96 PART V The Part of Tens
The Effect of Dirt on the Image
Some optical surfaces are more sensitive to dirt than others. In particular, the objective
lenses are critical, but anything close to the object or to a camera sensor
has a great impact on the image quality. You can easily recognize dirt on optical
surfaces if you have an idea of the best result you can expect from your application.
If you compare your expectation with the given image, you will immediately
recognize whether or not your microscope is soiled anywhere. If the sharpness or
contrast of the image is less than optimum, there is a high probability that your
microscope optics are not clean.
How to Locate Dirt
If you have the impression that you have some dirt in your microscope you can
proceed with the following steps as an easy check:
✔✔Carefully rotate the objectives by a small amount within their thread.
✔✔Check the glass slide and coverslip by moving the specimen.
✔✔Check the condenser by moving it up and down and, 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 on the protection glass of the camera sensor will not move when you move
the camera.
Types of Soiling
You may say that dirt is dirt – but that would be too simple. To decide on the
cleaning
method, you need to know what you want to wipe away. There can be dust,
glass particles from broken sample slides, tiny parts of your skin, clothing fibers,
pollen, liquid or dried-up embedding or immersion media, culture solutions re-
sidue from improper cleaning attempts, fingerprints, grease. As you can see, this
is a long list.