GB1216383A - A refractometer using the critical angle method - Google Patents

Abstract

1,216,383. Refractometers. SOC. D'OPTIQUE, PRECISION, ELECTRONIQUE ET MECANIQUE. July 11, 1968 [July 27, 1967], No.33204/68. Heading G2J. A critical angle refractometer comprises a light source 1, an orientable aiming telescope 2 movable along a graduated dial 3 and an optical element 4 in which a light beam from the source is reflected, having at least one transparent contact surface with the medium 6 whose refractive index is to be measured, and at least two plane reflecting surfaces 9, 10 which cause the beam to be reflected, at least twice, at the same angle of incidence on the contact surface. Fig.1 shows a light beam from lamp 1 entering the prismatic element 4 through surface 11 and being reflected by contact surface 7 at point d 1 , by plane reflecting surfaces 9, 10 and by contact surface 8 at point d 2 into the telescope 2 via exit surface 12. In modifications, element 4 can have a single exit and entry surface and two contact surfaces, a single exit and entry surface and a single contact surface, an exit and an entry surface and single contact surface, an exit and an entry surface and three reflection points on a single contact surface, achieved by suitably positioning tri-rectangular tetrahedrons engaged by their bases to the element.