JPH0514922A - Video camera - Google Patents

Abstract

PURPOSE:To enhance indoor color reproducibility by avoiding the errorneous operation of white balance control with the manual operation of an iris. CONSTITUTION:An electric signal from a sensor 3 is processed in a signal processing circuit 4 and an encoder 5 so as to be a video signal. A white balance control circuit 6 gain-controls a chrominance signal in the signal processing circuit 4 by a color difference signal from the signal processing circuit 4 so as to keep white balance. The manual iris control circuit 7 of an iris control circuit 11 permits the stop value of the iris 2 and the control range of white balance in the white balance control circuit 6 to change in accordance with the level of a luminance signal from the signal processing circuit 4 at the time of automatic light quantity control but the control range of white balance in the white balance control circuit 6 is made to be the wide normal range when the manual operation of the light quantity control is detected by the output of a manual iris control circuit 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera having automatic and manual light amount control means and a white balance control circuit for automatically adjusting white balance.

[0002]

2. Description of the Related Art In a video camera, a white balance control circuit is essential for improving color reproducibility of a subject to be photographed. Conventionally, various white balance circuits have been proposed, but for example, the Television Society Technical Report, VOL. 1
5, No. 7, P.I. P. As disclosed in 25-30 (1991), a white balance control circuit is known in which a white component is extracted from a subject being photographed and white balance is automatically adjusted based on the white component.

[0003]

By the way, the white balance control circuit needs to accurately extract the white component. The term "white" as used herein refers to a color that should not be displayed as white because it should be displayed as white, but a color shift (light color) occurs due to a change in the color temperature of the light source. The white balance control circuit extracts the pale color component as a white component and controls the pale color to be white.

However, since there are actually light-colored subjects, the white component extraction is likely to include an error. Specifically, for example, a light yellow subject outdoors will be described. Since sunlight has a high color temperature, white becomes bluish. Therefore, when light blue is judged to be white and a white balance is achieved, good color reproduction can be obtained, but when a light yellow subject is photographed, light yellow is judged to be white, and a more bluish image is obtained. And the color reproduction deteriorates.

In order to eliminate such an erroneous operation, various judgment standards are provided in the white balance control. In the above example, outdoors is much brighter than indoors,
The illuminance is determined from the iris aperture value and the shutter speed, and when the illuminance is high, it is determined to be outdoors, and in this case, the control range of the white balance is narrowed so that the light yellow is not drawn in white. As a result, it is possible to eliminate the above malfunction.

However, such a technique does not consider a video camera having a manual iris function. Therefore, even when the iris is manually narrowed down indoors, it is judged that it is outdoors. There is a problem that the balance control range is narrowed and accurate color reproduction cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a video camera which solves such a problem, prevents erroneous operation of white balance control and realizes good color reproduction even during manual iris operation. .

[0008]

In order to achieve the above object, the present invention provides a manual iris detection circuit, and preferentially controls the white balance control range according to the output of the manual iris detection circuit.

[0009]

[Operation] The manual iris detection circuit detects a manual operation of iris control. When a manual operation is detected by this, the white balance control range is forcibly set to the normal control range, and the white balance control operation is performed within this control range. Therefore, even if the iris is stopped down indoors by manual operation, good color reproduction can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a video camera according to the present invention, in which 1 is a lens, 2 is an iris, 3 is a sensor, 4 is a signal processing circuit, 5 is an encoder, 6 is a white balance control circuit, and 7 is a white balance control circuit. Is a manual iris detection circuit, 8
Is a driver, 9 is an aperture value detection circuit, 10 is a manual iris control circuit, and 11 is an iris control circuit.

In FIG. 1, an optical signal input through the lens 1 is adjusted in light quantity by the iris 2 and then converted into an electric signal by the sensor 3. This electric signal is subjected to processing such as gain adjustment, gamma processing, color difference signal processing, etc. in the signal processing circuit 4, and then supplied to the encoder 5 and converted into, for example, an NTSC video signal.
On the other hand, the white balance control circuit 6 extracts a white component using the color difference signals (RY) and (BY) output from the signal processing circuit 4, and the white component of the signal processing circuit 4 is extracted by this white component. Gain control of the blue (B) signal and the red (R) signal is performed so that white balance can be achieved. As a result, the encoder 5 generates a video signal with good color reproducibility.

Further, the iris control circuit 11 is supplied with a luminance signal Y output from the signal processing circuit 4 and a manual control signal output from the manual iris control circuit 10, and responds to the level of the luminance signal and the manual control signal. The aperture value of the iris 2 is controlled by the iris 2, but in this embodiment, the iris control circuit 11 is provided with the driver 8 and the manual iris detection circuit 7.

The manual iris detection circuit 7 generates an aperture value control signal according to the luminance signal Y output from the signal processing circuit 4 and the manual control signal output from the manual iris control circuit 10, and supplies it to the driver 8. Although the aperture value of the iris 2 is controlled by the manual iris control circuit 10, when the manual control signal is supplied from the manual iris control circuit 10, the manual operation detection signal indicating that the manual operation is performed is supplied to the white balance control circuit 6.

The aperture value detection circuit 9 detects the aperture value of the iris 2. The white balance control circuit 6 calculates the illuminance from the aperture value information output from the aperture value detection circuit 9 when taking the white balance. When the illuminance is high, it is determined that the image is taken outdoors, and the white balance control range is controlled. However, when the manual operation detection signal is supplied from the manual iris detection circuit 7, the white balance control range is set to the normal range.

FIG. 2 shows an example of the white balance control range for the color temperature of the object. In the same figure, in normal shooting or in manual iris operation mode, 230
White balance control is performed in a normal color temperature range of 0 ° K to 8000 ° K, and automatic exposure control is performed, and white balance control is performed in a narrow color temperature range of 5000 ° K to 7000 ° K only when the illuminance is high. Is performed.

In this way, in this embodiment, even if the iris is manually operated indoors, the control range of the white balance is not narrowed, so that good color reproduction can be obtained.

[0017]

As described above, according to the present invention,
When the iris control is manual, the white balance control range cannot be narrowed, so that good color reproducibility can be obtained even when the iris is manually closed indoors.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing a white balance control range with respect to color temperature.

[Explanation of symbols]

 2 Iris 6 White balance control circuit 7 Manual iris detection circuit 9 Aperture value detection circuit 10 Manual iris control circuit 11 Iris control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Tarumi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi Imaging Information Systems Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A video camera in which the control range of the white balance is controlled according to the control amount of the light amount control means, wherein the white balance control range is detected by detecting a manual operation of the light amount control. A video camera provided with means for canceling the control of.