Osram Opto Semiconductors GmbH of Regensburg, Germany says that, not only does its new infrared Oslon black SFH 4725S emit light at a wavelength of 940nm (making it virtually invisible to the human eye) but its black package reflects almost no ambient light. Together with its high optical output of almost 1 watt, the LED is suitable as a light source for covert surveillance.
Concealed security systems – such as those installed in banks, on machinery and at border controls – need to be designed so they are unobtrusive. This is a major challenge for IR illumination in such applications, because the 850nm LEDs that are most often used appear as weak dots of red light, especially in dark environments, says Osram Opto. The solution is to switch to a wavelength of 940nm, which the human eye is 130 times less likely to notice. Camera sensors, however, can easily detect this invisible radiation.
Picture: Oslon black SFH 4725S 940nm IR-LED.
The compact Oslon black SFH 4725S infrared LED provides 940nm light with high optical output of 980mW from an operating current of 1A. Behind this high performance lies Nanostack technology, in which Osram has succeeded in providing two emission centers in one chip, almost doubling the light output. The SFH 4725S achieves a radiant intensity of 450mW/sr at an emission angle of 90° and therefore provides what is claimed to be excellent illumination over the area being monitored. Radiant intensity (measured in milliwatts per steradiant) indicates the light output within a solid angle segment and hence defines the intensity of the light beam.
The black package ensures that the component is completely concealed behind the camera lens. “The 940nm SFH 4725S is a further addition to our Oslon black series for the security sector, which already includes 850nm versions with standard and Nanostack chips,” says Dr Jrg Heerlein, head of product marketing for industrial infrared components.
Osram Opto claims that, in the compact class, the Oslon is currently one of the most powerful versions for both visible and infrared illumination. Measuring only 3.85mm x 3.85mm x 2.29mm, the infrared Oslon components are among the smallest IREDs, with around 1W optical power, the firm adds. Its beam angle is +/-45°. “Users with experience in constructing visible lighting units can transfer their know-how and their processes directly to the infrared Oslon,” comments Heerlein. The market is also full of lenses that designers can use to shape the beam from the IRED to meet their specific requirements.
