Lichtempfindliches Element

摘要

672,052. Discharge apparatus. RADIO CORPORATION OF AMERICA. Feb. 27, 1950 [Feb. 28, 1949], No. 4974/50. Class 39 (i). [Also in Group XL (b)] The photo-sensitive plate of a transmitter tube of the orthicon or iconoscope type or of a vacuum tube element employed in connection with a flying light spot employs as the lightsensitive material red amorphous selenium, i.e. the form produced by vaporization of selenium in vacuo and its deposition on a cool surface, preferably maintained at a temperature below 50‹ C. In a tube of the orthicon type, Fig. 3, the amorphous selenium 42 is carried on a conductive plate 40 mounted on the end 36 of the tube 30. The selenium to be deposited on the plate 40 is placed in a small cavity 43 and vaporized by local heating-the plate 40 being maintained in a cool condition so that the vapour is deposited thereon. The electrode system for the tube comprises the cathode 44, grid 45 and a positively-charged accelerating electrode 46 having a beam-defining aperture 48 in its forward end. A wall coating 38 acts as a focusing electrode and a decelerating ring electrode 54 aids focusing around the edges of the signal plate. Surrounding the tube are deflection coils 56, focusing coils 58 and small alignment coils 60 to compensate for mechanical misalignment of the electron gun or target. In the iconoscope arrangement, Fig. 4 (not shown), a collector electrode in the form of a metal ring is disposed between the signal plate and a viewing window through which the picture is projected on to the selenium surface. A cylindrical accelerating electrode has an entrance aperture and an exit aperture which includes an annular focusing electrode. In a further modification, Fig. 5, the flying spot is generated by a cathode-ray tube 116 and the photo-sensitive elements disposed in an evacuated envelope 126 comprise a light-transparent film 134, a coating 132 of red amorphous selenium, a thin plate 130 of semi-conducting material and a mosaic 136 of a photo-emitting material, such as silver oxide in combination with caesium. The collecting electrode 122 comprises a coating of conducting material, e.g. stannic oxide or a metal, and is connected to ground via a resistor 138 to provide the output video signal. In operation the photo-emitting surface is charged negatively in accord with the picture intensity by the conduction of the selenium in response to the varying light and the flying spot causes electrons to be emitted and to travel to the collecting electrode 122. The conductive signal plate electrode in contact with the selenium may be gold, platinum, aluminium, beryllium, sputtered palladium or silver.