OPERATIONZEISS Illumination and contrast methods in transmitted light Axiolab 5110 430037-7444-001 05/2019• Configure the microscope as for transmittedlight brightfield microscopy using the KÖHLERmethod (see section 4.2.1).• Swivel the polarizer (Fig. 4-13/3) into the beampath and, if it is rotatable, position it at 0°.• Swivel the analyzer into the beam path andbring into a crossed position with the settingwheel. (The field of view will now appear dark)• Place the specimen on the stage and focus onit.• Swivel the analyzer into the beam path (Onposition) with rotary knob A (Fig. 4-17/2). Thepolarization direction can be changed using thesetting wheel (Fig. 4-17/4) of the analyzer.ATTENTIONThe movements of rotary knobs A and BL and the respective setting wheels are coupled toeach other. Only one control element should therefore be operated at a time and themovement of the other should not be inhibited or blocked. Otherwise, mechanical damagemay occur.NOTEIf rotary knob BL is set to the On position, rotary knob A will be automatically set to the On ifit is not already there.If, on the other hand, rotary knob A is set to the Off position, rotary knob BL will beautomatically set to the Off position if it is not already there.• Place a selected crystal in the center of the crossline reticle.• Swivel in the objective N-Achroplan 50x/0.8 Pol or EC Plan-Neofluar 40x/0.9 Pol and focus with thefocusing drive.• If necessary, close the luminous-field aperture to avoid superimposition of axial figures of neighboringcrystals on the axial figure. The smallest crystal range that can be faded out is approx. 170 μm.• Switch on the Bertrand lens BL (Fig. 4-17/1) (Position On). The axial figure will appear in the field ofview.• Bring the axial figure into focus with the setting wheel (Fig. 4-17/5).(3) EvaluationCrystalline anisotropic specimens can be separated into optical uni- and biaxial, in each case with an"optically positive" or "negative" character.Uniaxial crystals display a black cross when the optical axis is parallel to the direction of view.Depending on the level of birefringence and the specimen thickness, concentrically arrangedcolored interference rings (so-called isochromes) may appear (see also Fig. 4-12, second row).Fig. 4-17 Axiolab 5 for transmitted lightconoscopy
