OPTO-ELECTRONIC SCALE-READING APPARATUS

摘要

The apparatus has a scale (10) positioned to be read by a read head (20). The scale (10) has marks (12) defined by first surfaces (40) lying at an angle (E) to second surfaces (50) defining spaces (13) between the marks (12) so that, on illumination of the scale by rays (40A, 50A), the rays (40A) falling on the marks (12) are reflected into the read head (20) while the rays (50A) falling on the spaces (13) are reflected away from the read head (20). The arrangement provides improved contrast between the marks and the spaces.