Before cleaning your microscope you must first be able to recognize dirt and debris that could be affecting the image quality.
The Effect of Dirt on the Image
The closer any dirt is to the object or to a camera sensor, the greater is the effect on the live or captured image. To ensure a clear crisp image, you must regularly perform microscope maintenance and keep the following surfaces clean and clear:
- The external surface of the front lens of the objective
- The surface of the camera sensor and its protective cover glass
- Both surfaces of the cover slip
- The surface of the specimen slide
- The surfaces of the camera adapter optics
- The surfaces of the condenser front lens
- The outer and inner surfaces of the eye lens of the eyepiece and the surfaces of graticules
- The outer surface of the protective glass covering the light exit opening of the illuminated field diaphragm
- Other glass surfaces in the light path - bulbs, fluorescence filters, beam splitters, collector lens, contrast and heat filters
Some optical surfaces are more sensitive to dirt than others. The front lens of the objective is critical. Exposure of the front lens of any objective to dust is greater in case of an inverted microscope than an upright microscope. The front lens of an immersion objective should be cleaned to remove residue both after use and before fresh immersion liquid is applied.
How to Recognize Dirt
Learning how to clean a microscope also requires learning how to recognize and locate dirt. To recognize dirt on optical surfaces, you should have an idea of the best result you can expect from a specific microscopy method and in a specific application. If you then compare your expectation with the visual image in terms of maximum definition, best contrast and cleanness, you will immediately recognize whether or not your microscope has dirt somewhere. If the sharpness or contrast of the image is less than optimum, there is a high probability that your microscope optics are not clean. There is also a chance you have a larger optical issue (de-cementing, alignment issues, or oil in your objective.)
To locate the dirt, proceed as follows:
- Carefully rotate objectives and cameras by a small amount within their thread
- Check specimen slide and cover slip by moving the specimen while focusing the upper and lower surfaces in succession
- Check the condenser by moving it up and down, if possible, slightly swiveling or turning the front lens.
The affected optical surface is identified when the dirt follows the movement of the suspected optical component. The camera is the only exception to this rule: dirt within the camera will not move when you move the camera.
Dirt on the front lens of an objective is easily detected if you look at an evenly lit surface from the rear end of the objective. The inner lens components produce an enlarged image of even the smallest bit of dirt on the front lens.
Different Types of Soling
You must differentiate between dust particles ( e.x. glass abraded from specimen slides, flakes of the users skin, particles from clothing, pollen) and other kinds of soling (e.x. liquid or dried-up embedding or immersion media, culture solutions residue from improper cleaning attempts, fingerprints, or grease).
Dust may either rest loosely on optical surfaces or more of less stick to them. Other dirt may be soluble in water or organic solvents for complete removal.
A blurred image my not always be due to dirt: Using an objective with a large numerical aperture in conjunction with a cover slip of the wrong thickness may result in blurred images.
Cleaning Agents & Methods
You will want to remove all dust and dirt without leaving any residue of the cleaning agent and without damaging the surfaces. It is a common misconception that lens tissue is the appropriate material for cleaning. For proper microscope maintenance, do not use lens tissue as the papers are too harsh and do not absorb the dirt efficiently or quickly enough. In order to properly clean a microscope, the following utensils and agents are required.
- Long, thin wooden sticks preferably made of bamboo or a comparable not too flexible material.
- High purity cotton
- Absorbent polyester swabs for optical cleaning
- Kim Wipes
- Dust blower
- Distilled water
- Freshly prepared solutions of 5-10 drops of dish-washing liquid in 10 ml of distilled water.
- Solvent for removing greasy or oily dirt (acetone, lacquer thinner, etc).
For the quick and easy cleaning of flat surfaces (removing oil from cover slips or front of lenses) use Kim Wipes soaked in diluted dish-washing liquid. For cleaning all other optical surfaces, use freshly made cotton swabs as they absorb dirt through their microfiber surfaces. Freshly made cotton swabs can be made by winding the cotton around the thin wooden sticks.
- Blow all loose dust particles away with a dust blower.
- Remove all water-soluble dirt with distilled water. If this is not successful, repeat using diluted dish-washing liquid. Remove any remaining residue with a dry cotton swab, but breathe on the surface first to generate a film of moisture.
- To remove oily dirt, first use diluted dish-washing liquid. If the result is not satisfactory repeat using a solvent as listed above.
- Greasy dirt must always be removed with a solvent.
- After cleaning, inspect the surface.
Place the objectives, eyepieces, and cameras on a dust-free surface to be cleaned. All other components to be cleaned should be accessible in the best way possible.
For cleaning optical surfaces move the moist cotton swab in a spiral motion from the center to the rim. Never wipe in a zigzag pattern ans this will spread the dirt.
It is important to note that while using solvents (e.g. acetone) will help remove greasy dirt, they can also damage and attack plastic and rubber. Be careful when using solvents.
While this procedure may seem simple and easy we would always recommend having a professional clean and service your microscope. Doing this the improper way can damage your lenses, alter alignment (from removing and putting optical components back on), or cause you to spread the dirt instead of cleaning the dirt.
***Microscope Central is not responsible for any damage or issues that may arise from a user following these instructions. We recommend leaving this job to a professional.***