An expanded account is given of a simple modification to an ordinary beam-splitting microscope, which renders it stereoscopic. The full aperture of the objective is used, so the method is applicable to all powers of the microscope. The method involves dividing the lower focal plane of the condenser into left and right halves with opposite polarization by means of Polaroid, and isolating the two resulting beams in the eyepieces with Polaroid analysers. This system, first published by Jackson(1944-9), gives excellent results with the highest powers of the microscope, but appears to have been forgotten. this paper is written in the hope of re-introducing it.
A simple and accurate method of ensuring axial illumination is described. It involves examining a suitable cardboard disk held in the substage filter-holder and checking that the image of the field-stop is central in the field of view.
The formula for vertical measurement by means of the fine adjustment of the microscope, n 2 / n 1 x measured depth = real depth, is true, where n 2 is the refractive index of the object and n 1 is that of the immersion medium of the objective lens . The refractive index of the mountant is unimportant. Several additional complications of this method of measurement suggest that it should not be used unless it cannot be avoided, or rough figures are required quickly.