GB1456286A - Arrangement for measuring the departure of a bundle of parallel light - Google Patents

Abstract

1456286 Measuring light beam deflection refractive index CARL ZEISS JENA VEB 23 July 1974 [25 July 1973] 32493/74 Heading G1A A system for measuring deflection of a beam of parallel light has a slit 3 illuminated by source 1 and imaged in plane 6 by condensing and imaging objectives 4, 5; a further objective 10 imaging an object field 9, in the parallel beam between objectives 4 and 5, at the detector plane 8 and an optical element 7 in the image plane 6. The optical element is a glass plate with strips or edges of areas which cause a phase shift of 180 degrees and is placed in the diffraction pattern of the slit so as to maximize or minimize the light intensity at detector 8. Lateral movement of the parallel beam by an object at 9 will change the intensity at the detector and the movement can be measured either from the change or by moving a beam displacing element, either manually or automatically to compensate for the change. The system may be used to measure refractive index of a flowing liquid using a wedge shaped cell for each of a reference and the unknown liquid. Several alternative arrangements are described. A plane mirror may reflect parallel light to the collimator lens which serves also as an imaging lens and a half silvered mirror may separate the beam. Optical element and slit may be rigidly mounted together with reflection of parallel light by a mirror which is not perpendicular to the optical axis of the collimator. When measuring refractive index, the beam may be positionally restored by contrarotatable optical wedges.