JPH0252586A - Video signal correction circuit for color television camera - Google Patents

Abstract

PURPOSE:To attain color reproduction with well color balance at all times even if the shutter speed is changed during camera operation by storing a correction value of an amplification factor of an amplifier of each color channel in response to the shutter speed into a memory in advance. CONSTITUTION:A microcomputer 3 closes switches 9R, 9B switching whether or not an output of detection circuits 8R, 8B is fed to control circuits 7R, 7B by the instruction of a correction value generation command circuit 6, generates the correction value of the amplification factor to amplifiers 2R, 2B and stores the result in a memory 4. When no instruction comes from the circuit 6, the switches 9R, 9B are opened and the computer 3 corrects the amplification factor of the amplifier in response to the shutter speed set by a shutter speed setting circuit 5 depending on the correction value stored in the memory 4 to keep the color balance between the video signal outputs of the R, G and B channels constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal correction circuit for a color television camera with a shutter function capable of changing the shutter speed.

[Prior Art] Recently, television cameras have been proposed that are equipped with a shutter function that changes the shutter speed by changing the readout speed of an image sensor such as a CCD.

[Problem to be solved by the invention] In this type of television camera, even if the R, G, and B signal levels are the same when the white balance is set in advance, when the shutter speed is changed, the R, G, B
Due to the difference in the linearity of the image sensor between multiple channels, level differences will occur between the R, G, and B signals unless the white balance is adjusted again.
The color balance is off.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a video signal correction circuit that improves color reproducibility by eliminating the shift in color balance that occurs when changing the shutter speed in the above-mentioned color television camera with a shutter function. It is in.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides an imaging device that has an imaging device installed for each of a plurality of color channels corresponding to the three primary colors, and that can change the shutter speed. a means for amplifying the imaging output of the plurality of color channels from the imaging means and outputting a video signal of each color channel, the means having a plurality of amplifiers provided for each of the plurality of color channels; tQ means storing data related to amplification factors for each of the plurality of amplifiers predetermined to control the signal level ratio of each video signal from the plurality of amplifiers so as to achieve white balance; means for reading out data corresponding to the amplification factor from the storage means in accordance with the changed shutter speed when the shutter speed is changed; and in accordance with the read data;
The present invention is characterized by comprising means for adjusting the amplification factors of the plurality of amplifiers.

[Function] In the present invention, data related to the relative amplification factors of each of the amplifiers for taking out video signals of each color channel, for example, n, G, and B, is stored in memory in advance as a correction value according to the shutter speed. If you change the shutter speed while the TV camera is in operation, the I/O will be adjusted accordingly.
Since the signal level of the video signal of each color channel such as t, G, and B can be automatically adjusted, correct color reproduction with well-balanced color can always be achieved.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the invention, where In IG
and Ill are respectively R, G, and B channel image pickup devices, such as CODs, and have a shutter function. 211.2G and 2B are amplifiers in a signal processing circuit that receives outputs from the image sensors IR, IG, and 1B, respectively. Here, for the sake of simplicity, the remaining parts of the signal processing circuit for each channel are omitted and only the amplifiers are shown. shall be taken out.

Reference numeral 3 indicates a microcomputer, 4 a memory such as RAM, 5 a shutter speed setting circuit, 6 a correction value creation instruction circuit, 7R and 7B an amplifier 2R, respectively.
and an amplification factor control circuit for 2B. 8R and 8B are an R video signal, a G video signal, and a G video signal, respectively.
This is a detection circuit that detects the signal level difference between the video signal and the B video signal. Note that the D/A converter and A/D of the control circuits 7R and 7B and the detection circuits 8R and 8B
The functions of the digital processing circuit portions other than the converter portion can also be realized by the microcomputer 3.For convenience of explanation, the functions of the digital processing circuit portions are shown as separate circuit portions.

9R and 9B are detection circuits 8R and 8B, respectively.
This is a switch for switching whether or not to supply each output to the control circuits 7R and 7B, and when a correction value creation instruction is issued from the correction value creation instruction circuit 6, it is opened by the microcomputer 3, and the microcomputer 3 Amplifiers 2B and 2 according to the outputs of 8R and 8B
Create a correction value for the amplification factor for B. On the other hand, when the above instruction is not given, these switches 9R and 9B are open, and the microcomputer 4 transfers the correction values previously created and stored in the memory 4 from the shutter speed setting circuit 5. The control circuits 7R and 7B read out according to the set shutter speed.
, thereby correcting the amplification factors of each amplifier 2R and 2B according to the set shutter speed, thereby adjusting the relative signal level between amplifiers 2R, 2G and 2B, and adjusting the relative signal level between R, G and 2B. To maintain a constant color balance between each video signal output of a B channel.

Next, an example of a control procedure for creating a correction value executed by the microcomputer 3 is shown in FIG. In this example, for simplicity, the shutter speed is l/60° 1/250,115
There are 4 types: 00 and l/1000, and the target is l/60! In this example, when the shutter speed is 1/60, it is the standard maximum image state. Therefore, it goes without saying that the standard speed may be other than this example depending on the method. In flowchart 1 of FIG. 2, index A indicating the shutter speed is determined as shown in Table 1 below.

Table 1 Furthermore, in Figure 2, R(8) and B(Δ) indicate the gains of each amplifier 2R and 2B, and the center is R(8).
-10 times, B(Δ)~100*.

First, in step SO, it is determined whether an instruction has been issued from the correction value creation instruction circuit 6, and if an instruction has been issued,
In step S1, the switches 9R and 9B are closed, and in the next step S2, the shutter speed is set to A-1, that is, 1/60. It is assumed that a white object is cast in the deepest shadow using illumination light with a color temperature of 3000°.

In the next step S3, R(8)-100 houses, 1
1(8)-100*, and further, in step S4, analog outputs of It(8) and 11(8) are obtained from the D/8 converters in control circuits 7B and 7B, and outputted to amplifiers 2R and 2B. , respectively, supply;
Let the gains of each amplifier be these R(8) and n(A)
Switch by the value of .

The R, G, and B video signals obtained thereby are converted into digital signals in the detection circuits 8B and 8B in the /D converter (step S5), and then in sequential steps S6 to S13, the R, G, and B video signals are Adjust R(A) and [1(A) so that there is no difference in signal level of the video signal between the B and G channels.

In the next step 514, the resulting gain changes ffl:R(A) and [1(8) are stored in the memory 4 as control variables.

Furthermore, in the next step 515, the shutter speed is changed until the shutter speed becomes Δ・2,3.4.
Step 516) repeating the process of 514). The control amounts obtained as described above are shown in Table 2 below, for example.

Table 2 The control amounts in Table 2 indicate values when a white subject is photographed using illumination light with a color temperature of 3000°, so as the color temperature changes, the control amounts also change. Therefore, in the next step S17, with the shutter speed l/60 end control ff1R(1) and B(1) as the reference, the control ff1Il(A) and B(8)(^・2,3
4) as correction amounts, and these correction amounts are stored in the memory 4 in step 518. The correction amounts stored in the memory 4 are as shown in Table 3 below.

Table 3 Therefore, when the shutter speed changes, this correction value is set to the standard speed l/60 regardless of the imaging conditions.
It is sufficient to add it to the control ff1R(1) and B(1) at the time.

When actually making a correction based on the correction value obtained as described above, the switches 9R and 9B are opened because the instruction from the instruction circuit 6 has disappeared. When the shutter speed is set by the setting circuit 5, the microcomputer 3 changes each readout speed for the image pickup elements In, IG, and IB to change the shutter speed, and also performs correction corresponding to the set speed from the memory 4. Read the value. According to these correction values, the control circuits 7R and 81 (change the amplification factors of the amplifiers 2R and 2B,
The signal level between the video signal outputs of each R, G, and B channel is controlled so that color balance is maintained.

For example, assuming the current shutter speed 760, each control amount in the control circuits 7R and 7B is 1(1)-1
00%, B(1)-100 zero. When the shutter speed changes from 1/60 to 1/250, the control circuits 7R and 7B read the correction value R5(2)- from the memory 4.
LX and O5(1)-+z* are read out and added to the control amounts It(1) and B(1), respectively. The control amount obtained thereby is R(2)-99 zero and B(2
)-102! The amplification factors of the amplifiers 2R and 2B are controlled according to these control amounts.

Furthermore, when the shutter speed changes from 1/250 to 11500, the control amount 1t(2)-9H and B
(2)-+o2%, J: ”) l/250 throat@
I) Correction m R5(2)-I! and 115 (2
)-+296 and add the corrections ff1Is (3)-2 zero and BS (3)-+8 for 11500, respectively. Control ff111 obtained thereby
(3)・9896 and [1(3)-103! The amplification factors of amplifiers 2R and 2B are controlled by l;.

Above, l/liO, 1/250, 11500, 1/1
Although the case of four types of shutter speeds of 000 was illustrated,
Furthermore, even if the speed can be changed in multiple stages, it can be realized by making the memory capacity sufficiently large.

Alternatively, it is also possible to select any desired speed from among these multiple speeds and execute the process as in the above example at that point.

In addition, in the above example, two of the three channels R, G, and B
Although the signal level is adjusted only for channels R and B, the amplification factors may be adjusted relatively for the two channels R and G or G and B, or alternatively,
It is also possible to adjust the amplification factors individually for all three channels, RG and B.

Furthermore, in the above example, the case where there are three channels of R, G, and B as a plurality of color channels corresponding to the three primary colors is illustrated, but the present invention is not limited to this case only; Of course, the present invention can also be applied to a case of 3 channels, a case including a color channel, or a simple type of imaging means that uses a 2-channel imaging device and extracts the imaging output in the form of a color difference signal. be.

[Effects of the Invention] As is clear from the above, according to the present invention, even if the shutter speed is changed during operation of the television camera, the signal level of the video signal of each color channel such as R, G, and B is adjusted accordingly. can be adjusted automatically, ensuring accurate color reproduction with good color balance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a flowchart showing an example of its control procedure. In, IG, in...Image sensor, 211.2G, 211...Amplifier, 3...Microcomputer, 4...Mesori, 5...Shutter speed setting circuit, 6...Correction value Creation instruction circuit, 7R, 7B...Amplifier control circuit, 8n, 8B...Level difference detection circuit, 911.9[1...Switch that is closed when creating a correction value. 77th construction drawing of the actual date and month color A row of this publication

Claims (1)

[Scope of Claims] 1) Imaging means having an imaging device provided for each of a plurality of color channels corresponding to three primary colors and capable of changing shutter speed; and a plurality of amplifiers provided for each of the plurality of color channels. means for amplifying the imaging output of the plurality of color channels from the imaging means and outputting a video signal of each color channel; storage means storing data related to amplification factors for each of the plurality of amplifiers predetermined to control the signal level ratio of the plurality of amplifiers so as to achieve white balance; means for reading out data corresponding to the amplification factor from the storage means in accordance with the shutter speed that has been read out; and means for adjusting the amplification factors of the plurality of amplifiers in accordance with the read data. A video signal correction circuit for color television cameras featuring: