The microscope table is graduated on its periphery, and, furthermore, carries a vernier for more exact reading.
The polarization microscope is not furnished with an objective nose-piece. Every objective, however, is supplied with an individual centring head, which permits the objective to be attached to an objective clutch-changer, situated at the lower end of the microscope-tube. The centring head permits the objectives to be perfectly centred and to remain centred even if another objective is introduced into the objective clutch-changer.
At an angle of 45 degrees to the polarization plane of polarizer and analyzer, a slot has been provided, which serves for the introduction of compensators.
Between analyzer and ocular, another slot is found which permits the Amici-Bertrand lens to be introduced into the optical axis. The slider for the Bertrand lens is supplied with two centring screws whereby this lens can be perfectly and easily centred. The Bertrand lens serves the purpose of observing the back focal plane of the microscope objective. In order to allow the Bertrand lens to be focused, the tube can be raised and lowered for this purpose. An iris diaphragm is mounted above the Bertrand lens.
If the Bertrand lens is shifted out of the optical axis, one can observe the preparation placed upon the microscope stage and, depending on its thickness or its double refraction, the interference color of the specimen. This interference figure is called the orthoscopic image and, accordingly, one speaks of the microscope as being used as an “orthoscope.”
After the Bertrand lens has been introduced into the optical axis, the interference figure is visible in the back focal plane of the objective. Each point of this interference figure corresponds to a certain direction of the rays of the preparation itself. This arrangement permits observation of the change of the reflection of light taking place in the preparation, this in accordance with the change of the direction of the rays. This interference figure is called the conoscopic image, and, accordingly, the microscope is used as a “conoscope.”
Many types of polarization microscopes have been constructed; those of a more elaborate form are used for research investigations; others of smaller design for routine investigations.