Download objective lens

History of the
Microscope
A. Introduction
• 1. A microscope is an optical instrument
that uses a lens or a combination of lenses
to magnify and resolve the fine details of an
object.
The Lens
The Egyptians knew and practiced the art of cutting and polishing stones. From
the Egyptians this art was extended to Greece and Italy.
•Egyptian artifacts include rock crystals in the from of convex lenses (~2600
B.C.E.)
•The Greeks and Romans continued with these types of lenses up to the end of
the Roman Empire (~31 C.E.)
•Knew and practiced the art of glass blowing
•Observed that objects placed in a bulb filled with water appeared magnified
B. History of the Microscope
• 1. During the 1st century AD (year 100),
glass had been invented and the Romans
were looking through the glass and testing it.
2. They experimented with different shapes
of clear glass and one of their samples was
thick in the middle and thin on the edges.
• 3. They discovered that if you held one of
these “lenses” over an object, the object
would look larger.
4. Someone also discovered that you can focus the rays of
the sun with one of these special “glasses” and start a fire.
5. These early lenses were called magnifiers or burning
glasses.
6.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 .
Like much of the history of optics, there are many reports about spectacles, but most put
the invention around 1285.
The grave of Salvano d'Aramento degli Amati a nobleman of Florence has a statement
that he invented spectacles, but kept the process a secret.
Alessandro della Spina of Pisa who died in 1317 had an inscription on his tomb that he
had discovered how to make spectacles (possibly from Amati) and had made the
method known.
Yet another monk, Giordino da Rivalta, who died in 1305 said that making glasses was
one of the most useful arts and that it was only 20 years since its invention. He also said
he knew the inventor (1285).
Why such a long delay between the development of lenses and the invention and use of
spectacles?
One answer is that church doctrine did not allow for man to alter what God had created.
7. These lenses were not used much until the end of
the 13th century when spectacle makers were
producing lenses to be worn as glasses.
8.
The early simple “microscopes” which were really
only magnifying glasses had one power, usually
about 6X - 10X .
9. 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”.
10.
Sometime about the year 1590, two Dutch spectacle
makers, Zaccharias Janssen and his father Hans started
experimenting with these lenses.
11. 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!
12. They had just invented the compound microscope
(which is a microscope that uses two or more lenses).
13.
Galileo heard of their experiments and started
experimenting on his own.
14. He described the principles of lenses and light rays and
improved both the microscope and telescope.
15. He added a focusing device to his microscope and of
course went on to explore the heavens with his telescopes.
16321723
my work, which I've done for a long time, was not pursued in order to gain the
praise I now enjoy, but chiefly from a craving after knowledge, which I notice
resides in me more than in most other men. And therewithal, whenever I found out
anything remarkable, I have thought it my duty to put down my discovery on
paper, so that all ingenious people might be informed thereof.
Antony van Leeuwenhoek. Letter of June 12, 1716
16. 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.
17. He became so interested that he learned how
to make lenses.
18. 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!
19. 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.
20. 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“, though he did not
invent the microscope
He took samples between his teeth
and other people. Named these
“things” he saw
Animacules
21. 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.
C. The Compound Microscope
• 1. In the basic compound microscope, the object
to be magnified is placed under the lower lens
(objective lens) and the magnified image is viewed
through the upper lens (eyepiece lens).
• 2. The magnification of the image can be
calculated by multiplying the magnifying power of
the objective lens times the magnifying power of
the eyepiece lens.
• 3. The microscope is composed of a mechanical
system which supports the microscope, and an
optical system which illuminates the object under
investigation and passes light through a series of
lens to form an image of the specimen.
The principle of the compound microscope. The passage of light through
two lenses forms the virtual image of the object seen by the eye.
Eyepiece
Objective
Lens
Magnificati
on
Low Power
10 x
4x
40 x
Green = GO!
Green = GO!
Green = GO!
Green = GO!
Medium
Power
10 x
10 x
100 x
Yellow = Caution
Yellow = Caution
Yellow = Caution
Yellow = Caution
High Power
10 x
40 x
4000 x
Red = STOP!
Never Use This
Lens!
Focus: finefocus knob
only
Body tube
Revolving Nosepiece
ocular
eyepiece
arm
Objective lens
Stage
Stage clips
Diaphragm
Light
Coarse adjustment knob
Fine adjustment knob
base
1. Don’t even think of starting your drawing unless
you have a PENCIL! Drawings in PEN are UNACCEPTABLE!
This is for two reasons:
(a) You can erase pencil!
(b) You can shade in areas more easily in pencil.
2. Each Drawing must be 1/2 page in size, and
must include clear, proper labels! In the upper left hand
corner of each circle include the specimen name as written
on the slide label. In the upper right hand corner, include
the magnification (100x or 430x).
How To Make A Wet Mount:
1. Gather a thin slice/piece of whatever your specimen is. If
your specimen is too thick, then the coverslip will wobble on
top of the sample like a see-saw:
2. Place ONE drop of water directly over the
specimen. If you put too much water over the specimen,
then the coverslip will float on top of the water, making it
harder to draw the specimens as they float past the field of
view!
3. Place the coverslip at a 45 degree angle (approximately),
with one edge touching the water drop, and let go.