Construction of an Optical Microscope
Ordinary optical microscopes are composed of mechanical and optical parts.
(1) Mechanical part
① Mirror base: It is the base of the microscope to support and stabilize the mirror body.
②Mirror arm: It is the pillar of the microscope and the part that is held by the hand.
③Stage: It is a platform for placing sliced specimens. There is a light hole in the center, and slide holders and specimen pushers are installed on it, which are used to fix slides and move specimens. The propeller screw under the left side of the stage is used to move the slide in front, back, left and right directions.
④ Lens barrel: Located above the lens arm, the upper end is equipped with the eyepiece, and the lower end is connected to the objective lens converter.
⑤Focusing screw: Located on both sides of the mirror arm, it is used to adjust the distance between the objective lens and the stage, thereby adjusting the focal length. There are often two sets of focusing screws, the coarse and the fine, for larger and finer adjustments, respectively.
⑥ Objective lens converter: It is a disc installed under the lens barrel, which can rotate freely and convert the objective lens.
(2) Optical part
① Eyepiece: Installed on the upper end of the lens barrel, it is marked with "5×", "l0×", "l5×" and other magnifications.
②Objective lens: Installed under the rotating disk, it is generally divided into low-magnification lenses (4×, 10×), high-power lenses
(40×) and oil lens (l00×).
Microscope magnification = eyepiece magnification × objective lens magnification
③Condenser: Located under the stage, it is used to enhance the brightness of the field of view. On the right side of the condenser, there is a condenser lifting screw, which can make the condenser lift up and down, thereby adjusting the brightness of the field of view. The bottom of the condenser is equipped with an aperture, which can be enlarged or reduced to control the amount of light entering.
④Light source: It is located under the condenser, and there is a brightness adjustment switch on the left side of the mirror base.
2. How to use the microscope
(1) preparation
Hold the mirror arm with your right hand and the mirror base with your left hand to take the microscope out of the mirror cabinet and place it on the left side of the test bench. It is advisable that the rear end of the mirror base is about 6-10 cm away from the edge of the test bench. First check whether the various parts of the microscope are complete and normal.
(2) How to use the low power lens
①Aiming at the light: turn on the power switch of the microscope, turn the coarse adjustment screw to lower the stage, adjust the objective lens converter, and turn the low-power mirror to the working state (that is, align it with the light hole). When the lens is fully in place, you can A slight tapping sound is heard. Open the iris and raise the condenser into position. Then look into the eyepiece with both eyes, and you can see a white and bright field of vision.
② Place the slide specimen: place the slide specimen on the stage and fix it with a clamp (note: make the side with the cover glass or the specimen face up), and then turn the screw of the specimen propeller so that it needs to be observed Align the specimen site with the center of the light aperture.
③Adjust the focus: look at the low-magnification mirror from the side with your eyes, and at the same time use the coarse adjustment screw to raise the stage until the distance between the low-magnification lens and the slide specimen is about 0.6cm. Then observe on the eyepiece with both eyes, and at the same time slowly turn the coarse adjustment screw with the left hand to lower the stage until the object image appears in the field of view, and then turn the fine adjustment screw to make the object image in the field of view the clearest. If the object image to be observed is not in the center of the field of view, or even not in the field of view, the specimen pusher can be used to move the position of the specimen back and forth, left and right, so that the object image enters the field of view and moves to the center.
(3) Use of high magnification lenses:
①Find the structure that needs to be magnified for observation under a low-power lens, and move it to the center of the field of view, and at the same time adjust the object image to the clearest level.
②Turn the converter and align the high power lens with the light hole.
③Observe the eyepiece and adjust the focus with the fine adjustment screw (coarse adjustment screw is prohibited) until the object image is clear.
When it is necessary to replace the slide specimen, first turn away the objective lens, lower the stage, then change the specimen sheet, and then readjust from the low magnification lens to the high magnification lens according to the above operation sequence.
