JPS6153912B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color temperature correction device when the color temperature of a light source that illuminates a subject to be imaged by a color television camera changes.

Conventionally, in color television cameras, when the color temperature of the light source changes, a color temperature conversion filter is installed in front of the image pickup tube to convert the color temperature of the light incident on the image pickup tube to the original setting value. It was common practice to adjust the white balance by

With this method, each time the color temperature of the light source changes, a color temperature conversion filter must be installed in front of the lens or between the lens and the image pickup tube, which is not only time-consuming, but also requires a change in color temperature conversion filter. essentially has an attenuation characteristic, which has the disadvantage of causing a loss of light quantity.

Furthermore, in simple color television cameras, a method is widely adopted in which when the color temperature of the light source changes, the ratio of the R (red) signal and the B (blue) signal is changed in accordance with the change. Specifically, as shown in FIG. 1, the R signal is divided by a variable resistor VR ₁ and resistors R101 to R104, and connected to terminals 1 to 4 of a changeover switch SW ₁ . On the other hand, the B signal is variable resistor VR ₂ , resistor R105 to R108
and is connected to terminals 1 to 4 of changeover switch _SW2 . Note that terminals 1 to 4 have set points corresponding to, for example, approximately 320〓 for a halogen lamp, approximately 4500〓 for a white fluorescent lamp, approximately 6000〓 for a daylight fluorescent lamp, and approximately 6000〓 for sunlight. Therefore, when the color temperature of the light source changes, changeover switches SW ₁ and SW ₂ are changed to greatly change the R and B gains to roughly adjust the white balance, and then the fine adjustment variable resistors VR ₁ ,
You can fine-tune the R and B gains by varying VR ₂ , and adjust the white balance by changing the R and B gain ratios. However, in order to adjust the white balance according to changes in color temperature using this method, even if switch SW ₁ and SW ₂ can be configured to work together, it is necessary to adjust three adjustment knobs: the switch and two variable resistors. The disadvantage is that it is necessary and difficult to adjust. Particularly for general users, it is extremely difficult to adjust the white balance by adjusting the R and B gains independently using separate knobs.

In order to improve the above-mentioned drawbacks, the present invention investigated how the R and B output ratios change when the color temperature of the light source is changed, and uses a single control signal to adjust the R and B signal gains according to the color temperature changes. By performing different gain controls in the two colors, it is possible to easily adjust the white balance in response to changes in color temperature.

An embodiment of the present invention will be described below based on the drawings. Figure 2 shows a white subject with the same illuminance (brightness signal Y constant) when the color temperature of the light source is approximately 3200〓 and the color temperature of the light source is changed after adjusting the white balance of the color television camera. This shows the vector locus on the vector scope for points 201 to 204, where the light sources are halogen lamps (color temperature approx. 3200〓), white fluorescent lamps (color temperature approx. 4500〓), and daylight color fluorescent lamps (color temperature approx. 6000〓). 〓) and sunlight (color temperature approximately 6000〓).
These are the R and B outputs (R
〓, B〓) to the R, B output (R3200〓, B3200〓) in a 3200〓 light source as shown in Figure 3, and the R, when the color temperature changes,
You can see how the B output ratio changes. For example, 6000〓
For sunlight, the R signal is approximately 3200〓.
It has become 0.65 times larger, and the B signal has become about 1.63 times larger.
Therefore, in order to match the white balance at each color temperature, the gain GR of R and B outputs must be adjusted.
〓, GB〓 at 3200〓, gain GR3200〓,
GB3200〓, each R〓/R3200〓, B〓/
All you have to do is multiply it by the reciprocal of B3200〓. FIG. 4 shows this relationship, and shows that if this relationship is maintained and the gains of the R and B outputs are varied, the white balance can be adjusted to changes in color temperature. In other words, it is not necessary to adjust the gains of the R and B outputs independently to match the white balance.If the gain changes of the R and B outputs by the color temperature adjustment device are set to maintain this relationship, adjustment errors can be easily avoided. You can adjust the white balance.

The present invention realizes the above-mentioned principle, and FIG. 5 shows a configuration diagram of the principle using a single-tube color camera as an example. A striped color filter 502 is arranged in front of the face plate of the image pickup tube 501, and is configured so that a color signal can be obtained from the output of one image pickup tube. The output of this image pickup tube 501 is amplified by a preamplifier 503, and then separated into Y, R, and B signals by a separation signal 504 of luminance signal Y, red signal R, and blue signal B, and the R and B outputs are each subjected to color temperature correction. After the gain is controlled by gain controllers 505 and 506, the Y signal is subtracted by subtracters 510 and 511,
The color difference signals R-Y and B-Y are output to the encoder 51.
2 and separately to encoder 512.
The signal is encoded and taken out from the output terminal 513 as an NTSC signal. gain controller 505,
The gain of 506 is the resistance R507, VR508, R
509, which is controlled by a DC control voltage from a resistor voltage divider, and if the gain at the control voltage corresponding to a certain color temperature (3200〓 in this example) is 1, the control voltage can be changed. The gain changes of the gain controllers 505 and 506 when
The relationship between GR and B gain GB is such that the relationship shown in FIG. 4 is maintained. Therefore, when the color temperature of the light source changes, by changing the position of the intermediate tap point of the variable resistor VR508 and changing the control voltage, the white balance will be matched at a certain control voltage, and the white balance can be adjusted with one adjustment. can be combined.

In the above principle configuration diagram, the characteristics of the color temperature correction gain controllers 505 and 506 for the R signal and the B signal are different, but as an actual usage example, as shown in FIG. It is practical to use the same characteristics for both signals and to realize the characteristics shown in FIG. 6 by manipulating the control voltage. FIG. 7 is an example of the actual use of the color temperature correction section in FIG. 5, in which the R and B signals are controlled by gain controllers 505 and 506' having the same characteristics as curve A in FIG. Then, the gain is controlled. The control voltage led to the gain controller 505 for the R signal is connected to the resistor R50.
7, VR508, and R509, whereas the control voltage led to the gain controller 506' for the B signal is the direct current voltage obtained directly by the resistive voltage divider by the curve H in FIG. The voltage is led to an inverting amplifier 702 through a non-linear circuit 701 having the characteristics shown in FIG. Therefore, the characteristics of the B signal gain controller 506' with respect to the DC voltage from the resistor voltage divider are generally the same as the characteristics shown in curve B of FIG. 6, and the principle of the present invention shown in FIG. will be achieved.

Note that the input/output characteristics of the nonlinear circuit 701 shown by curve C in FIG. 8 can be easily achieved with a gamma circuit composed of resistors, diodes, and the like.

In the above description, manual color temperature correction has been described, but it is clear that the present invention can also be applied to automatically achieve color temperature correction. In other words, the circuit can be simplified by automatically controlling the gain of either the R or B signal and using the control signal to control the gain of the other signal so as to maintain the above relationship.

As described above, according to the present invention, by changing the gains of the red (R) and blue (B) signals with respect to color temperature changes while maintaining an inverse relationship, color temperature correction can be performed with a single control means. , color temperature correction can be simplified. In particular, the effect will be great if it is introduced into simple color television cameras, which will likely be used by general consumers who are not familiar with color television cameras.

[Brief explanation of the drawing]

Figure 1 is an example of a conventional manual color temperature correction circuit, and Figure 2 is an example of a white subject on a vectorscope with the same illuminance when the color temperature of the light source is changed after adjusting the white balance at 3200㎓. A diagram showing the vector trajectory, Figure 3 is a characteristic diagram showing how the R and B outputs change at that time, and Figure 4 is a characteristic diagram showing how the gain changes in the R and B signals to adjust the white balance at each color temperature. 5 is a principle block diagram showing one embodiment of the present invention, FIG. 6 is a characteristic diagram of the gain controller for color temperature correction shown in FIG. 5, and FIG. 7 is a concrete diagram showing the main parts of the present invention. A configuration example diagram, FIG. 8, is an input/output characteristic diagram. 501... Image pickup tube, 504... Y, R, B signal separation device, 505, 506... Gain control device for color temperature correction, R507, VR508, R509...
Resistance voltage divider, 510, 511...Subtractor, 701
...Nonlinear circuit, 702...Inverting amplifier.

Claims (1)

[Claims] 1. In a color television camera, when the color temperature of the light source changes, the gain of either the red (R) or blue (B) signal is linearly changed, and the gain of the other signal is changed by changing the gain of the other signal. A color temperature correction device equipped with a single control means that changes the temperature inversely proportional to the gain of the color temperature and non-linearly. 2. Adding a single DC control signal generated by a color temperature adjustment knob composed of a single variable resistor to the gain control circuit for either the red (B) or blue (B) signal, The signal gain is varied linearly, and the single DC control signal is applied to the gain control circuit of the other signal via a nonlinear circuit to vary the signal gain inversely proportionally and nonlinearly. A color temperature correction device according to claim 1, wherein the color temperature correction device is configured as follows.