| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To improve SN ratio in optical reading of a pattern by an exclusive pen or the like from a coordinate input sheet suitable for handwritten character input on a display screen or the like and having coordinate information printed as a coordinate information pattern on a sheet surface. <P>SOLUTION: As the coordinate input sheet 3, a one including a coordinate information pattern 1 having a cholesteric structure formed on a base material 2 is used to selectively reflect only circularly polarized infrared ray by the pattern 1, and circularly polarizing filters 61 and 62 are disposed in illuminating light and reading light paths to read the pattern. When a selected reflected light 8R from the pattern 1 is right circularly polarized light, right circularly polarizing filters are used as the circularly polarizing filters 61 and 62, whereby a reflected light 8L from a non-pattern part is reversed to left circularly polarized light by mirror reflection although the selectively reflected light 8R from the pattern 1 remains the right circularly polarized light. Therefore, only the selectively reflected light 8R from the pattern 1 which are right circularly polarized reaches an image sensor 5 by the circularly polarizing filter 62, and the SN ratio is thus improved. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
