| 摘要 |
PURPOSE:To detect positions having a fine internal at a high speed and with high precision by forming two spots on a fixed scale which has position detection marks at prescribed pitch by splitting and focusing luminuous flux from a light source, and then detecting their reflected light beams by a movable optical system. CONSTITUTION:A read head 2 movable in a direction AB is opposed to a fixed scale 1 having black-and-white marks of width l/2 at pitch (l). Light from a semiconductor laser 3, polarized at 45 deg. to a paper surface, is reflected by the 1st polarizing prism 6 after passing through a collimator lens 4, and then focused (spot diameter l/2) on the fixed scale 1 through a quarter-wavelength plate 7 and a condenser lens 8; and its reflected light travels backward to illuminate a photodetecting element 9 through a polarizing film 5. The reflected light of the light spot transmitted through the polarizing film 5, on the other hand, is detected by a photodetecting element 15 similarly. Thus, positions having a fine interval are detected at a high speed and with high precision. |
