Kodak
reports on:
false, ugly, useful colors. .getting the lead in . . .thoughts to think while selecting an infrared detector
Try crazy color and that is subject to change without notice. We have learned that there are still some people around who are shy about laying out that kind of money on precious little assurance of success in their endeavors. We have therefore put it up in 135 form so that they can try out 20 shots in a KODAK RETINA Reflex Camera or such other 35mm still camera as the less fortunate find at hand. A note to Eastman Kodak Company, Special Sensitized Products Division, Rochester, Ν. Y. 14650, will start one or more cassettes to ward the Kodak dealer you name. We'll also tell you what to do about processing the film for the projector, just like real color film. 100. 10..
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An energy distribution like ^^J^'i'^^-J will come out red; Pictures like these are seen in Life, Look, and The Saturday Evening Post as they should be seen—in color. There we boast of film to renew your conviction that the world is beautifully colored. Here we advise of another color film of ours carefullydesigned to show chlorophyll as magenta, a film that depicts the works of nature and of man in colors thoroughly false, generally ugly, and possibly useful. As put up for use in aerial cameras, this KODAK EKTA CHROME Infrared Aero Film runs no less than around SI 10,
100. 10..
blue. The first is the , green; and most interesting. If you would like to pick out the parts of a subject that particularly absorb in this band, or particularly fail to absorb in this band, or particularly emit in this band, then this crazy film (aided by a wise choice of filter) fits you with the right kind of eyes, cheaply and simply.
It's all in the packaging (but not quite) We have thought of a way to improve the sensitivity to internal detail in x-ray pictures of the thinner, lighter kinds of objects. Nothing could be more practical. You need no new apparatus. Indeed, the apparatus list is reduced by two little items—ex posure-holders and lead foil. The foil has been a nuisance to the radiographer to have to explain over and over. Covering the film during exposure, it preferentially absorbs secondary, image-spoiling radiation of longer wavelength excited from objects around the film-holder. Photoelectrons generated in the foil further amplify the useful image. This works fine with sub jects substantial enough to take kilovoltages above 130 or so. With x-rays of feebler penetrating power, the losses in the foil exceed the gain, just as the naive would argue. For radiography of objects too light for the higher kilovoltages, the radiog
rapher can't find uniform lead foil that's thin enough. Now he can quit looking. We coat Pb304 on paper to a thickness corresponding to 0.0004" of metallic lead. Since the art of coating layers of various substances on sheets of various materials finds its most advanced state of perfection in our house, these lead oxide "screens" far surpass foil in uniform ity. We put the lead oxide next to a sheet of x-ray film and put the combination inside a iighttight paper package. The load ing and unloading of film-holders then becomes a waste of time. No dirt is picked up to absorb electrons. The radiographer calls the x-ray dealer and orders "KODAK Indus trial X-ray Film, LEAD PACK (ESTAR Base)." Genuine technological progress usually proceeds thus by easy steps, without the blatting of bugles.
For new highs in detectivity at t h e 4 . 3 μ CO*, b a n d :
Off-the-shelf KODAK EKTRON Detectors, Type Ε (which stands for evaporated PbSe), now hit 1 to 2 χ 1010 cm/watt-sec^ in D* at 1500 cycles, whether at —196CC, —78°C, or as warm as —45°C. This degree of temperature independence is news. Send for pamphlet on KODAK EKTRON Detectors to Eastman Kodak Company, Apparatus and Optical Division, Rochester, Ν. Υ. 14650.
For a simplified explanation of "detectivity": An EKTRON Detector changes electrical resistance in response to a change in radiant energy falling on it. Of course, one doesn't just turn on the infrared the way one turns on the porch light. One thinks frequencies. One inter rupts the infrared at a certain frequency and looks for this frequency of voltage fluctuation across the detector. One can't always be sure when the amplifier happens to hum at the right frequency that the infrared is doing it. There is always a cer tain amount of random electronic activity in the detector. The smaller the detector, the less this random activity gets averaged out and therefore the noisier it appears. On the other hand, the
more power per unit area in the infrared signal, the better the signal stands out against the noise. The sharper the tuning to the frequency, the less noise will happen by chance to fall within the narrow frequency range. This plodding line of thought leads to a definition of "de tectivity" as "the signal-to-noise ratio at a given radiation wavelength and chopping frequency with an amplifier band width of one cycle/sec for a photodetector of one square centi meter sensitive area when irradiated by one watt of flux." The brotherhood calls it D*.
This is another advertisement w h e r e Eastman Kodak Company probes a t random for mutual interests and occasionally a little revenue from those whose w o r k has something to do with science
