They enable Android smartphone manufacturers to reduce the sensor aperture in the display’s cover glass by up to 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 2mm respectively.
They also allow the emitter – an infra-red LED – and photodiode to be placed 1mm apart. Lenses on top of the emitter and sensor, along with an optical barrier between them, minimise 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 enhances the accuracy of the device’s proximity measurements. The ability to measure up to a range of 100mm 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 to less than 3mm”, 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.”