American cinematographer (Jan-Dec 1946)

New Orthicon Television Tube (Continued from Page 7) images from interference due to ex¬ ploding photo flash bulbs and other sudden bursts of brilliant light. 4. Smaller size of tube, facilitating use of telephoto lens. 5. Type of design that lends itself to use in lightweight, portable television camera equipment. 6. Improved gain control system that provides unvarying transmission, de¬ spite wide fluctuations of light and shadow. How the Tube Works Resembling a large tubular flashlight in size and appearance, the advanced development model of the Image Orthi¬ con has an overall length of about 15 inches, with the shank about two inches in diameter and the head about 3 inches in diameter and 3 inches long. It has three main parts: An electron image section, which amplifies the photoelectric current; an improved Orthicon-type scanning section, smaller and simpler than those built before the war; and an electron multiplier section, the function of which is to magnify the relatively weak video signals before transmission. The principle which makes the new tube super-sensitive to low light levels is similar to that which enables RCA’s multiplier phototube to measure star¬ light. This principle, known as second¬ ary electronic emission, involves the use of electrons emitted from a primary source as missiles to bombard a target or a series of targets, known as stages or dynodes, from each of which two or more electrons are emitted for each electron striking it. Light from the scene being televised is picked up by an optical lens system and focused on the photo-sensitive face of the tube, which emits electrons from each illuminated area in proportion to the intensity of the light striking the area. Streams of electrons, accelerated by a positive voltage applied to a grid placed directly behind the photo-sensi¬ tive face and held on parallel courses by an electromagnetic field, flow from the back of the photo-sensitive face to a target. Secondary emission of elec¬ trons from the target, caused by this bombardment, leaves on the target a pattern of varying positive charges which corresponds to the pattern of light from the scene being televised. The back of the target is scanned by a beam of electrons generated by an electron gun in the base of the tube, but the electrons making up this beam are slowed down so that they will stop just short of the target and turn back until it again approaches a positively charged section. The returning beam, with picture in¬ formation imposed upon it by the vary¬ ing losses of electrons left behind on the target, is directed at the first of a series of dynodes near the base of the tube; secondary electrons “knocked out” of this electrode by the bombardment strike a second dynode, and this pro¬ cess continues, with the strength of the signal multiplying at each stage until it reaches the signal plate and is car¬ ried out of the tube through an ex¬ ternal connection. Men Who Developed the Image Orthicon Credit for the tube’s development goes to three members of the RCA re¬ search staff: Dr. Albert Rose, Dr. Paul K. Weimer, and Dr. Harold B. Law. The project is a continuation of RCA Lab¬ oratories’ work on the pick-up tube over the past 20 years under the direction of Dr. V. K. Zworykin, associate director of RCA Laboratories. During part of that period, the work was headed by B. J. Thompson, associate director of the laboratories, who was killed in ac¬ tion overseas in July, 1944, while on a special' mission for the Secretary of War. Y our Best Investment— VICTORY BONDS During the War— E. M. BERNDT CORP. produced sound on film recording equipment that uient to the Armed services. NOW We hope to furnish the same high quality and service to our peace-time customers. Auricon division E. M. BERNDT CORP. 5515 SUNSET • HOLLYWOOD 28, CAL. MANUFACTURERS OF SOUND-ON-FILM RECORDING EQUIPMENT SINCE 1931 FOR LIGHT ON EASTERN PRODUCTION - C. ROSS For Lighting Equipment As sole distributors East of the Mississippi we carry the full and complete line of latest-type Inkie and H.I.-Arc equipment manufactured by MOLE-RICHARDSON, Inc. Hollywood California Your requirements for interior or exterior locations of to the last minute detail anywhere ☆ MOTOR GENERATOR TRUCKS RENTALS SALES ☆ CHARLES ROSS, Inc. 333 West 52nd St. New York. N.Y. Phones: Circle 6-5470-1 taken care SERVICE American Cinematographer • January, 1946 27