JPS6412435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the color reproducibility of a simple color television camera that generates a color television signal that is bittonated by a standard color television receiver, and in particular of a frequency separation single-tube color camera. It is something.

For simple color television cameras,
Because three color signals are obtained from a single image pickup tube,
The color reproduction characteristics are not satisfactory due to various limitations such as the SN ratio. As a means of correcting this,
Although methods such as linear matrix have been reported,
The improvement effect is small compared to the negative effects such as complicating the circuit and decreasing the signal-to-noise ratio, so it is not generally put into practical use in simple color television cameras, and color reproduction characteristics have not been improved. It is.

However, especially in frequency-separated single-tube color cameras, the imaging characteristics of each primary color cannot be selected independently, so color reproduction characteristics have become a major problem. A major problem was the lack of vividness when capturing images of plants and trees.

FIG. 1 is a basic configuration diagram of a conventional frequency separation type single tube color television camera. In the figure, 1 is an image pickup tube with built-in cyan and yellow crossed stripe filters for the frequency separation method, and 2
3 is a preamplifier, and 3 is a low-pass filter (hereinafter abbreviated as LPF) for a luminance signal (hereinafter abbreviated as Y signal), which removes the component spatially modulated by the stripe filter. 4 is R (red)
It is a signal separation circuit, and in the case of a single frequency separation method,
A comb filter using a 1H delay line is used. Reference numeral 5 denotes a B (blue) signal separation circuit, which, like the R signal separation circuit 4, is composed of a comb filter. 6 and 7 are color difference signals (RY) and (B
-Y). 8 and 9 are an amplifier for the (RY) signal and an amplifier for the (B-Y) signal, and the ratio A ₁ :A ₂ of the amplification degrees A ₁ and A ₂ is the (R-Y) signal and (B-Y) signal amplifier. Y) The signal ratio is approximately 1/1.14:1/2.03 as shown in Figure 2 to match the NTSC system. 10 and 11 are balanced modulators (R
-Y) signal and (B-Y) signal, which perform balanced modulation on subcarriers whose phases are different by 90 degrees. 12
is an adder, which generates a modulated color signal (hereinafter C
) is obtained.

13 is a Y signal, a C signal, a burst signal to be described later,
Encoder that obtains NTSC signal from the same synchronization signal, 1
4 is an NTSC signal output terminal.

15 is a synchronizing signal generator, and output terminal 16
A subcarrier (hereinafter abbreviated as SC) is output from the subcarrier.
Then, this SC is gated by a burst flag pulse (hereinafter abbreviated as BF) outputted from the output terminal 17 of the synchronizing signal generator 15 by the gate circuit 21, and a burst signal is obtained. On the other hand, the SC is delayed in phase by 90° with respect to the burst signal by a 90° phase delayer 19 and is guided to the balanced modulator 10. Further, the output of the 90° phase delayer 19 is delayed in phase by 180° with respect to the burst signal by a 90° phase delayer 20, and then guided to the balanced modulator 11. Therefore, the burst signal,
The phase relationship among the (RY) modulation signal, the (B-Y) modulation signal, and the carrier color signal C is as shown in FIG. Note that 18 is an output terminal of the synchronizing signal generator 15 for generating a synchronizing signal.

In a frequency-separated single-tube color television camera configured as described above, the red, yellow, green, cyan, blue, and magenta color bar charts (ideally, the tips of the vectors indicated by the dotted line arrows in Figure 3) P ₁ , P ₂ , P ₃ , P ₄ , P ₅ , P ₆ ) are captured and reproduced on a standard color television receiver, each approximately as shown by the x mark in Figure 3. On the vector, it is reproduced at P ₁ ′ to _{P 6} ′, and the saturation of green is reproduced with extremely low saturation.

To correct this with the conventional configuration, (R-
The ratio of the Y) signal and the (B-Y) signal is 1/1.14:1/2.
Make some changes from 03 (to minimize changes in other colors and increase only the saturation of green,
(R-Y) There is a slight effect if the signal is made larger)
Although this method is conceivable, the change in the reproduction of other colors becomes large (in particular, the intensity of R and cyan becomes too high), so the gain ratio cannot be changed significantly, and the effect of improving the saturation of green is small.

The present invention has a relatively simple configuration, improves the saturation of green without significantly affecting the reproduction of other colors, and alleviates the above-mentioned drawbacks in color reproduction of the simple color television camera. be.

The present invention will be explained below.

It is clear that the best way to easily improve the saturation of green without affecting the color reproduction of other colors is to increase the gain on the green axis in the vector diagram of FIG. To achieve this, in the chromaticity vector diagram of the NTSC system shown in Figure 3, we need to create a color difference axis (referred to as the ξ axis) whose phase matches that of the green vector, and a color difference axis (referred to as the η axis) that is orthogonal to this (referred to as the ξ axis). A simple method is to select ξ-axis gain as the modulation axis and increase the gain of the ξ-axis from the standard gain of the NTSC system. color difference signal Eξ representing the ξ-axis and η-axis;
In order to express Eη by the signals R, B, and Y obtained from the image pickup tube, if the angle between the ξ axis and the (RY) axis is expressed by α from FIG. 4, the following relationship holds true.

Transforming the above equation (1), we get however, From this, from the R, B, and Y signals, Eξ=(E ₁ −
Create Y)・A ₁ signal and Eη=(E ₂ −Y)・A ₂ signal, and transmit these two signals with subcarriers delayed by (90° + α°) and (180° + α°) with respect to the burst phase, respectively. If quadrature two-phase modulation is performed, it will match the NTSC standard method, and if the gain of Eξ is made larger than this value, the effect on the reproducibility of other colors will be minimized, and the phase will be almost the same as the phase of the ξ axis. You can increase the saturation of colors in . If we make the phase of the ξ axis equal to the phase of the Green vector and increase the gain of Eξ, we get
The saturation of green can be improved.

At this time, the Eξ and Eη signals are expressed as α=29° using equation (2).
Substituting into equation (3), we get the following equation.

Eξ0.25(3R+B)-Y Eη{44(-R+B)-Y}×0.01...(4) E ₁ 0.25(3R+B), A ₁ 1 E ₂ 44(-R+B), A ₂ 0.01...(5) or more An example of a configuration for realizing the principle of the present invention is shown in FIG. The same parts as in FIG. 1 are given the same reference numerals, and only the different points will be explained together with their operations. The matrix circuit 22 uses the R and B signals obtained by the R signal separation circuit 4 and the B signal separation circuit 5.
The E ₁ signal and the E ₂ signal are obtained, and the subtraction circuits 23 and 24 produce (E ₁ −Y) and (E ₂ −
Y) Create a signal, amplify it by amplifiers 25, 26, and then lead it to balanced modulators 10, 11. If the gain ratio of amplifiers 25 and 26 is A ₁ /A ₂ , NTSC
In this case, the gain ratio of the amplifiers 25 and 26 is made larger than A ₁ /A ₂ in order to increase the gain of the color difference signal Eξ whose phase matches that of the reproduced color with low saturation. Ru. That is, amplifier 2
If the gains of 5 and 26 are respectively set as G ₁ and G ₂ , the relationship is G ₁ /G ₂ >A ₁ /A ₂ . Furthermore, by configuring G ₁ /G ₂ to be variable, the saturation of colors that are reproduced with low saturation can be adjusted in consideration of the reproducibility of other colors.

On the other hand, in the balanced modulators 10 and 11, the SC from the output terminal 16 of the synchronizing signal generator 15 is delayed by (90° + α°) with respect to the burst signal by a phase delayer 27 (90° + α°). The output of the (90° + α°) phase delayer 27 is delayed by 90° by the 90° phase delayer 20, and a subcarrier delayed by (180° + α°) with respect to the burst signal is derived. , Eξ and Eη are balanced modulated.

If we try to improve the saturation of green by matching the phase of the Eξ axis with the phase of the green vector, α = 29°, E ₁ 0.25 (3R + B), E ₂ 44 (-R +
B), G ₁ /G ₂ > 1/0.01.

FIG. 6 shows a second embodiment of the invention.

In the case of a color television camera, when a white subject is imaged, it must be reproduced as an achromatic color (this is called adjusting the white balance).
For this purpose, when imaging a white subject, for example, if the Y signal level is used as a reference, then R and B
Conventionally, the signal levels were adjusted so that the (RY) and (BY) signals became zero. That is, by observing the (RY) and (B-Y) signal levels, the R and B signal levels could be adjusted independently. However, in the first embodiment shown in FIG. 5, Eξ,
Since a signal of the form (k ₁・R + k ₂・B−Y) of Eη is obtained (k ₁ , k ₂ : coefficients), the levels of the R and B signals must be observed independently to adjust the white balance. This causes inconvenience because it cannot be adjusted. In order to eliminate this inconvenience, the second embodiment has a configuration in which the (RY) and (BY) signals are matrixed to obtain the Eξ and Eη signals. It is clear that even with this configuration, the present invention can be realized only by having the characteristics of the matrix circuit 28 different from those of the matrix circuit 22 shown in FIG. 5.
With such a configuration, the white balance can be adjusted by independently adjusting the levels of the R and B signals while observing the outputs of the subtracters 6 and 7.

As described above, according to the present invention, in a color television camera, the saturation of colors that are reproduced with low or high saturation can be corrected with a relatively simple configuration without significantly affecting the reproduction of other colors. In particular, green can be reproduced more vividly in frequency-separated single-tube color television cameras.

Note that the above explanation does not specifically mention the method of bitoning on the receiver side, but as mentioned above, the output signal from the color television camera of the present invention can be reproduced by a standard color television receiver. Since this is assumed, the gain ratio of the color difference signal on the bittone axis when bittone is performed on the receiver side is a ratio that matches the standard color television signal. Therefore, if the gain of an arbitrary color difference signal on the camera side is set to a value different from the value calculated by the standard color television system, the saturation of the color on the axis corresponding to that color difference signal will be changed. This will be reproduced on the cathode ray tube of the receiver to obtain the above-mentioned effect.

Furthermore, in the present invention, an arbitrary color difference signal is obtained and modulation is performed using a subcarrier wave whose phase matches the modulation axis of the color difference signal, so unlike conventional linear matrices, no S/N deterioration occurs. There is also an advantage.

In addition, in the above explanation, we have mainly explained a camera that reproduces green with low saturation, but it is clear that it can also be applied to cameras that reproduce other colors with undersaturation or oversaturation. .

Furthermore, although the second color difference signal Eη has been described as having an orthogonal relationship with the first color difference signal Eξ, it is clear that the present invention can be configured even if a color difference signal that is not orthogonal to the first color difference signal Eξ is selected.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of a conventional frequency separation method single-tube color television camera, Figure 2 is a diagram showing the phase relationship of color subcarriers in the NTSC system, and Figure 3 is a diagram showing the phase relationship of color subcarriers in the NTSC system.
The figures are vector diagrams showing the color reproduction of an ideal color television camera and a conventional frequency-separated single-tube color television camera. Figure 4 is a diagram showing the phase relationship of the modulation axes for quadrature two-phase modulation.
FIG. 6 is an electrical block diagram of each embodiment of a color television camera according to the present invention. 1... Image pickup tube, 3... Luminance signal low pass filter, 4... Red signal separation circuit, 5... Blue signal separation circuit, 6, 7... Subtractor, 10, 11... Balanced modulator, 12... Adder, 13... Encoder, 1
5...Synchronization signal generator, 20...90° phase delay device, 2
1... Gate circuit, 22... Matrix circuit, 2
3, 24...Subtractor, 25, 26...Amplifier, 2
7... (90°+α°) phase delay device, 28... Matrix circuit.

Claims (1)

[Claims] 1 A separation circuit that separates a luminance signal, a first color difference signal, and a second color difference signal from an image sensor output signal, and calculates the first and second color difference signals to change the saturation and reproduce the image. a matrix circuit for obtaining a third color difference signal in which a specific color to be selected is substantially on the axis thereof, and a fourth color difference signal in a substantially orthogonal relationship to the third color difference signal; and a gain of the third color difference signal. an amplifying means for changing the gain of the standard color television system in the direction of changing saturation, and an output signal of the amplifying means, the fourth color difference signal, and the luminance signal are encoded to obtain a composite color signal. A color television camera characterized by comprising means.