Description of the dark field method of optical microscopy
Many transparent or translucent samples, such as bacteria, microorganisms, fine structures within cells, and crystal contents, are not easy to see clearly in a bright field microscope. The visibility of the sample can be greatly improved by using the dark field method. . What you see with the dark field method is the outline of the sample and its details that glow against the dark field background. The highest resolution of a common optical microscope is 0.2μm. Although the detailed structure of the sample cannot be clearly distinguished by a dark-field microscope, it can see the existence of fine particles above 0.004μm, that is, it can see the submicroscopic structure, which is particularly suitable for use. to observe tiny particles, bacteria, etc. Adjustment method: The main necessary component of the darkfield method is the darkfield condenser. Before use, the Kuhler illumination system must be adjusted with a bright field condenser. When replacing the dark field condenser, you need to remove the slide (sample), drop immersion oil on the top of the condenser, then place the sample slide on the object stage, and the immersion oil will be filled between the two. The condenser must be used with a 100× oil lens equipped with a variable diaphragm. Another medium-magnification dry darkfield condenser can be used with a medium-magnification objective lens. This condenser has a central light stop, and the illumination light can only enter the condenser through the light transmission ring between the light stop and the edge of the condenser. For a fully equipped phase contrast microscope, the phase contrast condenser phase ring used with the Ph3 objective lens can be used with phase contrast objectives of 10× and below to form a low-magnification dark field effect.
