Unlimited Sampling From Theory To Practice For Imaging, Audio, And Autonomous Cars

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Researchers developed a new technology that enables digital sensors like cameras to sense all light intensities.

Everyday image sensors or any other digital sensors like microphone, radars, ultrasound systems and seismic sensors are subject to saturation points. They cannot detect stimuli beyond certain physical limits.

Researchers from Imperial College London and Technical University of Munich have developed a technique that combined with new hardware and algorithms unleash the full potential of digital sensors like these.

Lead author of the research Dr. Ayush Bhandari from Imperial’s Department of Electrical and Electronic Engineering said: “We need sensors that capture the full range of what our environment has to offer, and there is boundless potential for sensors to measure signals beyond current human and technological limits.”

The sensing devices consist of analog-to-digital converters (ADCs) that convert information like light and sound from cameras and microphones into digital signals. However, ADCs are limited by some quantization voltage, and saturation occurs when an incoming signal exceeds those limits.

Dr. Bhandari added: “Our new technique lets us capture a fuller range of stimuli in countless examples of digital technology, with applications ranging from everyday photography and medical scanners to extra-terrestrial exploration, bioengineering, and monitoring natural disasters. The hardware-software co-design approach opens up new scientific frontiers for further research.”

The researchers experimented on ADCs that use ‘modulo’ (remainder produced when the voltage of a signal is divided by the ADC’s maximum voltage) sampling to check if a different type of voltage called moduli can  help sensors process a greater range of information. They built a prototype that switches the ADC to switch to modulo voltage once the stimulus limit is reached and ‘folds’ these signals into smaller ones. 

This allowed ADCs to process a much wider range of information. According to the researchers, it can even provide ‘unlimited sampling’ that accurately captures signals whose amplitudes far exceed ADCs’ voltage limits.

Study co-author and Dr. Bhandari’s undergraduate mentee at Imperial, Thomas Poskitt said, “By taking a modulo of the signal, we keep the voltage within the limit and reconstruct the full signal, even without knowing how many times the voltage has exceeded the limit. This can unlock a high dynamic range for any sensor which could, for example, allow cameras to see what humans cannot.”

Researchers believe that the applications of this technology range from consumer photography and scientific and medical imaging to space exploration.

The research appeared in the journal IEEE Transactions on Signal Processing.


 

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