Fully Quantized Always-on Face Detector Considering Mobile Image Sensors
Haechang Lee Wongi Jeong Dongil Ryu Hyunwoo Je Albert No Kijeong Kim Se Young Chun
Despite significant research on lightweight deep neural networks (DNNs)
designed for edge devices, the current face detectors do not fully meet the
requirements for "intelligent" CMOS image sensors (iCISs) integrated with
embedded DNNs. These sensors are essential in various practical applications,
such as energy-efficient mobile phones and surveillance systems with always-on
capabilities. One noteworthy limitation is the absence of suitable face
detectors for the always-on scenario, a crucial aspect of image sensor-level
applications. These detectors must operate directly with sensor RAW data before
the image signal processor (ISP) takes over. This gap poses a significant
challenge in achieving optimal performance in such scenarios. Further research
and development are necessary to bridge this gap and fully leverage the
potential of iCIS applications. In this study, we aim to bridge the gap by
exploring extremely low-bit lightweight face detectors, focusing on the
always-on face detection scenario for mobile image sensor applications. To
achieve this, our proposed model utilizes sensor-aware synthetic RAW inputs,
simulating always-on face detection processed "before" the ISP chain. Our
approach employs ternary (-1, 0, 1) weights for potential implementations in
image sensors, resulting in a relatively simple network architecture with
shallow layers and extremely low-bitwidth. Our method demonstrates reasonable
face detection performance and excellent efficiency in simulation studies,
offering promising possibilities for practical always-on face detectors in
real-world applications.