SILVER
150
SERIES
| 13
SILVER
LINE
When light rays pass through air from the specimen to the objective lens, they are distorted
slightly, a phenomenon known as refraction. This is usually not a problem at a magnification
of 400X or lower. However, at a magnification of 1,000X and above, refraction becomes
problematic. This problem is reduced significantly by placing a thin layer of very clear,
viscous oil between the slide and tip of the objective lens. The result is a much clearer image
at 1,000X because the oil has the same light transmitting properties as glass. Using oil slight-
ly increases the resolution and brightness of the image. Usually a very thin slide (size #1) is
used for oil immersion because at this magnification, the working distance is very small and
is critical to focusing the specimen. Good quality glass (not plastic) cover slips should be
used. If their thickness is over 0.17mm, the objective will not resolve properly, because the
specimen cannot be moved close enough to the objective lens to be in focus. Place a tiny
amount of oil (only 1 drop should be sufficient) onto the slide prior to rotating the 100XRD
objective into position. It is essential to thoroughly clean the objective tip after use to prevent
damage and to ensure that an image can be seen clearly the next time the objective is used.
Please contact Motic Optical or your authorized Motic dealer for the appropriate immersion
oil to use.
IMPORTANT:
The working distances of the 40XRD and 100XRD objectives to the slide
surface are very small and although these objectives are sealed to prevent oil contamination,
it is a good practice to avoid dragging these objectives through an oiled slide. The 100XRD
oil immersion lens on Motic microscopes has a spring-loaded end to prevent cracking the
cover slip upon its initial contact. Once this zone of safety is exceeded by moving the slide
further toward the lens, a point can be reached where damage will occur. Always make a
practice of frequently checking the position of the lens on the slide. Note that a 100XRD
objective requires an iris diaphragm for brightfield oil immersion microscopy.
Motic's patented POINTMASTER
®
eyepiece reticle, which is installed in the eyepiece of the
microscope, enables the user to easily measure the size of the specimen.
1. The numbers on the chart indicate the actual size of the POINTMASTER
®
scale in millime-
ters. For example, the length is 1.0mm from the top of the arrow to the bottom; the total
length of the scale is 8.0mm, etc. The thickness of all the horizontal lines is 0.01mm.
2. To obtain the actual physical size of a specimen, divide the POINTMASTER
®
scale
readings by the magnification of the objective lens that is in use. Divide the readings by 10
if the 10X objective is being used, 40 if the 40XRD objective is in use, or 100 if of 100XRD
is in use.
100XRD Objective
Immersion Oil
Slide
0.5
1.0
0.1
0.5
0.5
0.5
0.2
0.35
2.5
2.5
8.00
1.0
0.5
UNIT: mm SCALE: 20/1
OIL IMMERSION
For 100X objective
HOW TO USE THE POINTMASTER
®
EYEPIECE RETICLE
