polarization

10 Articles

Polarizing 3D Scanner Gives Amazing Results

December 23, 2015 by 16 Comments

What if you could take a cheap 3D sensor like a Kinect and increase its effectiveness by three orders of magnitude? The Kinect is great, of course, but it does have a limited resolution. To augment this, MIT researchers are using polarized measurements to deduce 3D forms.

The Fresnel equations describe how the shape of an object changes reflected light polarization, and the researchers use the received polarization to infer the shape. The polarizing sensor is nothing more than a DSLR camera and a polarizing filter, and scanning resolution is down to 300 microns.

The problem with the Fresnel equations is that there is an ambiguity so that a single measurement of polarization doesn’t uniquely identify the shape, and the novel work here is to use information from depth sensors like Kinect to select from the alternatives.

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Augmenting Human Vision With Polarimetric Cameras

December 15, 2015 by 30 Comments

Light is just a wave, and the wavelength of light determines its color and determines if it can cook food like microwaves, or if it can see through skin like x-rays. There’s another property of waves human’s don’t experience much: polarization, or if the light wave is going up and down, side to side, or anywhere in between.

[David Prutchi]’s project for the Hackaday Prize was like many projects – a simple, novel idea that’s easy and relatively cheap to implement. It’s a polarimetric camera meant to see what humans can’t. By seeing the world in polarized light, the DOLPi can see landmines, cancerous tissue, and air pollution using only a Raspberry Pi and a few Python scripts He gave a talk at this year’s Hackaday SuperConference about polarization cameras and the DOLPi project. After enjoying the video, join us after the break for more details.


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Polarization Camera Views The Invisible

July 28, 2015 by 55 Comments

Light polarization is an interesting phenomenon that is extremely useful in many situations… but human eyes are blind to detecting any polarization. Luckily, [David] has built a polarization-sensitive camera using a Raspberry Pi and a few off-the-shelf components that allows anyone to view polarization. [David] lists the applications as:

A polarimetric imager to detect invisible pollutants, locate landmines, identify cancerous tissues, and maybe even observe cloaked UFOs!

The build uses a standard Raspberry Pi 2 and a 5 megapixel camera which sits behind a software-controlled electro-optic polarization modulator that was scavenged from an auto-darkening welding mask. The mask is essentially a specialized LCD screen, which is easily electronically controlled. [David] whipped up some scripts on the Pi that control the screen, which is how the camera is able to view various polarizations of light. Since the polarization modulator is software-controlled, light from essentially any angle can be analyzed in any way via the computer.

There is a huge amount of information about this project on the project site, as well as on the project’s official blog. There have been other projects that use polarized light for specific applications, but this is the first we’ve seen of a software-controlled polarizing camera intended for general use that could be made by pretty much anyone.

The 2015 Hackaday Prize is sponsored by: