New infrared LED offers reliable iris recognition for cell phones and tablet Computers – SFH 4780S
Thanks to iris scanners, Osram Opto Semiconductors is making it easier to protect mobile devices. The new SFH 4780S infrared LED (IRED) with a wavelength of 810 nanometers (nm) and very high radiant intensity enables high-contrast images of the eye to be captured using a single IRED. For the first time, this component therefore provides the basis for energy-saving and space-saving designs for implementing reliable iris recognition functionality in cell phones and tablet computers as a means of access control.
It is becoming more and more important to protect mobile devices against unauthorized access because people are increasing using their cell phones and their tablets for online banking, online shopping and other sensitive applications. Many manufacturers are using biometric methods to identify authorized users by their fingerprints or the characteristic patterns of their irises. Iris scanners illuminate the eyes with infrared light and capture an image of the iris with a camera. The characteristic features of the iris are detected and compared with the stored iris patterns of authorized users. This process is only reliable – in other words users are not incorrectly rejected or accepted – if the captured image has sufficient contrast. Designers therefore often use multiple emitters but the scanner then requires more space and more power. This is seldom a viable option for compact battery-operated devices such as cell phones and tablets.
Low-profile IREDs with record radiant intensity
Osram has solved this dilemma with high-efficiency chips, a new wavelength and a high-performance package. The wavelength of 810 nm is ideal for achieving high-contrast images of irises of any color with the minimum of light. The highly efficient thin-film chips are based on nanostack technology and have two emission centers per chip, offering a typical optical output of 680 milliwatts (mW) from a current of one ampere (A). A current of up to 2 A is permitted in pulsed mode. Osram has also adapted its successful Oslux package for visible lighting applications to the needs of infrared LEDs. The result is a low-profile emitter, only 2.4 millimeters high, which has an integrated reflector, an integrated lens and an emission angle of only 20 degrees. From a current of 1 A, the SFH 4780S achieves a typical radiant intensity of 2900 mW per solid angle – a value which beats all previous records for this geometry. The outstanding emission characteristic ensures that as much of the emitted light reaches the eyes as possible. Osram has succeeded in producing an IRED with a unique size/performance ratio which meets the special requirements for iris recognition in mobile devices.
Iris scanners expose the eyes to infrared light so they have to comply with the relevant eye safety standards. Information and implementation support is available for designers in an application note.