Space-Time Warping Imaging at 1T fps - Ramesh Raskar

[dsmikk]

Imaging at a Trillion Frame Per Second - Ramesh Raskar

http://www.ted.com/talks/ramesh_raskar_a_camera_that_takes_one_trillion_frames_per_second.html

Although this video is extremely interesting, The part I'm most interested in occurs at about the 9:30 mark.


Ramesh Raskar says,

"But there is also something funny going on here .. the ripple are moving away from the camera towards the cap of the bottle when we know that light should be moving from cap to the camera?
Well Einstein would have loved to see this femto-photo.
It turns out that because we are recording nearly at the speed of light, there is reversal in how we observe events in the world. After a correct mathematical space-time warp, we can correct for this time distortion."

So my question is, why do we observe a reversal in the events when photographing at almost the speed of light? I may be overthinking, but I'm curious and was wondering if anybody had an explantation. Thanks in advance for any responses!

 

[mfb]

A photo is the collection of all light that reaches the camera at a specific point (better: very short interval) in time. It is not a collection of all light emitted at a specific time.

For regular photos, this does not make a difference, as the time needed from emitter to camera is negligible. For those high-speed videos, the effect is relevant. To determine the frame where the camera will see light somewhere, you have to add the length between light source and this point and the length between this point and the camera.

This does not have to lead to a "reversal", but it leads to significant effects on the images.

 

[dsmikk]

For regular photos, this does not make a difference, as the time needed from emitter to camera is negligible. For those high-speed videos, the effect is relevant. To determine the frame where the camera will see light somewhere, you have to add the length between light source and this point and the length between this point and the camera.

Ahh that makes more sense now. I was definitely overthinking the process. Thanks

 

[A.T.]

I was definitely overthinking the process. Thanks

Or the guy was over-explaining the issue.

 

[sardar]

I can provide an explanation for the observed reversal in events when photographing at almost the speed of light. This phenomenon is known as the Lorentz transformation, which is a fundamental concept in Einstein's theory of special relativity. According to this theory, the speed of light is constant in all reference frames, and as an object approaches the speed of light, time and space become distorted.

In the case of Ramesh Raskar's imaging technology, the camera is recording at a trillion frames per second, which is close to the speed of light. This means that the camera is capturing images at a very high frequency, and as a result, there is a time dilation effect. This means that time appears to slow down for the objects being photographed, causing a reversal in the observed events.

To correct for this time distortion, Raskar and his team use mathematical space-time warping techniques, which essentially account for the effects of special relativity on the captured images. By doing so, they are able to accurately reconstruct the events as they would appear in normal time.

In essence, the observed reversal in events is a result of the fundamental principles of special relativity and can be explained through the Lorentz transformation. Raskar's innovative imaging technology not only captures images at an incredibly high speed, but it also allows us to observe and understand the effects of special relativity in real-time events. This has immense potential for various fields of science, including physics, biology, and medicine.