JPH0430793B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a beam index type color television receiver.

(b) Prior art A beam index type color television receiver has three primary color phosphors of red, green, and blue repeatedly arranged in a stripe pattern, and m/n (m, n) between these phosphors.
is an index signal obtained from an index element when an electron beam emitted from a single electron gun is swept over a surface consisting of index elements arranged repeatedly in a stripe shape with a regular relationship (all positive integers). is pulsed to form an index pulse, the frequency of the index pulse is divided into 1/m and multiplied by n to form a control signal with a triplet frequency corresponding to the repetition period of the three primary color phosphors, and the control signal is This is a television receiver in which the electron beam is modulated with a video signal to impact a predetermined phosphor, but the main components of the conventional example are as shown in Figure 1, in which the electron beam is generated from an index element. In addition, the index signal S converted into an electric signal by the photoelectric converter is filtered by a band pass filter 1, pulsed by a pulse generator/reset pulse circuit 2 to form an index pulse, and the index pulse is divided into 1/m. The frequency is divided by frequency divider 3. Here, since m and n are set to m=3 and n=2, the frequency division 3 becomes a 1/3 frequency divider. The next stage decoder 4 multiplies the index pulse by n and supplies it to the first mixer 5. The first mixer 5 calculates the frequency sum of the triplet frequency index pulse Sp and the 3.58 MHz carrier CW, and the next second mixer 6 calculates the frequency difference with the color signal C. the result,
The index signal has its amplitude and phase modulated by the color signal. The index signal subjected to such modulation is added to the luminance signal Y in an adder 7 and supplied to the cathode ray tube through an amplifier 8. The reset pulse Sr output from the pulse generator/reset pulse circuit 2 resets the frequency divider 3 so that the frequency is divided by 1/m.

By the way, it has been confirmed that the number of index pulses increases due to the inclusion of noise pulses, and that pulses are missing in areas with low brightness. However, if one pulse is missing from the index pulse Sp input to the frequency divider 3 as shown in FIG. 2A, the triplet frequency index pulse obtained from the decoder 4 will be as shown in FIG. 2B. What had previously occurred in the red R phase now occurs in the blue B phase, with the phase delayed by 120 degrees. The three primary color phosphors are arranged in the order of red R, green G, and blue B at intervals of 120° in terms of phase. Furthermore, if two pulses are missing as shown in FIG. 2C, there will be a delay of 240° as shown in FIG. 2D.

On the other hand, when the index pulse increases by one,
It is easy to understand that it advances 120 degrees, and if it increases by two, it advances 240 degrees. If the index pulse whose phase has changed due to omission or increase is processed in the subsequent first mixer 5 or the like, correct colors cannot be reproduced.

(c) Object of the Invention An object of the present invention is to provide a beam index type color television receiver that reproduces accurate colors regardless of the increase or decrease of index pulses.

(D) Structure of the Invention The beam index type color television receiver of the present invention includes a detection means for detecting missing index pulses, and a detection means for detecting missing index pulses, and detects the same number of pulses as the number of missing index pulses, which is controlled by the output of the detecting means. pulse generating means that generates a
1, 2...), m・k+1,..., m・k+(m-
1), a first determining means for determining whether the
The number of index pulses has increased compared to normal,
m・k, m・k+1, ..., m・k+(m−1)
a second discriminating means for discriminating whether the index pulse is one of the index pulses, and m pulse trains whose output pulse phases are 0°, 2π/m, . . . , (m-1)2π/m by counting the index pulses; and a pulse train output from the phase means in accordance with the outputs of the first and second discrimination circuits so that an index pulse train of a constant phase is obtained regardless of the omission or increase of the index pulses. A switching means for switching is provided.

(E) Embodiment In FIG. 3, the same parts as in FIG. Pulse generating means 11 is controlled and generates the same number of pulses as the number of missing index pulses, and 11 counts the output pulses of the pulse generating means so that the number of pulses output from the pulse generating means is m·k (k=0 , 1, 2...), m・k
+1, .
+1, . . . , m.
A phase means 14 outputs m pulse trains of 2π/m, . The switching means switches the pulse train of the output of the phase means in accordance with the output of the first and second discrimination circuits.

Fig. 4 shows the configuration within the dotted line in Fig. 3 in more detail, 15 is an index pulse rising detection circuit, 9' is a retriggerable first monomultivibrator, and its time constant _T1 is the index pulse rising edge detection circuit. When the pulse repetition period is Ti, Ti<T ₁ <
Selected by 2Ti. This first monomultivibrator 9' serves to detect missing index pulses. 10' is a pulse oscillation circuit, and 11' is a second ternary counter. 16 is a second retriggerable mono-multivibrator whose time constant T ₂ is chosen to satisfy 1/2Ti<T ₂ <Ti. This second monomultivibrator 16 detects an increase in index pulses. 17 is a third ternary counter. 18 is a first ternary counter which divides the frequency of the index pulse by 1/3, and its output is given to a decoder 19. A comparison circuit 20 compares the outputs of the first ternary counter 18 and the third ternary counter 17 to determine the increase in the number of index pulses. The second mono-multivibrator 16, the third ternary counter 17, and the comparison circuit 2
0 constitutes the second discriminating means 12 in FIG. 2
1 and 22 are first and second switching circuits constituting the switching means 14 in FIG. 3, and the first switching circuit 21
is controlled by a comparison circuit 20, and the second switching circuit 22 is controlled by a second ternary counter 11' serving as the first discrimination means 11. The configuration of FIG. 4 is shown in detail in FIG.

Next, the operation will be explained with reference to the waveform diagram in FIG.

Since the time constant T ₁ of the first mono-multivibrator 16 is set to Ti<T ₁ <2Ti, if there is no dropout in the index pulse, the output simply remains at a low level; occurs and the pulse interval becomes longer than _T1 , it becomes high level, and returns to low level with the next pulse. And if z pulses are missing, zTi−(T ₁
-Ti) outputs a pulse with a width of -Ti). If this pulse activates the oscillation circuit 10' whose cycle is selected to be the same as that of the index pulse, the same number of pulse outputs as in the case of missing pulses can be obtained. This number of pulses is counted by a ternary counter 2. On the other hand, since the time constant T ₂ of the second mono-multivibrator 16 is set to 1/2 Ti < T ₂ < Ti, the second mono-multivibrator 16 outputs the same number of pulses as the input index pulses during normal operation. This pulse is counted by a third ternary counter 17. The count results of the first ternary counter 18 and the third ternary counter 17 match under normal conditions. However, if the noise pulse 25 is mixed between the index pulses and the number of pulses increases, that is, if the pulse interval becomes shorter than _T2 , the second monomultivibrator 16 is retriggered and the output pulse is less than the input pulse. As a result, the first and third ternary counters 18,
The counting results for 17 will be different. The comparison circuit 20 compares these outputs to determine how many have increased. Incidentally, the third ternary counter 17 is
〓〓 is generated, and the comparison circuit 20 outputs 〓〓.
The output shown by 〓 is produced. The output of the decoder 19 is switched in the first switching circuit 21 by the output of the comparison circuit 20, and is switched at the part where the pulse increases as shown in 222324, and then the output of the decoder 19 is switched in the second switching circuit 22 at the part where the pulse increases. One index pulse train 25 switched by the output 〓 〓 21 of the advance counter 11' is output. In this pulse train 25, even if the index pulse is missing or increased, the pulse phase after the missing or increased index pulse is the same as the pulse phase before the missing or increased index pulse.

In the example shown in Figure 6, there are two missing index pulses.
The case where the increase is 1 and the case where the increase is 1 are shown.
The number of missing pulses is 3k+1 (k=0, 1, 2...)
In the case of , the output pulse is advanced by 120°, and in the case of 3k+2, the output pulse is advanced by 120°.
240° advance, conversely the number of index pulses increases
When 3k+1, the phase is delayed by 120°, and when 3k+2, it is 240°.
The switching shall be performed so as to produce a phase-delayed output.

(F) Effects of the Invention According to the present invention, regardless of the index pulse dropout or increase, a pulse having the same phase as the index pulse before the dropout or increase can be obtained, so that correct color reproduction is always possible.

[Brief explanation of drawings]

Figure 1 is a schematic block diagram of a conventional beam index type color television receiver;
The figure is an explanatory diagram thereof. FIG. 3 is a schematic block diagram of a beam index type color television receiver embodying the present invention, FIG. 4 is a block diagram showing a part of the receiver in detail, and FIG. The circuit diagram shown in FIG. 6 is an explanatory diagram of FIG. 5. 9...Detection circuit, 10...Pulse generating means, 1
1...First discrimination means, 12...Second discrimination means, 1
3...Phase means, 14...Switching means.

Claims (1)

[Claims] 1 Red, green, blue, repeatedly arranged in stripes,
and m/n (m,
When an electron beam emitted from a single electron gun sweeps over a surface consisting of index elements arranged repeatedly in a stripe pattern with a regular relationship (n is a positive integer), the index obtained from the index elements is The signal is pulsed to produce an index pulse, the frequency of the index pulse is divided into 1/m and multiplied by n to form a control signal with a triplet frequency corresponding to the repetition period of the three primary color phosphors, and the control signal is In a beam index type color television receiver in which an electron beam modulated by a video signal is made to impact a predetermined phosphor, there is provided a detection means for detecting a missing index pulse, and control based on the output of the detection means. pulse generating means that generates the same number of pulses as the number of missing index pulses, and counting the output pulses of the pulse generating means and determining the number of pulses output from the pulse generating means m·k (k=0, 1 , 2...
...), m·k+1, ..., m·k+(m-1), and the increased number of index pulses is m·k,
m·k+1, . . . , mk+(m−1), and counting the index pulses to determine whether the phase of the output pulse is 0°, 2π/m, . (m-1) A phase means for outputting m pulse trains of 2π/m, and a pulse train output from the phase means so as to obtain an index pulse train of a constant phase regardless of the dropout or increase of the index pulses. 1. A beam index type color television receiver comprising: switching means for switching according to the outputs of the first and second discrimination circuits.