S Back to top Stage, The stage is the platform that supports the specimen. It is usually quite large to minimize vibration and it attaches to the microscope stand. The stage has an opening for the illuminating beam of light to pass through.   A spring loaded clip holds the specimen slide in place on the stage. Other types of stage clips are designed for use with petri-dishes, multiwell plates, or other specialized chambers.   Most stages have a rack and pinion mechanism that can move the specimen slide in two perpendicular (X - Y) directions. On many microscopes, stage movement is controlled using two concentric knobs located to the side or below the stage.   Stand, The stand is the basic structure of the microscope to which everything is attached. The stand, also known as the arm, is the part of the microscope that you grab to transport the microscope.

Base function in microscopediagram

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M Back to top Magnification, The degree to which the image of the specimen is enlarged by the objective. For example, 40 specifies 40 times (40x) the actual size of the specimen. As magnification increases, resolution (NA) must also increase so that more information can be obtained. Magnification without increased resolution yields no additional information and is called "empty magnification."

P Back to top   Plan, There are many different kinds of objective lenses. Common designations include "plan" for flat field, "achromat" for partially color-corrected, and "apochromat" for highly color corrected. These designations may become combined as in "plan achromat."

Such cornea can be described like a rugby ball also (Fig5). Like the doughnut example, here again both meridians are curved, but one meridian is more curved than the other. Since both sides have power, they will be called power meridians, or Principal Meridians.

Functionof nosepiecein microscope

Now let us consider, you have both astigmatism as well as myopia (or hyperopia) found by your doctor. How will your cornea look like ? It would look like a doughnut ( see Fig 4 ).

Unlike the cylinder, a doughnut would not have any flat surface. All surfaces will be curved. However, there will be one surface more curved than the other. In Fig4 you can see the tube representing the cornea has one axis more curved than the other axis. Or in other words, in the Fig4, the y-axis or 90 degree is significantly more curved than the x-axis (180 degree).

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-1-2@90, whereby -1 denotes myopia the patient is having, the -2 denotes the difference in principal meridians (astigmatism), and the axis 90 degree is where you are placing the spherical power in glass as -1 to correct for the difference in power of the two principal meridians. In the world of physicians and optometrists, this is also referred to as an optical cross.

Microscopeparts and functions pdf

So, transposing -1-2@90 would be -3+2@180. To do transposition, add the spherical and the cylinder, then change the sign before the cylinder , keep the magnitude of astigmatism unchanged, and change the axis by 90 deg.

Astigmatism here is the difference between the two principal meridians. That is 46.50 - 44.50 = 2 dioptres. Thus we can represent this as +2.0 at 180 degree. We can say here that the 180 degree is steeper than an average cornea of 43.50 dioptres by +3 dioptres, and 90 degree is steeper by +1 dioptre. Thus both meridians are steeper than normal conea, and rays of light passing through both the meridians of 90 and 180 degree are falling before the retina. The patient's cornea is having a compound myopic astigmatism, that is both meridians have stronger power on the cornea than average cornea. To correct this, we need to give a equally rughby shaped glass, but have to place the same power in opposite meridians to negate the difference in corneal power. Thus since the patient has +3 at 180 degee and +1 at 90 degree on cornea, we will have to negate it with a -3@180 degree and -1 at 90 degree on the glass,

F Back to top Focus (coarse), The coarse focus knob is used to bring the specimen into approximate or near focus.   Focus (fine), Use the fine focus knob to sharpen the focus quality of the image after it has been brought into focus with the coarse focus knob.

O Back to top Objective Lens, The objective lens is the single most important component of the microscope. Together with the condenser, it determines the resolution that the microscope's capability. Learning how to use the correct objective for a particular application is a prerequisite for good microscopy.   Important information describing the objective lens is engraved on the side of its barrel. This is the best performance the objective is capable of and it will only yield this performance when used properly. Ocular Lenses, The ocular lenses are the lens closest to the eye and usually have a 10x magnification. Since light microscopes use binocular lenses there is a lens for each eye. It is important to adjust the distance between the microscope oculars, so that it matches your interpupillary distance. This will yield better image quality and reduce eye strain.

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A cylinder, in optics, and as depicted in figure 1 has one side curved, and the other side flat. The side which is flat (y axis in fig1) has no power and is called axis. In the fig1 the axis or the meridian of no power is at 90 degree. The side which has power is called power meridian, that is 180 degree in the picture (x axis in fig1). Here the horizontal side has power and the vertical side is the Axis, or a place of no power. The difference between the Principal Meridians (power meridian) and the axis (no power) is astigmatism/cylinder.

When the turret is rotated, it should be grasped by the ring around its edge, and not by the objectives. Using the objectives as handles can de-center and possibly damage them.

Microscopeparts and functions

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To state in terms of corneal example, both axis of cornea (90 degree and 180 degree) have power which is either more or less than average power of cornea. In our last example, remember the patient had more power than average cornea (46.50 dioptres) at 180 degree. But in the other meridian that was 90 degree away, the patient had normal power ( 43.50 dioptre). In this example however, the patient will have more power or less power than 43.50 dioptre in both the vertical and horizontal meridians. Say in this case the patient has 44.50 dioptre @ 90 degree. So the patient has 46.50@180 and 44.50@90, and therefore in both the meridians the patient has more power than average and normal cornea.

Such a patient will have a subjective refraction typically like this, that is the optometrist will check his eye and see that he may be accepting a glass power of -1 -2 @90

To be more scientific, and talking in corneal terms, we understand the average power of the cornea is around 43.50 dioptres. What this means in the context of the above described figure is that one meridian will have just the right power (average power/43.50 diopter), while the other meridian which is 90 degree away will have either more or less power than 43.50 dioptres. For example, in the context of Fig 1, the patient's cornea will have 43.50 dioptres on the y axis (90 degree), but has more power (say 46.50 dioptres) at the x axis (180 degrees). The rays of light that pass through the 90 degree will therefore fall on the retina, while the rays of light that pass through 180 degree will fall before the retina as because the cornea is too steep at the horizontal axis.

Since we started by describing that we will talk about astigmatism in corneal terms, let us assume that the patient's corneal reading ( Keratometry ) is +2 at 90 degree. That is the patient' 90 degree (y axis) has more power than the 180 degree, which is often labelled as with-the-rule astigmatism. How will we correct this corneal astigmatism with glass?

Objective lensmicroscope function

Microscope Anatomy & Function Glossary Back to Quicktime VR Microscope   A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z   A Back to top   B Back to top Base, The base is the foundation on which the microscope stand is built. It is important that the base is relatively large, stable, and massive. When you are setting up a microscope for the first time ensure that the surface on which it is placed is level.     C Back to top Condenser, The condenser under the stage focuses the light on the specimen, adjusts the amount of light on the specimen, and shapes the cone of light entering the objective. One way to think about the condenser is as a light "pump" that concentrates light onto the specimen.   The condenser has an iris diaphragm that controls the angle of the beam of light focused onto the specimen. The iris diaphram is an adjustable shutter which allows you to adjust the amount of light passing through the condenser. The angle determines the Numerical Aperture (NA) of the condenser. This diaphragm, generally called the aperture diaphragm, is one of the most important controls on the microscope.   Cover slip, Most objectives are designed for use with a cover slip between the objective and the specimen. The cover slip becomes part of the optical system, and its thickness is critical for optimal perfomance of the objective. The cover slip thickness designation on most objective lenses is 0.17 mm or 170 microns. D Back to top   E Back to top   F Back to top Focus (coarse), The coarse focus knob is used to bring the specimen into approximate or near focus.   Focus (fine), Use the fine focus knob to sharpen the focus quality of the image after it has been brought into focus with the coarse focus knob.   G Back to top   H Back to top   I Back to top Illuminator, There is an illuminator built into the base of most microscopes. The purpose of the illuminator is to provide even, high intensity light at the place of the field aperture, so that light can travel through the condensor to the specimen.   J Back to top   K Back to top   L Back to top   M Back to top Magnification, The degree to which the image of the specimen is enlarged by the objective. For example, 40 specifies 40 times (40x) the actual size of the specimen. As magnification increases, resolution (NA) must also increase so that more information can be obtained. Magnification without increased resolution yields no additional information and is called "empty magnification."   N Back to top Numerical Aperture (NA), The maximum angle from which it can accept light. Lenses that accept light from higher angles have greater resolving power, thus NA defines resolving power. The maximum NA of objectives is 1.4, and it is limited by the physics of light and the refractive index of glass.   O Back to top Objective Lens, The objective lens is the single most important component of the microscope. Together with the condenser, it determines the resolution that the microscope's capability. Learning how to use the correct objective for a particular application is a prerequisite for good microscopy.   Important information describing the objective lens is engraved on the side of its barrel. This is the best performance the objective is capable of and it will only yield this performance when used properly. Ocular Lenses, The ocular lenses are the lens closest to the eye and usually have a 10x magnification. Since light microscopes use binocular lenses there is a lens for each eye. It is important to adjust the distance between the microscope oculars, so that it matches your interpupillary distance. This will yield better image quality and reduce eye strain.   P Back to top   Plan, There are many different kinds of objective lenses. Common designations include "plan" for flat field, "achromat" for partially color-corrected, and "apochromat" for highly color corrected. These designations may become combined as in "plan achromat." Parfocal, The specimen is focused for all objectives if it is focused for one objective. In other words, once the specimen is focused under one objective it will be in approximate focus under other objectives. Q Back to top   R Back to top   S Back to top Stage, The stage is the platform that supports the specimen. It is usually quite large to minimize vibration and it attaches to the microscope stand. The stage has an opening for the illuminating beam of light to pass through.   A spring loaded clip holds the specimen slide in place on the stage. Other types of stage clips are designed for use with petri-dishes, multiwell plates, or other specialized chambers.   Most stages have a rack and pinion mechanism that can move the specimen slide in two perpendicular (X - Y) directions. On many microscopes, stage movement is controlled using two concentric knobs located to the side or below the stage.   Stand, The stand is the basic structure of the microscope to which everything is attached. The stand, also known as the arm, is the part of the microscope that you grab to transport the microscope.   T Back to top Tube, the tube houses many of the optical components of the microscope. The optical tube length of most biomedical microscopes is 160 millimeters but tube geometry varies considerably due to relay lenses and proprietary design features. In most modern microscopes the tube is folded to make the microscope easier to use.   Early microscopes had straight tubes such as this model built by Robert Hooke in the mid 17th century. Tube length, describes the optical tube length for which the objective was designed. This is 160 mm (6.3 inches) for modern biomedical microscopes.   Turret, Most microscopes have several objective lenses mounted on a rotating turret to facilitate changing lenses. An audible click identifies the correct position for each lens as it swings into place. When the turret is rotated, it should be grasped by the ring around its edge, and not by the objectives. Using the objectives as handles can de-center and possibly damage them. U Back to top   V Back to top   W Back to top   X Back to top   Y Back to top   Z Back to top   Back to Quicktime VR Microscope

If you do a transposition then you get the second principal meridian. The concept of transposition is described in Eye & Astigmatism series in this site Video section. In transposition you add the spherical and cylinder powers as a first step to get the power of the other principal meridian.

How to correct ? A glass given to you would have a cylinder shape, but would be placed in the opposite meridian (Fig2). So here the glass cylinder will be aligned horizontally, that is the flat axis of the glass will be aligned on the x axis or 180 deg meridian ( Fig3 ). Thus the power meridian aligned to 90 deg of the prescription cylinder ( depicted in yellow colour in Fig2 and Fig3) , will negate the corneal Power meridian at 180 deg ( depicted in grey cylinder in Fig1). The result, you have is a spherical refraction depicted in green (Fig3).

N Back to top Numerical Aperture (NA), The maximum angle from which it can accept light. Lenses that accept light from higher angles have greater resolving power, thus NA defines resolving power. The maximum NA of objectives is 1.4, and it is limited by the physics of light and the refractive index of glass.

Thus, the concept of correction of astigmatism with myopia (or hyperopia) is the same as that of the patient with astigmatism only (in the first example). The patient with a difference between two principal meridians ( astigmatism ) will have to be given a similar difference of two meridian power in the glass, albeit, on the opposite meridians/directions. Such lenses, whether glass or an IOL ( if a cataract patient ) are also called sphero- cylindrical lenses. The TORIC IOLs of different surgical companies implanted intraoperatively, is a sphero-cylindrical lens where you have a difference of power in the two opposite meridian.

Functionof eyepiecein microscope

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In this article, I will explain astigmatism and how it is corrected with glasses. To further reference you can also see my video explanations in the TORIC section (https://www.quickguide.org/post/eye-astigmatism-part-1) .To explain in a lucid way, we will talk in terms of corneal astigmatism or cylinder, and its correction with prescription glasses.

Imagine you visit your doctor and he/she finds out that you have only astigmatism with no myopia or hypermetropia. In this case you have an average power in one meridian and in other meridian (which is 90 degree away) you have rays of light falling away from the retina. This is subjective refraction, the sum total of the corneal and lenticular refractions (total eye refraction). It shows that you have astigmatism, that is in one meridian you have more (or less) power, while the meridian which is 90 degree away has just the right power. To keep matters simple, let us keep the human crystalline lens (HCL) away, and assume that the astigmatism is solely due to cornea. So with one meridian of cornea more (or less power) than average, while the other meridian which is 90 degree away having a normal power, will make the refraction of your cornea a cylinder in shape (Fig1)

Functionof armin microscope

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Parfocal, The specimen is focused for all objectives if it is focused for one objective. In other words, once the specimen is focused under one objective it will be in approximate focus under other objectives.

B Back to top Base, The base is the foundation on which the microscope stand is built. It is important that the base is relatively large, stable, and massive. When you are setting up a microscope for the first time ensure that the surface on which it is placed is level.

Base function in microscopelabeled

The condenser has an iris diaphragm that controls the angle of the beam of light focused onto the specimen. The iris diaphram is an adjustable shutter which allows you to adjust the amount of light passing through the condenser. The angle determines the Numerical Aperture (NA) of the condenser. This diaphragm, generally called the aperture diaphragm, is one of the most important controls on the microscope.   Cover slip, Most objectives are designed for use with a cover slip between the objective and the specimen. The cover slip becomes part of the optical system, and its thickness is critical for optimal perfomance of the objective. The cover slip thickness designation on most objective lenses is 0.17 mm or 170 microns.

C Back to top Condenser, The condenser under the stage focuses the light on the specimen, adjusts the amount of light on the specimen, and shapes the cone of light entering the objective. One way to think about the condenser is as a light "pump" that concentrates light onto the specimen.

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Going by our previous example in corneal terms, such a patient would be given a prescription/subjective refraction written like this : +3.50@180( power meridian of 3.5 D will be then aligned to 90 degree, that is to the flat meridian of cornea) to negate the +3.50 diotres of more power the patient has in cornea at 180 degree ( 46.50@180 and 43.50@90 on cornea).

Therefore the two spherical powers are -1 and -3 diopters in the glass. The patient's glass will have -1 at 90 degree while -3 will be at 180 degree. Thus the difference of 2 dioptres in glass power will negate the +2 of astigmatism at the corneal plane.

T Back to top Tube, the tube houses many of the optical components of the microscope. The optical tube length of most biomedical microscopes is 160 millimeters but tube geometry varies considerably due to relay lenses and proprietary design features. In most modern microscopes the tube is folded to make the microscope easier to use.   Early microscopes had straight tubes such as this model built by Robert Hooke in the mid 17th century. Tube length, describes the optical tube length for which the objective was designed. This is 160 mm (6.3 inches) for modern biomedical microscopes.   Turret, Most microscopes have several objective lenses mounted on a rotating turret to facilitate changing lenses. An audible click identifies the correct position for each lens as it swings into place. When the turret is rotated, it should be grasped by the ring around its edge, and not by the objectives. Using the objectives as handles can de-center and possibly damage them.

Raman spectroscopy is based on the inelastic light scattering in a substance where the incident light transfers energy to molecular vibrations.

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I Back to top Illuminator, There is an illuminator built into the base of most microscopes. The purpose of the illuminator is to provide even, high intensity light at the place of the field aperture, so that light can travel through the condensor to the specimen.

Microscope calculations are a range of formulas used for digital microscopy applications to calculate the depth of field in microscope, field.