| 摘要 |
PURPOSE:To prevent misjudgement by interrupting discriminating operation of a judging circuit when an auxiliary detection light is projected to a part to be detected close to a main detection light or the reflected light thereof and reflected from a light shielding object. CONSTITUTION:A laser beam 4a from a main projection element 4 is received with a main light receiving element 8 reflected from a point 0 to be detected and provided to a discrimination circuit 11 via an A/D conversion circuit 10. Depending on whether the electrical signal is equal to, larger or smaller than the reference value preset and memorized in the discrimination circuit 11, the circuit determines the condition at the point, flat, concave or convex. When infrared rays 14a and 17a are projected to the point being detected from the auxiliary projection elements 14 and 17, there is little reflected light from the ground. A stick 24 traverses the laser beam 4a from the main projection element 4 and simultaneously the infrared beam 14a from the auxiliary projection element 14 and a reflection sheet wrapped on the stick reflects it. The laser beam thus reflected is received with the light receiving element 14 which outputs a stop signal to the discrimination circuit 11. This stops the operation of the discrimition circuit 11 temporarily to prevent misjudgement. |
