Osram ambient light sensor adjusts display brightness
High-precision ambient light sensor - the sensor that works like a human eye
Osram Opto Semiconductors is the first semiconductor manufacturer to suc-ceed in producing a sensor that precisely matches the sensitivity curve of the human eye. This new product is called ambient light sensor SFH 5711. It en-ables the brightness of displays for example to be adjusted more precisely than ever before and headlights to be switched on and off automatically, all on the basis of ambient light conditions. Logarithmic amplification of the SFH 5711 allows the entire brightness range to be covered with high precision.
Like the human eye, the SFH 5711 ambient light sensor has its maximum sensitivity at 560 nm. It is suitable for adjusting the brightness of displays and other such com-ponents for optimum readability in the available light and for switching headlights on and off depending on ambient light levels. In LCD displays the sensor prevents the rapid onset of eye strain – a common problem if the display is too bright in a dark room. Small mobile terminals such as mobile phones and PDAs will be easier to read in all lighting conditions and will consume much less power because the display will only be lit as required. This will be easier on the eyes and save battery power. With a supply voltage of 2.3 to 5 V the sensor is ideal for applications in mobile terminals and also for automotive applications.
The “human” properties of the SFH 5711 are thanks to a new material system. It re-places the traditional silicon and has a spectral sensitivity similar to that of the human eye. The logarithmic amplifier IC enables a large brightness range (3 lx to more than 30000 lx) to be detected with great accuracy without the need for various series re-sistors. These resistors are needed with linear detectors so that the sensitivity can be adjusted externally for different brightness ranges. The impressive accuracy of the SFH 5711 enables virtually infinite dimming of backlighting systems.
The new sensor also has low thermal coefficients. Measuring just 2.2 x 2.8 x 1.1 mm the SFH 5711 is also a useful SMT chip for small mobile devices.
The new sensor will detect all brightness ranges with great reliability and precision without the need for any additional circuitry. The brightness of displays can therefore be adjusted to the ambient light conditions whatever the level of available light – even twilight.
Osram Opto Semiconductors