JP2000125210A - Video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a dynamic range of a sensor from getting smaller than that of the video camera whose frame rate is fixed, in the case that the frame rate is selected lower in the video camera whose frame rate can be changed. SOLUTION: The variable speed video camera that is provided with a CCD 1 and whose frame rate is variably adjusted is provided with a Vsub controller 7 that controls an operating point of the CCD 1, and the Vsub controller 7 changes the operating point of the CCD 1 depending on a frame rate to adjust a dynamic range of horizontal and vertical registers and a sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state imaging device (C)
CD) and a video camera that captures an image of a subject with the solid-state imaging device.

[0002]

2. Description of the Related Art Conventionally, a video camera provided with a solid-state image sensor (CCD) has been proposed. In this video camera, an image of a subject is formed on a light receiving surface of a solid-state image sensor by a photographing lens. This image is captured by the solid-state imaging device. The solid-state imaging device converts optical information of an image of a subject into an electric signal and outputs the electric signal.

This solid-state image pickup device takes in information of an image of a subject at a cycle according to a predetermined frame rate.
The cycle defined by this frame rate is usually
There are 30 frames (60 fields) per second.

[0004]

In the above-described video camera, the frame rate can be changed by switching the clock frequency of the drive timing generation circuit of the solid-state image sensor. Changing the frame rate will increase the number of frames per second,
Alternatively, it can be reduced, and increasing the number of frames can realize a high frame rate video camera.

However, even if the frame rate is changed to increase the number of frames per second, the dynamic range of the solid-state imaging device does not change accordingly.
Therefore, when the frame rate can be changed, the vertical and horizontal transfer registers are not saturated even at the highest clock frequency that can be selected.
It is necessary to set the dynamic range of the sensor.

Therefore, in this video camera,
When operating at a low clock frequency such as a normal speed of 30 frames per second (60 fields), the dynamic range of the sensor may be smaller than that of a video camera having a fixed frame rate. .

Accordingly, the present invention has been proposed in view of the above-described circumstances, and in a video camera in which the frame rate can be changed, the frame rate is fixed even when the frame rate is reduced. An object of the present invention is to provide a video camera in which a dynamic range of a sensor is not reduced as compared with a video camera.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a variable speed video camera having a solid-state image sensor and capable of variably adjusting a frame rate.
Control means for controlling the operating point of the solid-state image sensor is provided, and the control means changes the operating point of the solid-state image sensor according to the frame rate to adjust the dynamic range of horizontal and vertical registers and sensors. It is a feature.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

A video camera according to the present invention includes a CCD (solid-state imaging device) 1 as shown in FIG. An image of a subject is formed on a light receiving surface of the CCD 1 by a photographic lens (not shown). The CCD 1 captures an image of a subject, converts optical information into an electrical signal, and outputs the electrical signal.

An output signal from the CCD 1 is quantized by an A / D converter 2, converted to a normal speed by a frame rate converter 3 using a memory or the like, and sent to an encoder 4. The encoder 4 converts the signal sent from the frame rate converter 3 into a video format and outputs it. An output signal from the encoder 4 is sent to a monitor (not shown) and displayed as an image, or sent to a video recorder (not shown) and recorded on a recording medium such as a video tape.

The CCD 1 is driven by a drive clock generated by a timing generator 5. The timing generator 5 generates a driving clock with a clock corresponding to the frame rate specified by the system controller 6 and sends the driving clock to the CCD 1. That is, in this video camera, the frame rate can be freely changed via the system controller 6, and the frame rate can be changed to three times per second.
Not only normal speed shooting such as 0 frames (60 fields), but also high speed shooting with more frames per second can be performed.

The dynamic range of the CCD 1 is governed by the smallest dynamic range of each of the sensor, the vertical register, and the horizontal register. When the dynamic range of the sensor is dominant, the picture becomes a natural white clip, but when the transfer clock frequency increases, the dynamic range of the horizontal register and the vertical register becomes smaller than the dynamic range of the sensor. As a result, a so-called horizontal pulling or vertical pulling occurs as a picture, and image quality deteriorates.

Therefore, by controlling the dynamic range of the sensor in accordance with the transfer clock frequency, increasing the dynamic range at low frequencies and decreasing the dynamic range at high frequencies, an optimum dynamic range can be obtained. The control of the dynamic range of the sensor can be performed by controlling the Vsub voltage (substrate potential) of the CCD 1.

This video camera uses a Vsub of CCD1.
It has a Vsub controller 7 for controlling the voltage. The Vsub controller 7 supplies a preset optimal Vsub voltage to the CCD 1 according to the frame rate specified by the system controller 6.

The Vsub controller 7 has a data table 8 and a D / A converter 9 as shown in FIG. In the data table 8, data for generating an optimum Vsub potential at each frame rate is set, and the data is loaded to the D / A converter 9 according to the frame rate specified by the system controller 6. I do. The D / A converter 9 generates an optimum Vsub potential as an analog voltage in accordance with the data loaded from the data table 8 and supplies the analog voltage to the CCD 1.

In this way, the Vsub potential of the CCD 1 is controlled according to the frame rate. In the CCD 1, the dynamic range is increased when the transfer clock frequency is low, and the dynamic range is reduced when the transfer clock frequency is high. As a result, an optimum dynamic range can be obtained. Therefore, even when this video camera is configured as a variable speed video camera, it is possible to perform normal speed shooting with image quality comparable to a video camera with a fixed frame rate, and it is possible to perform normal speed shooting and high speed shooting. Both can be performed favorably.

[0018]

As described above, in the video camera according to the present invention, the operating point of the solid-state imaging device is changed by the control means in accordance with the frame rate, and the dynamic range of the horizontal and vertical registers and the sensor is balanced. Take
An optimal dynamic range can be obtained. Therefore, this video camera is a variable-speed video camera, and is capable of normal-speed shooting with image quality comparable to that of a fixed-frame-type video camera, and has good both normal-speed shooting and high-speed shooting. You have the freedom to do it. Therefore, it is not necessary to use two video cameras for normal speed and for variable speed (for high speed) as in the related art.

That is, the present invention relates to a video camera in which the frame rate can be changed. Even when the frame rate is reduced, the dynamic range of the sensor is smaller than that of a video camera having a fixed frame rate. It is possible to provide a video camera which is prevented from being lost.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a configuration of the video camera.

[Explanation of symbols]

1 CCD, 5 timing generator, 6 system controller, 7 Vsub controller

Claims (1)

[Claims] 1. A variable-speed video camera including a solid-state imaging device and capable of variably adjusting a frame rate, comprising a control unit for controlling an operating point of the solid-state imaging device, wherein the control unit controls the frame rate. A video camera wherein the operating point of a solid-state image sensor is changed in accordance with the change to adjust the dynamic range of horizontal and vertical registers and sensors.