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5 / 192018-08-16 | Document No.: AN097
To simplify and optimize the overall system a single high-power 810 nm
illumination module is best suited for all possible eye colors to unveil the rich
structures of the human iris. It also allows the use of narrow optical bandpass
filters in the camera module to maximize the signal-to-noise ratio of the iris scan
pattern in high-brightness environments (e.g. sunlight). Usually the optical
bandpass is either integrated into the camera module or positioned on top of the
camera (below the cover glass).
A single 810 nm emitter is a clear advantage compared to the more “old-
fashioned” (traditional) approach of using e.g. two emitters to create a
broadband illumination source between 700 nm and 900 nm.
Additionally, to get the best signal quality and to avoid unintended direct
reflections from the surface of the eye a slightly tilted emitter in the range of 5°
to 10° (e.g. 8°) might be favorable, depending on the overall system design. To
achieve this tilt, the SFH 4780S can be mounted on a tilted PCB (see option 1 in
Figure 1B) or a light bending wedge made e.g. made out of glass or other
materials. Also, special foils can be fixed on top of the IR-LED to achieve the
required light bending (see option 2 in Figure 1B).
In general the radiation characteristics of the SFH 4780S already matches the
single eye iris scanning requirements. Adding a proper optics can create any
desired illumination pattern in case it is required.
Iris recognition software
A suitable (custom) software extracts the unique pattern of the human eyes,
encodes them (e.g. into a 2048 bit code) and conducts a matching procedure (to
e.g. grant access). This all can be performed within a second or less, faster and
more secure than a four-digit password-based system. Typical camera features
are: Resolution > 1 Mpixel, > 10 pixel / mm.
B. SFH 4780S
The SFH 4780S is a high-power, narrow-angle 810 nm emitter. It features the
unique OSRAM Opto Semiconductors nanostack technology to match the iris-
scanning requirements, such as
• High irradiance level: high quality pictures even in bright sunlight conditions
• Narrow emitting angle: focus illumination on the eye area between 10 cm
to 40 cm
• Infrared wavelength of 810 nm: minimized corneal specular reflections
• Narrow spectral width (FWHM ~ 30 nm): allows narrow optical filters for
high iris picture quality
• Black and compact component body: suitable for harmonic/ discreet
industrial design