Follow the LeddarReview of a Low-Cost Detection and Ranging Device

A 3.224Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE

LiDAR News recently obtained an evaluation kit from LeddarTech in Canada. We used the Leddar in several real-world test scenarios and collected some representative sample data. It’s not traditional LiDAR, but it is analogous in principle. The technology (emitter, photodetector sensing and ranging electronics) is quite similar. We looked at the capabilities and applications, checked the results and report on them in this brief review.

Quick Opinion
Using the Leddar was easy and a lot of fun. The software interface is well designed and simple to use (with a lot of underlying functionality). The product worked exactly as advertised (which is always a good thing). We were pleasantly surprised at the Leddar’s effectiveness in measuring to multiple, simultaneous zones (more on this later).

In-short, the Leddar is a specialized device that does a limited number of things, but does them extremely well. It is not a silver-bullet solution, but rather a very specific technology to solve some very specific problems in a reliable and accurate manner.

LeddarTech’s Background
LeddarTech was formed in 2007 around a technology spin-off from a leading Canadian optics research organization called Institut National d’Optique (INO) in Quebec City. LeddarTech acquired the rights to the technology and began to produce commercial-based sensors for many applications such as traffic management and speed and pedestrian detection. The company has a worldwide install base, with 40-50 cities in North America alone deploying the Leddar.

The Leddar evaluation kits were only recently made available to OEM customers and developers in the summer of 2013. More recently, LeddarTech has entered into an agreement with a driving assistance equipment manufacturer for a highly advanced application specific integrated circuit (ASIC) version of the Leddar for on-road obstacle detection and tracking by vehicles. In addition to driving assistance applications and vehicle detection, the Leddar may be a great technology for robotics (sense-and-avoid), security and monitoring. LeddarTech has exhibited at the AUVSI Unmanned Systems conference to promote the capabilities for unmanned vehicles.

"Enabling Modules"
According to Charles Boulanger, CEO LeddarTech, the Leddar technology is offered in the form of "enabling modules" which are complete standalone kits (like the one we tested). These units are designed to be rapidly integrated into more complex products and technology. The idea is to allow developers and brand-owners the ability to innovate, creating value within their own specialized markets according to their unique needs and based on their own specific knowledge and expertise.

This is a smart strategy as it is sort of "crowd-sourcing" within your customer base. By opening up the platform and making access to the technology easier (very low entry price), the company will likely benefit from novel and unique uses (developed by experts in their own vertical market), thereby expanding the scope of applications.

How it Works
The Leddar employs the same basic principles as LiDAR, namely light time-of-flight measurement. Instead of using a laser as the illumination source, the Leddar (in the EvalKit) uses two high-power light-emitting diodes (LED). The LEDs emit diffused light (uncollimated) over the area of interest within the infrared band (940nm). The LED’s are typically pulsed at 100 kHz, and the intensity can be either auto or manually controlled.

A series of 16 channels built on to a photodetector array collects the returned energy of the emitted light, reflected by objects within the fieldof-view (FOV). Each channel provides detection and range for (simultaneous) multiple objects. The position in the array of each element (1-16) determines the angle to the object detected, thereby enabling location relative to the sensor and other objects in the scene.

The 16 detectors are arranged such that the complete field of view through the lens is 45 horizontal (See Figure 2). Each segment has an 8 vertical FOV. Within each segment, multiple objects (multiple returns) can be detected and located simultaneously, as long as the distant objects are not 100% obscured by the near-field objects.

The company has published an interesting white paper which goes into greater depth on the anatomy of the Leddar technology. Additionally, there are more detailed explanations of much more advanced capabilities in the product documentation.

Form Factor and Attributes
The Leddar is light-weight and compact (114 x 76 x 45.3mm, 265g). It draws 4W continuous power at 24VDC. The EvalKit comes with an adapter to run off of 110VAC power. The Leddar is designed to operate in all types of weather. So, the specialized commercial units provided by LeddarTech are typically enclosed in an IP67 (or other enclosure type) water resistant housing for various applications. The EvalKit, on the other hand, is barebones and exposed so that full access to power ports, USB and SD card slots is available for developers and integrators.

Additionally, an 8-pin header block is supplied to interface to the Leddar for CAN Bus and RS-485. This allows for easier integration into vehicle and robotic systems. The housing on the EvalKit device (essentially just a cover on the backplane to the board) has several M3 machine threads for mounting in different orientations. At the bottom is a quarter-20 thread so that the Leddar can be mounted to a tripod or similar as seen in Figures 1, 3 and 4.

The LeddarTech EvalKit only scratches the surface of what’s available in the Leddar product line. According to the company, the base technology can be adapted for a wide variety of applications. Apparently, the modules can be tailored to have a different number of channels (detector array elements) such as 32 or even as little as a single channel. The beam area (FOV) can be customized to be anywhere from 9-95. Furthermore, the Leddar can be changed to use a different wavelength of emitted light and the pulse rate can be varied as well.

According to LeddarTech, they have designed the firmware and software to be scalable and flexible so that a wide range of hardware configurations can be implemented. The company says that this allows their engineers to tailor the technology to specific customer applications.

User Configurable, Extended Functionality
Underlying the simple interface of basic functions is a suite of sophisticated tools to refine the data collection parameters for specific needs and environments. We explored a few briefly. However, there are too many to comment on in this short review. One extended function we looked at, but do not include in the test section, is the Advanced Zone Detection tool. This feature allows the user to set-up a very complex set of detection and range rules. It employs things like Boolean operators and programming condition statements to restrict data collection to specified user parameters. We recommend getting in touch with LeddarTech customer support directly for more information on this capability

Special Algorithm
The company claims that what really makes the sensor unique is the way they handle the algorithms. The approach to controlling light pulses as well as oversampling and signal accumulation allow the sensor to achieve really good accuracy and range, all while consuming very little power.

The user guide that accompanies the EvalKit for developers has extensive explanation of the signal accumulation in waveform sampling. It is very interesting, especially for special applications where the sensor might require tweaking and customization.

The Testing
As in past reports, to ascertain the easeof-use of the product, we let a complete "noob" (the author of this review) try his hand at running the Leddar. Test protocols were not exhaustive by any means, but rather targeted at verifying the primary functions and capabilities of the device. To keep it simple, we looked at several non-complex scenarios: 1) people entering/exiting a doorway, 2) scanning a planar surface to look at any potential jitter in the range values, and 3) detecting and logging ranges from vehicles travelling on a local side street.

Test 1. In this case (and all test cases for that matter), The Leddar performed exactly as depicted in the YouTube Videos. For the first battery of quick checks, we positioned the sensor across from a door to a stairwell. When test subjects walked across the 45 beam path, a corresponding shift was observed in real-time in the data display window of the laptop we used. As the subjects crossed from one array element to the next, the position was accurately tracked and displayed on-screen. We were also able to see shifts in the corresponding element indicators that represented the surface of the door as it was opened and then swung closed.

Test 2. For this trial, we pointed the Leddar at a projection screen (see Figure 4: Set-up of Leddar and camera oriented towards side-street Figure 3) which provided a relatively uniform reflective surface. The distance from the planar surface was slightly less than 2m in order to allow all 16 elements of the photodetector array to "see" the narrow screen (and not fall on to surrounding, less uniform surfaces of the wall). The hanging screen presented a much flatter, consistent surface than any of the drywall or other possible targets we looked at.

The Leddar software has a feature that allows the user to select a small pop-up window to view the raw range values in real-time. The window appears in conjunction with the graphical display which depicts the range values as green bars within each lateral array element as seen in Figure 3. We observed that the range values did not fluctuate (range values are shown to the nearest centimeter), even though the amplitude (of the return signal) jittered somewhat.

Using a steel tape, we measured the distance from the reference point at the bottom of the Leddar housing to the surface of the screen, trying as carefully as possible to keep the tape perpendicular to the Leddar and the screen. While this is admittedly an inexact approach, we were able to consistently obtain distance measurements that agreed well within 5mm with those listed in the raw range window. These values easily met the accuracy stated in the documentation.

Test 3. This was the most interesting and challenging test due to the more complex, less controlled environment of the local side-street. We set-up the Leddar co-mounted with a camera on a tripod and aimed it at the street. The height of the lens was approximately 1.6m above ground and about 15m from the nearest curb (See Figure 4). The objective was to detect and measure ranges from passing vehicles.

While we were optimizing the FOV, several trucks parked across the street and can be seen in Figure 5. Subsequently, a garbage truck passed through the FOV and we were able to collect detection/ range data from the side of the vehicle as seen in Figure 6. As the large truck passed through the FOV, we observed a "slug" of green bars moving across the 45 angle depicted in the monitor window, corresponding to the range and lateral position changes within the detector elements. Using some simple trigonometry, and assuming the truck was perpendicular to the center detector/range element, then we can estimate the length of the truck at about 7 meters or so.

Future Testing
There are many areas of interest we would like to explore with the Leddar. For this brief tech review, we barely touched on the many features available to those with more sophisticated applications and expertise. A second phase of follow-on testing might be interesting to undertake and then possibly report in a future article. Here are some ideas that might be worth evaluating:
Rotate 90 and measure height profiles of passing vehicles
Try measuring stockpiles
Try attaching an inexpensive direct-georeferencing/odometry system and try roadway crown and shoulder fall-off profiling
Integrate with an Arduino board for sense-and-avoid on robots
Use as a speed detection device for speeding traffic

Summary and Conclusion
Overall, the Leddar EvalKit did what it was supposed to do. From our limited testing, it was clear that the capabilities right out-of-the-box were more than enough for a developer, and in fact would suffice for immediate integration into real-world projects and applications. We were very pleased with the responsiveness of LeddarTech customer support. Any questions regarding operation, performance or specifications were immediately answered, in-depth. Additionally, as we are looking at integrating an Arduino board for future work with the Leddar, customer support staff provided us detailed documentation, software links and recommendations to assist us.

The Leddar product (in the form of the EvalKit) is a very useful and reliable device. At the low price point, it is highly recommended for those interested in exploring a cost effective means for project development and for experimenting with detection and ranging technology.

Bill Gutelius is the President and co-founder of Active Imaging Systems (AIS). In 2007 he formed AIS where he consults for commercial and government clients on active and passive imaging technologies and their applications.

Fast Facts

$299 price (EvalKit)
LED, Solid-State (no scanners)
Eye-safe (IEC 62471-2006 exempt)
Intuitive UI software
Low power consumption (4W)

Quick Specs
100kHz LED pulse rate
45 x 8 field-of-view
5cm accuracy, 1cm resolution
50m max range (cooperative target)
940nm wavelength
265g weight

A 3.224Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE