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EETE FEB 2015

OmniVision replaces VCM with MEMS autofocus By Peter Clarke CMOS image sensor vendor OmniVision Technologies Inc. (Santa Clara, Calif.) has used a MEMS-based autofocus system from Wavelens SA (Grenoble, France) for autofocus, which it reckons is superior to the “dated” voice coil motor (VCM). The VCM is used in many image sensors today but OmniVision has coupled its 23.8-magapixel OV23850 sensor with a MEMS from Wavelens to produce a highspeed autofocus and bring digital still camera functionality to high-end smartphones. The OV23850 is capable of recording quad high definition (QHD) video at 30 fps in HDR mode to enable ‘always on’ HDR preview mode for a resolution size popular with flagship smartphone displays. Additionally, the sensors support 720p HD video at 120 fps and 1080p HD video at 90 fps, allowing for crisp slow motion video recording. Wavelens has developed three optical MEMS with different optical apertures and dimensions to cater form a few megapixels to more than 20 megapixels. Wavelens’ optical MEMS consists of an optical membrane released onto an optical oil-filled cavity, with MEMS actuators embedded at the membrane periphery. As an operating principle, when the MEMS are actuated, the optical oil flows through the membrane center-modifying the membrane’s curvature and introducing a focal length variation. This smart combination of the flexible membrane and the optical oil makes possible an efficient and powerful variable focus component. Since the MEMS actuators are embedded at the membrane periphery, Wavelens technology is very competitive in term of compactness (ratio between MEMS outline and optical aperture). Thanks to the optical oil, the voltage required is typically below 10V, because of the low force needed to change the membrane curvature, and the power efficiency is very high. The optical power variation required for Autofocus application (at least 10 diopters) can easily be achieved for a wide range of optical MEMS aperture. Wavelens optical MEMS has a functional thickness less than 100-microns. “With our partnership with OmniVision, we are able to fully leverage the high-speed focus and low-power consumption that our MEMS-based autofocus technology offers,” said Sebastien Bolis, CEO at Wavelens, in a statement. Aiming at smartphones, poLight readies for mass production By HJulien Happich eadquartered in Horten, Norwegian startup poLight AS has raised NOK 146m (USD19M) in a private placement of shares, to fuel the deployment of its piezo-MEMS auto-focus lens technology, TLens. “The funds will take us all the way into the global market” told us poLight’s newly appointed CEO Øyvind Isaksen, “helping us step up our manufacturing capacity and expand our organization with the opening of extra offices to get nearer our customers”. Currently, the company is working with several potential customers and is ramping up manufacturing capacity in a cooperation with ST Microelectronics as a manufacturing partner, with volume production planned for the second half of 2015. Assembled at wafer level, each 2.9x2.9mm TLens consists of a very thin piezo-actuator layer on top of a thin glass membrane that deforms a soft polymer sandwiched with a thicker layer of glass. By applying varying voltages (up to 30V), the piezo actuator forces the thin glass membrane to bend, deforming the polymer underneath it and varying the optical focus. The TLens is claimed to be ten times faster than today’s widely used VCM (Voice Coil Motor) lenses, while drawing 20 times less power. These features make them very attractive as a replacement for bulkier VCM assemblies, also enabling fast consecutive multi-focus shots to implement full-focus photos in software. Although Tlens currently rely on ST’s fab capacity, the company owns the full process IP and could easily second source its capacity. “We see a huge expansion of the market for autofocus lenses”, said Isaksen, “Autofocus used to be reserved to back-facing cameras, now you also find it on front-facing smartphone cameras and across multiple cameras for stereo-imaging, all these represent new opportunities for poLight” he added. The company has also developed a proofof concept for image stabilization, again with a very low power consumption, no inertia and no wobbling compared to multiple VCM assemblies. Next step for poLight will be to become a public listed company. “We will probably do a pre-IPO by late 2015 or mid-2016 when we are in the market and are starting to generate revenue, an IPO could follow 12 months later”, said Isaksen. One could establish a parallel with Wavelens, a French startup with similar performance claims for another MEMS-based lens technology using an oil-filled cavity instead of a polymer for the optical path variation. “The real competition now is VCMs, so there will be plenty of room for a couple of competitors” admitted Isaksen. www.electronics-eetimes.com Electronic Engineering Times Europe February 2015 39


EETE FEB 2015
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