Patent GB-768727-A (GB)
Title: Optical arrangement for splitting a light beam and for reuniting the (split) light beams
IPC: G02B27/28
Filed: 1954-09-13
Abstract: 768,727. Optical apparatus. ZEISS-STIFTUNG C., [trading as ZEISS, C. [Firm of]]. Sept 13. 1954 (Sept. 19, 1953], No. 26385/54. Class 97(1) An optical system comprises an interference polarizer which divides an incident beam into two partition beams and then reunites the partition beams or several interference polarizers one or more of which divide the incident beam and the remainder reunite the partition beams, optical elements being provided in the partition beams which affect the intensity, spectral distribution, vibration static, degree of polarization or path length of the said beams. As shown in Fig .1 an incident beam JO is divided by a polarizing interference layer 12 into transmitted and reflected beams polarized at right angles the latter being reflected by prism surfaces 13 and 14 to fall on a second polarizing interference layer 12 at which it is combined with the beam transmitted by the first polarizer. By the insertion of colour filters 15 and 16 in the beams additive or subtractive mixtures of colour may be obtained. and if the filters 15 and 16 are replaced by a single polarizer its rotation will vary the intensity of the final beam I. To obtain a resultant unpolarized beam variable in intensity the prism-system 11 may be reversed so that the polarizing layers 12 are parallel and the filters 15 and 16 replaced respectively by polarizing plates arranged with their polarizing axes relatively, inclined. Rotation of these plates will effect the desired change in the resultant beams. A similar arrangement may be used to produce a beam of constant intensity but variable degree of polarization. The reflecting surfaces 13 and 14 may be replaced by polarizing layers blackened on the outside. To produce a monochromatic beam the arrangement shown in Fig. 6 may be employed. An incident beam passes a plane polarizer 61a and is incident an interference polarizer 66a arranged at 45 degrees to the polarizing axis of the polarizer 61a. The beam reflected by the layer 66a is incident on a plane reflector 62a after passage through a quarter-wave plate and is directed back to the polarizer 66a, to join the transmitted beam which has passed a quarter wave plate 63a and been reflected by a plane mirror 63a. The combined beam passes a plane polarizer and is similarly divided and recombined by an interference polarizer 66b. Plane mirrors 62b and 63b and quarter wave plates 64b, 65b. This division and recombination is repeated by an interference polarizer 66c and by suitable dimensioning and positioning of the components a monochromatic beam is obtained. By providing a fourth interference polarizer system the emergent beam may have the same direction as the incident beam. The interference polarizer 60a may be used alone to perform the functions of the system shown in Fig. 1. Alternatively the plane mirrors 62a, 63a may be parallel and on opposite sides of the polarizer 60a. The supporting prisms may be omitted. the interference polarizing layers being carried by a transparent plate. The system may be used in the projection of stereo pictures 91, 92, Fig. 9, in polarized light produced by dividing the beam from a condenser by an interference polarizer 95 and recombining the beams by a similar polarizer 96, after reflection at prisms 93, 94, for projection by an objective 98. The polarizers 95, 96 may be carried on transparent plates, the prisms 93, 94 being replaced by plane mirrors.