There are two types of fluorescence microscopes in terms of their optical paths:
1. Transmission fluorescence microscope: The excitation light source is used to excite fluorescence by passing through the specimen material through a condenser lens. Commonly used dark field concentrators can also be used, and ordinary concentrators can be used to adjust the reflector to redirect and sidelobe the excitation light onto the specimen. This is a relatively old-fashioned fluorescence microscope. Its advantage is strong fluorescence at low magnification, but its disadvantage is that its fluorescence decreases with increasing magnification. Therefore, it is better for observing larger specimen materials.
2. Falling light fluorescence microscope is a new type of fluorescence microscope developed in modern times. Unlike the above, the excitation light falls from the objective lens downwards onto the surface of the specimen, using the same objective lens as the illumination condenser and the objective lens for collecting fluorescence. A dual color beam splitter needs to be added to the optical path, which is 45 degrees apart from the light uranium. Angle, the excitation light is reflected into the objective lens and focused on the sample. The fluorescence generated by the sample, as well as the excitation light reflected from the surface of the objective lens and cover glass, enter the objective lens and return to the dual color beam splitter, separating the excitation light and fluorescence. The residual excitation light is then absorbed by the blocking filter. If different combinations of excitation filters/dual color beam separators/blocking filters are used, they can meet the needs of different fluorescent reaction products. The advantages of this fluorescence microscope are uniform field illumination, clear imaging, and stronger fluorescence with larger magnification.
