Orthoscopic light microscopy
This easy-performing method permits underlining and differentiating birefringent transparent materials. The light beam, which is collimated and at a perpendicular angle to the specimen surface (so called orthoscopic light), is polarized, in main cases linearly, by a polarizer inserted in the light unit; an analyzer is placed in the microscope, above the preparation. For all practical purposes, the collimated illumination would be carried out by Köhler illumination with a very small aperture diaphragm. (see unit UNIT M11G1). See Figure 1.
The polarizer, analyzer, and preparation would be precisely and independently adjustable around the microscope optic axis by means of appropriate mechanisms on the stand. (see Figure 2).
Most of the time, birefringence of the objects, which are observed with polarized light microscope, would form, in white light, some distinct colors permitting to distinguish and locate the various components of the specimen (Figure 3). The colors observed are due to the appearance of fluted spectra that interfere with polarized light. When neutral lines of the specimen's homogeneous regions neutral lines are oriented to \(\pm 45^{\circ}\) to the polarizer, and the analyzer is crossed or parallel to the polarizer, then the visible color would be one of Newton shades[2] 1. (Refer to lessons about physical optics and birefringence and polarization, for example [ Born 1999[1]]).
