The French term moiré is used to describe wave-like patterns that occur when an existing grid or lines are superimposed with a similar or identical pattern and when both patterns are rotated against each other.
A certain similarity to moirés are the beats known from acoustics and RF technology, which only occur when the frequencies do not differ too much from each other.
Moirés can be detected on screens with masking techniques, for example, with aperture masks or striped masks. The shadow mask has a certain pattern that is repeated in a similar form in the pixels. Since there are electrical fields between the two patterns that minimally affect the beam path, moirés are best recognized as light and dark wavy lines when the screen is illuminated in a single color.
The moiré technique is used in printing to determine the screen. Since photos must always be displayed in halftone in printing, it is possible to determine which halftone was used to print the photo by placing a measuring grid over the photo.