JPH0352067Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a beam index type color television receiver.

(B) Prior Art As shown in Fig. 1, three primary color phosphors R, G, and B of red, green, and blue are provided in stripes on the inner surface of the face plate 2 of the picture tube 1 with a black guard band 3 in between. Further, an index element 4 made of a short afterglow phosphor is provided thereon via a metal back film (not shown). As shown in FIG. 2, a conventional beam index type color television receiver using this picture tube transmits an optical index signal obtained when the inner surface of the face plate 2 is scanned with a single electron beam to the picture tube. A photoelectric converter 5 provided on the back side converts the signal into an electric signal, and the signal is converted into an electric signal by a filter 6, and then converted into a pulse by a pulse generator 7. This index pulse is converted by a frequency converter 8 into a triplet frequency matching the repetition period of the three primary color phosphors, and is also converted into a sine wave. The write signal thus formed is sent to the first mixer 9 at 3.58MHz.
The frequency sum of the continuous wave CW and the second wave of the next stage is calculated.
In the mixer 10, the frequency difference with the color signal is taken. Therefore, the output of the second mixer 10 is a triplet frequency sine wave whose amplitude and phase are modulated by the color signal. The write signal into which color information has been incorporated in this way is sent to adder 1.
1, it is added to the luminance signal and guided to the electrodes of the picture tube.

As mentioned above, the index signal is modulated by the color signal, and as a result, the electron beam is controlled to impact the phosphor stripes according to the color information, but in order for such control to be performed correctly, The phase of the index signal before being modulated by the color signal must be fixed at a predetermined phase. However, if a pulse is missing in the index pulse train, the phase of the index signal after frequency conversion changes, making accurate hue reproduction impossible.

(c) Purpose of the invention The purpose of the invention is to avoid hue shift due to index pulse omission, and to prevent undesired hue reproduction even during the omission period.

(d) Structure of the invention The invention counts and decodes index pulses to generate a first pulse train synchronized with the position of the red phosphor of the three primary color phosphors, a second pulse train synchronized with the position of the blue phosphor, and a green phosphor. pulse train forming means for forming a third pulse train synchronized with the position of the body;
means for detecting a missing index pulse, a pulse oscillation circuit for compensating for the missing pulse, and means for counting the number of pulses of the pulse oscillation circuit;
The first, second and third pulse trains from the pulse train forming means and the output of the counting means make the phase of the index pulse after the index pulse missing period the same as the phase of the index before the missing period. The beam index type color television receiver is provided with a correcting means for controlling the output of the correcting means, and a means for cutting off the output of the correcting means during the missing period.

(E) Embodiment In FIG. 3, the same parts as in FIG. 2 are given the same symbols for convenience of explanation, and 12 counts and decodes the index pulses given from the pulse generator 7. pulse train forming means for forming a first pulse train synchronized with the position of the red phosphor of the three primary color phosphors, a second pulse train O synchronized with the position of the blue phosphor, and a third pulse train W synchronized with the position of the green phosphor. It is. 13 is a detecting means for detecting a missing index pulse supplied from the pulse generation circuit 7 and outputting a signal corresponding to the missing period; 14 is operated only during the period of the output signal of the detecting means 13 and outputs a signal corresponding to the missing period; A pulse oscillation circuit that generates pulses of the same frequency; 15 a counter that counts the number of pulses of the pulse oscillation circuit 14; 16 a first, second, third pulse train L, O, W from the pulse train forming means 12; correcting means for making the phase of the index pulse after the missing period of the index pulse the same as the phase of the index pulse before the missing period, based on the output of the counter; and 17, the detecting means 13;
This means is activated by the output signal of and cuts off the output of the correction means 16 during the period.

FIG. 4 is a circuit diagram specifically showing the circuits 12 to 17 in FIG.
9, and the first and second D flip-flops 18,
It consists of an OR gate 20 that ORs the outputs of 19, and a decoder 21. The Q output of the first D flip-flop 18, the Q output of the second D flip-flop 19, and the output of the OR gate 20 are the fifth
Shown in Figures 1, 2 and 2. FIG. 5A shows the index pulse as the output of the pulse generator 7,
It is applied to input terminal 22 in FIG. The decoder 21 includes a plurality of NAND gates N ₁ to _{N 9} as shown in the figure.
and an inverter _I1 , of which _N1 ,
The index pulse wave from the input terminal 22 is given as the first input to N ₃ and N ₅ , and N ₂ , N ₄ , and N ₆
The index pulse inverted by the inverter _I1 is applied as a first input to the inverter I1. The Q output chip of the first D flip-flop 18 is given as a second input to N ₁ and N ₆ , and the second D flip-flop 18 is similarly applied to N ₂ and N ₃ .
The Q output of flip-flop 19 is also N ₄ ,
The outputs of the OR gates 20 and 2 are connected to _N5 respectively.
given as input. As a result, a first pulse train synchronized with the position of the red phosphor is generated at the output end of _N7 , a second pulse train synchronized with the position of the blue phosphor is generated at _N8 , and a green pulse train is generated at _N9 . A third pulse train synchronized with the position of the phosphor occurs. The first of these,
The second and third pulse trains are shown in FIG. The detection means 13 is composed of a retriggerable monostable multipipulator, and its output is at a low level when index pulses are continuously applied from the input terminal 22, as shown in FIG. 5B. When an index pulse is missing, the level is high during the missing index pulse. When this high level is applied to the pulse oscillation circuit 14, the pulse oscillation circuit 14 generates a number of pulses that match the number of missing pulses, as shown in FIG. 5C. The counter 15 has the third and fourth D connected as shown in the figure.
It consists of flip-flops 23, 24 and an OR gate 25, and their outputs H, H, and T are shown in FIG.
This occurs as shown in F and G. The correction means 16
HAND gates N ₁₀ , N ₁₁ , N ₁₂ and multiple input type
The first input of NAND gates _N10 , _{N11 ,} and _N12 is counter 1.
Outputs E, H, and G from 5 are given, respectively, and the second inputs are the first, second, and third pulse trains L,
O, W are given. The cutoff means 17 is constituted by an AND gate A, and is controlled by a signal obtained by inverting the output LOW of the detection means 13 by an inverter _I2 .

Next, the operation shown in FIG. 4 will be explained for the case where five index pulses are missing as shown in FIG. 5A.

The time constant τ of the detection means 13 is selected so that T ₁ < _τ < 2T ₁ with respect to the period T 1 of the index pulse. Therefore, if a drop occurs in the index pulse applied to the input terminal 22, Detection means 13
The output becomes high level, and in response, five pulses, which are the same as the number of missing pulses, are generated from the pulse oscillation circuit 14. The outputs E, H, and T of the counter 15 that count these pulses are as shown in FIG. of
When taken with NAND gates N ₁₀ , N ₁₁ , and N ₁₂ , the outputs are as shown in Figure 5.
The output of the NAND gate _N13 has the same phase before and after the pulse loss ends.

However, during the pulse missing period the wide 2
Since two pulses P ₁ and P ₂ are occurring, color synchronization cannot be achieved during this missing period, resulting in incorrect color reproduction during the missing period.

In order to prevent this inconvenience, in addition to the AND gate A which inverts the output of the detection means 13 with an inverter _I2 to form the cutoff means 17, the generation of an index signal at the output terminal 26 during the missing period is prevented. . Therefore, the output of the second mixer 10 shown in FIG. 3 is not generated during the missing period, and only the luminance signal is provided to the picture tube 1. In such a case, the reproduced image will not have a wrong hue, so it will not be difficult to see.

In order to ensure that the color signal is cut off during the missing period, an analog switch 27 is provided after the second mixer 10 as shown in FIG. It may be open during the period. The other parts in FIG. 6 are the same as in FIG. 3.

(f) Effects of the invention According to the invention, even if an index pulse is missing, an index pulse with the same phase as before the dropout can be obtained, so the color synchronization after the dropout period can be set correctly. Also, since the color signal is cut off during the missing period, it is possible to avoid an unpleasant hue state due to color synchronization disturbance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the inner surface of the face plate of a picture tube, and FIG. 2 is a block diagram of a conventional beam index type color television receiver using the picture tube shown in FIG. Fig. 3 is a block diagram of a beam index type color television receiver implementing the present invention, Fig. 4 is a circuit diagram of its main parts, and Fig. 5 is a signal waveform diagram of each part in Fig. 4. . FIG. 6 is a block diagram of another embodiment of the present invention. A... Index pulse, 12... Pulse train forming means, 13... Detecting means, 14... Pulse oscillation circuit, 15... Counter, 16... Correction means,
17...Blocking means.

Claims (1)

[Scope of utility model registration request] A first pulse train synchronized with the position of the red phosphor of the three primary color phosphors, a second pulse train synchronized with the position of the blue phosphor, and a third pulse train synchronized with the position of the green phosphor by counting and decoding index pulses. a pulse train forming means for forming a pulse train, a means for detecting missing index pulses, a pulse oscillation circuit for compensating for the missing pulses, a means for counting the number of pulses of the pulse oscillation circuit, a correction means for making the phase of the index pulse after the missing period of the index pulse the same as the phase of the index pulse before the missing period using the first, second and third pulse trains and the output of the counting means; and means for cutting off the output of the correction means during the missing period.