Patent GB-915082-A (GB)
Title: Improvements in thermoplastic information storage system
IPC: G11B7/24
Filed: 1959-08-21
Abstract: 915,082. Cathode-ray storage tubes. GENERAL ELECTRIC CO. Aug. 21, 1959 [Aug. 25, 1958], No. 28649/59. Addition to 913,971. Class 39 (1). [Also in Group XIX] The recording of digital data on a deformable plastic surface as described in the parent Specification is effected by an electron gun assembly with means for supervising the focusing of the electron beam and the recorded patterns produced. Fig. 1 shows an electron tube with cathode 3, accelerating electrodes 4 and 5, focusing electrodes 15-17 producing a substantially parallel beam, horizontal and vertical deflection electrodes 25, 26 and 27, 28 and further focusing electrodes 22, 23 bringing the beam to a focus on the recording element 13. An inspection turret 38 with three monitoring elements is provided; positioned as shown a phosphor screen 40 provides a luminescent image of the spot which can be examined by a microscope 44 for its size and shape (a rectangular spot about 1.5 x 5 microns is suitable), in a second angular position a beam shadow projector (not shown) forms an image of the spot on a fluorescent screen 48 for observation of the focal plane of the beam (a gauge 50 measuring the axial position of the turret), and in a third position a lens assembly 42 enables inspection of the plastic surface with the microscope 44. The record member 13 may be moved by threaded push rod 56 to a position where the turret 38 can be lowered by means of knob 49 through aperture 53 or 54 for the monitoring; this push rod and another, not shown, at right angles to it enable mechanical positioning of the record member 13 for reading or writing at a desired address, and " developing " of the electron pattern by an induction heater 34. The diffraction pattern produced by the data can be viewed by a microscope 70 when the member 13 is moved into the path of the light from bulb 71 (shown as a broken line). Deflection plates 29 are used to switch off the beam by deflecting it into a Faraday cage 30. The storage member 13 may consist of a blend of polystyrene, m-terphenyl, and a copolymer of butadiene and styrene on a glass base, with a thin interposed conducting layer of cuprous iodide or stannous chloride; this latter may be omitted if the optical developing heater shown in Fig. 6 is used. This heater uses an arc lamp 116 at the focus of a lens 114, the parallel beam being reflected by an annular mirror 117 and brought by lens elements 119 to a focus on the plastic surface to soften it and make it conductive, the reflected and diffracted light forming a colour pattern on a screen 123 so that the viewing system 70-74 of Fig. 1 is not necessary. Fig. 6 also shows a beam monitor 124 which is similar to and replaces the beam shadow projector of Fig. 1; an electron-scattering gold target 127 throws a shadow image of a fine grid 128 on to a phosphor screen 118. Fig. 5 shows a modification of the tube of Fig. 1, having a beam-splitter 80 which produces four beams at an angular spacing dependent on the potential applied to 81 and 82. By switching (89) this potential between two values, two different spacings of the grid formed on storage element 13 may be obtained. Fig. 7 shows a further modification of Fig. 1 in which the platelike storage element 13 is replaced by a drum 160 having a plastic coating, the drum being rotatable and movable axially (as in the parent Specification) for data address-selecting. 152 and 153 are monitoring elements of the type already described and 155 an optical heater and viewer similar to that of Fig. 6.