JPS5828699B2 - color - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shadow mask type color picture tube equipped with a slot type shadow mask (hereinafter referred to as slot mask).

In this type of color picture tube, a moiré phenomenon occurs due to interference between the longitudinal slot joints of the slot mask and the scanning line of the electron beam.

This moiré phenomenon is a problem because it causes a deterioration in image quality.3 This moiré phenomenon is expressed by the number of beats of interference image 1 as shown in the following equation.

Here, B: Number of beats No.: Number of effective scanning lines α Overscan rate 1 m = Mask effective surface height Pv: Vertical pitch of mask The above formula (1) is taken as a column for 18-inch type, and the horizontal axis is the vertical mask pitch Pv, If the number of beats B is plotted on the vertical axis, it will look like FIG. 1.

In FIG. 1, the solid line indicates the NTSC system, which has 525 scanning lines and is used in Japan, the United States, etc., and the dotted line indicates the PAL system, which has 625 scanning lines and is used in Europe.

As is clear from the figure, the mask vertical pitch Pv at which the number of beats is the maximum Bmax''! or the minimum Bmin is as shown in the following table.

Table 1 Pv value (18-inch model) Looking at the relationship between the number of beats and moire, moire is most noticeable when the number of beats is O, and moire is least noticeable when the number of beats is maximum. It's time to become

In other words, in the NTSC system, when Pv=0.75, the PA
In the L system, moire is most noticeable when Pv = 0.94, and in the NTSC system, when Pv = 0.90, P
In the AL method, moire is least noticeable when Pv = 0.75.However, in the case of a slot mask, if the vertical pitch of the slot mask is selected so that the number of beats is maximum and moire is least noticeable, The reality is that very noticeable moiré appears, leading to a decline in image quality.

In particular, this phenomenon affects the resolution of color picture tubes, and the recent trend toward higher resolution of color picture tubes has shown unfavorable results with respect to moiré.

By the way, in the vicinity of the beat number O, where moire is least noticeable, several moire can be seen in the shape of tree rings.

However, this tree-ring-like moiré may disappear temporarily depending on the condition of the TV receiver, but when the tree-ring-like moiré appears, the drop in image quality is more significant than when the number of beats is at its maximum. It is normal not to use it.

It has been a challenge in the past to find a way to reduce the annual ring-like moiré, which causes a significant deterioration in image quality, and to make it less noticeable.

The present invention was made in view of the above problems, and an object of the present invention is to provide a color picture tube that can reduce moiré and obtain excellent image quality.

Embodiments of the present invention will be described below based on the drawings.

In Fig. 2, G is the effective surface of the slot mask, the hatched area 2 is the slot row with the vertical pitch Pvl of the slot mask such that the number of beats of 1 is O, and the blank area 3 is the slot row that interferes and is the number of beats of 1. The slot row portions of the vertical pitch Pv2 where the number of beats is the maximum are shown respectively.

In this way, slot mask 1 has two vertical pitches P v
1 n P v 2 are provided alternately in units of a plurality of slot rows.

By alternately providing vertical pitches where the number of heats is maximum and vertical pitches where the number of beats is 0, the advantages of both can be utilized.

In other words, even if a tree-ring-like moire occurs, the tree-ring-like moire is erased in the blank area 3 shown in FIG.
Moiré becomes less noticeable on the screen as a whole.

It is preferable to select a range of 5 to 20 slot rows as a unit of the plurality of slot rows to which the same vertical pitch is applied.

In the case of 1 to 2 columns, a moiré different from that calculated by the above formula (1) occurs, which does not lead to improvement in image quality.

Moreover, when there are 20 or more columns, moiré, which is calculated using equation (1) within each unit, becomes noticeable, and it may not be possible to improve the image quality as well.

Furthermore, as is clear from Figure 1 and Table 1, the vertical pitch of the NTSCJ system where the number of beats is the maximum Bmax is almost the same as the vertical pitch of the PAL system where the number of beats is the minimum Bmin, and the NTSCJ system where the number of beats is the minimum Bmin. The vertical pitch of the system and the vertical pitch of the PAL system, which is Bmax, are almost the same.

Therefore, by alternating the vertical pitch for the maximum number of beats and the vertical pitch for the minimum number of beats as described above,
It becomes possible to share slot masks between the NTSC system and the PAL system.

As is clear from the above explanation, according to the present invention, there are two different
By alternately providing the two vertical pitches, moiré becomes less noticeable, excellent image quality can be obtained, and slot masks that can be pressed in different ways can be shared.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the number of beats of an 18-inch color picture tube and the vertical pitch of the mask, and FIG. 2 is an explanatory diagram showing a slot mask according to the present invention. B...Number of beats, Pv...Vertical pitch,
1... Slot mask, 2, 3... Slot rows with different vertical pitches.

Claims (1)

[Claims] 1. Press a button on a shadow mask type color picture tube equipped with a slot mask, and set the vertical pitch of the slot mask such that the number of beats of the slot mask becomes 0 due to interference, using multiple slot rows as a unit within the slot mask. A color picture tube equipped with a slot mask in which the vertical pitch of the slot mask is alternately provided so as to maximize the number of beats.