To analyze:
The reason for parfocal microscope objectives.
Introduction:
Microscopy is a technique of observing an object under a microscope that is not observable with naked eyes. The types of microscopy include scanning probe microscopy, electron microscopy, and optical microscopy. Optical microscopy uses light for illuminating and lenses to magnify the sample.
A light microscope uses two lenses, objective and condenser lenses, for magnifying the sample under observation and an eyepiece lens (ocular lens) for observing the sample. The lens of eyepiece has a fixed power of 15x or 10x. In a microscope, there are 3-4 objective lenses that define the magnification. The power of objective lenses ranges from 4x to 100x. The condenser lens is aimed at focusing the light on the specimen. Condenser lens of power 400x or above are most useful.
Parfocal objectives of a microscope help in retaining the focus of the microscope while switching lenses. The stabilized focus of the microscope helps in easy focusing of the sample.
It is desirable that microscope objectives be parfocal because it helps in retaining the focus of the microscope while changing lenses.