Resource-Constrained Human Presence Detection for Indirect Time-of-Flight Sensors

Caterina Nahler, Hannes Plank, Christian Steger, Norbert Druml

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review


Face recognition with LiDAR and Time-of-Flight sensors is increasingly used in smartphones to automatically unlock devices when the user is present. The problem is that the presence of the user has to be detected before the energy-intensive face recognition can be started. This work presents a solution by introducing an energy-efficient measurement method for indirect Time-of-Flight sensors, which includes an on-chip processing method to detect the user's presence directly on a Time-of-Flight image sensor. The presented method is based on histogram analysis of direct reflectance images. The unique use of direct reflectance images is a significant enabler as it reduces histogram variations. Therefore our method outperforms conventional histogram detection methods and enables low-power on-chip face detection. It further enables the Time-of-Flight sensor to notify the smartphone application processor to perform the actual face recognition for device unlocking. We show in our evaluation that our method just has a false-positive rate of 17%, while all faces were detected. This is very promising since our measurement method reduces the processing cost which might lead to vast power savings in a future smartphone generation.
Original languageEnglish
Title of host publicationDICTA 2021 - 2021 International Conference on Digital Image Computing
Subtitle of host publicationTechniques and Applications
EditorsJun Zhou, Olivier Salvado, Ferdous Sohel, Paulo Vinicius K. Borges, Shilin Wang
Number of pages5
ISBN (Electronic)9781665417099
Publication statusPublished - 2021
Event2021 Digital Image Computing: Techniques and Applications : DICTA 2021 - Hybrider Event, Austria
Duration: 29 Nov 20211 Dec 2021


Conference2021 Digital Image Computing: Techniques and Applications
Abbreviated titleDICTA 2021
CityHybrider Event


  • Always-on
  • Face detection
  • Histogram
  • Histogram intersection
  • Reflectance
  • Time-of-Flight
  • ToF

ASJC Scopus subject areas

  • Artificial Intelligence
  • Signal Processing
  • Computer Vision and Pattern Recognition
  • Computer Science Applications


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