5.4 Lesson 4: Microscope
- The compound light microscope was invented in the 17th century in Europe but still represents a major tool for the Trichologist. Most compound light microscopes produce magnifications of 50x to 500x and are suitable for viewing the hair shaft and root.
- The important parts of the microscope are: - Ocular Lens (Eyepiece): lens that the Trichologist looks through (can be monocular–one eyepiece; or binocular–two eyepieces). - Objective Lens: closest lens to the object of study (ex. hair). Usually attached to a revolving nosepiece that can be turned to lenses of greater or lesser magnification. - Coarse adjustment knob: helps make larger focus changes. - Fine adjustment knob: helps make smaller focus changes. - Iris diaphragm: helps make changes to the amount of light passing through the object and entering the objective lens. - Stage: where the object is positioned. Often has stage clips attached to hold the object in place.
- The magnification of a compound light microscope is determined by multiplying the power of the ocular lens by the power of the objective lens (ex. ocular = 10x; objective = 40x: Total Magnification 10 x 40 = 400).
- Field of View (FoV) is the amount of an object that can be seen when looking through the microscope. The larger the magnification, the smaller the field of view (in the example to the right, the FoV is only what is in the circle–the ‘F’ and ‘W’ would not be seen under the microscope).
- Micrometer (µm) is the unit of linearmeasurement used to measure hair diameters. Special lenses can be attached to the ocular lens to help in this measurement.
- Images of the object are seen through the ocular in a different perspective than when the object is looked at normally. The image is ‘flipped over’ and ‘upside down’ in comparison to the object’s appearance on the stage without a microscope. For example a “p” on the stage will look like a “d” through the ocular.
- Other microscopes of interest to the Trichologist:
-Digital Microscope: hand held microscope that is attached to the computer for easy viewing of the hair and scalp during consultation.
-Dissection Microscope: a light illuminated microscope that gives a three dimensional (3-D) image to better view a specimen undergoing dissection.
-Confocal Microscope: uses a laser light that scans across a specimen with the aid of scanning mirrors. The image is then placed on a digital computer screen for analyzing.
-Scanning Electron Microscope (SEM): uses electron illumination. Electrons bounce off the specimen to give a 3-D image. It has a high magnification and high resolution, however, pictures are in black and white (see image to the right).
-Transmission Electron Microscope (TEM): is electron illuminated. Electrons pass through thin slices of a specimen, such as skin tissue, to obtain a 2-D view. It has high magnification and high resolution.