With billions of sensors already being deployed in all types of devices
and applications, the sensor revolution is well underway. Through the
Internet of Things (IoT) and the Internet of Everything (IoE), smart
sensors have the potential to significantly help our societies resolve
countless global challenges. In order to do so in a timely manner,
major advancements are required in the development of ultra-efficient
sensors
Leddar Technology Overview
Leddar® (acronym for light-emitting diode detection and ranging) is a patented sensing technology developed by LeddarTech, a successful spin-off of Canada's leading optics and photonics research institute, Institut national d'optique (INO). The main innovation behind this new approach lies in the superior signal processing that drives every Leddar sensor. Combined with the use of visible or infrared LEDs to perform time-of-flight measurements, Leddar technology provides continuous, rapid and accurate detection and ranging, without any moving parts.What Makes It Better?
Contrary to collimated emitters (lasers), the Leddar sensor's LEDs and emitter optics are used to create a diffuse beam covering a wider area of interest. The receiver collects the backscatter of the reflected light from objects in the beam and, using full-waveform analysis, detects the presence of objects in each segment of the beam, measuring the distance of the detected objects (based on the time taken by the light to return to the sensor). Accumulation and oversampling techniques are used to maximize range, accuracy and precision.Time-of-Flight Principle
Leddar sensors use LEDs to generate very short light pulses, typically 100,000 pulses per second. The time-of-flight (ToF) principle essentially consists in measuring the time taken by a light pulse to travel from the sensor to a remote object and to return to the sensor. The range R of the detected object is deduced from the measured full round-trip time T of the light pulse using the simple relation R = c T / 2 n, where c is the speed of light in vacuum and n denotes the refractive index of the medium in which the light pulse propagates.
Beam Pattern for Multi-Element Option
The multiple-element photodetector has a rectangular sensing area. The purpose of the emission optics of a Leddar sensor is to direct as much of the emitted light from one or more LEDs into a pattern that best fits the photodetector geometry. The purpose of the reception optics is to collect the backscatter of light from objects in that beam onto the photodetector. The combined emission and reception optics solution can be designed to obtain different beam widths. Currently, optics options with beam widths of approximately 9°, 18°, 24°, 34°, 45° and 95° are available on the multi-element option (the single-element option comes with a narrow 3° beam). Figure 2 illustrates a simulated emission beam pattern of a Leddar® sensor with an overlay of the matching segments provided by the reception optics corresponding to the photodetector elements.
How Does It Work?
The LED source is pulsed at a rate of approximately 100,000 pulses per
second. The light pulses propagate through the detection area and
reflected light is captured by the optics and the photodetector. The
sensor signal is amplified, and the signal acquisition is synchronized
to the pulses.
Detection and Distance Measurement
The detection and distance measurement is performed by the sensor's processor, using the acquired signals (one per photodetector element). The signals consist of a series of values representing light amplitude at incremental distances from the sensor. The number of samples in the signal is chosen according to maximum range required.
Conclusion
This innovative core technology is giving rise to the creation of a completely new generation of ultra-efficient smart sensors, greatly changing the way detection and ranging capabilities are integrated into a wide range of industries and applications. Not only can it make these functions more accurate, more reliable and more robust, but it can also make the entire solution more cost-effective, which will be vital in the deployment of profitable high-volume applications. By providing these important characteristics, Leddar is poised to become a key enabler in the smart sensor revolution.For more information on this patented* technology, visit leddartech.com.
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