JPH07336588A - Television camera - Google Patents

Abstract

PURPOSE:To obtain a natural video signal without shock due to gain switching even in the on-air state by changing continuously a gain of a video signal in a prescribed time constant. CONSTITUTION:When a gain is changed, a discrete gain control signal 2a corresponding to,e.g. 0dB, +9dB, +18dB respectively is fed to a gain control signal arithmetic processing circuit 3. The arithmetic circuit 3 generates a gain control signal 3a changing continuously up to a supplied gain control value from a current gain control value based on the supplied discrete gain control values by the software processing and outputs the gain control signal 3a to a gain variable circuit 1. Thus, since the gain of the gain variable circuit 1 is changed continuously at a prescribed time constant at gain switching, a natural video signal without shock at gain switching is obtained. Then a video input 1a is amplified by the gain of the gain variable circuit 1 changed continuously and outputted as an output signal 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of video signal gain control in a television camera.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional video signal gain switching circuit, and FIG. 3 shows a transient response characteristic at the time of gain switching. In this operation, when the gain changeover switch 2 is switched, discrete gain control signals (gain control values) 2a corresponding to 0 dB, +9 dB, and +18 dB are sent to the gain variable circuit 1, and the gain of the gain variable circuit 1 is changed. ,
It changes discretely like 0 dB, +9 dB, and +18 dB. Here, the video signal input 1a is amplified by the gain of the switched gain variable circuit 1 and is output as the video signal output 1b. At this time, as shown in the transient response characteristic of FIG. 3, when the gain changeover switch 2 is switched, the gain of the gain variable circuit 1 is instantaneously switched, so that the video signal output 1b becomes a shocked and unnatural video signal. Will end up.

[0003]

In the above-mentioned prior art,
When the gain of the video signal of the television camera is switched, the gain is discretely switched, for example, 0 dB, +9 dB, and +18 dB, resulting in an unnatural video signal having a switching shock. Therefore, there is a drawback that the gain cannot be switched during ON AIR. An object of the present invention is to eliminate these drawbacks and to provide a gain switching circuit in a television camera, which can obtain a natural video signal without a shock even when the gain of the video signal is switched.

[0004]

In order to achieve the above object, the present invention is provided with means for continuously varying the gain of a video signal with a predetermined time constant when switching the gain of the video signal of the television camera. It is a thing.

[0005]

As a result, when the gain of the video signal of the television camera is switched, the gain of the video signal continuously changes with a predetermined time constant, so that a natural video signal without a shock at the time of gain switching can be obtained. , Gain can be switched even in ON AIR.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG. FIG. 1 is a block diagram of a video signal gain switching circuit according to an embodiment of the present invention. This operation is 0d when the gain changeover switch 2 is changed.
Discrete gain control signals (gain control values) 2a corresponding to B, +9 dB, and +18 dB, respectively, are sent to the gain control signal arithmetic processing circuit 3. Here, the gain control signal arithmetic processing circuit 3, as will be described later, is based on the supplied discrete gain control value and continuously changes from the current gain control value to the supplied gain control value. Three
a is generated by software processing, and the gain control signal 3a is output to the gain variable circuit 1. As a result, the gain of the variable gain circuit 1 is such that when the gain is switched, the gain of the video signal continuously changes with a predetermined time constant, so that a natural video signal without a shock at the time of gain switching can be obtained. The signal input 1a is amplified by the gain of the gain variable circuit 1 which continuously changes, and is output as a video signal output 1b.

Hereinafter, the operation of the gain control signal arithmetic processing circuit 3 will be described in detail with reference to FIG. First, the gain control signal arithmetic processing circuit 3 reads the gain control value G1 of the gain control signal 2a that is switched and selected by the gain changeover switch 2 and is output. Next, this gain control value G1 and the current gain control value G of the gain control signal arithmetic processing circuit 3
2 are compared to determine whether there is a difference. If there is a difference, the output gain control value G of the gain control signal 3a output from the gain control signal arithmetic processing circuit 3 is set to G = G2, and G1 and G2 are compared. Where G1> G2
In the case of, the output gain control value G = G + ΔG is calculated and output, and the operation waits for Tm sec. Next, it is determined whether or not G = G1, and if G <G1, the output gain control value G = G
Calculate and output + ΔG, and wait for Tm sec. This operation is repeated until G = G1 is satisfied.

When G1 <G2, the output gain control value G = G-ΔG is calculated and output, and the operation waits for Tm sec.
Next, it is determined whether or not G = G1, and if G> G1, the output gain control value G = G-ΔG is further calculated and output, and T
Wait for m sec. This operation is repeated until G = G1 is satisfied. As a result, the gain changeover switch 2 is changed, for example, from 0 dB to +18 dB, from +18 dB to +9 dB.
When switched to, the gain variable circuit 1
Gain control signal (output gain control value G) that continuously changes from 0 dB to +18 dB and from +18 dB to +9 dB
3a is supplied, and as shown in the transient response characteristic of FIG. 4, the gain of the variable gain circuit 1 continuously changes with a predetermined time constant, so that a natural video signal without a gain switching shock can be obtained. . It is needless to say that the gain control signal arithmetic processing circuit 3 in the present embodiment is not limited to the software configuration and can be realized by the existing hardware configuration.

[0009]

According to the present invention, a function of continuously and smoothly switching the gain of a video signal can be realized. Therefore, it is possible to obtain a natural video signal without a gain switching shock even in ON AIR.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video signal gain switching circuit according to the present invention.

FIG. 2 is a block diagram showing a conventional video signal gain switching circuit.

FIG. 3 is a diagram showing a transient characteristic when switching a conventional video signal gain.

FIG. 4 is a diagram showing transient characteristics when switching a video signal gain according to the present invention.

FIG. 5 is a flowchart showing the operation of the gain control signal arithmetic processing circuit of the present invention.

[Explanation of symbols]

1: gain variable circuit, 2: gain changeover switch,
3: gain control signal arithmetic processing circuit, 1a: video signal input, 1b: video signal output, 2a: discrete gain control signal, 3a: continuously changing gain control signal.

Claims (1)

[Claims] 1. A television camera comprising means for continuously varying the gain of a video signal with a predetermined time constant when switching the gain of the video signal of the television camera.