Depth sensor filters out ambient infrared light for outdoor use

Researchers at MIT have developed an infrared depth-sensing system built from a smartphone with a laser attached that can work outdoors as well as in, which could be beneficial for future field activities.

04/08/2016


CSAIL researchers at MIT are presenting a new infrared depth-sensing system built from off-the-shelf components, that works outdoors as well as in. Courtesy: Christine Daniloff, MITThe Microsoft Kinect was a boon to robotics researchers. The cheap, off-the-shelf depth sensor allowed them to quickly and cost-effectively prototype innovative systems that enable robots to map, interpret, and navigate their environments.

However, sensors like the Kinect, which use infrared light to gauge depth, are confused by ambient infrared light. Even indoors, they tend to require low-light conditions, and outdoors, they're hopeless.

At the International Conference on Robotics and Automation in May, researchers from MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) will present a new infrared depth-sensing system, built from a smartphone with a $10 laser attached to it, that works outdoors as well as in.

The researchers envision that cellphones with cheap, built-in infrared lasers could be snapped into personal vehicles, such as golf carts or wheelchairs, to help render them autonomous. A version of the system could also be built into small autonomous robots, like the package-delivery drones proposed by Amazon, whose wide deployment in unpredictable environments would prohibit the use of expensive laser rangefinders.

"My group has been strongly pushing for a device-centric approach to smarter cities, versus today's largely vehicle-centric or infrastructure-centric approach," said Li-Shiuan Peh, a professor of electrical engineering and computer science whose group developed the system. "This is because phones have a more rapid upgrade-and-replacement cycle than vehicles. Cars are replaced in the timeframe of a decade, while phones are replaced every one or two years. This has led to drivers just using phone GPS today, as it works well, is pervasive, and stays up-to-date. I believe the device industry will increasingly drive the future of transportation."

Joining Peh on the paper is author Jason Gao, an MIT PhD student in electrical engineering and computer science and a member of Peh's group.

Background noise

The researchers prototyped the sensor using the camera in an ordinary cellphone and a commodity laser emitter that costs about $10. Courtesy: Li-Shiuan Peh, Jason Gao, MITInfrared depth sensors come in several varieties, but they all emit bursts of laser light into the environment and measure the reflections. Infrared light from the sun or man-made sources can swamp the reflected signal, rendering the measurements meaningless.

To compensate, commercial laser rangefinders use higher-energy bursts of light. But to limit the risk of eye damage, those bursts need to be extremely short. And detecting such short-lived reflections requires sophisticated hardware that pushes the devices' cost into the thousands of dollars.

Gao and Peh's system instead performs several measurements, timing them to the emission of low-energy light bursts. Essentially, it captures four frames of video, two of which record reflections of laser signals and two of which record only the ambient infrared light. It then simply subtracts the ambient light from its other measurements.

In their prototype, the researchers used a phone with a 30-frame-per-second (fps) camera, so capturing four images imposed a delay of about an eighth of a second. But 240 fps cameras, which would reduce that delay to a 60th of a second, are already commercially available.

The system uses a technique called active triangulation. The laser, which is mounted at the bottom of the phone in the prototype, emits light in a single plane. The angle of the returning light can thus be gauged from where it falls on the camera's 2D sensor.

Global replace

At ranges of 3 to 4 m, the system gauges depth to an accuracy measured in millimeters, while at 5 m, the accuracy declines to 6 cm. The researchers tested their system on a driverless golf cart developed by the Singapore-MIT Alliance for Research and Technology and found that its depth resolution should be adequate for vehicles moving at rates of up to 15 km per hour.

Imminent advances in camera technology could improve those figures, however. Currently, most cellphone cameras have what's called a rolling shutter. That means that the camera reads off the measurements from one row of photodetectors before moving on to the next one. An exposure that lasts one-thirtieth of a second may actually consist of a thousand sequential one-row measurements.

In Gao and Peh's prototype, the outgoing light pulse has to last long enough that its reflection will register no matter which row it happens to strike. Future smartphone cameras, however, will have a "global shutter," meaning that they will read off measurements from all their photodetectors at once. That would enable the system to emit shorter light bursts, which could consequently have higher energies, increasing the effective range.

Massachusetts Institute of Technology (MIT)

www.mit.edu 

- Edited by Chris Vavra, production editor, Control Engineering, cvavra@cfemedia.com. See more Control Engineering process sensor and actuator stories.



The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by Control Engineering subscribers. Vote now (if qualified)!
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Maximize ROI with integrated control system approach; Microcontrollers vs. PLCs; Power quality; Accelerate and rewire IIoT; Traits for excellent engineers
HMI effectiveness; Distributed I/O; Engineers' Choice Award finalists; System Integrator advice; Inside Machines
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Programmable logic controllers (PLCs) represent the logic (decision) part of the control loop of sense, decide, and actuate. As we know, PLCs aren’t the only option for making decisions in a control loop, but they are likely why you’re here.
This digital report explains how plant engineers and subject matter experts (SME) need support for time series data and its many challenges.
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by Control Engineering subscribers. Vote now (if qualified)!
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Maximize ROI with integrated control system approach; Microcontrollers vs. PLCs; Power quality; Accelerate and rewire IIoT; Traits for excellent engineers
HMI effectiveness; Distributed I/O; Engineers' Choice Award finalists; System Integrator advice; Inside Machines
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Programmable logic controllers (PLCs) represent the logic (decision) part of the control loop of sense, decide, and actuate. As we know, PLCs aren’t the only option for making decisions in a control loop, but they are likely why you’re here.
This digital report explains how plant engineers and subject matter experts (SME) need support for time series data and its many challenges.
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by Control Engineering subscribers. Vote now (if qualified)!
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Maximize ROI with integrated control system approach; Microcontrollers vs. PLCs; Power quality; Accelerate and rewire IIoT; Traits for excellent engineers
HMI effectiveness; Distributed I/O; Engineers' Choice Award finalists; System Integrator advice; Inside Machines
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Programmable logic controllers (PLCs) represent the logic (decision) part of the control loop of sense, decide, and actuate. As we know, PLCs aren’t the only option for making decisions in a control loop, but they are likely why you’re here.
This digital report explains how plant engineers and subject matter experts (SME) need support for time series data and its many challenges.
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me