VCSELs enabling progress in biometric applications such as mobile 3D sensing, highlights Osram

Since many key technology advances in mobile devices (including smartphones, tablets and wearables) are based on the ubiquitous use of light, including not only visible light (such as display lighting or flash applications) but also invisible infrared light (for example for gesture recognition, iris scanning or facial recognition), vertical-cavity surface-emitting laser (VCSEL) technology can play a role in this development, says optoelectronics component maker Osram Opto Semiconductors GmbH of Regensburg, Germany.

Biometrical user identification methods are currently the most reliable and secure access options. They are an alternative to complex password management tools for mobile device security, access control and, increasingly, authentication for mobile payments and other transactions. The need for these solutions is driven by users increasingly managing all aspects of their digital lives via their smartphone and other mobile devices, which accelerates the development progress, says Osram Opto.

Biometrics make use of human characteristics such as specific structures within the iris, facial features or fingerprints. Sensors identify these characteristics and compare them with previously stored biometrical data. To function reliably in mobile devices, infrared light is required to illuminate the target area. This technology was already being used in access control systems, with most countries using it for immigration purposes. But with the growing miniaturization of infrared LED technology, adoption in mobile and consumer devices has been accelerating. Now VCSEL technology is complementing the portfolio of solutions, enabling use of these applications in a wider market, says Osram.

VCSEL technology opening up new applications fields

VCSEL technology has previously been used for data communications, but recently a multitude of application opportunities in different markets has been identified. Since light radiates vertically from the surface of the chip (rather than from the edge of the chip in edge-emitting laser diodes), surface emitters feature lower production costs than edge emitters and superior beam quality but lower output power. As a surface-mountable component, a VCSEL combines the characteristics of a LED with those of a laser. The technology can also be used as a VCSEL array – composed of several hundred or even thousand VCSELs – for example, a chip with 500 apertures of 1mm x 1mm, glued and bonded like a normal LED.

VCSEL technology is a good choice for applications such as smartphones, drones and augmented reality/virtual reality (AR/VR) devices where high-speed modulation is an advantage, says Osram Opto. 3D sensing applications such as facial recognition (especially for consumer devices) are viewed as key market drivers. Market research firm LEDinside forecasts that the global infrared laser projector market for mobile 3D sensing will grow from $246m in 2017 to about $1.953bn in 2020.

Existing solutions for mobile 3D sensing include structured light and time of flight (ToF). One of the most recent smartphone models uses structured light, with its dot projector producing several ten thousand dots of infrared (IR) light on the face before the infrared camera receives the reflected light to create a 3D facial landscape.

Additional applications include autofocus and proximity functions in cameras (especially smartphone cameras). 3D sensing is also being integrated with AR and VR for smart glasses or future smartphones and other mobile devices, including drones.

Due to its broad range of advantages such as a very small footprint, relatively low cost, optical efficiency, low power consumption, wavelength stability and high modulating rates, VCSEL technology could be key to the wider adoption of applications such as 3D sensing in the mass market, reckons Osram Opto.

Although the technology offers many advantages compared with existing technologies, it is not the best solution for all segments, the firm acknowledges. It should therefore be viewed as an expansion of infrared and other light-based technologies. To help clients choose the most suitable solution for each application, leading providers of optoelectronics components are complementing their infrared technology portfolios with VCSELs, notes Osram Opto.

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