How Do I Choose the Best Microscope Eyepiece?

A microscope is an optical instrument composed of a lens or a combination of several lenses, and it is a sign that humans have entered the atomic age. ^{[1] It is} mainly used to amplify tiny objects to be seen by human eyes. Microscopes are divided into optical microscopes and electron microscopes: optical microscopes were first created in 1590 by Jensen and his sons in the Netherlands. Today's optical microscopes can magnify objects by 1600 times, and the minimum limit of resolution is 1/2 of the wavelength. The length of domestic microscope mechanical cylinders is generally 160 mm. Among them, Levenhoek, a Dutch national, has contributed greatly to the development of microscopes and microbiology.

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A microscope is an optical instrument composed of a lens or a combination of several lenses.

Optical microscope consists of eyepiece, objective lens, coarse quasi-focus helix, fine quasi-focus helix, tablet clamp, clear hole, shutter, converter, reflector, stage, lens arm, lens barrel, lens holder, condenser , The diaphragm is composed.

D = 0.61 / N * sin / 2

D: Resolution

: light source wavelength

: Objective lens opening angle (opening angle of the specimen at a point on the optical axis to the objective lens opening)

If you want to improve the resolution, you can: 1. Reduce , such as using ultraviolet light as the light source; 2. Increase N, such as in cedar; 3. Increase , that is, reduce the distance between the objective lens and the specimen as much as possible

Microscopes are classified according to the principle of microscopy.

It is in

The maximum magnification of electron microscopes now exceeds 15 million times.

In 1931, M. Knoll and E. Ruska of Germany modified a high-voltage oscilloscope with a cold-cathode discharge electron source and three electron lenses, and obtained an image magnified more than ten times. The invention was a transmission electron microscope. The possibility of magnified imaging with an electron microscope was confirmed. In 1932, after Ruska's improvement, the resolving power of the electron microscope reached 50 nanometers, which was about ten times the resolving power of the optical microscope at that time, breaking through the resolving limit of the optical microscope, so the electron microscope began to receive attention.

In the 1940s, Hill of the United States used astigmatism to compensate for the asymmetry of the rotation of the electronic lens, which made a new breakthrough in the resolution of the electron microscope and gradually reached the modern level. In China, a transmission electron microscope was successfully developed in 1958, with a resolution of 3 nanometers. In 1979, a large-scale electron microscope with a resolution of 0.3 nanometers was made.

Although the resolution ability of the electron microscope is far better than that of the optical microscope, it is difficult to observe living organisms because the electron microscope needs to work under vacuum conditions, and the irradiation of the electron beam will also damage the biological samples. Other issues, such as the brightness of the electron gun and the improvement of the quality of the electron lens, need to be further studied.

Field emission scanning electron microscope

Main application: The instrument has super high resolution, and can do secondary electron image, reflected electron image observation and image processing on the surface topography of various solid samples. It has a high-performance X-ray spectrometer, which can perform qualitative, semi-quantitative and quantitative analysis of micro-area points, lines and surface elements on the surface of the sample at the same time.

Instrument Category: 03040702 / Instrumentation / Optical Instruments / Electronic Optics and Ion Optics

Index information: Secondary electron image resolution: 1.5nm Acceleration voltage: 0 30kV Magnification: 100,000-50 million times Continuously adjustable Working distance: 5 35mm Continuously adjustable Tilt: -5 ° 45 ° X-ray energy spectrum Analyzer: Resolution: 133eV Analysis range: BU

Attachment Information: ISIS Image Processing System Backscattering Probe

Field emission scanning electron microscopy, due to its high resolution, provides a reliable experimental method for the study of nanomaterials. In addition, satisfactory images can be obtained for semiconductor materials and insulators. Superconducting thin films, magnetic materials, thin film materials grown by molecular beam epitaxy, and semiconductor materials have been observed for morphology, and micro-area composition analysis has been performed on various materials , Can get satisfactory results

Light microscope structure

The structure of ordinary optical microscope is mainly divided into three parts: mechanical part, illumination part and optical part.

Mechanical part

Troubleshooting of coarse adjustment part

The main fault of the coarse adjustment is the uneven tension during the automatic sliding or lifting. The so-called automatic sliding down refers to the phenomenon that the lens barrel, the mirror arm or the stage is automatically lowered slowly under the action of its own weight without being adjusted when it is stationary at a certain position. The reason is that the gravity of the lens barrel, the lens arm and the stage itself is greater than the static friction force. The solution is to increase the static friction force to make it greater than the gravity of the lens barrel or the lens arm itself.

For the oblique cylinder and the coarse adjustment mechanism of most binocular microscopes, when the lens arm automatically slides down, you can use two hands to hold the anti-slip wheel on the inside of the coarse adjustment handwheel. . If it does not work, a professional should be repaired.

The lens barrel automatically slides down, often giving the illusion that it is caused by too loose gears and racks. Then add a gasket under the rack. In this way, although the slide of the lens barrel can be temporarily stopped, the gear and the rack are in an abnormally engaged state. As a result of the movement, both the gear and the rack are deformed. Especially when the pad is uneven, the deformation of the rack is more severe. As a result, part of the rack is tight and part of the rack is loose. Therefore, this method is not suitable.

In addition, because the coarse adjustment mechanism has been out of repair for a long time, the lubricating oil is dry, and it will have an uncomfortable feeling when lifting, and even the friction sound of the parts can be heard. At this time, the mechanical device can be removed for cleaning, greased and reassembled.

Fine-tuning some troubleshooting

The most common faults in the fine-tuning part are stuck and invalid. The fine-tuning part is installed inside the instrument, and its mechanical parts are small and compact, making it the most sophisticated part in the microscope. The malfunction of the fine-tuning part should be repaired by professional technicians. Not sure enough, don't just dismantle.

Troubleshooting objective lens converters

The main failure of the objective lens converter is the failure of the positioning device. Generally caused by damage to the positioning spring (deformation, fracture, loss of elasticity, loosening of the spring plate's fixing screws, etc.). When replacing the new spring plate, do not tighten the fixing screws for the time being. Make the optical axis correction first. After waiting the shaft, tighten the screws. If it is an internal positioning type converter, you should unscrew the large screw in the center of the rotating disk and remove the rotating disk to replace the positioning spring. The method of correcting the optical axis is the same as before.

Troubleshooting of Concentrator Lifting Mechanism

The main failure of this part is also automatic decline. The exclusion method is as follows:

(1) The lifting mechanism of the condenser of the straight tube microscope is shown in Figure 10-3-2: 1. 5. Celluloid washer 2. Head screw 3. Eccentric rack sleeve 4. Gear bar 6. Lifting hand wheel 7. Both eyes When adjusting the nut, use one hand to insert a binocular nut wrench into the binocular nut on the end face of the handwheel, and use the other hand to insert a screwdriver into the slot with the big screw at the other end. Tighten it firmly to stop the slide.

(2) The lifting mechanism of the condenser of the oblique tube microscope is shown in Figure 10-3-3:

When adjusting, first use a screwdriver to withdraw the resident screw 2 in the middle of the binocular nut 1 to 2 turns. The bearing washer 3 is tightly fitted with the resident screw 2, so it will also exit with it and detach from the end face of the toothed rod 10. Then, use a binocular nut wrench to screw the binocular nut 1 toward the adjusting seat 5. At the same time, use the other hand to turn the handwheel and perform a test. Stop the screwing of the binocular nut until the lifting mechanism is properly tightened and can stay in any position. Finally, it is enough to screw in the stop screw so that the bearing washer contacts the toothed bar 10.

The reason why the adjustment can eliminate the fault is because the inner hole of the adjusting seat 5 is tapered. The tapered sleeve 4 has a slot in the axial direction, as shown in Figure 10-3-4. When the two-eye nut 1 is rotated inward, the tapered sleeve is pushed inward, so that when the tapered sleeve is advanced, the notch becomes smaller, the inner hole shrinks, the pinion 10 is clamped tighter, and the gear rotation is increased. Friction resistance, thus preventing automatic lowering.

1 self-sliding of lens barrel

This is one of the common failures of biological microscopes. The solution to the microscope of the sleeve type structure can be performed in two steps.

Step 1: Hold the two coarse handwheels with both hands and tighten them relatively hard. See if you can solve the problem.If you can't solve the problem, you need to use a special double-column wrench to unscrew a coarse adjustment handwheel and add a friction plate. After the handwheel is tightened, if the rotation is difficult, add the friction plate It's too thick. You can change a thin one. It is easy to rotate the handwheel, and the lens barrel can move up and down easily without sliding down by itself. The friction plate can be punched with a punch using a waste photographic film and a soft plastic sheet less than 1 mm thick.

Step 2: Check the meshing state of the gear on the coarse handwheel shaft and the rack on the lens barrel. The up and down movement of the lens barrel is completed by the gear driving the rack. The optimal meshing state between the gear and the rack is theoretically that the graduation line of the rack is tangent to the graduation circle of the gear. In this state, the gear rotates easily, and the rack wears the least? There is a wrong way to add a shim behind the rack, so that the rack tightly presses the gear to prevent the lens barrel from sliding down. At this time, the graduation line of the rack intersects with the graduation circle of the gear, and the tooth tips of the gear and the rack tightly bear against each other's roots. When the gears rotate, severe grinding occurs between them. Because the rack is made of copper, the gear is made of steel. Therefore, grinding each other will damage the teeth on the rack, and many copper shavings will be produced on the gears and racks. Eventually the rack will be severely worn and unusable. Therefore, you must not use a rack rack to prevent the lens barrel from sliding down. Solving the problem of the lens barrel's self-sliding can only be achieved by increasing the friction between the coarse adjustment handwheel and the eccentric shaft sleeve. The one exception is that the graduation line of the rack and the graduation circle of the gear are apart. At this time, when the coarse adjustment handwheel is turned, the phenomenon of idling and slippage will also occur, which affects the vertical movement of the lens barrel. If this is adjusted by adjusting the eccentric shaft sleeve of the coarse handwheel, the meshing distance between the gear and the rack cannot be adjusted. It can only be solved by adding a proper sheet after the rack. The standard for adjusting the meshing distance between the gear and the rack with a shim is that turning the coarse handwheel is effortless, but it does not idle.

After adjusting the distance, add some neutral grease between the gear and the rack. Just move the lens barrel up and down a few times. Finally, the two compression screws on the eccentric shaft sleeve must be tightened. Otherwise, when the coarse adjustment handwheel is turned, the eccentric shaft sleeve may rotate, and the rack may be blocked, so that the mirror cannot move up and down. At this time, if the power of turning the coarse adjustment handwheel is too large, the rack and the eccentric shaft sleeve may be damaged. After tightening the compression screws, if you find that the eccentric shaft sleeve is still turning. This is because the screw hole thread of the compression screw is not changed. Because manufacturers change the thread by using a machine to change the thread, often one or two teeth are not changed in place. At this time, even if the compression screw is not screwed in place, the eccentric shaft sleeve will not be compressed. Found this kind of fault, as long as the thread tapping of the screw hole with M3 tap can solve the problem. I used this method to completely solve the problem of eccentric shaft sleeve rotation of 30 biological microscopes in our school.

After all the above steps are done one by one, the problem of the lens barrel sliding down is basically completely solved.

2 Shade positioning failure

This may be caused by the screws of the shutter being too loose and the positioning marbles escaping from the positioning holes. Just put the marbles back into the positioning holes and tighten the fixing screws. If the shutter is difficult to rotate after tightening, you need to add a washer between the shutter and the stage. After the thickness of the washer is tightened with screws, the shutter can be rotated easily, and the positioning of the marbles does not escape, and the shutter is preferably positioned correctly.

3 Objective lens converter is difficult to rotate or positioning failure

The difficulty in turning the converter may be that the fixing screws are too tight. Makes rotation difficult and can damage parts. If it is too loose, the bearing marbles inside will be out of track and squeezed together, which also makes rotation difficult; in addition, the marbles are likely to run outside. The diameter of the marbles is only one millimeter, which is easy to lose. The tightness of the fixing screw is based on the ease and freedom of the converter when turning, and there is no loose clearance in the vertical direction. After adjusting the fixing screws, the locking screws should be tightened immediately. Otherwise, problems will occur after the converter is turned.

Converter positioning failure can sometimes be caused by broken or elastically deformed positioning springs. Generally, it only needs to be replaced.

4Eyepiece lens is contaminated or moldy

After most microscopes are used for a period of time, the outside of the lens will be stained or moldy. Especially the high magnification objective 40X,

Use of a microscope

When using a natural light source for microscopy, it is best to use a north-facing light source, not direct sunlight; when using an artificial light source, a fluorescent light source should be used.

During the microscopy, the body should be directly facing the training platform, adopting an upright posture, with the eyes open naturally, the left eye observes the specimen, the right eye observes the recording and drawing, and the left hand adjusts the focus to make the object clear and move the specimen field of view. Right-hand recording and drawing.

The stage cannot be tilted during the microscopic examination, because when the stage is tilted, liquid or oil will easily flow out, which will damage the specimen and contaminate the stage, and affect the inspection results.

During the microscopic examination, the specimen should be moved in a certain direction until the observation of the entire specimen is completed, so that the inspection is not missed and repeated.

The heavy light of the microscope is the conversion of light, the objective lens and the adjustment of the light. Light regulation is very important when looking at parasite specimens. Because the observed specimens, such as worm eggs and cysts, are objects in natural light state, large or small, dark and light in color, and some are colorless and transparent. With different specimens and requirements during microscopy, the focal length and light need to be adjusted at any time, so as to make the observed image clear. In general, the light of stained specimens should be strong, and the color of uncolored or unstained specimens should be weak; the light of low magnification should be weak, and the light of high magnification should be strong.

1. To the light:

(1) Turn the low magnification lens under the lens barrel to align with the lens barrel.

(2) Turn the reflector to adjust to the brightest field of view without shadows. The reflector has flat and concave sides. Use a flat surface when the light source is strong, and a concave surface when it is dark. When a strong light is needed, raise the condenser and increase the aperture; when a weak light is needed, lower the condenser or reduce the aperture appropriately.

(3) Place the specimen to be observed on the stage and turn the coarse adjuster to lower the lens barrel until the objective lens approaches the specimen. While turning the coarse adjuster, you must lean over the mirror and carefully observe the distance between the objective lens and the specimen.

(4) The left eye observes through the eyepiece, and at the same time, the left hand rotates the coarse adjustment to slowly raise the lens barrel to adjust the focus, so that the object in the field of vision stops when it is seen, and then adjust the fine adjuster until the specimen is clear.

2. Use of objective lens and adjustment of light:

The microscope generally has three objective lenses, namely low magnification, high magnification, and oil lens, which are fixed to the objective lens conversion disk.

When holding the mirror, you must hold the arm with your right hand and the holder with your left hand. Do not take it with one hand to prevent the parts from falling off or hitting other places.

Handle gently, do not place the microscope on the edge of the experimental table, it should be placed 10cm away from the edge.

Hook era microscope

Avoid touching the ground.

Keep the microscope clean. The optical and lighting parts can only be wiped with lens cleaning paper. Do not wipe with a hand or a cloth, and the mechanical parts with a cloth.

Do not touch the lens and the lens with water droplets, alcohol or other medicines. If it is stained, wipe it off with lens paper immediately.

When placing slide specimens, aim at the center of the clear hole, and do not place the slides backwards to prevent the slides from being crushed or the objective lens being damaged.

Make a habit of observing with both eyes open at the same time, observe the visual field with the left eye, and draw with the right eye.

Do not remove the eyepiece at will to prevent dust from falling into the objective lens, and do not arbitrarily disassemble various parts to prevent damage.

After use, it must be restored to return to the mirror box. The steps are as follows: remove the specimen, turn the spinner to leave the lens through the clear hole, lower the stage, place the mirror flat, and lower the collector (but do not touch the reflector Mirror), close the aperture, return the pusher, cover with silk cloth and cover, and put it back into the experimental bench cabinet. Finally, use the registration form. (Note: The mirror should usually be placed vertically, but sometimes the diaphragm will break the aperture when the stage is lowered because the collector is not raised to the proper height, so it is placed flat here)

cause of issue

I. Verification method Place the standard ruler on the table of the hardness tester (or microscope), and adjust the focal length before inspection so that the ruler of the standard ruler can be clearly seen in the field of view of the eyepiece or on the projection screen. And adjust it to coincide with the engraved lines in the eyepiece, and then compare the engraved lines of the reading microscope with the engraved lines of the standard ruler. The measurement should be performed at least 5 intervals in the entire measurement range, and each interval is compared 3 times. , Take the average of 3 comparison results, and calculate the relative error W as follows:

W = ( Li - L ) / L × 100%

In the formula: W relative error (mm); Li length measured in the comparison section of the reading microscope (mm), ( i = 1 5); L the actual length of the comparison section of the standard ruler ( mm).

The scale of the reading microscope is compared piece by piece according to the above method, and the error should not be greater than ± 0.5%.

Second, the fault cause and adjustment

1. The microscope is cloudy

The main reason: dirty or moldy lenses.

Exclusion method: When there is dust or dirt on the lens, use a brush or feather to remove it, and then use lens paper or absorbent cotton dipped in a little absolute alcohol or ether to carefully wipe along the circular track, but do not let the wipe liquid lose.

2. The edge of the indentation cannot be clearly seen in the mirror

Main reason: some lenses are loose.

Remedy: Retighten the lens loose.

3. The reading microscope scale value does not coincide with the standard scale scale

The main reason: the objective lens is loose or the gasket at the connection between the objective lens and the lens barrel is lost, and the focal length is changed.

Remedy: Tighten the objective lens. If the gasket is lost, it should be repeatedly adjusted for its thickness, and fitted with a suitable gasket to the position where the scale error is the smallest.

4. The reading microscope scale value is larger than the standard scale scale

The main reason: the lens barrel grows, it may be that the lens barrel connector is loose.

Remedy: Retighten the lens barrel connector.

The reading microscope should be kept clean and not used for a long time. It can be placed in a dry box to prevent mildew. Handle with care during use to avoid damage to the microscope and affect measurement accuracy and service life.