JPS6314554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a black balance adjustment circuit that adjusts the black balance of an image when incident light is reduced to substantially zero, and a black balance adjustment circuit that automatically adjusts the aperture of a lens according to the brightness of an object to be imaged. The present invention relates to a television camera each equipped with an automatic aperture device for adjusting the diaphragm.

When operating a color television camera, it is necessary to adjust the white balance and black balance before taking an image. For example, if you adjust the color temperature indoors,
Even if you are able to capture the correct color when using a standard light source of 3200 degrees, the color temperature will be around 6000 degrees outdoors, and the white parts of the TV image will be colored, or the black parts will become the correct black color. If you don't do it, you'll get it. For this reason, before taking an image, a white object is imaged, and the television camera is adjusted (white balance) so that the white color appears correctly. In addition, the TV camera is adjusted (black balance) so that the light that enters the camera is blocked and the black color appears correctly on the screen.

FIG. 1 shows a conventionally known adjustment circuit for achieving black balance as described above. In this adjustment circuit, automatic adjustment is performed so that the levels of R, G, and B signals obtained from the television camera are equal to each other when the incident light is zero. In FIG. 1, any two of the above R, G, and B signals
Two (R and B in the figure) are supplied to AGC circuits (automatic gain control circuits) 1 and 2. The outputs R' and B' of AGC circuits 1 and 2 and the G signal are matrix circuit 3.
The luminance signal Y, Q signal, and I signal are formed. Further, the output R' and G signal of the AGC circuit 1 are supplied to an operational amplifier 4, and the output of this operational amplifier 4 is supplied to a control terminal of the AGC circuit 1 via a memory circuit 6. Similarly, the output B' and G signal of the AGC circuit 2 are supplied to an operational amplifier 5, and the output of this operational amplifier 5 is sent via a memory circuit 7.
It is supplied to the control terminal of AGC circuit 2.

To explain how to achieve black balance using the adjustment circuit shown in FIG. 1, first, cover the lens of the television camera with a lens cap or manually operate the aperture to block the incident light. Next, when a black balance switch (not shown) is operated to put the adjustment circuit shown in FIG.
AGC circuit 2, operational amplifier 5 and memory circuit 7
The control loops consisting of the following are respectively in operation. These control loops operate so that the input levels of the operational amplifiers 4 and 5 are equal to each other. That is, so that G'=R and G=B',
Outputs R and B of AGC circuits 1 and 2 are memory circuit 6,
It is controlled according to the output of 7. As a result, when balance is achieved, R'=G=B'. At this time, the control voltages supplied to the AGC circuits 1 and 2, respectively, are stored in the memory circuits 6 and 7. Therefore, even if the control loop of FIG. 1 is rendered inactive by turning off the black balance switch, the above-mentioned adjustment circuit can be maintained in a black balanced state. If the television camera is operated in this state, it is possible to obtain a television image in which the black parts of the image are properly black.

As mentioned above, conventionally, in order to balance the black of a television camera, the light incident on the camera was first blocked and then the black balance switch was pressed, which resulted in the problem of complicated and time-consuming operation. Ta.

The present invention has been made in view of the above-mentioned problems, and includes a black balance adjustment circuit that adjusts the black balance of an image when the incident light is substantially zero, and a black balance adjustment circuit that automatically adjusts the black balance of an image according to the brightness of the object to be imaged. In each television camera, the television camera is equipped with an automatic aperture device that adjusts the aperture of the lens, and a control signal is sent to the automatic aperture device to close the aperture in response to operation of an operation switch that starts the black balance adjustment. At the same time, a delay means is provided in response to the operation of the operation switch, and the black balance adjustment circuit is operated after the aperture is closed. With this configuration, simply by operating the operation switch that adjusts the black balance, the light is automatically blocked, and the adjustment circuit operates only after the diaphragm is completely closed, preventing erroneous adjustments. I try not to.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block circuit diagram of a black balance adjustment circuit to which the present invention is applied. Note that in FIG. 2, the same parts as in FIG. 1 are designated by the same reference numerals, and explanations thereof will be omitted.

Generally, television cameras are equipped with an auto-iris device that automatically adjusts the aperture of a lens according to the brightness of an object to be imaged. FIG. 2 shows a part of this auto-iris device. In FIG. 2, an amplifier 10 is supplied with a luminance signal Y obtained from a television camera. This amplifier 1
The output of 0 is sent as an auto iris signal from the output terminal 12 to the servo circuit (not shown) via the resistor 11.
The output of this servo circuit drives a motor linked to the iris (diaphragm) to automatically adjust the iris. The auto iris signal is set so that when the level is 7V, the iris is in the open state, when the level is 2V, the iris is in the closed state, and when the voltage is between these levels, the iris is in the intermediate open/close state.

The changeover switch 14 is a black balance switch that is operated when performing black balance, and one fixed contact terminal 14a is supplied with a voltage of +9V, and the other fixed contact terminal 14b is at ground potential. Further, the movable contact terminal 14c of the changeover switch 14 is connected to the operation control terminal K of each of the memory circuits 6 and 7. Furthermore, the output terminal 12 of the auto iris signal is a diode 13.
It is connected to the movable contact terminal 14c via.

In the adjustment circuit shown in FIG.
When the movable contact is connected to the fixed contact 14b to achieve black balance, the auto-iris signal output terminal 12 is clamped to approximately the ground potential through the diode 13. Therefore, almost 0V is supplied to the servo circuit of the auto iris device. Therefore, the iris of the television camera is closed and light entering the camera is blocked. At the same time, the operation control terminals K of the memory circuits 6 and 7 become ground potential, and the memory circuits 6 and 7
are in the operating state. As a result, the control loop consisting of AGC circuit 1, operational amplifier 4, and memory circuit 6 and the control loop consisting of AGC circuit 2, operational amplifier 5, and memory circuit 7 are in the operating state, respectively, in the same way as in the case described above. Become. And R′=
The black balance is adjusted so that G=B'.

Although this black balance adjustment is electrically instantaneously performed by the above-mentioned control loop, it takes about 1.5 seconds from when the changeover switch 14 is operated until the iris of the camera is completely closed. For this reason, a time constant circuit 15 is provided as a delay means between the selector switch 14 and the control terminals K of the memory circuits 6 and 7 so that the black balance adjustment operation is performed approximately 2 seconds after the selector switch 14 is operated. is provided. Furthermore, a display means that lights up approximately two seconds after the changeover switch 14 is operated may be provided, for example, in the viewfinder of the television camera, thereby indicating that the black balance has been perfectly achieved.

Next, when the changeover switch 14 is returned to the fixed contact 14a side, the operation control terminals K of the memory circuits 6 and 7
It becomes a high level of 9V. Therefore, these memory circuits 6 and 7 are fixed in a state where the output voltages of the operational amplifiers 4 and 5 are maintained in a black-balanced state. Therefore, from now on, the television camera can be operated to take images with the black balance maintained. Further, since a voltage of +9V is applied to the anode side of the diode 13, this diode 13 is turned off. As a result, the auto-iris signal from the amplifier 10 is applied to the servo circuit, so that the auto-iris device operates normally.

As described above, the present invention is such that, in response to the operation of an operation switch that activates the black balance adjustment circuit of a television camera, a control signal that closes the aperture of the camera lens is supplied to the automatic aperture device. I made it. Therefore, even if you do not perform a separate operation to substantially block the light incident on the television camera, operating the black balance operation switch automatically shuts off the light, making it very easy to adjust the black balance. It's easy to do.

In addition, a delay means that responds to the operation of the operating switch is provided so that the black balance adjustment circuit is operated after the diaphragm is completely closed, so even if there is a time delay in the operation of the diaphragm device, the black balance adjustment circuit can be operated even if there is a time delay in the operation of the diaphragm device. Accurate black balance adjustment is performed and high quality imaging output can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a conventionally known adjustment circuit for adjusting the black balance of a television camera, and FIG. 2 is a block circuit diagram of a black balance adjustment circuit to which the present invention is applied. In addition, in the symbols used in the drawings, 1,
2 is an AGC circuit, 4 and 5 are operational amplifiers, 6 and 7 are memory circuits, 14 is a changeover switch, and 15 is a time constant circuit.

Claims (1)

[Claims] 1. A black balance adjustment circuit that adjusts the black balance of an image when the incident light is substantially zero, and an automatic system that automatically adjusts the lens aperture according to the brightness of the object to be imaged. and a diaphragm device, in response to operation of the operation switch that starts the black balance adjustment, a control signal for closing the diaphragm is supplied to the automatic diaphragm device;
The television camera is provided with a delay means responsive to the operation of the operation switch, and operates the black balance adjustment circuit after the aperture is closed.