The Polaroid ultrasonic sensor was an electrostatic ultrasonic transducer developed in the 1970s to focus Polaroid’s instant cameras automatically. It first shipped in the SX-70 Sonar OneStep in 1978. Polaroid’s OEM division later supplied the same transducer to industry, where it became a standard in robotics research. SensComp acquired that division in 2002 and remains the exclusive manufacturer of the line, now the SensComp Series 600, built in Livonia, Michigan.
KEY ANSWERS AT A GLANCE
What was the Polaroid ultrasonic sensor? An electrostatic ultrasonic transducer that Polaroid developed in the 1970s to give its instant cameras sonar autofocus.
Which camera used it first? The SX-70 Sonar OneStep, introduced in 1978, the first autofocus single-lens reflex camera available to consumers.
Why electrostatic? Piezoelectric ultrasonic transducers couldn’t meet the sensitivity the camera needed to range soft subjects such as people.
Who makes it now? SensComp acquired Polaroid’s OEM products division in 2002 and is the exclusive manufacturer of the SensComp Series 600.
Can I replace a legacy Polaroid part? SensComp still builds the SensComp Series 600 transducer and the 6500 Ranging Module and can match a legacy part to a current product.
Why did Polaroid develop an ultrasonic sensor?
Polaroid developed its ultrasonic sensor to solve a focusing problem. The original SX-70, introduced in 1972, was a folding single-lens reflex camera that relied on the photographer to focus by eye, and many users found that hard, especially in dim light.
Polaroid’s answer was sonar: measure the distance to the subject with a burst of ultrasound, then drive the lens to match. That required a transducer sensitive enough to pick up faint echoes from a person’s face and clothing, which are soft, sound-absorbing targets. Piezoelectric ultrasonic transducers couldn’t meet the requirement, so Polaroid invested millions of dollars in a compact, low-cost electrostatic ultrasonic transducer instead.
The result shipped in 1978 in the SX-70 Sonar OneStep, the first autofocus single-lens reflex camera available to consumers. Half-pressing the shutter button sent out the ultrasonic burst, and a motor turned the lens to the measured distance. Because the camera measured distance with sound rather than light, it could focus in the dark.
How did the Polaroid ultrasonic transducer work?
The Polaroid transducer works like a capacitive microphone that can also transmit. A thin, gold-coated plastic film is stretched across a round, grooved aluminum backplate, and a DC bias charges the film relative to the plate. To transmit, a high-voltage pulse drives the film. To receive, the returning echo moves the film and changes the capacitance, producing a small signal that the electronics amplify and time.
The grooves in the backplate let the film flex and broaden its frequency response. The same principle is at work in every SensComp electrostatic ultrasonic transducer today: a low-resonant film membrane that settles quickly after transmit, a broadband response of roughly 20 kHz to 100 kHz, and approximately 40 dB greater receive sensitivity than piezoelectric ultrasonic transducers.
How did Polaroid sonar move beyond cameras?
Polaroid’s OEM products division began supplying the transducer, and the ranging electronics built around it, to engineers outside photography. Paired with the Polaroid 6500 ranging module, the instrument-grade transducer became a standard in mobile-robot research. The Springer Handbook of Robotics describes that combination as the basis of most conventional sonars of the period.
The module’s low cost and simple digital interface made it a popular choice for sonar arrays, and researchers mounted rings of them around a robot’s perimeter to map rooms and avoid obstacles. Industrial users applied the same technology to non-contact sensing of all kinds.
Who makes the Polaroid ultrasonic transducer today?
SensComp acquired Polaroid’s OEM products division in 2002 and remains the exclusive manufacturer of the transducer line, now sold as the SensComp Series 600. The smaller Polaroid 7000 transducer continues as the Series 7000, and the Polaroid 6500 ranging module as the 6500 Ranging Module.
SensComp builds all three in Livonia, Michigan. The company is ISO 9001 certified and woman-owned.
How has the technology changed since Polaroid?
The operating principle is the same, but the product line has kept moving. The SensComp Series 600 Instrument Grade and Environmental Grade transducers have gained 304 stainless-steel housings and improved gasketing. Environmental Grade transducers add an optional parylene coating to protect against moisture, chemical exposure, and corrosion, with minimal dampening of acoustic sensitivity. Complete sensors now build the drive electronics in, including the Smart Sensor and the Mini Series.
The applications have moved just as far: agricultural boom height and canopy sensing, AGV and AMR obstacle detection, level sensing on grain, powder, and foam, and people and vehicle detection. A SensComp electrostatic sensor has also been qualified as a component for NASA’s mission to Titan, Saturn’s largest moon.
Can you still buy Polaroid ultrasonic sensors?
Not under the Polaroid name, but the line is still in production. SensComp manufactures the SensComp Series 600 transducer and the 6500 Ranging Module that grew out of Polaroid’s OEM products, so many legacy designs can be supported with current parts.
If you’re maintaining equipment built around an original Polaroid transducer or ranging module, contact SensComp with the part number or a photo of the unit, and SensComp can match it to a current product.
Frequently Asked Questions
The Polaroid SX-70 Sonar OneStep, introduced in 1978, was the first camera to use Polaroid’s sonar autofocus and the first autofocus single-lens reflex camera available to consumers. The folding SX-70 had launched in 1972 as a manual-focus camera. Later Polaroid models, including the SLR 680, also carried sonar autofocus.
Sensitivity. A camera has to range people, and soft, sound-absorbing subjects return only faint echoes. Piezoelectric ultrasonic transducers couldn’t meet that requirement, so Polaroid developed an electrostatic ultrasonic transducer. SensComp electrostatic ultrasonic transducers today have approximately 40 dB greater receive sensitivity than piezoelectric ultrasonic transducers.
SensComp acquired Polaroid’s OEM products division in 2002 and is the exclusive manufacturer of the SensComp Series 600, the transducer line that began at Polaroid. SensComp builds it in Livonia, Michigan.
The Polaroid 6500 ranging module was the drive and detection board paired with Polaroid’s instrument-grade transducer. It fired the transducer, timed the echo, and reported the result over a simple digital interface, which made it a favorite for robot sonar arrays. SensComp builds the 6500 Ranging Module today
Cost and simplicity. The 6500 ranging module and instrument-grade transducer were inexpensive, low-power, and easy to connect to a microcontroller, so researchers could build rings of sensors around a mobile robot. The Springer Handbook of Robotics describes the pairing as the basis of most conventional sonars of the period.
In many cases, yes. SensComp still manufactures the SensComp Series 600 transducer and the 6500 Ranging Module that grew out of Polaroid’s OEM products. Send SensComp the part number or a photo of the unit, and SensComp can match it to a current product.
Maintaining a Polaroid-era design, or starting a new one?
Find the right SensComp electrostatic ultrasonic sensor or transducer for your application: Try our Sensor Selector.
REFERENCES
- Museum of Design in Plastics, “Polaroid SX-70 Sonar One Step.” https://www.modip.ac.uk/artefact/aibdc-006210 (1978 introduction; first consumer autofocus SLR)
- Kleeman, L., and Kuc, R. “Sonar Sensing.” In Springer Handbook of Robotics, 1st ed., edited by B. Siciliano and O. Khatib, pp. 491–519. Springer, 2008. https://doi.org/10.1007/978-3-540-30301-5_22 (robotics use, p. 497 and p. 501; transducer construction, p. 498)