Slot for inserting compensators

This is immediately below the analyser and its greatest dimension forms an angle of 45º with the direction of vibration of the Nicols (polariser and analyser).

The main directions of vibration of the compensating plate and those of the polariser and analyser are situated at 45°.

These are plates of anisotropic substances, whose planes of vibration coincide with their two dimensions, length and width.

Accessory plates consist of mineral sections of a thickness such that they produce a known amount of retardation.

They may be wedge-shaped so that retardation (and thus colour) will depend on the thickness acting at any moment in time.

The effects that these compensators introduce are superimposed on the effects that the minerals on the microscope stage introduce.

They are used for studying interference figures and the retardation produced by mineral specimens.

When required, they are inserted into the microscope tube in a slot between the objetives and the analyser.