Patent GB-781166-A (GB)
Title: Facsimile apparatus
Inventor: STAMPS GEORGE MORELAND
IPC: H04N1/16
Filed: 1953-07-22
Abstract: 781,166. Copying-telegraphy. FAXIMILE, Inc. July 22, 1953, No. 20333/53. Class 40 (3). In apparatus for continuously scanning a subject or a recording sheet for transmission or reception respectively, wherein a single fixed line is scanned by scanning members including one opaque rotatable member having a narrow continuous spiral or helical slit or window of at least one turn associated with a stationary opaque element having a linear slit or window to define a continuously moving parallelogrammic scanning aperture, the curved slit or window is formed by a photographic method as a transparent line on an opaque backing or supporting member. In the transceiver scanning arrangement, Fig. 1, the disc 50 having the spiral transparent slit 47 is rotated by a motor 40 driving rollers 32 supporting the transmitting or recording sheet 31. For transmission, the light source 76 is energized and the reproducing light source 52 swung back on its hinge 56 so that an image of an area of the sheet 31 is projetted to the plane of the member 48 carrying the linear slit 49. The resulting scanning spot is focused by a lens 64 on to a photo-cell 67. When the scanning arrangement operates for the reception of a picture, the light-source 52 is swung back into operative position and the scanning light 76 cut off so that a modulated light spot, projected via slits 49 and 47, scans successive lines S on the recording sheet 31. In a modification for scanning stationary films, particularly micro films, Fig. 7 (not shown), the image of an area of the film is traversed over the linear slit, behind which the spiral slit is rotated. In a further modification, Fig. 8, a horizontal strip of a film 84 moved continuously at right angles to the plane of the Figure and illuminated by elongated lamps 85, 89 above and below the strip is projected by a lens 73 on to a linear slit 49 in an opaque member behind which is a disc 88 with a multi-turn spiral slit 90 associated with a single turn slit 47<SP>1</SP> in a disc 50<SP>1</SP> rotated at a speed less than that of the disc 88. The scanning spot is projected by a lens 64 on to an elliptical mirror 86 and then from a smaller mirror 87 to a photo-cell 67. A further modification, Fig. 14 (not shown), employs a modified Schmidt projection system in conjunction with elliptical reflectors similar to 86, 87 of Fig. 8. An arrangement for deriving the spiral slit is shown in Fig. 15 in which a disc 100 is connected to a disc 115 by a shaft 101 rolling on inclined knife-edge members 102, 103. A light spot derived from a light source 121 and apertured screen 119 is projected by a lens 116 to a point P on a diameter D of the disc 100, and traces a spiral SP on a photo-sensitive sheet 124 as a cam disc 114 connected to shaft 101 is rotated by a pulley 100. The sheet 124 when developed is a negative 125 having a black spiral line 126 on a transparent base 127 from which a print is made giving a transparent line 47 on an opaque background 128. The linear slit in the plate 48 may be derived by a photographic process in which light beams 147 are passed through a plate 145 carrying a wire 143 contacting a photo-sensitive layer 146 on a supporting plate 48<SP>1</SP>, as indicated by Fig. 23. A helical slit on a drum may be derived by employing the method shown in Fig. 23 to form a diagonal transparent line in a rectangular opaque sheet which is wrapped around a transparent drum. To provide the equivalent of a chopper frequency the light source 121 may be modulated at a desired frequency so that the spiral track has corresponding transparent and dark portions along its length.