PCA-RECT: An Energy-efficient Object Detection Approach for Event Cameras

We present the first purely event-based, energy-efficient approach for object detection and categorization using an event camera. Compared to traditional frame-based cameras, choosing event cameras results in high temporal resolution (order of microseconds), low power consumption (few hundred mW) and wide dynamic range (120 dB) as attractive properties. However, event-based object recognition systems are far behind their frame-based counterparts in terms of accuracy. To this end, this paper presents an event-based feature extraction method devised by accumulating local activity across the image frame and then applying principal component analysis (PCA) to the normalized neighborhood region. Subsequently, we propose a backtracking-free k-d tree mechanism for efficient feature matching by taking advantage of the low-dimensionality of the feature representation. Additionally, the proposed k-d tree mechanism allows for feature selection to obtain a lower-dimensional dictionary representation when hardware resources are limited to implement dimensionality reduction. Consequently, the proposed system can be realized on a field-programmable gate array (FPGA) device leading to high performance over resource ratio. The proposed system is tested on real-world event-based datasets for object categorization, showing superior classification performance and relevance to state-of-the-art algorithms. Additionally, we verified the object detection method and real-time FPGA performance in lab settings under non-controlled illumination conditions with limited training data and ground truth annotations.Comment: Accepted in ACCV 2018 Workshops, to appea

Configuration of Probe Tones for MKID Readout with Frequency Sweeping Scheme

International audienceWe are developing detector arrays using microwave kinetic inductance detectors (MKIDs) for astronomical observations in the 100-GHz band and a readout system for MKID arrays with frequency sweeping scheme. Probe tones in this scheme are generated and acquired by a frequency sweep probe (FSP) which is a digital fast Fourier transform spectrometer (FFTS), while the probe tones are converted and modulated by an intermediate frequency (IF) section. Since the values of the resonance frequencies change under different photon backgrounds, an appropriate method to configure the probe tones is essential to preserve the dynamic of the detected signals. We considered a general IF section which is a cascade of up/down converter pairs and found that its characteristics can be described with the base band, the target band, the sign of probe tone order, and the sign of frequency sweep direction. We implemented an algorithm to make a list of tone frequencies from a list of resonance frequencies given. Using this configuring method, we assembled IF sections for an antenna-coupled MKID array and for a LEKID array and set up a prototype FSP. The resonance frequencies of the antenna-coupled MKIDs and the LEKIDs are at 4.6–5.1 GHz and 0.6–1.0 GHz, respectively, and their spectra were obtained successfully. The method enables us to configure the readout system for both types of arrays