JPS62296692A - White balance adjusting device for television camera - Google Patents

Abstract

PURPOSE:To easily and freely take a picture even under any condition by operating a switch means and making an automatic white balance adjustment and a white balance adjustment based upon a stored signal selectively. CONSTITUTION:The output of a white balance detecting circuit W is sent to variable gain amplifiers 4 and 5 through buffer amplifiers 15r and 15b and their gains are controlled to adjust the white balance of a video signal. When a tandem switch SW is turned on, the outputs V3 and V4 of operational amplifiers 11 and 12 are sent to the variable gain amplifier for infrared signal gain control and variable gain amplifier 5 for blue signal gain control through the amplifiers 15r and 15b to automatically adjust the white balance following up variation in the color temperature of an illumination light source as a subject. Then when the SW is turned off, the outputs V3 and V3 before the off operation are held in memory capacitors 13 and 14 to adjust the white balance.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention A. Field of Industrial Application The present invention relates to an automatic white balance adjustment device for a video camera.

When shooting with a conventional technology TV camera, the color temperature of the light that is incident on the external light receiver of the automatic white balance adjustment device and the light that actually illuminates the subject may be different. There is. For example, if the subject is backlit and the subject is illuminated by an artificial light source near a TV camera, the light receiving section of the white balance adjustment device will mainly receive light from the background of the subject or from the sky. , almost no light from artificial light sources is incident. In such cases, correct white balance cannot be obtained. In conventional automatic white balance adjustment devices installed in television cameras, the light receiving section receives light from a wide range in front of the camera, so an appropriate white balance condition is normally maintained. When using a series of special lighting, there is a problem in that the correct white balance cannot be obtained.

The above-mentioned problem cannot be solved by automatic white balance adjustment, but the television camera described in Japanese Patent Publication No. 60-4637 has wQ'M. The television camera described in the publication uses a luminance signal Y and two color signals R9B obtained through each photographic lens and an image pickup electric system.A white surface is placed at the position of the subject, and two color difference signals R are used.
- Two color signals R2 so that Y and B-Y are both zero.
The B gain is set, that is, the gain of the variable gain amplifier that amplifies both the R and B signals is adjusted, the gain is fixed, and the actual photographing begins. According to this TV camera, as long as the subject lighting conditions are fixed, the correct white balance can be obtained no matter what lighting method is used. Therefore, photographing operations are troublesome and it is not possible to deal with changes in lighting conditions.

C.9 Problems to be Solved by the Invention The present invention attempts to provide a white balance adjustment device that is capable of automatically adjusting white balance and can obtain the correct white balance even under the above-mentioned special lighting conditions. It is.

2. Means for solving the problem; a balance detection means for receiving an external light and outputting an automatic white balance signal; a storage means for storing the automatic white balance signal; A white balance adjustment device is constructed by a switch means for selecting an automatic white balance signal or a storage signal, and an adjustment means for adjusting the white balance according to the selected signal.

When the switch means selects the automatic white balance signal, automatic white balance adjustment is performed using the automatic white balance signal output from the white balance detection means. Further, when the first signal is selected, white balance adjustment is performed using an automatic white balance signal stored in the storage means. Therefore, for example, if the storage means is interposed between the white balance detection circuit and the adjustment means, and the switch means is an open/close switch that inputs the output of the white balance detection circuit to the storage means,
During normal shooting, if you close the switch, automatic white balance adjustment will be performed. On the other hand, when the lighting is such that the white balance detection means cannot receive light during shooting, for example, it may be due to auxiliary lighting during backlighting as described above, or fluorescent lighting from the ceiling in stage shooting, etc., and the white balance detection means cannot detect the light. On the other hand, if the person on the stage is illuminated by a spotlight using a tungsten light bulb in addition to a fluorescent light on the ceiling, point the TV camera toward the light source and watch it. If you output a white balance signal for the light source and then open the switch to take a picture, it will be controlled by the white balance signal for the illumination light at that time, so you can get the correct white! , < Lance will be obtained.

To, Example FIG. 1 shows a circuit of a video camera according to an embodiment of the present invention.

The part W surrounded by the dotted line in the figure is the part that includes the white balance detection circuit and the storage means, and the output buffer amplifier 15.
Two white balance signals are output from r and 15b. A double switch S is connected between these buffer amplifiers 15r, 15b and the preceding operational amplifier 11.12.
A storage capacitor 3.times.14 is connected between the input terminals of the buffer amplifiers 15r and 15b and the ground. In the figure, the white balance detection circuit is on the left side from the switch Sw. I is an imaging lens system of a television camera, 2 is an image sensor, 3 is a color separation circuit that separates a luminance signal and two color signals from the output of the image sensor 2, 4 is a variable gain amplifier that adjusts the gain of the red signal, 5 6 is a variable gain amplifier that adjusts the gain of the blue signal, and 6 is an encoder that forms an NTSC signal from a luminance signal and two color signals. With this configuration, the output of the balance detection circuit is sent to the two variable gain amplifiers 4 and 5 via the buffer amplifiers J5r, 5b, and gain control of the amplifiers 4 and 5 is performed to control the video signal. White balance is achieved. The part W in the child chain l: configuration will be described in detail below.

In Figure 1, Rga and Rr are two photoconductive elements with the same characteristics formed on the same substrate -U, and Rh and Rgb are two photoconductive elements with solid characteristics formed on the same substrate -L. It is a conductive element. FIG. 2 shows the arrangement of these four photoconductive elements. Rga and Rr are formed side by side on one substrate Ba, Rgb and Rh are formed side by side on another substrate Bbl, and the two substrates Ba and Bb are arranged side by side to receive external light. There is. A red transmission filter Fr is arranged in front of R and r of the photoconductive element, a blue transmission filter Fb is arranged in front of Rb, and a green transmission filter Fg is arranged in common with Rga and Rgb. . External light is made to enter each photoconductive element equally through a light diffusion plate and a lenticular C2 infrared cut filter IF.

Such a light expanding plate, lenticular C, filter Fr,
Fg, Fb, each photoconductive element Rr, Rga, R
The light receiving section for color measurement consisting of gb, R, and b is shown in Figure 3 (1)
As shown in , it is placed in front of the television camera. In this figure, 17 is a photographing lens.

When performing automatic white balance adjustment, the double switch Sw is in the ON state, and the outputs V3. V4 is sent to the variable gain amplifier 4 for red signal gain adjustment and the variable gain amplifier 5 for blue signal gain adjustment via the buffer amplifier 15r r 1.5b, and the color temperature of the light source illuminating the subject is changed. The white balance will also be adjusted automatically accordingly. When the switch Sw is turned OFF, OFF M, the output V3 of the previous operational amplifier 11, 12. V4 is memory capacitor 13
14, and a white balance adjustment operation is performed using this held signal.

Finally, the configuration and operation of the white balance detection circuit itself will be explained. As shown in FIG.
One end of the two photoconductive elements Rr and Rga formed on a is connected to the inverting terminal side of the operational amplifier 9 as an input resistor, the other end is connected to the voltage source E1, and the other end is connected to the inverting terminal side of the operational amplifier 9 as an input resistor. The photoconductive element Rr is connected as a feedback resistor between the output terminal and the inverting terminal of the operational amplifier 9. Therefore, the output voltage V1 of the operational amplifier 9 is Vl-=E2-(E1-E2)Rr/Rga・=(1
) Similarly, the output voltage v2 of the operational amplifier 10 is V2=E
3-(E3-E4)Rb/Rgb=・(2) Next, the output voltage v3 of the operational amplifier 11 to which vl is input is V3=Vref−(Vl−Vref)R2/R1・・
・(3) The output voltage v4 of the operational amplifier 12 to which v2 is input is V4=Vref −(Vl−Vref)R,4/R,3
...(4) Red and green when CdS is used as the photoconductive element.

The illuminance of each blue color light on the element is Lr, Lg, 1. b, then −r −γ Rr/Rga=ALr/ALg=(Lg/I.

r) Y...(5) / -γ I-r R, b / Rg )) = A I-)) /
A T-g - (I, g/Lb) ... (6) The illuminance of each color light of red, green, and blue at the standard color temperature is Ro,
Go, Bo, and the above V3. where the external light has a good standard color temperature. V
Assuming that El and E3 are adjusted so that Vref is equal to Vref, V3. Without organizing the formula of V4, 1V3=Vre f+
K (Lg/Lr) -K (Go/R,o)...
(7) V4=Vre f+'(Lg/Lb f-'
(Go/and Bo)...(8) If you further adjust the resistance ratios R2/R1, R, 4/R3! Since K changes, Vref=K(Go/RO)'='(GO/B(-1
)', V3=K(Lg/Lr)'V4=K(Lg/Lb)"-, the ratio of red light and blue light to green light is found, and this is the white balance signal. Become.

The switch Sw in Fig. 1 is operated by the automatic white balance adjustment lock push button provided on the telepino 1 camera. When it is not pressed, automatic white balance adjustment is performed, and when it is pressed, the switch Sw opens and the previous A white balance signal is held in capacitors 13 and 14, and the white balance of the imaging system is adjusted using this held signal.

Note that the switch may be a semiconductor switch that is electrically turned on and off in conjunction with the operation of a push button. Further, the above switch may be a so-called changeover switch. That is,
As shown in FIG. 4, a white balance detection means 21 and a storage means 22 are provided in parallel with the switch 23, and the storage means is always updated by inputting a white balance signal, and the outputs of these two means are The switch means 23
may be selected.

G. Effects In the conventional device mentioned at the beginning, the white balance is fixedly adjusted by imaging a white subject in advance, or by attaching a light diffusion plate to the photographing lens and aiming the image at the illumination light source.
Although it is possible to obtain the correct white balance even under special lighting conditions, it is not necessary to set the white balance, and as mentioned above, the operation is troublesome.

On the other hand, with the present invention, even under special lighting conditions, there is no need to attach a diffuser to the lens or prepare a white subject, and the automatic white balance adjustment or memorization can be performed simply by operating the switch means. Since white balance adjustment is performed selectively using signals, you can freely and easily take pictures under any conditions.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a sectional view of a light receiving section for color temperature detection in the same embodiment, and Fig. 3 is a front view of the television camera showing the position of the television camera in the light receiving section. 4 are main part circuit diagrams of other embodiments. Rr, Rb, Rga, Rgb-photoconductive element, P...light receiving section, Fr...red transmission filter, Fg...green transmission filter, Fb...blue transmission filter. Figure 2■--ta]-ga Figure 3〆D [Ki Sannukiken 1] Uyowa section

Claims (2)

[Claims] (1) White balance detection means having a colorimetric light receiving section and outputting an automatic white balance signal based on a signal from the light receiving section, means for storing the white balance signal, and the automatic white balance detection means A television camera comprising: a switch means for selecting an automatic white balance signal from the storage means or a storage signal from the storage means; and an adjustment means for adjusting the white balance according to the signal selected by the switch means. white balance adjustment device. (2) The switch means is connected between the white balance detection means and the storage means, and the storage means outputs a signal from the white balance detection means to the adjustment means when the switch means is closed, and the storage means is opened. 2. The white balance adjustment device for a television camera according to claim 1, wherein the white balance adjustment device for a television camera outputs the stored signal from the white balance detection means in response to the opening operation when the camera is opened.