Microscope Troubleshooting Tips
Use a Compound Microscope
Evaluating a Microscope
Microscope Magnification Specifications
Microscope Parts and Specifications
History of the Microscope
MICROSCOPE CARE & MAINTENANCE INSTRUCTIONS
|A Barlow lens is a diverging lens
that alters the focal length of a microscope and, therefore,
the magnification power and field of view. They also alter
the working distance between the objective lens and the
specimen, which is a critical variable for many applications
such as PCB soldering and inspection.
A Barlow attaches to the bottom of the objective lens on a
stereo (low power) microscope when there is a need for
either more or less of one of the following variables:
The most common type of Barlow lens is the Reducing Barlow.
A Reducing Barlow reduces the magnification power of the
microscope, but has the advantage of increasing the field of
view and the working distance between the objective and the
specimen. Reducing Barlows are typically 0.3x, 0.5x and
0.75x although other powers are available.
As an example, a 0.5x Barlow lens will halve the
magnification power of the microscope, but it will double
the size of the field of view. It will also increase the
working distance between the objective and the specimen.
By the same token, a 2.0x Barlow will double the
magnification and halve the field of view of a microscope.
In other words, each different power Barlow has a
proportionate effect on magnification and a direct inverse
proportional effect on the field of view and working
Back To Top
We start with the premise that choosing a microscope should
be an enjoyable process!
That said, there are a number of variables that go into
selecting a microscope system. The process can be a little
daunting. Moreover, there is a bewildering range of quality
- from cheap plastic microscopes to the most expensive
German and Japanese brands.
This article, therefore, provides sensible advice to assist
budding microscopists to make a more educated decision.
We recommend that you refer to the Glossary of Microscope
Terms when reading this guide.
Before we start, you should know that everything in this
article refers to light microscopes; that is a microscope
that includes a built-in light source. There are other types
of microscopes, such as electron or ultraviolet, but they
are significantly more expensive and typically, used in
commercial or scientific applications
II). THE ¡®RIGHT¡¯ LIGHT MICROSCOPE
Microscopes are configured to suit different applications.
It is important to ensure that you purchase a microscope
that is well-suited to your application. There are three
basic things you need to know:
First, a light microscope has two sources of magnification.
The primary source is via the objective lens. The secondary
source is via the eyepiece lens. Total magnification is
achieved by multiplying the (magnification) power of the
objective lens by that of the eyepiece lens.
For example: Standard eyepieces have a power of 10x. When
using a 100x objective lens, the total magnification would
Second, and perhaps most important of all, do not fall into
the trap of being attracted by high levels of magnification.
The vast majority of the world¡¯s light microscope
applications require magnification levels of less than 60x!
Third, you need to know whether you need a compound or
III). COMPOUND OR STEREO MICROSCOPE?
Microscopes fall into two basic categories: Compound or
Stereo, often referred to as high power or low power,
You will need a compound microscope if you are viewing
"smaller" specimens such as blood samples, bacteria, pond
scum, water organisms, etc. The reason is that such
specimens require higher powers of magnification in order to
see the detail. For this reason, a compound microscope is
also known as a high power microscope. Typically, a compound
microscope has 3-5 objective lenses that range from 4x-100x.
Assuming 10x eyepieces and 100x objective, the total
magnification would be 1,000 times. Compound microscopes are
also integrated systems in the sense that the microscope
body and base form an integrated unit.
When considering a compound microscope, you will also need
to decide on whether you want a monocular, binocular or
trinocular microscope. That is to say, a microscope with
one, two eyepieces or one with two eyepieces and a third,
There are four basic variables in this decision:
1. Magnification: Monocular microscopes work efficiently for
up to 1000X total magnification. For higher magnification
levels, a binocular microscope is required.
2. Comfort: Most people find binocular microscopes more
ergonomic and easier to use than monocular. Young children,
on the other hand, find monocular easier to use.
3. Price: While the price ranges overlap, typically a
monocular microscope is the least expensive type of
microscope with trinocular being the most expensive.
4. Application: Most monocular microscopes do not include a
mechanical stage, which is useful for more sophisticated
applications. Most binocular microscopes do include a
mechanical stage. A trinocular microscope is typically used
when a third (trinocular) port is required for
You will need a stereo microscope to view more substantial
specimens such as insects, bugs, leaves, rocks, gems, etc.
Typically, such specimens require lower power, magnification
ranges from 6.5x-45x. Hence they are also known as low power
microscopes. By definition, a stereo microscope has at least
two eyepieces (binocular), and provides a three-dimensional
image of the specimen. They are available in one of two
configurations: dual power or zoom. In the first instance,
the microscope has two magnification options, for example
20x-40x. In a zoom microscope, there is a continuous zoom
range from the lowest power to the highest power. For
example, from 6.5x to 45x.
As with compound microscopes, stereo microscopes also come
in a trinocular configuration for photographic purposes.
Stereo microscopes can be integrated microscopes or,
increasingly often, are modular in the sense that different
stereo microscope bodies can be assembled with different
For most individuals, an integrated system is appropriate.
Some users require specialist microscope bases such as boom
stands for applications such as PCB inspection or engraving
Now that you have decided on the type of microscope you
need, there are several further variables to consider, most
important of which is quality. Quality particularly applies
to construction, lens and illumination. We will consider
each of them.
a). Quality of construction
Most people believe that higher price equates to higher
quality. This is partially true, but overly simplistic in
the same way that it would be in referring to a car. As with
a car, the finest light microscopes in the world tend to be
extremely expensive. There are several well-known German and
Japanese microscope brands that fall into this category.
However, as with Ferrari cars, most people cannot afford
them and do not need that level of refinement.
By the same token, there are a large number of low priced
and low quality microscopes that range from plastic toys to
cheaply made imports. Most of these are made of inferior
quality materials, have minimal optical quality and are
likely to break quickly. The vehicular equivalent might have
been the Yugo! The danger of buying such microscopes is
easily avoided by buying from a reputable microscope vendor.
In our opinion, there is now a healthy selection of fine
quality microscopes that have excellent optics, but without
the high price tags associated with well-known brands. In
other words, like cars, many microscopes are now made that
will achieve the same as the high-end brands, but without
being "fully-loaded" or the brand cachet, so to speak! Our
own Omano microscopes fit into this category. They are
designed with an excellent engine (high quality optics),
offer a comfortable drive (ergonomic design) and do not
break down (reliable everyday use). Perhaps Omano is the
Toyota of the microscope world!
Implicit in such microscopes are design elements such as
solid metal alloys, high quality prisms rather than mirrors
and iris diaphragms not disk type diaphragms, among others.
That said, in our experience, we recommend caution in
purchasing any full-size, light microscope that is priced
less than the following:
b). Optical Quality
Optical quality is largely determined by the quality of the
objective lenses and, to a secondary degree, by the quality
of the eyepieces. The standard for good, quality objective
lenses is an achromatic lens. An achromatic lens is one that
corrects for the fact that different colors refract through
a curved, glass lens at different angles. In "color
correcting," the microscope produces a significantly,
enhanced, "flatter" specimen image of the specimen than
would otherwise be obtained.
However, while achromatic objectives will satisfy most
microscopists, some sophisticated users need a better
quality objective that produces even flatter images of the
specimen with less aberrations than achromatic lenses. These
microscopists will require either semi-plan or plan
objectives. Plan objectives, essentially, are "perfect
lenses" and are usually required for sophisticated
biological research¡..and are double the price of achromatic
Finally, it is useful to ensure that the objectives are DIN
compatible. While DIN (Deutsch Industrie Norm) is not a
measure of quality, DIN objectives are useful since they are
interchangeable from one DIN compatible microscope to
another. Should you lose or damage an objective, you can
easily replace it rather than have to buy a new microscope.
With regard to eyepieces, as a general rule, the wider the
eyepieces the easier the viewing. Ask for Widefield (WF) or
Super Wide Field (SWF) eyepieces. Be aware, however, that
the width of the lens, itself will decrease relative to the
size of the magnification power. In other words, higher
power eyepieces have smaller eye ports.
There are four primary types of illumination: tungsten,
fluorescent, halogen and LED.
In summary, a high quality, pedestal microscope should
include halogen lighting as standard. Halogen produces a
strong, white light and typically, include a variable
rheostat so that the intensity of the light can be adjusted.
All Omano, pedestal, microscopes use halogen light.
b). LED ¨C Portable Microscopes
LED ring lights are commonly used in portable microscopes
and, typically include rechargeable batteries. Portable
microscopes and LED ring lights are useful for microscopists
who wish to use them outside or where there are limited
electrical outlets such as conferences or trade shows.
c). Flourescent Light
Flourescent lighting is typically used in specialist,
epi-flourescent microscopes for biological research and
similar applications. However, fluorescent ring lights, are
typically used as additional light sources in stereo
microscopes when more light is required. These ring lights
should not be confused with fluorescent microscopes.
We recommend against buying a microscope with tungsten
lights. They produce yellowish light and excessive heat. No
high quality microscope will include tungsten lighting.
VI). OTHER CONSIDERATIONS
a). Iris Diaphragm & Abbe Condenser
When buying a compound microscope, always ensure that the
microscope has an iris diaphragm and an Abbe condenser ¨C
which all good quality microscopes will include. Both items
are found in the sub-stage of the microscope and are used in
adjusting the base illumination. All Omano compound
microscopes include iris diaphragms and Abbe condensers, as
b). Mechanical Stage
A mechanical stage is also useful for compound microscopes,
particularly when viewing specimens at high magnifications.
All our full-size, Omano compound microscopes include a
mechanical stage with one exception where it is optional.
VII). SERVICE, SHIPPING & RETURNS
So far, we have summarized the basic variables that go into
buying a microscope. Often overlooked is the quality of
service that you will receive and the shipping and returns
a). Knowledgeable Service
At The Microscope Store, LLC, we believe that buying a
microscope should be fun! It should not be daunting. More
important, a good microscope vendor will have sufficient
knowledge and patience to be able to walk you through the
above, decision-making process. They will be able to guide
you to a microscope that is well-suited to your application.
We pride ourselves on this level of service at The
Microscope Store, LLC. It is central to our success and is
underpinned by a strong sense of traditional business
b). Returns Policy
That said, everyone makes mistakes! For this reason, we
recommend that you only buy a microscope from a vendor with
an adequate Returns policy. As this article indicates, there
are many variables that go into buying a microscope. In some
cases, however helpful the vendor is, the microscope may not
quite work out as anticipated. Most reputable microscope
vendors have a 14-30 day returns policy, during which time
the microscope, (if in it¡¯s original condition and
packaging), can be returned for a full refund. At The
Microscope Store, LLC, we have a 25-day Returns Policy.
c). Shipping Costs
Finally, it is worth checking the vendor¡¯s shipping policy.
Shipping costs can add more than 10% to the cost of a
microscope. At The Microscope Store, LLC, we pledge never to
make a profit from shipping. See full details on the special
Back To Top
MICROSCOPE CARE & MAINTENANCE INSTRUCTIONS
disassemble the microscope as doing so may cause electric
shock or damage to the microscope
the halogen bulbs to cool before touching. Halogen bulbs
become extremely hot and may cause burns if touched
avoid electric shock or damage to the instrument, unplug the
microscope before replacing the bulb.
only the prescribed halogen or fluorescent bulb
off and unplug the microscope before moving.
Carrying the Microscope
lift the microscope with two hands: one hand on the arm, the
other hand supporting the base.
Cleaning the Microscope
should be cleaned off with pressurized air or with a soft
smudges, fingerprints, oils, etc from the lens with clean
lens paper or a soft clean cloth moistened with a small
amount of absolute alcohol-ether mixture. If an
alcohol-ether mixture is unavailable, use isopropyl alcohol
the microscope body and stand using a moist, soft cloth with
a small amount of detergent.
temperatures are: 32¡ã F-104¡ã F (0¡ãC-40¡ãC). Max. relative
water only on plastic surfaces
not use paint thinner or other solvents
a final wipe with a moist soft cloth
all surfaces after cleaning
cover the microscope with the supplied dust cover when not
in a dry place
humid or moist environments, it is advisable to store the
microscope in a waterproof container with a drying agent
not touch the optical lens with bare fingers
not store the microscope in direct sunlight. Sunlight can
influence the quality of the specimen imaging.
Back To Top
Microscope Troubleshooting Tips
|Are you having trouble with your
microscope? Below is a list of common questions we receive
when it comes to microscope maintenance and troubleshooting.
If your question is not listed here, please call us at (877)
409-3556 and a technician will gladly assist you.
1). My microscope will not turn on.
check to see if your microscope is plugged in.
check to see if the bulbs are installed correctly: You may
have to install or reinstall the microscope bulb. Not all
microscopes are shipped with the bulbs already installed. If
the bulbs are installed, check to make sure they aren¡¯t
loose, which sometimes happens during shipment.
you examined all power adjustments? Most microscopes have
rocker switches located on the back, sides and the top to
control whether the microscope receives power or not; also,
most have dials that control the dimness or intensity of the
the fuse in good condition? All microscopes (with cords)
have fuses that can be accessed from the outside of the
microscope. Depending on the your microscope model, you will
either find the fuse on the bottom or back of the
microscope. If the glass case of the fuse appears discolored
or burned, or you can see broken pieces of the fuse element,
this means the fuse is not working. Replacing the fuse will
fix this problem. If your microscope blows its replacement
fuse quickly, please contact one of our microscope
technicians for repair.
2.) I cannot see anything through my microscope.
sure you have removed the protective coverings
you installed the eyepieces? If not, install your eyepieces
(Not sure how? See instructions below)
3.) I cannot install my eyepieces.
you removed the protective covers from the eye ports? If
not, pull out protective covers.
their retaining screws obstructing this installation? If so,
retract with a small slotted screwdriver, such as an
eyeglass screwdriver or penknife. Be careful not to scratch
the finish on the eyepiece tubes.
4.) I cannot view anything through the trinocular port
on my microscope.
a black protective cover obstructing your view? If so,
remove the protective covering.
there a silver pull or lever on the side or front of your
microscope head? If so, either slide the lever back and
forth or pull and push the silver pull. This will transfer
the image from the eye ports to the trinocular port.
you attempting to look through the trinocular port without
an eyepiece? The trinocular port does not contain an optic
for viewing. You may purchase an eyepiece ocular to
facilitate this type of use if necessary. Typically the
trinocular port is used for digital camera attachments that
do not require an eyepiece ocular.
Back To Top
Use a Compound Microscope
familiarize yourself with all the parts of a microscope so
that you can easily move from one part to another during
Moving and Placement: It is worth remembering
that while a good quality microscope will last a lifetime,
it is a sensitive scientific instrument that will suffer
damage from sharp blows or impact. Always, therefore, carry
your microscope in both hands. Grasp the arm with one hand
and place the other hand under the base for support. Always
place the microscope on a level and stable surface.
Slide Preparation: Microscope slides should
always be prepared with a cover slip or cover glass over the
specimen. This will help protect the objective lenses if
they touch the slide. To hold the slide on the stage fasten
it with the stage clips. You can push down on the back end
of the stage clip to open it.
Focusing the Microscope:
1.Start by turning the revolving nosepiece (turret) so that
the lowest power objective lens is "clicked" into position.
The lowest power objective is the shortest one. This
objective is the easiest to focus and center the image in
the field of view.
2.While looking at the objective lens and the stage from the
side, turn the coarse focus knob so that the stage moves
upward toward the objectives. Move it as far as it will go
without touching the slide.
3.Now, look through the eyepiece(s) and adjust the
illuminator and diaphragm until you attain the maximum,
comfortable level of light.
Slowly turn the coarse adjustment so that the stage moves
down (away from the slide). Continue until the image comes
into broad focus. The turn the fine adjustment knob, as
necessary, for perfect focus.
4.Move the microscope slide until the image is in the center
of the field of view. Then readjust the illuminator or
diaphragm in order to attain the clearest image.
5.Once you have attained a clear image, you should be able
to change to a higher power objective lens with only minimal
use of the focusing adjustment. If you cannot focus on your
specimen, repeat the above steps and work from objective to
objective until the higher power objective lens is in place.
1.You should check to see if your microscope has a rack
stop. If it does not have one, then be careful not to allow
the objective lens to touch the slide as you may break the
2.When using a monocular microscope, the correct technique
is to look through the eyepiece with one eye and keep the
other eye open. Most new users, tend to close one eye. While
many microscopists do close one eye, you will help avoid eye
strain by keeping both eyes open.
3.Finally, remember! When you view a specimen through a
microscope, you are viewing an image through multiple
lenses. As a result, the image is upside down and
back-to-front so when you move the slide to the right, the
image goes to the left and vice versa!
Care & Maintenance of Your Microscope
Your microscope will last a lifetime if cared for properly
and we recommend that you observe the following basic steps:
1.When finished viewing , lower the stage, click the low
power lens into position and remove the slide.
2.Switch off the microscope when not using.
3.Avoid touching the glass part of the lenses with your
fingers. Use only special lens paper to clean the lenses.
4.Dust is the number one enemy of a microscope so always
keep your microscope covered when not in use. When not in
use for extended periods, replace the microscope in its box.
Back To Top
Microscope Magnification Specifications
|Field of View or Field Diameter is
very important in microscopy as it is a more meaningful
number than "magnification". Field diameter is simply the
number of millimeters or micrometers you will see in your
whole field of view when looking into the eyepiece lens. It
is just as if you put a ruler under the microscope and
counted the number of lines.
The chart below will tell you (approximately) what to expect
when looking through a microscope with varying combinations
of eyepiece and objective lenses. As an example (in green
below), a dual power stereo microscope with 10X eyepiece
lenses and 1X and 3X combinations of objective lenses, would
have total powers of 10X and 30X and your field of view
would be 20 mm and 6.7 mm respectively.
This means that an object 20 mm (2 cm, or about 3/4 inch)
wide would fill up the whole viewing area at 10X and an
object about 6.7 mm wide would fill up the whole area at
30X. As you can see, having the highest power may not be
best for your particular application. When you move to
greater magnifications, you sacrifice field of view.
Get a metric ruler and place it on the stage of your
microscope. Illuminate from above (if you are using a
compound microscope, get a transparent ruler or illuminate
it with a flashlight). See how many millimeters you can see
from left to right. What would be the field of view of this
image? (answer at bottom of page)
Other considerations: The working distance is the distance
from the bottom of the microscope (lens) to the part of the
specimen that is in focus. As you increase the
magnification, you decrease the working distance. If you
need to work under the microscope, you will need a large
working distance. Some special microscopes have extended
working distances for these purposes. Zoom microscopes have
a fixed working distance throughout the zoom range. When
using a 100X objective lens (1000X total power) your working
distance might only be 0.04mm (40um). The lens will be
extremely close to the specimen! The working distance and
the amount of vertical motion of the microscope will also
affect the maximum specimen height. Maximum Specimen Height
is how tall an object you can put on the stage and still be
able to focus on the top part of the specimen.
Note: The numbers below
will not be the same for all brands of microscopes
microscopes usually have 10X eyepiece lenses so we
only list one column above the 4X objective. If you
wanted to look at an amoeba that is 150um long
(0.15mm) then you would use either the 40X or 100X
objectives.. There are 25 mm in an inch and there
are 1,000 um (micrometers) in a single millimeter.
Back To Top
Microscope Parts and Specifications
|Historians credit the invention of
the compound microscope to the Dutch spectacle maker,
Zacharias Janssen, around the year 1590. The compound
microscope uses lenses and light to enlarge the image and is
also called an optical or light microscope (vs./ an electron
microscope). The simplest optical microscope is the
magnifying glass and is good to about ten times (10X)
magnification. The compound microscope has two systems of
lenses for greater magnification, 1) the ocular, or eyepiece
lens that one looks into and 2) the objective lens, or the
lens closest to the object. Before purchasing or using a
microscope, it is important to know the functions of each
Eyepiece Lens: the lens at the top that you
look through. They are usually 10X or 15X power.
Tube: Connects the eyepiece to the objective
Arm: Supports the tube and connects it to the
Base: The bottom of the microscope, used for
Illuminator: A steady light source (110 volts)
used in place of a mirror. If your microscope has a mirror,
it is used to reflect light from an external light source up
through the bottom of the stage.
Stage: The flat platform where you place your
slides. Stage clips hold the slides in place. If your
microscope has a mechanical stage, you will be able to move
the slide around by turning two knobs. One moves it left and
right, the other moves it up and down.
Revolving Nosepiece or Turret: This is the
part that holds two or more objective lenses and can be
rotated to easily change power.
Objective Lenses: Usually you will find 3 or 4
objective lenses on a microscope. They almost always consist
of 4X, 10X, 40X and 100X powers. When coupled with a 10X
(most common) eyepiece lens, we get total magnifications of
40X (4X times 10X), 100X , 400X and 1000X. To have good
resolution at 1000X, you will need a relatively
sophisticated microscope with an Abbe condenser. The
shortest lens is the lowest power, the longest one is the
lens with the greatest power. Lenses are color coded and if
built to DIN standards are interchangeable between
microscopes. The high power objective lenses are retractable
(i.e. 40XR). This means that if they hit a slide, the end of
the lens will push in (spring loaded) thereby protecting the
lens and the slide. All quality microscopes have achromatic,
parcentered, parfocal lenses.
Rack Stop: This is an adjustment that
determines how close the objective lens can get to the
slide. It is set at the factory and keeps students from
cranking the high power objective lens down into the slide
and breaking things. You would only need to adjust this if
you were using very thin slides and you weren't able to
focus on the specimen at high power. (Tip: If you are using
thin slides and can't focus, rather than adjust the rack
stop, place a clear glass slide under the original slide to
raise it a bit higher)
Condenser Lens: The purpose of the condenser
lens is to focus the light onto the specimen. Condenser
lenses are most useful at the highest powers (400X and
above). Microscopes with in stage condenser lenses render a
sharper image than those with no lens (at 400X). If your
microscope has a maximum power of 400X, you will get the
maximum benefit by using a condenser lenses rated at 0.65 NA
or greater. 0.65 NA condenser lenses may be mounted in the
stage and work quite well. A big advantage to a stage
mounted lens is that there is one less focusing item to deal
with. If you go to 1000X then you should have a focusable
condenser lens with an N.A. of 1.25 or greater. Most 1000X
microscopes use 1.25 Abbe condenser lens systems. The Abbe
condenser lens can be moved up and down. It is set very
close to the slide at 1000X and moved further away at the
Diaphragm or Iris: Many microscopes have a
rotating disk under the stage. This diaphragm has different
sized holes and is used to vary the intensity and size of
the cone of light that is projected upward into the slide.
There is no set rule regarding which setting to use for a
particular power. Rather, the setting is a function of the
transparency of the specimen, the degree of contrast you
desire and the particular objective lens in use.
How to Focus Your Microscope: The proper way
to focus a microscope is to start with the lowest power
objective lens first and while looking from the side, crank
the lens down as close to the specimen as possible without
touching it. Now, look through the eyepiece lens and focus
upward only until the image is sharp. If you can't get it in
focus, repeat the process again. Once the image is sharp
with the low power lens, you should be able to simply click
in the next power lens and do minor adjustments with the
focus knob. If your microscope has a fine focus adjustment,
turning it a bit should be all that's necessary. Continue
with subsequent objective lenses and fine focus each time.
What to look for when purchasing a microscope.
If you want a real microscope that provides sharp crisp
images then stay away from the toy stores and the plastic
instruments that claim to go up to 600X or more. There are
many high quality student grade microscopes on the market
today. They have a metal body and all glass lenses. One of
the most important considerations is to purchase your
instrument from a reputable source. Although a dealer may
give you a great price, they may not be around next year to
help you with a problem. One dealer that we can highly
recommend is Microscope World. They offer a wide variety of
instruments at very competitive prices.
Back To Top
History of the Microscope
|(includes: Who invented the
During the 1st century AD (year 100), glass had been
invented and the Romans were looking through the glass and
testing it. They experimented with different shapes of clear
glass and one of their samples was thick in the middle and
thin on the edges. They discovered that if you held one of
these “lenses?over an object, the object would look larger.
Someone also discovered that you can focus the rays of the
sun with one of these special “glasses?and start a fire.
These early lenses were called magnifiers or burning
glasses. The word lens by the way, is derived from the latin
word lentil, as they were named because they resembled the
shape of a lentil bean (look up lens in a dictionary).
These lenses were not used much until the end of the 13th
century when spectacle makers were producing lenses to be
worn as glasses.
The early simple “microscopes?which were really only
magnifying glasses had one power, usually about 6X - 10X .
One thing that was very common and interesting to look at
was fleas and other tiny insects. These early magnifiers
were hence called “flea glasses?
Sometime about the year 1590, two Dutch spectacle makers,
Zaccharias Janssen and his father Hans started experimenting
with these lenses. They put several lenses in a tube and
made a very important discovery. The object near the end of
the tube appeared to be greatly enlarged, much larger than
any simple magnifying glass could achieve by itself! They
had just invented the compound microscope (which is a
microscope that uses two or more lenses).
Galileo heard of their experiments and started experimenting
on his own. He described the principles of lenses and light
rays and improved both the microscope and telescope. He
added a focusing device to his microscope and of course went
on to explore the heavens with his telescopes.
Anthony Leeuwenhoek of Holland became very interested in
lenses while working with magnifying glasses in a dry goods
store. He used the magnifying glass to count threads in
woven cloth. He became so interested that he learned how to
make lenses. By grinding and polishing, he was able to make
small lenses with great curvatures. These rounder lenses
produced greater magnification, and his microscopes were
able to magnify up to 270X!
Anthony Leeuwenhoek became more involved in science and with
his new improved microscope was able to see things that no
man had ever seen before. He saw bacteria, yeast, blood
cells and many tiny animals swimming about in a drop of
water. From his great contributions, many discoveries and
research papers, Anthony Leeuwenhoek (1632-1723) has since
been called the "Father of Microscopy".
Robert Hooke, an Englishman (who is sometimes called the “English
Father of Microscopy?, also spent much of his life working
with microscopes and improved their design and capabilities.
Little was done to improve the microscope until the middle
of the 19th century when great strides were made and quality
instruments like today’s microscope emerged. Companies in
Germany like Zeiss and an American company founded by
Charles Spencer began producing fine optical instruments.
Today, there are no microscope manufacturers in the US and
most of the microscopes come from Germany, Japan and China.
Toy plastic microscopes should be avoided as they do not
achieved the level of quality of the basic instruments with
metal frames and glass lenses.
Because of foreign production, quality microscopes have
become affordable for all. Zaccharias Janssen, the inventor
of the microscope would marvel at the quality of even the
most basic microscopes found in schools today.
Back To Top
Evaluating a Microscope
|When evaluating microscopes,here are
some items that you might check.
the size of the microscope. Many of the introductory and
elementary student models are 3/4 size or smaller. This is
ok for younger students but children over 13 years old and
adults might prefer a full size instrument. Generally these
smaller microscopes are from 11 to 12 inches tall and the
full size microscopes are 14 inches tall and up.
you do choose a 3/4 size microscope we recommend you select
one with a stationary stage and a moving tube (to focus).
The instruments with the moving stage and fixed tube seem to
have a universal problem with stage drift. In the full sized
varieties, this is not a problem so the moving stage is not
an issue with them. See more on stage drift below.
and workmanship: Basic frame and components should be metal,
although some small parts may be of plastic. Evaluate the
general appearance of all optical and metal surfaces.
the focusing mechanism: The rack and pinion type is the most
reliable and should move smoothly when the focus knobs are
turned. There should be no rough spots. We do not recommend
microscopes with a single "intermediate" focusing knob. If
your microscope goes to 400 or 1000X, it should have both
coarse and fine adjustments.
dovetail in the focusing track (rack and pinion): Look at
the type of metals used to assure that improper materials
will not cause problems later. Check for excessive grease on
rack and pinion focusing mechanism is a very important
component. A round cog-wheel type gear (the pinion, not
shown) engages the rack (teeth, shown) and should offer
smooth motion throughout the focusing range. The dove tail
(shown) is the channel on which the rack runs and should be
focusing, some microscopes have a moving stage, others have
a moving eyepiece tube. If the stage moves when you focus,
check stage drift by pushing down slightly on the stage with
fingers. It should not move. If the stage is stationary and
the eyepiece tube moves, likewise check drift by slightly
pushing down on the eyepiece. On some 3/4 size microscopes
with a moving stage, just moving the slide around on the
stage will push the image out of focus! This is extremely
frustrating when you are trying to move a slide around at
at the alignment of the stage and nosepiece: For example, if
the stage is tilted just a tiny bit, your specimen will
continually be out of focus on one side or the other.
for "backlash" by focusing all the way to the top and bottom
and try to turn the knob further, looking for slight motion.
This tells you how well the rack and pinion gears are
the slip clutch by continuing to turn the focus knob even
after reaching some resistance.
parfocallity: With a slide on the stage, the image should
remain relatively close to focus when changing objective
lenses. Only a slight adjustment should be required to
sharpen the image as objectives are changed.
parcentricity: Start with the lowest power objective and
center your specimen. Move up to successive objective lenses
and the area should remain relatively centered.
for cleanliness: With no slide on the stage, dial in your
highest power objective lens, adjust the diaphragm to the
smallest opening, turn on the illuminator and look through
the eyepiece lens. If you see dust particles, turn the
eyepiece lens. If the dust moves, it is on the eyepiece. If
it doesn't move, it is likely on the internal prisms.
quality of the objective lenses is one of the most important
characteristics of a fine microscope. The better the lenses
(and usually, the more expensive the microscope!), the
sharper the image. In a side by side comparison, you might
be able to notice a difference!
lenses produce crisp, clear images
||Poor quality or
dirty lenses will produce poor, low resolution
Back To Top