JPS6246117B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color television camera (hereinafter referred to as TV).
This invention relates to a white balance adjustment device for a camera (referred to as a camera).

Conventionally, white balance has been adjusted by preparing a white subject and adjusting the level of a color signal obtained when the subject is imaged before imaging the subject. Also, when the color temperature of the illumination changed during image capture, the photographer observed the change in color temperature based on his own experience and adjusted the white balance in the same way as before the image capture.

First, an example of a white balance adjustment device in a two-frequency separation single-tube color camera will be described with reference to FIG. Figure 1 shows that the optical information of the subject is spatially modulated using transparent-yellow and transparent-cyan striped filters with different repetition frequencies, and the spatially modulated optical information is converted into an electrical signal using an image pickup tube. (hereinafter referred to as
(BPF) separates red and blue modulation signals, detects these modulation signals to obtain red (R) and blue (B) color signals, and obtains an NTSC signal with an encoder. 2-frequency separation single-tube color It's a camera. In FIG. 1, 1 is an image pickup tube with a built-in strump filter as described above, 2 is a preamplifier that amplifies the output signal of the image pickup tube, 3 is a color separation circuit with two BPFs,
4 is an LP that separates the low frequency signal, that is, the luminance signal (Y)
F, 5, 6 are gain control circuits that vary the gain of the red or blue modulation signal; 7, 8 are manual variable voltage sources that provide voltages for controlling the gains of the gain control circuits 5, 6; 9; 10 is a detector for detecting a red or blue modulation signal; 11 and 12 are color difference signals (R-
Y), a subtracter to obtain (B-Y), 13 is
This is an encoder for obtaining NTSC signals. Note that 14 is a lens placed in front of the image pickup tube 1.

In Fig. 1, a white subject is imaged and the variable voltage sources 7 and 8 are varied to produce color difference signals (R-Y) and (B-Y).
Adjust the white balance so that it is zero.
In this device, if the color temperature changes due to changes in illumination or outdoor natural light conditions during image capture, the photographer must use his or her intuition to recognize the change in color temperature and adjust the white balance. However, it is impossible for a person who is not skilled in the handling to judge whether the color temperature has changed during image capturing.

Further, the one shown in FIG. 2 can be considered as one having a function of notifying whether readjustment of the white balance is necessary. In FIG. 2, numerals 1 to 14 are the same as each circuit in FIG. 1, and have the same function.
Reference numeral 15 indicates a light condenser that collects external light from the surroundings including the subject at a wide angle, 16 indicates the output of a color temperature detector that detects the color temperature of the light from the light concentrator 15, and 17 indicates the output of the color temperature detector when adjusted. a color temperature change detector that detects that the color temperature detector and the color temperature detector during imaging have changed by a predetermined amount or more; 18 is a gate signal generator that generates a gate signal based on the output of the color temperature change detector; 19;
is an alarm that notifies that the color temperature has changed due to the gate signal. With the configuration shown in FIG. 2, if the color temperature of outside light changes, the annunciator 19 notifies the photographer of the need for adjustment, so the white balance can be adjusted by changing the variable voltage sources 7 and 8. For example, it is possible to always take an image with the white balance correct, without taking an image with the white balance incorrect.

Next, FIG. 3 shows a detailed view of the portions indicated by numerals 15 to 19 in FIG. 2. In FIG. 3, 20 is a detector for the red signal _RT , 24 is a detector for the luminance signal _YT ,
22 is a detector for the blue signal B _T ; 23, 24, and 25 are amplifiers for R _T , Y _T , and _BT, respectively; and 26 and 27 are signals (R _T −Y _T ), (B _T −Y _T ). 28, 29 are comparison circuits, 30, 31 are storage circuits, 32, 33 are gate circuits, 34, 35 are gate signal generators, 36 is an OR circuit, 37 is an alarm,
38 is a manual gate signal generator. However, R _T ,
Spectral characteristics of the detectors 20, 21, 22 of Y _T and B _T and the luminance signal Y, red signal R, and blue signal B in the image pickup tube
The spectral characteristics of are kept almost the same.

In the above configuration, after adjusting the white balance of the TV camera, the manual gate signal generator 38 generates a gate signal, and this gate signal causes the gate circuit 32,
33 to store the outputs of subtracters 26 and 27 in storage circuits 30 and 31, respectively. Next, an image is taken, and when the color temperature of the external light around the subject changes during the image taking, the detectors 20, 21 of R _T , Y _T , B _T ,
Since the ratio of the output of 22 changes, the subtractor 26,2
The output of 7 is different from the output of memory circuits 30 and 31.
This difference is detected by comparison circuits 28 and 29, respectively, gate signals are generated by gate signal generators 34 and 35, and these two gate signals are passed through an OR circuit 36 when a gate signal is generated in at least one of them. It is possible to activate the alarm 37. However, the comparison circuits 28 and 29 are the subtracters 26 and 27.
A signal is generated only when the output of the memory circuits 30 and 31 changes by more than a predetermined amount (this predetermined amount is determined by the white balance tolerance range).

A specific circuit example of the comparison circuits 28 and 29 is shown in the fourth section.
As shown in the figure.

The comparison circuit includes an input terminal 39 from the subtracter 26 or 27, an input terminal 40 from the memory circuit 30 or 31, an output terminal 41, constant current sources 42, 43,
44, 45, transistor (hereinafter abbreviated as Tr) 4
6, 47, 48, 49, resistance 50, 51, 52,
It consists of 53, 54, and 55. The base voltage of Tr 47 is made higher than the voltage at terminal 40 by constant current source 42 . The amount of this increased voltage is determined by the constant current source 4
2 and the value of the resistor 52. In a similar manner, the base voltage of Tr 49 becomes lower than the voltage at terminal 40. Here, if the voltage at the terminal 39 is lower than the base voltage of the Tr47, the Tr47 is turned off, and the collector of the Tr47 becomes the power supply voltage B. The voltage at terminal 39 is
If it is higher than the base voltage of Tr47, the power supply voltage B is increased by the voltage determined by the resistor 50 and constant current source 44.
becomes lower. On the other hand, if the voltage at terminal 39 is higher than the base voltage of Tr49, Tr48 is turned off and Tr48 is turned off.
The collector of Tr48 becomes power supply voltage B, and if the voltage of terminal 39 is lower than the base voltage of Tr49, Tr4
8 becomes lower than power supply voltage B by a voltage determined by resistor 51 and constant current source 45. Therefore, the voltage at terminal 41 is the same as when the power supply at terminal 39 is Tr4.
It becomes equal to the power supply voltage B only when it is within the range of the base voltage of Tr 7 and the base voltage of Tr 49, and when it is outside the range, it drops below the power supply voltage. With the above configuration, it is possible to easily determine whether the color temperature has changed by a predetermined amount or more.

However, in this method, the condenser 15 and R
Detectors 20, 21, and 22 for _T , Y _T , and B _T are required, making the device large-scale. Therefore, the present invention uses video signals obtained from a camera without using a condenser or a detector. The present invention provides a white balance adjustment circuit that determines whether readjustment of balance is necessary. An embodiment of the invention is shown in FIG. Fifth
In the figure, numerals 1 to 14 are the same as in FIG. 2, and they operate in the same way. The gain control circuits 56 and 57 have the same configuration as the gain control circuits 5 and 6, the detectors 58 and 59 have the same configuration as the detectors 9 and 10, and the subtraction circuits 60 and 61 have the same configuration as the subtraction circuits 11 and 1.
2, the smoothing circuits 62 and 63 are circuits that smooth over the vertical scanning period, and the comparison circuits 64 and 65
is a circuit having the same configuration as the comparison circuits 28 and 29,
The OR circuit 66 is the same circuit as the OR circuit 36, and the alarm 67 is the same circuit as the alarm 37.

gain control circuits 56, 57, detectors 58, 59,
The subtraction circuits 60, 61 and the smoothing circuits 62, 63 constitute a negative feedback loop, and work so that the average value of the outputs of the subtraction circuits 60, 61 is always zero. When imaging a white subject, the control signal to the gain control circuit 56 and the control signal 5 match, and the gain control circuit 5
The control signal to 7 and the control signal to 6 should match. If they do not match, the white balance must be adjusted by moving the variable voltage sources 7 and 8. This is because the gain control circuits 5, 6, 5
6, 57, detectors 9, 10, 58, 59, and subtracters 11, 12, 60, 61 have the same circuit, so when imaging a white subject, the gain control circuit 5, 5
This is because the gain of the circuit 6 and the gains of the gain control circuits 6 and 57 must be the same. Therefore, the respective control signals are compared by comparison circuits 64 and 65,
If the white balance differs by more than a predetermined amount, an annunciator 67 informs the photographer of the need to readjust the white balance through an OR circuit 66. Experiments have shown that the average value of the color difference signals when photographing a wide-angle image, not only when photographing a white subject, will almost match the color difference signal obtained from a white subject. 67, it is necessary to readjust the white balance. Note that when using this imaging output, the average value within the screen may not be completely white due to narrow-angle shooting or the color of the subject, and the alarm 67 will also operate in this case, but this is at the operator's discretion. It is better to think about it manually.

As an embodiment of the present invention, a two-frequency separation type TV camera has been described as an example, but TV cameras configured to obtain color difference signals from red, edge, and blue, and other types of color
It is obvious that all TV cameras use circuits of similar construction. Note that as the alarm 67, a well-known light indicator or sound alarm can be used.

As is clear from the above embodiments, the white balance adjustment device of the present invention has a very simple configuration and notifies that the color temperature of the illumination of the subject has changed, allowing the operator to easily adjust the white balance. Since readjustment is possible, image output with good color balance can always be guaranteed.

[Brief explanation of the drawing]

Figure 1 shows a device equipped with a conventional white balance adjustment device.
A configuration diagram of the main parts of a TV camera. Figure 2 is a configuration diagram with a device that notifies white balance deviation, and Figure 3 is a configuration diagram of the main parts of a TV camera.
FIG. 4 is a circuit diagram showing an example of the comparison circuit of FIG. 3, and FIG. 5 is a configuration diagram of an embodiment of the present invention. 5, 6, 56, 57...gain control circuit, 9, 1
0, 58, 59...detector, 11, 12, 60,
61...Subtraction circuit, 62, 63...Smoothing circuit, 6
4,65...comparison circuit.

Claims (1)

[Claims] 1 First and second gain control circuits controlled by external voltages provided for two of the three colors, each of the two colors obtained from the first and second gain control circuits, and the other one The first step is to obtain two color difference signals from the color.
The first signal processing section configured with a second color difference circuit, the third and fourth gain control circuits, and the third and fourth color difference circuits have the same configuration and the same structure as the first signal processing circuit. a second signal processing section configured with characteristics;
Smoothing the outputs of the third and fourth color difference circuits for at least one vertical scanning period, respectively;
A smoothing circuit that generates a voltage to control the gain of the gain control circuit is compared with the control voltages of the first and third gain control circuits and the second and fourth gain control circuits, and when the inputs differ by more than a predetermined amount, a signal is generated. A white balance adjustment device comprising two comparison circuits that generate output, and an alarm that notifies that at least one of the comparison circuits generates an output.