JP2716056B2 - Color video camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video camera capable of obtaining a video signal having good color reproducibility even under a white fluorescent lamp.

[Conventional technology]

FIG. 8 is a block connection diagram showing a conventional color video camera disclosed in Japanese Utility Model Publication No. 4116011, for example.
In the figure, 1 is a lens, 2 is an image sensor, 3 is a color separation circuit, 4 is an R channel gain control circuit, a gain control circuit (white balance adjustment gain adjustment circuit), and 5 is a B channel (white balance adjustment gain). Adjustment circuit), 6 is a process circuit, 7 is a matrix circuit, 8 is an encoder circuit, 9 is a synchronization signal generation circuit, 10 is an output terminal, 21 is an R sensor (photoelectric conversion element), 22 is a G sensor (photoelectric conversion element). , 23 is a B sensor (photoelectric conversion element), 24, 25 are division circuits, 28, 29 are linear conversion circuits, 30 changes the phase of a color subcarrier fscR-Y for modulating an RY color difference signal, An fscR-Y phase adjustment circuit as a color reproducibility compensation circuit for compensating the saturation and the hue, 31 changes the phase of the color subcarrier fscB-Y for modulating the BY dye signal to change the saturation and the hue. FscB-Y phase adjustment circuit as color reproducibility compensation circuit to compensate A.

Next, the operation will be described. The light image incident from the lens 1 is photoelectrically converted by the imaging device 2 and color-separated by the color separation circuit 3 into three color signals of R, G, and B. Next, the gain control circuit 4 controls the gain of the R signal of the R channel, and the gain control circuit 5 controls the gain of the B signal of the B channel. The gain control circuits 4 and 5 adjust the gains of the R signal and the B signal to adjust the white balance.

On the other hand, the R sensor 21, G sensor 22, and B sensor 23 generate outputs proportional to the R, G, and B components of the incident light. Now, assuming that the respective output values are R _S , G _S , and B _S , the ratio G _S / R _S (= V _R ) of the G component and the R component independent of the amount of incident light is output by the divider circuit 24. . Similarly, the division circuit 25 outputs the ratio B _S / G _S (= V _B ) between the B component and the G component. Here, the gain control circuit 4 is a control voltage V _R the gain is increased in accordance with increases, its gain decreases in accordance with the other of the gain control circuit 5 is the control voltage V _B increases. Further, in the case of a light source having a low color temperature, that is, a light source having a large R component and a small B component with respect to the G component, Indicates a value lower than that of a light source having a high color temperature. When the color temperature of the light source is low, the gain of the gain control circuit 4 for the R channel decreases, and the gain of the gain control circuit 5 for the B channel increases.

On the other hand, in the case of a light source having a high color temperature, that is, a light source having a small R component and a large B component with respect to the G component, the gain of the gain control circuit 4 for the R channel becomes large and the gain control circuit 5 for the B channel becomes large. The gain is smaller. As mentioned above,
White balance adjustment by automatically controlling the gain of the R channel gain control circuit 4 and the gain of the B channel gain control circuit 5 in response to changes in the R, G, and B components included in the light source. do. Further, if the color temperature changes due to the spectral sensitivity characteristic of the image sensor 2 or the signal processing method, the same signal is taken even if the same subject is imaged and the white balance is correctly adjusted.
V _R and V _B are linearly converted by linear conversion circuits 28 and 29 and applied to phase adjustment circuits 30 and 31. Thereby, the change in the phase of the color signal is corrected.

In addition, in such a color video camera, a vector diagram in the case where red, yellow, flesh color, and white charts are imaged under a fine afternoon (before sunset and a color temperature of about 4000 K) is shown in FIG.
As shown in the figure, white fluorescent lamp (color temperature about 4000K)
The vector diagram obtained when the red, yellow, flesh color, and white charts are captured under the following conditions is as shown in FIG. 10, and in each case, the voltage for controlling the gain of each of the gain control circuits 4 and 5 is shown in FIG. The values are almost equal, and the white balance adjustment is correctly performed.

Further, as another conventional example, the phase adjustment circuits 30 and 3 shown in FIG.
By connecting gain control circuits to the color difference signal RY and BY output lines connecting the matrix circuit 7 and the encoder circuit 8 instead of the matrix circuit 7 and the encoder circuit 8, the color difference signal R- There has also been proposed one that corrects a change in the amplitude of Y, BY.

Further, as another conventional example, instead of the phase adjusting circuits 30 and 31 in FIG. 8, a mixing circuit is provided on the line for outputting the color difference signals RY and BY connecting the matrix circuit 7 and the encoder circuit 8. In order to correct a change in phase by controlling the mixing ratio of each of the color difference signals R-Y and B-Y by the output of the linear conversion circuits 28 and 29, there has also been proposed a method in which the phase change is corrected.

[Problems to be solved by the invention]

Since a conventional color video camera is configured as described above, the color rendering properties of a white fluorescent lamp are usually poor. Therefore, as can be seen by comparing FIGS. The flesh color phase, amplitude, and the like become worse with a white fluorescent lamp. In particular, the flesh color phase is 123 ° in FIG. 9, which is a preferable phase, and is 137 ° in FIG. And the skin color is yellowish, which is a major problem in visual perception. In addition, since the skin color is a memory color, it is desirable to have a constant phase amplitude irrespective of the type of the light source. There were problems such as being noticeable with fluorescent lamps. The method of improving color reproduction focusing only on color temperature change is described in the 1986 National Institute of Television Engineers of Japan Preliminary Proceedings, pp. 81-82, "Improvement of color reproducibility in full color difference line sequential cameras". However, a sufficient effect has not been obtained for a light source having poor color rendering properties as described above.

Further, in the case where the gain control circuit is provided in place of the phase adjustment circuits 30 and 31 as described above, in particular, since the skin color is a memory color, reproduction is performed at a constant phase and amplitude regardless of the type of light source. It is desirable to use a conventional color video camera. Since the gains of the color difference signals RY and BY are controlled by the values obtained by linearly converting, for a light source having poor color rendering properties such as a white fluorescent lamp, a white fluorescent lamp Then, there was a problem that the phase amplitude changed as shown in FIG.

The present invention has been made to solve the above problems, even under a light source with poor color rendering properties such as white fluorescent lamp,
An object of the present invention is to provide a color video camera capable of obtaining good color reproduction.

[Means for solving the problem]

According to the color video camera of the present invention, an AC component included in the light source is detected by an AC detection circuit, and a linear conversion signal of an output of a division circuit or an optimal color reproducibility compensation control is determined according to the magnitude of the AC component. A signal is selectively output by a switching circuit to control a color reproducibility compensation circuit such as a color difference signal phase adjustment circuit, a gain control circuit, and a mixing circuit.

[Action]

The color reproducibility compensation circuit according to the present invention controls the color reproducibility compensation circuit by obtaining a color reproducibility compensation control signal obtained by converting the output of the division circuit into a table when the AC component contained in the light source is large. Then, like on a sunny afternoon,
To obtain a video image with optimal color reproduction even under a discharge lamp.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 26 is an AC detection circuit connected to the G sensor 22, 27 is a table converter, and 32 is a switching circuit for selecting the output of the linear conversion circuits 28 and 29 or the output of the table converter 27. The same blocks as those shown in FIG. 8 are denoted by the same reference numerals, and redundant description will be omitted.

Next, the operation will be described. First, in the present invention, the AC component of the amount of light contained in the light source is detected by the AC detection circuit 26, and when the AC component is small, the output of the linear conversion circuits 28 and 29 is selected by the switching circuit 32. Works the same as.

When the AC component included in the light source detected by the AC detection circuit 26 is large, the output of the table converter 27 is selected by the switching circuit 32.

The light source from which the AC component is detected is a discharge lamp mainly including a white fluorescent lamp and the like. If there is a condition that the AC component is large, it is possible to classify this discharge lamp by the outputs V _R and V _B of the division circuits 24 and 25, and therefore, the table converter 27 is most suitable for each discharge lamp. Voltages for controlling the phases of the color subcarriers fscR-Y and fscB-Y are input as color reproducibility compensation control signals to phase adjustment circuits 30 and 31 as color reproducibility compensation circuits.
Thereby, in the case of a white fluorescent lamp as shown in FIG. 10, compared with the case of FIG.
If fscB-Y is changed by about -15 °, almost satisfactory color reproducibility can be obtained as shown in FIG.

FIG. 3 shows another embodiment of the present invention. This is the first
Instead of the phase adjusting circuits 30 and 31 shown in the figure, gain control circuits 30A and 31A as color reproducibility compensating circuits are provided for connecting the color difference signals RY and BY connecting the matrix circuit 7 and the encoder circuit 8. Connected to. In addition, the same blocks as those shown in FIG. 1 are denoted by the same reference numerals, and overlapping description will be omitted.

In this embodiment, when the AC component included in the light source detected by the AC detection circuit 26 is large, the output of the table converter 27 is selected by the switching circuit 32.

The light source from which the AC component is detected is a discharge lamp mainly including a white fluorescent lamp. If there is a condition that the AC component is large,
The discharge lamps can be classified according to the outputs V _R and V _B of the division circuits 24 and 25, and the most suitable color difference signal R−
The Y, BY gain control voltages are output by the table converter 27. Thereby, in the case of a white fluorescent lamp as shown in FIG. 12, the RY color difference signal gain is increased by about 1.3 times and the BY color difference signal gain is increased by about 0.8 times as compared with the case of FIG. Thus, almost satisfactory color reproducibility can be obtained as shown in FIG.

FIG. 5 shows still another embodiment of the present invention. This is achieved by replacing the phase adjusting circuits 30 and 31 shown in FIG. 1 with mixing circuits 30B and 31B as color reproducibility compensating circuits and color difference signals RY and B- connecting the matrix circuit 7 and the encoder circuit 8. These are connected to the Y line, and receive signals from the switching circuit 32 to set the mixing ratio of each of the color difference signals RY and BY. In addition, the same blocks as those shown in FIG. 1 are denoted by the same reference numerals, and overlapping description will be omitted.

In this embodiment, if there is a condition that the AC component is large, it is possible to classify the discharge lamp by the division circuit outputs V _R and V _B , and to mix the color difference signals most suitable for each discharge lamp. A voltage for controlling the ratio is input as a color reproducibility compensation control signal to the mixing circuits 30B and 31B as color reproducibility compensation circuits.

Assume that the outputs of the mixing circuits 30B and 31B are (RY) ', (B
−Y) ′, the expressions (1) and (2) hold, and (RY) ′ = (RY) + k ₁ (BY) (1) (BY) ′ = K ₂ (RY) + (BY) (2) In the case of FIG. 9, k ₁ = 0 and k ₂ = 0, and in the case of FIG. 10, k ₁ = −0.26. , k ₂ = 0.14, satisfactory color reproducibility as shown in FIG. 2 can be obtained.

In the above embodiment, the case of the color video camera using the RY and BY color difference signals has been described. However, the color video camera may be based on the IQ color difference signal or another color difference signal. To play.

Further, by using a circuit having a limit characteristic as shown in FIG. 6 or a circuit having a polygonal line characteristic as shown in FIG. Can be used to output a large signal.

Furthermore, the division circuits 24 and 25, the AC detection circuit 26, the table converter 27, the linear conversion circuits 28 and 29, the switching circuit 32, and the like may be realized by hardware or software, and A similar effect is achieved. In this case, in a case where the conversion is realized by software, the linear conversion circuit may be configured by a table converter. In this case, it is necessary to provide two table converters, a table converter selected when the AC component of the light source is equal to or higher than a specific level, and a table converter selected when the AC component is equal to or lower than the specific level.

The division circuits 24 and 25 only need to have outputs based on the ratio of two input variables, and may be, for example, those obtained by logarithmic conversion.

〔The invention's effect〕

As described above, according to the present invention, the table conversion unit storing the color reproducibility compensation signal value suitable for each of the discharge lamp illumination lights classified based on the output ratio of the division unit, and the output from the photoelectric conversion unit Switching means for outputting an output value from the linear conversion means when it is determined that the AC component of the obtained electric signal is small, and outputting an output value from the table conversion means when it is determined that the AC component is large. Inputting the output signal from the switching means to the color reproducibility compensating means, thereby compensating the saturation and hue of the color signal determined from the first and second color difference signals independently of the white balance adjustment. Therefore, even under a light source having poor color rendering properties such as a discharge lamp, the table conversion means outputs an optimal control signal for color reproducibility compensation according to the light source, thereby achieving color reproducibility. By compensating the saturation and hue of amortization means, there is an effect that can be approximated to the color reproduction closer to the memory color.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a color video camera according to an embodiment of the present invention, FIG. 2 is a vector diagram of color difference signals of the color video camera of FIG. 1, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a vector diagram of a color difference signal of the color video camera shown in FIG. 3, FIG. 5 is a block diagram showing still another embodiment of the present invention, and FIGS. FIG. 8 is an input / output characteristic diagram of a limit circuit and a broken line circuit used in place of the linear conversion circuit in the present invention. FIG. 8 is a block connection diagram showing a conventional color video camera. FIGS. 9 and 10 are diagrams of a conventional color video camera. Vector diagrams showing the phase of each color difference signal under fine weather afternoon and under a discharge lamp. FIGS. 11 and 12 are vector diagrams showing gains under fine weather afternoon and under a discharge lamp according to another conventional color video camera. A. 2 is an image sensor, 21, 22, and 23 are photoelectric conversion elements, 24 and 25 are division circuits, 26 is an AC detection circuit, 27 is a table converter, 30, 31, and
30A, 31A, 30B, 31B are color reproducibility compensation circuits, 30, 31 are phase adjustment circuits, 30A, 31A are gain control circuits, 30B, 31B are mixed circuits, 32
Is a switching circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (4)

(57) [Claims] 1. A photoelectric conversion means for detecting R, G, B components of illumination light and converting them into electric signals, a dividing means for obtaining a ratio of outputs of the photoelectric conversion means, and a signal outputted from the photoelectric conversion means. AC detection means for judging the magnitude of at least one AC component of the electric signal, imaging means for photoelectrically converting an optical image signal incident from a lens, and output signals of the imaging means for R, G, and B. Color separation means for separating the color signals into two color signals, gain control means for adjusting the white balance by controlling the gain of the color signals of the color separation means in accordance with the output ratio of the division means, and white balance adjustment Color difference signal generating means for generating a first color difference signal and a second color difference signal from an output of the gain control means, and compensating the saturation and hue of the color signal determined by the first color difference signal and the second color difference signal. Color reproducibility compensator A stage, a linear conversion means for linearly converting the output value of the division means, and a table conversion storing color reproducibility compensation signal values suitable for each of the discharge lamp illumination lights classified based on the output ratio of the division means. Means, when the AC detection means determines that the AC component of the electric signal output from the photoelectric conversion means is small, outputs the output value from the linear conversion means, and determines that the AC component is large. Is provided with switching means for outputting an output value from the table conversion means, and by inputting an output signal from the switching means to the color reproducibility compensating means, the first color difference signal is output independently of white balance adjustment. And the second
A color video camera for compensating a saturation and a hue of a color signal determined from a color difference signal of the color video signal. 2. The color video according to claim 1, wherein the color reproducibility compensating means adjusts the phases of the first color difference signal and the second color difference signal based on an output signal from the switching means. camera. 3. The color reproducibility compensating means controls individual gains of the first color difference signal and the second color difference signal based on an output signal from the switching means. Color video camera. 4. The apparatus according to claim 1, wherein the color reproducibility compensating means controls a mixing ratio of the first color difference signal and the second color difference signal based on an output signal from the switching means. Color video camera.