Patent ID: 7433256

Claim:
System comprising: an optical element ( 102 ) for generating a periodic array of light spots ( 103 ) intended to be applied to an information carrier ( 101 ), said information carrier ( 101 ) comprising a first periodic structure ( 108 ) being intended to interfere with said periodic array of light spots ( 103 ) for generating a first moiré pattern, and a second periodic structure ( 109 ) being intended to interfere with said periodic array of light spots ( 103 ) for generating a second moiré pattern, said second periodic structure ( 109 ) being placed perpendicularly to said first periodic structure ( 108 ), first analysis means ( 118 ) for deriving from said first and second moiré patterns, the spatial position (x,y) between said periodic array of light spots ( 103 ) and said information carrier ( 101 ), first actuation means (AC 1 -AC 2 ) for adjusting the spatial position of said information carrier ( 101 ) with respect to said array of light spots ( 103 ), based on control signals ( 122 ) derived from said spatial position (x,y).