JPS62159592A - Automatic white color adjuster for television camera - Google Patents

Abstract

PURPOSE:To improve an accuracy in an automatic white color adjustment by performing the white color adjustment correctly even when picking up an image under an illumination light source having a spectral characteristic which does not follow the law of the black body radiation and performing the white color adjustment generally equally to the convention when picking up the image under the illumination light source having the spectral characteristic which follows the law of the black body radiation. CONSTITUTION:An output control voltage of a non-linear amplifier 9 is selected to a level converting characteristic shown by a solid line I with respect to a mired (micro- reciprocal-degree) number. The level converting characteristic I is a generally complementary characteristic with respect to a level ratio R/Y to the mired number characteristic of a red color signal and a luminance signal and a part thereof is selected to a non-linear characteristic having a characteristic (shown by an asterisk) required for the white color adjustment when the image of an object of a fluorescent light is picked up. Similarly, the output control voltage to the mired number characteristic of a non-linear amplifier 10 is, as shown by a solid line II, selected to the non-linear level converting characteristic, as a part thereof has the characteristic shown by the asterisk required for the white color adjustment in picking up the image of the object under the illumination of the fluorescent light.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic white adjustment device for a television camera. The present invention relates to an automatic white adjustment device that performs white balance adjustment.

Conventional technology When capturing an original image of a subject with a color television camera, gain control is applied to the primary color signal or color difference signal obtained by capturing the image in order to obtain correct color reproduction in accordance with the color temperature of the illumination light source of the subject. Conventionally, automatic white adjustment devices have been known that perform the following steps to equalize the respective levels of two primary color signals and a luminance signal.

Here, the color temperature of the illumination light source of the subject is determined by, for example, making the light from the subject diffused by a diffuser plate enter two photoelectric conversion elements having different spectral characteristics, and the resulting two photoelectric conversion elements. It is detected by the level ratio of both output signals. In other words, the light incident on the charge conversion element L is an illumination light source (e.g. sunlight, incandescent lamp, etc.) that is based on black body radiation.
In the case of light from a The reciprocal of C is inversely proportional (but not inversely proportional) to a certain Mired number (=(1x106)/color temperature (K)) -
It becomes the following function. This color temperature detection voltage is converted to an appropriate level by two linear amplifiers and applied as a gain 11 control voltage to two variable gain amplifiers, respectively.

On the other hand, among the three types of signals obtained by R visualization, for example, red signal (R), blue signal (B), and luminance signal @ (Y),
Level ratio R/Y of red signal and 1 degree signal (unit: dB)
shows a characteristic proportional to the Mired number of the illumination light source as shown by the solid line in FIG. The above Mired number does not show an inversely proportional relationship to the Mired number as shown by the solid line in Figure 5 (B).The above two variable gain amplifiers are supplied with the above red signal and blue signal separately. The red signal is supplied to the first
The variable gain (q) of the amplifier is determined by converting the color temperature detection voltage having the characteristics shown in Fig. 4 to the variable gain (Δ) shown in Fig. 6 (Δ) using the first linear amplifier.
The gain of the second variable gain amplifier to which the blue signal is supplied is controlled by the control voltage obtained by converting the characteristic to be inversely proportional to the Mired number shown by the solid line. The output primary color signals (red signal and The level of the portrait signal @) can be made equal to the level of the luminance signal.

Problems to be Solved by the Invention However, the above-mentioned conventional automatic white adjustment device is based on the premise that the illumination light source is a light source with spectral characteristics that comply with the law of blackbody radiation; When the light source has spectral characteristics that do not follow the law of radiation (for example, a fluorescent lamp), the level ratios R/Y and B/Y are expressed as shown in FIGS. 5 (△) and (B), respectively, with respect to the Mired number. Therefore, the control I lightning voltage to be supplied to the first and second variable gain amplifiers should be the value shown by the stars in FIGS. 6(A) and (B). Nevertheless, Figure 6 (△),
Because of the different shifts on the solid line in (B), there was a problem in that white balance adjustment (automatic white adjustment) was not successful.

Therefore, the present invention is designed to achieve white balance even for typical light sources that are frequently used as illumination light sources (e.g. fluorescent lamps) among light sources with spectral characteristics that do not follow the law of blackbody radiation. An object of the present invention is to provide an automatic white adjustment device for a television camera that solves the problem in item 1 by passing a color temperature detection voltage through a nonlinear level conversion circuit.

Means for Solving the Problems To achieve the above object, the automatic white adjustment device for a television camera according to the present invention includes color temperature detection means.

It consists of first and second variable gain amplifiers, first and second level conversion circuits, and each of the first and second level conversion circuits is subjected to spectroscopic analysis in which most of the level conversion characteristics comply with the law of blackbody radiation. A representative illumination light source among the illumination light sources selected to have level conversion characteristics for white adjustment under an illumination light source with characteristics, and having spectral characteristics in which part of the level conversion characteristics does not comply with the law of blackbody radiation. The configuration has a nonlinear level conversion characteristic selected as the level conversion characteristic for white adjustment shown below.

The two primary color signals obtained by 1q from the output signal of the active image sensor are supplied to the first and second [IJ variable gain amplifiers, respectively, where they are controlled by gain control signals from the first and second level conversion circuits. Individually gain controlled.

The first and second level conversion circuits level-convert the output detection signal of the color temperature detection means that outputs a detection signal according to the color temperature around the subject for self-adjustment, and convert the output detection signal into the first and second level conversion circuits. The gain control signal is supplied to the variable gain amplifier as a gain control signal. Here, the level conversion characteristics of the first and second level conversion circuits are non-linear level conversion characteristics as described above, and under typical illumination light sources among illumination light sources with spectral characteristics that do not follow the law of black body radiation. A gain control signal for white adjustment can be generated.

EXAMPLES Below, examples of the present invention will be described with reference to the drawings.
FIG. 1 shows a block system diagram of an embodiment of an automatic white adjustment device for a television camera according to the present invention. Light from an object is made to enter a solid-state image sensor 2 through an optical system 1. Note that the solid-state image sensing device 2 may be an image pickup tube, and in this specification, this will be collectively referred to as a silver image device. The carrier image signal obtained by photoelectric conversion by the solid-state carrier image element 2 is
Preamplifier, color demodulation circuit, pedestal adjustment circuit.

It is supplied to a process circuit 3 consisting of a gamma correction circuit, etc.
Here, it is amplified and subjected to predetermined signal processing, and output as two primary color signals, for example, a red signal (R signal) and a blue signal (B signal), and a luminance signal (Y). The red signal is fed to a first variable gain amplifier 4 and the θ color signal is fed to a second variable column (7 amplifier 5).

On the other hand, the light from the object is diffused by the first and second diffusion plates 6a and 6b and is incident on the color temperature sensors 7a and 7b, respectively. Here, this color television camera has a shape as shown, for example, by 1/1 in FIG. Light from the subject is also allowed to enter a sensor window 17 located above the lens 15 on the front side. The light transmitted through the sensor window 17 is made to enter the two diffusion plates 6a and 6b. The light that is diffused by the diffusers 6a and 6b and enters the color temperature sensors 7a and 7b is the integrated light of the subject and its surroundings, and is based on the idea that integrating the light in the world produces white light. .

The color temperature sensors 7a and 7b have very different spectral characteristics; for example, color temperature pin leaf a has spectral characteristics that are highly sensitive to red light, and color temperature sensor 7b has high sensitivity to blue light. It has been selected to have unique spectral characteristics. The electric signals obtained by photoelectrically converting the incident diffused light by the color temperature sensors 7a and 7b are supplied to the color temperature detection circuit 8, where they are converted into a color temperature detection signal indicating the level ratio of both signals. The output detection voltage of this color temperature detection circuit (
The relationship between the color temperature detection signal) and the Mired number is based on the fourth
As shown by the solid line in the figure, the color temperature detection signal level corresponds to the color temperature around the subject.

The color temperature detection signal described above is supplied to first and second nonlinear amplifiers 9 and 10, respectively, as an example of a level conversion circuit that forms a main part of the present invention. A signal obtained by nonlinear level conversion by the nonlinear amplifier 9 is supplied to the variable gain amplifier 4 as a gain control voltage. Further, the signal which has been subjected to non-linear level conversion by the non-linear amplifier 10 and has been converted to 1q is supplied to the variable gain amplifier 5 as a gain-side i11 voltage. Here, the level conversion characteristic of the non-linear amplifier 9 is selected such that its output control voltage has a relationship with the Mired number as shown by the solid line ▪ in FIG. 2(A). This level conversion characteristic (■) is approximately complementary to the level ratio (R/Y) of the red signal and luminance signal vs. Mired number characteristic shown by the solid line in FIG. 5(A).
Some of the characteristics required for white adjustment when imaging a subject of a typical illumination light source (in this case, a fluorescent lamp) among illumination light sources with spectral characteristics that do not follow the law of blackbody radiation (Figure 2 (A))
(indicated by an asterisk).

Similarly, the output control voltage vs. Mired number characteristic (level conversion characteristic) of the nonlinear amplifier 10 is approximately complementary to the characteristic shown by the solid line in FIG. 5(B), as shown by the solid line ■ in FIG. 2(B). However, part of it is selected as the nonlinear level conversion characteristic f1 so that it has the characteristics necessary for white adjustment when photographing a subject under fluorescent lamp illumination, as indicated by the star in Fig. 2 (B). has been done.

As a result, even when the subject is a silver image under fluorescent lamp illumination, the output gain of the nonlinear amplifiers 9 and 10 is controlled by the gain signal, and the red signal and the blue signal are extracted from the variable gain amplifier 4.5. The level of the signal is made to substantially match the luminance signal from the process circuit 3,
White color can be adjusted.

red and blue signals from variable gain amplifiers 4 and 5;
The luminance signals from the process circuits 3 are each supplied to a video signal processing circuit 11, where they are converted into color video signals of a required standard color television system (for example, NTSC system), and then outputted to an output terminal 12. Ru.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, the number of color temperature pin lengths having different spectral characteristics may be three. Further, when two types of color difference signals are outputted together with a luminance signal from the process circuit 3, the present invention can be similarly applied to a circuit that adds or subtracts some luminance signals to each color difference signal to achieve white balance.

Effects of the Invention As described above, according to the present invention, white adjustment can be performed accurately even when imaging under an illumination light source that is frequently used, such as a fluorescent lamp, but has spectral characteristics that do not follow the law of black body radiation. In addition, white adjustment can be performed in roughly the same way as before even when imaging under an illumination light source with spectral characteristics according to the law of blackbody radiation, and the accuracy of automatic white adjustment can be improved overall. It has certain characteristics.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the device of the present invention;
2 is a diagram showing an example of the level conversion characteristics of the nonlinear amplifier in the 10-channel system shown in FIG. 1, FIG. 3 is a perspective view of an example of a television camera to which the present invention can be applied, and FIG.
The figure shows an example of color temperature detection voltage vs. Mired number characteristics.
Figure 5 is a diagram showing the relationship between the level ratio of the primary color signal and luminance signal from the silver image element and the Mired number, and Figure 6 is a diagram showing the relationship between the variable gain control voltage and the Mired number in a conventional neck wear. be. 2...Solid-state camera@device, 3...Process circuit, 4,5
... Variable gain amplifier, 7a, 7b... Color temperature sensor, 8... Color temperature detection circuit, 9, 10... Nonlinear amplifier, 17... Sensor window. Patent applicant: Victor Japan Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 1 Figure 4 Millet J&LI5 Figure 6

Claims (1)

[Claims] a color temperature detection means that outputs a detection signal according to the color temperature around the subject; first and second variable gain amplifiers that individually amplify two types of primary color signals obtained from the output signal of the image sensor; The first and second level conversion circuits convert the level of the output detection signal of the color temperature detection means and separately supply the first and second variable gain amplifiers as a gain control signal to individually control the gain. , an automatic white adjustment device that obtains two types of white-adjusted primary color signals and a brightness signal from both output signals of the first and second variable gain amplifiers and a brightness signal from the image sensor, Each of the first and second level conversion circuits is selected to have a level conversion characteristic for white adjustment under an illumination light source whose level conversion characteristic mostly has spectral characteristics in accordance with the law of black body radiation, and It is characterized by a configuration having a nonlinear level conversion characteristic selected as a level conversion characteristic for white adjustment under a typical illumination light source among illumination light sources having spectral characteristics that do not comply with the law of black body radiation. Automatic white adjustment device for television cameras.