| 摘要 |
PURPOSE:To increase position precision for focusing, to speed up response, and to improve reliability by applying an electrical signal to a piezoelectric element fitted to a lens mount part, and controlling the position of a lens according to variation in the thickness of the piezoelectric element. CONSTITUTION:A range measuring device 8 measures the distance to a subject 1 in the form of the level of a voltage on the basis of the reflection time of an ultrasonic wave radiated to the subject 1 and the focusing point of light, and the voltage from the range measuring device 8 is amplified by an amplifier 9 and applied to the piezoelectric element 7. The piezoelecetric element 7, therefore, varies in thickness with the level of the voltage based upon the distance between the subject 1 measured by the range measuring device 8 and the device 8, and consequently the position of the lens 2 is adjusted axially. Thus, the focus of the lens 2 is adjusted to form a sharp image on a film 6. |
