SMA Actuators Capable of Driving Glass Lenses

Friday, November 3rd 2017

The drive to improve image quality in smartphone cameras has seen vendors invest in next generation glass lenses, e.g. the LG V30 is shipping with hybrid lenses. Glass offers an inherent advantage over plastic when used to make lenses as it has lower dispersion, higher refractive index and better scratch resistance. Dispersion is a mechanism that produces disruptive colour fringes, and a lower dispersion material will produce a lens that is optically purer and gives a clearer image. The higher refractive index of glass means that lenses can be made thinner than an equivalent plastic lens, leading to a thinner camera design.

A feature of glass is that it is significantly denser than plastic, and even though lenses can be made thinner, they have a higher mass than a plastic lens. The additional weight of these lenses compromises the performance of auto-focus and optical image stabilisation mechanism based on voice coil motors as the means to drive actuation.

In a recent news release CML stated that the use of heavier glass lenses should be well within the performance envelope of SMA based actuators and we are pleased to report that our expectations for high level operation have been confirmed.

We have taken SMA OIS actuators and characterised the image shake suppression performance, using our state of the art automated measurement equipment. The measurement was repeated for a range of lens masses including standard plastic lenses, current state of the art of hybrid glass lenses and significantly greater masses than are expected for next generation glass designs. We have demonstrated that image shake suppression levels were independent of the mass of the lens assembly and that CMLs SMA technology can overcome the limitations that VCM actuators have when driving heavier lenses.