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Overview of a Novel LED-Based Detection and Ranging Technology

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). This innovative approach, based

on the time-of-flight of light principle, has enabled the use of LED lighting, either in the visible or

infrared spectrum, for detection and ranging.

What Makes It Better?

Contrary to collimated emitters (lasers), the Leddar sensor’s LEDs and emitter optics are used to

create a diffused 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.

Leddar technology also allows for a high level of versatility, and a wide range of optics options

are available for the sensor modules, providing a variety of beam patterns for different needs.

For example, in response to current market needs, the technology is presently being offered in

the form of two main adaptable platforms: 1) a small and cost-effective single-element module,

which provides a narrow, yet conic beam that is particularly suitable for applications like level

sensing, proximity detection, etc., and a 2) multi-element module, which offers a much wider

beam and provides lateral discrimination abilities, suitable for applications that might

traditionally use laser scanners, or multiple sensors.

This unique sensing technology presents multiple advantages. The use of a diffused light beam

results in increased robustness of detection of specular surfaces. Another benefit is high

robustness of detection under harsh weather conditions such as rain or snow. Aligning the

sensor is also easier, which results in fast and simple installation. Additionally, the multi-element

receiver provides detection and ranging for multiple segments of the beam without any moving

parts. This makes for a more compact, reliable and rugged assembly, all of which translate to an

extended service life.

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

Summary of content (5 pages)

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WHITE PAPER Overview of a Novel LED-Based Detection and Ranging Technology 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).
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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. Depending on the characteristics of the target’s surface, the light pulse is either absorbed, totally reflected, or reflected diffusely.
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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. An oversampling scheme using multiple light pulses is implemented to improve the resolution of the acquired signal.
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170 165 Amplitude (count) 160 155 150 145 140 135 130 -5 0 5 10 15 20 Distance (m) 25 30 35 40 Figure 3. Sample trace, where the x-axis is a time axis, scaled into distance, and the y-axis is the light amplitude. Figure 3 illustrates a typical trace signal for one segment. In this example, the sensor is collecting light reflected back by two separate objects. Full waveform analysis performed by Leddar sensors provides the capacity to detect multiple objects in the same segment.
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Integrating with the Leddar Modules Because of their compact size and flexible interfaces, Leddar sensing modules can be easily integrated into any system, enabling developers and integrators to use this advanced method in their own products. The modules were designed to facilitate both mechanical and software integration. Namely, the included software development kit provides sample code for developers to quickly integrate sensor data into their application software.