JPH0822069B2 - Color display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color display device, and more particularly to a color display device capable of displaying an optimum image corresponding to the hue of an input video signal.

[Conventional technology]

The hue of the transmitted video signal may not be different due to the difference in white balance of the illumination light or the video signal path of the video camera or the like.

When the carrier color signal is band-limited due to the band characteristic of the carrier color signal system before being input to the color demodulation circuit, the phase changes in the frequency band subject to the band limitation and the color demodulation is performed in that state. If you do, an unnatural hue will occur in places where the color changes.

Therefore, in order to reduce these hue changes in the vicinity of the skin color, which is the strongest memory color, some color display devices have conventionally been configured to perform color demodulation at a demodulation angle / demodulation ratio different from the standard. is there.

When the demodulated color signal in the case of standard demodulation in this kind of device is reproduced on the circumference as shown by the broken line in FIG. 8 when considered on the RY / B-Y axis, a certain arbitrary When demodulation is performed by the demodulation axis and the demodulation ratio, color demodulation can be performed on an ellipse as shown by the solid line in the figure.

As a result, the color change of the demodulated signal becomes small with respect to the phase change in the vicinity of the skin color, so that a natural skin color can always be reproduced in various video sources.

Therefore, by performing color demodulation with a given demodulation angle and demodulation ratio, it is possible to obtain color reproduction with little hue change for the stored color.

[Problems to be Solved by the Invention]

However, the hues other than the hue for which the color change is to be reduced are also demodulated so as to be close to the axis for which the color change is to be reduced, so that the hue is different from the original hue of the video signal and the color reproducibility is improved. There was a problem of making it worse.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a color display device capable of always displaying an image of optimum color reproduction corresponding to the hue of a video signal. To provide.

[Means for solving the problem]

The color display device of the present invention includes a color signal demodulation means for demodulating a carrier color signal in an incoming video signal to generate three color difference signals which are color demodulation signals, and two color difference signals of the three color difference signals. Of the hue of the incoming video signal is detected based on a combination of the positive and negative values of the positive and negative, and a hue detection means for outputting a hue detection signal representing the detection result; 3 depending on the detection signal value
A hue correction unit that corrects the amplitudes of the two color difference signals to change the predetermined hue and supplies the three hue-corrected color difference signals to the picture tube is provided, and the predetermined hue of the video signal is changed and displayed. It is the one. Here,
The "predetermined hue" means not only one hue but also "any hue within a certain range".

[Action]

According to the present invention, when the video signal has a predetermined hue,
Since the amplitude of the color demodulation signal is corrected to change the predetermined hue in the color demodulation signal (that is, the predetermined hue of the video signal after color demodulation), the original hue corresponding to the hue of the original video signal is changed. A color reproduction image can be displayed. further,
According to the present invention, the positive / negative of two color difference signals of the three color difference signals is detected, and the predetermined hue is detected by the combination of the positive / negative, so that the predetermined hue can be accurately detected. When the video signal has a predetermined hue, only the predetermined hue can be changed accurately without affecting other hues, and the color reproducibility can be improved.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a color display device according to a first embodiment of the present invention. The device shown in FIG. 1 performs color demodulation at a demodulation angle / demodulation ratio that reduces the hue change of skin color, and in that case, The configuration is such that the green hue whose reproducibility is deteriorated is detected and the color demodulation signal is corrected so as to match the green hue according to the detected signal value.

A color demodulation circuit 1 demodulates a carrier color signal in an incoming video signal. The color demodulation circuit 1 is set to have a small change in hue for skin color and good reproducibility.

Reference numeral 2 denotes a color difference signal adder, and this color difference signal adder 2 has a hue detection signal input terminal, and the color difference from the color demodulation circuit 1 depends on the input signal value to this hue detection signal input terminal. The signal is corrected and supplied to the CRT drive circuit 3.

Reference numeral 4 is a hue detection circuit. The hue detection circuit 4 receives the RY color difference signal and the BY color difference signal from the color demodulation circuit 1 and detects whether the hue of the incoming video signal is green by detecting whether the color difference signals are positive or negative.・ It is to detect whether or not. Here, "RY <0" and "BY"
The area of <0 "is a region where the hue of green is strong, and the hue and amplitude of green are changing. As shown in Fig. 2, the hue detection circuit 5 uses this characteristic to Transistor Q1 detects the time when RY <0 "and" BY <0 ".
~ Q4, resistors R1 ~ R5, and voltage sources V1, V2.

R-from the color demodulation circuit 1 is used as the base of the transistor Q1.
The Y color difference signal is input, the voltage of the voltage source V1 is applied to the emitter via the resistor R1, and the collector is grounded via the resistor R2. The voltage of the voltage source V1 is set to the DC voltage value of the RY color difference signal, and when the RY color difference signal is lower than the DC voltage value and is negative, the transistor Q1 is turned on.

B− from the color demodulation circuit 1 is used as the base of the transistor Q3.
The Y color difference signal is input, the voltage of the voltage source V2 is applied to the emitter via the resistor R3, and the collector is grounded via R4. The voltage of the voltage source V2 is set to the DC voltage value of the BY color difference signal, and when the BY color difference signal is lower than the DC voltage value and is negative, the transistor Q3 is turned on.

The base of transistor Q2 is connected to the connection point between the collector of transistor Q1 and resistor R2, and the emitter is a resistor
The power supply voltage Vcc is applied via R5, and the collector is grounded. Therefore, the transistor Q2 becomes the transistor Q1.
When is turned on, its base becomes "H" and outputs "H" to the emitter.

The base of transistor Q4 is connected to the connection point between the collector of transistor Q3 and resistor R4, and the emitter is a resistor
The power supply voltage Vcc is applied via R5, and the collector is grounded. Therefore, transistor Q4 becomes transistor Q3
When is turned on, its base becomes "H" and outputs "H" to the emitter.

The emitters of the transistors Q2 and Q4 are connected in common.The transistors Q2 and Q4 form an AND circuit in which their bases are input and the emitters are output terminals. Are both "H", that is, only when the RY color difference signal and the BY color difference signal are both in the negative quadrant as shown by the slanted lines in FIG.
The voltage is output to 4).

The output of the detection circuit 4 configured as described above is given to the detection signal input terminal of the color difference signal adder 2 and this color difference signal adder 2 is used for the skin color when the hue of green is not detected. The color signal from the color demodulation circuit 1 is output as it is, and when the hue of green is detected, the color difference signal from the color demodulation circuit 1 is corrected toward green according to the voltage value of the detection signal. It is what is done.

The color difference signal adder 2 includes detection signal amplifiers 21R, 21B,
21G and adders 22R, 22B and 22G. The hue detection signals from the hue detection circuit 6 are detected by these detection signal amplifiers.
Each of 21R, 21B, and 21G is amplified with each gain a, b, and c and its polarity is controlled. The adder 22R adds the color difference signal RY from the color demodulation circuit 1 and the output signal of the detection signal amplifier 21R, and the adder 22B outputs the color difference signal BY from the color demodulation circuit 1 and the output of the detection signal amplifier 21B. The signal is added and the adder 22G adds the color difference signal G-Y from the color demodulation circuit 1 and the output signal of the detection signal amplifier 21G, whereby each color difference signal R-Y, B-Y, The amplitude of G-Y is adjusted. Therefore, the detection signal amplifier 21R and the adder 22R compare the amplitude of the color difference signal RY with the detection signal amplifier 21B and the adder 2R.
2B is for controlling the amplitude of the color difference signal BY, and the detection signal amplifier 21G and the adder 22G are for controlling the amplitude of the color difference signal G-Y.

As shown in FIG. 3, each color difference signal control circuit (a set of a detection signal amplifier and an adder for each color difference signal) has an NP
N-type transistors Q5, Q7, Q8, Q9 and PNP-type transistors Q6, Q1
It consists of 0, Q11, resistors R6, R7, voltage sources V3, V4 and current sources I1, I2. Here, a control circuit including a detection signal amplifier 21R and an adder 22R for the color difference signal RY is shown as a representative. And among its components
The transistors Q7 to Q11 and the voltage sources V3, V4 and R6 form a detection signal amplifier 21R, and the others form an adder 22R.

That is, the hue detection signal is input to the base of the transistor Q7, and the emitter is grounded via the resistor R6. A voltage from a voltage source V3 is applied to the base of the transistor Q8, a voltage from a voltage source V4 is applied to the base of the transistor Q9, the emitters of these transistors Q8 and Q9 are connected in common, and their common connection terminals are connected. To transistor
Q7 collector is connected. Transistors Q10, Q11
Form a current mirror circuit, the bases of which are commonly connected to serve as input terminals, and the emitter is connected to the power supply voltage Vc.
c is applied. The collector of the transistor Q10 is connected to the collector of the transistor Q8, and the collector of the transistor Q11 is connected to the collector of the transistor Q9. Further, the collector of the transistor Q8 is connected to the input terminal of the current mirror circuit.

In this configuration, the hue detection signal input to the base of the transistor Q7 is converted into a current by the transistor Q7 and the transistor R6 and flows into the collector of the transistor Q7. The bases of transistors Q8 and Q9 whose emitters are commonly connected to their collectors are the voltage sources V3 and V4, respectively.
Since it is biased by the voltage source V3, V4,
It divides into the transistor Q8, Q9 with the division ratio by the difference voltage of
The shunted current flows to each collector.

Since the collector of the transistor Q8 is connected to the input terminal of the current mirror circuit, the same current as the collector of the transistor Q8 flows to the collector of the transistor Q11. Therefore, the collector of the transistor Q9 and the transistor
When a current source is placed at the common connection end with the collector of Q11,
A current corresponding to the difference between the currents flowing through the collector of the transistor Q9 and the collector of the transistor Q11 (transistor Q8) appears. Here, the magnitude of the difference is proportional to the difference between the voltage sources V3 and V4 as is clear from the above, and the polarity is such that the relationship between the voltage sources V3 and V4 is “V3> V4”.
In case of, the current flowing in the transistor Q8 exceeds that flowing in the transistor Q9, so that it becomes “positive” and “V3 <
At the time of V4 ", the current flowing through the transistor Q8 becomes lower than that flowing through the transistor Q9, so that the current becomes" negative ", and this current is added in the adder described below, and as a result, the color difference signal R-Y from the color demodulation circuit 1 is obtained. The amplitude of is adjusted.

The color difference signal RY from the color demodulation circuit 1 is input to the base of the transistor Q5, the power supply voltage Vcc is applied to the collector of the transistor Q5, and the emitter is grounded via the current source I1. The connection point between the current source I1 and the current source I1 serves as an output terminal to form an emitter follower circuit. The base of the transistor Q6 is connected to the connection point between the emitter of the transistor Q5 and the current source I1 via the resistor R7, the collector of the transistor Q6 is grounded, and the power supply voltage Vcc is supplied to the emitter of the transistor Q6 via the current source I2. A connection end between the applied voltage and the current source I2 is used as an output terminal, and an emitter follower circuit is also formed here. Collector and transistor of the above transistor Q9
The common connection end of the collector of Q11 is connected to the connection point of the base of the transistor Q6 and the resistor R7.

In this configuration, the color difference signal R-Y input to the base of the transistor Q5 passes through the resistor R7 and the transistor Q6.
Supplied to the base of.

On the other hand, the collector of the transistor Q9 and the transistor
A current corresponding to the difference between the current flowing through the collector of Q11 and the current flowing through the resistor R7 causes the base potential of the transistor Q6 to shift, and here the color difference signal RY from the color demodulation circuit 1 and the amplifier 21R. And the hue detection signal from the. This added signal is output from the common connection end of the transistor Q6 and the current source I2 by the emitter follower, and the CRT
It is supplied to the drive circuit 3.

Amplifier 21B and adder 2 for color difference signal BY
2B, the circuit elements of the amplifier 21G and the adder 22G for the color difference signal G-Y are the same as above, and are set to specific values so that the voltage sources V3 and V4 have respective gains b and a.

As a result, when the hue detecting circuit 4 detects a green hue, the amplitudes of the color difference signals RY, BY, and MY from the color demodulating circuit 1 are corrected according to the detected signal value. Therefore, as shown in FIG. 7, the color difference signal supplied to the CRT drive circuit 3 is one in which the hue of green on the R-r / B-Y axis has changed, and there is little change in hue for skin color and color for green. Good reproduction characteristics can be obtained, and optimum color reproduction can be performed.

FIG. 4 is a block diagram of a color display device according to a second embodiment of the present invention. The apparatus shown in this figure is configured to superimpose R, G, B signals from the outside such as on-screen into video signals and display them on the screen. Since the external signal such as the on-screen does not have the deterioration of the color reproducibility unlike the color demodulation output signal, its hue change is unnecessary. Therefore, the feature of the present embodiment is that the hue correction of the color signals is not performed during the external signal period in which the superimposing is performed. The details will be described below. Since the apparatus of this embodiment has a portion equivalent to or equivalent to that of FIG. 1, the same reference numerals as those in FIG. Only the part will be explained.

In FIG. 4, the apparatus of the present embodiment has a color demodulation output signal /
An external signal switching circuit 5 and a hue detection inhibiting circuit 6 are provided,
Ys is an external signal period display signal given as a control signal to the signal switching circuit 5 and the hue detection prohibiting circuit 6. The external signal period display signal Ys is "H" (high level) during the input period of the external signal and "L" (low level) during the other periods.

The signal switching circuit 5 selectively outputs the color demodulation output signal and the external signal in accordance with the period display signal Ys, and outputs the color demodulation output signal while the period display signal Ys is “L” and the period display signal Ys. An external signal is output during the "H" period.

The hue detection prohibiting circuit 6 controls the supply of the hue detection signal to the adder 2 according to the period display signal Ys. The period display signal Ys outputs the hue detection signal during the period “L”. The hue detection signal is not supplied to the adder 2 while the period display signal Ys is "H".

FIG. 5 shows the detailed configuration of the hue detection prohibiting circuit 6 in association with the circuit elements of the hue detecting circuit 4.

In this figure, the hue detection prohibition circuit 6 includes an NPN type transistor Q12, a PNP type transistor Q13 and resistors R8, R9, R10.
It consists of The period display signal Ys is input to the base of the transistor Q12 via the resistor R8 in series, and
R9 grounds the connection point between the base of the transistor Q12 and the resistor R8, and the period display signal Ys is divided by these resistors R8 and R9. The emitter of the transistor Q12 is grounded and turns on when the period display signal Ys is "H".

The base of the transistor Q13 is connected to the collector of the transistor Q12, and the power supply voltage Vcc is applied to the connection point thereof via the pull-up resistor R10. Transistor Q13
Is grounded, and the emitter is connected to the collectors of the transistors Q2 and Q4 that form the output end of the detection circuit 4. When the period display signal Ys is "H", the detection circuit 4 is
Detection signal is dropped to the ground and the detection signal is added
It will not be supplied to.

As a result, the hue correction of the color signal can be prevented from being performed during the external signal period in which the superimposing is performed.

Further, it goes without saying that the second embodiment can also obtain the same effects as the first embodiment.

In the above embodiment, the RY color difference signal and the BY color difference signal are used to detect the green hue on the RY / BY axis, and the green hue is configured to correspond to the green hue. However, the present invention is not limited to this, and may be configured to correspond to other hues.

In this case, according to the characteristics of the hue to be detected, the information source for the detection is set to another element on the RY / B-Y axis,
RY / G-Y axis other than RY / BY axis or BY / G-Y
An appropriate one should be selected from each element on the axis. At this time, if the information is insufficient for one hue element alone depending on the hue, information may be obtained for a plurality of hue elements and necessary logical operations may be performed.

〔The invention's effect〕

As described above, according to the present invention, when the video signal has a predetermined hue, the predetermined hue in the color demodulation signal is changed, so that the original color reproduction corresponding to the hue of the original video signal is reproduced. Images can be displayed. Further, according to the present invention, the positive / negative of two color difference signals among the three color difference signals is detected, and the predetermined hue is detected by the combination of the positive / negative, so that the predetermined hue can be accurately detected. When the video signal has a predetermined hue,
Only the predetermined hue can be changed accurately without affecting the other hues, and the color reproducibility can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a color display device according to a first embodiment of the present invention, FIG. 2 is a detailed diagram of a hue detection circuit thereof, and FIG. FIG. 4 is a block diagram of a color display device according to a second embodiment of the present invention, FIG. 5 is a detailed view of a hue detection inhibiting circuit thereof, and FIG. 6 is a hue provided in the first and second embodiments. FIG. 7 is a hue detection characteristic diagram of the detection circuit, and FIG. 7 is a final (that is, after hue correction) color difference output characteristic diagram of the embodiment.
The figure is a color difference output characteristic diagram in which the hue change of the skin color is reduced. 1 ... Color demodulation circuit, 2 ... Detection signal adder, 3 ... CRT drive circuit, 4 ... Hue detection circuit.

Claims (1)

[Claims] 1. A color signal demodulation means for demodulating a carrier color signal in an incoming video signal to generate three color difference signals which are color demodulation signals, and positive and negative of two color difference signals of the three color difference signals. And a hue detection unit that detects whether or not the hue of the incoming video signal is a predetermined hue by a combination of positive and negative, and outputs a hue detection signal indicating the detection result, and the hue detection signal. And a hue correction unit that corrects the amplitudes of the three color difference signals in accordance with the values to change the predetermined hue and supplies the three hue-corrected color difference signals to a picture tube.