Nikon ECLIPSE E200 Manual De Instrucciones página 61

Chapter 4 Microscopy (Detailed Procedure)

Adjusting the Aperture Diaphragm

The aperture size is increased or decreased by rotating the condenser aperture diaphragm lever.

If the aperture diaphragm is closed, the brightness and resolution are decreased but the contrast

and range of focus are increased. If the aperture diaphragm is opened, the brightness and

resolution are increased but the contrast and range of focus are decreased.

Generally, a good image of sufficient contrast can be achieved with the aperture diaphragm

closed to approximately 70% - 80% of the objective's numerical aperture. Since the image

resolution will be degraded when the aperture diaphragm is closed too much, do not close the

aperture diaphragm to less than 60% of the objective's numerical aperture except when

observing a specimen with low contrast, such as a near-transparent specimen.

The aperture diaphragm controls the numerical aperture of the illumination. Do not use it to

control brightness. Use the brightness control dial to control the brightness.

•

The objective's numerical aperture is indicated on the side of the objective.

40x / 0.65 = magnifying power 40x, numerical aperture 0.65

•

To observe the diaphragm image, remove the eyepiece and look down the open

tube. (The eyepiece is fastened to the eyepiece tube. Loosen the screw before

removing the eyepiece.)

•

The figures on the condenser show the approximate positions of the aperture

diaphragm lever corresponding to each objective magnification. (When the

aperture diaphragm lever is moved to that position, the size of the aperture

diaphragm will be 70% - 80% of the objective's numerical aperture.) Each

time you switch the objective, align the aperture diaphragm lever to the same

figure as the magnifying power of the objective to get a good image with

sufficient contrast.

Magnifying Power: 40x

Numerical Aperture: 0.65

Corresponding objective magnification

Aperture diaphragm

lever

Objective pupil

Aperture diaphragm image

The appropriate size of the aperture diaphragm