Introduction to optical microscope condensers
Concentrator
Concentrator is also called light collector. Located on the condenser holder beneath the specimen. It mainly consists of condenser lens and variable diaphragm. Among them, condensers can be divided into brightfield condensers (ordinary microscope configuration) and darkfield condensers.
1. Main parameters of light microscope
Numerical aperture (NA) is the main parameter of the condenser. The maximum numerical aperture is generally 1.2-1.4. The numerical aperture has a certain variable range. Usually the number engraved on the upper lens frame represents the maximum numerical aperture, which can be adjusted by adjusting the lower part. The opening degree of the diaphragm can obtain various numerical apertures below this number to adapt to the needs of different objectives. Some condensers are composed of several sets of lenses. The top set of lenses can be removed or moved out of the optical path to reduce the numerical aperture of the condenser to adapt to the illumination during observation with low-magnification objectives. 2. The function of condenser
The condenser functions like a convex lens, converging light to enhance the illumination of the specimen. Generally, the focusing point of the condenser is designed to be approximately 1.25mm above the plane of the upper lens. (The focus of focus is on the specimen to be observed, and the thickness of the slide is about 1.1mm)
3. iris diaphragm
The variable diaphragm, also called the aperture, is located below the condenser and consists of more than a dozen metal sheets with a round hole in the center. Its function is to adjust the light intensity and adapt the numerical aperture of the condenser to the numerical aperture of the objective lens. The wider the iris is opened, the larger the numerical aperture (after observation, the aperture should be adjusted to the maximum).
Below the iris diaphragm, there is also a circular filter holder.
Note: In middle school laboratories, only teacher microscopes (1600× or 1500×) are equipped with condensers, while student microscopes (640× or 500×) are equipped with rotating diaphragms. It is a disc that can rotate in a circle and is placed closely under the stage. It is a rotating diaphragm (also called a shutter). There are round holes of different sizes on the diaphragm, which are called apertures. The diameters are 2, 3, 6, 12, and 16mm respectively. Turn the rotating diaphragm. Each aperture on the diaphragm can be aligned with the light hole, and the intensity of the light can be adjusted through apertures of different sizes.
