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Objectives:
DIN acrhomatic objectives are corrected for chromatic(colour) aberration. Your
microscopes may be equipped with Semi-plan or Plan achromatic objectives which
minimize the effects of curvature of field and produce flatter images. The 4 objec-
tives will be parfocal when properly fix to the nosepiece so it should not be neces-
sary to make large adjustments in focus when changing objectives.
Objectives 4x and 10x have relatively long working distances while the objectives
40x and 100x have a very short working distance. The 40x and 100x objectives are
retractable (spring-loaded in the lens mount) to protect the specimen slide.
Oil immersion objective 100x is made to get the correct magnification with the in-
termediate of immersion oil between the specimen slide and the objective. When
using 100x objective, begin focusing using the lower magnification objective. Put a
drop of oil on the illuminated area of the specimen and rotate the nosepiece to bring
the 100x objective into the optical path. Looking through the eyepiece, turn the fine
focusing handle to bring the specimen into focus. When bringing the objective into
position, pay attention to not introduce air bubbles into the oil as the bubble will
interfere with your observation. If an air bubble is introduced in to the oil it can eas-
ily be removed by turning the objective to the right and left slightly still touching the
oil on the slide. The air bubble will disappear. After using the 100x objective, be
sure to wipe off the oil thoroughly from the objective and the slide using a soft clean
cloth or lens tissue moistened with Xylol.
The objectives 40xR and 100xR are sealed to prevent damage from contact with
immersion oil, although the oil is not required for use with objective 40xR.
The high power objective requires bright light rays matching the Numerical Aper-
ture of the objective. The NA of the 100x objective is 1.25 and a condenser with
NA1.25 should be used with it. Numerical Aperture(NA) refers to resolving power
limits, and is expressed with formula NA = N x Sin U, N is refractive index of me-
dium (air or oil) between objective and slide, and U is half of the aperture angle.
Larger NA number relates to larger resolving power.
Eyepiece:
One pair of Wide Field eyepieces WF10x are supplied, having Field Number of 20
or 18. The FN20 eyepiece offers extra wide field of view and the high eye point of
18.8mm. The FN18 eyepiece has the eye point of 18.5mm, and a 19mm diameter
micrometer disc can be installed in it as option. The actual field of view of the mag-
nification is calculated as follows.
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