Biological microscopes are compound microscopes that are primarily used to observe and study organisms and microorganisms.
Biological microscopes were the earliest type of microscopes to be invented and the most widely used compound microscope today. Humans first used simple microscopes to observe tiny objects with a lens. Later, compound microscope were invented, which then used two lenses, i.e., one eyepiece and one objective lens for secondary imaging, to obtain a larger multiple of the image.
Conventionally, we usually refer to microscopes that include various accessories such as phase contrast, fluorescence, and polarized light etc. as compound microscopes, to distinguish them from stereo microscopes. (Although stereo microscopes also have an eyepiece and an objective lens, they have two light paths, which presents a three-dimensional image).
The most basic biological microscope consists of an eyepiece, an objective lens, a microscope stage, and light source. Both the eyepiece and the objective lens are convex lenses. The objective lens first enlarges the object into a real image. The eyepiece then magnifies the real image again into a virtual image, and finally becomes an inverted magnified virtual image on the retina of the human eye.
Biological microscopes are usually used to observe transparent or translucent objects, such as animal and plant cells, tissues, bacteria and microorganisms, as well as various kinds of tiny particles by means of sectioning. They are widely used in teaching, medicine, animal or plant research and industrial fields. Modern optical microscopes have made great progress in the wavelengths of various kinds of light; illumination forms, resolution, microscope functions, structure and comfort of image acquisition and analysis, and basically meet various research needs.
According to the user's needs and the complexity of the product, general biological microscopes are divided into student-level, experimental-grade, and research-level biological microscopes.
Basic Structure of Biological Microscope
A standard biological microscope usually has at least the following basic structures:
1. Objective lens - the closest imaging lens to the observed specimen. Objective lens determines the most important properties of the microscope imaging; such as wavelength and resolution of the object light. A microscope can have several objective lenses with different magnifications.
2. Eyepiece - the lens mounted on the upper end of the microscope tube; close to the observer's eyes. Generally, microscopes can have several eyepieces with different magnifications.
3. Light source - the light source of the biological microscope is under the microscope stage. According to different needs, a light source may include an illuminating light source (bulb), an aperture diaphragm, a condenser etc. The condenser is used to condense the illumination light and also increase the illumination brightness of the specimen. Aperture diaphragm, also called iris, is used to adjust the luminous flux of light. Under the aperture diaphragm, there is usually a circular filter holder, and the optical filters are placed according to needs. A simple microscope would not have an illuminating light source, it is illuminated by natural light, and a reflector is used to illuminate the object to be observed.
4. Microscope base - located at the bottom of the microscope; to support the lens body. Usually, the light source and the electrical appliances are installed inside the base and above the base.
5. Microscope body - used to connect and stand the various components of the entire microscope, and it is also the part the user holds when moving the microscope.
6. Microscope tube - an optical path channel connecting the eyepiece and the nosepiece of the microscope.
7. Nosepiece - the turntable under the microscope tube. The nosepiece usually has 3 to 4 circular holes for mounting objective lenses of different magnification; which can be rotated onto the optical axis of the microscope for use.
8. Microscope stage - where the specimen is placed for observation. There are usually two metal tablets on the mobile station, which are used to fix the specimen of the slide. There is also usually a pusher installed for moving the specimen. There are also microscope stages that can be moved directly in the XY direction.
9. Focus knob - used to adjust the distance between the objective lens and the microscope stage (sample) to bring the objective lens into focus to get a clear picture or image. The focus knob is usually mounted with the microscope stage to achieve the purpose of moving up and down focusing through the coarse focus knob and the fine focus knob.
Biological Microscope Quick Operation Steps
Step 1. Install and Prepare:
The configuration of the biological microscope is mostly standard. Carefully check the parts on the packing list and the information on the BoliOptics website to assemble and install the microscope.
The microscope should be placed on a solid and stable work surface with the tabletop kept steady, clean, and close to a power source. It is best to place the microscope out of direct sunlight. Generally speaking, the darker the environment, the better the image is observed by the microscope. Stray light greatly influences the imaging when the microscope is used for observation, as it can damage the specimen and can also accelerate the aging of the microscope surface and components.
Step 2. Turn on the light source:
Connect the power source, turn on the power switch, and adjust the light source to a position where the brightness is moderate.
Step 3. Place the specimen (also known as the type or sample):
Adjust the coarse focus knob first, and raise the objective lens to a higher position for easy placement of the specimen. Place the slide specimen of the observed object on the microscope stage. Note that the side of the cover slip is placed face up. Then use spring pressure to clamp on both ends of the slide to prevent the specimen from moving, and then adjust the knob through the XY direction of the microscope stage to move the general position of the part of the specimen to be observed to the center of the condenser.
Step 4. Adjust the parfocal of the high and low objective lens:
First observe with low power objectives. Adjust the low power lens (such as 4X, 10X) from the objective lens or nosepiece to the optical axis. Then, adjust the focus knob to find the outline of the image. Because the low power objectives have a large field of view, it is easier to find the image and determine the part to be observed. At the same time, adjust the XY microscope stage hand button to find the position of the specimen to be observed. It should be noted that the image of the biological microscope in the field of view is usually an inverted image, that is, the specimen should be moved in the opposite direction when moving the specimen.
Then, turn the nosepiece and gradually use the high power objective (such as 40X) to move to the observation position, and finally to the maximum magnification (such as 100X). During the process, continually adjust the fine adjustment knob to find the clearest image.
With regard to the observation and use of the oil lens, it is generally carried out after the above steps, and finally make further accurate observation.
When changing from low power objectives to high power objectives, the object image can generally be seen, but it may not be very clear. When rotating to the maximum power objectives (such as 100X), only the fine focus knob should be used rather than the coarse focus knob, so as to avoid damage to the lens or the slide specimen. When the image of the maximum power objective is clear using a microscope with normal function, ensure that the low power objectives and the high power objectives are parfocal, and the focus knob is no longer adjusted. During operation, it is possible that the power of some of the objectives in the middle may not be parfocal. If so, you only need to adjust the fine focus knob slightly.
Using a binocular microscope - If the observer's binocular vision is different, adjust it by the eyetube diopter of the eyepieces. Do not adjust the focus knob.
Step 5. Adjust the Light Source:
Adjust the light intensity of the light source. Adjust the size of the diaphragm, the height of the condenser, the angle of the reflector. These adjustments need to be coordinated and adjusted with the power of objective in order to get a clear image.
Under normal circumstances, the light of the stained specimen should be strong, and the light of the colorless or unstained specimen should be dim. When adjusting between high and low power objectives, the light for low power objectives for observation should be dim, and the light for high power objectives for observation should be strong.
Step 6. Replace the specimen:
After observing the specimen - if you need to switch to another slide, you should first change the objectives back to low power, remove the slide before replacing it with a new one, and then adjust the focus again for observation. Do not change the specimen under the high power objectives as the working distance is very small, so as to prevent damage to the objective lens.
Step 7. Arranging the microscope after use:
After observing with the microscope, the objective lenses should be moved away from the light-passing hole. Turn the nosepiece so that the V-shape between the lenses is slanted to both sides.
Remove the sample.
Check the light source of the microscope - adjust the aperture diaphragm to the maximum, adjust the brightness knob to the darkest, and then turn off the power button to prevent the instantaneous high current from burning out the light source when the power is turned on next time.
Lower the microscope stage and check if any parts are damaged, if the objective lens is stained with water or oil, or if the objective body has stains or hand prints. Wipe the microscope clean, and check that the accessories are complete, the sample specimens are complete, and anything else is complete.
After the final inspection is completed, cover the microscope with a dust cover or place the microscope into a box.
Biological microscopes are the basic structure of other forms of compound microscopes that are added with various kinds of accessories or attachments. Many principles and key points are fundamentally reflected in biological microscopes.
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