Shape Memory Alloy (SMA) in the form of wires the thickness of human hair is used to precisely move the camera lens for both optical image stabilisation (OIS) and autofocus (AF) in smartphone cameras. The characteristic expansion and contraction of the SMA material is controlled by driver ICs and software algorithms which alter the wire length to achieve sub-micron accuracy.
SMA actuators do not require coils, magnets and Hall sensors, with closed loop control achieved through direct measurement of the SMA wire resistance. As a result, SMA actuators are smaller than equivalent voice-coil motor (VCM) actuators and do not suffer from electromagnetic interference, allowing for greater freedom in end-product design.
CML’s previously stated benefits of SMA over VCM solutions were highlighted in the Alps Alpine press-release:
- SMA technology is small and lightweight compared to VCM; with a 40% footprint reduction for same image sensor size.
- Lack of magnetic interference increases handset design freedom, use of multi-cameras and adoption in foldable phones.
- SMA is a high force technology and capable of 10x force compared to VCM enabling controlled motion of heavier lenses and additional components such as variable apertures. For a 1000mg lens, the required footprint for SMA is 60% of the area used by an Alps Alpine VCM actuator.
CML is pleased that mass-produced Alps Alpine SMA actuators have now shipped in major smartphone cameras with expansion to new customers expected in 2023. Read the press release from Alps Alpine: Press Release | Alps Alpine Begins Mass Production of SMA Actuators.
If you’d like to learn more about SMA technology, please get in touch.