The Polaroid Ultrasonic Ranging System
This paper will deal with the electronics and mechanics necessary to perform precise focusing of the camera lens of the Polaroid SX-70 Sonar Camera and the Prontol Sonar Camera. These cameras utilize ultrasonic sound waves to measure the distance to a subject and then convert this information into lens rotation to obtain the correct focus. The system is composed of an electrostatic transducer and three integrated circuits. The complete transmit, receive, and lens rotation to precise focus requires but a few tenths of a second. This unique system has proven extremely reliable compared to other distance measuring techniques.
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