GB839895A - Improvements in and relating to optical instruments - Google Patents

Abstract

839,895. Polarizing apparatus; microscopes. ABBEY, A. (American Optical Co.). Aug. 16, 1957, No. 26008/57. Class 97(1) In a polarizing apparatus comprising a polarizer and analyzer rotation of the plane of the polarization due to the oblique incidence of plane polarized light on refracting e 1 e - ments is compensated by a phasealtering plate and a "rotary compensator." The latter may be formed by refracting e 1 e - ments normally used and disposed between the phaseshifter and the analyzer or by a meniscus air or glass lens of zero power. In the microscope of Fig. 1, reflected light from mirror 16 is plane polarized at 12 and formed by condenser 18 at 24. Lenses 42 formed on plane 24 transmit parallel light through a half-wave plate 50 to lenses 44 which form the light on an object at 36 an image of which is formed by objective 26 behind a crossed analyzer 30. The plane of polarization of the light emerging from polarizer 12 is rotated due to oblique incidence of some of the light rays in lenses 18 and 42, is reversed by the halfwave plate 50 and additionally rotated by oblique incidence on lenses 44, 26 so that plane polarized light is incident on the analyzer 30. The half-wave plate 50 may be provided by a rhomb giving four internal reflections, at each of which there is a #/8 phase change. In a modified microscope, a unit comprising a half-.wave plate and a rotary compensator formed by a meniscus air or glass lens of zero power may be disposed in the light path between polarizer and condenser and between objective and analyzer; each unit may be axially adjustable. As shown in Fig. 10, such a unit may consist of a half-wave plate 133 and two meniscus air lenses 132A and 132B of which the latter is axially adjustable. Lens 132A and lens 132B together with the half-wave plate may both be adjustably mounted in a tube.