Light microscopes relies on glass lenses and visible light to magnify tissue samples. It was invented in XVII century, and has been improved over the years, resulting in the powerful modern light microscopes. As individual cellular structures are too small to be seen by the human eye, microscopy techniques have played a key role in the development of histological techniques.

1. Types of light Microscopes used in Histological Studies
Supervised by
Assisstant Professor Dr. Enas Fadhil
Prepared by
Oday Hatem Mohammed

2. TABLE OF CONTENTS
The simple microscope
Principles
Types of
microscopy
Introduction
05
Definition of
Microscope
Parts of light
microscope
01
03 04
02

3. INTRODUCTION
Histology is the microscopic study of cells and tissues and plays a central role in disease
diagnosis. Through the identification of characteristic features in tissue structures, it is
possible to diagnose diseases by comparing changes in the cellular structure between
healthy and diseased tissues. Light , or optical, microscopes are essential for histological
studies because they allow us to visualize cells and morphological features of tissues.

4. INTRODUCTION
Light microscopes relies on glass lenses and visible light to magnify tissue samples. It was
invented in XVII century, and has been improved over the years, resulting in the powerful
modern light microscopes. As individual cellular structures are too small to be seen by the
human eye, microscopy techniques have played a key role in the development of
histological techniques.

5. 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

6. Definition of Microscope
Instrument that produces enlarged images of small objects, allowing the observer an
exceedingly close view of minute structures at a scale convenient for examination and
analysis. As advances in optics have made it possible to perform microscopy with a wider
range of imaging techniques and improved spatial resolution, many of these techniques
have been adopted as a routine part of histological investigations.

7. The simple microscope Principles
Light microscope is also called an optical microscope. There are two types of light
microscope, simple microscope has one lens with low magnification and the compound
microscope has two lenses (objective and eye piece) with higher magnification.

8. 1. Ocular/Eyepiece is present towards the
viewer. It converts the real image of object into
virtual image. It may be a combination of more
than two lenses.
2. Lens tube is of about 160 mm length and
holds the eyepiece.
3. Objective lens is present towards the object.
It assembles the light reflected from the object at
a place and produces a real image of object.
Parts of light microscope

9. 4. Objective revolver consists of objective lenses of
different magnifying power.
5. Stand is attached with all components of
microscope and it keeps them together.
6. Clip holds the object in place.
7. Stage is the place where object is kept for
observing.
8. Condenser focuses the rays of sunlight on the
object.
Parts of light microscope

10. 9. Fine and coarse adjustments control the
distance between object and objective lens. They are
used to produce sharp image of object.
10. Luminous-field diaphragm controls the
diameter of light coming from light source.
11. Light source is the LED bulb used to
illuminate the object. The older microscopes
used concave mirror to focus the sunlight on the
object to make it visible.
12. Base supports the microscope.
Parts of light microscope

11. Types of microscopy
Many types of microscopes are used for the study of tissues. The most common is the bright-
field microscope, which is a complex optical instrument that uses visible light. Modifications
of this instrument have provided the phase contrast, interference, dark field, and polarizing
microscopes. The optical systems that utilize invisible radiations include the ultraviolet
microscope, X-ray, and electron microscope. Each of these instruments has been a valuable
tool in the study of oral tissues.

12. Bright field light microscope
This is the most basic optical Microscope used
in microbiology laboratories which produces
a dark image against a bright background.
Made up of two lenses. Its functionality is
based on being able to provide a high-
resolution image, which highly depends on
the proper use of the microscope.

13. Bright field light microscope
This means that an adequate amount of
light will enable sufficient focusing of the
image, to produce a quality image. It is also
known as a compound light microscope.

14. DARK FIELD MICROSCOPY
This is a specialized type of bright field light microscope that
has several similarities to the Phase-Contrast Microscope.
This technique is used to visualize living unstained cells. This
is affected by the way illumination is done on the specimen.

15. DARK FIELD MICROSCOPY
Light passes through the objectives to the specimen forming
an image. This makes the surrounding field of the specimen
appear black while the specimen will appear illuminated.
This is enabled by the dark background this the name, dark-
field Microscopy.

16. FLUORESCENCE MICROSCOPY
In the fluorescent Microscope, the specimen emits light. How? By
adding a dye molecule to the specimen. This dye molecule will
normally become excited when it absorbs light energy, hence it
releases any trapped energy as light. The light energy that is
released by the excited molecule has a long wavelength compared
to its radiating light.

17. FLUORESCENCE MICROSCOPY
The dye molecule is normally a fluorochrome, that fluoresces
when exposed to the light of a certain specific wavelength. The
image formed is a fluorochrome-labeled image from the emitted
light.

18. PHASE CONTRAST MICROSCOPY
This is a type of optical microscope whereby small light deviations
known as phase shifts occur during light penetration into the
unstained specimen. These phase shifts are converted into the
image to mean, when light passes through the opaque specimen,
the phase shifts brighten the specimen forming an illuminated
(bright) image in the background. The phase-contrast microscope
produces high contrast images when using a transparent specimen.

19. PHASE CONTRAST MICROSCOPY
The PCM can be used to view unstained cells, which means that
the morphology of the cell is maintained and the cells can be
observed in their natural state, in high contrast and efficient
clarity. This is because if the specimens are stained and fixed, they
kill most cells, a characteristic that is uniquely undone by the
brightfield light microscope.

20. DIFFERENTIAL INTERFERENCE CONTRAST MICROSCOPY
DIC works by separating a polarized light source into two
orthogonally polarized beams. The light beams are split and then
recombined. This optical path difference in each of the two light
beams caused by differences in thickness and refractive index of
the specimen cause them to interfere when combined.

21. DIFFERENTIAL INTERFERENCE CONTRAST MICROSCOPY
This produces contrast and makes the cell appear three
dimensional as if lit form the side. Using DIC there are no halos
around organelles so the resolution is maximized and the
technique permits observation of thin optical sections.

22. CONFOCAL MICROSCOPY
Confocal microscopy provides a means of rejecting the out-of-
focus light from the detector such that it does not contribute blur
to the images being collected. This technique allows for high-
resolution imaging in thick tissues. In a confocal microscope, the
illumination and detection optics are focused on the same
diffraction-limited spot in the sample, which is the only spot
imaged by the detector during a confocal scan.

23. CONFOCAL MICROSCOPY
To generate a complete image, the spot must be moved over the
sample and data collected point by point. A significant advantage
of the confocal microscope is the optical sectioning provided,
which allows for 3D reconstruction of a sample from high-
resolution stacks of images.

24. POLARIZED MICROSCOPY
A polarizing microscope can also produce contrast provided the
specimens or cellular components are birefringent (doubly
refracting). The addition of linear polarizing filters to a bright field
microscope is inexpensive.

25. POLARIZED MICROSCOPY
The use of a compensator or wave plate filter can also introduce
colors to the subject and background and a polarizing microscope
can determine refractive index of mineral or biological specimens if
the specimen thickness is known.

26. Volvox, a green algae living in fresh water ponds viewed by different kinds of microscope
illumination a) bright-field b) dark-field c) phase contrast d) differential Interference contrast e)
Rheinberg lighting f) fluorescence microscopy with green excitation.

27. Smartphone-based imaging devices (SIDs)
Smartphone-based imaging devices (SIDs) are platforms that
utilize the imaging capability of a smartphone and is used for
applications other than conventional photography. They have
shown to be utilized as microscopic devices, analytical detection
and sensing devices, devices to monitor pollution and
contaminants, as well as devices for educational purposes. SIDs are
advantageous over the conventional optical microscope in areas
with limited manpower and where the requirement of rapid
diagnosis is high.

28. Smartphone-based imaging devices (SIDs)
SIDs are portable with either add-on attachment or modification
of the built-in camera setup for advanced imaging. Other benefits
could be diagnosis confirmation, sharing of knowledge, and rapid
data sharing for faster analysis. This makes the whole diagnostic
system affordable and helps in reaching out to a larger section of
the society.