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Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
A last-minute burst of software hacking prior to the Nottingham Gaussfest yesterday got my high-speed video camera system to the point of being able to save some images... Project page It's been a stupidly large amount of work but hopefull worth it.. First images
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
wow, quite an accomplishment. I remember reading you site when you were just massing with the interface thinking how much effort it would take to make work...
how much effort do you think it would take to make it work with a modern ccd? I know that I can set the exposure on my digicam up at like 1/1000 second, seems like it would 'just' be a matter of saving the data from the ccd... Way out of my scope, unfortuantely :(
Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
You can't do it to any serious extent with standard CCDs, as although they can often do sub-millisecond shutter times, they are not designed for rapid readout. Clock rate limitations mean that you really need parallel signal paths out of the CCD, e.g. A VGA resolution sensor would need a 300MHz pixel clock to do 1000FPS on a single channel.
There may however be some scope for overclocking CCDs or CMOS sensors, but I don't know enough about tem to know how viable this might be. I know CCDs are pretty capacitive & need driving hard, so upping the frequency would get pretty hard pretty soon. I'd be surprised if you could get more than. say, double video rates. Micron make a nice high-speed imaging chip that does 1MPixel images at 500fps, smaller images faster : MT9L413 - nice chip as it has 10x10 bit on-chip ADCs and is available in a colour version, but cost is US$1400 (wonder if they do samples...?). Cypress also do one : LUPA-1300 with similar specs , but this has 16 analogue outputs so more work to interface.
I've had a couple of other thoughts about how you might be able to do high-speed imaging on the cheap: 1) Most high speed imagers have the ability to image partial frames at increased rates. I wonder if this might be a viable approach with standard CCD or CMOS sensors, by bending the drive signals or maybe even just forcibly resetting them at sub-frame rates. e.g. if you could get a VGA (TV) res sensor to scan, say 48 lines instead of 480, it could potentailly do 600 frames/sec, and that's before overclocking. 48 lines may not sound like much but it's plenty to see some interesting stuff. If you're really lucky you may not even have to do much with the interfacing- if the controller (e.g. USB interface) thinks it's scanning a whole field, but you are externally bashing the drive to do, say, 10x48 lines, then you'd get a series of 480 line images, each containing ten sub-frames
2) Repurpose the innards of a DLP projector. I've not thought this through too far, but in principle the DLP is an addressable light-valve. If you could get it into the optical path between a lens and a CCD/CMOS sensor, you could in principle use it to sequentially expose different parts of the CCD very rapidly. The optics could get pretty tricky though as you'd need to somehow get multiple copies of the same image area shining on different parts of the CCD simultaneously, to then be sequentially exposed during the CCD's frame exposure time. I have no idea how practical this would be, but it could in principle allow short bursts well in excess of 10K frames/sec, judging by the potential update rate figures on the TI DLP datasheets. You would probably need to bash the DLP at a pretty low level though....
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High-speed video camera project (nearly) finished
