Microscope objectives may be grouped into broad catagories based on their use and optical corrections
Designation
Spherical correction
Color correction
Addn'l properties
Achromat
1 wavelength (green)
2 wavelengths (B&R)
Fluorite
2 wavelength (B&G)
2 wavelengths (B&R)
Low internal fluorescence
Apochromat
3-4 wavelengths (RGB)
4-5 wavelengths (RGB)
"Plan" or "Plano"
Flat field of view
Phase
Contain a Phase Plate 1, 2 or 3
"W"
Corrected for water immersion
Pol
Strain-free glass, used for PLM
Has a Correction Collar
Can be corrected for coverslip thickness (usually 0–2mm thick)
"ICS", ∞
Infinity Corrected System
LWD, ELWD
Refers to the working distance: Long, Extra-long, etc.
EPI
Objective with an outer ring for transmitting light to the top surface of a sample.
Field curvature is the property of an objective lens whereby on- and off-axis imaging describes a curved field. When using such a lens the sample center and extremities would not be in focus at the same time. Lenses corrected for field curvature are called "Plan" lenses.