EXERCISE NO. 1 THE COMPOUND MICROSCOPE Flashcards
The term ‘microscope’ was from the Ancient Greek [?], “small”, and [?], “to look” or “see”.
- mikrós
- skopeîn
are instruments designed to produce magnified visual or photographic images of small objects.
Microscopes
The microscope is an essential equipment in parasitology laboratory. While some parasites, such as the adult worms of [?], can be seen by the unaided eye, a microscope is necessary to make it possible to view their products such as eggs and/or larvae. and other parasites which are too small to be seen by the naked eye.
Ascaris lumbricoides, or Taenia species
There are many types of microscopes, and they may be grouped in different ways. Routine microscopic work in a parasitology laboratory is done using a [?]. It uses visible light to illuminate the specimen, and passes that light through two separate lens to magnify the image.
light compound microscope
When carrying the microscope, hold both sides around the
hole of the arm (Fig.1.1). Under no circumstances should one
attempt to carry two microscopes at one time. To prevent
damage, do not hold the microscope by the [?]
stage (1) orobservation tube (2).
Don’t let the [?] of the microscope dangle in such
a way as to hazard foot entanglement.
electric cord
Place the microscope in a [?]. Keep the workstation uncluttered.
stable flat surface
Microscope with rotatable observation tube may be used in two ways: with microscope arm near the observer or away from the observer. To change from one position to another, hold the [?] firmly with one hand while loosening the observation tube adjustment clamp and rotating the observation tube with the other hand to prevent it from accidentally falling off from the microscope and causing damage to the ocular lenses. Don’t forget to tighten the clamp .
observation tube
check the [?] to make sure they are clean.
lenses
• Rotate the [?] into position.
lowest-power objective
• Remove the [?] from the stage.
slide
• Clean the microscope surfaces free of dust or debris. If immersion oil has been used, wipe it off the [?] with lens tissue.
lens and stage
• Coil the [?] around the base of the microscope.
power cord
• Replace the [?] and/or return the microscope to to its correct place in the cabinet.
dust cover
• Replace the [?] and/or return the microscope to to its correct place in the cabinet.
dust cover
The microscope consists of different parts and can be
classified into four systems:
the support system
the magnification system
the illumination system
the adjustment system
the overall support
Base or foot
supports the observation tube
Arm or limb
objective changer
Revolving nosepiece
holds the slide specimen in place
Stage
This consist of a system of lenses.
MAGNIFICATION SYSTEM
The lenses of the microscope are mounted in two groups, one at each end of the
long tube - body tube.
The first group of lenses is at the bottom of the tube, just
above the object and is called the
objective
The second group of lenses is at the top of the tube and is
called the
eyepiece or ocular
The second group of lenses is at the top of the tube and is
called the
eyepiece or ocular
A microscope may be monocular or binocular.
A monocular has only 1 eyepiece for viewing objects.
A [?], which has 2 eyepieces, is used in most clinical laboratories because both eyes are used to view an object, thus reduces eyestrain.
binocular microscope
refers to the ability of an optical system to enlarge an image of a specimen. This is expressed as magnifying power - the number of times the image of an object is enlarged.
Magnification
is shown by a figure engraved on the sleeve of the lens (Fig. 1.4). The figures ranges from 4x up to 100x.
The magnifying power of each objective
magnifies 4 times.
magnifies 10 times.
magnifies 40 times.
magnifies 100 times.
- 4x (scanning) objective
- 10x (low-power, LPO) objective
- The 40x (high-power, , HPO) objective
- The 100x (oil-immersion) objective
are called dry objectives because they are designed to operate with air as the imaging medium between the cover glass and the objective front lens.
The 4x-, 10x-, and 40x- objectives
is called the oil immersion objective (OIO) because the tip of the OIO lens is immersed in oil.
The 100x objective
The magnifying power ranges from 10x up to 20x (Fig. 1.5)
Eyepiece (or ocular)
magnifies the image produced by the objective 10 times
a 10x eyepiece
magnifies the image 20 times.
a 20x eyepiece
built into the microscope beneath the stage. This is turned on by a main switch found near the base of the microscope or arm of the microscope.
An electric bulb
The light source can be a
halogen lamp or a light emitting diode (LED)
Microscopes that do not have built-in light bulb have a [?] that reflects rays from the sunlight or external lamp onto the object.
mirror
One side has a plane surface, the other a concave surface. The [?] side forms a low-power condenser and is not intended to be used of the microscope already has a condenser
concave
This is located between the mirror and the stage. It brings the rays of light to a common focus on the object to be examined.
Condenser
This is located between the mirror and the stage. It brings the rays of light to a common focus on the object to be examined.
Condenser
it can be raised to provide maximum illumination, and lowered to provide minimum illumination. It must be centered and adjusted correctly.
condenser
This is a series of thin plates found inside the condenser.
Iris diaphragm
Iris diaphragm has a [?] which can be controlled to open or close to increase or reduce, respectively the angle and therefore the amount of light that passes into the condenser.
central aperture
It is fitted below the condenser. It allows the passage of light of desired wavelength only.
Filter
is used to balance the light created by tungsten or halogen microscope lights.
Daylight blue filter
Because [?] can be designed to generate the desired visible light colors, there’s no need to use the traditional colored filters.
LEDs
This consist of: • mechanical stage control knobs (1) • observation tube adjustment clamp (2) • focus adjustment knobs: - coarse adjustment knob (3) - fine adjustment knob (4) • condenser adjustment screw (5) • iris diaphragm ring (6) • light intensity adjustment knob (7) • interpupillary distance adjustment (8) • diopter adjustment ring (9)
ADJUSTMENT SYSTEM
These are used to move the object slide on the stage.
Mechanical stage control knobs
This enables the observation tube of the microscope to rotate.
Observation tube adjustment clamp.
moves the specimen in a horizontal direction (left or right)
x-axis knob
moves the specimen in a vertical direction (backwards and forwards).
y-axis knob
This enables the observation tube of the microscope to rotate.
Observation tube adjustment clamp
This is the largest screw. It is used first to achieve an approximate focus. It is rotated to bring the specimen as close as possible to the objective.
Coarse adjustment knob
This moves the objective more slowly. It is used to bring the object into perfect/precise focus.
Fine adjustment knob
This is used to raise the condenser for greater illumination or to lower it to reduce the illumination.
Condenser adjustment screw
This can be moved to close or open the diaphragm, thus reducing or increasing both the angle and the intensity of the light.
Iris diaphragm ring
This controls the mechanism for preventing collision between the specimen and the objective
Pre-focusing knob
This regulates the eyepieces according to the distance between your eyes so that you observe a single image through the eyepieces.
Interpupillary distance adjustment
This compensates for the difference in the eyesight between the 2 eyes. to make diopter adjustments, one focuses first with the right eye.
Diopter adjustment ring
Additional features found in binocular microscope
Interpupillary distance adjustment
Diopter adjustment ring
The microscope must accomplish three tasks:
- produce a magnified image of the specimen
- separate the details in the image
- render the details visible to the human eye or camera.
So, other than magnification, properties of a good microscope are
resolution and contrast
The image of an object can be magnified when viewed through a
lens
is a function of the interaction between the visible light rays and the curvature of bi-convex lens, one that is thicker at the center than at the periphery
Magnification
When parallel rays of light pass through a biconvex lens, light rays are refracted (bent) and converge at one point called the
focal point
The vertical plane in which the focal point lies is the
focal plane.
The distance from the center of the bi-convex lens to the focal plane is known as the [?] (or focal length).
focal distance
The distance between the front principal plane of the lens and the object is known as the
object distance
The distance between the front principal plane of the lens and the object is known as the
object distance
In a similar manner, the distance from the rear principal plane to the image is termed the
image distance.
These parameters are the fundamental elements defining the geometrical optics of a simple lens and can be used to calculate important properties of the lens, including
focal length and magnification factor
When object is situated two focal lengths in front of the lens, the image is also [?] behind the lens.
two focal lengths
The lens is performing , i.e., the image size is the same as the object size.
1:1 magnification
For a magnified image to be observed, the object distance must be [?] than the focal length of the lens
shorter
In general, images are defined by the regions where and how they are
observed or perceived.
is an image which is located in the plane of convergence for the light rays (back focal plane) that originate from a given object.
real image
If a screen is placed in the plane of a real image, the image will generally become visible on the screen and appears [?] (reversed and upside-down). An example of real image is the image seen on a cinema screen (the source being the projector).
inverted
is perceived on the same side of the lens as the object; is produced on the same side of the lens as the object, such as the image produced by a simple magnifying lens. It is formed on the retina of the eye , therefore cannot be projected on a screen.
virtual image
virtual images always appear [?] to the observer.
upright
Parasitologic work uses [?] which is best for observing stained specimens and living organisms. Now we will describe how a brightfield microscope works in somewhat more detail.
brightfield microscope
passes the substage condenser, which forms a well-defined light cone that is concentrated onto the object.
Light from illuminator
Light is transmitted through the specimen and into the objective which then projects a primary enlarged image, called [?], to a fixed plane within the body tube.
intermediate image
The intermediate image becomes the “object” for the eyepiece to produce a secondarily enlarged image, called the[?].
final image
When the human eye is placed above the eyepiece, the lens and cornea of the eye “look” at the [?] as if it were 10 inches from the eye, near the base of the microscope.
final image
of the microscope is derived by multiplying the magnification values of the objective and the eyepiece. For instance, using a 10X objective with a 10X eyepiece yields a total magnification of 100X and likewise.
Total magnification
is the ability of the optical system to separate two closely adjacent objects into 2 distinct entities. Simply, this is the property of the microscope that determines
microscopic image clarity and richness of detail. One using a microscope would not want to observe magnified images of small objects only but also clear images, not blurry or fuzzy.
Resolution
is the ability of the optical system to separate two closely adjacent objects into 2 distinct entities. Simply, this is the property of the microscope that determines
microscopic image clarity and richness of detail. One using a microscope would not want to observe magnified images of small objects only but also clear images, not blurry or fuzzy.
Resolution
Increased magnification is useless without improved
resolution
