Wednesday, September 17, 2008

Microscope Operating Guide - Part IV

Adjust the light intensity to the desired level, and then readjust the fine focus.

Microscope Light Intensity Adjustment

Adjust the field iris diaphragm

Field Iris Diaphragm Adjustment

Adjust the aperture iris diaphragm. The iris aperture diaphragm controls the cone of light that reaches the objectives and therefore controls the numerical aperture. Matching the numerical aperture of the illumination system (given on the iris diaphragm) with that of the objective provides better image resolution and contrast, and also increases the depth of focus.

Aperture Iris Diaphragm Adjustment


  • The presence of oil between the objective and the specimen decreases the diffraction of light that as it passes through the objective and this is important for resolution of objects at 1000X (100X objective and 10X eye piece). To use the 100X objective, also called the oil immersion objective, follow the instructions given above and:
  • Place a drop of immersion oil on the slide in the viewing area.
  • Turn the revolving nosepiece to engage the oil immersion objective.
  • Use the fine adjustment control to focus the image.
  • The oil on the specimen must be free of bubbles or the image is impaired. To remove bubbles, slightly move the oil immersion lens back and forth over the specimen.
  • It is very important that all oil be cleaned off the lens before storing the microscope.

Clean Microscope


Handling the microscope

  • To carry a microscope: first clear your desk to receive the microscope, then grasp its arm firmly, lift and support under the base with other hand, set on a cleared desk. Remove and store its dust cover in cabinet under desk. Unwrap power cord, loop once around gas outlet at rear of desk, plug into electrical outlet in front of desk.
  • Clean the lenses: use ONLY lens paper. Polish the objectives and oculars: breathe on them lightly for moisture.
  • Always begin slide set-up with the stage lowered and the lowest power objective (4x) in place.
  • Focus initially only by LOWERING the stage to the focal point using the coarse focus.
  • Use only the fine focus with higher power objectives. Make only minor changes in focus when necessary with the fine focus knob. If you totally lose focus, return to a lower power objective to find the focal point. Do not use the 100x objective unless you have received specific instructions on its use.

Cleaning the microscope
  • Don’t let the microscope get too dirty – always use the dust cover when not in use.
  • To clean the eyepiece – use a high quality lens paper. First brush any visible dust from the lens, and then wipe the lens. Do not use facial tissues, they are made from ground up wood fibers and could damage the lenses.
  • To clean the objective lenses – use a fresh piece of the lens paper each time so that you don't transfer dust from one lens to another.
  • Use lens paper on all glass parts of the microscope.
  • A cotton swab (Q-Tip) can be used in place of lens paper.

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