SMA Module Tilt OIS

Cinematic video quality is increasingly marketed with the latest smartphone cameras. This means that consumers are now looking for video mode capabilities with an increasing array of use cases, such as walking, running and cycling. To provide the best possible video mode output, optical image stabilisation (OIS) is required to avoid user generated picture blur.

Rotation out of the sensor plane is the dominant source of image blur for most imaging conditions, for which tilt motion compensation provides the ideal optical solution. However, the majority of image stabilisation is achieved by moving the lens with respect to the image sensor, known as Lens Shift OIS. With Sensor Shift OIS, it is the image sensor which moves with respect to the lens barrel. For both Lens Shift OIS and Sensor Shift OIS an angular correction is enabled by shifting the lens or sensor in a translation movement parallel to the sensor plane. Whilst this can result in images or videos showing good suppression at the centre, Lens Shift OIS and Sensor Shift OIS solution may still show motion blur in the corners. 

Corrections using computation software are often used, but these result in a reduction of the video resolution and thus the overall quality.

SMA Module Tilt OIS acts as a gimbal stabilisation system, which moves a standalone camera module, with the lens and image sensor fixed in position with respect to each other. The result is superior image quality, as uniform image stabilisation across the entire image sensor is achieved. 

Lens Shift OIS and Sensor Shift OIS cameras are typically rated to ±1.5deg shake compensation. Above that, the image quality visibly degrades. For Module Tilt OIS, a uniform shake correction can be achieved for higher shake amplitude, currently up to ±3deg. The mechanical OIS means there is no need for an EIS application that reduces the output image resolution from the image sensor. These capabilities allow Module Tilt OIS to extend the video use cases from hand shaking correction to action camera applications.

Cambridge Mechatronics Ltd. (CML) have developed the Module Tilt OIS actuator system using Shape Memory Alloy (SMA) technology, SMA wires of 30um diameter are configured to hold the AF camera module in a cradle position. These SMA wires contract and expand upon heating and cooling with high force to move the camera module in a tilt and roll motion to a desired position. Fast and precise control of the actuator and camera is delivered by CML's unique IC and Firmware to generate ultimate OIS performance. CML's use of SMA technology enables a design approach that allows CML's Module Tilt system to overcome the drawbacks of a VCM system. 

4. CML's SMA Module Tilt OIS system provides shake compensation for >3deg tilt in X, Y and rotation about Z;
5. CML’s design incorporates the FPC within the camera module, thereby achieving a compact design that has a >25% smaller XY footprint compared to VCM; 
6. The cradle design avoids the need for a gimbal, thus reducing the SMA solution module height by 1.7mm compared to the VCM design;
7. CML’s unique controller chip (CM824) and firmware removes the need for position (Hall) sensing technologies that VCM requires;  
8. SMA technology does not use magnets or generate magnetic flux – this makes it hugely suitable for today’s handsets which contain many components susceptible to magnetic interference, such as antennae, wire charging coils, other cameras and speakers, whilst offering mitigation for image noise;  
9. CML delivers and supports a complete actuator system, including actuator, controller chip and patent firmware which provides ultimate performance and unique features.