JPS6119285A - Iris control method of video camera - Google Patents

Abstract

PURPOSE:To obtain an always excellent picture by weighting a luminance signal at each H period to form an iris control signal and opening or closing smoothly an iris in response to the level of the control signal. CONSTITUTION:A horizontal parabolic wave having a period equal to 1H period is generated from a color blurring correcting signal generating circuit 7, the horizontal parabolic wave is fed to an adder circuit 10 through a buffer 8, the signal is subject to addition of a vertical gate signal from an input terminal 9, the result is inverted (11) and fed to a luminance signal processing circuit 6 as an iris gate signal G. The circuit 6 applies weighting by the signal G to a luminance signal Y, the luminance signal Y is extracted by a prescribed period each at each H period and the extracted signal is subject to pieak detection to form the iris control signal S. Then in iris control circuit 12 controls an iris drive motor 13 according to the change in the level of the signal S to adjust the closing/opening amount of iris blades.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to an iris control method for a video camera.

[Background of the invention]

Video cameras that use an automatic iris system control the amount of opening and closing of the iris according to changes in the brightness signal level.
This allows the amount of print to be automatically adjusted by simply pointing the camera at the subject.

In the conventional iris control method, a rectangular gate signal with a period equal to the horizontal scanning period is used to give a certain weight to the video signal and extract the video signal for a predetermined period for each horizontal scanning period.
However, according to such an iris control method, the entire iris control signal for controlling the opening/closing amount of the iris is generated by peak detecting the extracted video signal.

When an object such as reflected light from the sun or a light crosses the imaging surface horizontally, a high-level portion of the luminance signal suddenly appears or disappears at the rising edge or falling edge of the gate signal. Therefore, the level of the iris control signal changes suddenly, and the amount of opening and closing of the iris changes rapidly.

When the iris opens and closes rapidly in this way, the image obtained at this time may appear unnatural because it suddenly changes from a bright state to a dark state, or from a dark state to a bright state suddenly. It ends up feeling like this. Ota. Even though you are shooting a bright screen, if a high-brightness subject comes near the edges of the screen, which correspond to the rising and falling portions of the gate signal, the reproduced image will become dark. There was a drawback.

[Purpose of the invention]

An object of the present invention is to provide an iris that can operate smoothly without suddenly opening and closing the iris even when a high-brightness subject enters or leaves one screen from the horizontal direction of the video camera, and can always obtain good images. The objective is to provide a control method.

[Summary of the invention]

To achieve this objective, the present invention provides a weighted gate signal that corresponds to one horizontal scanning period, has a maximum amplitude approximately in the middle of the period, and has a minimum amplitude at the beginning and end of the period. The iris control signal is generated by weighting the luminance signal for each horizontal scanning period, and the opening/closing amount of the iris is controlled according to the level of the iris control signal, so that the rising edge of the gate signal on the screen is 9. Even if a high-luminance object comes to a part where the falling edge is near 9, the iris blades are not moved violently and the opening/closing operation is performed smoothly.

[Embodiments of the invention]

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

FIG. 1 is a block diagram showing the iris control method according to the present invention, in which 1 is a lens block, 2 is an image pickup tube, 3 is an amplifier circuit, 4 is a separation circuit, 6 is a luminance signal processing circuit, and 7 is a color unevenness correction circuit. A signal generation circuit, 8 a buffer, 9 a vertical gate signal input terminal, 10 an addition circuit, 11 an inversion circuit, 12
13 is an iris control circuit, 13 is an iris drive motor, and 14 is an iris control circuit.
is an iris feather.
.

When photographing, optical information from a subject passes through a lens block 1, is converted into an electrical signal by an image pickup tube 2, is amplified by an amplifier circuit 3, and then is converted into a cycloma signal C and a luminance signal Y by a separation circuit 4. separated. A part of the luminance signal Y is then supplied to the luminance signal processing circuit 6.

On the other hand, the uneven color correction signal generation circuit 7 generates a horizontal parabolic wave with a cycle equal to one horizontal scanning period, which has a minimum amplitude at the start and end positions of the 1' horizontal scanning period and a maximum level at the middle of the i period. The horizontal parabolic wave is supplied to an adder circuit 10 through a buffer 8, and after a vertical gate signal, which will be described later, supplied from an input terminal 9 is added thereto, it is inverted by a 1 inverting circuit 11 to produce an iris gate signal G. The signal is then supplied to the luminance signal processing circuit 6.

The luminance signal processing circuit 6 weights the luminance signal Y with the iris gate signal G, extracts the luminance signal y'l for a predetermined period every horizontal scanning period, and peaks the extracted luminance signal. The iris control circuit 12 detects the iris control signal S, and the iris control circuit 12 generates the iris control signal S.
The iris drive motor 13 is controlled according to the change in the level of the iris blade 14, and the opening/closing amount of the iris blade 14 is adjusted.

Here, FIG. 2 shows three horizontal parabola waves generated by the one-color unevenness correction signal generation circuit 7. As shown in the figure, the horizontal parabolic wave changes in an arc in synchronization with the horizontal scanning period, and its period T is 63 μS.

From this, the iris gate signal G supplied from the inversion circuit 11 to the luminance signal processing circuit 6 is as follows.

Since the phase is inverted from that of the horizontal parabolic wave, the portion corresponding to the start and end 9 of each horizontal scanning period has the minimum amplitude, and the portion corresponding to the middle of the period has the maximum amplitude.

Therefore, in the luminance signal processing circuit 6, the luminance signal Y
The maximum weighting is given in the middle of the horizontal scanning period, and the weighting becomes smaller toward both ends of the period.

As a result, even when a high-brightness subject enters or exits at both horizontal ends of the screen during shooting, the iris control signal does not change suddenly like in the past.

Therefore, the iris blade 14 can be smoothly opened and closed. Furthermore, since the iris pattern movement has become smoother, deterioration in image quality due to a high-brightness subject is reduced, and it is possible to obtain a natural-looking and good image.

FIG. 3 is a circuit diagram showing an example of a circuit from the buffer 8 to the inversion circuit 11'i in FIG.

Q2 is a transistor, R and -R7 are resistors b Dl +D
t is a diode, 16 is a terminal connected to the output terminal of the uneven color correction signal generation circuit 7, 9a and 9b are input terminals corresponding to the vertical gate signal input terminal 9 (FIG. 1), and 17 is a luminance signal processing circuit 6. This is the terminal connected to the input terminal of

The horizontal parabolic wave from the color unevenness correction signal generation circuit 7 is supplied to the terminal 16, and is connected to the transistor Q8 and the resistors R1, R,
), resistor Rm sR4*R5
and diodes D, , D, are supplied to an adder circuit.

Here, a first vertical gate signal synchronized with the vertical scanning period and having a shape similar to a horizontal parabolic wave is supplied to the input terminal 9α, and one input terminal 15A is supplied with a first vertical gate signal synchronized with the vertical scanning period. A second vertical gate signal having a sawtooth waveform is supplied.

Then, the horizontal parabolic wave and the first wave. The second vertical gate signal is added and the transistor Qt (!: resistors R6-R7
The iris gate signal 'G is inverted by an inverting circuit composed of the following, and is supplied to the luminance signal processing circuit 6.

As described above, in the adding circuit 10, the second vertical gate signal having nine sawtooth waves is added to the first vertical gate signal having a parabolic waveform, but by changing the shape of the sawtooth waveform, The first vertical gate signal is modified, and the vertical weighting characteristics applied to the luminance signal Y can be changed. This is normal shooting.

This is done to control the pattern in accordance with bright subjects (such as the sun and sky) appearing at the top of the screen and the bottom being relatively dark.

The iris gate signal G thus formed has a large amount of weighting at approximately the center of one screen, and a small amount at the periphery of one screen. Therefore, not only in the horizontal direction of the screen, but also wherever a high-brightness subject enters the screen,
There is no sudden change in the iris control signal S generated by the luminance signal processing circuit 6, and the iris blades 14 are smoothly opened and closed.

In the above embodiment, the gate signal has a parabolic wave shape, but the present invention is not driven by this; the amplitude gradually increases until the middle part of the horizontal scanning period, and gradually increases after the middle part. Any signal whose amplitude decreases may be used.

〔Effect of the invention〕

As explained above, according to the present invention, a luminance signal is generated using a gate signal that corresponds to one horizontal scanning period and has a maximum amplitude at approximately the middle of the period and a minimum amplitude at the beginning and end of the period. to form an iris control signal,
Since the opening/closing amount of the iris is controlled according to the level of the iris control signal, even if a high-brightness subject enters or leaves the screen in the horizontal direction, the iris opens and closes smoothly and always provides a natural-looking image. The playback image can be completely written.

It is possible to provide all methods for controlling the iris of a video camera with excellent functions, except for the second-level problems of the prior art.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the iris control method for a video camera according to the present invention, FIG. 2 is a waveform diagram showing a horizontal parabolic wave generated by the color unevenness correction signal generation circuit of FIG. 1, and FIG. The figure is a circuit diagram showing an example of a circuit that forms an iris gate signal. 6... Luminance signal processing circuit 7... Color unevenness correction signal generation circuit 8... Buffer 10... Power 1] calculation circuit 1
1... Inversion circuit 12... Iris control circuit 13... Iris drive motor 1A... Iris vane

Claims (1)

[Claims] The video signal is weighted with a gate signal with a period equal to the horizontal scanning period, the video signal is extracted for a predetermined period for each horizontal scanning period to form an iris control signal, and the opening and closing of the iris is controlled by the iris control signal. In the iris control method for a video camera, the gate signal is a signal whose amplitude sequentially increases up to the middle part of the horizontal scanning period and whose amplitude sequentially decreases from the middle part. Iris control method.