JPH0564515B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a hue variable circuit for changing the phase of a video signal in a demodulation circuit for color television signals according to the PAL system and the NTSC system.

[Technical Background of the Invention] Currently, various color television systems are being adopted in countries around the world, and these are mainly
It is broadly divided into NTSC, PAL, and SECAM systems, and it is well known that these systems are not compatible with each other. On the other hand, there is a strong demand for higher image quality in each country, and there is a need to make the hue adjustment adopted in the NTSC system possible for PAL system receivers as well. Particularly in a dual-purpose receiver capable of receiving images of both the NTSC and PAL systems, it is preferable to be able to adjust the hue of both systems.

First, as a conventional example, a block diagram of a system shown in FIG. 2 in which only the NTSC system is capable of changing the hue, and the PAL system does not have a hue variable adjustment function will be described.

In the block diagram shown in Figure 2, switch 1
If it is connected to the terminal a side of each of 3 and 14, it means that the input video signal is PAL system,
If it is connected to the terminal b side, it indicates that an NTSC video signal is being added.

First, means for reproducing PAL video signals (particularly in this case, it shows demodulating means for PAL-D)
I will explain about it. Switches 13 and 14 are each set to the terminal a side. When a PAL video signal is applied to the input terminal, the Y/C separation circuit 6 separates it into a luminance signal and a carrier color signal. The carrier color signal is supplied to summation circuits 2 and 3, a 1H delay line 1 that delays by one horizontal scanning period, and a burst gate circuit 7 that detects only burst signals. The carrier color signal that has passed through the 1H delay line 1 is applied to the sum calculation circuit 3 together with the carrier color signal that has not been delayed by 1H via the switch 14 to obtain a (B-Y) carrier color difference signal. Further, the phase of the carrier color signal that has passed through the 1H delay line 1 and the switch 14 is inverted by the phase inversion circuit 16, and is applied to the summation circuit 2 together with the carrier color signal that has not been delayed by 1H. )
Obtain a carrier color difference signal. The burst gate circuit 7 extracts the burst signal component of the carrier color signal.
The burst signal output is performed by the subcarrier oscillation circuit 8 controlled by the next stage APC circuit and every horizontal scan.
The signal is supplied to a line identification circuit 11 that discriminates between burst signals having a phase difference of 180 degrees.

The subcarrier signal output of the subcarrier oscillation circuit 8 passes through a switch 13 and generates a 90° phase difference.
The above (B-
Y) added together with the carrier color difference signal to obtain a BY color difference signal. Further, the subcarrier signal output is directly connected to the terminal b side of the switch 12, and the output of a 180° phase shifter 9, which has a phase difference of 180°, is connected to the terminal a side of the subcarrier signal output. The switch 12 is switched every 1H based on the output of the line identification circuit 11. The subcarrier signal passed through the switch 12 is applied to the R-Y color demodulator 4 together with the (R-Y) carrier color difference signal to obtain the R-Y color difference signal.

Next, a means for reproducing an NTSC video signal will be explained. Switches 13 and 14 are each connected to terminal b.
set on the side. When an NTSC video signal is applied to the input terminal, the carrier color signal is sorted by the Y/C separation circuit 6, passes through the summation circuits 2 and 3, and is applied to the color demodulation circuits 4 and 5, respectively, to generate the R-Y color difference. signal,
Obtain a B-Y color difference signal. The burst signal of the carrier color signal output from the Y/C separation circuit 6 is extracted by a burst gate circuit 7 and controls the subcarrier oscillation circuit 8 described above. The output of the subcarrier oscillation circuit 8 passes through a phase shifter 15 that generates a phase difference of Φ as a function means for adjusting the hue, and then passes through a 90° phase shifter 10.
It is added to the Y color demodulator 5. Further, the subcarrier oscillation signal passes through the phase shifter 15, and the switch 12 is set to the terminal b side (in the case of the NTSC system, the line identification circuit 11 does not function).
is applied to the R-Y demodulator 4, and the R-Y
A color difference signal will be obtained.

Therefore, as mentioned above, by the configuration shown in FIG.
Color demodulation is possible for both PAL and NTSC systems.

[Problems in the background art] As mentioned above, since the color demodulation means is configured to reproduce both systems, it is not possible to achieve high image quality or adjust the hue to your preference in the case of the PAL system, and In this case, a phase shifter 15 is required at the output of the subcarrier oscillation circuit 8, and therefore, the subcarrier signal is easily affected by temperature and humidity, which can cause instability. Both the PAL system and the NTSC system have the disadvantage that they tend to deviate from the normal demodulation phase.

[Object of the invention] The present invention has been made to eliminate the problems and drawbacks of the conventional ones as described above, and is
A ±phase shifter with the same absolute value is provided in the front stage of the PAL color reproduction means, and the hue can be made variable not only in the NTSC system but also in the PAL system by a switching operation by the line identification means, and the hue can be variably shifted in the rear stage of the subcarrier oscillation circuit. Since no phase shifter is provided, a stable subcarrier signal can be obtained, and the object of the present invention is to provide a hue variable means that can stably maintain a once set hue.

[Summary of the Invention] In the color demodulation means for NTSC and PAL color television signals, the carrier color signal is passed through a variable ±phase shifter with the same absolute value, and the color demodulation means for each system is processed at the subsequent stage. NTSC and PAL
Both methods achieved stable playback operation and hue variable function.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, in which parts equivalent to those in FIG. 2 are designated by the same reference numerals. When the carrier video signal is input to the input terminal, the carrier color signal is extracted by the Y/C separation circuit 6,
Phase shifters 17 and 18 and a burst gate circuit 7 that generate a phase difference ±Φ that is variable and opposite in phase to each other.
is input.

First, in the case of PAL system, switch 14 is connected to terminal a.
set on the side. The switches 12 and 19 are switched by the line identification circuit 11 for each horizontal scan, and in the example shown in the figure, they operate in conjunction. FIG. 3 shows a vector diagram for the basic burst signal in the n-th and (n+1)-th horizontal scanning lines.
First, assuming that a carrier color signal having a phase angle of θ with respect to the B-Y component axis is input, the carrier color signal on the n-th horizontal scanning line will be as shown in figure a, with a phase shift of +Φ. The output from the phase shifter 17 becomes a carrier color signal having a phase angle of θ+Φ as shown in figure c, and the output of the -Φ phase shifter 18 becomes a carrier color signal having a phase angle of θ−Φ as shown in figure e. becomes. Next, the conveyed color signal on the n+1 horizontal scanning line becomes as shown in figure b, the output of +Φ phase shifter 17 has a phase angle of -θ+Φ as shown in figure d, and -Φ phase shifter 18 The output has a phase angle of -θ-Φ as shown in the f diagram. Here, when the n-th horizontal scanning line is input by the switch 19, it is connected to the terminal a side which selects the carrier color signal having the phase angle shown in figure c, and when the n+1-th horizontal scanning line is input, figure f It is connected to the terminal b side which selects the carrier color signal having the phase angle shown in FIG. In other words, switch 1
The output of 9 is the output of +Φ phase shifter 17 in the n-th horizontal scanning period, and - in the n+1-th horizontal scanning period.
Select the output of the Φ phase shifter 18 and select the output of the Φ phase shifter 18,
Output a carrier color signal having the vector shown in the figure. Therefore, the phase angle of the carrier color signal output from the switch 19 becomes θ+Φ in the n-th horizontal scanning period, and becomes n+1.
In the main horizontal scanning period, it becomes -(θ+Φ). This indicates that the phase of the carrier color signal of the PAL system has become a carrier color signal rotated by the vector Φ with respect to the vector of the input carrier color signal of θ.

The output of this switch 19 is shown in the conventional example mentioned above.
This is reproduced by the PAL demodulation means, and the B-Y color difference signal and the R-Y color difference signal are output as color difference signals rotated by a phase of +Φ with respect to the input carrier color signal. In addition, the burst gate circuit 7, the subcarrier oscillator 8, the lie identification circuit 11, and the PAL
The structure of the matrix etc. is PAL as shown in the conventional example above.
The contents are the same as those explained in the demodulation means of the system. Although one embodiment has been described above based on FIG. In other words, it has the function of changing the hue.

In addition, in FIG. 1, the switch 19 is the ±Φ phase shifter 1.
7, 18, the ±Φ phase shifter 17,
It may be provided in the front stage of 18, or it may be provided in both the front stage and the rear stage.

Further, in FIG. 1, the case where the switch 19 operates in conjunction with the PAL-SW switch 12 has been explained, but even if the switch 19 operates in the opposite phase, the output of the switch 19 will still contain a carrier color signal having a similar reversed rotational phase angle. You can get . Further, although the PAL-D method has been described as a means for demodulating the carrier color signal output from the switch 19, another method may be used.

Next, the reproduction means in the NTSC system will be explained. In this method, the switch 12 is placed on the terminal b side,
The switch 19 is connected and set to the terminal a side, and the switch 14 is connected to the terminal b side. Also, line identification circuit 1
Function 1 is removed. This setting can be done automatically or manually. Therefore, the carrier color signal output from the Y/C separation circuit 6 becomes a carrier color signal whose phase is advanced by +Φ with respect to the carrier color signal transmitted by the +Φ phase shifter 17. In other words, the hue changes by the phase difference between the burst system and its advanced +Φ. The output of this +Φ phase shifter 17 is passed through the switch 19, as shown in the conventional example above.
The NTSC color reproduction means outputs the B-Y color difference signal and the R-Y color difference signal. Furthermore, since the phase shifter 15 and switch 13 shown in the above-mentioned conventional example are not required, the subcarrier oscillation circuit 8 can operate more stably than the conventional example, and the hue may fluctuate depending on external conditions such as temperature and humidity. There will be fewer things. If you want to obtain a -Φ hue using this method, set the terminal of the switch 19 to the b side and use the -Φ phase shifter 18 or vary the phase shift amount of the +Φ phase shifter 17. A desired hue can be obtained by providing the function of shifting the phase by Φ and setting it on the terminal a side of the switch 19.

[Effects of the Invention] As described above, according to the present invention, in the case of the PAL color demodulation means, each of the reverse phase By changing the amount of phase shift of the phase shifter, it is possible to change the hue and adjust the hue to the user's preference. This also means correcting variations in the processing means leading to the output of each color of R, G, and B, which tend to occur after the main color demodulation means, and correcting color variations on the sender side, such as broadcasting stations and program production. You will be able to do that.

In addition, in the present invention, there is no need to provide a phase shifter and a PAL/NPTSC mode changeover switch in the next stage of the subcarrier oscillation circuit as in the conventional example, so both systems can obtain stable subcarriers for demodulation, and once set Hue is no longer influenced by external circumstances.

Furthermore, in the present invention, since the hue can be changed by the same adjustment section for both the PAL system and the NTSC system, improvements such as simplification, cost reduction, and stability in terms of space and circuit components can be expected compared to when they are provided separately. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a block diagram of a conventional example, and FIG. 3 is a color signal vector diagram for explaining FIG. 1. 1...1H delay line, 2, 3...sum calculation circuit, 4
...RY color demodulation circuit, 5...B-Y color demodulation circuit, 7... Burst gate circuit, 17...+Φ phase shifter, 18...-Φ phase shifter.

Claims (1)

[Scope of Claims] 1. A color demodulating means for PAL and NTSC color television signals, comprising: (a) first and second phase shifting means for shifting the carrier color signal by the same absolute value and in opposite phases; (b) switching means for switching the input or output of the first and second phase shifting means for each horizontal scanning line; (c) in the case of the PAL system, operating the switching means to switch the input or output of the first and second phase shifting means for each horizontal scanning line; connected to the latter part of the means
(d) in the case of the NTSC system, setting means for fixing the switching means so that only one of the first and second phase shifting means passes the signal, and the PAL system; A PAL/NTSC video circuit comprising: a setting means for not connecting a delay line for one horizontal scanning period in a demodulating means; and a means for fixing a pulse switch.