4 ms·

It is interesting that the reproduced image seems rotated from the color image. Is that change an artifact of the algorithm or being NLOS, or is it the angle of

It is interesting that the reproduced image seems rotated from the color image. Is that change an artifact of the algorithm or being NLOS, or is it the angle of the perspective (for lack of a better word since I'm not really sure how you would define your viewpoint) / a difference in where the color image was taken from the special sensor (i.e., you could place the normal camera in front of a mirror to have a similar perspective from the special sensor)...

DrJosiah 7y ago
They used some sort of wall to reflect off of. I'm sure that when they moved / removed the wall to take the regular picture, it wasn't in the same alignment.
GistNoesis 7y ago
The captured data is a 3D voxel grid (not a 2.5D image like kinect). In theory it can view behind the objects themselves. The reproduced image is an orthogonal projection of this 3D grid of pixel. Any projection could have been chosen. For example the camera projection could have been chosen to obtain exactly the same image.
- eximius 7y ago
  Do they have a lower effective resolution at different projections due to light reflected being somehow less direct (more reflections?)?
  - GistNoesis 7y ago
    Yes. The best views will be from projections whose camera position is at a point scanned by the laser. With the f-k migration algorithm, the output is in fact the aligned sum of 2.5D images that would have produced by cameras located at the laser scanned locations. The algorithm is based on a simple model which doesn't take into account obstructions or secondary ray reflections. In theory for slower algorithms in O(N^5) like inverting the rendering engine you can take obstructions, and ray bouncing into account, but the effective resolution will depend on the dynamic range of your measurements, that you can improve a little by increasing exposure time. In practice reflections don't carry enough information. You can also incorporate phase information (like with holograms) instead of just intensity, if you are able to measure it to get sharper image thanks to coherent imaging. Once you use the phase information, you can improve the spatial resolution, using multiple wavelength.

DrJosiah 7y ago

They used some sort of wall to reflect off of. I'm sure that when they moved / removed the wall to take the regular picture, it wasn't in the same alignment.

GistNoesis 7y ago

The captured data is a 3D voxel grid (not a 2.5D image like kinect). In theory it can view behind the objects themselves. The reproduced image is an orthogonal projection of this 3D grid of pixel. Any projection could have been chosen. For example the camera projection could have been chosen to obtain exactly the same image.

eximius 7y ago
Do they have a lower effective resolution at different projections due to light reflected being somehow less direct (more reflections?)?
- GistNoesis 7y ago
  Yes. The best views will be from projections whose camera position is at a point scanned by the laser. With the f-k migration algorithm, the output is in fact the aligned sum of 2.5D images that would have produced by cameras located at the laser scanned locations. The algorithm is based on a simple model which doesn't take into account obstructions or secondary ray reflections. In theory for slower algorithms in O(N^5) like inverting the rendering engine you can take obstructions, and ray bouncing into account, but the effective resolution will depend on the dynamic range of your measurements, that you can improve a little by increasing exposure time. In practice reflections don't carry enough information. You can also incorporate phase information (like with holograms) instead of just intensity, if you are able to measure it to get sharper image thanks to coherent imaging. Once you use the phase information, you can improve the spatial resolution, using multiple wavelength.