. Beck microscopes. Microscopes. w^. Fig. 4 Duplex dark ground (visual) and The illuminator (Fig. 4) consists of a large size concentric focus- sing dark ground illuminator in which the optical parts have a central aperture into which is fitted a quartz condenser. Both these systems can be simultaneously focussed upon the object, and by blocking out the appropriate apertures at the back of the condenser, either dark ground illumination with visible light, or ultra-violet illumination with trans- mitted light is employed according to which source of illumination is being used. For dark ground i
. Beck microscopes. Microscopes. w^. Fig. 4 Duplex dark ground (visual) and The illuminator (Fig. 4) consists of a large size concentric focus- sing dark ground illuminator in which the optical parts have a central aperture into which is fitted a quartz condenser. Both these systems can be simultaneously focussed upon the object, and by blocking out the appropriate apertures at the back of the condenser, either dark ground illumination with visible light, or ultra-violet illumination with trans- mitted light is employed according to which source of illumination is being used. For dark ground illumination with ultra-violet light a special type of illuminator devised by Mr. Smiles is supplied which gives a power- ful illumination and with which short exposures can be given. An interferometer is supplied to measure the movement of the transmitted and objectives in terms of wavelengths of light. A mirror fitting [aa, Fig. 3) is provided which can be fitted to the objective bracket (/). This carries a flat mirror which can be tipped by two adjusting screws {ab). Another fitting [ac] is fixed to the body of the focussing unit [k). This includes a plane plate of glass {ad), a thin glass reflec- tor and an observing microscope (aA). A small mirror [ae) receives light from the mirror [af, Fig. 1) of the mercury lamp and reflects this down on to the thin glass reflector, which in turn reflects it upon the interferometer plates. These are moved close together by means of the rack and pinion [ag) and the first interferometer mirror is adjusted parallel to the second by means of the two screws [ah). The observing microscope [ah) is then swung round to a convenient position and the shift of the interference bands can be observed when the fine adjustment is actuated. (C) The optical bench (C, Fig. 1) consists of a triangular section bar rigidly fixed to the main frame (A) at right angles to the axis of the microscope (B). Three fittings slide along this bar. The first carries
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Keywords: ., bookcontributorgersteinuniversityoftoro, booksubjectmicroscopes
