PDA

View Full Version : image sensors



wind27382
03-12-2008, 07:54 PM
I have just one big question does anyone know how I could use a serious of 30fps CMOS image sensors. to capture high speed video sort of like this.

http://graphics.stanford.edu/papers/highspeedarray/

Eric
03-13-2008, 07:03 AM
2 items to consider.
1. A 30fps camera will capture the motion of 1/30 sec. so even if you have a bunch of cameras at 30fps timed somehow, you are still only getting 1/30 sec at best. You can sync up several still frame cameras to get that effect (because you can set the shutter speed to 1/500 sec. or more) For example, if you take your SLR still frame camera and turned it to 1/30 sec, that is the best any normal video camera will do.
2. With high speed photography, MUCH more light is needed. Often strobe lights are used to illuminate the object. The less time the camera has to capture the picture = the more light you need.
So the answer to the question is: probably not. (Without changing the camera)

jdolecki
03-13-2008, 05:25 PM
Did you read the Attached PDF file on your link? That explains how the system works.

The trick is the software they wrote to assemble and correct the immages into one.
This explains how they get 1560 FPS.



Using n cameras running at a given frame rate s, we create
high-speed video with an effective frame rate of h = n  s

by staggering the start of each camera’s exposure window
by 1/h and interleaving the captured frames in chronological
order. Using 52 cameras, we have s=30, n=52, and

h=1560fps. Unlike a single camera, we have great flexibility
in choosing exposure times. We typically set the exposure
time of each camera to be 1/h or less, or 1/1560sec.
Such short exposure times are often light limited, creating

Eric
03-14-2008, 12:28 PM
Yup, you caught me... I didn't see the pdf on that. One interesting thing about that is they said "regular off-the-shelf" video cameras
The key is they need to get a video camera that has a variable shutter speed. Many cameras I used had a slow/fixed shutter speed to capture as much light as possible (makes it easer to shoot) They needed to find cameras that you can modify that shutter speed (and pretty fast shutter speed too!) So that explains the correction.(plus it's amazing how they snyced up the start up just right.. but that's another animal) Yes it can be done with some cameras, but low-end webcams probably won't cut it. Certainly won't be cheap...
Now their processing I find facinating. Lots of logic behind that to make it work. Very clever folks.
How can you(the generic "you") create somthing like that... I sure wouldn't want to try it without plenty of grant money. :veryhappy:
Interesting topic... thanks for showing it!