| 摘要 |
<p>A light-emitter (22) emits light, and a plano-convex condenser lens (26) focuses the emitted light and projects the focused light onto a floor (25) near a door (14) to thereby establish a sensing area. A plano-convex light-receiving lens (28) focuses light reflected from the sensing area (16), and a light-receiver (24) receives the focused, reflected light. The plano-convex lenses (26,28) have edges closer to the door (14) which is substantially straight. <IMAGE></p> |
