FLYING SPOT MICROSCOPY 



Danckwardt, p. W. and Eisenbrand, J., "Lu- 

 mineszenz-Analj^se im filtrierten ultraviolet- 

 ten Licht." 5. Edition Akademische Verlags- 

 gesellschaft Geest and Portig. K. F. Leipzig, 

 1949. 



Bandow, F., "Lumineszenz, Ergebnisse und An- 

 wendiing in Physik, Chemie und Biologic," 

 Wiss. Verlagsgesellschaft, Stuttgart, 1950. 



FoRSTER, Th., "Fluoreszenz organischer Verbin- 

 dungen," Gottingen, 1951. 



Pringsheim, p. and Vogel, M., "Luminesconce 

 of liquids and solids and its practical applica- 

 tions," Interscience Publishers, Inc. New 

 York, N. Y., 1942. 



G. L. Clark 



Flying spot microscopy 



In 1912, Tschachotin (1, 2) devised an 

 ultraviolet microbeam for the purpose of ir- 

 radiating selected areas of living protoplasm. 

 This ultraviolet microbeam was brought to 

 focus by the use of refracting lenses and was 

 rather crudely positioned on the specimen. 

 In 1954, Uretz, Bloom and Zirkle (3) re- 

 ported a much improved method for ultra- 

 violet microbeam irradiation of living 

 protoplasm. In 1956 Montgomery, Roberts 

 and Bonner (4) annoimced the development 

 of the ultraviolet flying-spot television micro- 

 scope and a new tool for the study of ultra- 

 violet irradiation effects came into being. 



In brief outline, the ultraviolet flying spot 

 television microscope utilizes as a light 

 source an ultraviolet-emitting flying-spot 

 scanner tvibe. A 250-line raster may be 

 traced upon the face of this tube at variable 

 sweep speeds from one sweep every 10 sec- 

 onds to one sweep every l/20th of a second. 

 For intermittent irradiation studies, the 

 raster may be switched on and off for any 

 integral nimiber of frames following any 

 predetermined number of sweeps. The image 

 of the raster of the ultraviolet emitting 

 cathode-ray scanner tube is minified by re- 

 flecting it in reverse through the optical 

 components of a suitable microscope. The 

 unabsorbed energy transmitted by the speci- 

 men is allowed to strike the photocathode 

 surface of an ultraviolet sensitive photo- 



multiplier tube. The resulting current gener- 

 ated in the photomultiplier tube is suitably 

 amplified and vised to modulate a monitor 

 tube locked in synchrony with the ultra- 

 violet flying-spot scanner tube. In this way, 

 a black and white ultraviolet absorption 

 image of the living specimen is traced out on 

 the monitor tube. Since the spectral charac- 

 teristics of the ultraviolet emitting cathode- 

 ray scanner tube are centered at 2600 A, the 

 black and white image of the specimen on 

 the monitor tube represents, in the main, a 

 nucleoprotein absorption image of the living 

 protoplasm. By appropriate photographic 

 techniques these images may be recorded by 

 time-lapse motion picture photography. A 

 block diagram of this system may be seen 

 in Figure 1. 



Modifications of this basic ecjuipment 

 have provided a technique for spot irradia- 

 tion of a specimen and this has been re- 

 ported by Montgomery and Bonner (5). In 

 brief this system functions by feeding the 

 horizontal and vertical sweeps to variable 

 delay, pulse-width generators. The pulses 

 thus generated are compared in a coincidence 

 circuit and at the time when both occur, and 

 output from the coincidence circuit modu- 

 lates the scanner tube grid, causing an in- 

 tensified spot to appear on the scanner tube. 

 This spot may be moved about on the raster 



334 



