Introduction And Solution Of Moire Fringe

First, know Moore.

Moore streak was an optical phenomenon first discovered by French researcher Moore in eighteenth Century.

From a technical point of view, moire fringe is a visual result of interference between two lines or two objects at a constant angle and frequency. When the human eye can not distinguish these two lines or two objects, it can only see the pattern of interference, and this optical phenomenon is moire fringe.

Moire fringe is a potential problem for halftone screen printing.

The so-called halftone printing is the way to continuously divide the original manuscript through photography or other methods to decompose the dots into different sizes.

The dark tone is printed by larger dots, and the light is invoked to print smaller dots to show the interference between the same dots, especially multicolor printing or four-color printing, to form moire fringes.

Moire fringes formed between dots are common problems in all levels of screen printing.

Dot and screen can also form another form of moire fringes. The distribution of moire fringes on the screen can produce distinctly different patterns from the manuscript.

Moire stripe can be produced in three aspects:

1. interference between two color or multicolor dots.

2. interference between different dots and silk mesh.

3. as an additional factor, interference occurs as a result of the characteristics of the printed object itself.

The purpose of Moire fringe protection system is to predict moire fringes according to the mesh number, the number of mesh lines, the number of printing colors and the angle of screening.

Two. Avoid moire fringe.

It is possible to predict and analyze moire fringes with mathematical calculations, and the results are only theoretical moire fringes. The moire fringes that actually affect screen printing are visible moire stripes which are harmful to printing results. The moire fringe protection system provides a simple visual control tool for screen printing workers. This tool will avoid moire fringes in any step of the replication process.

Serilor? Log contains two sets of tools to predict moire fringes:

1. analog screen mesh, this is a set of mesh mesh analog film, the number of analog mesh is determined by the test chip you ordered - Advanced test piece and Basic test piece.

The two sets of test pieces include four mesh numbers: Code MG -S -B:100T /cm, 110T /cm, 120T /cm, 130T /cm, (255T, e, e, e).

The Advanced test piece also contains a series of MG -S -A's breakdown numbers: 140T /cm, 150T /cm, 165T /cm and 180T /cm.

For screen printing or screen printing, MG -S -C:77T /cm, 81T /cm, 85T /cm and 90T /cm are used for coarse screen purposes; MG MG, 81T, /cm, and /cm.

Special purpose and high tension wire mesh test pieces need special order.

{page_break}

Two

The identification instrument / indexing instrument can overlap the indexing instrument and the film to detect the number of the film and the color separation angle.

The two sets of tools can be used interchangeably to analyze mesh number / mesh number / dot angle and moire function.

You need to install a light stable glass worktable in the darkroom to provide high intensity and stable light sources. Weak light makes it difficult to find moire patterns.

The two sets of protective tools of Moire fringe can help you choose the screen correctly, and also help you choose the color separation parameters (the number of lines and angles) and the printing parameters.

3. the following examples can help you understand the use of Moore protective tools.

(1) the dichroic film provided by the customer should choose the correct mesh mesh. First, the mesh mesh analog chip is placed on the glass worktable, and then the color separation film is placed in the selected mesh area. The color separation film must be exactly aligned with the corresponding position of the analog chip.

When using multicolor or four color printing, each type of dichroic film must be placed on the mesh simulator for inspection.

In some special cases, moire fringes will appear very clearly in one of four dichroic patches.

Experience has proved that this screen can solve these problems with different screen mesh.

The mesh number can be selected through the Garnandstandard test chip to select the nearest silk screen without moire fringe.

Note: This is your last solution to this problem. On some occasions, it can not work, and it will change the amount of ink deposition and cause additional trouble: drying speed, screen definition, color deviation.

(2) mesh mesh can not be changed but color splitter can be changed. Due to special technical factors, you may not be able to change mesh number (printing parameters and ink deposition have been set). At this time, you need to fix the parameters of the dichroic film to avoid moire fringes.

Using the mesh analog film matching the mesh number of the screen mesh and the moire fringe dividing instrument on the mesh analog chip according to the screening angle of the dichroic screen, you can determine the number of wire added in your dichroic screen.

When you turn the indexing instrument, different superposition will produce moire fringe.

If moire fringes appear only in high light areas (below 10% percentage points below)

Almost no impact, but when moire fringes are generated at all grayscale rungs or appear at 50% nodes, you must change the screening angle.

When visible moire fringes appear, we need to change the number of mesh lines or dichroic patches until all the dichroic chips coincide with the screen.

Before selecting the screening angle, check the recommended values of the scanner.

These screening angles are different for different printing processes (offset printing, flexographic printing) and country related.

For example, the screening angle of North American offset printing and European standard DIN16547 (1) are almost unified, but belong to different color plates.