Hacker News Reader

Comment by darsham | Hacker News Reader

I've always wondered if it's possible to build a video camera that films on the microwave spectrum instead of the visible light spectrum. Would such a tool would allow you to "see" wi-fi access points ? I guess they would look like bright, pulsating sources of light, and they would be visible through walls.

I did a bit of research on the subject, and they don't seem to really exist. It's possible that the longer wavelength poses technical difficulties. The individual receptors are too big and you can't cram them together at a sufficient density. Also, the lensing and shielding needs to be completely re-thought.

There's a 2012 paper called "Portable Real-Time Microwave Camera at 24 GHz" but i couldn't access it (not in academia).

View on HN

Check out this article http://www.wired.com/2013/01/new-metamaterial-camera/

Also, try searching Synthetic Aperture Radar :) fun stuff

Here's the full text: http://cl.ly/1E3t000K2q0E

There are two ways to capture an EM signal. The static-array method, where you have something like a CCD (a matrix of antennas that sample a signal in parallel), is basically only useful around the visible-light part of the EM spectrum.

What you do for the rest of the spectrum is to take one antenna and move it around. As long as the signal is relatively static with respect to time, this has the same effect (and is much cheaper to implement.)

> The static-array method, where you have something like a CCD...is basically only useful around the visible-light part of the EM spectrum

Why is this the case? Is it just that technology is further along for visible light because there's more economic incentive for a digital camera that replicates the human eye?

Is it a materials problem, where we haven't discovered arrangements of matter with the right properties (e.g. CCD's respond to visible wavelengths and are adaptable to semiconductor manufacturing techniques)?

Or is it something to do with fundamental physics like the wavelengths are a lot longer which requires detectors that are too large to be practical? Or maybe diffraction is a problem?

Here's what an image from the camera described in that paper looks like: http://i.imgur.com/3z8Uae9.png

Reply on news.ycombinator.com