Technology Overview
The thermo elastic properties of the family of metals known as Shape Memory Alloys (SMA) were discovered in the 1930's. In the early 1960's the US Naval Ordinance Laboratories (NOL) carried out a great deal of research on a particular SMA made from Nickel (Ni) and Titanium (Ti). This alloy became known as NiTiNOL.
Heating wire made from NiTiNOL makes it contract against a spring, cooling allows the spring to elongate the wire back to its original length. Actuators using SMA wire have displaced motors and solenoids in many applications to save space, weight and cost. CML's achievement has been to miniaturise these actuators by using very thin wire, down to 25µm, a quarter the thickness of a human hair.
CML has also learned how to compensate for the thermal non-linearities caused by the wire movement and by environmental changes inside a miniature camera. This was necessary for the actuator to behave in the linear and repeatable manner prerequisite for the Autofocus (AF) application. By fully understanding the thermodynamics of the entire SMA-based miniature camera, CML was able to develop a tiny ASIC which varies the current supplied to the wire depending on the ambient temperature and the position of the lens. Crucially this is done without the aid of position or temperature sensors. CML's ASIC monitors the resistance of the wire and therefore its length, which enables it to make a real-time calculation of the lens position.
CML have applied this knowledge to the following product areas:
