Contains research objectives and reports on one research project.Woods Hole Oceanographic InstitutionU. S. Navy, Office of Naval Researc

Breslau, L. R.

Edgerton, Harold E.

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XI. STROBOSCOPIC RESEARCHProf. H. E. EdgertonL. R. BreslauRESEARCH OBJECTIVESIntermittent light is an essential component of a very highly specialized type ofinstrumentation that involves precise flash timing and uses photography for recording.The main object of this work is usually to aid the eye to observe fast actions and tomake accurate measurements.For example, the experimental information about elementary particles and inter-actions which is now so eagerly sought by nuclear physicists is recorded by electronicflash lamps during the brief moment in the cloud chamber after expansion. Then beginsthe tedious work of reducing the data from the photographs. Our laboratory has helpedmany physicists with the illumination problem for the cloud chamber.In addition to the application work on direct instrumentation, the Stroboscopic Lightlaboratory is vitally concerned with the development of flash sources of many types andfor many uses. Each year brings advancement, usually through theses of students inthe Departments of Electrical Engineering and of Physics.H. E. EdgertonA. DESIGN AND CONSTRUCTION OF A LUMINESCENCE CAMERAAn instrument was designed for photographing the sea animals that cause underwaterluminescence. These light flashes had been observed by members of the Woods HoleOceanographic Institution (W. H. O. I.) while using the bathyphotometer (1). Their observa-tions indicated that a luminescence detector could be triggered by flashes with an irradi-ance of 10 - 5 microwatts/cm2 or more.As an extension of his thesis, L. R. Breslau, who is now at M.I.T. as a staff memberof W. H. O. I., designed and built the aforementioned instrument. It was constructed atM. I. T. with the cooperation of the Research Laboratory of Electronics, especially inthe use of the Laboratory's facilities.A photomultiplier trigger, which can be actuated by the flash of an underwater animal,was designed to trigger an electronic-flash-and-camera combination. (The photomulti-plier device was designed in such a way that it is not injured by direct sunlight or by thelight flash emitted by the electronic lamp.) Simultaneously, a sonar pulse is emitted byan attached transducer; this signal indicates that a picture has been taken and, in addi-tion, relays information about the depth of the instrument from the surface.The instrument, which is self-contained, requires only the mechanical support of acable. The device can be operated continuously at any depth down to 6000 meters for atleast 10 hours before the batteries require recharging. Mercury switches allow loadingand storing of the instrument in a prepared state. The camera (2) and the film-advancing circuitry are contained in one cylindrical housing, and the electronic flashPart of this work was done in conjunction with the Woods Hole OceanographicInstitution. The W. H. O. I. work is supported by the U. S. Navy, Office of Naval Research.(XI. STROBOSCOPIC RESEARCH)Fig. XI- 1.Fig. XI-2.Flash unit of luminescence camera.HING RELAYD SIL MICROSWITCHD3101'I C 6VCamera unit of luminescence camera. (The microswitchrides on a cam that is gauged to the film advance motor.)and photomultiplier trigger (Figs. XI-1 and XI-2) are contained in another. Thesehousings fit into a rigid cradle. Detailed descriptions of the mechanical design, cameradesign, and electronics are given in a recent report by Breslau and Edgerton (3).The entire volume of water observed by the photomultiplier is in the field of view ofthe camera and is illuminated by the electronic flash. Because many luminescentanimals have translucent bodies, side lighting was considered advisable. Of course, acompromise must be made between the size of the field and the magnification of thephotographed object. Because most of the luminescent animals that were to bephotographed were expected to be less than 3 inches long, an observed volume of0. 1 cu ft was decided upon. A second position of the cylindrical housing tubes inthe cradle allowed the camera to photograph only one-half of the volume observed(XI. STROBOSCOPIC RESEARCH)by the photomultiplier but produced twice the magnification.The luminescence camera was operated from the Research Vessel Crawford and theCoast Guard Cutter Yamacraw in the waters south of Woods Hole, Massachusetts. Thebest results were obtained when the instrument was used in conjunction with the bathy-photometer and a graphic recorder for echo sounding. (The bathyphotometer is a wide-range, logarithmic device that is sufficiently sensitive to detect luminescence, but isnot injured by a high-intensity electronic flash.) Several small animals took their ownpictures successfully by means of the luminescence camera.L. R. Breslau, H. E. EdgertonReferences1. G. L. Clarke and C. Hubbard, Quantitative records of the luminescent flashing ofoceanic animals at great depths, forthcoming in April 1959 issue of Limnology andOceanography.2. H. E. Edgerton and L. D. Hoadley, Cameras and lights for underwater use,SMPTE J. 64, 345-350 (1955).3. L. R. Breslau and H. E. Edgerton, The luminescence camera, Technical Report,Reference No. 58- 14, Woods Hole Oceanographic Institution, April 1958 (unpublishedmanuscript).

Stroboscopic Research

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Stroboscopic Research

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