JP3296745B2 - Color signal generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal generation circuit for an on-screen display used in a home VTR or the like, and more particularly to a color signal generation circuit for coloring an internally created screen.

[0002]

2. Description of the Related Art As a color signal generating circuit used for an internally created screen, a circuit as shown in FIG. 2 is known. In FIG. 2, reference numeral 4 denotes a 45-degree phase color signal generation circuit for eight colors. Reference numeral 1 denotes four times the subcarrier 4fsc (fsc is 3.58 MHz in the case of NTSC) corresponding to four times the frequency of the color burst signal. A frequency divider for frequency division, 2 is a shift circuit, and a frequency divider (1) is provided with flip-flops 1a and 1b and has four times the number of subcarriers 4.
Divide fsc. The shift circuit (2) shifts the phase of the output signal of the frequency divider (1) by a clock supplied through the inverter (3).

Various phase signals are generated by the operation of the frequency divider (1) and the shift circuit (2). That is, Phi 0 to Phi 7 shown in FIG. These eight signals are applied to the delay circuits (11) to (16). Each delay circuit performs a necessary delay so as to obtain a desired color and adjusts a phase. FIG. 3B shows the signal waveform after the delay.

As described above, according to the circuit of FIG. 2, a color signal having a phase angle of every 45 degrees obtained by dividing a signal of 4 fsc is created, and the color signal is delayed so as to have a desired color. So that a color signal can be created.

[0005]

However, the color signal generation circuit shown in FIG. 2 has a problem that a dedicated delay circuit is required for each color. Delay circuits often require capacitors and the like, and are unsuitable for IC integration.
It also increases costs. Further, in the color signal generation circuit of FIG. 2, the four times subcarrier 4fsc was indispensable. Therefore, there is a problem that it cannot be created when there are only twice as many subcarriers 2fsc.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned point, and divides a frequency of a reference signal having a frequency twice as high as that of a color burst signal to form a plurality of color signals different in phase by 90 degrees. A frequency divider that generates the signal; a first delay circuit that delays the phase of the reference signal; and a second signal that synchronizes a first output signal of the frequency divider with the delay signal of the first delay circuit and outputs a burst signal. A single cutout circuit, and a plurality of color signals are obtained from the frequency divider.

[0007]

FIG. 1 shows a color signal generation circuit according to the present invention. FIG. 1A shows a frequency division of a subcarrier 2fsc having a frequency twice as high as that of a color burst signal. A frequency divider for generating a plurality of (four Q1 to Q4) signals, (2) a first delay circuit for delaying the phase of the 2fsc signal by 14 degrees, and (3) a phase delay of the 2fsc signal by 2
A second delay circuit that delays 7 degrees, (10) a third delay circuit that delays the phase of the 2fsc signal by 43 degrees, and (4) outputs a frequency-divided output signal Q1 of the frequency divider (1) to the first signal. A first cutout circuit which synchronizes with the delay signal of the delay circuit (2) and outputs the burst signal as a burst signal; (5) converts the frequency-divided output signal Q1 of the frequency divider (1) to that of the second delay circuit (3) A second color signal (yellow) output in synchronization with the delay signal
A cutout circuit, (6) a third cutout circuit for synchronizing the frequency-divided output signal Q3 of the frequency divider (1) with the delay signal of the second delay circuit (3) and outputting the same as a color signal (blue); (7) a fourth cutout circuit for synchronizing the frequency-divided output signal Q4 of the frequency divider (1) with the delay signal of the third delay circuit (10) and outputting it as a color signal (magenta);
(8) is a fifth cutout circuit for synchronizing the frequency-divided output signal Q2 of the frequency divider (1) with the delay signal of the third delay circuit (10) and outputting it as a color signal (green).

The frequency divider (1) is constituted by a circuit similar to that of FIG. The cutout circuit is composed of a D-type flip-flop, and the output signal of the frequency divider (1) is D-type.
The output signal of the delay circuit is applied to the clock terminal. FIG. 4 shows the phase relationship between the color signals. In FIG. 4, the burst signal exists at a position of 180 degrees on the BY axis. In FIG. 4, 0, 90, 180, and 2
70 degrees can be created by the frequency divider (1) in FIG.

A signal of 2 fsc is applied to the terminal (11) in FIG. The 2fsc signal is delayed by 14 degrees in the first delay circuit (2) and applied as a clock signal to a first cutout circuit (4) for generating a burst signal. From the frequency divider (1), Q1 to Q4 having phases different by 90 degrees are generated. This is shown in FIG. Divided output signal Q1
Are set on the 180-degree axis, Q2 is set on the 270-degree axis, Q3 is set on the 0-degree axis, and Q4 is set on the 90-degree axis. The six colors can be created based on the four frequency-divided output signals shown in FIG. It has been found that six colors can be produced by the phase synthesis shown in Table 1 below.

Table 1 Red: 104 degrees = 90 degrees + 14 degrees (prepared from Q4 in FIG. 5) Cyan: 284 degrees = 270 degrees + 14 degrees (prepared from Q2 in FIG. 5) Yellow: 167 degrees = 180 degrees-13 degrees (created from Q1 in FIG. 5) Blue: 347 degrees = 360 degrees-13 degrees (created from Q3 in FIG. 5) Magenta: 61 degrees = 90 degrees-29 Degree (created from Q4 in FIG. 5) Green: 241 degrees = 270 degrees−29 degrees (created from Q2 in FIG. 5) What is clear from Table 1 is that +14 degrees, −13 degrees, and −2 degrees.
If three types of phase shifts of 9 degrees are performed, six colors can be displayed. Therefore, in the present invention, the phase advance of 14 degrees is performed by the first delay circuit (2) in FIG. As a result, the phase of the burst signal serving as the color reference moves, and the same result as that obtained by adjusting the output signal phase of the frequency divider (1) is obtained. Specifically, as shown in FIG. 1, cyan Q2 and red Q
4 can be created directly from the divided output signals Q2, Q4 of the divider (1).

FIG. 6 shows this state. 2fsc in FIG.
The signal of 2fsc from the terminal (11) is shown, and when the signal of 2fsc is divided by 1/2, Q1 to Q4 of the frequency fsc are obtained. The signal Q1 is applied as a data signal to the first cutout circuit (4). The signal delayed by 14 degrees is shown in FIG.
Shown as 4th DELAY. For this reason, the burst signal shown by Q1a in FIG. 6 is obtained from the first cutout circuit (4). Thereby, cyan Q2 and red Q4 can be obtained as they are as the frequency-divided output signals.

Next, yellow and blue will be described. Since the first delay circuit (2) moves the reference phase, -1
To create 3 degrees and -29 degrees -27 degrees (-13 =-
27 degrees +14 degrees) and -43 degrees (-29 degrees = -43 degrees +1)
4) is prepared. Therefore, yellow and blue are shown in Figure 1.
-13 degrees is obtained by the second delay circuit (3).

FIG. 1 shows magenta and green.
-29 degrees is obtained by the third delay circuit (10). This is shown in FIG. The delayed output signals of the second and third delay circuits (3) and (10) are shown in FIG.
Shown as LAY, 43 degrees DELAY. 27 degree DELA
By Y, Q1b yellow and Q3a blue are cut out. Similarly, magenta Q4a and green Q2a are cut out by 43 degrees DELAY.

Therefore, according to the circuit of FIG. 1, six colors can be accurately displayed only by using three delay circuits using a clock signal of 2 fsc.

[0015]

As described above, according to the present invention, it is possible to provide a color signal generation circuit capable of displaying six colors by using only three delay circuits and using the remaining logic circuits. For this reason, the number of delay circuits can be significantly reduced. In particular, according to the present invention, there is an advantage that six colors can be accurately displayed using a clock signal of 2 fsc.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a color signal generation circuit according to the present invention.

FIG. 2 is a circuit diagram showing a conventional color signal generation circuit.

FIG. 3 is a waveform diagram for explaining FIG. 2;

FIG. 4 is a phase vector diagram for explaining FIG. 1;

FIG. 5 is a phase vector diagram for explaining FIG. 1;

FIG. 6 is a waveform chart for explaining FIG. 1;

[Explanation of symbols]

 (1) Divider (2) First delay circuit (3) Second delay circuit (10) Third delay circuit (4) First cutout circuit (5) Second cutout circuit (6) Third cutout circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/00-9/78

Claims (5)

(57) [Claims] 1. A frequency divider for dividing a reference signal having a frequency twice as high as that of a color burst signal to generate a plurality of signals having phases different by 90 degrees, and a first delay circuit for delaying the phase of the reference signal And a first cutout circuit that synchronizes a first output signal of the frequency divider with a delay signal of the first delay circuit and outputs the signal as a burst signal, and obtains a plurality of color signals from the frequency divider. A color signal generation circuit characterized in that: 2. The color signal generation circuit according to claim 1, wherein said frequency divider generates a color signal including at least one of green, cyan, magenta, and red. 3. The color signal generation circuit according to claim 1, wherein a delay amount of said first delay circuit is around 14 degrees. 4. A frequency divider for dividing a reference signal having a frequency twice as high as that of a color burst signal to generate a plurality of signals having phases different by 90 degrees, and a first delay circuit for delaying the phase of the reference signal. A second delay circuit that delays the phase of the reference signal; a first cutout circuit that synchronizes a first output signal of the frequency divider with a delay signal of the first delay circuit and outputs the signal as a burst signal; A second cutout circuit that synchronizes a second output signal of the frequency divider with a delay signal of the second delay circuit and outputs the color signal as a color signal, wherein a plurality of second cutout circuits are provided by the frequency divider and the second cutout circuit. A color signal generating circuit for obtaining a color signal. 5. A frequency divider for dividing a reference signal having a frequency twice as high as that of a color burst signal to generate a plurality of signals having phases different by 90 degrees, and a first delay circuit for delaying the phase of the reference signal. A second delay circuit for delaying the phase of the reference signal; a third delay circuit for delaying the phase of the reference signal; and synchronizing a first output signal of the frequency divider with a delay signal of the first delay circuit. A first cutout circuit for converting the second output signal of the frequency divider into a color signal by synchronizing the second output signal of the frequency divider with a delay signal of the second delay circuit; A third cutout circuit for synchronizing a third output signal of the frequency divider with the delay signal of the third delay circuit and outputting the color signal as a color signal, wherein a plurality of the frequency dividers and the second and third cutout circuits are provided. Color signal. A color signal generation circuit.