Care and Use of the Olympus CH30 Compound Microscope
Introduction:
We will use the Olympus CH30 compound microscope several times over the course of this
semester. The purpose of this hand-out is to familiarize you with its parts as well as how to
handle it properly.
Lab Exercises:
1. Examining the Parts of the Microscope
The parts of your CH30 scope are described below and are identified in Figure 1. Take a few
minutes to identify each of these parts on your microscope and on the figure provided.
Review the function of all parts before using the instrument.
Figure 1. Olympus CH30 Microscope parts.
1
NOTE: Please be sure that you use both hands when carrying your microscope. One hand should
firmly grip the arm while the other supports the base. Keep the instrument upright and level while
you are carrying it. This is to prevent the oculars from falling out. NEVER carry this expensive
instrument with one hand. Also, do not try to slide the scope on your bench, instead, lift it to move
it to a new position.
The basic components of a microscope are a system of lenses and focusing controls. Identify the
BASE, the ARM, and an OBSERVATION HEAD, which houses the OCULAR LENSES that are also
called the EYEPIECES. At the bottom of the OBSERVATION HEAD is a revolving NOSEPIECE
also called a TURRET, which houses a series of OBJECTIVE LENSES. Directly under the nosepiece
and the objective lenses is the flat STAGE. Beneath the opening in the center of the stage is another
lens system called the CONDENSER. The condenser concentrates and focuses the light received
from the light source (lamp) below. Its function is analogous to the function of the lens of your eye
that focuses the light on your retina.
Built into the condenser is the IRIS DIAPHRAGM. The iris diaphragm works like the iris of your eye
to regulate the amount of light that enters. Hence, opening the diaphragm lets more light in and
closing the diaphragm lets less light in. It is important to note that less light is needed to view an
object under a low power objective than is needed to view an object under high power. Therefore,
when you move from low to high power (or high to low), you will probably need to adjust the light
intensity with the light intensity knob and the iris diaphragm.
Each of the OBJECTIVE LENSES screwed into the nosepiece has a different power of magnification, which is stamped on the side of the objective. Your Olympus microscope will have
a 4.0X, a 10X and a 40X objective. Note that as you go from lower to higher power of
magnification, the objective lens is longer. In other words, the low power objective is the
shortest lens, the intermediate is longer, and the high power is the longest of the objective
lenses. A 4.5X objective lens will magnify the object 4.5 times; a l0X lens will magnify the
object 10 times; a 40X lens will magnify 40 times.
The OCULAR lenses or EYEPIECES at the top of the observation head also have their power
of magnification stamped on them. To determine the TOTAL MAGNIFICATION of an object
or specimen being viewed, multiply the ocular magnification times the magnification of the
objective lens you are using. For example: viewing an object with a l0X ocular and a 10X
objective gives a total magnification of 100X.
Two focusing controls complete the basic components of your microscope. One of the controls
is called the COARSE FOCUS ADJUSTMENT and the other is called the FINE FOCUS ADJUSTMENT. These focusing controls adjust (increase or decrease) the distance between the
objective lens and the specimen on the stage, bringing the object into focus. Note that the
coarse adjustment knob is larger than the fine adjustment knob. Work both of the controls
described above and observe how each affects the distance between the objective lens and the
stage.
The COARSE FOCUS adjustment knob is used to initially focus the object to be viewed when
it is under the low power objective magnification. Turning the coarse focus adjustment
changes the distance between the objective lens and the object on the stage rapidly and in
greater increments with relatively little turning and therefore allows you to get the object
into focus more quickly. When using the high power objective lens, the distance between the
2
objective lens and the object is very small and that is why under high power magnification,
only the fine focus adjustment is used. THE COARSE FOCUS ADJUSTMENT SHOULD
NEVER BE USED WHEN VIEWING AN OBJECT UNDER HIGH POWER.
The FINE FOCUS adjustment knob “fine-tunes” the image to an exact, sharp focus. The fine
focus adjustment moves in very small increments in adjusting the distance between the
specimen and the objective lens. Note that our microscope is PAR FOCAL. This means that if
the image is in focus at one power, when you switch to another power, the image should
remain in focus and should only require fine-tuning with the fine focus adjustment knob.
Therefore, you should always first focus the image under the lowest power using the coarse
focus adjustment, then switch to a higher power objective and use the fine adjustment at the
higher power to adjust the focus. Using this procedure will ensure that you don’t smash an
expensive objective lens into the slide on the stage, thus scratching and damaging the lens.
2. Operation of the Microscope
Position your microscope with the oculars facing you, plug it in, and turn on the main light
switch on the right side of the arm. Note: your Olympus microscope is equipped with a stage
locking control. This control can also be used to pre-focus. In any case, when the lever near
the coarse focus adjustment knob on the left side of your microscope has been engaged
(pushed down, towards you), the coarse focus is locked and you will not be able to use the
coarse focus. However, you will be able to continue to use the fine focus. To unlock, gently
push the lever up and away from you.
Next, make sure that the eyepiece diopter (a ring in the left ocular) is set at the 0 position
and that the condenser lens (under the stage) is positioned at the highest point.
Make sure that the stage is lowered all the way down, by turning the coarse focus knobs.
Also make sure that the lowest power objective lens (the shortest one, the 4X with red ring)
is in position and place a practice slide on the stage (colored threads or the letter “e”), centering the specimen to be observed over the hole in the stage using the mechanical stage
controls. Without looking through the microscope, slowly decrease the distance between the
slide and low power objective until it almost touches the slide or the distance can no longer
be decreased. Adjust the light intensity with the light intensity control knob located just
under the light switch, to a comfortable level.
Next, adjust the interpupillary distance. While looking through the eyepieces, adjust for
binocular vision by pushing or pulling the oculars until the left and right fields of view
coincide completely (i.e., until the two circles of light merge to form one). Looking through
the oculars, FOCUS the object into view by using the coarse adjustment to increase the
distance between the object and the lens. Refine your image with the fine adjustment.
Now adjust the diopter on the left ocular. To do this, close your left eye and with your right
eye look down the right eyepiece. Adjust the coarse and fine focus until you get the best
(sharpest) image. Next open the left eye and adjust the diopter until you obtain a sharp
image in both eyes.
You may need to adjust the light intensity (using the light intensity control knob) again. FOCUS the specimen into view by using the coarse focus adjustment to increase the distance
3
between the specimen and the lens. Refine your image using the fine focus adjustment.
Remember that it is best to always focus by increasing the distance between the stage and
the objective. Manipulate the iris diaphragm in the condenser (located under the stage) to
generate the most detailed image possible.
Move the slide on the stage to examine different portions of the specimen. This scanning will
help to locate areas of particular interest. Once something of interest is located, rotate the
nosepiece to the higher power objective. FOCUS WITH THE FINE ADJUSTMENT ONLY.
REMEMBER: NEVER USE THE COARSE ADJUSTMENT ON THE HIGHER POWER
OBJECTIVE. Usually both the low and the high power objectives are nearly in focus (par
focal), so that little adjustment is necessary. Again, manipulate the iris diaphragm to achieve
the best image quality.
When you finish using the microscope today and are ready to return your microscope to its
space, you must do the following:
•
•
•
•
•
•
•
•
•
remove any slide from the stage
lower the stage to the lowest position
make sure the lowest power objective lens is in place
engage the safety stage lock by gently pressing the stage lock lever downward
turn the light intensity to the lowest position
turn the light switch to OFF position
unplug the microscope and NEATLY wind the cord around the arm put the
microscope back into the proper slot in the cabinet
wipe the objective lens with lens paper
wipe the stage with Kimwipes making sure it is clean and dry
Note: Please report any problems with the instrument to your instructor. Microscope repair
tags are available at the front desk. Do not put a defective microscope back into the cabinet
without a tag.
4