[visionegg] Re: upper frame rate limit for random dot motion displaysand gratings

Anne-Kathrin Warzecha wrote:

Hi,
we need a visual stimulation device that can reliably present motion stimuli (random dot and gratings superimposed by noise) above 200Hz. Does Vision Egg support such an application? Are there special graphics cards and monitors that have been used for similar purposes preferably based on Windows as operating system?
Thanks for your help!
Best wishes A.-K. Warzecha

Dear Anne-Kathrin,

Good to hear from you! I approved your posting to the mailing list (only subscribers are allowed). I suggest subscribing in case others reply to this thread on the list.

The only serious difficulty is stimulus hardware; most current video cards and operating systems do not establish an explicit upper framerate limit. It seems that consumer CRT monitors top out at 200 Hz. There may be specialist displays (for air traffic control or medical industries) that go faster. I just looked at http://www.imagesystemscorp.com/ and couldn't find anything, but I think they used to offer a 240 Hz CRT -- perhaps it's worth a phone call. Another device apparently does 4096 frames per second in binary (black and white) mode: http://www.opticalsciences.com/Engineering/projectors/dmd/osc_dmdinfo.htm . We'd love to hear back if you discover anything more regarding fast displays.

There is one interesting trick I've heard of, but have no personal experience with, to get high frame rates: by removing the spinning filter wheel from a DLP projector, each RGB frame is no longer drawn as temporally interleaved R, G, and B images, but instead as multiple monochrome images.The trick in this case is to compute RGB frames that take this into account. While the Vision Egg doesn't currently do this, it's certainly something I'm interested in and could lend a helping hand in implementing. (Also, for some experiments, it is possible that the stimulus itself need not be updated at such a high rate, but only that the flicker is fast. In this case, any needed RGB maninipulation would be simpler.) Upon a bit of surfing, I wonder if this projector ( http://www.plus-vision.com/en/product/projector/u3-1100w/index.html ) turns off the filter wheel spinning at the flip of a switch.

Cheers!
Andrew

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