| 摘要 |
PURPOSE:To perform the judgment of a distance simply and stably, by positioning a light receiving element, which is divided into two parts, so that the image of a light spot on a reference surface is formed on a boundary line of light receiving surfaces, and comparing the magnitudes of the voltages from the two light receiving surfaces. CONSTITUTION:A spot light beam is projected on an object surface 12 by a light projecting part 11 comprising a spot light source and a light projecting lens. The image of the light spot is formed on the light receiving surfaces of a photodiode 14, whose light receiving surface is divided into two parts, i.e. the upper and lower parts. Current I1 and I2 are obtained as the outputs of the received light beams at the upper part and the lower part of the boundary line on the light receiving surfaces of the photodiode 14, which is divided into the two parts. The current I1 and I2 are converted into voltage V1 and V2 by photoelectric conversion circuits 15 and 16. The magnitudes of the voltages V1 and V2 are compared and judged by a comparator 17. The judged result is inverted by an inverter 18, and a light emitting diode 19 for display is driven. The result is taken out as the judged output. |
