(images coming soon!)
I never even knew this kind of camera existed until I found this thing on eBay. Framing cameras are a class of very, very high speed cameras that work by storing frames in spatially separated locations. The usual sort works by sending the incoming light through a set of beamsplitters onto a set of several (usually 8 or 16) intensified, MCP-gated CCD's. A precise timebase shutters the MCP's in sequence, usually a few nanoseconds apart; the result is that each CCD captures one frame of a high-speed image sequence. Frame rates of several hundred million FPS are possible.
It turns out, however, there is a different and much older class of framing camera. These work on a principle similar to a Gen 2 night-vision tube: incoming photons strike a photocathode, where they are converted to electrons and accelerated through a potential of several kilovolts. From there, the electron beam (which is spatially modulated by the incoming light and ~10mm in size) is electrostatically gated and steered, oscilloscope-style, onto an output phosphor screen. The result is that each frame appears on a different spot on the screen; to capture the image, a digital photograph or film contact print(!!) is made.
This particular unit can be configured to capture 8, 12, 15, or 24 frames (with decreasing frame size) on a 70mm output screen with 15lp/mm resolution; this translates into roughly 12 VGA-sized frames.The inter-frame time can be under 50ns; the manufacturer claims up to 24 million frames per second.
We have it a lot better in the modern world; on release your choice of capture device was an ASA3000 film contact print or a image taken with a 1.5MP CCD connected to an "IBM PC compatible running menu-driven capture software under Microsoft Windows"; nowadays, pretty much any DSLR or microscope camera will have sufficient performance. Lenses have gotten a lot sharper wide open too, giving a bigger chance of capturing those precious 15 line pairs per millimeter.
No comments:
Post a Comment