It works common gratings are formed in accordance with the principle of work on physical moire. When the instructions and lined lined grating scale grating at an angle to place when two encoders, will definitely lead lined grating on the two cross each other. Under the irradiation of the light source, near the intersection of the small area as the black-lined overlap, thus shading the smallest and weakest of the light blocking effect, the cumulative effect of light makes the area appear bright band. On the contrary, far from the intersection of the region, due to two overlapping portions of the grating opaque black lined becoming less and less opaque region area becomes larger, the light-shielding area becomes larger, so that the light-blocking effect becomes stronger, only less light through this region through the grating, so that this region appears dark bands, which will form we see moire.
Moire
In a transmission grating, for example, when lined lined between the ruler and the index grating on the grating formed on a small angle ¦È, and placing two relatively parallel grating facets when, under the irradiation of the light source, located almost vertical the gate pattern, forming light and dark stripes. This streak is called "moire" (shown at right). Strictly speaking, the direction of the moire arrangement is lined with two grating angle perpendicular bisector phase.
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