| 摘要 |
This optical rotation encoder for a X-Y direction input device comprises a light source (51), two light-sensitive elements (53, 55) aligned vertically and a circular encoding wheel (42) placed between the light source and the light-sensitive elements, and provided with a plurality of openings (47) distributed at equal angles with, in each case, an arc sector region forming a screen (46) between two adjacent openings. The wheel is at a first distance from the source and at a second distance from the light-sensitive elements, in order to obtain a X-Y displacement of the input device by virtue of a plurality of pulses resulting from the light which is received by the light-sensitive elements after having passed through the openings intermittently when the wheel turns. The source is a point source and either the opening or the region forming a screen has a width which is less than that of the pair of the light-sensitive elements. <IMAGE>
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