| 摘要 |
PURPOSE:To exactly find a range extending from a short distance to a long distance by simple constitution by providing a photodetecting means which a reflected light from an object to be photographed of a range finding use light is made incident on and outputs two signal corresponding to the incident position. CONSTITUTION:A light beam emitted from an infrared-ray light emitting element 1 is allowed to irradiate an object to be photographed 3, and a reflected light is brought to image formation on a position detector 5. In the detector 5, in accordance with the image forming position, a photocurrent is brought to current diversions I1, I2, supplied to auto focus (AF) use integrated circuit 6, the element 1 is brought to pulse driving through a transistor 1A, and also, the diverted currents I1, I2 are brought to AF operation, its result is supplied as AF data to a CPU 7, and a distance of the object to be photographed is derived. When its distance is a short one, it can be decided that S/N of an optical signal is high, and based on a signal corresponding to a ratio of both, and in case of a long distance, based on a signal which depends on intensity of the reflected light, the AF data is derived by an integral operation, respectively. Accordingly, in case of a short distance, the range finding can be executed exactly, based on a theory of a trigonometrical distance measurement without depending on intensity of the reflected light, and in case of a long distance, the range finding being proportional to the reflected light can be executed. |
