JPH07131701A - Television camera device - Google Patents

Abstract

PURPOSE:To correct automatically a luminous quantity change such as an F drop by storing a luminous quantity change characteristic of a zoom lens in advance and cancelling a luminous quantity change in the zoom lens depending on a focal distance. CONSTITUTION:A luminous quantity change characteristic of a zoom lens with respect to a focal distance expressed in digital data is stored in advance in a characteristic data memory 4. A focal distance detection section 2 detects a focal distance of the lens 1 to provide an output of a focal distance detection signal Fd. A gain control section 3 receives the detection signal Fd and automatically data from the memory 4 and provides an output of a gain control signal Cg to cancel an F drop of the lens 1 to a variable gain amplifier 6. A light of an object made incident through the lens 1 is converted into an image pickup signal by an image pickup element 5 and the signal is given to the amplifier 6. The amplifier 6 amplifies the image pickup signal and its amplification factor depends on the signal Cg. The image pickup signal whose F drop is corrected by the amplifier 6 is subject to prescribed processing by a video signal processing section 7 and the processed signal is outputted as a television video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television camera device, and more particularly to a television camera device capable of gain control when amplifying an image pickup signal.

[0002]

2. Description of the Related Art Generally, in a television camera, a subject image formed through an image pickup lens system is used as an image pickup tube or a CCD.
An image pickup device such as the above converts the signal into an electric signal, amplifies the image pickup signal, and performs signal processing to obtain an output video signal. However, in reality, the image pickup signal level fluctuates due to changes in the illuminance of the subject, and various proposals have been made to correct this and keep the video signal level constant.

First, a structure has been proposed in which the image output level is maintained constant even in low illuminance by an automatic diaphragm for adjusting the amount of light incident on the image pickup tube and automatic gain adjustment for amplifying the image pickup signal (Japanese Patent Laid-Open No. 2000-242242). 56-93495). Similarly, a configuration has been proposed in which the gain of the amplifier is controlled according to the amount of incident light so that a good output level can be obtained regardless of whether the illuminance is low or high (Japanese Patent Laid-Open No. 63-215173).

Further, a configuration has been proposed in which an optimum video signal is obtained by adjusting the shutter amount of the CCD image pickup device and the gain of the amplifier at the subsequent stage (Japanese Patent Laid-Open No. 4-32476).
7 publication).

[0005]

In a television camera, a zoom lens is generally used as an image pickup lens. The zoom lens changes the focal length f (or magnification) by changing the mutual distance between the lens groups. The state in which the focal length f is the smallest is called the wide-angle end, and the state in which it is the largest is called the telephoto end.

However, when this zoom lens is used, as shown in FIG. 5, there is a phenomenon in which the amount of light called F drop lowers in the area near the telephoto end, and as a result, the image output level of the television camera also lowers. Occurs.

In order to prevent this phenomenon, the diameter of the first lens group of the zoom lens may be increased, but this is not practical in consideration of the size and weight of the entire lens. For this reason, conventional television cameras often allow a certain amount of F drop and are put to practical use.

An object of the present invention is to provide a television camera device capable of automatically correcting an F drop generated on the telephoto end side of a zoom lens and maintaining a video output level.

[0009]

In a television camera apparatus according to the present invention, a characteristic of a light quantity change of a zoom lens is stored in advance, and a variable gain amplifier is used so as to cancel the light quantity change of the zoom lens according to a focal length. It changes the gain of.

That is, the television camera apparatus according to the present invention detects the focal length of the zoom lens, which is provided in the optical path of the subject light incident on the image pickup element and which can continuously change the focal length. Focal length detection means, characteristic data storage means for storing, as digital data, the light amount change characteristic of the subject light with respect to the focal length of the zoom lens, and the zoom lens based on the focal length of the zoom lens and the characteristic data. And a gain control means for controlling the gain of the variable gain amplifier so as to cancel the change in the light amount due to.

[0011]

The light quantity change characteristic with respect to the focal length of the zoom lens is stored in the characteristic data storage means, and the light quantity change characteristic data is read from the detected value of the zoom lens focal length.
The gain of the variable gain amplifier is controlled so as to correct the change in the image pickup signal due to the change in the light amount. As a result, a change in the amount of light such as F drop of the zoom lens is automatically corrected.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a television camera device according to the present invention, and FIG. 2 is a block diagram showing details of the gain control section 3.

In FIG. 1, the zoom lens 1 is used in a television camera, and the focal length f can be continuously changed. For example, the focal length is 16-160 mm for studios and 24-400 m for relays.
m or more is used.

The focal length detection unit 2 detects the focal length f of the zoom lens 1 and outputs the focal length detection signal Fd to the gain control unit 3.
Output to.

The gain control section 3 inputs the focal length detection signal Fd and the characteristic data from the characteristic data memory 4 to generate a gain control signal Cg for canceling the F drop of the zoom lens 1, and a variable gain amplifier. Output to 6.

The characteristic data memory 4 includes a zoom lens 1
Characteristic data indicating a change in the amount of incident light with respect to the focal length is stored in advance.

As shown in FIG. 2, the gain control section 3 has a function of A /
It is composed of a D conversion unit 31 and a calculation unit 32, and the calculation unit 32 is A
The focal length detection signal Fd converted into a digital signal by the / D converter 31 and the characteristic data are input to generate a gain control signal Cg.

The subject light incident through the zoom lens 1 is converted into an electric image pickup signal by the image pickup device 5.
As the image pickup device 5, an image pickup tube, a CCD solid-state image pickup device, or the like is used.

The image pickup signal from the image pickup device 5 is amplified by the variable gain amplifier 6, and its gain is determined by the gain control signal Cg from the gain control section 3. Variable gain amplifier 6
The F-drop corrected image pickup signal is subjected to predetermined processing in the video signal processing unit 7 and output as a television video signal.

FIG. 3 is a graph showing the relationship between the F drop of the zoom lens and the gain of the variable gain amplifier with respect to the focal length (Fd). Due to the F drop of the zoom lens 1, the amount of light incident on the image sensor 5 decreases on the telephoto side as shown in the figure, and therefore the output level of the image sensor 5 also decreases on the telephoto side. To correct this output level drop,
As shown in the figure, the gain of the variable gain amplifier 6 may be increased so as to cancel the F drop effect on the telephoto side.

To this end, the characteristic data memory 4 stores in advance the characteristic data of the F drop of the zoom lens 1, that is, the characteristic data of the level change of the image pickup signal with respect to the zoom lens focal length (Fd). Using this characteristic data, the gain control unit 3 performs gain control that cancels the above F drop effect.

FIG. 4 is a partial flow chart showing the operation of this embodiment.

In the figure, the gain controller 3 inputs a detection signal Fd indicating the focal length of the zoom lens 1 from the focal length detector 2 through the A / D converter 31 (S10).
1).

Subsequently, it is determined whether or not F drop occurs at the focal length indicated by the input detection signal Fd (S10).
2). If no F drop occurs (N in S102)
o), reading step of focal length detection signal (S10)
Return to 1).

If the zoom lens 1 is on the telephoto side to cause F drop (Yes in S102), the gain control section 3 reads the F drop characteristic data of the zoom lens for the focal length from the characteristic data memory 4 (S103).
Then, the calculation unit 32 of the gain control unit 3 generates a gain control signal Cg for adjusting the gain of the variable gain amplifier 6 so as to cancel the F drop and outputs it to the variable gain amplifier 6 (S104). When the gain control of the variable gain amplifier 6 for the current focal length is completed in this way, the process returns to the focal length detection signal reading step S101 again, and the above operation is repeated.

The determination as to whether or not an F drop will occur (S102) may be made by previously reading the focal length at which an F drop will occur from the characteristic data memory 4 as in the above-described example, or by making a comparison determination. Each time the distance detection signal Fd is input, characteristic data corresponding to the focal length may be read and compared and judged. In the latter case, not only the F drop but also other characteristics of the zoom lens 1 can be corrected.

[0028]

As described above in detail, in the television camera apparatus according to the present invention, the characteristic quantity storage means stores the light amount change characteristic with respect to the focal length of the zoom lens, and the detected value of the focal length of the zoom lens is stored. The change in the light amount is read from, and the gain of the variable gain amplifier is controlled so as to correct the change in the imaging signal due to the change in the light amount. With this, it is possible to automatically correct the light amount change characteristic such as F drop of the zoom lens, and it is possible to maintain the image output level in the range from the wide-angle end to the telephoto end of the zoom lens.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a television camera device according to the present invention.

FIG. 2 is a block diagram showing details of a gain control unit 3 in the present embodiment.

FIG. 3 is a graph showing the relationship between the F drop of the zoom lens and the gain of the variable gain amplifier with respect to the focal length (Fd) in the present embodiment.

FIG. 4 is a partial flowchart showing the operation of this embodiment.

FIG. 5 is a graph showing the relationship between the focal length (Fd) and the F drop of the zoom lens.

[Explanation of symbols]

 1 Zoom Lens 2 Focal Length Detecting Section 3 Gain Control Section 4 Characteristic Data Memory 5 Image Sensor 6 Variable Gain Amplifier 7 Video Signal Processing Section 31 A / D Converter 32 Calculation Section Fd Focal Length Detection Signal Cg Gain Control Signal

Claims (2)

[Claims] 1. A television camera apparatus having a variable gain amplifier for amplifying an output signal of an image pickup device, wherein the television camera device is provided in an optical path of subject light incident on the image pickup device,
A zoom lens capable of continuously changing the focal length, a focal length detecting means for detecting the focal length of the zoom lens, and a light quantity change characteristic of the subject light with respect to the focal length of the zoom lens are stored as digital data. Characteristic data storage means, and gain control means for controlling the gain of the variable gain amplifier based on the focal length of the zoom lens and the characteristic data so as to cancel the change in the amount of light by the zoom lens. Characteristic television camera device. 2. The television camera device according to claim 1, wherein the zoom lens has a characteristic that the light amount of the subject decreases on the telephoto side.