JPS6090490A - Video camera - Google Patents

Abstract

PURPOSE:To obtain white balance by gating only the center part out of modulation output of an image signal, operating an alarm circuit by the output and copying a white object without using a diffusion plate. CONSTITUTION:Outputs of color difference signals from color difference circuits 4 and 5 are added to a modulation circuit 9, thereby obtaining modulation outputs. Only the center part out of the modulation output is taken out by a gate circuit 10. After the center part is wave-shaped by a shaping circuit 11, the result is supplied to a level detector 12. If a redish object image is picked up, the level detector 12 outputs a detected signal, which is added to an alarm circuit 13 because the redish object image exceeds the reference of a white level at the level detector 12. At this time, the alarm that the detection signal is unsuitable for the reference data of white balance adjustment is given. In such a manner, white balance is obtained by using the white object as reference data without using the diffusion plate.

Description

[Detailed description of the invention] Industrial applications TECHNICAL FIELD The present invention relates to a video camera.

Conventional configuration and its problems Conventionally, when adjusting the white balance in this type of video camera, in order to make the adjustment easier, a translucent cap or a piece of paper that can be inserted into the lens system was used instead of a white piece of paper. A diffuser plate is used to adjust the white balance. In this case, using a diffuser plate is more advantageous than using a cap, but the spectral characteristics of the diffuser plate itself have the disadvantage that the color balance is disrupted depending on whether it is in the optical path to the image pickup tube or not. Even if a correction circuit is used to correct this, sufficient accuracy cannot be maintained due to variations in the image pickup tube and irregularities in the diffuser plate.

OBJECTS OF THE INVENTION The present invention provides a video camera that eliminates the drawbacks of the above-mentioned conventional examples and that can achieve white balance without using a diffuser.

Structure of the Invention In order to achieve the above object, the present invention provides a circuit that gates only the central part of the output of a modulation circuit that modulates the color difference output, excluding the peripheral part, a circuit that shapes the waveform of the gate output, and the output thereof. This camera is equipped with an alarm circuit that operates when the camera takes a picture of a white subject without using a diffuser to achieve white balance.

A warning is displayed when the white balance is adjusted for a colored subject.

Description of examples An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is an image pickup tube with a stripe filter attached to the front, 2 is a RlY, B signal separation circuit connected to the image pickup tube 1, 3 and 3' are gain control circuits, 4 and 6
1 is a color difference circuit, 6 and 7 are smoothing circuits, 8 is an automatic white balance circuit, and 9 is a modulation circuit.

1o is a gate circuit that increases the modulation output 11j and gates only the central portion and excludes the peripheral portion; 11 is a shaping circuit that converts high frequency components to low frequency components and shapes the input waveform; 12 is a level detector; Detects the signal level when capturing images of objects other than white objects. Reference numeral 13 denotes an alarm circuit, which operates in response to a signal from the level detector 12.

In the above configuration, if circuits 10 to 13 are ignored, there is no difference from the conventional white balance circuit.

However, the conditions for maintaining white balance without using a diffuser will be regulated.

Therefore, the present invention provides circuits 10 to '13, extracts only the central portion of the output from the modulation circuit 9 using the gate circuit 10, shapes the waveform in the shaping circuit 11, and outputs the output from the modulation circuit 9 to the level detector 12.
It is configured so that it is applied to

Here, if a reddish subject is imaged, the white level standard in the level detector 12 will be exceeded, so a detection signal is output from the level detector 12 and applied to the alarm circuit 13, and the sample is used for white balance adjustment. A warning will be issued to the effect that this is inappropriate. On the other hand, when a white object is used as a sample, no signal is output to the level detector 12, and the white balance can be adjusted as is.

That is, when performing white balance without using a diffuser, a white object is always imaged as a sample, and this is used to perform automatic white balance and the circuit 8 performs white balance.

Furthermore, when a color temperature conversion filter that is set for outdoor use is used indoors, even if a white subject is imaged, the output will be equivalent to red, exceeding the level detector 120 level and activating the alarm circuit 13, so the filter It can also warn of misuse.

Effects of the Invention As described above with reference to the embodiments, according to the present invention, since a white balance warning circuit is provided, it is possible to easily determine the white balance setting conditions, that is, the quality of the sample.

Furthermore, the present invention has the advantage that a diffuser plate is not required, making the configuration of the camera easier.

[Brief explanation of drawings]

The drawing is a block diagram of essential parts of a video camera according to an embodiment of the present invention. 1... Image pickup tube, 2... Signal separation circuit, 3
, 3'...gain control circuit, 4, 6...
...Color difference circuit 6.7...Smoothing circuit, 8.
... Automatic mortar (lance circuit 9 ... Modulation circuit, 1o ... Gate circuit, 11 ... Shaping circuit, 12 ... Level detection circuit, 13 ... ...Alarm circuit.

Claims (1)

[Claims] A gate circuit that gates only the center part of the modulated output of the video signal, a circuit that shapes the waveform of that output, and a warning when a signal that exceeds the white standard level is output to the waveform-shaped output as well. A video camera equipped with a circuit.