JPS6232873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for generating an index signal in a beam index type color television.

In general, the picture tube of a beam index type color television has three primary color phosphor stripes 21 of red, green and blue on the inner surface of a face plate 16, as shown in FIG.
22 and 23 are repeatedly applied to form a fluorescent surface 2, and index fluorescent light is applied at pitches having a certain relationship with the pitches of a set of three primary color phosphor strips (referred to as 1 triplet) on the fluorescent surface 2. Body stria 3 has been applied.

When this fluorescent surface 2 is scanned with a single electron beam 15, the index fluorescent body 3 is stimulated to emit light, and this emitted light 31 is detected by a photodetector to obtain an index signal. Using this index signal, the accurate scanning position of the single electron beam on the fluorescent surface is detected, and this signal is used to switch the three primary color signals and supply them to the electron gun, thereby reproducing a normal color image.

Conventionally, as a method of arranging index phosphor strips 3, a method has been proposed in which one index phosphor strip 3 is provided for each triplet of three primary color phosphor strips, as shown in FIG. If such an arrangement method is adopted, the index phosphor strip 3 can be formed in the same mask pattern as the three primary color phosphor strips, and the alignment of the index phosphor strip 3 is extremely easy.
During color reproduction, the beam amount of the electron beam is modulated at a frequency corresponding to the triplet pitch, which distorts the index signal and causes a phase error, causing cross modulation that makes proper color reproduction difficult. There is.

The cause of this cross modulation is considered to be as follows.

The color signal V applied to the picture tube is generally expressed by the following equation, where V _M is a volatility signal, V _C is a color saturation signal, ω is a frequency for color generation, and φ is a color phase signal.

V=V _M +V _C cos (ωt+φ) ...Next, when the phosphor surface 2 is scanned with an electron beam with a constant beam amount, the pulse signal I generated from the index phosphor strip 3 is approximately It is expressed by the following Fourier expansion formula.

I=a ₁ +a ₁ cosωt+a ₂ cos2ωt+a ₃ cos3ωt+…
...... Coefficients a ₀ , a ₁ , a ₂ ... are index phosphor strip 3
This is a constant determined by the width of the stripe, the stripe pitch, etc.

Therefore, the signal emitted from the index phosphor strip 3 during color signal reproduction is proportional to the product of Eq.

V・I=a ₀ V _M +a ₀ V _C cos(ωt+φ)+a ₁ V _M cosωt+a ₂ V _M cos2ωt +a ₁ V _C cosωt・cos(ωt+φ)+... In the formula, the fundamental wave component of angular frequency ω When extracting and using this as an index signal, the following equation is obtained from the equation.

(V・I) ω=a ₀ V _C cos(ωt+φ)+a ₁ V _M cosωt =√( _{0 C} + _{1 M} ) ² +( _{0 C} ) ² cos(ωt−δ) ……… δ=arctan(− a ₀ V _C sinφ/a ₀ V _C cosφ+
a ₁ V _M )...... From the above equation, it can be seen that the index signal includes a phase error δ which is a function of the color saturation signal V _C , the luminance signal V _M and the color phase signal φ. . In particular, depending on the change in the phase signal φ, δ
As a result, a phase error occurs in the index signal, which is the main cause of cross modulation.

To address the above problem, the relationship between the pitch of one triplet of the three primary color phosphor strips and a non-integer multiple, for example, as shown in FIG. A picture tube has been proposed in which cross modulation does not occur by providing three tubes.

In this picture tube, the above equations and equations can be rewritten as follows.

I=b ₀ +b ₁ cos3/2ωt+b ₂ cos3ωt+…… V・I=b ₀ V _M +b ₀ V _C cos(ωt+φ)+b ₁ V _M cos3/2ωt+b ₂ V _M cos3ωt +b ₁ V _C cos3/2ωt・cos(ωt+φ)+... ...... However, b ₀ , b ₁ ... are constants.

In the formula, when the frequency component of angular frequency 3/2ω is used as an index signal, we obtain (V·I) _3/2 = a ₁ V _M cos3/2ωt . It can be seen that the equation does not include the phase error δ in the above equation, and that an index signal without cross modulation can be obtained.
However, in the case of the picture tube described above, the index phosphor strip 3 does not have a fixed positional relationship with the phosphor strip of a specific color, so it is difficult to know which color phosphor the beam is currently scanning. cannot be identified from the index signal.

For this identification, at the beginning of the horizontal scan of the beam,
One of the three primary color phosphor strips, so-called "run-in"
It becomes necessary to provide two or more index phosphor strips 32, 32 having an integral multiple relationship with the triplet pitch, and this results in a portion where the image is not reproduced at the edge of the screen (for example, in the case of a 20-inch picture tube, Approximately 2 to 3 cm). Furthermore, when the black level drops and the generation of the index signal once stops, color synchronization is lost, and even if the index signal is restored, proper color reproduction is no longer possible. Therefore, it is necessary to constantly emit an electron beam to generate an index signal, and it is not possible to obtain good image contrast with this method. Furthermore, since the pitch of the index phosphor 3 is a non-integer multiple of the pitch of one triplet of the three primary color phosphor strips, the index phosphor 3 cannot be formed with the same mask pattern as the three primary color phosphors. When different mask patterns are used, it is extremely difficult to align the patterns, causing color misregistration during color reproduction.

The present invention solves the above problems at once by scanning an electron beam by modulating it with a high frequency signal having a frequency Ω sufficiently higher than the angular frequency ω corresponding to one triplet pitch. An object of the present invention is to provide a method for generating an index signal in which no cross modulation occurs even when the pixels are arranged at the same pitch or an integral multiple of the bits of one triplet of the three primary color phosphor strips.

A beam index type color television embodying the present invention has a receiving device 9 as shown in FIG.
A luminance signal 72 and a color generation signal 73 are taken out from the video signal received by the system, and after the signals are subjected to signal processing to be described later, they are applied to the index picture tube 1 to reproduce a color image.

The index picture tube 1 has substantially the same structure as the conventional one, and a single electron beam 15 is emitted from one electron gun 14 disposed in the network 11, and this beam 15 is swung to strike the inner surface of the face plate 16. The formed fluorescent surface 2 is scanned.

As shown in FIG. 2, the fluorescent surface 2 is made by repeatedly applying three primary color phosphor strips 21, 22, and 23 of red, green, and blue.
A non-luminescent material 24 made of graphite or the like is interposed between adjacent phosphor strips. An aluminum metal bag 25 is uniformly deposited on the fluorescent surface 2.
Index phosphor strip 3 on metal back 25
is applied in stripes over the entire scanning surface. The index phosphor strips 3 are provided at a pitch equal to or an integral multiple of the pitch of one triplet of the three primary color phosphor strips 21, 22, 23. In the illustrated example, the arrangement pitch of the index phosphors 3 is made to match one triplet pitch of the three primary color phosphor strips, and each index phosphor strip 3 is aligned with the red phosphor strip 2.
1 and the green phosphor strip 22. A photodetector 4 such as a photomultiplier tube is provided in the funnel section 17, and the photodetector 4 detects a signal from the index phosphor 3, and sends this signal to an index signal processing section 5, which will be described later. Therefore, the frequency (ω) corresponding to the pitch of the index phosphor stripes
The index signal is obtained, and the signal is further converted into a converter
is applied to the grid electrode 13 of the electron gun 14 in place of the carrier signal (ω ₀ ) in the color generation signal.

In the present invention, in addition to the luminance signal 72 and the color generation signal 73, the electron beam 15 emitted from the electron gun 14 is further modulated with a high frequency signal having a sufficiently high angular frequency Ω and scanned. This is to generate a frequency component signal that does not include a phase error in the signal 31 generated from the oscilloscope.

That is, a high frequency signal with an angular frequency Ω is generated by the signal generator 6, this signal is added to the color signal V using the mixer 61, and the signal expressed by the following or formula is mixed and adjusted, and this signal is sent to the electron gun. 14.

V'=V _M cosΩt+V _C cos(ωt+φ) ...... V'=V _M +V _RF cosΩt+V _C cos(ωt+φ)
...... However, V _RF is the amplitude of the high frequency signal.

Since the pitch of the index phosphor strip 3 is the same as the triplet pitch of the three primary color phosphor strips, the signal I generated when the phosphor surface 2 is scanned with a fixed amount of electron beam is I=a ₀ +a ₁ cosωt+a ₂ cos2ωt+a ₃ cos3ωt+…
...... It is the same as the above formula.

Therefore, the signal emitted from the index phosphor strip 3 during color image reproduction is proportional to the product of Eq.

V'・I=a ₀ V _M cosΩt+1/2a ₁ V _M {cos(Ω+ω)t+cos(Ω-ω)t}+1/2V _M a ₂ {cos(Ω+2ω)t +cos(Ω-2ω)t}+1/ 2a ₃ V _M cos(Ω+3ω)t+cos(Ω-3ω)t+a ₀ V _C cos(ωt+φ) +1/2a ₂ V _C cos(3ωt+φ)+cos(-ωt+φ)+1/2a ₁ V _C {cos(2ωt+φ)+cosφ} +1/2a ₃ V _C {cos(4ωt+φ)+cos(-2ωt+φ)}+... ...... The above formula includes an angular frequency ω equivalent to the pitch of the index phosphor strip 3, and a color phase signal φ. This indicates that there are many frequency components that are not included. Such frequency components are listed below.

Therefore, among the above frequency components, for example, (V′・
I) A filter circuit 51 extracts a signal related to Ω _- 〓, and a mixer 52 adds a signal of angular frequency Ω to the angular frequency component to cancel the Ω component, thereby creating an index related only to the angular frequency ω. I get a signal.

Note that when implementing the present invention, the frequency of the high-frequency signal for modulation is determined in consideration of the following points.

1. Since the image is disturbed by high-frequency signals, set the frequency to be sufficiently higher than the frequency of the luminance signal and color generation signal so that this is not visually observed.

2 When using P45, which generates ultraviolet rays, as the index phosphor 3, the frequency of the electron beam for generating ultraviolet rays is limited to 20MHz;
It does not respond to electron beams with higher frequencies.

Therefore, taking into account the response of the phosphor to the electron beam, the frequency is set to 20 MHz or less. Considering the above points, when using the signal at (V'・I)Ω _- 〓, which has the largest amplitude in the above equation, the frequency of the high-frequency signal should be
It is recommended to select 15MHz.

In the case of a 20-inch receiver, the frequency ω/2π is approximately 10MHz, so it becomes Ω−ω/2π5MHz, and this frequency is located between the luminance signal and the color generation signal, and is convenient for selection by the filter 51. It is.

As described above, the present invention modulates the beam amount of the single electron beam 15 with a high frequency signal, regardless of the arrangement of the index phosphor strips 3.
An index signal containing no phase error can be obtained, and cross modulation can be reliably prevented from occurring.

In addition, the arrangement pitch of the index phosphor strips 3 is
Since the pitch can be set to be the same as or an integral multiple of the pitch of one triplet of the three primary color phosphor strips, there is no need to separately provide an index phosphor called a "run-in", and it is possible to reproduce colors appropriately and achieve good contrast. It has many excellent effects, such as being able to obtain an image, and furthermore, the index phosphor strip 3 can be formed with the same mask pattern as the three primary color phosphor strips, making alignment easy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an index type color television embodying the present invention, and FIGS. 2 and 3 are enlarged sectional views showing the arrangement of index phosphor strips. 21, 22, 23... Three primary color phosphor stripes, 3...
Index phosphor strip, 6... High frequency generation section.

Claims (1)

[Scope of Claims] 1. An index signal is generated by scanning a phosphor surface coated with an index phosphor strip with a single electron beam at a pitch of one triplet of three primary color phosphor strips or a pitch having a relationship of an integral multiple thereof. In a beam index type color television that obtains the beam intensity of the single electron beam, a high frequency signal (Ω) having a frequency (Ω) higher than the frequencies of the luminance signal and the color generation signal but at which the response of the phosphor can be obtained is used. By scanning the phosphor surface with the modulated beam, the frequency (ω) associated with the pitch of the index phosphor strip and the A beam characterized in that after extracting a signal at a frequency related only to the frequency (Ω) of the high-frequency signal, a signal at a frequency (ω) corresponding to the pitch of the index phosphor strip is frequency-separated to obtain an index signal. A method for generating index signals in index type color television. 2 The signal extracted when scanning the phosphor surface with a single electron beam has a frequency (ω) corresponding to the pitch of the index phosphor strip and a frequency (Ω) of the high-frequency signal.
A method for generating an index signal in a beam index type color television as set forth in claim 1, wherein the signal has a frequency (Ω-ω) that is the difference between the index signal and the index signal. 3. The index signal generation method in a beam index type color television set according to claim 2, wherein the frequency (Ω) of the high frequency signal is approximately 15 MHz.