Stereo Microscope or Dissecting Miscrscope

STEREO MICROSCOPE

By Muhammad Waleed Ahsan Khan Tareen13-arid-1100

DVM 5th (Evening)PMAS UAAR

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Definition• The stereo or stereoscopic or dissecting

microscope is an optical microscope variant designed for low magnification observation of a sample, typically using light reflected from the surface of an object rather than transmitted through it.

PIR MEHR ALI SHAH ARID AGRICULTURE UNIVERSITY

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Three key parts: 1. Viewing Head/Body

• Viewing Head/Body that houses the optical components in the upper part of the microscope


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2. Focus Block• Focus Block that

attaches the microscope head to the stand and focuses the microscope


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3. Luminous stand• Stand that supports

the microscope and houses any integrated illumination.


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Conjunction purpose• Stereo microscopes are

increasingly modular. This means that the same head can be used in conjunction with different focus blocks and stands.

• For example, Microscope.com offers a range of pole stands, track stands and boom stands.

POLE STAND

BOOMSTAND

TRACK STAND


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OPTICAL COMPONENTS• As in a compound microscope, there are two optical

systems in a compound microscope: • Eyepiece Lenses • Objective Lenses


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Eyepieces or Oculars & Eyepiece tube

• Eyepieces or Oculars are what you look through at the top of the microscope.

• Typically, standard eyepieces have a magnifying power of 10x.

• Optional eyepieces of varying powers are available, typically from 5x-30x.

• Eyepiece tube holds the eyepieces in place above the objective lens.


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Objective Lenses• Objective

Lenses are the primary optical lenses on a microscope.

• In a low power microscope, they provide fixed magnification or zoom magnification.


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Focus Control & Working Stage • Most stereo microscopes have

only coarse focus controls• Working Stage is where the

specimen to be viewed is placed. Pole and track stands have simple stages since lower magnification powers require less subtle movements than high power microscopes..

• Stage Clips are used when there is no mechanical stage.


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Transmitted Illumination • Since most specimens

examined on a stereo microscope are opaque, a top light (Transmitted Illumination) is used to shed light on the specimen. Some stereo microscopes also include a bottom light (Incident Illumination).


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Modern stereomicroscope optical design. A - Objective B - Galilean telescopes (rotating objectives) C - Zoom control D - Internal objective E - Prism F - Relay lens G - Reticle H - Eyepiece TAREENPIR MEHR ALI SHAH ARID AGRICULTURE

UNIVERSITY

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Reticule• A reticle, or reticule (from

Latin reticulum, meaning "net"), is a net of fine lines or fibers in the eyepiece of a sighting device, such as a telescope, a telescopic sight, a microscope, or the screen of an oscilloscope.


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How to Calculate Stereo Microscope Magnification

• Combination of the eyepiece magnification (most commonly 10x) and the objective lens magnification (typically anywhere between 0.7x - 5x).


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Cont..• If you are using a stereo

microscope with 10x eyepieces and the zoom knob is set to 4x, the total magnification formula would look like this:

10 x 4 = 40x magnification


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Auxiliary lens• The other addition that can alter total

magnification is if the stereo microscope has an auxiliary lens added to it.

• If this is the case, the auxiliary lens is also multiplied into the equation.

• Say you are using a stereo microscope with 10x eyepieces, the zoom knob is set to 5x and you also have a 0.3x auxiliary lens on the microscope.

• Total magnification would be determined with the following formula:

• 10 x 5 x 0.3 = 15x magnification


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STEREO MICROSCOPE: OPERATING

1. Set the microscope on a flat surface in a stable and comfortable position. 2. Turn on The Transmitted/Oblique illuminator. 3. Place a small solid specimen onto the stage such as a card, coin or any

other flat, detailed object.4. Turn the Magnification adjustment knob to the lowest power and bring

the image into focus using the focus control.5. Adjust the eyepieces for the correct interpupillary distance to suit you. Do

this by moving the eyepieces closer together or farther apart until a single field of view is observed (B). Now, set the Dioptric adjustment rings on both eyepieces to the zero position (A).

6. Use the Magnification adjustment knob to set the highest magnification.7. Bring the image into focus with the focusing knob. Center the image

on some clear point of detail on the specimen.PIR MEHR ALI SHAH ARID AGRICULTURE UNIVERSITY

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Cont.. 8. Adjust the microscope down to the lowest magnification

using the Magnification adjustment knob. The image could be slightly out of focus.

9. Do not adjust the focus with the focusing knob. Adjust the focus for each eye separately using the eyepiece Dioptric adjustment rings.

10. Your microscope is now "parfocal". This means that as the microscope is zoomed from high to low magnification the image will stay in focus throughout the entire range. Each individual will have a different setting.


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Basic Groups of StereomicroscopeGreenough Design

• Old design• Used in production processes for

soldering on a miniature scale and dissecting specimens

• The advantage of the Greenough design is the similarity to a compound microscope since it allows selection of high apertures.

Common Main Objective

• New design• Used in research and

development because of its high resolution and the optical and illumination accessories available

• The CMO uses a large, single objective lens, which is shared by a pair of ocular channels and lens assembly.


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AnomaliesGreenough Design

• The disadvantage is what's known as the keystone effect. This is a slight tilt in the focal plane due to the two lenses viewing the same image at slight angles.

• As the lenses are not exactly parallel, this results in the outside of the image in the field of view to be slightly over focused or under focused. Therefore, only the central regions of the image are correctly focused at identical magnifications.


• This design virtually eliminates any image tilt in the focal plane. However, it creates an optical anomaly that makes the viewed object appear to elevate in the center, also referred to as “perspective distortion”.

• This is more of a problem in the less expensive CMO stereo microscopes so those used in top research, being more expensive and made by a major manufacturer, should not have this distortion.


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Cont..Greenough Design



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Difference between CMO & GREENOUGH designs

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Types of stereo

Stereo Fixed Microscope• The term “fixed" refers to one of the

microscopes used in stereo microscopy.• The fixed magnification uses two objective

lenses, which refer to the optical element gathering and focusing the light rays on the image.

• The magnification has a fixed degree and is limited to the capability of the lens. Changing to a stronger eyepiece increases the magnification.

• This can be useful as you cannot change to a higher or lower magnification while viewing a specimen, therefore it keeps a stable focus.


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Types of stereoStereo Turret Microscope• These types of microscopes come in a

variety of mountings, one of which is a turret style.

• Objective turret is another term for this type of mounting and indicates that an additional objective lens can be rotated into viewing position.

• This easily allows the viewer to change magnifications by simply rotating the turret mounting.

• Stereo turret microscopes are less flexible than the zoom type but are a more economical choice.


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Types of stereoStereo Zoom Microscope• The stereo zoom microscope behaves much as

its name implies and is very popular. This microscope can zoom in or out to increase or decrease the desired magnification. The available range can also be altered by changing to a stronger eyepiece.

• The stereo zoom microscope comes with a choice of stands:

a) A simple stand allows room for observation and repair of items such as watches, coins, entomology

b) A boom stand is for larger applications and can be mounted to the floor and have an added boom to act as a counterweight..


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Digital display with stereo microscopes

• Recently, video dual camera pickups have been fitted to stereo microscopes, allowing the images to be displayed on a high resolution LCD monitor.


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Uses of stereomicroscope• Erect & Three dimensional perspective• Insects disection• Detailed work such as microsurgery & watch making• Commercial inspection applications such as – soldering – circuit board inspection – repair – engraving


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Education

Stereo Microscope or Dissecting Miscrscope