Published online by Cambridge University Press: 14 March 2018
The customary illumination by a ‘coverglass’ inclined at 45 degrees is replaced by a double reflection. The beam from the horizontal collimating tube is first reflected from a highly reflecting mirror at the back of the unit, then downward from a coverglass placed at the top of the unit. With this arrangement the coverglass is inclined at less than 22½ degrees to the axis of the microscope, with a similar reduction of the angle of incidence. The correction ratio for rotation by upward passage of light through the coverglass is now reduced from 6:5 to the almost negligible value 21:20. There is a corresponding improvement in the homogeneity of extinction over the microscope field.
page 726 note 1 Hallimond, A.F. and Taylor, E.W., Min. Mag., 1953, vol. 30, p. 49.CrossRefGoogle Scholar
page 726 note 2 A.F.Hallimond, Manual of the polarizing microscope, 2nd ed., 1956, p. 99.
page 726 note 3 0.S Heavens, Optical properties of thin solid fihns, 1955, p. 240.
page 727 note 1 L. Holland, Vacuum deposition of thin film., 1956, p. 512.