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1949 IMPROVEMENTS IN HIGH-SPEED PICTURES 465
TWO-DIMENSIONAL SCANNING CAMERA
In our first paper on this subject,! the basic theory proposed a composite picture made up of widely displaced silver deposits with unexposed areas between them much larger than the deposit size. The spacing of the coherent elements for one picture would be so coarse as to provide room in the neighborhood of each for elements to be used for 899 other pictures. Such a system would require a well-made focal-plane sieve for positively selecting those elements which constitute related parts of a single picture both for exposure and for viewing. Once again if each hole (the sieve as a unit) could be translated to a new nonoverlapping position, unexposed emulsion would be uncovered for the recording of an entirely new picture. This theory requires two-dimensional scanning, a picture now being made up of dot elements rather than linear strips as before. A two-dimensional scanning system could be made by using two of the one-dimensional form described in our first paper and operating at right angles to one another. This, however, would be much too complex especially in view of the high speeds we wish to attain. A much simpler approach is to use a disk carrying a configuration of holes, the disk rotating in a camera focal plane to record the composite subject motion frames as the event progresses. Such a disk begins to approach the theoretical sieve which we proposed in our initial paper.
A two-dimensional version of the high-speed multiple-aperture scanning camera will now be described which is capable of taking 900 pictures at a rate up to several million per second. These figures are based upon the assumption that the number of frames is a function of aperture diameters uncovered. This we have now shown to be on the low side factorily. However, since we have not done any absolute frame-number work for this device similar to that already described for the one-dimensional case, this basis will suffice for our preliminary introductions. Basically this camera consists of a focal-plane sieve in the form of a disk which rotates very nearly in contact with the emulsion of a photographic plate on which the images are recorded. The camera contains a capping shutter which operates in much the same fashion as that described for the one-dimensional case. Fig. 1 shows the configuration of holes on the disk and the action of the capping shutter. On any given radius there is a series of holes one unit of length in diameter, each thirty units of length apart. On another radius sufficient distance away such that its outermost hole can be t This issue, pp. 451^61.