Journal of the Society of Motion Picture and Television Engineers (1950-1954)

jfeirable, and often mutually conflicting, I characteristics: I High optical speed, ((High mechanical speed, •Good resolution, •Freedom from distortion, IjFreedom from blurring due to relative motion between image and film, I Adaptability to various types of photog raphy and subject matter, II Large number of pictures exposed in one sequence, i Projectability of photographs as exposed without re-registration, I Simplicity and ruggedness of construction, Economy of construction, and I Economy in the use of photographic film. The Isotran principle was first used in a camera developed in the labora tories of the National Advisory Committee for Aeronautics.1-2 That camera, of which three units were constructed by NACA, has given highly satisfactory service over a period of about thirteen years. Many of the results of its work have been published.8 Its maximum speed is 40,000 frames/sec. In the Isotran camera developed at Battelle, the mechanical and optical arrangements have been considerably modified from those of the NACA camera, to permit a potential increase of repetition rate to 100,000 frames/sec. The unique feature of the Isotransport camera is the transport of film and photographic images by the same opticalmechanical part. By this means identity of motion of film and image, both as to speed and direction, is permanently and rigidly assured. Backlash of gears, increasing with wear, is never involved. ISOTRANSPORT DESIGN General Design Features Figure 1 is a photograph of the Battelle Isotran camera. The visible major components are labeled in the photograph. The only moving part that is photographically functional is a disk, approximately two feet in diameter, which spins within the rotor housing. This disk, weighing about 50 Ib, is fabricated of forged aluminum alloy; it turns at 12,000 rpm for a repetition rate of 100,000 frames/sec, or at proportionately lower speeds for lower repetition rates. The disk carries either one or two strips of standard 8mm film, approximately six feet in length, in closed circular loops on the inner surface of ledges at its periphery. The spinning disk carries, in addition to the film, a series of small mirrors disposed about its outer periphery. These mirrors operate in pairs, one pair for each frame to be exposed, a total of 1,000 mirrors for the 500 frames that can be exposed in one photographic sequence. These mirrors, which will be explained in detail later, function in conjunction with a number of stationary parts of the optical system of the camera, and they constitute the image-transport mechanism. Hence the spinning disk, with the attached reflectors, constitutes both the image-transport and the filmtransport mechanism. It is from this advantageous condition, allowing no conceivable variation in relative speed of image and film, that the name "Isotransport" is derived. The spinning disk is driven by a pistontype hydraulic motor which occupies part of the space within the hydraulicmotor housing. This hydraulic motor is geared to the shaft of the spinning disk, to provide 3^ turns of the disk for each turn of the motor. Fluid is delivered at 1000 psi to the hydraulic motor by the vane pump, direct-connected to the three-phase induction motor. The hydraulic drive, as opposed to a direct or geared connection of the electric motor to the spinning disk, represents the most convenient solution Miller and Scharf : Isotransport Camera 131