[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: High speed arc photos: rotating mirror vs streak camera



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 09:48 PM 9/19/2006, Tesla list wrote:
Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Just to stimulate further discussion & experimentation, there are at least two techniques that can be used to separate and record the multiple discharges that make up a tesla coil streamer.

In the first technique, the moving image is swept across a fixed detector. This can be accomplished by using a rotating mirror, etc, to sweep the image across photographic film or a CCD detector. This is the technique being used by Peter and Terry.

In the second technique, a fixed image is projected onto a moving detector, the "detector" usually being photographic film. This is the classic technique used in some types of high speed motion picture cameras, where a length of film is "accordian-folded" into a canister, then rapidly accellerated to a high linear speed just milliseconds before the "event" is triggered.

Do a web search for "streak camera" and you'll find info on many different implementations of streak cameras, some specifically for capturing high-speed events. Some clever modifications have been made to motor-drive 35mm cameras to convert them to streak-camera function. A 35mm camera will allow the use of specialized high-speed (high-sensitivity) films, but of course requires processing before the results can be viewed.


There are also schemes where the film is on a drum that is spun.

If you run the math for reasonable frame sizes and high frame rates (1 Mfps), you'll find that you need to spin that mirror pretty darn fast (as in, using a diegrinder air motor fast).

Very high speed cameras these days use electronic shutters and image intensifiers. The standard image intensifier can also serve as a shutter by driving the bias appropriately. Surely an ambitious TCer would have no problem making short HV pulses, eh?

There are also such things as Pockels and Kerr cells (the latter is faster), which are electrically driven. One could set up a whole series of inexpensive, but slow, cameras, with fast shutters in front of them that are triggered in sequence by some sort of timing apparatus. An updated version of Muybridge, if you will.