Hyperspectral Imaging With A DSLR

spectral

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.

Mapping the motor cortex

[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

[Read more...]

Automated sky tracking to catch UFOs

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.