Osram Opto Semiconductors GmbH of Regensburg, Germany says that the principal application of its new IR Oslux SFH 4780S (its first infrared emitter with a wavelength of 810nm) is biometric unlocking of cell phones and tablet computers. With a height of only 2.4mm, the LED achieves record radiant intensity values with a narrow emission angle from very small dimensions. This combination paves the way for compact energy-saving designs for reliable iris scanning functionality on mobile devices, says the firm.
Biometric identification methods for cell phones and tablet computers are becoming popular as these devices are being used increasingly 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 is the first IRED in the new high-performance Oslux package. “Oslux LEDs have long been established for visible lighting applications in mobile devices, such as camera flash,” says Sevugan Nagappan, product marketing manager for infrared. “We are now extending the range to include infrared emitters.”
Picture: The 2.4mm-high, 810nm-wavelength SFH 4780S LED.
A special feature of Oslux is the flat component surface despite the use of a lens. By matching the lens to the internal reflector, Oslux components have a very narrow emission beam angle of +/-10° at a low height of just 2.4mm so they provide optimum performance, says the firm. Despite its compact size of 3.5mm x 3.5mm x 2.4mm, the SFH 4780S achieves 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. Due to its black package, the SFH 4780S can be integrated completely unobtrusively behind the covers of mobile devices.
For mobile device applications, it is important for the emitter to consume as little power as possible. A centroid 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.
Osram says that the SFH 4780S is its answer to the notorious problem of a lack of space in mobile devices. Whereas existing designs often use several IREDs, the high radiant intensity of the new IRED enables the iris scanner to operate with only one compact emitter.
