JPS6339296A - Automatic white balance adjusting device - Google Patents

Abstract

PURPOSE:To enable an automatic white balance adjustment which doesn't dislocate so much even under the high intensity of illumination by converging a first signal corresponding to the ratio of the quantity of light between a first color light and a second color light and a second signal corresponding to the ratio of the quantity of light between a third color light and the second color light into a specified value as the quantity of light of any color light becomes large. CONSTITUTION:Ceiling value set circuits 53 and 54 respectively set ceiling values which makes the ceiling value of the clips of clip circuits 51 and 52 output to a signal SG. And the bottom value of the clips of bottom value set circuits 55 and 56 is made to output to the signal SG. The input-output characteristic of the ceiling value set circuits 53 and 54 and the bottom value set circuits 55 and 56 is shown by a figure. Namely, the output values of the ceiling value set circuits 53 and 54 are set as K1 and K2 and the output values of the bottom value set circuits 55 and 56 are set as K3 and K4. When the output values K1-K4 changes against the signal SG in the way shown by the figure, the range of the outputs from the clip circuits 51 and 52 is converged into the specified value as the signal SG becomes large such as parts shown with oblique lines in figure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic white balance adjustment device for a color video camera.

[Prior Art] FIGS. 3 and 4 show a conventional automatic white balance υi,l device disclosed in, for example, Japanese Patent Laid-Open No. 58-15-793.

FIG. 3 is a diagram explaining the concept of a conventional color video camera. Reference numeral 2 in FIG. 3 denotes a light source spectral characteristic detection section. This light source spectral characteristic detection section 2 is directed toward the light source 1a, detects all the spectral characteristics of the light source 1a, and sends a correction signal to the color camera 3.
send to Since the reflected light 1ex of the subject 1b input to the color camera 3 is affected by the light source color temperature, if the video signal obtained by this reflected light 1e2 is corrected with the correction signal described above, an appropriate video signal can be obtained. It will be done.

That is, the subject 1b and the light source spectral characteristic detection unit 2 receive direct light 1el from the light source 1a.

le3 is emitted. The direct light from the light source 1el should be 1e3, and the reflected light leg from the subject 1b is the direct light from the light source 1.
It must be influenced by el.

Therefore, an appropriate video signal can be obtained by the above-described correction.

Hereinafter, the conventional device will be explained in detail with reference to FIG. 4.The light input to the light source spectral characteristic detection section 2 has characteristics such that the sensitivity peaks in visible light red, green, and blue. Photoelectric conversion element R8, Go in the ridge.

The three primary color signal components are converted into electrical signals by Bo, and are amplified by 5 times each by preamplifiers 2a, 2b, and 2c.

The three electrical signals output from the three preamplifiers 2a, 2b, and 2c indicate the spectral characteristics of the light source 1a, and also correspond to the signal vR9VG+VB in the color camera 3.

The outputs of the preamplifier 2a and the amplifier 2C are input to one input terminal of the comparators 2d and 2e, respectively, and further,
The output of the preamplifier 2b is input to the other input terminals of the comparators 2d and 2e. Outputs from the comparators 2d and 2e reach the color camera 3.

The signals amplified by preamplifiers 2a, 2b, and 2c are converted to SRI.
sG, SKI, in the comparator 2d, the signal S
Compare yt and Sc and find out the coefficient Kn? Similarly, comparator 2e
Then, find the coefficient KB t”. Coefficient K n * K n
are relative values of red and blue, respectively, based on the green level of the light source 1a.

Specifically, the color camera 3 is an NTSC three-tube color camera, and optical signals corresponding to red, green, and blue are inputted from the image pickup tubes RT, GT, and BT, respectively, and converted into electrical signals. The signals output from the image pickup tubes RT and GTIBT are respectively sent to preamplifiers A Rs A G m
A 11 is inputted and amplified, and the respective signals V Re
It is output as VG #VB.

Level correction amplifiers 3a and 3b are connected to the preamplifier AR and preamplifier AB, respectively. The output signal from the comparator 2d is input to the level correction amplifier 3aK, and the output signal from the comparator 2e is input to the level correction amplifier 3b.

The level correction amplifiers 3a, 3b calculate the desired V u at the gain point based on the output signals of the comparators 2d, 2e.
*V cm V B signal is green (VG)
t-Reference K Level Correction Gain is controlled by Annia's 3a and 3b, resulting in a proper video signal.
The signal is sent to the Jx circuit 31.

That is, the signal corresponding to blue is output by the level correction amplifier 3a and the red correction amplifier 3b. Mano VC.

Therefore, the signals corresponding to red and blue obtained from the subject 1b become signals corrected based on the proportion (based on green) contained in the light source 1a.

Tsu-! In this conventional example, no matter how much the relative value of the spectral characteristics of the light source 1a changes, the relative amount is always 1:1:1.
It is possible to obtain a signal equivalent to when the subject is illuminated by a light source.

Therefore, an object that appears white with a certain photon of illumination will always appear white even if the light source changes. In other words, the white balance can be automatically adjusted.

Note that even though it is called white, the color temperature that feels most white differs depending on the person and the surrounding colors, so there is no problem in performing hue correction separately from the above-mentioned correction.

The signal is directly sent to the adder 35, and the engineering signal and Q signal are sent to the adder 35 via a low-noise filter 32, 33 and a modulator 34.
5. The adder 35 adds these Y, I, and Q signals and outputs them as a video signal.

[Problem that the invention seeks to solve]

Since the conventional automatic white balance adjustment device is configured as described above, when the light input to the photoelectric conversion element R8+GQe BQ is large, the coefficient K R changes when its output is saturated.
*Kn has a value that does not correspond to the spectral characteristics of the light source at all, resulting in problems such as a large deviation in white balance.

This invention was made to solve this problem, and is an automatic white balance adjustment system that does not deviate significantly even under high illuminance. ! :'The aim is to obtain.

[Means to solve all problems]

The automatic white balance adjustment device according to the present invention corresponds to an example in which the amount of light of either one of the second or third color light is large, thus corresponding to the ratio of the amount of light of the first color light and the second color light. Means is provided for converging the first signal and the second signal corresponding to the ratio of the light amounts of the third color light and the second color light to a specific value.

[For production]

In this invention, the first signal and the second signal are the first .
As the color light 0 element i of either the second or third color light increases, the first and second signals converge to a specific value.

〔Example〕

Embodiments of the automatic white balance adjustment device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment. In FIG. 1, parts that are the same as those in FIG. 4 are given IDl- symbols to avoid redundant explanation, and parts that are different from those in FIG. 4 will be mainly described.

In this Fig. 1, reference numerals 5) to 55 are newly added to the configuration of Fig. 4.
5)゜52 is a clip circuit, 5)a and 52a are clip circuits 5). 52 input terminals, 5)b, 52b are clip circuits 5). Terminal for setting the upper limit value of the clip in 52, 5) c, 52c
is a clip circuit 5). A terminal for setting the lower limit value of clipping in 52, 5)d, and 52d are clipping circuits 5). 5
This is the second output terminal.

The signal Sc from the preamplifier 2b is input to the upper limit setting circuit 53.54, and the output of the upper limit setting circuit 53.54 is connected to the terminal 5)b of the click 7''' circuit 5).52. , 52b, respectively.

In addition, the lower limit value setting circuits 55 and 56 include the preamplifier 2b
The outputs of the lower limit value setting circuits 55 and 56 are supplied to the terminals 5)b and 52b.

Upper limit value setting circuits 53 and 54 are each clip circuits 5)
．． 52 is used to set the upper limit value for outputting the upper limit value of the clip for the signal SG, and the lower limit value for the clip for the lower limit value setting circuits 55 and 56 is output for the signal Sc.

These upper limit value setting circuits 53, 54 and lower limit value setting circuit 5
The input/output characteristics of 5.56 will be described later.

Next, the operation of the present invention will be explained, but since the same parts as in FIG. 4 perform the same operations, the explanation will be omitted. FIG. 2(a) and FIG. 2(6) are diagrams showing the input/output characteristics of the upper limit value setting circuits 53 and 54 and the lower limit value setting circuits 55 and 56.

Output value t-Ks * Kx of upper limit value setting circuit 53.54
shall be. Output value tKs of lower limit value setting circuit 55.56
.

Let's call it K4. These output values Ks e Kgs Ks
e K4 responds to signal Sc in Fig. 2(a), Fig. 2(
When the changes shown in b) occur, the clip circuit 5). 52
The range of the output converges to a specific value as the signal Sc becomes larger, as shown by diagonal lines in FIGS. 2(a) and 2(b).

Considering that this type of automatic white balance adjustment device is actually used in home color video cameras, the above-mentioned converging specific values will not allow correct white balance adjustment when the light source is sunlight on a clear day. A good value is

Does the specific value mentioned above correspond to clear sunlight? The reason for choosing a value that allows correct white balance adjustment when used as a light source is that, especially when targeting a home color video camera, the amount of light input to the conversion element increases significantly by 9% due to the UK sunlight. This is because it is thought that most of the time, the images will be shot at the same location.

In the above embodiment, the 3afO optical turtle conversion element was explained as having sensitivity peaks in red, green, and blue, but the 38i color may be any other color as long as it is three independent colors. good. For example, the first to third colored lights may be red light, golden light, or blue light, or may be yellow light, green light, or cyan light, and further may be yellow light, all-color light, or cyan light. It may be.

Moreover, the same effect can be achieved even if other methods are used to converge the first signal and the second signal.

Furthermore, in the description of the conventional example and one embodiment of the present invention,
In the above, a case has been described in which the white balance is adjusted by detecting the spectral characteristics of the light source, but the white balance may also be adjusted using the original spectral characteristics obtained by integrating the reflected light from the subject using a diffuser plate or the like.

In addition, the first signal and the second signal control the difference between the red signal and the luminance signal, the magnitude of the luminance signal that is added to or subtracted from the signal, and the magnitude of the luminance signal that is added to or subtracted from the difference signal between the blue signal and the luminance signal. You can also adjust the white balance.

〔Effect of the invention〕

This invention? 'i As explained above, as the light amount of any one of the first to third colored lights increases, the amount of the first to third colored lights increases. Since the second signal is set to a specific value, even if the white balance 'fAh deviates at high illuminance, the deviation is small and can converge to a specific value.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the automatic white balance adjustment device of the present invention, FIG. 2(a), FIG. 2(b)
Fi "in the same automatic white balance adjustment device as above":
T#, value setting 1 Ayu and input/output characteristics diagram of the lower limit value setting circuit. Figure 3 is a diagram to explain the concept of a conventional color video camera. Figure 4 is a diagram of a conventional automatic white balance adjustment device. It is a block diagram. 3...Color camera, RT m G? -BT・
...Image tube, 3a, 3b...Level correction amplifier, 31
...Matrix circuit, 32.33...Ronozoos filter, 34...Modulator, 35...Adder, 5...
・Light source spectral characteristics detection unit, RO* G Oa B O””
Light converting element, 2c, 2d-comparator, 5). 52...
Clip circuit, 53.54... Upper limit value setting circuit, 55
．． 56... Lower limit value setting circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts. Daitan! Figure 1 Figure 2 (a) (b) Figure 3 Figure 4

Claims (9)

[Claims] (1) A first signal corresponding to the ratio of the light amount of the first color light to the light amount of the second color light; In a white balance adjustment device for a color video camera that adjusts white balance using a second signal corresponding to the ratio of the first color light and the second color light, the light amount of any one of the first, second, or third color light; 1. An automatic white balance adjustment device characterized by comprising means for converging the first and second signals to a specific value as the value increases. (2) the first color light, the second color light, and the third color light are red light;
The automatic white balance adjustment device according to claim 1, characterized in that the light is green light or blue light. (3) the first color light, the second color light, and the third color light are red light;
2. The automatic white balance adjustment device according to claim 1, wherein the automatic white balance adjustment device uses full color light and blue light. (4) The first colored light, the second colored light, and the third colored light are yellow light;
The automatic white balance adjustment device according to claim 1, characterized in that the light is green light or cyan light. (5) the first color light, the second color light, and the third color light are yellow light;
2. The automatic white balance adjustment device according to claim 1, wherein the automatic white balance adjustment device uses full color light and cyan color light. (6) gain of the red signal by the first signal and the second signal;
6. The automatic white balance adjustment device according to claim 1, wherein the white balance is adjusted by controlling the gain of the blue signal. (7) By controlling the magnitude of the luminance signal to be added to or subtracted from the difference signal between the red signal and the luminance signal and the magnitude of the luminance signal to be added to or subtracted from the difference signal between the blue signal and the luminance signal using the first signal and the second signal. An automatic white balance adjustment device according to any one of claims 1 to 5, characterized in that the automatic white balance adjustment device adjusts white balance. (8) The means for converging the first signal and the second signal to specific values includes a clip circuit that limits the values of the first signal and the second signal, and an upper limit value for clipping the signal in this clip circuit. , the lower limit value is converged to the specific value as the amount of light of any one of the first, second, or third color light increases. automatic white balance adjustment device. (9) As the light intensity of any one of the first, second, or third color light increases, the first signal and the second signal will correctly balance white when sunny sunlight is used as the light source. 9. The automatic white balance adjustment device according to claim 1, wherein the automatic white balance adjustment device converges to the adjusted value.