Definition
The optical microscope (light microscope) is a transmissive optical device that uses visible light and a system of lenses to magnify and resolve small objects placed on a stage. It remains one of the most important tools in medicine, biology, and material sciences.
Principal Systems
- 1. Mechanical System
- Provides support and stability.
- Allows movement and focusing of the specimen.
- Includes base, stage, arm, focusing knobs (coarse and fine).
- 2. Illuminating System
- Provides the light necessary to visualize the specimen.
- Components: light source, condenser lens, diaphragm.
- Directs and concentrates light onto the specimen.
- 3. Optical System
- Objective Lenses:
- The most important magnifying elements.
- Front lens = converging lens that forms the initial real, inverted image.
- Additional internal lenses correct optical aberrations.
- Ocular Lens (Eyepiece):
- Magnifies the image further (usually 5×, 10×, or 15×).
- Together, objective × ocular = total magnification.
Optical Scheme
- The specimen is placed beyond the focal length of the objective lens.
- Light rays pass through and are refracted to converge behind the lens, forming a magnified real image.
- This intermediate image is then enlarged by the ocular lens into a virtual image observed by the eye.