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June 4, 2021
Photo of: Past MSU Students in Lasers and Optics Research
Last year, a group of Montana State University students stumbled upon the need for a portable, low-cost LiDAR system for educational purposes. The Optical Remote Sensor Laboratory (ORSL) at MSU seeks to educate others on imaging technologies in applications such as precision agriculture and climate science. This innovative student research team worked together to develop an affordable, portable LiDAR rangefinder and the accompanying educational package for teaching LIDAR to future generations of learners.
A Capstone Project
The student's paper outlines that their design uses a “pulsed diode laser at 635 nm wavelength an optical receiver with a 2.5 cm diameter lens, interference filter, and photodiode. The detector signal is passed into a comparator, whose output is used to determine range with a time-to-digital converter chip and processed with a microcontroller. Range data is then displayed in a GUI on a laptop screen. The system was designed to detect the location of solid objects at ranges up to 10 m. The main source of cost reduction within the system is achieved by using a fully integrated time-of-flight chip as well as small low-cost optics.” The team employed a Quantum Composers Emerald 9250 digital delay pulse generator as their synchronizer, as it was able to provide multiple independent channels, 5ps timing resolution, and a high level of accuracy as compared to similar units.
Role of the Digital Delay Pulse Generator
The Emerald pulse generator was used to provide square wave signals to precisely coordinate the system device’s timing and display. With its four independent outputs, the Emerald generated multiple waveforms with a time delay between channels and a 5 ps resolution. Resolution and accuracy of the width, delays, and period counters allowed for 10 kHz square waves with an amplitude of 3.30 Vpp and offset of 1.65 V. They noted that “Three different ToFs were simulated with 5 measurements performed on each. The ToFs tested were 33.36 ns (10 m), 16.68 ns (5 m), 0.665 ns (20 cm).” Ranges were calculated in MATLAB and showed that the TDC/MCU combo could measure the minimum and maximum ranges required and those in-between with an absolute maximum offset of 1.5 cm, which met the specifications.
Conducting Research in a Pandemic
While the original project goal was to build a fully operational portable LiDAR rangefinder, COVID-19 impacted lab space and equipment availability, requiring the team to pivot by working remotely using whatever they had in terms of resources and equipment while social distancing. In the end, the students successfully identified, tested, documented subsystems, hardware, code, and documentation—all within budget—for the next set of researchers who are on track to complete the device this year.
These Montana State University students were able to meet challenges as well as excel in the face of unforeseen challenges in the integration, testing, and verification work on this complicated technology amid unusual circumstances. They in addition to the Montana State University staff serve as an outstanding example of the kind of ingenuity and perseverance that came from the COVID-19 challenges of the past year
About the Quantum Composers Pulse Delay Generator
Quantum Composers understands that researchers may have a variety of applications and projects and created a whole line of pulse generators to match the varied needs and budgets. The Emerald 9250 comes standard with a 280 ppb TCXO oscillator, giving the user a higher performance without extra cost.
Quick Specs
Channels: 4 Independent Channel Outputs
Resolution: 5ps
Accuracy: 1 ns + (0.0001 x delay)
Jitter: 15 ps + (1e-8 x delay)
Memory: 6 Storage Slots
Comm Ports: USB, Bluetooth (Optional)
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