GB909403A - Improvements relating to systems for producing deformations in the surface of a deformable medium - Google Patents

Abstract

909,403. Television; light modulating. GENERAL ELECTRIC CO. Jan. 6, 1959 [Jan. 13, 1958], No. 485/59. Addition to 909,401. Class 40 (3). In a television receiver in which the deformation set up in a deformable medium 15 when scanned by an electron beam 13 velocity modulated by television signals are utilized to modulate light from a source 23 and thus to project a television picture on to a viewing screen 35 the medium 15 has the property of decreasing in volume resistivity with decreasing thickness. This prevents the scanned area of the medium from decreasing to zero thickness when the force due to the changes (relative to the conducting coating 21) deposited by the scanning beam overcomes the surface tensions from the excess of the medium outside the scanned area since the decrease in volume resistivity results in a decreased time constant for the passage of leakage current from 15 to the coating 21 and an equilibrium condition is then reached in which the force due to the changes is equal to that due to the surface tension. Such a medium should have a volume resistivity that varies within the range of 10<SP>14</SP> to 10<SP>11</SP> ohms per c.c. and an average resistivity at the equilibrium condition of 10<SP>11</SP> ohms per c.c. At the working temperature range of 25‹ to 100‹ C. the viscosity should be in the range 100 to 50,000 centistokes. Suitable materials are (1) butyl esters of methyl- #-carboxyethylisiloxanes, (2) bees wax, and (3) methyl silicone fluids which may contain up to about 5% of phenyl silicones.