JPH04186972A - Color image receiving device - Google Patents

Abstract

PURPOSE:To suppress the generation of Moire fringes in a state that sufficient luminance remains held by scanning an electronic beam at a speed of two folds of an image sending side, when a television image is received, and shifting a position of a scanning line of a first field and a scanning line of a second field by 1/2 of a scanning line interval of each field. CONSTITUTION:A first field and a second field are constituted of 262.5 pieces of scanning lines, respectively, and they are scanned without being superposed to each other, and as a result, the total number of scanning lines becomes 525 pieces. Scanning of 525 pieces is executed during 1/60 second in which a first field is sent, and scanning of 525 pieces is executed by shifting it a little during the next 1/60 second in which a second field is sent. As a result, the total number of scanning lines becomes 1050 pieces of two folds. Scanning of two folds of an image sending side is executed by each field, and as for an image signal corresponding thereto, it is allowable to apply the same signal to two pieces of continuous scanning lines, and also, it is allowable to apply it by synthesizing it with a signal of a field before one or more by using an image memory device.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a color image receiving device using a color picture tube having a shadow mask, and particularly relates to a color image receiving device in which moire fringes are reduced. .

(Prior Art) As is well known, shadow mask type color picture tubes have red and green shadow masks for color selection.

It is placed near a phosphor screen made of a phosphor layer that emits light in three colors of blue, and its shadow mask has a large number of circular or substantially rectangular holes. In recent years, circular through holes have been mainly used for industrial applications such as computer terminals, and rectangular through holes have been used in almost all home televisions. This is because rectangular through holes have advantages such as brighter brightness.

That is, as shown in FIG. 2, the rectangular through holes (2) are regularly arranged so that the long side direction coincides with the vertical direction of the screen. The spaces between the vertical holes are called bridges (2), which function to maintain the strength of the shadow mask, and these bridges are also arranged regularly. On the other hand, since the electron beam also constitutes regular scanning lines, these two regular patterns interfere with each other, resulting in unsightly bright and dark stripes, so-called moire fringes, appearing on the phosphor screen.

As long as there are bridges, it is impossible to completely eliminate these moiré fringes, but if the vertical spacing of the bridges is appropriately selected depending on the number of scanning lines in NTSC, PAL, etc., it can be suppressed to a level that does not pose a practical problem. be able to.

Recently, high-definition television (hereinafter referred to as HDTV), which has a much larger number of scanning lines than conventional broadcasting systems, has been developed.
Japanese HDTVs, which are being put into practical use, have a total number of scanning lines of 1.
The number of lines is 125, which is more than twice the number of 525 lines in the conventional NTSC system. Future color image receiving devices will need to receive both conventional and HDTV images, and the device must be designed so that moiré fringes are not noticeable regardless of the number of scanning lines.

For example, aspect ratio for a 32-inch HDTV:
9 If we consider specific numerical values for this color picture tube, we get the following: 0 The vertical size of the effective screen area is 372.
．． 6) However, the video amplitude is normally set as large as 8% to avoid screen breakage.

During HDTV image reception, the total number of scanning lines is 1125, but since 90 are used during the vertical retrace period, the number becomes 1035, and the scanning line interval is 0.39 (■).On the other hand, in NTSC image reception Sometimes the total number of scan lines is 525
Although it is a book, 40 lines are used during the vertical blanking period, so there are 485 lines, and the scanning line interval is 372.6 x 1.08 to 0.83 (m). It can be obtained by multiplying the line by the brightness function resulting from the force V. Calculating the relationship between the vertical pitch of the two holes, the pitch of the moiré fringes, and the contrast is as shown in FIG. 3 when the number of scanning lines is 1125, and as shown in FIG. 4 when the number of scanning lines is 525. Third
．． In FIG. 4, the horizontal axis shows the through-hole pitch (■), the vertical axis shows the moiré pitch (mm 2 ), and the moiré contrast. The larger the moire pitch, the more visible the moire stripes will be.
The greater the contrast, the more noticeable it is. Looking at Figure 3, in HDTV, both the moire pitch (shown by the solid line) and the contrast (shown by the broken line) are small and good when the vertical hole pitch is 0.6 m or less, and the contrast is good when the vertical hole pitch is 1.0 m or more. Although it is somewhat large, the moiré pitch is small at about 1 intestine, which is relatively good. Also, looking at Figure 4, we see that NT
In SC, the vertical pitch of the through hole is 0.6- or less, which is good.
On the larger side, when the vertical pitch of the holes is about 1, the moire pitch is minimal, but it is about 2-2, and the contrast is strong, making it easy to notice moire fringes.

(Problem to be solved by the invention) The larger the vertical pitch of the perforation, the fewer the number of bridges per unit length, which naturally results in a brighter screen. If you choose a vertical through hole pitch so that the stripes are not noticeable, the pitch will be 0.61 or less,
HDTV with dim brightness and unimpressive screen
Improvements in this respect were strongly desired.

[Structure of the invention]

(l [Means for Solving the Problem]) This invention was made in view of the above problems, and in order to suppress the occurrence of moiré fringes without reducing the brightness of the color picture tube, it is necessary to When receiving a total of 525 or 625 television images, the electron beam is scanned at twice the speed of the image sending side, and the first
This is a color image receiving device in which the positions of the scanning lines of a field and the scanning lines of the second field are shifted by 172, which is the scanning line interval of each field.

(Function) With this slight shift, the frame created by combining the first and second fields becomes 1050 lines, twice the original number of scanning lines in the case of NTSC, and as explained in detail below, the frame created is 1050 lines. It is possible to suppress the occurrence of moire fringes while maintaining brightness.

(Example) In the NTSC signal, the first field is sent in 1/60 seconds, and the second field is sent in the next 1760 seconds, and the sum of these two fields, 1/30 seconds, constitutes one frame. As is well known. The first field and the second field each consist of 262.5 scan lines, but they are scanned without overlapping each other, resulting in a total number of scan lines of 525. Currently, some image receivers scan the electron beam at twice the speed of the transmitting side, 1/6
The system uses a method that creates 525 scanning lines in 0 seconds. However, in that case, the positions of the scanning lines created in each l/60 second are the same, and the total number of scanning lines is 525.

In contrast, in the present invention, as shown in Fig. 1, 525 scans are performed in 1760 seconds after the first field is sent, and the scans are slightly shifted in the next 1/60 seconds when the second field is sent. 525 lines are scanned.

As a result, the total number of scanning lines is doubled to 1050 lines.

In each field, scanning is performed twice as much as on the image sending side, but the corresponding image signal may be applied to two consecutive scanning lines, or an image memory device may be used to provide one or more previous scanning lines. It may be combined with the signal of the field and given.

FIG. 5 shows the results of calculating the moire pitch and contrast when the number of scanning lines is 1050. It shows that even if the vertical pitch of the through holes is 1.21 or more, the moire pitch is 1 square or less. It is clear from FIG. 3 that good image quality with inconspicuous moiré fringes can be obtained even during HDTV reception. A comparison of the difference in screen brightness when the vertical pitch of the holes is 1.2 square meters and 0.6 meters is as follows. The ratio of brightness is equal to the ratio of the percentage occupied by the through holes. The width of the bridge is reduced to the limit regardless of the vertical pitch, and the width is approximately 0.1
There are five intestines. Therefore, the brightness ratio is 17% brighter with a vertical pitch of 1.2 m.

〔Effect of the invention〕

As described above, by doubling the number of scanning lines when receiving conventional broadcasting, the vertical pitch of the through-holes in the flat mask can be increased, brightness is brighter, and color images with less noticeable moire fringes can be received. equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the positional relationship of scanning lines according to the present invention. Figure 2 is a schematic diagram of a shadow mask with rectangular holes, and Figures 3, 4, and 5 show the vertical pitch of the holes when the number of scanning lines is 1125, 525, and 1050, respectively. FIG. 3 is a diagram showing the relationship between moire pitch and moire contrast. 1... Clear hole 2... Bridge agent Patent attorney Nori Chika Ken Double amount Take Hana Kikuo Diagram 1 Inquiry Lfjl125+ Diagram 3 mh ghi: y (mm)

Claims (1)

[Claims] When receiving a television image with a total number of scanning lines of 525 or 625, the electron beam is scanned at twice the speed of the image sending side, and the positions of the scanning lines of the first field and the scanning lines of the second field are A color image receiving device characterized in that the total number of scanning lines is twice that on the image sending side by shifting the scanning line interval of each field by 1/2.