the present invention, the above (1)-
In consideration of the point (3), the operation state of the exposure control is switched according to the normal mode and the still image mode.

In the normal mode (moving image shooting), control as shown in FIG. 2 is performed. In FIG. 2, the horizontal axis represents the brightness. In the normal mode, in the case where the incident light is less than the brightness L _1, L ₁ or more and when the processing is switched.

When shooting a moving image, the shutter speed is set to 1/60 second in the NTSC system. Since it is desired to set the gain of the AGC circuit 6 to 0 dB as much as possible, the gain of the AGC circuit 6 is set to 0 dB when the brightness of the incident light is L ₁ or more, and the diaphragm 2 is opened and closed.
Exposure control is performed.

When the brightness is less than L ₁ , the required light quantity cannot be obtained even if the diaphragm 2 is completely opened when the gain of the AGC circuit 6 is 0 dB. Therefore, when the brightness is L ₁ or less, the diaphragm 2 is opened and the gain of the AGC circuit 6 is 0d.
The exposure is controlled by changing from B to +18 db.

As described above, in the normal mode, the exposure control is performed so that the shutter speed is 1/60 seconds and the gain of the AGC circuit 6 is 0 dB as much as possible.

In the still image mode, control as shown in FIG. 3 is performed. As shown in FIG. 3, in the still image mode, when the brightness of the incident light is less than L ₁₁ , between L _{11 and} L ₁₂ , between L _{12 and} L ₁₃ , ₁₃ ~ L ₁₄
The processing is switched depending on whether it is between L and L ₁₄ or more. The amount of incident light corresponding to the brightness L ₁₃ corresponds to the boundary between the brightness for indoor shooting and the brightness for outdoor shooting.

In the still image mode, it is desirable to increase the shutter speed in order to prevent blurring due to camera shake or screen movement. When the brightness of the incident light is L ₁₃ or more,
It can be determined that the image is taken outdoors, and outdoors, there is no problem due to flicker under indoor fluorescent lights.

Therefore, when the incident light is L _{13 to} L ₁₄ ,
The gain of the AGC circuit 6 is set to 0 dB, the aperture of the diaphragm 2 is opened to an appropriate aperture (for example, aperture F4.8), the shutter speed is changed to 1/100 to 1/1000,
Exposure control is performed.

When the amount of incident light is L ₁₄ or more, the gain of the AGC circuit 6 is set to 0 dB and the shutter speed is 1
000, the aperture of the diaphragm 2 is changed from F4.8 to a small diaphragm, and exposure control is performed.

When the brightness of the amount of incident light is less than L ₁₃ ,
It can be determined that the image was taken under a fluorescent lamp in the room. Under a fluorescent lamp in a room, if the shutter speed is set to 1/100, it is not affected by flicker such as fluorescence. However, if the shutter speed is set to 1/100, it will be 1 times the normal shutter speed.
The shutter speed is faster than / 60, and it is less susceptible to the effects of motion blur and camera shake.

Therefore, when the incident light is L _{12 to} L ₁₃ ,
The shutter speed is set to 1/100 to avoid the influence of flicker such as fluorescence. Gain of AGC circuit 6 is 0
Since it is set to dB, the AGC circuit 6 is prevented from generating noise. Then, the aperture of the diaphragm 2 is changed from the maximum to a predetermined aperture (for example, the aperture F4.8), and the exposure control is performed. The aperture F4.8 is set so that the shutter speed is 1/100 and the gain of the AGC circuit 6 is 0 dB.
When it is set, the brightness of the boundary between the indoor and the outdoor corresponds to the experimental value for making the incident light quantity the optimum value.

When the brightness of the incident light amount is L _{11 to} L ₁₂ , the optimum incident light amount cannot be obtained even if the diaphragm 2 is opened to the maximum. Therefore, the gain of the AGC 6 is changed so that the required amount of incident light can be obtained. That is, when the brightness of the incident light amount is L _{11 to} L ₁₂ , the shutter speed is set to 1/100, and the influence of flicker such as fluorescence is avoided. The opening of the diaphragm 2 is set to the maximum value. Then, the gain of the AGC circuit 6 is changed from +18 dB to 0.
The exposure is controlled by changing to dB.

When the brightness of the amount of incident light is less than L ₁₁ ,
Open the diaphragm 2 to the maximum and set the gain of the AGC circuit 6 to + 18d.
Even if it is raised to B, the required amount of incident light cannot be obtained. Therefore, the diaphragm 2 is opened to the maximum and the gain of the AGC circuit 6 is +
The exposure speed is set to 18 dB, the shutter speed is changed from 1/100 to 1/60, and exposure control is performed.

As described above, in the still image mode, when shooting outdoors, the shutter speed becomes faster, and it is possible to prevent blurring due to camera shake or a subject that moves rapidly. Furthermore, when shooting indoors, the shutter speed is 1 /
It becomes 100, which is less likely to be affected by flicker under a fluorescent lamp, and the shutter speed is faster than 1/60 of the normal shutter speed, so that blurring due to camera shake or a subject with rapid movement can be prevented to some extent. .

[0036]

According to the present invention, the operation state of the exposure control can be switched according to the still image mode and the moving image mode. The shutter speed in the movie mode is, for example, 1/60
Set to seconds. In still image mode, the shutter speed is set higher than this. In the still image mode, since the shutter speed is fast, blurring is less likely to occur. Further, at the time of recording a still image, when it corresponds to the brightness of the room, the shutter speed is set to 1/100. As a result, flicker does not occur even under a fluorescent lamp that is lit using a power source with a frequency of 50 Hz.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of a video camera to which the present invention has been applied.

FIG. 2 is a schematic diagram used for explaining an example of a video camera to which the present invention is applied.

FIG. 3 is a schematic diagram used to describe an example of a video camera to which the present invention is applied.

[Explanation of symbols]

 2 Aperture 3 CCD image sensor 5 Microcomputer 6 AGC amplifier

Claims (3)

[Claims] 1. An image pickup unit having a variable shutter speed, an exposure control unit for detecting an image pickup output level from the image pickup unit and performing exposure control according to the image pickup output level, a moving image mode and a still image mode. And a control means for controlling the operating state of the exposure control means according to the moving image mode and the still image mode. 2. The video camera device according to claim 1, wherein the exposure control means controls an iris, a shutter speed, and a gain of an AGC circuit, respectively, according to an image pickup output level from the image pickup means. . 3. The video camera according to claim 1, wherein, in the still image mode, a shutter speed related to flicker caused by a fluorescent lamp is set within a range in which an image pickup output level from the image pickup means corresponds to room light. apparatus.