Structure and function of biological microscope in grade one.

The magnification of the specimen is mainly completed by the objective lens. The greater the magnification of the objective lens, the shorter its focal length. The smaller the focal length, the smaller the distance (working distance) between the lens and the objective glass slide. The working distance of the oil mirror is very short, so special attention should be paid when using it. The eyepiece only magnifies, but it can't improve the resolution. The magnification of a standard eyepiece is ten times. The condenser can make the light enter the objective lens after illuminating the specimen, forming a cone beam with a large angle, so it is very important to improve the resolution of the objective lens. The condenser can move up and down to adjust the brightness of the light, and the aperture can adjust the size of the incident beam.

The light source of microscope can be natural light or light, especially light, because the color and intensity of light are easy to control. Ordinary microscopes can use ordinary lamps, and high-quality microscopes need microscope lamps to give full play to their performance. Some need strong lighting, such as dark field lighting and photography. And halogen lamps are often used as light sources. An optical microscope consists of an optical amplification system and a mechanical device. Optical system generally includes eyepiece, objective lens, condenser, light source, etc. Mechanical system generally includes lens barrel, objective lens converter, stage, arm and base, etc.

2. Principles:

The magnification efficiency (resolution) of microscope is determined by the wavelength of light wave and the numerical aperture of objective lens. Shortening the wavelength of the light wave or increasing the numerical aperture can improve the resolution. The wavelength of visible light is relatively narrow, and the wavelength of ultraviolet light can improve the resolution, but it cannot be observed directly with the naked eye. Therefore, it is limited to improve the resolution of optical microscope by reducing the wavelength of light, and increasing the numerical aperture is an ideal measure to improve the resolution. In order 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 aromatic asphalt is 1.5 1, which is similar to the refractive index of glass slide (1.52), so that the light can directly enter the objective lens through the glass slide and aromatic asphalt without refraction, thus improving the resolution. The total magnification of microscope is the product of the magnification of eyepiece and objective lens. The higher the magnification of objective lens, the higher the resolution.

Second, the use of ordinary microscope

1, observed at low magnification

First, fix the position of the low-power objective lens, then place the specimen, rotate the reflector, adjust the light, raise the objective lens, lower the objective lens until the specimen can be seen, and then use fine adjustment to align the focal length for observation. Except for a few microscopes, the condenser should be placed at the highest point. If an image of an external object appears in the field of view, the condenser can be lowered slightly and the image can disappear. The iris aperture under the condenser should be adjusted to a suitable size to control the amount of incident light and increase the difference between light and shade.

2. High magnification observation

Microscope design is generally the focus of * * *. After the low-power mirror is focused, the high-power mirror is basically focused, as long as it is slightly rotated and fine-tuned. Some simple microscopes are not the focus of * * *, or they can't reach the focus of * * * because of changing the objective lens. It is necessary to move the high-power objective lens down and then adjust the focal length up. The aperture of the aperture should be enlarged to form a sufficient cone angle. Move the condenser up and down slightly to see if the image is clear.

3, oil immersion mirror observation

The working distance of the oil mirror is very small, so it is necessary to prevent the lens and objective lens on the holster from being damaged. When it is used, it is generally through low power and high power to immerse the mirror in oil. When the high-power objective lens is aimed at the specimen, observe it with an immersion lens. Slide specimens can also be directly observed by oil immersion lens without passing through low and high power objective lenses. If the microscope has an automatic drop stop device, after oiling the slide, move the oil immersion mirror down to the oil drop until it stops falling, and then adjust the focal length through fine adjustment. If there is no automatic drip stop device, the method of focusing is to look from the side of the microscope, move the oil immersion mirror down until it touches the glass slide slightly, and then lift it up through fine adjustment to focus.

When using the oil immersion mirror, the stage should be kept horizontal to prevent oil from flowing out. The oil used for the oil immersion mirror should be clean, the condenser should be raised to the highest point, and the aperture under the condenser should be enlarged, otherwise the numerical aperture will be reduced and the resolution will be affected. The adjustable microscope lamp should be used as the light source for oil immersion lens and high power lens observation.

Third, the maintenance of ordinary microscope

Microscope is a precise and expensive instrument, which must be well maintained. Put the microscope back into the original mirror box or mirror cabinet after use, and pay attention to the following matters:

1. After observation, take out the observed slide specimen.

2. If you have used an oil-immersed mirror, first wipe off the oil on the lens with mirror paper, then wipe it with xylene for 2-3 times, and finally wipe off the xylene with mirror paper.

3. Turn the objective lens converter and place it at the low power mirror position.

4. Lower the mirror body to the lowest position, adjust the position of the sample Mover on the stage, and cover it with a dust cover.

The protection of lenses is the most important. To keep the lens clean, you can only wipe it with soft mirror-wiping paper without short hair. The mirror cleaning paper should be put in the paper box to prevent dust. Never wipe the lens with a handkerchief or gauze. If necessary, the objective lens can be cleaned with solvent, but care should be taken to prevent the adhesive for fixing the lens from dissolving. According to different cementing agents, different solvents can be selected, such as alcohol, acetone, xylene, etc., among which xylene is the safest. The method is to dip a small amount of xylene in absorbent cotton ball, gently wipe it, immediately wipe off xylene with mirror paper, and then blow off the possible residual short wool with ear washing ball. Whether the eyepiece is clean or not can be observed under a microscope. Turn the eyepiece. If stains can be seen in the field of vision, it means that the eyepiece has been stained with dirt. You can wipe the lens with mirror wiping paper. If it can't be removed, clean the lens below, and then blow off the short wool with an ear washing ball. When wiping the eyepiece or removing the eyepiece for other reasons, cover the lens barrel with wiping paper to prevent dust from entering the lens barrel and falling on the objective lens below the lens barrel.