Introduction to Condensers for Optical Microscopy
condenser
Concentrators are also called concentrators. on the condenser holder below the specimen. It mainly consists of a condenser and an iris diaphragm. Among them, the condenser can be divided into bright field condenser (common microscope configuration) and dark field condenser.
1. The main parameters of the light mirror
The numerical aperture (NA) is the main parameter of the condenser. The maximum numerical aperture is generally 1.2-1.4, and 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. Depending on the opening degree of the diaphragm, various numerical apertures below this number can be obtained to suit the needs of different objective lenses. Some condensers consist of several groups of lenses, and the top group of lenses can be removed or moved out of the light path to make the numerical aperture of the condenser smaller, so as to adapt to the illumination of low magnification objectives. 2. The role of the condenser
The function of the condenser lens is equivalent to that of a convex lens, and it plays the role of condensing light to enhance the illumination of the specimen. Generally, the condensing focal point of the condenser is designed to be about 1.25mm above the plane of the lens at its upper end. (The focus of the light is on the specimen to be observed, and the thickness of the glass slide is about 1.1mm)
3. iris diaphragm
The iris diaphragm, also known as the aperture, is located below the condenser lens and consists of more than a dozen metal sheets, with a circular hole formed in the central part. 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 larger the iris diaphragm, the larger the numerical aperture (the aperture should be adjusted to the maximum after viewing).
Below the iris diaphragm, there is also a circular filter holder.
Note: In the middle school laboratory, only the teacher’s microscope (1600× or 1500×) is equipped with a condenser, and the student’s microscope (640× or 500×) is equipped with a rotating diaphragm. Closely attached to the stage, a circular disc that can rotate in a circle, 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 aperture, and the intensity of the light can be adjusted through the apertures of different sizes.
