Swiss developer ActLight has developed a tunable CMOS photodiode to enable low light operation of LiDaR sensors in the Internet of Things (IoT).
ActLight operates in the Internet of Things (IoT) market with a focus on mobile and wearable devices, healthcare / medical technology, autonomous driving, drones and robotics.
Single-photon diodes used in smartphones lidar scanners to create 3D maps of the surrounding space and enable AR applications are too sensitive to ambient light. The Dynamic PhotoDiode (DPD) measures the absolute depth in weak light and also allows depth measurement in bright light. This is done by adjusting the sensitivity of the photodiode to an appropriate level and thus preventing it from saturating in bright light. The tuning is done by setting the bias on the photodiode.
Instead of using DC bias, the DPD operates at pulsed voltages: the applied voltage is switched from reverse to forward bias. This forward bias induces a large forward current after a time delay, so called triggering time, which depends on the light intensity. This way, we measure the delay time of the large forward current instead of the small photocurrent magnitude.
The large output signal means the DPD does not require any amplifier, and it can be directly connected to digital circuits. This boosts the performance and allows the front-end circuits to be integrated on the same chip, reducing the silicon area and the cost.