
Turning Corners into Cameras: Principles and Methods - yamaneko
http://people.csail.mit.edu/klbouman/cornercameras.html
======
yamaneko
Paper is available here:
[http://people.csail.mit.edu/klbouman/pw/papers_and_presentat...](http://people.csail.mit.edu/klbouman/pw/papers_and_presentations/cornercam_iccv2017.pdf)

Abstract:

 _We show that walls, and other obstructions with edges, can be exploited as
naturally-occurring “cameras” that reveal the hidden scenes beyond them. In
particular, we demonstrate methods for using the subtle spatio-temporal
radiance variations that arise on the ground at the base of a wall’s edge to
construct a one-dimensional video of the hidden scene behind the wall. The
resulting technique can be used for a variety of applications in diverse
physical settings. From standard RGB video recordings, we use edge cameras to
recover 1-D videos that reveal the number and trajectories of people moving in
an occluded scene. We further show that adjacent wall edges, such as those
that arise in the case of an open doorway, yield a stereo camera from which
the 2-D location of hidden, moving objects can be recovered. We demonstrate
our technique in a number of indoor and outdoor environments involving varied
floor surfaces and illumination conditions._

~~~
taneq
> methods for using the subtle spatio-temporal radiance variations that arise
> on the ground at the base of a wall’s edge to construct a one-dimensional
> video of the hidden scene behind the wall

Interesting. I realised a few years ago that I automatically look down any
time I approach a blind corner (when walking through an office, for example).
Once I noticed it took me a while longer to figure out that I was looking for
the subtle diffuse shadowing that means you're about to walk into someone.

------
evanb
This reminds me of dual photography, where one can recover hidden images from
diffuse-diffuse light transfer.

video:
[https://www.youtube.com/watch?v=p5_tpq5ejFQ](https://www.youtube.com/watch?v=p5_tpq5ejFQ)

page:
[http://graphics.stanford.edu/papers/dual_photography/](http://graphics.stanford.edu/papers/dual_photography/)

~~~
anfractuosity
Wow the card reading experiment is really amazing!

Also I'm not sure if this is similar or not but the following, seems like it
might be related:

[https://www.cl.cam.ac.uk/~mgk25/ieee02-optical.pdf](https://www.cl.cam.ac.uk/~mgk25/ieee02-optical.pdf)

"Optical Time-Domain Eavesdropping Risks of CRT Displays"

Where he picks up an image from the diffuse light from a CRT on a wall.

------
tmaly
This should be used to save people's lives. Many of the marines on the ground
that have to go into buildings expect a 50% casualty rate.

~~~
Zeebrommer
Since it's funded by DARPA this is most likely the envisioned application.

------
chrischen
Originally I thought they were detecting diffracted light around the edge of
the wall but it turna out they are just annalzying the light on the floor,
which seems to have been done before [https://phys.org/news/2015-12-amazing-
camera-corners-video.h...](https://phys.org/news/2015-12-amazing-camera-
corners-video.html)

~~~
tonyg
This present research cites the older work you link. The older work uses
active illumination; the present work appears to be entirely based on passive
recovery of information.

------
yathern
Very cool! I'm always interested by clever uses of perception technology. I
wonder if this can be combined with video magnification[1] to remove some of
the noise?

[1]
([http://people.csail.mit.edu/mrub/vidmag/](http://people.csail.mit.edu/mrub/vidmag/))

------
ge96
Not related but I once saw this effect where your shades/curtain gap sometimes
if the light goes through it correctly you see the image coming in from the
window projected onto your wall... I think this is related to how pinhole
cameras were discovered/made but anyway that's pretty sweet.

~~~
homero
[https://en.wikipedia.org/wiki/Camera_obscura](https://en.wikipedia.org/wiki/Camera_obscura)

~~~
ge96
Thanks

------
jake-low
Fascinating and counter-intuitive that so much information is 'leaked' in
light patterns that can't be discerned by the eye. There's a color-amplified
visualization in the first embedded video of TFA (starts at 1:40) that shows
this really well.

------
vinchuco
[https://arxiv.org/pdf/1412.7884v1.pdf](https://arxiv.org/pdf/1412.7884v1.pdf)

