ams shrinks distance measurement and proximity sensing sensor

Claimed to be the world’s smallest 1D time of flight sensor (ToF), the TMF8701 has been introduced by ams.

The integrated 1D time-of-flight distance measurement and proximity sensing module can implement presence detection, for example to trigger the operation of a facial recognition system when a face is in range.

The TMF8701 is supplied in a 2.2 x 3.6 x 1.0mm package, and fits in a narrow smartphone bezel, for widescreen phone designs that have a high display screen to body ratio.

The TMF8701 sensor integrates a vertical-cavity surface-emitting laser (VCSEL) infra red emitter, multiple single photon avalanche photodiode (SPAD) light detectors, time-to-digital converter and a histogram processing core. The device implements all histogram-based presence detection, distance measurement and proximity sensing algorithms on-chip.

The sensor separately identifies reflections from fingerprint smudge contaminations on the display screen and optical reflections from objects beyond the cover glass, such as the user’s face, maintaining reliable performance even when the sensor’s aperture is dirty.

The Class 1 Eye Safe VCSEL emitter is immune to interference from ambient light and produces accurate distance measurement in all lighting conditions, claims ams. The module achieves accuracy of ± five per cent when measuring distance in the 200 to 600mm range in normal lighting conditions. Even in bright sunlight (100klux), ± five per cent accuracy is maintained at a range of up to 350mm.

The TMF8701 draws just 940 microA in proximity sensing mode when sampling at 10Hz. It is always on, to trigger the higher-power face recognition system to start up when the ToF sensor detects the presence of an object up to 600mm from the display screen.

The proximity sensing capability of the device can also be used to trigger the display and face recognition system to switch off when detecting a reflective surface at a distance of 0 to 100mm from the screen.

The accuracy of the TMF8701’s distance measurements also supports the selfie camera’s laser detect auto-focus (LDAF) function, especially in low-light conditions, adds ams.

The TMF8701 ToF sensor is in mass production now.

An evaluation kit is available.

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