JPH03158894A - Method for suppressing moire fringe displayed on color cathode-ray tube - Google Patents

Abstract

PURPOSE:To make a moire fringe inconspicuous for a user by oscillating correlative phase or raster between an image signal and a deflecting frequency signal with a signal with frequency lower than the deflecting frequency and equal to its divisor and whose timing is fitted in that of the deflecting frequency. CONSTITUTION:The signal with the same frequency as the horizontal deflecting frequency fH and the vertical deflecting frequency fV of a color monitor 2 in which a moire fringe is generated is supplied to a moire fringe suppression circuit 1. The signal supplied to the moire fringe suppression circuit 1 is frequency-divided to 1/m and 1/n, respectively, and they are sent as moire suppression signals 1/mfH and 1/nfV, and are inputted to the image signal phase adjusting circuit and the raster shift circuit of the color monitor 2, respectively. Where, (m), (n) are integers. As a result, since an electron beam is oscillated with the frequencies 1/mfH and 1/nfV, and an electron beam scanning line position that is one cause to generate the moire fringe is fluctuated, a moire fringe appearing position is also fluctuated, which makes the moire fringe inconspicuous for the user.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention makes moire fringes that appear on the display screen of a shadow mask type color cathode ray tube less noticeable.

This invention relates to a method for suppressing moiré fringes so that they do not become noticeable.

[Prior Art] The display screen of a shadow mask type color cathode ray tube includes a group of periodically deflected electron beam scanning lines.

Interaction of periodically arranged apertures in a shadow mask, periodically arranged phosphor dots or stripes on a phosphor surface, or periodic patterns that sometimes exist in the original display target image. Moiré fringes may appear as a snarl due to interference between images.

In order to prevent the occurrence of such moiré fringes, a technique that considers the arrangement of holes in a shadow mask is disclosed, for example, in JP-A-56-
The one disclosed in Japanese Patent No. 71256 is known. Such moire fringes can be fundamentally suppressed to some extent when standards are clearly defined, such as in the case of television broadcasting, but when used as a display terminal for an OA system, For example, it is impossible to eliminate such problems because a particular type of tube may be used by multiple users with different deflection frequencies that each user prefers.

Conventionally, when moire fringes occur, countermeasures have been taken such as increasing the diameter of the electron beam or changing the pitch of the apertures in the shadow mask.

C9! Akira tries to solve it! IM] However, the conventional countermeasures described above are unsuitable for displaying high-definition images when the diameter of the electron beam is increased, and poor focus becomes more of a problem than moiré fringes themselves. This change is a change in mask specifications and cannot be easily changed.

When moire fringes occur, the present invention does not require palliative measures such as weakening the focus of the lightning f-beam, but can easily eliminate moire fringes according to the usage situation.

To provide a method for suppressing moire fringes that is not noticeable or bothersome to a user.

[Means to solve the problem] In order to achieve the above object, the present invention.

Even moire fringes, which in principle cannot be removed.

Moiré fringes can be placed at specific positions on the display screen by vibrating the correlation phase between the image signal and the deflection frequency signal or by vibrating the mask using a signal with a frequency that is lower than the deflection frequency, equal to its divisor, and whose timing matches the deflection frequency. We decided to make it inconspicuous and unobtrusive by not making it fixed, but by constantly changing its appearance so that the user would not notice it.

[Effect] With the above method, even if moire fringes exist at a certain moment, their appearance position changes constantly at a frequency that does not bother the user, so their presence is weakened. For the user, this is the same as removing moire fringes.

[Example] FIG. 1 is a diagram showing an example of the present invention. Moire fringe suppression circuit 1
13, which is the same frequency as the horizontal deflection frequency fH1 and the vertical deflection frequency fv of the color monitor 2 where moiré fringes occur.
The signals given to Momo 1 are frequency-divided into 1/m and 1/n, respectively, and sent out as moiré fringe suppression signals 1/m fH and 1/n fv. It is input to the signal phase adjustment circuit and mask shift circuit. However, 1m
, n are all integers. As a result, the display screen is 1/mfH, 1/nf as shown in Fig. 2(a) and Fig. 2(b).
As the electron beam vibrates at a frequency of suppressed.

Note that the state of occurrence of moiré fringes varies depending on the usage conditions, so in reality, experiments are performed using the above circuit, and appropriate values are experimentally determined by adjusting the frequency and amplitude of each signal while looking at the displayed image. stipulated in

[Effects of the Invention] As explained above, according to the present invention, moiré fringes can be appropriately created to disturb the user depending on the usage situation without loosening the focus of the electron beam or changing the shadow mask specifications. It can be suppressed so that it does not occur.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a moire fringe suppression circuit according to the present invention,
FIGS. 2(a) and 2(b) are diagrams showing the state of the display screen when the moire fringe suppression circuit according to the present invention is operated. 1... Moire fringe suppression circuit, 2... Color monitor. 3...Monitor display screen when the moire fringe suppression circuit is operated using the horizontal deflection signal, 4, 5...Monitor display when the moire fringe suppression circuit is operated using the vertical deflection signal screen.

Claims (1)

[Claims] 1. On the display screen of a shadow mask color cathode ray tube,
A group of periodically deflected electron beam scanning lines, a group of apertures arranged periodically in a shadow mask, a group of phosphor dots or stripes arranged periodically on a fluorescent surface, or in the original display target image. The moiré fringes that occur as a beat due to interference between a group of patterns that periodically exist in the image signal and the deflection frequency signal can be detected by using a signal whose frequency is lower than the deflection frequency, equal to its divisor, and whose timing matches the deflection frequency. A method for suppressing moiré fringes in a color cathode ray tube display, characterized in that the moiré fringes are made less noticeable by vibrating the phase or raster correlated with the moiré pattern.