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Unformatted text preview: the eyepiece. Stop down the aperture diaphragm until it is just out of view. Changing Magnification The objective lenses are para-focal, meaning that they all focus on approximately the same specimen plane. After changing magnification only a slight adjustment of the fine focus knob will be necessary. 28. Rotate the objective lens turret to position the next higher/lower magnification objective in the light path. 29. Adjust the fine focus knob to obtain the sharpest image. Note: It is a good practice to refocus each time an objective lens comes into the light path rather than skipping over one or more to get to the final magnification. Only slight focus adjustments will be needed for each step. But when skipping over objectives focusing will be more difficult because you will be so far out of focus and, if you are increasing magnification, depth of field decreases and this will require more precise focusing. Also, since working distance decreases with increasing magnification you will want to watch the objective closely to make sure it does not strike the specimen. Polarized Light Polarized light can aid in increasing the contrast in the image. This microscope employs two polarizing elements, a rotatable, removable polarizer and a fixed analyzer which can be removed from the light path but it cannot be rotated. 30. The analyzer can be in or out. 31. Rotate the polarizer to obtain the desired effect. Dark Field Illumination Dark field illumination can be used to image the details of the specimen and to ignore the larger features. It works by illuminating the specimen with a hollow cone...
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- Spring '08