The correct use of a collimation screw in an optical microscope
The use of the focusing screw to adjust the focus and find the object can be said to be an important step in the use of the microscope, but also students feel * difficult step. Students are very likely to make the following mistakes in the operation process: first, in the high magnification lens directly focus; second, regardless of the barrel up or down, the eyes are always in the eyepiece to see the field of view; third, do not understand the critical value of the object distance, the object distance is adjusted to 2 ~ 3 cm is still adjusted upward, and turn the focusing spiral very quickly. The results of the first two errors often result in the objective lens against the mount, damage to the mount or lens, while the third error is a common phenomenon when students use the microscope. In response to the above errors, the teacher must emphasise to the students, adjust the focus must be adjusted at low magnification, first turn the coarse focusing spiral, so that the barrel of the microscope slowly down, the objective lens close to the slide, but be careful not to let the objective lens to touch the slide, in the process of the eyes from the side of the objective lens, and then use the left eye towards the eyepiece to gaze at the eyepiece, and slowly reverse the adjustment of the coarse focusing spiral, the barrel of the microscope rises until the object is seen until the object image, and then the students will see the object image. At the same time to explain to the students that the general microscope object distance in 1 cm or so, so if the object distance has been far more than 1 cm, but still do not see the object image, it may be that the specimen is not in the field of view or turn the coarse focusing helix speed is too fast, at this time should be adjusted to the position of the mount, and then repeat the above steps, when the field of view of the fuzzy object image appears, it is necessary to switch to a fine focusing helix to adjust, only in this way can we narrow the scope of the search to improve the speed of finding the object image. Only in this way can the search range be narrowed and the speed of finding the object image be increased.
