Objective lens front lens and the examined object between the different media classification
① Dry objective lens With air as the medium, such as the commonly used objective lens below 40 ×, the numerical aperture are less than 1.
② oil immersion objective lens often cedar oil as the medium, this objective lens is also called oil lens, its magnification is 90 × ~ 100 ×, numerical aperture value is greater than 1.
Numerical aperture (numerical apeature, N.A.), also called the mirror mouth rate (or opening rate). In the objective lens and concentrator are marked with their numerical aperture, the numerical aperture is the main parameter of the objective lens and concentrator, but also the most important indicator to judge their performance. The performance of the objective lens depends on the numerical aperture of the objective lens, the larger the numerical aperture, the better the performance of the objective lens. Numerical aperture and microscope performance has a close relationship, it reflects the size of the objective lens resolution, the larger the value, the higher its resolution.
Working distance refers to the distance between the lower surface of the objective lens and the upper surface of the coverslip when the object image is adjusted clearly; the greater the magnification of the objective lens, the smaller the working distance.
2. How to use the optical microscope and experiments.
Laboratory supplies
Materials and specimens: word slice, red and green wool cross slice, human blood smear.
Equipment: microscope, rubbing paper.
Reagents: cedar oil, xylene (or ether-alcohol mixture, ratio 2:3).
1)Use of 10× low magnification microscope
① Place the microscope 6~7 cm from the edge of the lab bench (at least about a fist's distance).
② Turn on the power switch of the microscope, then make the low magnification mirror aligned with the mirror stage, open the aperture, rise the concentrator and adjust the light adjusting knob to the field of view of light brightness moderate.
③Place the specimen piece: take a slide containing the specimen (hereinafter referred to as the slide specimen), and first observe it with the naked eye to determine the approximate position of the stop and reverse sides (the side containing the specimen is the front side, which is usually labelled) and the specimen. Then place the slide specimen face up on the carrier stage and clamp it with a spring clip. Move the clip with a mover to move the specimen of the slide specimen to the round hole of the carrier stage, directly above the spotting scope.
④Adjust the focus: gaze at the objective lens from the side of the microscope, while turning the coarse adjustment handwheel, so that the carrier stage rises to the highest (the distance between the objective lens and the specimen slides is about 5mm), and then while observing on the eyepiece, slowly turn the coarse adjustment handwheel, so that the carrier stage slowly descends to the field of view of the object image appears clear.
2)Use of 40× high magnification lens
①Select the target: always move the part to be observed to the centre of the field of view first under low magnification, and adjust the object image clearly.
② conversion of high-magnification objective: to prevent the lens collision slide, can be observed from the side of the microscope. Slowly turn the converter to make the high power lens aligned with the through hole.
③Adjust the focus: Observe the eyepiece while slightly adjusting the fine-tuning handwheel to obtain a clear image. If the field of view is not bright enough, rise the concentrator and open the aperture.
