How to use the optical microscope condenser
①Reason for using condenser
When the magnification increases, on the one hand, the higher the magnification, the greater the number of lenses, and the more light absorbed by the lenses; on the other hand, due to the brightness of the field of view (referring to the range in which the specimen being inspected can be seen) Inversely proportional to the square of the magnification, that is, the higher the magnification, the darker the field of view. In order to obtain sufficient brightness, a condenser must be installed to focus the light on the specimen to be observed.
②The height that the condenser should be at during observation
When observing, to ensure the best observation effect, the focus of the condenser should fall exactly on the specimen. To achieve this condition, the height of the condenser must be adjusted. When illuminating with parallel light, the focus of the condenser is about 1.25mm above the center of its upper lens plane. Therefore, people often require that the condenser be raised to a point only slightly lower than its upper lens plane during observation. The height of the stage plane so that the focus of light may fall on the specimen on a slide of standard thickness. When a slide that is thinner than the standard thickness is used to hold the specimen, the position of the condenser should be lowered accordingly. When a slide that is too thick is used, the focus of the focus can only fall below the specimen, which is not conducive to precision. observation.
③Coordination of condenser and objective lens
The so-called cooperation here is to make the numerical apertures of the condenser and the objective lens consistent, so as to better conduct more detailed observations. If the numerical aperture of the condenser is lower than that of the objective, part of the numerical aperture of the objective is wasted and its maximum resolution cannot be achieved. If the numerical aperture of the condenser is larger than the numerical aperture of the objective lens, on the one hand, the specified resolution of the objective lens cannot be improved, and on the other hand, the clarity of the object image will be reduced because the illumination beam is too wide. The operation method of combining the condenser and the objective lens is: after completing the lighting and focusing operations, remove the eyepiece and look directly into the lens tube, close the iris diaphragm under the condenser to the minimum, and then slowly open it. Open it until its aperture is exactly the same size as the diameter of the field of view*, then press on the eyepiece to observe. Every time you change the objective lens, you must follow these matching operations in sequence. The frame of some condenser iris diaphragms is engraved with a scale indicating the opening aperture, which can be matched according to the scale.
