JPH0923371A - Imaging device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To quickly change imaging conditions when moving from a moving image mode to a still image mode. In a moving image mode, a video signal from a CCD 3 is processed by a camera processor 8 and a CPU 1
1, the amount of light incident on the CCD 3 from the video signal is measured, and the iris value, shutter speed, gain of the AGC circuit 6 and the like are controlled by AE control in accordance with this measurement. When shifting to the still image mode, the shutter speed is set to a predetermined value, and the CPU 11 immediately calculates the gain based on the incident light amount measured in the moving image mode and sets the gain in the register 16. Therefore, when shifting to the still image mode, it is possible to quickly set the imaging condition suitable for the still image even if the response of the AE operation is slow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus suitable for use in a video camera or the like for recording a video signal picked up by an image pickup device in a digital format on a tape.

[0002]

2. Description of the Related Art In recent years, with the progress of digital signal processing technology, many image pickup devices such as a video camera having an image pickup portion and a digital recording type recording / reproducing portion have been proposed. In these devices, a standard video signal is formed by an image pickup unit using a solid-state image pickup device such as a CCD, the video signal is compressed using discrete cosine transform (DCT) and quantization, and the compressed data is compressed. Is encoded into a format suitable for digital tape recording, and then recorded on the tape by the head. At the time of reproduction, the reproduction signal taken out by the head is error-corrected, and then decoded and expanded as opposed to recording and outputted as a reproduced video signal. In addition, one still image can be taken from a moving image shot with such an image pickup device and then hard-copied to enjoy it, or a still image can be input to a PC and processed on a PC for use. The uses of images are increasing.

[0003]

However, the above-mentioned conventional techniques have the following problems. That is, in the solid-state image sensor, interlaced reading is performed according to the standard television system. Therefore, when an image of the entire screen (one frame) is taken out, the screen is displayed in two fields at different times. Composed. This is not a problem when watching a normal moving image on a television, but for example, when playback is paused and viewed as a still image, when one frame of image is displayed, the moving part becomes jagged. If an image of only one field is displayed in order to remove this, the vertical resolution becomes low. For this reason, conventionally, when shooting a still image, the shooting conditions for the still image are changed in advance so that the shutter speed is faster than 1/60 second using a mechanical shutter or an electronic shutter of a CCD. I was taking pictures one by one. However, with this method, you can instantly switch the exposure condition from a moving image to a still image, even if you want to take one frame as a still image while shooting one frame as a still image with a short shutter speed. However, there is a problem that a still image cannot be captured under proper conditions.

Therefore, it is an object of the present invention to provide an image pickup apparatus capable of promptly setting the image pickup condition of a still image when capturing a still image during moving image pickup.

[0005]

In the present invention, an image pickup means for photoelectrically converting a subject image and outputting a video signal, and an exposing means for exposing the subject image to the image pickup means.
Signal processing means for selectively performing a first mode for processing a video signal obtained from the image pickup means to obtain a continuous moving image and a second mode for extracting a still image during the first mode; Exposure control means for measuring the amount of light incident on the image pickup means based on a video signal obtained from the image pickup means in the first mode, and controlling the exposure of the exposure means according to the measured value; and the amount of incident light. Gain control means for controlling the gain of the video signal obtained from the image pickup means according to the measurement value of, and the exposure of the exposure means is set to a predetermined value when the second mode is selected. And a calculation control unit for calculating and setting the gain controlled by the gain control unit based on the measured value of the incident light amount in the first mode before the second mode is selected.

[0006]

According to the above structure, in the first mode, the exposure control means controls the exposure and the gain of the video signal in accordance with the amount of incident light by the AE operation, so that a moving image is continuously obtained. When the second mode is selected, the exposure is set to a predetermined value, and the gain of the video signal suitable for the second mode is immediately calculated based on the amount of incident light measured in the first mode. It Therefore, from the first mode to the second
Even when the response of the AE operation is delayed when the mode is shifted to the mode, the conditions for the still image such as exposure and gain can be immediately set, and a good still image can be quickly captured.

[0007]

1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a lens, 2 is an iris that adjusts the amount of light from the lens 1, 3 is a CCD, 4 is a driver that drives the iris 2 according to a command from the CPU 11,
5 is a CDS (CO
RREATION DOUBLE SAMPLING)
A circuit, 6 is an AGC circuit that is controlled by the CPU 11 and adjusts the output signal level of the CCD 3, 7 is an AD converter, 8 is a camera processor that converts the output of the CCD 3 into a video standard signal, and 9 is a recorder that records the video signal.
Reference numeral 10 is a timing generator that generates a timing signal for operating the CCD 3, the CDS circuit 5, the AD converter 7, etc., 11 is a CPU that controls the system, 12 is a shutter button that triggers an image of one frame, 1
3 is an output terminal for outputting the signals of the recorder 9 and the camera, 1
Reference numeral 6 is a register for setting the gain of the AGC circuit 6 by the CPU 11.

Next, the operation will be described. An object image (not shown) is input through the lens 1, focused by the iris 2 to a light amount suitable for the CCD 3, and then focused on the CCD 3 to convert the light into an electric signal to become a video signal. This video signal has its reset noise removed by the CDS circuit 5, and is then input to the AGC circuit 6 to register 1
It is amplified to an appropriate range according to the gain set to 6. The amplified video signal is converted into a digital video signal by the AD converter 7. This digital video signal is a signal of about 10 bits and is input to the camera processor 8 to become a standard video signal by an internal color separation circuit, a gamma circuit, an encoding circuit for a video signal, and the like. This video signal is input to a recorder 9 which is a recording device and recorded on a recording medium such as a magnetic tape. At this time, the video signal is output from the output terminal 13. Further, when reproducing the recorder 9, a reproduction signal is output from the output terminal 13.

The timing generator 10 includes a CCD 3
Is supplied with a reset timing and a clock for determining the accumulation time, the CDS circuit 5 is supplied with a sample timing, the AD converter 7 is supplied with a sampling clock, and the camera processor 8 is supplied with a synchronization signal.

When the camera is normally photographed by the CCD 3, the amount of light is measured inside the camera processor 8, the data is read by the CPU 11, and the iris 2 is moved so that the amount of light entering the CCD 3 is an appropriate amount. Alternatively, feedback control is performed in which the CPU 11 sets the gain in the register 16 and controls the gain of the AGC circuit 6 so that the input range to the AD converter 7 becomes an appropriate range. Since this feedback control is performed after detecting the signal input to the camera processor 8, the response cannot follow a too fast change. The measurement of the light quantity is performed for 1 V (within the vertical period), and the control is performed in the next vertical period.

When the shutter button 12 is pressed to capture only one still image in the moving image mode, a trigger signal is fetched by the CPU 11. As a result, the CPU 11 causes the timing generator 10 to perform timing such that the electronic shutter speed of the CCD 3 is shortened by one frame,
For example, a command is issued to generate a timing that is 1/250 seconds.

At the same time, the CPU 11 calculates the gain of the AGC circuit 6 by using the parameters in the moving image mode up to that point, and makes the gain of the AGC circuit 6 in the still image mode four times that before. The CPU 11 gives the gain to the register 16 to optimize the capture of one frame at that moment, that is, the above-mentioned 1/250 second frame. In the moving image mode after capturing a still image, the gain in the original moving image mode is set in the register 16 in order to restore the gain of the AGC circuit 6 to the state in the original moving image mode. Based on the above, it is possible to capture an image in an optimum state in both moving image and still image modes.

FIG. 2 is a diagram for explaining the timing of the above-mentioned operation. In the figure, (a) shows the exposure time of the CCD 3, (b) shows the moving image and still image modes, and (c) shows the gain of the AGC circuit 6.

FIG. 3 is a diagram for explaining the control operation together with FIG. 2 in more detail. Reference numeral 14 denotes a camera signal processing circuit provided in the camera processor 8, which performs gamma correction of luminance and color signal processing. Reference numeral 15 is a photometric circuit provided in the camera processor 8, which measures the amount of light from the brightness information obtained from the CCD 3. As described above, while performing photometry in the moving image mode, the shutter button 12 is pressed, and in the next vertical period, that is, in the timing of # 2 in FIG.
When the gain is determined, and when returning to the moving image mode in the next vertical period, that is, the timing of # 3, the photometric information at the time of moving image before the still image mode is stored and that value is used. At the timing of # 4, the normal feedback control is resumed for the first time.

FIG. 4 shows a second embodiment of the present invention. First
In this embodiment, the gain of the AGC circuit 6 is changed during a still image, but in this embodiment, the digital video signal from the AD converter 7 is increased by a multiplier. For this purpose, the A
A multiplier 17 to which the output of the D converter 7 is input and a register 18 for setting a coefficient in the multiplier 17 are provided.

When the shutter button 12 is pressed to capture a still image while the timing generator 10 is operating in the moving image mode, the CPU 11 causes the timing generator 10 to be in the still image state from the next frame and the CCD 3
The timing of the electronic shutter is accelerated and the reading is performed in the accumulation time of 1/250 seconds as described above. At this time, the CPU 11 sets a gain of 4 times that of the moving image mode in the register 18 and inputs the gain into the multiplier 17, so that the digital video signal can be input into the camera signal processing circuit 14 as an appropriate range.

In each of the embodiments, the gain of the AGC circuit 6 is changed, and the gain is changed by the multiplier 17. However, if an iris having a high response speed can be realized, the aperture of the iris is set to 1. The frame period may be changed.

[0018]

As described above, according to the present invention,
When you try to capture one frame as a still image during continuous shooting of moving images with a video camera or the like, you can quickly determine the shooting conditions for only one still image by using the AE function that the video camera originally has. Not only is it possible to perform various correction processes for making a still image look clearer, for example, noise suppression process, knee process correction, gamma process, contour enhancement process, and the like.

[Brief description of drawings]

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

FIG. 2 is a timing chart showing the operation of the first embodiment.

3 is a block diagram showing the inside of the camera processor of FIG. 1. FIG.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 2 Iris 3 CCD 4 Iris driver 6 AGC circuit 8 Camera processor 10 Timing generator 11 CPU 12 Shutter button 13, 14 Camera signal processing unit 15 Camera process photometry circuit 16, 18 Register 17 Multiplier

Claims (3)

[Claims] 1. An image pickup means for photoelectrically converting a subject image to output a video signal, an exposure means for exposing the subject image to the image pickup means, and a video signal obtained from the image pickup means for continuous processing. Signal processing means for selectively performing a first mode for obtaining a moving image and a second mode for extracting a still image during the first mode, and an image obtained from the image pickup means in the first mode. An exposure control unit that measures the amount of light incident on the image pickup unit based on a signal and controls the exposure of the exposure unit according to the measured value, and an image obtained from the image pickup unit according to the measured value of the incident light amount. Gain control means for controlling the gain of a signal, and a first mode before the second mode is selected, while setting the exposure of the exposure means to a predetermined value when the second mode is selected. Above at time An image pickup apparatus having an arithmetic control means for setting and calculates the gain to control the said gain control means based on the measurement values of Shako amount. 2. The image pickup apparatus according to claim 1, further comprising: a multiplication unit that multiplies the gain calculated by the calculation control unit and the video signal, and sends the multiplication output to the signal processing unit. 3. The exposure means changes the shutter speed according to the first and second modes, and the signal processing means changes the timing of signal processing according to the change of the shutter speed. The image pickup apparatus according to claim 1, wherein