JPS6232878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A beam-indexed color television receiver has a single electron beam as a picture tube, with red, green and blue color phosphor stripes arranged horizontally. An index that has a fluorescent surface and index phosphor stripes arranged horizontally on the inner surface of the phosphor surface is used, and is obtained by scanning the index phosphor stripes with an electron beam. Color switching is performed based on the signal, and when the electron beam scans the red color phosphor stripe, the red primary color signal is used.
When scanning a green phosphor stripe, a green primary color signal is used, and when a blue phosphor stripe is scanned, a blue primary color signal is used for density modulation.

Here, the frequency of the index signal is inversely proportional to the pitch of the index phosphor stripe and proportional to the scanning speed of the electron beam, so if the linearity of the horizontal deflection is poor or the scanning speed changes,
The frequency of the index signal fluctuates.

However, the processing loop from index signal detection to color switching requires the response time of the photodetector, the group delay time of the filter that extracts the index signal from the output signal of the photodetector, and the PLL that frequency-multiplies this index signal. It has a certain delay time due to group delay time, etc. For this reason,
When the frequency of the index signal fluctuates as described above, the timing of color switching shifts, resulting in color shift.

By the way, Japanese Patent Application No. 120697 (1972)
No. 45928) proposes a method for correcting the timing deviation of color switching based on the delay time of this loop.

That is, in the conventional general method, as shown in FIG. 1, the output signal of the photodetector 20 provided in the funnel portion of the picture tube 10 is supplied to a bandpass filter 30 and an index signal is extracted. This is supplied to the PLL 40 and frequency-multiplied, and the output signal of the PLL 40 is supplied to the gate signal generator 50 consisting of a ring counter, which generates the primary color signals of red, green, and blue under the conditions regulated by the mode set pulse P _S. Three-phase gate signals S _R , S _G and S _B to be gated sequentially are obtained. Although not shown, the red, green, and blue primary color signals are sequentially gated using the gate signals _SR , _SG , and _SB , and the switched primary color signals are applied to, for example, the first grid 11 of the picture tube 10. It will be done.

In the PLL 40, the index signal from the bandpass filter 30 is supplied to a phase comparator 41,
The output signal of the voltage controlled oscillator 42 is supplied to a frequency divider 43 , the frequency-divided signal is supplied to a phase comparator 41 , and the output voltage of the phase comparator 41 is supplied to the oscillator 42 through a low-pass filter 44 .

and 3 for 2 sets of colored phosphor stripes.
The index phosphor stripes are formed at the rate of a book, so that the frequency of the index signal is f _I , and the so-called triplet frequency determined by the pitch of a pair of color phosphor stripes and the scanning speed of the electron beam is f _T . In the case of the type where f _I =3/2f _T , the frequency divider 43 is set as a 1/2 frequency divider,
The frequency of the output signal of the PLL 40 becomes 2f _I =3f _T.
In addition, in a type in which index phosphor stripes are formed at a ratio of 3 to 4 sets of color phosphor stripes, so that f _I =3/4 f _T , the frequency divider 43 is set to 1/4. As a frequency divider, the frequency of the output signal of the PLL 40 becomes 4f _I =3f _T.

In contrast, Japanese Patent Application No. 51-120697 (Japanese Unexamined Patent Publication No. 53
-45928) method, as shown in Figure 2,
The output signal of the PLL 40 is supplied to the mixer 60, the signal obtained from the frequency divider 43 of the PLL 40 is supplied to the mixer 60 through the delay circuit 70, and the output signal of the mixer 60 is supplied to the bandpass filter 80. , from this, a signal with a frequency that is the difference between the frequency of the output signal of the PLL 40 and the frequency of the output signal of the delay circuit 70 is extracted, and this is output to the gate signal generator 50.
supplied to

In the type of f _I =3/2f _T , the frequency divider 43 is made into a 1/3 frequency divider, and the frequency of the output signal of the PLL 40 becomes 3f _I =9/2f _T , and the delay circuit 70 Since the frequency of the output signal f _I =3/2f _T , the frequency of the output signal of the bandpass filter 80 is 2f _I = 3f _T
become. In addition, in the type of f _I = 3/4f _T , the frequency divider 43 is set as a 1/5 frequency divider, the frequency of the output signal of the PLL 40 becomes 5f _I = 15/4f _T , and the delay circuit 7 Since the frequency of the output signal of 0 is f _I =3/4f _T , the frequency of the output signal of the bandpass filter 80 is 4f _I
= 3f _T.

Therefore, the delay time of the photodetector 20 and the bandpass filter 30 is τ ₁ , the delay time between input and output of the PLL 40 is τ ₂ , and the delay time of the delay circuit 70 is τ
_d , the delay time of the mixer 60 and the bandpass filter 80 is _τ3 , the delay time of the frequency divider 43 is assumed to be 0, and the amount of variation in the angular frequency of the index signal is Δω, then f _I =2/3f _T In the type, the phase error Δφ ₁ of the output signal of the PLL 40 is expressed as Δφ ₁ = (τ ₁ + τ ₂ )・3Δω (1), and the phase error Δφ ₂ of the output signal of the delay circuit 70 is Δφ ₂ = (τ ₁ + τ ₂ + τ _d ) Δω (2) Therefore, the bandpass filter 80
_{The phase} error _{Δφ 3 of the output signal of}
τ ₃ }Δω = {2(τ ₁ +τ ₂ +τ ₃ )−τ _d }Δω
......(3) becomes. Therefore, if τ _d = 2 (τ ₁ + τ ₂ + τ ₃ ) (4), the phase error Δφ ₃ of the signal supplied to the gate signal generator 50 becomes 0, and the index signal Even if the frequency changes, the timing of color switching does not shift, and no color shift occurs.

In addition, in the type of f _I = 3/4f _T , the phase error Δφ ₁ of the output signal of PLL40 is expressed as Δφ ₁ = (τ ₁ + τ ₂ )・5Δω (5), and the delay circuit The phase error Δφ ₂ of the output signal of the bandpass filter 80 is expressed as Δφ ₂ = (τ ₁ +τ ₂ +τ _d )Δω (6), and therefore the bandpass filter 80
_{The phase error Δφ 3 of the output signal of}
τ ₃ }Δω = {4(τ ₁ +τ ₂ +τ ₃ )−τ _d }Δω
......(7) It becomes. Therefore, if τ _d = 4 (τ ₁ + τ ₂ + τ ₃ ) (8), the phase error Δφ ₃ of the signal supplied to the gate signal generator 50 becomes 0, and the index signal Even if the frequency of the color changes, the timing of color switching does not shift and color shift does not occur.

Specifically, for f _I =3/2f _T type f _T =8 MHz, f _I 12 MHz, τ ₁ = 0.16 μsec, τ ₂ = 0.01 μsec, τ ₃ = 0.08.
If μsec ......(9), then τ _d = 2 (τ ₁ + τ ₂ + τ ₃ ) = 0.5 μsec ...(10). Also, for the type of f _I =3/4f _T , f _T = 8 MHz, f _I = 6 MHz, τ ₁ = 0.32 μsec, τ ₂ = 0.01 μsec, τ ₃ = 0.08
μsec ………(11) If τ _d = 4 (τ ₁ + τ ₂ + τ ₃ ) = 1.64 μsec
……(12) should be selected.

By the way, as shown in FIG. 4A, the picture tube 10 has an effective screen area 12 on which color phosphor stripes and index phosphor stripes are formed, and a scanning start area 13 on the left side where only index phosphor stripes are formed. is provided, and the electron beam reaches this scanning starting part 1.
3 is scanned with a constant beam amount, and in this scanning start section 13, phase matching of the gate signals S _R , S _G and S _B from the gate signal generator 50 with respect to the color phosphor stripes is performed, so-called mode setting. I have to. Therefore, the width of the scan start section 13 is such that the signal supplied to the gate signal generator 50 already has a predetermined frequency of 3f _T within the period during which the electron beam scans the scan start section 13. It is necessary to

In the conventional general method shown in FIG. 1, the index phosphor stripe is removed from the bandpass filter 30 after a time τ ₁ after the electron beam impacts the first index phosphor stripe in the scan start section 13 during the horizontal scan period. A signal is obtained, and after the lock time of the PLL 40 has elapsed, a predetermined signal is sent to the gate signal generator 50.
A signal with a frequency of 3f _T is supplied. However, the second
In the method shown in the figure, after the PLL 40 is locked, the predetermined signal is not output from the band-pass filter 80 until the sum of the delay time τ _d of the delay circuit 70 and the delay time τ ₃ of the mixer 60 and the band-pass filter 80 has elapsed.
A signal with a frequency of 3f _T is not obtained, that is, a signal with a frequency of 3f _T is not supplied to the gate signal generator 50. Therefore, in the method shown in FIG. 2, the width of the scanning start portion 13 must be increased by the sum of the times τ=τ _d +τ ₃ .

The time τ for this sum is τ = τ _d + τ ₃ = 0.58μsec (13) in the concrete example of the type _{f I =} 3/2f _T mentioned above, _and In the example, τ = τ _d + τ ₃ = 1.72 μsec (14), which is 4.4 mm for an 18-inch receiver, and 4.4 mm for an 18-inch receiver, respectively.
Equivalent to a width of 13.1mm.

In this way, the method shown in FIG. 2 can correct the deviation in color switching timing due to the loop delay time, but it requires that the width of the scan start section 13 for mode setting be made considerably wide. , the width of the effective screen portion 12 becomes narrower. As shown in FIG. 4A, the left and right overscan sections 15 and 16 are usually symmetrical, so by increasing the width of the scan start section 13, the effective screen section 12 is moved considerably to the right. The screen becomes undesirable.

This invention is intended to eliminate such inconveniences.

FIG. 3 shows an example of the present invention, in which the frequency divider 43 of the PLL 40 is a 1/3 frequency divider in both the f _I = 3/2 f _T type and the f _I = 3/4 f _T type. It is said that The output signal of the PLL 40 is supplied to the mixer 60, the signal obtained from the frequency divider 43 of the PLL 40 is supplied to the mixer 60 through the delay circuit 70, and the output signal of the mixer 60 is supplied to the bandpass filter 80. From this, a signal having a frequency that is the sum of the frequency of the output signal of the PLL 40 and the frequency of the output signal of the delay circuit 70 is extracted. Then, the output signal of this bandpass filter 80 is extracted through another PLL 90 as necessary. That is, the output signal of the band pass filter 80 is supplied to the phase comparator 91, the output signal of the voltage controlled oscillator 92 is supplied as is to the phase comparator 91, and the output voltage of the phase comparator 91 is supplied to the oscillator 92 through the low pass filter 94. Supplied. In the type of f _I =3/2 f _T , the output signal of the PLL 90 is supplied to the frequency divider 100 and divided into 1/2, and the divided signal is supplied to the gate signal generator 50. Ru.
In the type of f _I =3/4 f _T , the output signal of the PLL 90 is directly supplied to the gate signal generator 50 .

Therefore, in the type of f _I =3/2f _T , the frequency of the output signal of the PLL 40 is 3f _I =9/2f _T , and the frequency of the output signal of the delay circuit 70 is f _I =3/2f _T. Therefore, the frequency of the output signal of the bandpass filter 80, that is, the frequency of the output signal of the PLL 90 is 4f _I = 6f _T , and the frequency of the output signal of the frequency divider 100, that is, the frequency of the signal supplied to the gate signal generator 50 is 2f _I = 3f _T. In addition, in the type of f _I = 3/4 f _T , the frequency of the output signal of PLL40 is
3f _I =9/4f _T and the frequency of the output signal of the delay circuit 70 is f _I =3/4f _T , so the frequency of the output signal of the bandpass filter 80, that is, the signal supplied to the gate signal generator 50 The frequency of becomes 4f _I = 3f _T.

Moreover, in the present invention, the delay time of the delay circuit 70 is a time τ _h − which is shorter than the horizontal period τ _h by τ _d
τ _d . The index signals have a strong correlation between adjacent horizontal periods, and their frequency fluctuations are almost the same. Therefore, if the delay time is set to τ _h −τ _d , equivalently the negative delay time −τ
It becomes _d . That is, time is equivalently advanced by τ _d .

Therefore, the delay time of the photodetector 20 and the bandpass filter 30 is τ ₁ , the delay time between the input and output of the PLL 40 is τ ₂ , the delay time from the mixer 60 to the PLL 90 is τ ₃ , and the delay of the frequency divider 43 is If we consider the time and the delay time of the frequency divider 100 to be 0, then f
_The phase error Δφ of _the output signal of _{the PLL40} is
₁ is Δφ ₁ = (τ ₁ + τ ₂ )・3Δω
......(15) The phase error Δφ ₂ of the output signal of the delay circuit 70 is expressed as Δφ ₂ = (τ ₁ +τ ₂ −τ _d )Δω
......(16) Therefore, the phase error Δφ ₃ of the output signal of the PLL 90 is Δφ ₃ = Δφ ₁ +Δφ ₂ +τ ₃・4Δω = {3(τ ₁ +τ ₂ )+(τ ₁ +τ ₂ −τ _d )+4
τ ₃ }Δω = {4(τ ₁ +τ ₂ +τ ₃ )−τ _d }Δω
......(17) becomes. Therefore, τ _d = 4 (τ ₁ + τ ₂ + τ ₃ )
...... (18) If the delay time τ _h - τ _d of the delay circuit 70 is selected as τ _h - τ _d = τ _h -4 (τ ₁ + τ ₂ + τ ₃ )
...(19), the phase error _Δφ3 of the signal supplied to the gate signal generator 50 becomes 0, and even if the frequency of the index signal changes, the timing of color switching will not shift, and color shift will occur. does not occur.

According to the present invention, at the time when the PLL 40 is locked, the delay circuit 70 has already obtained a delayed version of the stable signal from when the previous PLL 40 was locked by τ _h - τ _d .
After PLL40 locks, mixer 60 to PLL90
A signal with a predetermined frequency of 3f _T is supplied to the gate signal generator 50 after only a delay time τ ₃ has elapsed. Therefore, the above-mentioned scanning start section 1
3 can be made as narrow as in the conventional general method shown in FIG. However, if this continues, the output signal of the delay circuit 70 will be missing at the right end of the effective screen section 12, and the gate signal generator 50 will not be supplied with a signal of the predetermined frequency of _3fT . Therefore, as shown in FIG. 4B, a scan is performed in which only index phosphor stripes are formed on the right side of the effective screen area 12 where color phosphor stripes are formed, in the same way as in the scan start area 13 on the left side. The end portion 14 is provided with a width corresponding to τ _d . By doing so, the effective screen portion 12 is located at the center of the face of the picture tube 10, resulting in a preferable screen.

In addition, since a signal from approximately one horizontal period before is used in this way, the index phosphor stripe is formed to extend to a line position immediately above the effective screen area 12, and an index signal can be obtained even at that line position. Do it like this.

As described above, according to the present invention, it is possible to correct the deviation in color switching timing based on the loop delay time, and it is also possible to correct the deviation in color switching timing based on the loop delay time. There is no inconvenience of being too far to the right.

Note that not only the signal at the 4f _I frequency but also the signals at the f _I , 2f _I , and 3f _I frequencies are obtained from the mixer 60, so if the Q of the band pass filter 80 is relatively low, the band pass filter The output signal of 80 will contain components of frequencies lower than this 4f _I. Therefore, if there is no PLL 90, the duty factors of the gate signals S _R , S _G and S _B will not be the same, and there is a risk that the color balance will be disrupted. If the Q of the bandpass filter 80 is made high enough, its output signal will hardly contain any frequency components lower than 4f _I.
If this is done, the delay time in the bandpass filter 80 will become longer. However, if the PLL 90 is inserted as shown in the figure, the filter effect of the PLL 90 will sufficiently attenuate the frequency components lower than 4f _I , even if the Q of the bandpass filter 80 is not made very high.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional general receiver;
The figure is a system diagram of a receiver using a special method that has already been proposed, FIG. 3 is a system diagram of an example of the receiver of the present invention, and FIG. 4 is a diagram for explaining the screen. 10 is a picture tube, 20 is a photodetector, 30 is a bandpass filter, 40 is a PLL, 70 is a delay circuit, 6
0 is a mixer, 80 is a band pass filter, and 50 is a gate signal generator.

Claims (1)

[Claims] 1. A photodetector that detects light emission when an electron beam scans an index phosphor stripe and outputs an index signal, a PLL that frequency multiplies the index signal, and a phase comparator of this PLL that outputs an index signal. a delay circuit that delays the frequency-divided signals whose phases are compared; a mixer that mixes the output signal of the PLL and the output signal of the delay circuit; and a mixer that mixes the output signal of the mixer with the frequency of the output signal of the PLL and the delay. It has a filter that takes out a signal with a frequency that is the sum of the frequencies of the output signals of the circuit, and a gate signal generator that divides the output signal of this filter and generates a three-phase gate signal to which the signals of each color are sequentially gated. and the delay time of the above delay circuit is τ
h-τd (τh is one horizontal period, and τd is a value that is approximately an integral multiple of the delay time of the index signal from the photodetector to the gate signal generator). Machine.