Politecnico di Torino - Corso Duca degli Abruzzi, 24 - 10129 Torino, ITALY

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Diffuse OpticsGated-mode SPADNear Infrared SpectroscopySingle-photon DetectorsTime-of-flight Imaging


The invention consists in a novel architecture for a solid-state photodetector, featuring single-photon sensitivity, wide photosensitive area (> 1 mm2) and fast “gating capability”. This photodetector can be switched between its OFF state (no photon can be detected) and ON state (photons can be detected) extremely quickly (few hundreds of picoseconds), thus enabling a precise “time-domain” filtering of the incoming light signal (e.g. very useful in applications like near-infrared functional brain imaging). The active area can be adjusted by selecting which microcells are enabled.

Technical features

The device is composed by a bidimensional array of “microcells” based on Single-Photon Avalanche Diodes (SPADs), with integrated time-gating circuits and read-out electronics. The chip may also include electronics for photon counting, for photon timing, for time filtering (e.g. to record the time-of-flight or fluorescence time constant), for correlating photons, for selecting photons, etc. The invention is also related to a method for dynamically controlling the effective photosensitive area of the detector, by selectively turning ON or OFF a subset of microcells, in order to adjust and equalize the signal level needed for further data processing (e.g. Time-Correlated Single-Photon Counting technique) or to select the overall detector sensitivity and sensitive area.

Possible Applications

  • Near-infrared spectroscopy;
  • Time-resolved diffuse optics;
  • Functional brain imaging;
  • Non-invasive biomedical diagnosis;
  • Optical mammography;
  • Food and pharmaceutical quality assessment;
  • Time-of-flight and 3D imaging;
  • LiDAR.


  • High dynamic range measurements;
  • High signal-to-noise ratio (SNR);
  • Extremely high sensitivity;
  • Fast time gating for photon time filtering;
  • High temporal resolution;
  • Single-chip solution for portability;
  • Adjustable active area size.