News

May 12, 2023

Image sensor shifter uses shape memory alloy

Cambridge Mechatronics (CML) has used shape memory alloy to create an image

Cambridge Mechatronics (CML) has used shape memory alloy to create an image sensor shifter for five-axis optical image stabilisation in phones.

"The main challenge in sensor shift is the requirement to move the image sensor whilst simultaneously connecting it to the handset," according to the company. "Traditional voice coil motors are limited in the force they can generate. Additionally, voice coil motors don't allow for the 5th axis of motion, roll, as they are prohibited by one smartphone brand's patent portfolio."

The CML actuator has four 25μm diameter shape memory wires in a square around the image sensor (hidden in image). These contract on heating above a transition temperature – allowing the image sensor position to be controlled thermally through wire length.

"The wires generate a high force which means a wide range of interconnect materials and designs can be used, from flexible printed circuits to metal flexures or trace suspension assemblies," said CML, which claims that its four-wire designs have shipped in >45 million handsets. "The first smartphone camera incorporating CML's new sensor shift technology was released in the flagship handset of a major brand early in 2022."

Control is through the company's own driver chip, which does not need Hall position sensing.

The four shape memory wires are out of sight, moving the image sensor (visible in top photo) within the flat housing it surrounding it. The sensor can be moved by the wires in two orthoganol ‘flat’ directions, as well as be rotated around a vertical axis. The obvious vertical ‘walls’ in the top photo on the far side are flexi-PCBs taking signals from the sensor.

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