Infrared emitter unlocks mobile phones

Biometric identification methods for mobile phones and tablet computers are the latest trend as these devices are being used more and more for sensitive applications such as online banking and shopping. In addition to fingerprint scans, many manufacturers are now considering iris scanning as the new biometric unlocking method. The eye is illuminated with infrared light and the camera on the device takes a picture of the iris so that its characteristic features can be identified.

The SFH 4780S offers the best performance-to-size ratio. It has a wavelength of 810nm and is the first IRED in the high-performance Oslux package. "Oslux LEDs have long been established for visible lighting applications in mobile devices, such as camera flash,” said Sevugan Nagappan, Product Marketing Manager for infrared, Osram. “We are now extending the range to include infrared emitters." Oslux components have a very narrow emission angle at a low height so they provide optimum performance. This is achieved by perfectly matching the lens to the internal reflector. A special feature of Oslux is the flat component surface despite the use of a lens.

The SFH 4780S offers extremely high radiant intensity for its compact size. Despite the low height of 2.4mm, developers have managed to achieve an emission angle of only ±10º. As a result, the IRED achieves a record radiant intensity of typically 2900mW/sr at an operating current of 1A. This high optical output comes from a highly efficient thin-film chip with an edge length of 750µm in which two emission centers are arranged one above the other with the aid of Osram’s nanostack technology. The emitter can even be operated with a current of up to 2A in pulsed mode. Thanks to its black package, the SFH 4780S can be integrated completely unobtrusively behind the covers of mobile devices.

For mobile device applications, it is very important for the emitter to consume as little power as possible. A wavelength of 810nm is particularly suitable in this regard because it provides high-contrast pictures of the irises of any color at comparatively low levels of light.

The SFH 4780S is Osram's answer to the notorious problem of a lack of space in mobile devices. Whereas current designs often use several IREDs, the high radiant intensity of this new IRED enables the iris scanner to operate with only one compact emitter. Like all applications in which the eye is exposed to infrared light, iris scanners must comply with the relevant eye safety standards.