Light sensors smarten smart phones with smaller apertures

July 21, 2016 // By Graham Prophet
TMD2620 proximity sensors and TMD2725 ALS modules, by Austrian mixed-signal IC house ams, reduce LED emitter-to-sensor gap to just 1.0 mm while eliminating the effect of optical cross talk; the devices provide proximity sensing and proximity/ambient light sensing modules enabling smartphone manufacturers to reduce the sensor aperture in the display’s cover glass to its smallest diameter.

Use of the TMD2620 proximity sensor or the TMD2725, a combined proximity and ambient light sensor, enables phone manufacturers to reduce the aperture’s size by as much as 50%, improving aesthetic appeal, especially in devices with a white or light-coloured bezel. The TMD2620 and TMD2725 enable aperture size as small as 1.4 and 2.0 mm respectively.

 

The TMD2620 and TMD2725 feature a breakthrough in optical module packaging which allows the emitter – an infra-red (IR) LED – and photodiode to be placed just 1.0 mm apart. Lenses on top of the emitter and sensor along with an optical barrier between them help to minimize crosstalk, caused by reflections from the surfaces of the cover glass. Offset adjustment registers eliminate the effect of any residual crosstalk from the module’s proximity calculations. Automatic ambient light subtraction further enhances the accuracy of the device’s proximity measurements. The ability to measure up to a range of 100 mm is comparable to laser-based solutions.

“Until now, inability to overcome the effects of optical crosstalk have prevented android phone manufacturers from reducing proximity sensing apertures below 3.0 mm”, said Herbert Truppe, Senior Marketing Manager at ams. “Now the TMD2620 and TMD2725 overcome those challenges and enable a smaller aperture than has previously been possible.”

 

Pricing is $0.36 for the TMD2620, and $0.43 for the TMD2725 (1000).

 

ams; www.ams.com/proximity-detection/TMD2620 / www.ams.com/ambient-light-sensors/TMD2725