JPH0221197B2 - - 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 on the inner surface of a face plate 1a of a picture tube 1.
G and B are arranged repeatedly in sequence so as to sandwich a black guard band 2, and a first index element 4 made of a phosphor that emits short-lasting light through a metal back 3 made of an aluminum film is attached to the inner surface of the three primary colors. Using the index signal obtained from the index element when an electron beam emitted from a single electron gun sweeps a surface repeatedly arranged with phosphors R, G, and B in a certain relationship as shown in FIG. This is a television receiver in which the electron beam 5 is controlled so as to impact predetermined three primary color phosphors.
More specifically, the optical signal 6 generated from the index element is converted into an electrical signal by a photoelectric converter 7 provided in the funnel portion of the picture tube 1, and the resulting index signal is filtered by a filter 8 and sent to an index processing circuit. 9, where it is converted into an array period of the three primary color phosphors R, G, B, ie, a triplet repetition frequency. Then, it is mixed with a color signal in the next mixing circuit 10, modulated by the color signal, and applied to the grid electrode of the picture tube 1. 1
1 is a video signal processing circuit which supplies a 3.58 MHz color subcarrier and a color signal to the mixing circuit 10, a luminance signal to the cathode electrode of the picture tube 1, and a synchronization signal to the index processing circuit 9. give. 12 is a deflection circuit, and 13 is a deflection yoke.

In such beam index type color television receivers, a beam scanning method called chroma scan has been proposed to eliminate the reduction in brightness and deterioration of color saturation caused by guard bands.
That is, when reproducing the primary colors of red R, green G, and blue B, the beam speed on the phosphor is slowed down by superimposing a minute deflection of the triplet frequency on the horizontal deflection of the electron beam, and the beam speed on the guard band 2 is reduced. If the beam is to be scanned quickly, but intermediate colors are to be reproduced, the beam speed on the phosphor is similarly slowed down by controlling the scanning speed with the phosphor frequency (3 times the triplet frequency), and the beam speed above the guard band 2 is This method allows the beam to scan quickly and increases the brightness of the screen without reducing color purity and resolution in both primary and intermediate colors. Reference numeral 14 denotes an auxiliary deflection coil for chroma scan, and a chroma scan signal is supplied from the index processing circuit 9, for example. By the way, in such a chroma scan, the frequency of the chroma scan signal applied to the auxiliary deflection coil 14 when intermediate colors are generated is three times the frequency when primary colors are generated, as described above. 14, and switching the frequency for chroma scanning depending on the primary colors and intermediate colors has the drawback that it complicates the circuit configuration. For this reason, a method has been proposed in which the diameter of the electron beam spot is increased and chroma scanning is performed at the same frequency for both primary colors and intermediate colors. However, in this case, other phosphors are also emitted when the primary colors are used, so the color saturation cannot be improved sufficiently.

In view of these points, the present invention proposes an excellent chroma scan type beam index type color television receiver.

That is, in the present invention, slight deflection is performed at the triplet frequency both when primary colors and intermediate colors are generated, and instead of this, a means is provided to change the spot diameter of the electron beam between when primary colors and intermediate colors are generated. The spot diameter when intermediate colors are generated is made larger than the spot diameter when primary colors are generated. In addition, when the guard band 2 having the same width as the width of the three primary color phosphors is installed, the diameter of the electron beam spot when the primary colors are generated shall be a value not more than three times the width of one phosphor. For example, in a 20-inch picture tube, the phosphor width is approximately 0.13
Considering that the electron beam current is 1 mA.
Therefore, it is necessary to keep the spot diameter to about 0.13 x 3 = 0.39 mm. On the other hand, the diameter of the electron beam spot when intermediate colors are generated may be made larger to the extent that it does not exceed twice the spot diameter when primary colors are generated.

Figure 3 shows when primary colors occur (for example, when red occurs),
Figure 4 shows the electron beam 5 when an intermediate color is generated;
The relationship (a) between the phosphors R, G, B and the guard band 2, the color generation drive signal (b), the electron beam current (c), and the chroma scan signal (d) are shown, respectively. Note that the means for changing the electron beam spot is explained in the fifth section.
As shown in the figure. In FIG. 5, 15 is a first multiplier circuit that multiplies the frequency of the color signal converted into 120° intervals for the three primary colors by 3, and its output is sent to the limiter 1.
6 to the discrimination circuit 18. 17 is
A second multiplier circuit multiplies the frequency of the 3.58 MHz color subcarrier by three, and its output is given to the discrimination circuit 18. The discrimination circuit 18 discriminates between primary colors and intermediate colors by taking the frequency difference between the color signal multiplied by 3 and the color subcarrier. That is, in the case of primary colors, the phase difference is 0, but in the case of intermediate colors, a phase difference remains, so different voltages are generated for primary colors and intermediate colors. In response, the discrimination circuit 18 outputs different voltages for primary colors and intermediate colors, and this output voltage is applied to the focusing electrode 20 of the picture tube 1 through the amplifier 19. This makes it possible to control the spot diameter of the electron beam to be small when primary colors are generated and to be large when intermediate colors are generated. FIG. 6 shows the relationship between the output voltage of the discrimination circuit 18 and the color pattern signal a.

As described above, according to the present invention, chroma scanning is performed at the same frequency (triplet frequency) for both primary colors and intermediate colors, so there is no difficulty in driving the auxiliary deflection yoke 14, and there is no need to switch the frequency. There is an effect that there is no. In addition, since the electron beam spot diameter is small for primary colors and large for intermediate colors, it does not impact other phosphors and reproduce undesired colors when primary colors are generated, and on the other hand, intermediate colors are generated. The present invention is extremely effective since it is possible to sufficiently illuminate the phosphors on both sides of the guard band by holding the guard band in between, and to obtain a sufficient degree of color saturation when intermediate colors are generated.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the inner surface of a face plate of a beam index color picture tube, and FIG. 2 is a block diagram schematically showing a beam index color television receiver. 3 and 4 are diagrams for explaining a beam index type color television receiver embodying the present invention, and FIG. 5 is a diagram showing an example of a part of the circuit configuration used in the present invention. FIG. 6 is an explanatory diagram of FIG. 5. 1... picture tube, 1a... face plate,
R, G, B...three primary color phosphors, 2...guard band, 3...metal back layer, 5...electron beam,
15, 17...multiplication circuit, 18...discrimination circuit,
20... Focusing electrode.

Claims (1)

[Scope of Claims] 1. A surface on which three primary color phosphors are sequentially and repeatedly arranged in stripes on the inner surface of a face plate of a receiver, with a black guard band interposed therebetween, and an index element is arranged on top of the stripes with a metal back layer interposed therebetween. By using the index signal obtained when sweeping the electron beam emitted from the single electronic lock, the electron beam is made to impact a predetermined phosphor, and when primary colors and intermediate colors are generated, the three primary color phosphors are In a beam index type color television receiver in which a minute deflection with a frequency equal to the triple repetition frequency of 1. A beam index type color television receiver, characterized in that it is provided with means for making the size larger than the original size. 2. The means includes a circuit that multiplies the frequency of the color signal converted into a 120° interval by three, a circuit that multiplies the frequency of the color subcarrier by three, and a circuit that multiplies the frequency of the color signal multiplied by three and the color subcarrier. 2. The beam index type color television receiver according to claim 1, further comprising a discrimination circuit for discriminating between primary colors and intermediate colors by measuring the frequency difference and generating different outputs, the outputs of which are applied to the electron beam focusing means of the picture tube. Machine.