Operation Manual

4.4 Using an oil immersion objective

Oil immersion objectives are labelled with the additional engraving “Oil” and are to be immersed in oil

between the specimen and the front of the objective.

The immersion oil supplied by Motic is synthetic, non-fluorescing and non-resining oil, with a refractive

index of 1.515

Normally, a cover glass must be used with oil immersion objectives with a few exceptions.

Deviations from thickness are not important as a layer of immersion oil acts as compensation above the

cover glass.

The small bottle of oil supplied with every immersion objective facilitates application of the oil tothe cover

slip.

Remove any air bubbles in the nozzle of the oil container before use.

Immersion oil must be used sparingly.

Freedom from air bubbles must be ensured. To check for air bubbles, remove one eyepiece, open the

field diaphragm as far as possible and look at the exit pupil of the objective within the eyepiece tube (the

exit pupil will appear as a bright circle).

If it is difficult to see if there are any bubbles, use a phase centering telescope and rotate the eyepiece

part of the centering telescope to focus on the exit pupil of the objective. Air bubbles in the oil will

deteriorate the specimen image. To purge bubbles, swing the immersed objective forward and

backwards by rotating the revolving nosepiece, add more oil, or wipe off the oil and apply new oil.

Place a single drop of immersion oil on the cover glass.

Make contact with the cover glass, and focus.

View and wipe clean the objective with a lens cleaning tissue.

Any residual film of oil remaining on immersion type objective, or where it has spread to the surface of

dry type objective will have a discernible, negative effect on the image.

To remove a film of oil, moisten a lens tissue or clean cloth with petroleum benzine and lightly wipe the

lens surface, wipe the lens surface with absolute alcohol (ethyl alcohol or methyl alcohol).

Petroleum benzine and absolute are highly inflammable. Use great care when handling them.