Polarizer for producing uniformly polarized light with aid of interference polarizers and phase retarders

摘要

743,502. Polarization apparatus. ZEISSSTIFTUNG, C., [trading as JENAER GLASWERK SCHOTT & GEN.]. May 4, 1953 [May 17, 1952], No. 12249/53. Class 97 (1). To produce uniformly polarized light, particularly for headlights and stereoprojectors, a polarizer is provided comprising lighttransmitting bodies in the form of a plate having parallel light-entrance and exit surfaces with bands impervious to light arranged between the light entrance surfaces, the bodies carrying interference polarizing layers inclined to the entrance surfaces so that collimated light is incident thereon at angles larger than 45 degrees, reflecting layers directing the light reflected by the interference layers back to its original direction and phase-retarding foils so arranged that all light leaving the polarizer is in the same polarization condition. As shown in Fig. 2, the polarizer comprises glass prisms 23, 24, 25 formed into a plate having light entrance surfaces 21, surfaces 22 impervious to light and interference polarizing layers 26, 27 and 28 arranged as shown, the rays polarized perpendicular to the plane of the drawing being indicated by dots and those polarized parallel to that plane by small horizontal lines. The planes 26 may alternatively be simple reflecting planes. The phase-retarding foils 29 may be arranged behind the layer 28 as shown or be arranged on the exit surface opposite the corresponding entrance surface. The layer 27 may be omitted and the layer 28 inclined to extend beyond the projection of the surface 21 on the exit surface. In the modification shown in Fig. 4 the interference layers 43, 44 and 45 are arranged on two prismatic bodies shaped and assembled as shown to provide light entrance surfaces 48 and impervious portions 49, polarization foils 50 being provided in the paths of the reflected rays which are as shown. The surfaces 46 and the portions of the layers 45 between A and B may be reflecting. Alternatively the foils 50 may be placed in the directly transmitted beam. Fig. 6 shows a further modification in which a plate 51 having prismatic portions forming isosceles triangles in section and carrying the interference polarizing layers 56 is joined to a plate 52 having recesses forming the lightimpervious bands and having surfaces 59a bearing the polarizing foils 59 being made reflecting or so arranged as to act as total reflectors for light reflected by the layers 56. Specification 707,060 is referred to.