GB735745A - Multi-path optical systems - Google Patents

Abstract

735,745. Optical systems. RADIO CORPORATION OF AMERICA. June 16, 1953 [June 28, 1952], No. 16594/53. Class 97 (1). In a light-dividing system comprising at least two partial reflectors arranged in series to produce at least two subsidiary light beams and a direct beam of substantially equal intensity each reflector comprising a transparent body supporting a layer reflecting and transmitting different colours, a transparent compensating member of substantially the same thickness as that of each reflector and of the same refractive index as the supporting bodies thereof is inserted in one of the beams to equalize astigmatism for paraxial and oblique rays. As shown in Fig. 1, for the purpose of effecting colour correction of three transparencies 16, 17, 18 they are illuminated by light from the spot of a cathode ray tube 11 by way of a lens 12 and light dividing system 13, the resulting light falling on photo-cells 23, 24, 25. The system 13 comprises a member 14 consisting of a semi-reflecting layer supported between two glass plates and reflecting a beam to the transparency 17, the beam passing through an inclined plate 26 of the same material and thickness as the combination of plates in the member 14. The beam transmitted by the member 14 is divided by a similar reflecting member 15 to fall on transparences 16 and 18. By this arrangement each beam will have passed through a thickness of glass equal to twice the thickness of each of the members 14, 15 and 26 and will have been incident on these members at the same angles so that the beams will have the same astigmatism. In the modification shown in Fig. 4 the beam from the lens 38 passes an inclined plate 39, is partly reflected by a front surface reflector 44, the reflected beam being divided by a further front surface reflector 45 whereby three beams are formed, the.astigmatism in the beams being again equalized by an inclined plate 43.