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Setting up a trinocular compoundmicroscope for best viewing

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“Trinocular” means three oculars, or eyepieces

Ocular tube for mounting a camera

Oculars for viewing by eye

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“Compound” means having multiple objective (lower) lenses mounted on

a rotating turret (lens holder)

Rotating turret to hold objective lenses

Objective lenses

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Focusing the microscope on specimen slides can be accomplished with a coarse adjustment control for rapid adjustment, and a fine control for small adjustments, particularly

necessary at high magnification levels.

Coarse control

Fine control

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The “mechanical stage” holds specimen slides and allows them to be moved precisely under objective

lenses to focus on any area of interest.

Stage positioning

controls

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The microscope illuminator, or light source, provides light for transmission through the specimen for viewing its structure. The amount of light is modified with a

IlluminatorDiaphragm control

shutter or diaphragm using acontrol knob to open or close itfor more or less light.

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The condenser focuses light from the illuminator onto the specimen slide to provide the best lighting for viewing. It can be raised or lowered and centered for precise focusing as necessary.

It has its own shutter diaphragm too, for varying the amount of light reaching the specimen slide.

Focusing knobs

Centering controls

Diaphragm control

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To send light from the microscope to a camera mounted on the third ocular tube, a diverter-prism is moved into the field of view by pulling out its control arm.

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Setting up a microscope for best viewing involves adjusting the parts of the scope to the viewer, focusing the

scope on the specimen slide and adjusting the illuminator or light source

to the slide being viewed.

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Turn on microscope illuminator by rotating dimmer knob slowly clockwise. Fast turn-on shortens bulb life.

Dimmer knob

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Place a sample slide on the microscope stage under the lowest power objective lens.

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Adjust the microscope eyepieces so you can comfortably see a well-focused image through both

Space eyepieces so you can comfortably see through both at the same time.

If one eyepiece tube is fixed focus, close the opposite eye and, using the microscope focusing knob, carefully focus an image of the sample for the open eye. (If both eyepiece tubes are variable focus, either one will do.) Now close the other eye and use the variable focus eyepiece tube to bring the image into focus for the open eye.

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4X 40X

Focus on the specimen slide (e.g. these wood cells from a piece of paper). Using the 4X objective lens, there will be a much larger field of view but much less detail visible than

with the 40X lens.

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4X 40X

Rotate the illuminator diaphragm control until the diaphragm is closed all the way. Using the focusing knob on the condenser, bring the diaphragm image into as sharp focus as possible. Using the centering controls, be sure the diaphragm image is positioned in the center of the field of view.

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Adjust the condenser diaphragm so that the specimen features are as clearly visible as desired.

Condenser diaphragm wide open

Condenser diaphragm closed down to provide correct contrast for clear viewing

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The nature of light and lenses results in a plane of focus which becomes thinner as magnification increases. That means for a particular specimen slide, it becomes possible to focus through

the thickness of a specimen. Some parts will be in focus while others will not, as in these wood cells focused at different “depths” through the slide.

Compare

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When the microscope has been adjusted to produce the best image of a specimen, it is

ready for capturing with the camera. Now the diverter-prism must be pulled into position to

direct light up the third ocular tube to the camera mounted on it.

REMEMBER

What you see in the camera or on the image-capture viewer is what will be captured to a

digital file. NOT NECESSARILY what you see by eye through the eyepieces. BE SURE a final focus is made in the camera viewer or on the

image-capture viewer.

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REVIEW

1)Turn on microscope illuminator slowly.

2) Place specimen slide on mechanical stage

3) Focus on specimen at desired magnification

4) Adjust eyepieces for best viewing

5) Adjust condenser for best lighting

6) Adjust condenser diaphragm for best contrast

7) Refine focus for depth of field

8) Refine focus for image capture

9) Capture image