| 摘要 |
PURPOSE:To improve the detection accuracy of a guidance tape and the reliability with low power consumption by utilizing image forming between a lens and an optical system of light projection and photodetection through an optical fiber. CONSTITUTION:The light irradiated from a light emitting diode 111 is collected by a lens system 113 through an optical fiber cable 112 and the image is formed on a light reflection tape 102. A light 117 reflected again on the light reflection tape 102 is converged by the lens system 113 and made incident in a photodetector 114 via the cable 112. The light 118 reflected correctly is not returned to the lens system 113 because of the incident angle alpha and only the component of the recurrsive reflected light 117 is detected selectively. Even when the tape 102 is placed with a tilt, since the recurrsive reflected light 117 is converged by the lens system 113, the light 117 is not at the outside of the photodetector 114. |
