| 摘要 |
<p>PURPOSE:To improve detecting position accuracy by using a lens and providing a shielding portion having a small opening in the vicinity of the focal plane thereof. CONSTITUTION:Light generated by a light emitting element 1 is focused on the position of an object body to be detected by a projecting lens 2, and the reflected light therefrom is focused by a light receiving lens 3 so as to pass through the opening of a shielding portion 4 having the sufficiently small opening provided at the focusing point of the light receiving lens 3, and is detected by a light receiving element 5. When a light source is placed at the focusing position of the projecting lens 2, the light receiving lens 3 is arranged to focus the light on the opening of the shielding portion 4. Therefore The light, reflected from a portion other than the focusing point of the projecting lens 2, is not allowed to pass through the opening of the shielding portion 4 so as not to be detected.</p> |
