JPS636946Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a chroma scan device in a beam index type color television receiver.

In a beam index type color television receiver, it is confirmed which phosphor is hit by the single electron beam, and then the color tone and intensity of the light to be emitted is controlled to reproduce an appropriate and bright receiving screen. Therefore, it is necessary to detect the index signal without interruption. To do this, a small amount of the beam is constantly flowing, and therefore, not only the desired phosphor but also other phosphors are irradiated with the electron beam.
There is a problem that the saturation level of the primary colors deteriorates.

To address this problem, color saturation has been improved by a method called a chroma scan method.

For example, when reproducing the primary color red, as shown in Figure 1a, the intensity of the electron beam is has the positional relationship shown in FIG. 1b, with the electron beam being strongest at the R position, and falling below the beam cut-off voltage at the B and G positions.

In the chroma scan method, by superimposing a chroma scan signal on the horizontal deflection voltage or by providing an auxiliary coil for chroma scan and applying the chroma scan signal to the electron beam, a minute deflection voltage is added to the horizontal deflection voltage, and the horizontal The deflection speed is shown in Figure 1c.
The scanning speed becomes slower on the phosphor of R, as shown in B,
On the G phosphor, the scanning speed increases.

As shown in Figure 1d, the amount of phosphor irradiation beam is R
Since it increases at the position B and G and decreases at the positions B and G, as a result, the red light is emitted strongly, the amount of light emitted by unnecessary phosphors is reduced, and the degree of saturation is improved.

However, when reproducing an intermediate color, for example, yellow, the horizontal polarization velocity, the waveform of the irradiation beam amount, and the positional relationship of the phosphor stripes are as shown in FIG. 1e. Due to the chroma scan, the beam amount is concentrated on the non-emitting guard band 1 between R and G, and the brightness of the reproduced yellow color decreases.

Also, when the phase of the color writing signal shifts slightly from yellow to red, for example, the amount of beam irradiated to the G phosphor decreases rapidly, and what should have been a reddish yellow becomes red. The color becomes a similar reproduction color.

For the same reason, an intermediate color shift also occurs when an intermediate color is reproduced in a state where a phase shift of the index signal occurs due to variations in the linearity of horizontal scanning.

If chroma scan is strongly applied and emphasis is placed on the saturation of the primary colors as described above, the brightness of intermediate colors will decrease and the hue will change rapidly, making the reproduced image look unnatural.

In order to properly reproduce intermediate colors, the applicant has already proposed the following improvements.

That is, when reproducing the primary colors, a minute deflection is applied to the horizontal deflection at the same frequency as the three primary color phosphor pitches, and when reproducing intermediate colors, the minute deflection is applied at three times the frequency (Japanese Patent Laid-Open No. 149723/1983). .

This method has the problem of requiring a plurality of circuits, since minute deflection must be performed using chroma scan signals of different frequencies when primary colors are reproduced and when intermediate colors are reproduced.

The present invention suggests that when the beam spot diameter is about three times the width of the phosphor, it is better not to perform chroma scanning when reproducing intermediate colors, since the brightness of the reproduced intermediate colors will be high and the saturation will be sufficient. Focusing on this, we perform sufficient chroma scan when reproducing primary colors,
It is an object of the present invention to provide a chroma scan device that does not perform chroma scan when reproducing intermediate colors or performs less chroma scan than when reproducing primary colors, and can improve color saturation of both primary colors and intermediate colors.

As shown in FIG. 2, a beam index type color television receiver converts an index signal 5 obtained from a photoelectric converter 4 provided in the funnel of a cathode ray tube 3 through a filter 6 to a frequency converter. 7 and is now converted into a triplet repetition frequency of the three primary color phosphor stripes and mixed with the color signal in a mixer 8.

The color signal, which has been made to match the phosphor by mixing with the frequency-converted index signal in this way, is further added to the luminance signal (Y signal) in the adder 9, and the color writing signal 10 is added to the cathode ray tube 3. guided by grid electrodes.

The cathode ray tube 3 is provided with a deflection coil 11 and an auxiliary deflection coil 12 , and a horizontal deflection signal is applied to the deflection coil 11 and a chroma scan signal 13 is applied to the auxiliary deflection coil 12 .

The chroma scan signal 13 is a color signal and a color carrier wave (3.58MHz) that are processed by the control circuit 14, and when the color write signal 10 reproduces primary colors, the chroma scan signal 13 is output, but when the color write signal 10 reproduces intermediate colors, it outputs the chroma scan signal 13. Scanning is performed using only the average horizontal deflection signal without outputting it.

The configuration in which the control circuit 14 distinguishes between the primary color signal and the intermediate color signal of the carrier color signal and outputs the chroma scan signal is detailed in the above-mentioned Japanese Patent Laid-Open No. 149723/1982, but the outline thereof is as follows. .

The R, G, B primary color signals and intermediate colors in the received NTSC signal are vector-converted by a vector converter 15 so that the amplitudes thereof are made constant and the primary color signals have a phase difference of 120°.

The frequency of the vector-converted signal is tripled by the first multiplier circuit 16, and by this circuit,
R, G, B are uniformly Acos3wt, yellow,
Intermediate colors such as cyan and magenta are uniformly Acos (3wt
+180°). Therefore, there is no distinction between colors, and only primary colors and intermediate colors remain as phase differences.

The signal 17 passes through a limiter 18 to a demodulator 19
is added to the reference signal 20, and mixed with the reference signal 20, so that only the primary color signal is demodulated.

The reference signal 20 is a color carrier wave (frequency 3.58MHz) generated by the receiver, which is converted into a signal with a phase of 60° [Bcos (wt + 60°)] by an appropriate phase shift circuit, and then
It is multiplied by 3 by the multiplier circuit 21 and further inverted by the inverting circuit 22.
This is the signal made by Bcoswt through.

Therefore, the demodulation axis of the demodulator 19 matches the phase of the primary color signal, and a positive demodulation output 23 is generated only at a position corresponding to the primary color signal in the color signal.

The voltage of this demodulated output 23 and the color writing signal 10
By inputting a signal whose phase is shifted by 90 degrees to the amplitude modulator 24 and applying the amplitude-modulated signal current to the auxiliary deflection coil 12 only when reproducing the primary color signal, chroma scan is performed only when reproducing the primary color signal, and intermediate color reproduction is performed. Sometimes it is possible to stop chromascanning.

Note that when reproducing intermediate colors, the amplitude modulator 24 is configured to increase the aperture ratio of the amplitude of the color writing signal 10 and output it, so that chroma scan is strongly applied when reproducing primary colors, and chroma scan is applied when reproducing intermediate colors. It is also possible to limit it weakly.

It should be noted that the present invention is not limited to the above-mentioned configuration, and it goes without saying that various modifications can be made within the technical scope of the claims of the utility model registration.

As described above, the present invention improves the brightness reduction and hue shift caused by chroma scan in intermediate colors, and at the same time performs sufficient chroma scan in primary colors. This is an excellent invention that has many advantages, such as solving problems with television receivers.

[Brief explanation of the drawing]

1A to 1E are explanatory diagrams of a fluorescent surface of a cathode ray tube and an initial signal waveform showing the principle of chroma scan, and FIG. 2 is a block explanatory diagram showing the configuration of an apparatus according to the present invention. 10...Color write signal, 13...Chroma scan signal, 14...Control circuit.

Claims (1)

[Scope of utility model registration request] Three primary color phosphors are arranged repeatedly in stripes on the inner surface of the face plate of the cathode ray tube with a black guard band in between, and a predetermined phosphor is bombarded with an electron beam emitted from a single electron gun.
In a beam index color television that performs chroma scanning by applying a chroma scan signal to the electron beam at the same time as a horizontal deflection signal, when the electron beam irradiates only one of the three primary color phosphors to reproduce the primary colors. The beam indicator is characterized in that it is equipped with a control circuit that outputs a chroma scan signal, irradiates the electron beam across two of the three primary color phosphors, and stops or limits the output of the chroma scan signal when expressing an intermediate color. Chroma scanning device for Tux-type color television receivers.