JPH0313793B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a beam index color television receiver.

As shown in FIG. 1, such a color television receiver has three primary color phosphors R, G, and B repeatedly arranged in stripes on the inner surface of a face plate 2 of a picture tube 1, sandwiching a black guard band 3. First index elements 5 made of a short-lasting phosphor are repeatedly disposed on the inner surface in a fixed relationship through an aluminum film 4, and the first index elements 5 are arranged repeatedly in a fixed relationship with each other through an aluminum film 4. A second index element 6 is provided in a position preceding the index element 6, so that when the electron beam emitted by the single electron gun is swept, the electron beam impacts a predetermined phosphor based on the index signal obtained from the index element. It is.

In other words, as shown in FIG. 2, the index signal obtained by converting the optical signal 8 generated from the index element into an electrical signal by the photoelectric converter 7 provided in the funnel portion of the picture tube 1 passes through the filter 9. and is added to the index processing circuit 10 to generate a frequency based on the arrangement period of the three primary color phosphor stripes (usually referred to as the "triplet frequency").
is converted to

This frequency-converted signal functions as an electron beam scraping control signal, but this control signal is modulated by the video signal in the coupling circuit 11 and becomes sufficient to control the electron beam. In FIG. 2, 12 is a deflection circuit, and 13 is a deflection yoke.

In the index processing circuit 10, the phase of the scraping control signal obtained by frequency conversion becomes constant (for example, corresponding to the red phosphor R), and this is phase modulated by the video signal to change the phase. However, the phase of the scraping control signal is determined by its initial setting.

Since this setting is performed at the start end of each horizontal scan, if a detection error of the index signal occurs due to the video signal at the start end, the phase of the scraping control signal will change by 120° or 240°. Therefore, accurate colors cannot be reproduced.

In order to eliminate such detection errors, the prior art devised by the present inventor is to maintain the level of the video signal at the scanning start end at a constant level for a certain period of time as shown in FIG.
The purpose is to keep the intensity of the electron beam constant during this certain period. In FIG. 3, 14 to 17 are first to fourth switches, and these switches are turned on when a low level is applied to their control terminals G1 to G4, and turned off when a high level is applied to their control terminals. shall be configured as follows.

The horizontal retrace pulse d applied to the terminal 18 is inverted by the inverter 19 and applied to the control terminal G4 of the fourth switch 17, and is further applied to the inverter 2.
3 to the control terminal G3 of the third switch 16 with its original polarity. The horizontal retrace pulse e inverted by the inverter 19 is applied to a one-shot multivibrator 20 and delayed, producing a positive polarity pulse as shown in FIG. 4f. This pulse f and the inverted horizontal retrace pulse e are input to the NAND circuit 21, and a pulse g corresponding to the difference in pulse width is generated with negative polarity and is applied to the control terminal G2 of the second switch 15, while passing through the inverter 22. The positive polarity pulse h is applied to the first switch 14
is supplied to the control terminal G1 of. Since the signals applied to the control terminals G1 and G2 of the first and second switches 14 and 15 have opposite polarities, when one is on, the other is off. 3rd and 4th switches 16, 17
The same applies to

The video signal a supplied to the terminal 24 is cut off by turning off the first switch 14 during period _t2 , and by turning on the second switch 15 in the interval, the voltage V1 selected by the volume control 25 is applied to the line 26. . During the other periods, the first switch 14 is on and the second switch 15 is off, so the video signal at the terminal 24 is output to the line 26 as is. As a result of the above, the signal on line 26 is b [see Figure 4]
However, this signal b is further changed to c by the third and fourth switches 16 and 17. That is,
The third switch 16 receives a positive retrace pulse d to the control terminal G3 and is turned off for this period _t1 , while the fourth switch 17 receives a negative retrace pulse e during that period and is turned on. This is because the output line 26 is held at the ground level.

In this way, the video signal c obtained on the output line 26 is maintained at a constant level during the constant period _t2 following the horizontal retrace period, so the intensity of the electron beam during this constant period is constant. Desired index signals should be obtained from index elements 6 and 5. However, in reality, the position of the above-mentioned period _t2 on the inner surface of the face plate may shift due to output fluctuations of the deflection circuit, high voltage circuit, etc., resulting in the inconvenience that the image on the screen is cut off at the scanning start end. occurs.

The present invention aims to eliminate such drawbacks.

The difference between the prior art shown in FIG. 3 and the prior art shown in FIG. 3 in which the present invention is implemented in FIG. 5 is that a circuit 27 is provided for synchronizing the end of the period in which the video signal is cut at the scan start end with the index signal.

This circuit 27 has a negative horizontal retrace pulse e generated at the output of the inverter 19 as a set input, a pulse obtained by inverting the index signal i (FIG. 6) by an inverter 28 as a timing input,
D flip-flop 29 with data input grounded
and a multivibrator 30 which inputs the output j of the D flip-flop and outputs the pulse shown in FIG. 6k, and the one-shot multivibrator 20 is reset by the output pulse k. The first index signal i originates from the second index element 6 and the subsequent ones originate from the first index element 5, but in the illustrated embodiment they are synchronized with the falling edge of the first index pulse. A reset pulse k is generated from the circuit 27, and the one-shot multivibrator 20 is reset. Therefore, as shown in FIG. 6g', the output of the NAND circuit 21 ends in synchronization with the falling edge of the first index pulse.
The pulse width is shorter than the output g of the NAND circuit 21 (the time axis is shown enlarged in FIG. 6 compared to FIG. 4). In the above, it goes without saying that it may be synchronized with, for example, the second index signal.

In this way, according to the present invention, the end point of the cut period of the video signal is determined in synchronization with the index signal, so the phase of the scraping control signal can be set. , it is possible to set the phase of the scraping control signal] The subsequent video signal is not cut, so even if the output of the deflection circuit or high-voltage circuit changes, the image at the scanning start end of the screen will not be deleted. Extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the inner surface of a face plate of a beam index type picture tube, and FIG. 2 is a block diagram showing an outline of a beam index type color television receiver. FIG. 3 is a circuit diagram of the main part of the prior art, and FIG. 4 is an explanatory waveform diagram thereof. FIG. 5 is a circuit diagram of a main part of a beam index type color television receiver embodying the present invention, and FIG. 6 is an explanatory waveform diagram thereof. 1... Picture tube, 2... Face plate, 5, 6...
Index element, 27...synchronizing circuit,
R, G, B...three primary color phosphors, a...video signal, i...
index signal.

Claims (1)

[Scope of Claims] 1 Consists of three primary color phosphors of red, green, and blue repeatedly arranged on the inner surface of the face plate of a picture tube, and an index element repeatedly arranged in regular relationship with these phosphors. A write control signal is created based on the index signal obtained from the index element when the surface is swept with an electron beam emitted from a single electron gun, and the control signal is modulated with a video signal so that the electron beam reaches a predetermined level. In a beam index type color television receiver, the electron beam intensity is made constant at the start end of the sweep scan by impacting the light body and cutting off the video signal at the start end of the sweep scan, wherein the electron beam intensity is made constant. In order to synchronize the end timing of the fixed period _t2 with the index signal, the index signal detecting means 7, 9, 10 for detecting the index signal, and the index signal i generated at the start end of the sweep scan are provided. Input one end time setting signal k synchronized with this index signal.
a reset means 27 that outputs a horizontal pulse e and the end time setting signal k, and a pulse signal g whose start timing is set by the horizontal pulse e and end timing is set by the end time setting signal k. ', the period setting means 19, ₂ for setting the constant intensity period t2.
0, 21, 22. A beam index type color television receiver comprising: