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8 / 192018-08-16 | Document No.: AN097
Figure 7: Percentage of optical power within a given 100 nm wavelength range. This is
for a standard SFH 4780S with centroid wavelength of 810 nm and FWHM of 30 nm.
Thermal effects are not considered
As the data in Figure 7 suggests, the SFH 4780S is an excellent single emitter fit
for the NIST mobileID “best practices report” (SP 500 — 280) recommendation.
It is also an excellent candidate for the requirements from the Universal
Identification Authority of India (UIDAI) and its requirements.
2
Optical bandpass filter
To determine the required passband of the optical bandpass filter the following
typical key factors need to be considered:
• Centroid wavelength (810 nm ±13 nm)
• Operating condition (on-time and drive current)
• Ambient/ junction temperature
• Angular dependent shift of optical filter passband
Note that the FWHM (the actual spectral shape and width) depends on junction
temperature and drive current of the IR-LED. Figure 6 in combination with Figure
and Figure 9 give a good indication of the basic relationships.
1.Note that the data does not include the typical manufacturing distribution
(λ
centroid
± 13 nm) as well as spectral changes due to ambient respectively the compo-
nents junction temperature.
2. Please note that this requirements are not 100% fulfilled by the SFH 4780S. OSRAM
Opto Semiconductors considers the properties of the SFH 4780S in combination with a
suitable camera/ software to be superior to the UIDAI requirements.
Wavelength range [nm]
Percentage of total power [%]
60
40
0
650-750 700-800 750-850 800-900 850-950
100
80
20