Ten years ago, MIT researchers proved that it was possible to look through an envelope and read the text inside using terahertz spectroscopic imaging. This research inspired [Barmak Heshmat] to try the same technique to read a book through its cover. A new crop of MIT researchers led by [Heshmat] have developed a prototype to do exactly that, and he explains the process in the video after the break. At present, the system is capable of correctly deciphering individual letters through nine pages of printed text.
They do this by firing terahertz waves in short bursts at a stack of pages and interpreting the return values and travel time. The microscopic air pockets between the pages provide boundaries for differentiation. [Heshmat] and the team rely on these pockets to reflect the signal back to a sensor in the camera. Once they have the system dialed in to be able to see the letters on the target page and distinguish them from the shadows of the letters on the other pages, they use an algorithm to determine the letters. [Heshmat] says the algorithm is so good that it can get through most CAPTCHAs.
The most immediate application for this technology is reading antique books and other printed materials that are far too fragile to be handled, potentially opening up worlds of knowledge that are hidden within disintegrating documents. For a better look at the outsides of things, there is Reflectance Transformation Imaging.
Continue reading “MIT Researchers Can Read Closed Books (and defeat CAPTCHA)”
Spectroscopy is one of the most useful tools in all of science, and for The Hackaday Prize’s Citizen Science effort [esben] is putting spectroscopy in the hands of every high school student. He’s built a super cheap, but very good spectrophotometer.
The idea of a spectrophotometer is simple enough – shine light through a sample, send that light through a diffraction grating, focus it, and shine the light onto a CCD. Implementing this simple system is all about the details, but with the right low-cost lenses and a 3D printed enclosure, [esben] has this more or less put together.
Of course, lenses and diffraction gratings are relatively simple. You need real data, and for this we can turn to another one of [esben]’s projects in the Hackaday Prize. It’s a breakout board for a linear CCD module, able to capture the spectrum coming off a sample with incredible precision. This is how real spectrophotometers are put together, but because of the difficulties in driving a CCD, not many people have put one of these together.
Both of these projects are finalists for in the Citizen Science portion of The Hackaday Prize. That’s an awesome result for what is a complete system for learning about spectroscopy with a device that’s also able to produce some high-quality data, too.
If you understand technology, there were a lot of things hard to explain on Star Trek. Transporters, doors that were smart enough to open unless you hit them during a fight, and the universal translator all defy easy explanation. But one of the hardest things to explain were Mr. Spock’s sensors. From the ship or with a tricorder, Spock could sense at a distance just about anything from chemical compositions, to energy, and even the presence of life (which, today, at least, is difficult to determine even what that means).
Remote sensing would have a very distinct use in today’s world: finding terrorist bombs earlier. A recent article published on New Scientist by [Debora MacKenzie] points out that stopping attacks like the recent one in Brussels is difficult without increasing congestion. For example, putting checkpoints at doors instead of inside transit stations is common in Asia, but causes lines and delays.
The United States has used ion mobility spectrometry (IMS) to detect explosive traces on swabs (using machines like the one on the left). However in the early 2000’s they experimented with a version of the device that used puffs of air to determine if people had explosives while they passed by the machine. By 2010, officials decided the machines broke down too often and stopped using them.
Remote Sensing in Practice
According to an expert at Rand Corporation, remote sensing is likely to employ imaging or sniffers. However, imaging solutions are easy to fool since a bomb can take the shape of an ordinary object. Sniffers, including biological sniffers (known as dogs), are harder to fool. The problem is that deploying thousands of dogs to cover the world’s airports is difficult.
Continue reading “Remote Sensing Bombs Could Stem Terrorism”
There are hackers who have soldering setups on the dining room table, and then there are hackers who have scanning electron microscopes in their living room. [Macona] is part of the latter group, with a Hitachi S-450 SEM he’s repaired and modified himself. [Macona] has documented the whole thing on Hackaday.io. The Hitachi came to him and a friend as a derelict. First it was broken, then stored for 10 years. It turned out the problem was a high voltage cable cut and spliced with electrical tape. The tape eventually broke down and shorted out the 500V supply. Thankfully the rectifier diodes were the only parts that needed to be replaced.
The SEM sprang to life and gave [Macona] and a friend their first images. However, SEMs are finicky beasts. Eventually the filament burned out and needed to be replaced. New filaments are $500 US for a box of 10, which is more than [Macona] wanted to spend. It turns out filaments can be built at home. A bit of .089mm tungsten wire and a spot welder were all it took to fix the issue. Next to go bad was the scan amplifier. While SEMs use many exotic parts, the Hitachi used relatively common Sanyo STK070 audio amplifiers for the purpose – an easy fix!
One thing that makes this SEM unique is the is Energy Dispersive X-Ray Spectroscopy (EDX) unit attached to it. The fragile liquid nitrogen cooled sensor was working, but the 1980’s era signal processing computer was a bit too old to bring up. A friend and fellow SEM hobbiest gave [Macona] a slightly newer Kevex Sigma Gold signal processor, which was nearly a plug and play upgrade for his machine. The new processor processor also gave him digital beam controls and a digital output which could be used to capture images with a PC.
Once all the connections were made, the EDX worked surprisingly well, even finding gold in a uranium ore sample placed in the microscope.
Now that old scanning electron microscopes being retired, it’s only a matter of time before more us get a chance to join the ranks of [Jeri Ellsworth], [Ben Krasnow] and [Macona] with our own personal SEMs!
It’s a relatively simple task to find evidence of helium by just looking at the sun; all you need is a prism, diffraction grating, and a web cam. DIY spectrometers have been around for ages, but most of them only produce a spectrum, not a full image complete with spectral data. Now it’s possible to take an image of an object, complete with that objects spectra using a DSLR, some lenses, a PVC pipe, and the same diffraction grating from your DIY interferometer.
The idea behind a hyperspectral imager is to gather the spectral data of each pixel of an image. The spectral data is then assembled into a 3D data cube, with two dimensions dedicated to the image, and the third dimension used to represent wavelength. There are a surprising number of applications for this technique, ranging from agriculture and medicine to some extremely creepy surveillance systems.
The authors of this paper (freakin’ huge PDF) used a piece of PVC pipe, three camera lenses, a diffraction grating, and a small paper aperture to construct their hyperspectral imager. Images are captured using a standard, multi exposure HDR method, assembling the raw data from the camera into a hyperspectral image with MATLAB.
There’s a ton of awesome info in the PDF, covering how the authors calibrated their system for different lighting conditions, interpreted the RGGB Bayer sensor in the camera, and a few examples of what kind of image can be constructed with this kind of data. That’s a recommended read, right there.
Thanks [Yannick] for the tip.
[Bruce] sent us another fantastic final project from the ECE4760 class at Cornell. What you see above is an array of 36 near infra red LEDs shining into this young man’s brain for the purpose of spectroscopy. Light bounces back differently based on brain activity (blood flow). For this project, they are mapping their motor cortex and displaying it on a PC using a java app. You can see the entire rig, as well as the readings in the two videos after the break.
When this tip came in, one of our writers,[Jesse Congdon], chimed in as well.
hey I actually used to work in this as an intern, at Upenn. two frequencies of near infrared light are used that both penetrate skin and bone, one bounces off of blood in general and the other bounces off oxygenated blood. Since your brain actually regulates the flow of blood to parts that are in use you can see brain activity by looking at blood flow, but then you also need to see if the brain is actually using that blood, so oxygenation gives you a full picture. The frontal cortex is a nice place to measure cause there is no hair on that portion of the skull, and it gives you emotional responses and the “aha!” moment when you figure out a problem.
One article from way back said the system was going to be used as a lie detector, since when you lie you think about the truth and the lie simoltaneously and show an increase in activity.
It’s tough though to categorize a response since you can’t really establish “base line” activity by turning off the brain
Continue reading “Mapping the motor cortex”
If you were to try to take a picture of a UFO, how would you do it? Sit by the side of a road in Nevada near Area 51? Pie tin on a string? A French team of UFO enthusiasts put together an automated UFO detection device (Google translate) out of a disco light and CCTV camera so long nights of watching the skies can be automated.
The build uses a disco light with an altitude and azimuth mount to constantly scan the skies on the lookout for strange, unexplained lights. Attached to this swiveling mount is a camcorder and a CCTV camera that streams video to the command and control laptops for image analysis.
In addition to object tracking, there’s also a diffraction grating in front of the CCTV camera. The team behind this project previously used this for some very low tech spectroscopy (translation) to identify emission lines in a light source. Light that have a signature including Oxygen and Nitrogen will probably be ionized air, while less common elements may be the signature of “advanced propulsion.”
While this build is going to detect a lot of satellites and meteors, there’s a definite possibility of capturing an unexplained phenomenon on video.