JPS6362155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color temperature correction circuit for a color camera, and in particular, by digitally presetting the color temperature in the standard mode, variable settings in bit units as the minimum unit of control are possible for color cameras. This can be done easily from the circumferential surface.

A commonly used color camera is configured, for example, as shown in Fig. 1, in which light from a subject is focused through a lens system 1 onto a photoelectric conversion surface 2 of an image pickup tube or image pickup plate, and is converted into an electrical signal. is converted to The electric signal extracted at the photoelectric conversion surface 2 in this way is converted into three-color signals corresponding to the first to third color lights such as green G, red R, and blue B at the color separation section 3. After being separated, the signals are amplified to a specified value in independently provided amplifier circuits 4, 5, and 6, respectively. The amplified color signals are combined in a combining circuit 7 using a matrix circuit or the like to generate a Y signal as a luminance signal, and the combining circuit 8 combines the Y signal and other two color signals. By combining B and R respectively, a color difference signal B-Y
and RY are generated. The color difference signals B-Y, RY generated in this way are modulated by the color carrier signal supplied from the drive signal generation circuit 10 in the process circuit 9, and are sent to the mixing amplifier as a carrier color signal. 11. The mixing amplifier 11 inputs a luminance signal and a carrier color signal, and also inputs a synchronization signal, a color burst signal, and other various pulse signals supplied from the drive signal generation circuit 10 and performs a mixing process, thereby outputting an output terminal. 12 to generate color television signals according to the NTSC standard system.

Here, the color camera is provided with a color temperature correction function in case the color temperature of the subject changes. When correcting this color temperature, there are two methods: one is to use a filter to correct the color temperature of the incident light, and the other is to electrically control the color signals. A configuration is generally used in which the amplification degree of amplifiers 4 to 6 that independently amplify each of the signals is varied. When correcting this color temperature, the amplification degree of the amplifier 4 in charge of the reference color signal (generally green) is fixed, and the amplification degree of the amplifiers 5 and 6 in charge of the other two colors is varied. A method is being taken to do so.

FIG. 2 shows the side surface of a conventionally commonly used color camera on which the color temperature adjustment mechanism is provided, and a filter is installed at the front side of the color camera body 13 depending on the place of use, such as indoors or outdoors. The configuration is provided with a knob 14 for switching, and volumes 15 and 16 for controlling the amplification degree of the amplifiers 5 and 6.

However, since the color temperature correction with the above configuration is analog controlled, it is difficult to preset the standard state with high precision, and if this is attempted, it will be extremely expensive.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color temperature correction method for a color camera that allows easy presetting of color temperature in standard mode.

To achieve these objects, the present invention provides a digital camera that controls the amplification degree of each amplifier by the output of an up-down counter, and that allows the preset value of this up-down counter to be controlled from outside the camera body. It is specified in bits by a switch. Hereinafter, a color temperature correction method for a color camera according to the present invention will be described in detail with reference to the drawings.

FIG. 3 is a circuit diagram showing an embodiment of the color temperature correction method for a color camera according to the present invention, and the same parts as in FIG. 1 are shown using the same symbols. In the figure, 17 indicates an amplified first color signal G and an amplified second color signal R that serve as a reference in automatic mode.
The second color signal R for the first color signal G is compared with
a comparator circuit 19 which generates an up-down control signal A corresponding to the direction of deviation of the color signals and also generates a gate control signal B which controls the gate circuit 18 to close until the first and second color signals G and R match; The up-down mode is switched by the up-down control signal A, and the clock pulses CP supplied via the gate circuit 18 are sequentially counted.
a preset counter that presets the signals supplied to the input terminals _S1 to _S4 when an "H" signal is supplied to the preset control terminal PS via the switch 20;
Reference numeral 21 denotes a preset value generating section, which includes four digital switches 21a to 21a provided in each pit.
21d. 22a-22d
is a resistor connected in series between the input and output of the amplifier 5 that amplifies the color signal, and each of the resistors 22a to 22d has a resistance value of R, 2R, 4R, and 8R, respectively, and constitutes a feedback circuit. . 23 is an analog switch circuit, which is connected in parallel to each of the resistors 22a to 22d, and is closed by a signal outputted from each bit output terminal _Q1 to _Q4 of the preset counter 19. Switch 23a-2
It has 3d. Note that 24 is an input end for the color signal R, 25 is an input resistor, and 26 is an output end.

In the circuit configured as described above, when the level of the second color signal R supplied to the comparator circuit 17 becomes higher than the level of the first color signal G in the automatic mode, the comparator circuit 17 outputs the up control signal A. The preset counter 19 is set to the up mode, and the gate control signal B is generated to close the gate circuit 18. As a result, the clock pulse CP is supplied as a clock signal to the preset counter 19 via the gate circuit 18, so that the preset counter 19 sequentially counts the clock pulse CP and the count output increases. When the count output increases, the upper portions of the analog switches 23a to 23d provided in the analog switch section 23 are turned on, and accordingly, the negative feedback resistance value decreases and the amplification degree is lowered. When the amplification degree is lowered, the level of the second color signal R input to the comparison circuit 17 is sequentially lowered, and the first and second color signals G, R
At the point in time when the values match, the up control signal A and the gate control signal B are cut off and the preset counter 19 is fixed. Further, when the level of the second color signal R is smaller than the level of the first color signal G, the down control signal A is generated from the comparator circuit 17, the preset counter 19 is set to the down mode, and the gate Control signal B is generated to close gate circuit 18. As a result, the preset counter 19 is counted down every time the clock pulse CP is supplied, and its output is sequentially decreased, and the analog switches 23a to 23d of the analog switch section 23 are closed in response to this output value. Therefore, since the negative feedback resistance value gradually decreases, the degree of amplification is increased and the level of the second color signal R is increased. Then, the first and second color signals G,
When the R levels match, the down control signal A and the gate control signal B are cut off, the count value of the preset counter 19 is fixed, and the color temperature is maintained in a balanced state.

Next, when the switch 20 is closed, an "H" signal is supplied to the preset control terminal PS of the preset counter 19, and the preset mode is entered. When the preset mode is entered in this manner, the preset counter 19 receives and holds the outputs of the digital switches 21a to 21d provided in the preset value generating section 21 as respective bit signals at the input terminals _S1 to _S4 . Therefore, in this preset mode, the amplification degree changes in accordance with the set output of each bit by the digital switches 21a to 21d, and accordingly, the color temperature correction in the standard mode changes. This makes it suitable as a preset. In this case, the analog switches 23a to 23 controlled by the 4-bit output
A negative feedback resistor 22 that is short-circuited by 3d.
Since the values of a to 22d are set to 1, 2, 4, and 8 times, the amplification degree can be changed to 16 types in total, which is sufficient for color correction of a color camera. Become.

FIG. 4 shows an example of a color temperature adjustment panel provided on the side of a color camera to which the circuit shown in FIG. You can switch between standard, automatic, and set. When the knob 22 is moved to the set position, the auto-white circuit is activated, and when the knob is released, the automatic position is restored. Therefore, the set position activates the auto-white circuit. Next, when the knob 22 is set to the standard position, the third
The switch 20 shown in the figure is closed and the preset counter 19 enters the preset mode. Therefore,
In this state, the color temperature is corrected in accordance with the preset value set by the preset value generating section 21. In addition, 23 is the third
This is a preset value generating section for color signal B. In such a configuration, each knob 2 of the preset value generators 21 and 23 is pressed in the standard mode.
By moving the knobs 4 and 25 according to the marker 26, the mode is set to the factory standard mode, and by moving the knobs 24 and 25, a preset value suitable for the user's preference is set.

In the above embodiment, a sliding digital switch was used to specify the preset value, but a rotary code switch may also be used.
The color temperature adjustment panel portion in this case is as shown in FIG.

As explained above, the color temperature correction method for a color camera according to the present invention is applicable to a color camera having a color temperature correction circuit that digitally controls the amplification degree of an amplifier that amplifies each color signal using the output of an up-down counter. By controlling the preset value of the counter using a digital switch operated from the side of the camera body, a preset value for color temperature correction in the standard mode is set. Therefore, although it has a simple configuration, it is possible to specify preset values reliably, and it has various excellent effects such as being able to incorporate external design by digitalization, which has become mainstream in recent years.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional color camera, FIG. 2 is a side view of the color camera shown in FIG. 1, and FIG. 3 is a circuit showing an embodiment of the color camera according to the present invention. Figure, Figure 4, Figure 5
The figure is a front view showing an example of a color temperature adjustment panel. 5... Amplifier, 17... Comparison circuit, 18... Gate circuit, 19... Preset counter, 20... Switch, 21... Preset value generator, 23... Analog switch circuit.

Claims (1)

[Claims] 1. Compare the signal levels of the first color light and the second color light and the first color light and the third color light in response to a change in the color temperature of any of the objects separated into three colors, and determine whether the second color light or In a color camera that corrects the color temperature by controlling the amplification degree of an amplifier that amplifies the signal of the third color light, a plurality of lights are attached to a part that can be operated from the outer periphery of the color camera body. A digital switch with a bit configuration, a comparator that compares the signal levels of the first color light and the second color light, and the first color light and the third color light, and a count up or count down depending on the comparison output of the comparator. an up-down counter that presets the output data of the digital switch when a preset mode is designated; and an up-down counter that amplifies the second color light or third color light signal under the control of the output of this up-down counter. Equipped with an analog switch that selects the resistance of the negative feedback resistor provided in the amplifier,
A color temperature correction method for a color camera, characterized in that a preset value of the amplification degree for the amplifier is variably adjusted in bit units as a minimum unit of amplification control by the digital switch operated from the outer periphery of the camera body.