In the FWF funded project ”Interferometric Distance Sensing Using APDs and SPADs” we aim for achieving outstanding distance precision together with a long measurement range. While interferometric measurement approaches allow distance precision in the micrometer range and even below, the low optical power, received for longer distances, typically limits the range and also the precision of such approaches.

In this project we develop and investigate sensor chips containing correlators and single-photon detectors. These single-photon detectors allow increasing the sensitivity of such sensors by 3-4 orders of magnitude [1]. This allows to either reduce the optical power of the light source by 3-4 orders of magnitude while still achieving the same distance precision, or to extend the measurement range from, which still sufficiently high optical power is received by a factor of 30-100.

Additionally, we build and investigate laser sources for interferometric and time-of-flight measurement approaches within this project. Among these laser sources we developed a frequency-modulated continuous-wave laser that allows distance precisions in the range of micrometer while having a measurement range of more than 30 m. By using innovative real-time control mechanisms, affordable laser diodes can be used and the setup can be kept compact and robust [3].

The following Figure shows one of the test chips designed within this project containing a single-photon detector, an active quenching circuit that biases and controls the single-photon detector and two correlator blocks. This chip can be used as detector for interferometric as well as time-of-flight measurement systems [1].

Image of a microchip


Digital correlator with integrated single-photon detector and the corresponding biasing circuit (active quencher)


  1. Alexander Kuttner, Michael Hauser, Horst Zimmermann, and Michael Hofbauer, “Highly sensitive indirect time-of-flight distance sensor with integrated single-photon avalanche diode in 0.35 µm CMOS,” IEEE Photonics Journal, vol. 14, no. 4, (2022), pp. 1–6, doi: 10.1109/JPHOT.2022.3182153.
  2. Michael Hofbauer, “Precise distance measurement with thick SPADs,” In proceedings of International SPAD Sensor Workshop, invited talk, 2022, p. 30.
  3. Michael Hauser and Michael Hofbauer, “FPGA-based EO-PLL with repetitive control for highly linear laser frequency tuning in FMCW LIDAR applications,” IEEE Photonics Journal, vol. 14, no. 1, (2021), pp. 1–8, doi: 10.1109/JPHOT.2021.3139053.
  4. Alexander Kuttner, Michael Hauser, Alija Dervic, Horst Zimmermann, and Michael Hofbauer, “SPAD based digital photon counting optical distance sensor in 150 nm CMOS using indirect multiphase time-of-flight,” 2021 44th International Convention on Information, Communication and Electronic Technology (MIPRO), 2021, pp. 1765–1770, doi: 10.23919/MIPRO52101.2021.9597003.
  5. Michael Hauser, Alija Dervic, Alex Kuttner, Horst Zimmermann, and Michael Hofbauer, “Time of flight analog correlator for distance measurement with SPADs,” 2021 44th International Convention on Information, Communication and Electronic Technology (MIPRO), 2021, pp. 1771–1776, doi: 10.23919/MIPRO52101.2021.9597003.



This research was funded by AUSTRIAN SCIENCE FUND, grant number P30927-N30.