Making Sensors More Sensitive

Digital sensors have limits in the range of values that they are capable of detecting. Whether it is a camera, microphone, seismometer, ultrasound system, or other device, there is a point at which they can no longer capture useful readings. The reason for these limitations, in many cases, is the analog-to-digital converter (ADC) that they use to translate their inputs into digital signals.

ADCs operate within a certain range of voltages, and when incoming signals exceed the upper limit, the sensor reaches saturation. When beyond the point of saturation, a sensor can no longer differentiate between varied input intensities. A team of researchers from Imperial College London and Technical University of Munich have developed a new technique that can bypass these limits.

To accomplish this, the team modified a traditional ADC. Such ADCs convert an incoming voltage level directly into a corresponding output digital signal. In contrast, their prototype device was built with a custom algorithm that applies a modulo function to the input (which is the remainder of the division of the input voltage by the chip’s maximum voltage), and effectively “folds” the signals into smaller ones once the maximum voltage of the ADC has been reached. This allows the ADC to process a much wider range of data than was previously possible. The researchers suggest that there may be no limit to this approach, and that it could allow converters to process signals that far exceed their voltage limits.

The potential applications for this technique are very broad, as the technique is adaptable to a plethora of sensors. It could be quite useful for self-driving car applications, for example, where sudden darkening, as with driving through a tunnel, can cause a temporary loss of visual information with most cameras. Many uses for the technology also exist in medical imaging, weather forecasting, and bioengineering.

The solution devised by the research team is relatively simple, which just goes to show that it is not always the most complex solution that proves to be the most useful. ADCs running the team’s algorithm may change the future landscape of digital sensing.