JPS584425B2 - color cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam perforation pattern in a shadow mask of a shadow mask type color cathode ray tube.

Recently, in shadow mask type color cathode ray tubes, the shape of the electron beam aperture 1 is not circular but rectangular in increasing numbers.

This is because the deflection device can be greatly simplified when used together with three horizontally arranged red, green, and blue electron guns and a vertically elongated band-shaped phosphor.

In a color cathode ray tube using such a rectangular electron beam aperture shadow mask, the occurrence of moiré is a serious problem.

As shown in Fig. 1, the electron beam hole pitch is set to P1.
1 The vertical deviation between adjacent electron beam aperture rows is △y
The scanning line pitch is expressed as Pl.

PM is the pitch of moiré generated between the nth harmonic of the vertical transmission waveform of the electron beam aperture row and the mth harmonic of the vertical brightness waveform of the scanning line, and PM is the phase difference between the moire waves due to adjacent throughhole rows. If φU is expressed as MM, and the luminance modulation degree of the moiré wave is expressed as MM, these are as follows (Patent Application No. 10898-1982)
(See No. 9).

A here.

is the magnitude of the DC component when the vertical brightness waveform of the scanning line is expressed in a Fourier series, and Am is the mth harmonic amplitude.

Similarly B. is the DC component of the electron beam transmission waveform through the aperture array, and Bn represents the n-th harmonic amplitude.

Among the above equations, the smaller the MM of equation (3), the less conspicuous the moire, but this cannot be changed arbitrarily because it depends on the spot brightness distribution and the width b of the bridge in FIG.

In other words, if the spot diameter is set to dog, MM becomes smaller, but
The direction of cathode ray tube development is to make this as small as possible to achieve sharp focus, and if b is also made smaller, MM will be smaller, but from the viewpoint of maintaining the mechanical strength of the mask, it will be significantly better than the current one. It cannot be made smaller.

Therefore, what can be freely manipulated is P in equation (1) and (2)
This is φ in the equation.

The smaller the PM, the less noticeable the moire will be.

Further, by keeping φ at 1800, that is, π, the moire pattern as a whole becomes less noticeable.

For this purpose, k is k(n If it is an odd number, And it is sufficient.

The above is a case where n and m are fixed to one type, but in reality, it is often necessary to consider several different types of n and m depending on the value of PY.

Also, if one type of shadow mask pattern can be used for multiple broadcasting systems instead of one broadcasting system, it will have a large cost reduction effect by simplifying the process, but this also requires the use of several different types of shadow mask patterns. and m must be considered.

For this reason, inventions using multiple △y by the same inventor (
Japanese Patent Application No. 108989/1982 was filed earlier, but there was a problem in that even if Δy was the same, the moiré reduction effect differed depending on the arrangement.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a shadow mask pattern that has a good moiré reduction effect for both the NTSC system and the PAL system.

In order to achieve the above purpose, first of all, both broadcasting methods (1
) It is necessary to provide a PY that reduces PM in the equation, and then determine a mask pattern that obtains a moiré phase difference φ that makes the moiré pattern less noticeable.

Moiré needs to be inconspicuous not only in the scanning lines of one frame, but also in half of the scanning lines per field, assuming that interlace is incomplete.

Taking these points into consideration, FIG. 2 shows the relationship of moiré pitch to frame and field scanning lines when the PY is changed between the NTSC and PAL systems.

The figure shows moiré pitch and P by various combinations of n and m.
The relationship with Y is also listed.

The values on the vertical and horizontal axes of the figure are for PM and Py to be discussed independently of the cathode ray tube size.
It is expressed as a standard using the scanning line pitch of the C method.

In order to make moire less noticeable in the NTSC and PAL systems, it is necessary to select Py that corresponds to the valleys of all the curves in the figure.

At this time, the allowable upper limit PM is different for the field and the frame, and as stated in the specification table of Tokusei No. 50-108989, for the frame, PM<7PNTSC...(5), and for the field, pM<14PNTSC. ...(6) can be used as a guide.

Furthermore, when Py is selected to a certain value, it is necessary to make the moiré pattern as a whole less noticeable by selecting △y that makes it less noticeable for the combination of n and m where the PM is relatively small. be.

In order to set such an appropriate value of △y, the magnitude relationship of the curves in Fig. 2,
In other words, it is necessary that the order of the PM values is not changed.

In Figure 2, the value range of Py that satisfies these conditions is the area surrounded by line segments 苧 and 4, that is, the value of PY is 1.43PNTSC≦Py≦1,5PNTsc (7
) is the interval.

In this section, PM is in the order of curves 5, 6, 7, 8, 9, and 100.
is large and there are some points that are equal, but this order will never change.

Furthermore, the conditions of equations (5) and (6) are also satisfied.

n corresponding to the magnitude of Moirevich PM in this section
The values are summarized in Table 1.

As can be seen from Table 1, in this case, n is 1 for △y.
and 2 should be selected to simultaneously make the moire pattern less noticeable.

In this case, a pattern configuration that satisfies this condition with one value of △y (see Japanese Patent Application No. 50-99534) or two to
A configuration satisfying three types (see Japanese Patent Application No. 50-108989) is conceivable, but in the present invention, the optimum pattern is constructed by using a ship as the moiré evaluation function described below. Let it represent the half width of a moiré wave 120 generated by the electron beam aperture array and the scanning line.

The vertical luminance waveform of moire generated in each electron beam aperture row is represented by C1, C2, C, , C4, . . . .

Here, the intensity of the moire fringes generated in the direction of the angle θ from the horizontal axis is the sum of the projected images Ci' of the moire waveforms Ci of the individual electron beam aperture rows projected onto the Z axis perpendicular to the axis of the angle θ. It is expressed as

The phase of the moiré luminance waveform in the i-th column with one point P on the vertical coordinate axis as the origin is represented by φi, and the phase of the waveform Ci' with one point P' on the Z axis as the origin is φθi, the composite moire waveform in the θ direction. When expressed in Ω(z, θ), it is as follows.

Here, ω and θ in equation (8) are ωMθ=2πμMθ...(
9).

In this way, the amplitude of the composite moire waveform Ω(ZSθ) depends on the phase φi or φθi in addition to the amplitude MM of each individual moire wave.

Here, there is a relationship between φi and φθi as shown in the following equation.

φ61=C(i-1)pxtanθ-φt] COBθ・
...-(11) Once the pitch PMθ and the amplitude and angle θ of Ω(ztθ) of the composite moiré waveform are determined in this way,
The spatial frequency characteristics of vision at a viewing distance of 2H shown in FIG. 4 (where H is the vertical height of the screen).

) and the curve of visual response reduction due to visual space anisotropy shown in FIG. 5, it can be estimated how visible the moiré pattern is in the angle θ direction.

If PMθ is now expressed in units of u, then there is the following relationship between f on the horizontal axis in FIG. 4 and PMθ.

Here, f is a spatial frequency converted to a video signal frequency in a 20-inch color cathode ray tube.

If the moiré evaluation function weighted by the visual response is expressed as W (of), this is the visual spatial frequency characteristic R(f) and the visual response E in the angle θ direction.
(m) and Ω(z1θ) as shown in the following equation.

In addition, the index (■M) indicating the degree to which moire is conspicuous as a whole in the pattern was taken as an amount.

The present invention will be described in detail below with reference to examples.

A shadow mask pattern as a first example is shown in FIG.

Moiré phase difference φM due to adjacent electron beam aperture rows is 180
In order to keep Py and △y at 0, the relationship shown in equation (4) is required, but as stated in the patent application "Japanese Patent Application No. 1983-99534" filed by the same inventor and applicant, φu is 180.
φM where the response of the visual system changes by 3 dB from the case of 0
If the value of Δy is the range in which the moiré reduction effect is recognized, the corresponding range of Δy can be determined by the following equation.

Converting this to the range of φM results in the following.

117° x axis M x 243° (10) The mask pattern in Fig. 6 is composed of and.

If the upward shift of △y is expressed as + and the downward shift of △y is expressed as 1, then △y1, △y2e△y3s - △y1s - △y2t
-Δy3 array.

As can be seen from equation (15), in this case, △y1:n=1 Δy2pΔy3: n=1, n=2 Then, φu falls within the range of equation (16).

That is, measures are taken to reduce moiré by setting the ratio of n=1 to 3 and n=2 to 2.

As shown in Table 1, the moiré shown by the curve 10 with the maximum moiré pitch in the PY region of n=1, m=1,
In other words, it occurs between the fundamental waveform of the field scanning line of the PAL system and the fundamental waveform of the electron beam through-hole array transmission waveform.
The weight of n=1 is increased relative to n=2 with the aim of reducing this problem intensively.

Moiré evaluation functions for this pattern with n=1 and n=2 are shown in FIGS. 1 and 8.

As seen in FIG. 1, the combined amplitude of moiré when n=1 is very small.

FIGS. 1 and 8 show the magnitude of the moire composite amplitude for θ=0 to 180°, standardized with MM=1.00.

In addition, in order to show the pattern effect independently of PM, (10
) is the result when PM is fixed at 10 mm.

As shown in Fig. 8, when n=2, n=
Reflecting the weights of 1 and n=2, the amplitude of the oblique moiré is slightly larger than that of n=1.

However, it shows the degree of reduction in moire from n=1 to 5 (
The moiré evaluation index IM of formula 14) is 0.0698, which is the smallest among this type of pattern.

In the second embodiment, as shown in FIG. 9, if the upward deviation of △y is expressed by + and the downward deviation is expressed by 1, then 10 △y1s + △y2, 10△y3m - △y1m-
The array is Δy2m−Δy3.

As shown in Figure 2, this pattern is expressed by the equation (7).
In the Y area, the moiré pitch of n=2 in the PAL system shown by curve 1 is the maximum in frame scanning, and in the pattern of Example 1, this becomes a diagonal moiré pattern as shown in FIG. It is aimed at eliminating it.

The moiré evaluation function W (of) for n=1 and n=2 is shown in Figure 10.
As shown in FIG. 11, when n=1, there is almost no difference from the first embodiment, but when n=2, it can be seen that there are not only diagonal but also horizontal components.

By scattering the moire patterns in the diagonal or horizontal direction in this way, a single moire pattern in the diagonal or horizontal direction cannot be seen, and this effect is actually noticeable.

The moiré evaluation index IM of this pattern is 0.101.

As explained above, according to the present invention, by complementary combining the moire reduction effect by reducing PM and the moire reduction effect by appropriately determining φU, both the NTSC system and the PAL system can be used. Moiré can be made less noticeable.

A pattern in which the moiré reduction weight is the same for both n=1 and n=2 is known (Kokoku Publication No. 48-32596), but the moire evaluation function of this pattern is shown in Figs. 12 and 13. As shown, oblique moire is particularly noticeable when n=2, and the moire evaluation index ■M is also large at 0.114.

In this way, we not only consider the moire reduction effect due to △y and even φya, but also reduce moire in areas where moire can be reduced by reducing PM by selecting PY. It is not possible to reduce moire for multiple broadcasting systems unless careful consideration is given to reducing moire by focusing on optimizing φ.

[Brief explanation of drawings]

Figure 1 is a structural diagram showing electron beam holes in a shadow mask, Figure 2 is a characteristic diagram showing the relationship between electron beam hole pitch and moiré pit, and Figure 3 is the relationship between individual moire waveforms and composite moire waveform. FIG. 4 is a characteristic diagram showing visual spatial frequency characteristics, and FIG. 5 is a characteristic diagram showing visual response anisotropy. FIG. 6 is a structural diagram showing a shadow mask pattern as an embodiment of the present invention, FIGS. 7 and 8 are characteristic diagrams showing a moiré evaluation function in this embodiment, and FIG. A structural diagram of the shadow mask pattern of the example, FIG.
FIG. 11 is a characteristic diagram showing a moiré evaluation function for this pattern. Further, FIGS. 12 and 13 are characteristic diagrams showing moiré evaluation functions for known examples for comparison. 1: Through hole row center line, 2: Shadow mask, 11: Through hole.

Claims (1)

[Claims] 1. A large number of rows of holes arranged at a constant pitch of holes Py,
In a shadow mask in which the through holes are arranged slightly offset from each other, the scanning line pitch on this shadow mask when this shadow mask is used in the NTSC system is PN.
When TSC is (1) 1.43≦Py/pNrsc≦
1.50 (2) The through hole position deviation △y of adjacent through hole rows is △
y1, △y2, △y3. −△y1, one △y2, one △y3
A color cathode ray tube equipped with a shadow mask that repeats PY and Δy. 2 A large number of through-hole rows arranged with a constant through-hole pitch Py,
In a shadow mask in which the positions of the through holes are arranged slightly shifted from each other, when this shadow mask is used in the NTSC system, and the scanning line pitch on this shadow mask is PNTSC, (1) 1.43≦PY/ PNTS
C≦1.50 (2) Through-hole position deviation △y of adjacent through-hole rows
△y1s△y2p△y39−Δ3'1s−Δy2j−
A color cathode ray tube equipped with a shadow mask that repeats Δy3 and has Py, Δy.