The use and maintenance of biological microscopes Preparation before use
1. Installation of optical system
For newly purchased microscopes or those whose optical system has been removed, the microscope must be installed before use. When installing, in order to prevent dust from falling downward, it should be installed in the order of first up and then down, that is, according to the order of eyepiece, objective lens, condenser lens and reflector.
When installing the objective lens, the lens barrel should be raised first or the carrier stage should be lowered to keep a certain distance between the converter and the stage. Then, hold the objective lens, put it into the screw port of the converter, and rotate it slightly counterclockwise. After the objective lens is equipped with silk patterns, then screw it in clockwise until it is moderately tight. When installing the objective lens, it should be installed clockwise from small to large according to the magnification of the objective lens. When converting the objective lens, do not push the objective lens to rotate by hand, otherwise the optical axis of the objective lens will be skewed. It is best to hold the rotating disc of the converter by hand to rotate, or hold the knurled outer circle at the junction with the objective lens converter by hand to rotate.
After the eyepiece and objective lens are installed, insert the condenser into the condenser bracket under the stage. The height of the insertion should be such that when the condenser is raised to the highest point, the end surface of the lens on the condenser is slightly lower than the plane of the stage, so as to prevent the glass slide from colliding with the lens of the condenser. Then, tighten the fixing screw of the condenser. For microscopes with non-electric light sources, the reflector is finally inserted into the socket under the condenser.
2. Calibrate the optical axis
The significance of correcting the optical axis is to make the main optical axis of the objective lens, eyepiece, condenser and the center point of the variable diaphragm coincide on a straight line. Therefore, it is also called coaxial adjustment or central adjustment. If the optical axis is skewed, the aberration will increase, and the resolution and sharpness will decrease.
The inspection method is to open the variable diaphragm to the maximum, screw the low-magnification objective lens into the optical axis, and lower the lens barrel so that the distance between the objective lens and the stage is smaller than the working distance of the objective lens (below 5mm). Without placing the specimen, adjust the angle of the reflector to make the field of view the brightest; or adjust the brightness of the light source lamp to make the field of view bright and dark.
Then, unplug the eyepiece and look directly through the tube. While slowly shrinking or opening the variable diaphragm several times, when the diaphragm is closed to the minimum, the image of the diaphragm (only a little bit at this time) should just fall on the center of the aperture of the objective lens. When the aperture is opened to a certain extent, the image of the aperture should coincide with the black circle of the aperture of the objective lens. If the above two conditions are met, it means that they are "coaxial". Otherwise, adjustments are required.
Both the eyepiece and objective are fixed and cannot be adjusted. Coaxial adjustment is mainly to adjust the position of the condenser. There are two optical axis correction screws on both sides of the condenser bracket of some microscopes, and the axis can be aligned by adjusting these two screws. Another kind of concentrator is supported by three screws at 120° intervals on the frame, one of which is equipped with a spring and can be retracted; the other two screws can be rotated. Adjust the two screws to fit the shaft.
After the optical axis of the microscope is calibrated, if the condenser is not removed or other special reasons, it is not necessary to calibrate frequently.
3. Prepare the specimen
Prepare high-quality specimens for later use.
(3) Use and maintenance of biological microscopes
How to use reflectors and condensers and how to direct light 1. Dimming
For microscopes using mirrors, flat mirrors are generally used to reflect the sun's scattered light. Concave reflectors should only be used in low light or when there are distractions outside the window.
For microscopes using electric light sources, just adjust the brightness appropriately.
2. Usage of concentrator
(1) Adjustment of the height of the condenser In the case of parallel light irradiation, the focus of the general condenser falls on the center of the lens plane at its upper end about 1.25mm. When using a high-magnification lens or an oil lens, due to the large magnification, the brightness of the mirror image is small, and strong lighting is required. Therefore, the condenser should be raised to the highest point so that the focus of the condenser just falls on the specimen plane. But when using a low magnification objective lens, the condenser can be properly lowered.
(2) Usage of the variable aperture The variable aperture plays two roles. One is to control the luminous flux directed at the specimen; the other is to change the numerical aperture of the condenser. Of the two roles, the latter is dominant. In order to make full use of the resolution of the objective lens, in principle, the numerical aperture of the condenser should be the same as that of the objective lens. Otherwise, resolution or clarity will be affected.
3. Lighting method
For the electric light source microscope, when using it, just adjust the light to the appropriate brightness. No aiming is required. However, for low-end microscopes using natural light, in order to obtain good observation results, the illumination light must be fully utilized. Therefore, the light should be adjusted before the microscope inspection. When aiming at the light, turn the low-magnification lens into the optical axis, raise the condenser appropriately, and open the variable diaphragm to the maximum. Then, look through the eyepiece while turning the mirror until the field of view is brightest and clearest. If you use natural light, try to avoid the interference of window frames and tree branches outside the window.
