Firm claims anti-shake camera breakthrough
CML (Cambridge, England) has created an actuator based on wires of nickel-titanium shape memory alloy (SMA) and an associated control and heating ASIC. The alloy has the property that it contracts and expands in a precise and reliable manner under heating and cooling.
The system uses a set of SMA wires to control the pitch and yaw of the lens in its housing and this must be done at frequencies of 1 to 30-Hz in response to gyroscope measurements of handshake, said CML CEO Simon Calder. The same technology is also used to control the z-position of the lens for focus.
CML has already succeeded in getting SMA-based control designed into cameras for autofocus. Mobile phones using AF technology are on sale in Japan, Calder said. But increasingly smartphone developers want to offer similar capabilities to digital still cameras, including OIS, but in a smaller and slimmer device.
Prototype smart-phone camera modules built to take advantage of CML’s OIS actuation provide more than 24-dBs (more than 4 optical stops) of hand shake suppression, Calder said. This enables as much as a 20-fold increase in exposure times without hand-shake induced blur. This will help eradicate two weaknesses of smart-phone cameras, poor (or no) low-light performance and shaky video recordings. It also improves the quality of photographs taken in other conditions.
The SMA based system is smaller stronger and simpler and consumes less power than conventional system which is a voice-coil motor, Calder added.
The spatial efficiency of CML’s actuation means that smart-phone image quality is improved without increasing the camera module’s size. At 8.5-mm by 8.5-mm by 5.7-mm CML’s 8-Mpixel camera is the same size as cameras found in today’s popular smart phones.
"For OIS voice coil motors require 6 meters of 25-micron diameter copper wire and 18 magnets. We just need 8 centimeters of 25-micron diameter SMA," said Calder.
The only way for VCM based OIS systems to incorporate these extra actuators was to expand in the x and y dimensions, increasing footprint by as much as 120 percent. As SMA actuators have less than 1 percent of the mass of an equivalent VCM, camera designers can achieve the 8.5-mm square size for a three axis OIS+A-F system with a 1/3 inch sensor and a large lens.
Many smart-phone vendors are in the process of specifying or selecting OIS-plus-AF enabled cameras for future model releases.
CML is currently qualifying the electronics and firmware required to control the SMA OIS and A-F actuators. The solution is based on the XC104 SMA Motor Processor IC developed by CML together with Swindon Silicon Systems Ltd. The chip is based on an 8-bit 8051 processor core that controls integrated MOSFETs that deliver up to 30-mA to heat and control the SMA wire. The chip is being manufactured for CML and Swindon Silicon by IBM at its Burlington facility in a 0.18-micron CMOS process.
CML’s business model is to license lens and camera module integrators to use its SMA actuator patent portfolio and provide the control ASIC, Calder said. CML is targeting mass production of 8- and 13-Mpixel OIS-plus-AF cameras in the second quarter of 2012.
"We have delivered a system that is demonstrably better than some of the best OIS-enabled DSLR cameras. The form factor and usage model of smart-phone cameras mean that their need for OIS is even greater. SMA-based OIS is a technological innovation that will give smart-phone consumers an instant and palpable improvement in their user experience," said Calder.
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