22
Significance of Objective Name
(Examples)
M
PL
FL
N
100
BD
(Plan)
None : Brightfield
BD
: Brightfield/darkfield
BDP : Brightfield/darkfield or
polarized
IR
: IR light
Figure : Magnification
None : UIS
N
: UIS 2
None : Achromat, or aberration correction with 2 wavelengths (red and bleu).
FL
: Semi-Apochromat, or color aberration correction with visual wave-
lengths (bluish purple to red).
APO : Apochromat, or color aberration correction with all visual-domain
wavelength (purple to red).
PL : Plan, or correction of image curving on peripheral area.
M
: Metal observation (no cover)
LM : Long-WD metal observation
SLM : Superlong-WD metal observation
LC
: Observation over glass plate
Glossary of Terms Used in the Optical Characteristics Table
Working distance (WD)
: The distance from the top of specimen and the front lens of objective.
Number of aperture (NA) : Important figure determining the objective characteristics (resolution, focal depth and bright-
ness).
Resolution ............. Increases in proportion with the NA.
Focal depth ......... Decreases in proportion with the NA.
Brightness ............. Proportional with the square of NA (comparison under the same magnification).
Resolution
: The limit that an objective can identify the images of two points that are close to each other,
expressed as the distance between the two points on the specimen.
Depth of focus
: The maximum depth of the specimen at which the entire specimen can be brought into focus
simultaneously. This value increases when the aperture iris diaphragm is narrowed and de-
creases when the objective NA is increased.
Field number
: The diameter of the image area that can be observed through the eyepieces, expressed in mm.
Field of view
: The diameter of the area observable on the specimen, expressed in mm.
