Optical process for the exploration or reconstitution of pictures and device for carrying out said process

摘要

317,791. Soc. Independante de Telegraphie sans Fil. Aug. 22, 1928, [Convention date]. Television.-In a scanning device the picture is illuminated by elliptically polarized light each picture - element being characterized by a particular orientation of the ellipse axes. At the transmitter the main lightbeam passes from the source 1 through a collimator 2, 3, totally-reflecting prism 6, polarizer 11, and divided cube 9 to the picture 10. The cube 9 is formed of two totally reflecting prisms, having different refractivities and joined base to base, so that light is both transmitted and reflected at this plane of contact. The light then passes through two scanning prisms 12, 13 so constructed that each elementary pencil composing the beam is rotated through an angle individual to it. The scanning-prism 12 comprises two wedges, fixed base to base, one being of laevo rotatory quartz and the other deutro-rotatory, the dimensions being such that the light at one edge of the picture is polarized perpendicularly to that at the other edge. The second scanning-prism 13 is similar but imposes a smaller degree of rotation and is turned through a right-angle with respect to the scanning- prism 12. A rotating analyser 14 extinguishes each picture element in succession. In order that the scanning-point may be sharply illuminated while the rest of the picture is uniformly illuminated, an auxiliary beam, passing through reflecting prisms 4, 5 and polarizers 7, 8, is employed. The polarizers 7, 8 are so set that the auxiliary beam is polarized at right-angles to the main beam and is of weaker intensity. Adjustment is checked by means of a photoelectric cell 16. A similar arrangement may be adopted at the receiving station, a paper or oiled fabric screen at 15 being illuminated directly or from behind while the source 1 fluctuates in accordance with the signals.