JPS61133793A - White balance device for automatically tracking color temperature - Google Patents

Abstract

PURPOSE:To adjust accurately white balance and to reduce considerably the cost, by detecting that the illuminating light source is discharge tube such as fluorescent lamp by an output electric signal issued by photoelectric conversionelement. CONSTITUTION:Illumination light is collectedtoelectric conversion element 2 which is sensitive to red and a photoelectric conversion element 3 which is sensitive to blue, and converted into an electric signal ER and an electric signal EB, then supplied to a subtractor 4. And, they are converted into an electric signal ER/EB and an electris signal EB/ER. On the other hand, the electric signal ER is also supplied to a light smission cycle detecting circuit 11. In case the illumination light is proved to be a discharge tube by the value of output ED of the circuit 11, the electric signals ER/EB, EB/ER are converted into (ER/EB)',(EB /ER)' by the factor of a matrix circuit 12. By selecting the appropriate correction factor, the white balance is adjusted so that the relation among red signal eR, blue signal eB and brightness signal eY as the inputs of encoder 10 should be eR'=eY,eB'=eY.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic color temperature tracking white balance device that can be used in a color video camera device.

2. Description of the Related Art In recent years, automatic color temperature tracking white balance devices that automatically adjust white balance by following changes in illumination light sources have become popular as white balance devices for color video cameras.

An example of a conventional automatic color temperature tracking white balance device will be described below.

FIG. 3 shows main blocks of an example of the use of a conventional automatic color temperature tracking white balance device in a color video camera device. In FIG. 3, illumination light collected by a condenser 1 is incident on a photoelectric conversion element 2 sensitive to red light and a photoelectric conversion element 3 sensitive to blue light. After each A electric signal ER1 is converted into an electric signal EB by the photoelectric conversion element 3, it is inputted to the divider 4, and the divider 4 outputs a complete signal ER/KB, an electric signal EB/I! :R
is converted to

On the other hand, in a color video camera device, an object is imaged on an image pickup tube 5 through a lens, and after being amplified by a preamplifier 6, a color separation circuit 7 is used to generate a blue primary color signal eB, a red primary color signal eR1, and a luminance signal. It is separated into eY. e, , eR are variable gain amplifiers 8. After being input to the variable gain amplifier 9 and having its gain adjusted by the values of the electric signal EB/E□ and the electric signal Ea/E mentioned above, it is input to the encoder 10 and combined with the above-mentioned luminance signal eY. Generate the required video signal.

The operation of the conventional automatic color temperature tracking device configured as described above will be described below.

First, when illumination light with a low color temperature, that is, a strong red light component and a weak blue light component, enters the condenser 1, the value of the output ER/EB of the divider 4 is small, and the value of EB/ER is The variable gain amplifier 8 makes the gain of the red and white color signals small, and the variable gain amplifier 9 adjusts the gain so that the gain of one primary color signal e≦ is reduced. Conversely, when illumination light with a high color temperature, that is, the red light component is weak and the blue light component is strong, the value of the output ER/EB of the divider 4 is small and the value of EB/ER is large. The gain of the red primary color signal θ is increased by the variable gain amplifier 8, and the gain of the evening primary color signal is decreased by the variable gain amplifier 9. Here, photoelectric conversion element 2. Spectral characteristics of photoelectric conversion element 3 and variable gain amplifier 8. By giving appropriate characteristics to the variable gain characteristic of the variable gain amplifier 9, when achromatic colors are photographed, the evening primary color signal e-2 red primary color is input to the encoder 1Q regardless of changes in the color temperature of the illumination light. The relationship between the signal θ; and the luminance signal eY is s'B = eY'
The white balance is adjusted so that ek=θa is satisfied.

Problems to be Solved by the Invention However, when the illumination light is separated into 20 parts using the above configuration, in order to improve the accuracy of output with respect to changes in color temperature, it is necessary to use the photoelectric conversion element 2 for two-color separation and photoelectric conversion. Element 3
Because it is necessary to separate the peak wavelengths of the two spectral characteristics,
Normally, a device with red and blue spectral characteristics is used as in the conventional example above, but if the illumination light source is a fluorescent light with strong energy at the edges, the photoelectric conversion element will be sensitive to the green part. Since it does not have a green light, it cannot detect green light and cannot accurately adjust the white balance.

Therefore, when it is necessary to adjust the white balance more accurately, conventionally, a third photoelectric conversion element with spectral characteristics in the green area is separately prepared, and the ratio between green and red or green and blue is adjusted to adjust the white balance. However, the photoelectric conversion element,
In addition, the number of dividers increases, resulting in a large cost amplifier.

The present invention solves the above problems by detecting that the illumination light source is a discharge tube such as a fluorescent lamp from the output electrical signal of the photoelectric conversion element, and using two conventional red and blue photoelectric conversion elements. Automatic color temperature that performs more accurate white balance adjustment than a two-color separation type, and significantly reduces costs compared to a three-color separation type that uses three photoelectric conversion elements for red, evening, and green. It is a tracking white balance device.

Means for Solving the Problems In order to solve the above problems, the color temperature automatic tracking white balance device of the present invention includes two or more photoelectric conversion elements, a divider that calculates the ratio of the outputs of the photoelectric conversion elements, The device includes a light emission period detection circuit that detects the light emission period of the light source from the output of the photoelectric conversion element, and a matrix circuit that corrects the output of the divider.

Effect: With the above configuration, it is possible to detect whether the illumination light source is a discharge tube by detecting the light emission period of the illumination light source from the output of the photoelectric conversion element. The spectral characteristics of commonly used discharge tubes are limited to only a few types, and the spectral characteristics of discharge tubes of the same type match well. Therefore, when a discharge tube is detected, a correction is made to the output of the divider to match the red primary color signal. By setting the gain of the evening primary color signal to an appropriate value, accurate white balance adjustment can be performed even under the illumination light of a discharge tube such as a fluorescent lamp.

Embodiment Hereinafter, an automatic color temperature tracking white balance device according to an embodiment of the present invention will be described with reference to one drawing. FIG. 1 shows a block diagram of essential parts of an embodiment of the present invention.

In FIG. 1, 1 to 1Q correspond to 1 to 1o of the conventional example, respectively. Reference numeral 11 indicates a light emission cycle detection circuit that detects the light emission cycle of the light source from the output of the photoelectric conversion element 2, and 12 indicates a matrix circuit that corrects the output of the divider 4 using a certain matrix.

The operation of the automatic color temperature tracking white balance device configured as described above will be described below with reference to FIGS. 1 and 2.

The process from photographing a subject with a color video camera to outputting it as a video signal is the same as in the prior art example described above, so a description thereof will be omitted here. First, the illumination light is transmitted by the condenser 1.
The electric signals E8 . Electrical signal E
After BK conversion, it is input to the divider 4 and the electric signal KR
/EB is converted into an electrical signal EB/ER.

On the other hand, the electric signals E and L are also input to the light emission period detection circuit 11. In this circuit, the electric signal ER is used to check the light emitting period of the discharge tube, which is the light emitting period of 50) h to 60 m, and the output ED of the light emitting period detection circuit 11 is expressed as a binary value depending on whether there is a light emitting period or not. This is what is output.

FIG. 2 shows an example of the configuration of the light emission period detection circuit 11.

This light emission period detection circuit 11 can be easily realized by a band pass filter (BPF) 21, an integrator 22, and a level comparison circuit 23, as shown in FIG.

Now, the output electrical signals E, /E and the electrical signal EB/E of the divider 4, as well as the output ED of the light emitting period detection circuit 11, are input to the I-I) multiplex circuit 12.

Here, when the value of E indicates that the illumination light source is not a discharge tube, the electric signal ER/EB.

KB/E8 as it is as an electric signal Ea/E, , E,
/ER, and at this time, the photoelectric conversion element 2. Red and evening optical filter characteristics of photoelectric conversion element 3 and variable gain amplifier 8. By giving appropriate characteristics to the variable gain characteristic of the variable gain amplifier 9, the relationship between the red primary color signal e2, the evening primary color signal e2, and the luminance signal eY is changed to e at the input of the encoder 1o.
The white balance can be adjusted so that 2 = eY, e nee e, etc. Next, when the value of ED indicates that the illumination light source is a discharge tube, the electric signals E, /E,.

KB/E passes through the matrix circuit 12, and a complete signal (E□/EB)' is generated by the function of the matrix circuit 12.

(EB/ER)', but by selecting an appropriate function for this correction, the encoder 10
By inputting , the white balance can be adjusted so as to satisfy the relationship e, , = eY, and e2 = eY.

Effects of the Invention As described above, according to the present invention, an appropriate white balance can be obtained for a color video camera even under illumination light having special spectral characteristics such as from a discharge tube.

[Brief explanation of drawings]

Fig. 1 is a main circuit block diagram of an embodiment of the present invention;
The figure is a block diagram showing an example of the structure of a light emitting period detection circuit used in the present invention, and FIG. 3 is a block diagram showing the main circuit of a conventional example. 2.3...Photoelectric conversion element, 4...Divider, 11...Emission cycle detection circuit, 12...
・Matrix circuit.

Claims (1)

[Claims] A color video camera device comprising two or more photoelectric conversion elements and a divider that takes a ratio of outputs of the photoelectric conversion elements, and adjusting white balance by the output of the divider, the output of the photoelectric conversion element A light emitting cycle detection circuit that detects the light emitting cycle of the light source from a signal, and a matrix circuit that uses the output of the light emitting cycle detection circuit to correct the output of the divider in order to set the white balance to an appropriate value. Automatic color temperature tracking white balance device.