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A long time ago, in a suburb far, far away…

“So, how would you kill mosquitoes with a laser?”

Nathan Myhrvold asked us. Lowell Wood, Rod Hyde, and I smiled. The three of us were meeting with Myhrvold in the fall of 2006, in an office at Intellectual Ventures Management, a company in Bellevue, Wash., that he founded in 2000 to create and invest in inventions. We smiled because we had just spent the afternoon arguing over that very question, scribbling ideas and calculations on a whiteboard, and had come up with what we thought was a pretty good answer: a “photonic fence” in the form of a row of vertical posts that would use optical sensors and lasers to spot, identify, and zap bad bugs on the wing.

The idea of building a high-tech defense against disease-carrying pests had come up in discussions that Myhrvold and Wood had been having with Bill Gates, who was Myhrvold’s boss when he was chief technology officer at Microsoft in the 1990s. Through the Bill and Melinda Gates Foundation, Gates has been trying to improve living conditions in some of the world’s poorest countries and in particular to come up with ways to eradicate malaria, a mosquito-borne disease that sickens about a quarter billion people a year and kills nearly a million annually, including roughly 2000 children a day (see Web-only sidebar, “ New Techniques Against a Tenacious Disease”).

Wood, a veteran of advanced weapons development at Lawrence Livermore National Laboratory, in California, and one of the scientists behind the Strategic Defense Initiative (otherwise known as “Star Wars”), had suggested trying a similarly high-tech approach against malarial mosquitoes—to take advantage of inexpensive, low-power sensors and computers to somehow track individual mosquitoes and shoot them out of the air. If it could be done cheaply enough, this might offer the first really new way in many years to combat malaria, as well as other diseases transmitted by flying insects, such as West Nile virus and dengue fever.

Hyde and I had worked with Wood at Livermore. Hyde now manages Intellectual Ventures’ stable of staff and consulting inventors, and he assigned me the challenge of making the idea work—or showing why it couldn’t.

Three years later, my colleagues and I at Intellectual Ventures have now worked out many of the trickiest aspects of the photonic fence and have constructed prototypes that can indeed identify mosquitoes from many meters away, track the bugs in flight, and hit them with debilitating blasts of laser fire. And we did it without a multimillion-dollar grant from some national Department of Entomological Defense. Nearly everything we used can be purchased from standard electronics retailers or online auction sites.

In fact, for a few thousand dollars, a reasonably skilled engineer (such as a typical IEEE Spectrum reader) could probably assemble a version of our fence to shield backyard barbecue parties from voracious mosquitoes. We therefore present the following how-to guide to building a photonic bug killer, in five parts: selecting an appropriate weapon, spotting the bugs, distinguishing friends from foes, getting a pest in your sights, and finally shooting to kill.

Why build a fence? You could try to lure bugs to one spot and kill them, but more will just keep arriving. For all practical intents, the supply of mosquitoes is infinite.

You could build a system that scans your entire yard for bugs. But as any infantryman knows, the first step in defense is to establish a perimeter; it’s much more effective (and safer) to concentrate your firepower in a narrow zone. Mosquitoes generally don’t spend their whole lives in your backyard, unless you live in a swamp. They fly back and forth from their breeding grounds, so to get to you they have to cross your laser-guarded perimeter. A few may fly over the fence, but not many. The average flying altitude varies among mosquito species but is usually only about 2 meters. They will fly over obstacles when necessary—even into an upper-story window—but if your virtual fence is 3 to 5 meters high, it can catch almost all mosquitoes that fly by.

Of course, there are any number of ways to build a fencelike barrier. You could detect mosquitoes acoustically, with radar, or with ultrasonic sonar. You could shoot them down with tiny bullets, break them apart with sonic pulses, or cook them with microwaves. We considered these and many other possibilities, but it’s hard to beat the range, precision, and literally lightning-fast response of optics. Good digital cameras and powerful diode lasers are relatively affordable and easy to find. So for us, photonic technology is the way to go.

Getting a bug in the crosshairs

To detect mosquitoes, you’ll need several video cameras—four per fence post for a full-coverage fence (two at the top and two at the bottom facing the two adjacent fence posts—see “Spot the Skeeter,” left). The cameras don’t have to be sharp enough to take a good photo of a mosquito many meters away, but they should have a resolution high enough so that a distant insect will at least fill up most of one pixel. If the bug occupies several pixels in the frame, that’s even better, as this will allow you to find its center. A 1.3-megapixel (1280- by 1024-pixel) camera turned sideways can cover a 4-meter-high fence post with pixels 3 millimeters on a side. If you’re economizing, you could even try VGA-resolution (640- by 480-pixel) cameras.

The speed of your cameras matters as much as the resolution. It’s no good if the bug is already through the fence by the time your system registers its presence. Mosquitoes fly up to a meter per second, so if the active zone is 10 centimeters wide, the frame rate must be more than 10 frames per second. Standard video cameras supply 30 frames per second, but the frames are interlaced—odd and even rows of pixels are delivered separately, 1/60 second apart—which will make it hard to follow a small moving object. So you’ll want to use noninterlaced cameras, or at least units on which you can disable the interlacing.

You’re interested only in a narrow vertical strip of image, less than 100 pixels wide, so you can drastically cut down the amount of data your cameras produce if you capture only that strip. Many digital video cameras allow you to do this by selecting a rectangular “region of interest.” Using less than the full frame may also let you increase the frame rate.

Next you need to get all those pixels into a computer. Not only do you need a high data rate but also low latency—as little delay as possible between the moment the pixels are captured and when they’re available for processing. USB connections are probably too slow; we’ve found that IEEE 1394 (FireWire) or gigabit Ethernet interfaces work fine. (Best of all would be to create a custom image-processing chip and integrate it directly into the camera. But that’s a different project.)

Mosquitoes are dark and typically fly at dusk, so they’re hard to see by reflected light. It’s much easier to pick out their silhouettes against a bright background. Fortunately, in a fence, we can use one post as the background, as seen from the next post in line.

Put a light source next to each camera and aim both the light and the camera at an adjacent fence post. Cover the target post with retroreflective tape, which will reflect the incoming light directly back toward the camera, much as a highway sign does. We often use 3M’s Diamond Scotchlite material, which reflects 3000 times as much light back toward the source as a matte white surface does. Other “safety marker” retroreflective materials should work too.

Single-color LEDs or diode lasers are good choices for the light source, because you can put a filter on your camera to block out stray visible light from the sun or nearby lamps. Infrared LEDs work better if you’d rather not attract insects, pets, or curious children to your fence; if you prefer a high-tech look, you can use red LEDs. You can add lenses or reflectors to focus the light at the target post, so that as little is wasted as possible.

Now that you have streaming video of bug shadows, the next step is to track the bogies. In simplest form, this just means generating a list of darker-than-usual pixels and grouping sets of adjacent dark pixels into objects. More sophisticated software might calculate the geometric center, or centroid, for each object, to achieve much better than single-pixel accuracy, or it could match up objects from one frame to the next, thus generating flight paths and measuring velocity. Extrapolate a track into the future and you can even predict where an insect will be—at least until its next zig or zag.

If you have more than one camera looking at the same target area, you can experiment with stereo imaging to estimate the range of each insect. The OpenCV software library (http://opencv.willowgarage.com) has many prebuilt functions for tracking and ranging.

Who flies there—friend or foe?

Let’s assume you don’t want to shoot down bumblebees, scare off hummingbirds, or freak out the neighbor’s cat while annihilating mosquitoes. How do you pick out the pests? The first test is size: Anything bigger than, say, 2 centimeters is not a mosquito (except perhaps in Minnesota, where the mosquito is reputed to be the state bird).

Another useful check is whether the target is isolated, with clear pixels on all sides. This test will rule out fingers, tree branches, or other objects that are thin but long. It should also prevent your fence from shooting at anything that’s too close to a large object, like your neighbor.

You may want to tune your system to reject things flying too fast (any more than 1 meter per second, unless there’s a breeze) or too slow. And anything moving vertically downward is more likely to be a raindrop or a falling leaf than a mosquito.

Simple filters such as these may be sufficient for backyard use. Although you don’t want to wipe out beneficial insects wholesale, it is probably okay to shoot gnats, flies, and small moths that attempt to crash your barbecue. Certainly the fence will inflict no more damage on the local ecology than an insecticide spray or an electric bug zapper. For large-scale malaria control, though, we need to be more selective (and more energy efficient), and so we have one more filter: We check how fast an insect beats its wings (see Web-only sidebar, “ Hold Your Fire Until You Hear the Beat of Their Wings”). This allows us not only to accurately identify the mosquitoes but also to tell in a split second whether they’re male or female. That way we can conserve power by sparing the lives of the males, which do not suck blood.

An insect has now wandered, unsuspecting, into the forbidden zone, and your program has decided it’s a bad bug. It’s time to point your death ray at it.

How fast and accurate your aiming system needs to be, and how large your killing pulse is, will depend on the geometry of your fence. As an example, if you want to be able to place a lethal pulse of energy anywhere within a target zone that’s 4 meters high and 10 centimeters wide (at a distance of 10 meters), then your beam must be able to swing 22 degrees up and down and about half a degree from left to right.

The most common way to steer a laser beam is to use galvanometers. A galvo is essentially a simple motor with a mirror mounted on the shaft. Drive a current through the galvo and the mirror will rotate by an amount proportional to the current. A built-in encoder feeds back the mirror position for closed-loop control. Individual galvos are often mounted in pairs to provide x-y motion.

High-quality galvos are carefully matched to their drive circuits and tuned by the manufacturer to provide maximum speed without overshoot or oscillation. They can be expensive: The Scanlab units we use—designed for laser marking and micromachining systems—cost upward of US $10 000 new. We managed to find some at an online industrial auction for about $500 each (although we then had to buy a controller card for close to $2000). But lower-cost galvos, designed for laser light shows, are widely available.

You can also experiment with other beam-deflecting techniques. Acousto-optic modulators deflect narrow laser beams over small angles (up to a few degrees) at high speed. Yet another approach is to rotate a pair of prisms relative to one another.

Whatever strategy you choose, keep in mind that the laws of diffraction will limit how well you can focus your killing laser. So the smaller the spot you want to produce, the wider the beam must be before it enters the focusing optics.

If, for example, your kill laser is an 808-nanometer infrared laser diode (with a high-quality single-mode beam), then a 4-mm-wide beam will remain nearly constant in diameter over 10 meters and will illuminate a 4-mm spot on the far fence post. But if you want to focus that beam on a 1-mm spot at 10 meters or on 4 mm at 40 meters, you’ll need to start with a beam that’s 16 mm in diameter.

Lights, Camera: Here’s some of the equipment needed to image a tiny bloodsucker flying at up to 1 meter per second.Ryan Smith/Intellectual Ventures

In any case, you’ll need a beam expander to enlarge the narrow beam produced by your laser, as well as galvo mirrors or other aiming optics big enough to accommodate the beam. Or you can deflect the beam first, then magnify it, which means you’d need to trade smaller galvo mirrors for bigger (but stationary) lenses. In our test system, the large output lens is actually a low-power telescope, which doubles the beam diameter (see photo, “Lights, Camera...”).

For the simplest aiming system, use a dichroic (wavelength-selective) beam splitter and arrange the camera and galvo so they share a common optical center. Then you don’t need to know the distance to your target; just as if you were sighting along a rifle barrel, what you see is what you hit. You’ll still need to calibrate the system to match up the camera and beam-steering coordinates, though. If everything is linear, that’s easy; you just need to steer the laser to three different spots and find the corresponding pixels on the camera.

If your camera can’t see your laser wavelength, you’ll need a way to find where the laser is pointed, such as an infrared-sensitive card, and mark the spot in a way the camera can see. A little algebra will give you the offsets and scale factors you need to point your laser accurately.

Usually, though, life won’t be so simple. Either your camera or your pointing system may be nonlinear; for instance, many camera lenses have “pincushion” or “barrel” distortion, which is really a change in magnification with the angle. You can measure the distortion by pointing your camera at a calibration grid and noting the nonlinearities. Or you can just move the beam a few more points, make a table of galvo input versus pixel position, and let your software interpolate between table entries. It’s worth the time to set up an efficient alignment process, though, because you’ll have to calibrate each camera, and you’ll need to recalibrate each time you change your optics or move a laser and camera relative to one another.

If the camera and beam deflector don’t share the same pivot point (as in our test system, where the camera lens and beam-output lens are a few inches apart), you’ll end up with a parallax error whenever you rotate the line of sight: A bug that shows up in a particular camera pixel will need slightly different laser-beam pointing, depending on how far away it is. I mentioned stereo imagery above as one way to find the range to bug; astute readers will no doubt think of other approaches.

A PEST’S LAST MOMENTS: The laser pulse (purple dot) induces an instant case of “heatstroke” that causes the critter to burn and crash.Image: Ryan Smith/Intellectual Ventures

Now comes the fun part: zapping the nasty little things. How much of a wallop should your laser pack? We’ve yet to find an engineering handbook—or even a paper in the entomological literature—that specifies the energy that’s lethal to mosquitoes. Certainly it must be less than about 2 joules, because that’s enough to boil the water inside a 1-milligram bug.

So we at the Intellectual Ventures laboratory have undertaken the world’s largest effort to discover what it takes to kill a mosquito using various wavelengths, pulse lengths, and fluxes of light. Our conclusion: For Anopheles stephensi (not your typical backyard pest but a close relative of the malaria-carrying strains), a few tens of millijoules, delivered within a few milliseconds, will cause most mosquitoes to expire within 24 hours. The blast gives them a sudden high fever, but not an obvious injury. Even under a microscope it isn’t clear what they actually die of. Let’s call it heatstroke.

We’ve shot high-speed video of mosquitoes being zapped with 50 to 100 mJ of light and found that although they keep flapping their wings, they lose attitude control and fall out of the sky. Boost the energy further and wings burn through or fall off, bodies emit puffs of steam, legs and antennae char, and so forth. Yes, it is a waste of laser energy, but revenge is sweet.

For a backyard system, the safest route would be to insist on “eye-safe” lasers, which emit wavelengths that the eye will not focus onto the retina. Alas, there are few inexpensive high-power lasers at eye-safe wavelengths, other than carbon dioxide lasers, whose wavelengths are so long (10.6 micrometers) that they require very large optics to focus over any distance. We have used an eye-safe near-infrared fiber laser operating at 1570 nm to kill mosquitoes, but even with diligent bargain hunting at surplus stores, you’re unlikely to find a comparable laser for less than several thousand dollars.

Ultraviolet lasers (shorter than 400 nm) are safe for the eyes, and pulsed UV light seems to be quite good for killing bugs, but they are also expensive. In addition, shorter UV wavelengths, particularly 266 nm (sometimes used for laser machining), can cause severe photochemical damage, including cataracts, even though they aren’t focused by the eye.

Therefore, if you can observe safety precautions—particularly wearing goggles at all times if there’s a chance of a stray beam—the best option may be a visible or near-infrared diode laser, or perhaps an older flashlamp-pumped laser. (SSY-1 flashlamp-pumped neodymium-doped yttrium aluminum garnet lasers, which can put out about one mosquito-lethal pulse a second, are often available on eBay for around $100.) Of course,making your guests wear FDA-approved goggles may put a crimp in your barbecue, but so would a cloud of thirsty mosquitoes.

We’ve found it helpful, as we assemble and align all the components, to combine a visible guide beam with the main laser beam, a color-selective beam splitter, or a filter. This makes it much easier to see where the laser will go. If your system has lenses downstream of the galvo, though, you will have a more complicated job aligning everything, because beams of different wavelengths will be steered and focused differently.

Before pressing the big red button, make sure your safety systems are working. Double-check that the kill laser won’t fire if there’s anything bigger than a mosquito in the way. Cover the optical path with an interlock to keep unauthorized folks away from beam paths (and high voltage, if any) inside.

All ready? Then turn everything on and wait for your first invader to breach the photonic plane. Track! ID! Aim! Fire!

Intellectual Ventures developed the photonic fence to help in an epic struggle against malaria and other vicious insect-borne diseases. But this technology could prove valuable in other roles as well, such as protecting crops from airborne pests or simply tallying insect populations rather than reducing them.

We don’t really expect many Spectrum readers will build a photonic fence for their backyards—although given the number of people whose first reaction to the concept is “How soon can I get one?” we wouldn’t be shocked to hear that some of you do. Our compliments: You will be helping to make the world a better place. Or at least a less itchy one.

JordIn Kare, an EE turned astrophysicist, is perhaps best known for his work on propelling spacecraft with laser light. He is now a contributing brain at Intellectual Ventures Management, an idea-making (and -selling) company run by ex-Microsoftie Nathan Myhrvold. When Bill Gates sought new ways to fight malaria, Myhrvold put Kare on the trail of a mosquito death ray powered by lasers. It shot its first bloodsucker out of the sky in 2008. Kare built the system on a shoestring, as he relates in “Backyard Star Wars.”

Your weekly selection of awesome robot videos

Evan Ackerman is a senior editor at IEEE Spectrum. Since 2007, he has written over 6,000 articles on robotics and technology. He has a degree in Martian geology and is excellent at playing bagpipes.

Video Friday is your weekly selection of awesome robotics videos, collected by your friends at IEEE Spectrum robotics. We also post a weekly calendar of upcoming robotics events for the next few months. Please send us your events for inclusion.

Another robotic pet on Kickstarter, another bunting of red flags.

Let's see, we've got: "she's so playful and affectionate you'll forget she's a robot." "Everything you can dream of in a best friend and more." "Get ready to fall in love!" And that's literally like the first couple of tiles on the Kickstarter post. Look, the hardware seems fine, and there is a lot of expressiveness going on, I just wish they didn't set you up for an inevitable disappointment when after a couple of weeks it becomes apparent that yes, this is just a robotic toy, and will never be your best friend (or more).

Loona is currently on Kickstarter for about USD $300.

Yeah, but where do I get that awesome shirt?!

Look, if you’re going to crate-train Spot, at least put some blankets and stuffed animals in there or something.

Is there an option in the iRobot app to turn my Roomba into a cake? Because I want cake.

Looks like SoftBank is getting into high-density robotic logistics.

Naomi Wu reviews a Diablo mobile robot (with some really cool customizations of her own), sending it out to run errands in Shenzhen during lockdown.

Roundtable discussion on how teaching automation in schools, colleges, and universities can help shape the workers of tomorrow. ABB Robotics has put together a panel of experts in this field to discuss the challenges and opportunities.

IEEE members get free admission and can help curate exhibits

Joanna Goodrich is the assistant editor of The Institute, covering the work and accomplishments of IEEE members and IEEE and technology-related events. She has a master's degree in health communications from Rutgers University, in New Brunswick, N.J.

Museum ENTER claims to have the largest collection of working Apple computers in Europe.

For more than a decade Museum ENTER, in Solothurn, Switzerland, has been a place where history buffs can explore and learn about the development and growth of computer and consumer electronics in Switzerland and the rest of the world. On display are computers, calculators, floppy disks, phonographs, radios, video game consoles, and related objects.

Thanks to a new four-year partnership between the museum and the IEEE Switzerland Section, IEEE members may visit the facility for free. They also can donate their time to help create exhibits; translate pamphlets, display cards, and other written media; and present science, technology, engineering, and math workshops.

The technology on display includes televisions and radios from the 1950s.ENTER Museum

ENTER started as the private collection of Swiss entrepreneur Felix Kunz, who had been amassing computers and other electronics since the mid-1970s. Kunz and Peter Regenass—a collector of calculators—opened the museum in 2011 near the Solothurn train station.

The museum’s collection focuses on the history of technology made in Switzerland by companies including Bolex, Crypto AG, and Gretag. The technology on display includes early telegraphs, telephones, televisions, and radios.

There are 300 mechanical calculators from Regenass’s collection. One of the mechanical calculators, Curta, looks like a pepper mill and has more than 700 parts.

The museum also has several Volksempfängers, the early radio models used by the Nazis to spread propaganda.

Visitors can check out the collection of working Apple computers, which the museum claims is the largest in Europe.

The IEEE Switzerland Section began its partnership with the museum last year, when the student branch at the IEEE EPFL hosted a presentation there, says IEEE Senior Member Mathieu Coustans, the Switzerland Section’s treasurer.

In May, the section and the museum organized a workshop celebrating 100 years of radio broadcasting in Switzerland. IEEE members presented on the topic in French, Coustans says, and then translated the presentations to English.

Based on the success of both events, he says, the section and the museum began to discuss how else they could collaborate.

The two organizations discovered they have “many of the same goals,” says IEEE Member Violetta Vitacca, chief executive of the museum. They both aim to inspire the next generation of engineers, promote the history of technology, and bring together engineers from academia and industry to collaborate. The section and museum decided to create a long-term partnership to help each other succeed.

In addition to the free visits, IEEE members receive a 10 percent discount on services offered by the museum, including digitizing books and other materials and repairing broken equipment such as radios and vintage record players. Members can donate historical artifacts too. In addition, IEEE groups are welcome to host conferences and section meetings at the facility.

The IEEE Switzerland Section as well as members of student branches and the local IEEE Life Members Affinity Group have agreed to speak at events held at the museum and teach STEM classes there.

“The museum is a space where both professional engineers and young people can network and learn from each other,” Vitacca says. “I think this partnership is a win-win for both IEEE and the museum.”

She says she hopes that “collaborating with IEEE will help Museum ENTER gain an international reputation.”

The perks of the collaboration will become “especially attractive with the opening of the brand-new Museum ENTER building” next year, says IEEE Senior Member Hugo Wyss, chair of the Switzerland Section, who led the partnership effort.

The museum is set to move in May to a larger building in the village of Derendingen. When it reopens there in November, these are some new additions visitors can look forward to:

The museum offers STEM workshops. ENTER Museum

In addition, these eight permanent exhibits will be available, the museum says:

The museum also plans to curate special exhibitions.

“We are going from being simply a museum with an extensive collection to being a center for networking, education, and innovation,” Vitacca says. “That’s why it’s important for the museum to collaborate with IEEE. Our offerings are not only unique in Switzerland but also across Europe. IEEE is a great partner for us to help get the word out about what we do.”

Learn how to measure and reduce common mode electromagnetic interference (EMI) in electric drive installations

Nowadays, electric machines are often driven by power electronic converters. Even though the use of converters brings with it a variety of advantages, common mode (CM) signals are a frequent problem in many installations. Common mode voltages induced by the converter drive common mode currents damage the motor bearings over time and significantly reduce the lifetime of the drive.

Download this free whitepaper now!

Hence, it is essential to measure these common mode quantities in order to take suitable countermeasures. Handheld oscilloscopes in combination with Rogowski probes offer a simple and reliable way to accurately determine the required quantities and the effectiveness of different countermeasures.