JP3391491B2 - Video camera and control method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a video camera and a control method thereof.

[0002]

BACKGROUND ART In general, a video camera shoots at a shutter speed of 1/60 second. For this reason, when trying to perform still reproduction of one frame in the motion of the subject from this movie video signal, only the faint reproduction in which the image flows can be performed.

In order to obtain a clear image for a moving subject during still reproduction, it is necessary to shoot at a high shutter speed, but then, when reproducing a movie, the sense of continuity of each frame of the image is lost and the image is reproduced. The movement of the subject in the captured image becomes very unnatural, and the two requirements are incompatible. In order to satisfy these two requirements, it is conceivable that, for example, one shot out of a plurality of consecutive shots at a high shutter speed and another shot at a normal shutter speed are repeated periodically.

A clear still image can be obtained by using a video signal obtained by photographing at a high shutter speed, and the photographing at a high shutter speed is performed only once in a plurality of times, so that the continuity of the image is lost. Nothing.

When shooting at a high shutter speed, the level of the video signal is lower than when shooting at a normal shutter speed, and the printed image may become dark when printed. In this case, it is conceivable to use an automatic gain adjustment circuit to amplify the video signal obtained by shooting at high shutter speed.
If the level of a video signal shot at a normal shutter speed and the level of a video signal shot at a high shutter speed are extremely different, the amplification rate of the video signal shot at a high shutter speed must be raised extremely. . For this reason, the S / N is lowered and the quality of the reproduced image is also lowered.

[0006]

DISCLOSURE OF THE INVENTION It is an object of the present invention to improve the S / N ratio of a video signal captured by a video camera.

[0007]

[0008]

[0009]

[0010]

The video camera of the present invention comprises a shutter means capable of shooting at a high shutter speed and shooting at a normal shutter speed, and shooting at a high shutter speed once in a plurality of consecutive times. Other than that, a shutter control means for controlling the shutter means so as to repeat shooting at a normal shutter speed, a first video signal is output by shooting at the high shutter speed, and a shutter speed is set at the normal shutter speed. Shooting means for outputting a second video signal by shooting, a storage means for storing the second video signal output from the shooting means, and a current image output from the shooting means by shooting at the high shutter speed. On the basis of the first video signal and the second video signal representing the previous image photographed last time read from the storage means. Motion determining means for determining whether there is motion between the current image and the previous image, and the first video signal and the second video when the motion determining means determines that there is no motion. A signal is added to the signal and output, and when it is determined that there is a motion, an adding unit that outputs the first video signal as it is is provided.

The video camera control method of the present invention is as follows:
Shooting at high shutter speed once in a series of multiple shots and shooting at normal shutter speed are repeated, and the first video signal is obtained by shooting at the above high shutter speed. The first video signal of the current image obtained by shooting at the high shutter speed mentioned above, the second video signal is obtained by shooting at the shutter speed of, and the second video signal obtained by the shooting is temporarily stored. And the second video signal representing the previous image that was temporarily stored and photographed last time, it was determined whether there was motion between the current image and the previous image, and it was determined that there was no motion. In some cases, the first video signal and the second video signal are added and output, and when it is determined that there is motion, the first video signal is output as it is.

According to the present invention, it is determined whether or not there is a movement between the current image taken at a high shutter speed and the previous image taken one image before the current image.
When it is determined that there is no motion, the first video signal representing the current image and the second video signal representing the previous image are added and output, and when it is determined that there is motion, the first video signal representing the current image is displayed. The video signal is output as it is.

Although the level of the video signal obtained by shooting at the high shutter speed is lower than the level of the video signal obtained by shooting at the normal shutter speed, according to the present invention, the image signal is shot at the high shutter speed. Since the level of the video signal of the current image will rise, S
/ N is improved. Further, when there is a motion between the current image and the previous image, the first video signal and the second video signal are not added, so that the image does not shake.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates an embodiment of the present invention, and is a block diagram showing the electrical construction of a video camera.
FIG. 2 shows a time chart when shooting is performed using the video camera shown in FIG.

As a general rule, a video camera continuously field-photographs a subject at a shutter speed of 1/60 second, but once every a plurality of fields (for example, 18 fields), a high shutter speed (for example, 1/250).
It is a camera that shoots movies in seconds. Shooting timing at high shutter speed is system controller 20
It is determined based on the shutter speed switching control signal output from the CCD drive circuit 17 to the CCD drive circuit 17.

The image of the subject is taken by the image pickup lens 2 to the CCD 3
Imaged above.

The CCD 3 performs an electronic shutter operation under the control of the CCD drive circuit 17. The CCD 3 repeats a plurality of continuous shots at a normal shutter speed of 1/60 second and a single shot at a high shutter speed of 1/250 second. FIG. 2 shows the timing of switching the shutter speed and the timing of the video signal output from the CCD 3. In this figure, a hatched portion shows a portion photographed at a high shutter speed, and a portion other than the hatched portion shows a portion photographed at a normal shutter speed.

The video signal output from the CCD 3 is given to an automatic gain adjustment circuit (AGC) 5 via a correlated double sampling circuit (CDS) 4.

The AGC 5 amplifies the video signal obtained at the high shutter speed photographing, in comparison with the amplification factor of the video signal obtained at the normal shutter speed photographing, based on the gain control signal from the system controller 20. The rate is increased and the input video signal is amplified.
The level of the video signal obtained at the high shutter speed is lower than the level of the video signal obtained at the normal shutter speed, but the level of the video signal obtained by the AGC 5 at the normal shutter speed is reduced. Level improves.

The video signal output from the AGC 5 is given to the video signal processing circuit 6. The video signal processing circuit 6 performs signal processing such as color balance adjustment, gamma correction, luminance signal generation, and color difference signal generation on the input video signal.

The video signal output from the video signal processing circuit 6 is given to the A / D conversion circuit 7, the motion detection circuit 10 and the resistance addition circuit 12, respectively.

The video signal applied to the A / D conversion circuit 7 is digitally converted and applied to the video memory 8, where 1
Data for one image (one field) is stored.

The video memory 8 can store image data for two fields, and the next image data can be input and stored while the image data is being output. However, if you use a video memory that can write and read image data at almost the same time, 1
It may be one that can store image data for fields. Further, in a video camera for performing frame shooting, a video memory for storing image data for two frames or a video memory for storing image data for one frame capable of writing and reading image data at almost the same time is used. .

The data for one image stored in the video memory 8 is output after 1/60 seconds and is given to the D / A conversion circuit 9 to be converted into an analog video signal. This analog video signal is applied to the motion detection circuit 10 and the switch circuit 11, respectively.

When the image represented by the video signal for one image output from the video signal processing circuit 6 is the current image, the image represented by the video signal output from the D / A conversion circuit 9 is 1/1 of the current image. This is the previous image taken 60 seconds ago. Therefore, the motion detection circuit 10 receives a video signal representing the current image and a video signal representing the previous image.

The motion detection circuit 10 can be constituted by, for example, a comparator, and determines whether the difference between the level of the video signal representing the current image and the level of the video signal representing the previous image is equal to or more than a certain level. It is a circuit that detects whether or not there is a movement of the subject between and.
The operation of the motion detection circuit 10 is controlled based on the high speed shutter speed information provided from the system controller 20, and the video signal captured at the high shutter speed is input from the video signal processing circuit 6 to the motion detection circuit 10. Only when it is controlled to detect if there is motion between the previous image and the current image.

When the motion detection circuit 10 detects that there is no motion between the current image and the previous image, the motion detection circuit 10
A switch control signal for turning on the switch circuit 11 is output from the switch circuit 11, and when it is detected that there is motion between the current image and the previous image, the motion detection circuit 10 switches to the switch circuit 11. A switch control signal for turning off the circuit 11 is output.

When there is no movement between the previous image and the current image, the switch circuit 11 is turned on, and the video signal representing the previous image is given to the resistance addition circuit 12.

The resistance adder circuit 12 is composed of resistors 13 and 14 and an adder 15. The video signal representing the current image is given to the adder 15 via the resistor 14. When the switch circuit 11 is turned on, the video signal representing the previous image is given to the adder 15 via the resistor 13.

When a video signal taken at a high shutter speed is output from the video signal processing circuit 6, it is detected whether or not there is a motion between the previous image and the current image. When there is no motion, the resistance adding circuit 12 Thus, the video signal representing the previous image and the video signal representing the current image are added. Therefore, it is possible to raise the level of the video signal shot at the high shutter speed without raising the gain of the AGC 5 so much.

When there is a motion of the subject between the previous image and the current image, the switch circuit 11 is turned off, so that only the video signal representing the current image is input to the resistance addition circuit 12, which represents the current image. The video signal and the video signal representing the previous image are not added. Therefore, the reproduced image does not shake due to the movement of the subject.

The video signal output from the resistance addition circuit 12 is applied to the recording / reproduction processing circuit 16. When a video signal shot at a high shutter speed is input to the recording / playback processing circuit 16, the system
An index signal is given from the controller 20. As a result, the index signal is superimposed on the video signal, and it becomes possible to identify whether or not shooting is performed at a high shutter speed.

The recording / reproducing processing circuit 16 performs recording processing such as pre-emphasis (high-frequency emphasis) and FM modulation of the input video signal and outputs it as a recording signal. The recording signal is recorded on the video tape by a recording / reproducing head (not shown).

The video camera shown in FIG. 1 can also perform reproduction processing.

When the reproducing process is performed, the video signal recorded on the video tape is read by a recording / reproducing head (not shown) and given to the recording / reproducing processing circuit 16. In the recording / reproduction processing circuit 16, the input video signal is demodulated, de-emphasized, etc., and output as a reproduction signal.

FIG. 3 shows another embodiment.
It is a block diagram which shows the electric constitution of a camera. In this figure, the same components as those shown in FIG. 1 are designated by the same reference numerals.

The video camera shown in FIG. 3 does not include the motion detection circuit 10 as compared with the video camera shown in FIG.

In the video camera shown in FIG. 3, whether or not there is motion between the current image and the previous image is determined by the system.
It is detected by the controller 20A. Therefore, the system controller 20A is supplied with the image data of the current image output from the A / D conversion circuit 7 and the image data of the previous image output from the video memory 8. system·
When the image data of the current image taken at a high shutter speed from the A / D conversion circuit 7 is input to the controller 20A, it is determined whether or not there is a subject motion between the current image and the previous image. Switch circuit 11 when there is no movement
Is turned on, and the video signal representing the current image and the video signal representing the previous image are added. Further, when the subject of the current image and the previous image is moving, the switch circuit 11 is turned off, and the video signal output from the video signal processing circuit 6 is given to the recording / reproducing processing circuit 16 through the resistance addition circuit 12. It is the same as the video camera shown in FIG. 1 described above.

In the embodiment shown in FIGS. 1 and 3, in order to improve the image quality of the image represented by the video signal captured at the high shutter speed, the current image represented by the video signal captured at the high shutter speed is improved. And whether there is a motion of the subject between the previous image and
The video signals are added when there is no movement. However, it is also possible to detect whether or not there is a motion between the current image and the previous image taken at a normal shutter speed, and add those video signals when there is no motion. As a result, the image quality of an image represented by a video signal obtained by shooting at a normal shutter speed is further improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a video camera according to an embodiment of the present invention.

FIG. 2 is a time chart when a picture is taken using the video camera shown in FIG.

FIG. 3 shows another embodiment and shows the electrical configuration of the video camera.

[Explanation of symbols]

3 CCD 6 Video signal processing circuit 8 video memory 10 Motion detection circuit 11 Switch circuit 12 Resistance addition circuit 17 CCD drive circuit 20, 20A system controller

Claims (2)

(57) [Claims] 1. A shutter means capable of shooting at a high shutter speed and shooting at a normal shutter speed, shooting at a high shutter speed once in a plurality of consecutive shots, and other normal shutter speeds. Shutter control means for controlling the shutter means so as to repeat shooting at each speed, a first video signal is output by shooting at the high shutter speed, and a second video signal is output by shooting at the normal shutter speed. Photographing means for outputting a video signal, storage means for storing a second video signal outputted from the photographing means, first video signal of the current image outputted from the photographing means by photographing at the high shutter speed And the second image signal representing the previously captured previous image read from the storage means, the current image and the previous image Between the first video signal and the second video signal when the motion determination means determines whether or not there is motion, and when the motion determination means determines that there is no motion, the result is output. A video camera having an adding means for outputting the first video signal as it is when it is determined that there is movement. 2. A first video signal obtained by shooting at a high shutter speed, once at a high shutter speed, and then repeatedly shooting at a normal shutter speed. , A second video signal is obtained by shooting at the normal shutter speed, the second video signal obtained by shooting is temporarily stored, and the current image obtained by shooting at the high shutter speed is obtained. On the basis of the first video signal and the second video signal which is temporarily stored and represents the previous image captured last time, it is determined whether or not there is a motion between the current image and the previous image. When it is determined that there is no motion, the first video signal and the second video signal are added and output, and when it is determined that there is motion, the first video signal is output as it is. Method of controlling the camera.