Optical components of a light microscope
(1) Eyepiece
Usually consists of two sets of lenses, the upper end of a group also known as the "eyepiece", the lower end is known as the "field mirror". Between the two or in the field below the mirror is equipped with a field of view diaphragm (metal ring device), magnified by the objective lens in the middle of the image falls in the field of view diaphragm on the plane, so it can be placed on the eyepiece micrometer. In the eyepiece engraved above the magnification, such as 10 ×, 20 ×, etc.. According to the size of the field of view, eyepieces can be divided into ordinary eyepieces and wide-angle eyepieces. Some microscope eyepieces are also attached to the visual adjustment mechanism, the operator can be adjusted to the left and right eyes, respectively, visual adjustment. Another photographic eyepiece (NFK) can be used for photography.
(2) Objective Lens
Composed of several sets of lenses, mounted on the converter, also known as the objective lens. Usually each microscope is equipped with a set of objective lenses of different magnifications, including:
① low-magnification objective: refers to 1 × ~ 6 ×;
② Middle magnification objective: 6 × ~ 25 ×;
③High magnification objective: 25×～63×;
Oil immersion objective: 90×～100×.
The oil-immersion objective is filled with a liquid with a refractive index of about 1.5 (such as cedar oil) between the lower surface of the objective and the upper surface of the coverslip, which significantly improves the resolution of microscopic observation. Other objective lenses are used directly. The selection of objective lenses during observation generally follows the order from low to high, as the low magnification lens has a large field of view, making it easy to find the specific part to be examined. The magnification of the microscope can be roughly regarded as the product of the magnification of the eyepiece and the magnification of the objective lens.
(3) Concentrator
By the spotting lens and iridescent aperture composition, located in the carrier stage below. Focusing lens function is to focus the light in the field of view; lens group below the iridescent aperture can be opened up and down to control the light through the scope of the concentrator, adjusting the intensity of light, affecting the imaging resolution and contrast. Use should be based on the purpose of observation, with the intensity of the light source to be adjusted to get the best imaging effect.
(4) Light source
Earlier ordinary optical microscope with the help of the mirror on the reflector, the natural light or light reflected to the centre of the concentrator lens as a mirror light source. The reflector is composed of a flat surface and another concave mirror. Do not use the concentrator or when the light is strong with concave mirrors, concave mirrors can play the role of convergence of light; with the concentrator or when the light is weak, generally use a flat mirror. Recently produced microscopes are generally installed directly on the mirror base light source, and current adjustment screw, used to adjust the intensity of light. Types of light sources include halogen lamps, tungsten lamps, mercury lamps, fluorescent lamps, metal halide lamps, etc.
There are two types of light source illumination methods for microscopes: transmission type and reflection (falling) type. The former refers to the light source from the bottom up through the transparent mirror object; reflective microscope is to the objective lens above the light to (fall illumination) opaque objects.
