Classification and Specialized Application Scenarios of Professional Optical Microscopes
1. Structure:
The magnification of the specimen is mainly achieved by the objective lens, and the larger the magnification of the objective lens, the shorter its focal length. The smaller the focal length, the smaller the distance (working distance) between the objective lens and the glass slide. The working distance of the oil mirror is very short, so special attention should be paid when using it. The eyepiece only serves to magnify and cannot improve resolution. The magnification of a standard eyepiece is ten times. A spotlight can allow light to enter the objective lens after illuminating the specimen, forming a large angle conical beam of light, which is important for improving the resolution of the objective lens. The spotlight can move up and down to adjust the brightness of light, and the variable aperture can adjust the size of the incident beam.
Microscopes can use light sources, both natural light and lighting, with lighting being better because the color and intensity are easy to control. Ordinary microscopes can use regular lighting, while high-quality microscopes require microscope lights to fully utilize their performance. Some require strong lighting, such as dark field lighting, photography, etc., often using halogen lamps as light sources. An optical microscope consists of two parts: an optical magnification system and a mechanical device. Optical systems generally include eyepieces, objective lenses, concentrators, light sources, etc; Mechanical systems generally include lens barrels, objective converters, stages, mirror arms, and bases.
2. Principle:
The magnification efficiency (resolution) of a microscope is determined by the wavelength of the light used and the numerical aperture of the objective lens. Shortening the wavelength of the light used or increasing the numerical aperture can improve resolution. The amplitude of visible light is relatively narrow, and the wavelength of ultraviolet light can improve resolution, but it cannot be directly observed with the naked eye. So reducing the wavelength of light to improve the resolution of optical microscopes is limited, and increasing the numerical aperture is an ideal measure to improve resolution. To increase the numerical aperture, the refractive index of the medium can be increased. When air is the medium, the refractive index is 1, while the refractive index of asphalt is 1.51, which is similar to the refractive index of slide glass (1.52). This way, light can enter the objective lens directly through the slide and asphalt without refraction, thereby improving resolution. The total magnification of a microscope is the product of the magnification of the eyepiece and objective lens, and the higher the magnification of the objective lens, the higher the resolution.
