Olympus BHM Microscope

Table of Contents

About this Machine

The Olympus System Microscope for reflected light Model BHM consists of a modular, building-block system of various components and interchangeable accessories, as shown below. A wide variety of combinations, standard or optional, is available according to your requirements.

Machine Safety

How to Get Help

Ask an ETL Manager if you have any questions.

Using this Machine

These sections describe the standard usage and common pitfalls.


Below outlines the function of the various components.

To use this microscope you will need to decide which objectives (aka lenses) and which eyepieces would be best for your project. Refer to this Optical Data Chart as needed.

Objectives (lenses)

There are two types of Olympus objectives: Achromats and Plan Achromats. The achromats are most popular for general use and are corrected for chromatic aberration. The plan achromats are recommended for visual observation of a large field and photomicrography of flat objects; these are capable of producing a flat image to the edge of the field.

For immersion objectives use Olympus immersion oil. To utilize the full numerical aperture of an immersion objective, the objective and specimen are immerse. Care should be taken to prevent oil bubbles from forming in the oil film between the specimen and the objective. After use, carefully wipe off the immersion oil deposited on the top lens surface of the objective with gauze moistened with xylene. Take care not to immerse objectives other than immersion objectives.

There are a few special objectives. Long working distance objectives provide a longer working distance as compared to a standard objective of equal power. Differential interference contrast objectives are strain-free objectives of high N.A. that can be used for brightfield and differential interference contrast methods.


The eyepieces available for this microscope are computed to correct the slight residual errors left uncorrected in the objectives and are designed to further magnify the primary image from the objective, limiting the field as views by the eye. The three eyepieces available are the widefield eyepiece, the compensating eyepiece, and the photo eyepiece.


  1. Place a specimen on the mechanical stage.
  2. Adjust the stage height.
  3. Switch on the transformer.
  4. Swing the 10X objective into the light path and coarse focus.
  5. Make interpupillary and diopter adjustments.
  6. Swing in the desired objective.
  7. Fine focus.
  8. Correct the illumination system.
  9. Adjust light intensity.
  10. Adjust aperture iris diaphragm and field iris diaphragm.

Level a Specimen

  1. Put plasticine on a metal slide supplied.
  2. Place a piece of tissue paper between the specimen and the plunger of the hand press in order to prevent scratching of the polished specimen surface. If there is no tissue paper available, use gloves.
  3. Place a specimen on the plasticine, and press the specimen with a hand press until the specimen surface is properly leveled.

Interpupillary Distance and Diopter Adjustments

  1. Hold the knurled dovetail slides of the right and left eyepiece tubes with both hands and push the tubes together, or pull them apart laterally, whichever is required, while looking through the eyepieces with both eyes, until perfect binocular vision is obtained.
  2. Memorize or write down your interpupillary distance setting as seen on the scale.
  3. Rotate the tube length adjustment ring on the right eyepiece tube to match your interpupillary distance setting which you obtained from the scale (i.e. prior step).
  4. Look at the image through the right eyepiece with your right eye and focus on the specimen with the fine adjustment knobs.
  5. Next, look at the image through the left eyepiece with your left eye and rotate the tube length adjustment right to focus on the specimen without using the coarse and fine adjustment knobs.

Note: The mechanical tube length of the microscope is standardized at 200mm.

Light Path Selection

The trinocular observation tube is provided with a light path selector level to direct the light to the observation tube or to the photo tube. You will need to adjust the light path depending on your project needs. In case of long time exposure, it is necessary to darken the room or put a pair of light shield caps, provided with the trinocular tube, on the eyepiece tubes, in order to prevent light from coming on the film plane.

The light path options are as follows,

Focusing Adjustment

Note: Do not rotate the right and left coarse adjustment knobs in the opposite directions simultaneously.


  1. Lower light intensity.
  2. Switch off the transformer.


Remove your specimen from the mechanical stage and clean up your workspace. If you used immersion oil, carefully wipe off the immersion oil deposited on the top lens surface of the objective with gauze moistened with xylene (if there is no xylene just use lens cleaning paper or a cotton swab).

Tips and Tricks

Assembly (Manager’s Only): For assembly, the picture below illustrates the sequential procedure. The numbers indicate the order of assebmly of various components. Remove dust caps before mounting components. Take care to keep all glass surfaces clean, and avoid scratching the glass surfaces.


Optical Troubleshooting

Electric System Troubleshooting

Focusing Troubleshooting

Observation Tube Troubleshooting

Stage Troubleshooting