JPH0448065Y2 - - 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 A beam index type color television receiver has three primary color phosphors of red, green, and blue repeatedly arranged in stripes on the inner surface of the face plate of the picture tube, and these phosphors are regularly associated with each other. When an electron beam emitted from a single electron gun is swept over a surface having index elements arranged repeatedly, the electron beam bombards a predetermined phosphor using an index signal obtained from the index element. This is how it was done.

By the way, there are two signal processing systems for beam index type color television receivers: the pulse drive system shown in FIG. 1 and the sine drive system shown in FIG. 2.

In FIG. 1, 2 is a demodulation circuit that demodulates R, G, and B primary color signals from a video signal applied to terminal 1. Reference numeral 4 designates a circuit for forming pulses of a triplet frequency corresponding to the arrangement period of the three primary color phosphors from the index signal applied to the terminal 3. 5 is the triplet frequency pulse +
This is a three-phase pulse generation circuit that generates a pulse train group of three phases: 120°, 0°, and -120°. Reference numerals 6, 7, and 8 are gate circuits that are gated by the pulses of the pulse train group and allow the R, G, and B signals from the demodulation circuit 2 to pass through, and their outputs are led to the output terminal 10 through the broadband amplifier 9. Applied to the electron gun of the picture tube.

In this way, the pulse drive type transmits a single beam emitted to the R, G, and B phosphors.
Scanning is performed with a beam amount that matches the brightness of each of the G and B phosphors.

In this case, the R, G, and B rectangular wave signals outputted from the gate circuits 6, 7, and 8 need to be applied to the picture tube while their level ratio and phase are maintained accurately. The R, G, and B signals must be amplified and passed as rectangular waves. Therefore, from the direct current of this amplifier 9, the above R,
An extremely wide band (0 to 15 MHz) characteristic is required that passes up to the third harmonic of the triplet frequency (usually selected to be about 5 MHz), which is the repetition frequency of the G and B signals. Also,
There is a drawback that the power consumption of the amplifier 9 also increases due to the widening of the band.

In the sine drive type shown in Fig. 2, the demodulation circuit 11 outputs the luminance signal M from the video signal input to the terminal 1, and also outputs the 3.58MHz color subcarrier ωc and the carrier color signal ωc+θ, and separately outputs it from the terminal 3. A circuit 4 converts the given index signal into a write signal with a triplet frequency ωr, a first mixing circuit 12 calculates the frequency sum of the color subcarrier ωc and a triplet frequency ωr, and a second mixing circuit 13 converts the first write signal into a write signal with a triplet frequency ωr. The frequency of the output of the mixing circuit 12 and the carrier color signal ωc+θ is determined to obtain a write signal that is phase-modulated (ωr+θ) by the carrier color signal, and this write signal and the luminance signal M are added by the amplifier 14 and sent to the output terminal 10. It is applied to the electron gun of the guiding picture tube.

In this way, in the sine drive type, the luminance signal level and the phase-modulated write signal (ωr+θ) are mixed and output. That is, a triplet frequency signal phase modulated by θ is applied to the electron gun. For example, if the input video signal is a blue screen, the beam amount is controlled by a sine waveform that peaks at the timing of scanning the B phosphor among the R, G, and B phosphors, so the playback screen becomes a blue screen. In other words, in the sine drive type, the beam has a sine waveform, and colors are reproduced by changing the phase of the beam.

In this case, the amplifier 14 only passes the luminance signal, which is a continuous wave of approximately 0 to 4.5 MHz, and the sine wave signal of the triplet frequency (as mentioned above), so the amplifier 14 passes both of the above signals. A relatively narrow band covering about 0 to 5.2 MHz may be used. However, in this conventional example,
Since the method of demodulating and using the color signal is not adopted, and θ of the write signal ωr + θ is the phase itself of the color signal sent from the broadcasting station,
It is difficult to match the actual situation on the receiver side (for example, three primary color phosphor stripes are arranged in parallel at exactly 120° intervals), and therefore has the drawback of poor color reproducibility on the receiver.

(c) Purpose of the invention The present invention provides a beam index type color television receiver having a signal processing configuration that eliminates each of the above-mentioned drawbacks. In this method, the θ of ωc+θ in the write signal is created from the once demodulated three primary color signals to improve color reproducibility.

(d) Structure of the invention The present invention comprises a demodulating means for demodulating R, G, and B primary color signals from a video signal in a beam index type color television receiver, a means for outputting a luminance signal, and a means for outputting a luminance signal from the index signal. means for forming pulses with a triplet frequency corresponding to the arrangement period of the three primary color phosphors; means for forming the pulses with the triplet frequency into three pulse trains corresponding to three phases of +120°, 0°, and -120°; three switch means for individually gating the R, G, B primary color signals as outputs of the demodulation means by the pulse train; and a bandpass amplifier for a predetermined band including the luminance signal and the output of the bandpass amplifier are applied to the picture tube.

(E) Embodiment In FIG. 3 in which the present invention is implemented, 15 denotes a demodulation circuit that demodulates and outputs R, G, and B signals from the video signal supplied to the terminal 1, and a circuit that outputs the luminance signal M. This is a video signal processing circuit with 16 is a pulse forming circuit which forms the index signal applied to the terminal 3 into triplet frequency pulses.

17 is the triplet frequency pulse +
This is a three-phase pulse generation circuit that generates a pulse train group with phases of 120°, 0°, and -120°.

Reference numerals 18, 19, and 20 designate switch circuits that are controlled on and off by the output pulses of the three-phase pulse generation circuit, and pass the R, G, and B signals from the video processing circuit 15 in an on state.

A bandpass amplifier 21 is commonly connected to the outputs of the switch circuits 18, 19, and 20, and is set to have a passband of approximately ±1MHz centered around the triplet frequency (5.2MHz). Therefore, the R, G, and B rectangular wave signals output from the switch circuits 18, 19, and 20 are transmitted to the amplifier 21.
Since the band is limited by the frequency band, it cannot pass through as a rectangular wave, and only the fundamental wave (sine wave) component of the triplet frequency, which is the repetition frequency of R, G, and B, is passed through and amplified and output. At this time, this sine wave signal has a phase depending on the presence or absence of each of the R, G, and B signals, and is therefore equivalently similar to the write signal ωr + θ output from the mixing circuit 13 in FIG. Become.

This point will be explained in more detail by taking a specific operational model shown in FIG. 5 as an example. FIG. 5 shows an example in which yellow color is reproduced (displayed), and A in the figure represents the R, G, and B phosphor stripes of the picture tube. Since yellow is now being reproduced, the magnitudes of the R, G, and B signals output from the video signal processing circuit 15 are R=G=1 and B=0.

Therefore, the switch circuits 18, 19, 2 in FIG.
The primary color signal gated by 0 and input to the bandpass amplifier 21 is as shown in FIG. 5B. Since the passband of the band-pass amplifier 21 is set as described above, this primary color signal B cannot pass through as a rectangular wave, and only the fundamental wave component, which is the repetition frequency of this signal B, is passed and amplified. At this time, since the phase of the fundamental wave component is determined by the respective positions of the R and G signals, the signal output from the bandpass amplifier 21 becomes as shown in FIG. 5C.

In other words, this output signal C has a waveform like a triplet frequency sine wave signal phase-modulated so that the positive amplitudes corresponding to R and B of the phosphor stripe are exactly the same. This is the same signal as the write signal ωr+θ in the case of this operation model in the conventional example (FIG. 2) described above.

The output signal of the bandpass amplifier 21 thus outputted is applied together with the luminance signal M from the video signal processing circuit 15 to an amplifier circuit 22 having a passband similar to that of FIG. 1
It is applied from 0 to the electron gun of the picture tube.

Incidentally, the luminance signal M and the output signal of the bandpass amplifier 21 may be applied separately to the cathode and grid of the electron gun without being combined.

In the embodiment shown in FIG. 4, the color signal and the luminance signal M are thus applied to separate electrodes of the electron gun. Incidentally, FIG. 4 shows a process in which the pitch of the index element is 4/3 times the pitch of the three primary color phosphor stripes.

23 is a filter that waves the index signal applied from the terminal 3, and 24 is a pulse generator that pulses the index signal.

25 is a PLL type pulse shaping circuit which forms a pulse with a frequency 4i, which is four times the index frequency i, using the pulsed index signal as a reference signal, and generates pulses for the phase comparator 26, low-pass filter 27, and 4i. voltage controlled oscillator 2
8. It consists of a 1/4 frequency divider 29. 30 is
The input pulse of 4i is divided by 1/3 and +120°, 0°,
This is a three-phase pulse generation circuit that generates a pulse train of three phases at -120°. In this embodiment, the three-phase pulse generating circuit 30 also serves as a means for forming triplet frequency pulses. Reference numeral 31 denotes a synthesis circuit that synthesizes the R, G, and B signals demodulated by the video signal processing circuit 15 at an appropriate ratio to create a luminance signal M. 32 is a color signal amplifier, and 33 is a luminance signal amplifier. Output terminal 34 is connected to the grid of the picture tube, and output terminal 35 is connected to the cathode of the picture tube. Switch circuit 18, 19, 20
The bandpass amplifier 21 and the bandpass amplifier 21 are similar to those shown in FIG.

As described above, in each of the embodiments shown in FIGS. 3 and 4, the passband of the bandpass amplifier 21 is set to 5.2MHz±1MHz, and the passband of the amplifier circuit 22 in FIG. 3 is set to 0 to 5.2MHz. The passband of the color signal amplifier 32 in FIG.
1 and the pass band of the luminance signal amplifier 33 may be the luminance signal band (approximately 0 to 4.5 MHz), so in the end, both of these embodiments have a pass band of 0 to 15 MHz like the conventional example shown in FIG. Doesn't require a wideband amplifier.

In both of the above embodiments, R, G, and B signals obtained by demodulating the color signals sent from the broadcasting station are used.
Since the write signal for the sine drive is created from the signal, a write signal with a phase that matches the actual situation on the receiver side, such as the arrangement of the three primary color phosphor stripes of the picture tube, can be obtained.

(f) Effects of the invention As described above, according to the beam index type color television receiver of the invention, the bandpass amplifier for supplying color signals to the picture tube and the amplifier circuit provided at the subsequent stage have a wide band. Since there is no need to use the amplifiers, the circuit configuration of each amplifier is simplified and the power consumption thereof can be reduced. Furthermore, since it is possible to obtain a write signal that matches the actual situation on the receiver side more than the conventional sine drive method, it has the great advantage of improving color reproducibility on the receiver.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the main parts of a conventional beam index type color television receiver, and FIG. 2 is a block circuit diagram of another conventional example. FIG. 3 is a block circuit diagram showing the main parts of a beam index type color television receiver embodying the present invention. FIG. 4 is a block circuit diagram showing the main parts of another embodiment of the present invention. FIG. 5 is a diagram for explaining the operation of the embodiment shown in FIG. 15... Video signal processing circuit, 16... Pulse forming circuit, 17, 30... Three-phase pulse generation circuit, 1
8, 19, 20... switch circuit, 21... band pass amplifier.

Claims (1)

[Claim for Utility Model Registration] Three primary color phosphors of red, green, and blue repeatedly arranged in stripes on the inner surface of the face plate of a picture tube;
When an electron beam emitted from a single electron gun is swept over a surface having index elements repeatedly arranged in regular relation to these phosphors, the electron beam is controlled by using an index signal obtained from the index element. In a color television receiver in which light impinges on a predetermined phosphor, the receiver includes: demodulating means 15 for demodulating primary color signals of R, G, and B from a video signal; and means 15 and 3 for outputting a luminance signal from the video signal.
1, pulse train forming means 16, 25 for forming pulses at a triplet frequency corresponding to the array period of the three primary color phosphors from the index signal;
three-phase pulse forming means 17, 30 that converts the R, G, and B primary color signals as outputs of the demodulation means into three pulse trains corresponding to three phases of 0° and -120°; three switch means 18, 19, 20 that gate individually; a bandpass amplifier 21 whose input terminals are commonly connected to the outputs of the three switch means and whose predetermined band is centered around the triplet frequency; and amplifier circuits 22 and 3 that amplify the output of the bandpass amplifier and apply it to the picture tube.
A beam index type color television receiver comprising: 2,33.