OPERATIONZEISS Illumination and contrast methods in transmitted light Axiolab 5100 430037-7444-001 05/2019Inserting a lambda compensator (473704-0000-000) or lambda/4 (473714-0000-000) or a 0-4 lambdawedge compensator (000000-1140-663) in the compensator slot with the initial state of the axial figurebeing as illustrated in Fig. 4-12 results in the following changes in color (shown schematically as blue andyellow areas) to the axial figure, thus allowing differentiation in "optically positive" and "opticallynegative".Optically uniaxial Optically biaxialPositive Negative Positive NegativeLambda plate(white → blue→ yellow)+ = Blue– = YellowQuartz wedge(Direction of motionat insertion) Direction of movementLambda/4 plate(position of blackspots)Fig. 4-12 Determining optical characterIn the case of less favourable sections in which the cross-hair center is optically uniaxial or the isogyres areoptically biaxial specimens outside the objective pupil, an assessment is possible as follows:• If the black isogyres are straight and they run parallel to the pupil (in relation to the cross-hairs), thespecimen is optically uniaxial.• If the black isogyres are curved lines which wander on a circular path through the pupil, thespecimen is optically biaxial.NOTEAxial figures can often be better displayed with circular polarization. In particular, the axisangle of optically biaxial specimens (quasi the distance between the isogyres) can bedetermined more clearly. The optical character can also be determined. The lambdacompensator (6x20mm), arranged in the compensator slot, is used for this purpose.NOTETwo storage compartments for 6x20mm slides are located on the back side of the conoscopystand.
