The stereo or stereoscopic microscope, also known as the dissecting microscope, is a modification of the optical microscope intended for low magnification observation of an object, typically utilizing light reflected from the surface of an object as opposed to being transmitted through it. Stereomicroscopes work distinctively and address the needs of the users in a unique way. The stereo microscope offers a three-dimensional view of the sample, instead of a flat image. It also has a lower magnification normally ranging from 5x – 80x, but they provide a longer working distance.
Stereo microscopes have frequently been nicknamed the workhorse of the lab or the production sector. Users spend numerous hours behind the ocular examining, viewing, reporting, or dissecting specimens. These microscope devices are extremely versatile and are intended for observing whole objects, for example, rocks, insects, and flowers, yet can likewise be utilized for observing prepared slides. The three-dimensional feature makes the stereo microscope ideal for observing surfaces of solid objects. One can utilize these units for working with watches, circuits, and even microsurgery.
In general, the size of the stereomicroscope is larger than the size of a compound one, with the measurement of the former estimated to be approximately 1-2 feet in height. The design of the stereomicroscope varies according to the model. In some stereomicroscope systems, samples are imaged using two individual compound microscope optical trains, each comprising an eyepiece, an objective, and intermediate lens components. Various other models utilize a typical objective shared between two separate optical channels. Two different images, instigating from somewhat distinct viewing angles, are projected onto the retinas of the user, where they excite nerve endings to transmit the data to the brain for processing. The outcome is a single three-dimensional image of the sample whose resolution is restricted by the optical framework parameters of the microscope and the number of nerve endings in the retina.
Stereo microscopes are essentially binoculars that enable the utilization of stereoscopic vision. The stereo microscope includes high numerical aperture objectives which can deliver high contrast images that have the lowest quantity of flare and geometrical distortion. The observation tubes have high eye-point eyepieces that can provide a field of view up to 26 millimeters. It also has a diopter adjustment that lets the image and reticle to merge into focus at the same time. Additionally, many units feature high zoom ratios (up to 12x-15x) that give a broad range of magnification (somewhere in the range of 2x and 540x) and decrease the need to change objectives. Ergonomic characteristics merged into the stereomicroscope designs help to decrease exhaustion during extended periods of operation, and new accessories allow present-day stereomicroscopes to image samples that were impractical only a couple of years back.
Stereomicroscopes can be generally divided into two fundamental types, each of which has both positive and negative attributes. The first type is the most established stereomicroscopic system, named after the creator Greenough, which uses twin body tubes that are inclined to generate the stereoscopic outcome. The Greenough design is exceptionally prominent and still utilized today by every important manufacturer. The framework utilizes two matching individual optical frameworks which are connected to the same stand at an angle. Two Porro prisms in the beam paths permit the image to be upright and accurately arranged. In addition, this design is comparatively inexpensive to manufacture. The second type is a newer framework known as the Common Main Objective (CMO). This system uses a single large objective that is shared by a pair of eyepiece tubes and lens. This version of stereo microscopes is still created today and is utilized for more sophisticated applications. This system takes into account modular use, and you can add various attachments, for example, a fluorescence attachment, iris diaphragm, ergonomic characteristics, illumination accessories, and so forth. Either type of microscope can be provided with step-type separate lenses to adjust magnification or a consistently variable zoom-type magnification system.
Selecting a microscope for using in a laboratory depends on the type of application and requirement of the user. For regular applications, for example, routine examination, PCB assessment, training, dissection, and so on, a Greenough style stereo microscope will be suitable. A Greenough model is more affordable and simple to utilize. For more sophisticated applications – for example, fluorescence or applications that entail higher resolution and magnification – a CMO type ought to be utilized. CMO microscopes will also enable the user to include ergonomic attributes into the magnifying instrument, for example, a tilting head.
Typically, a stereo microscope has three fundamental parts: a viewing head/body that contains the optical parts in the upper portion of the microscope, a focus block that connects the microscope head to the stand and helps the device to focus, and finally a stand that supports the microscope and accommodates any integrated lighting. The other components of a stereo microscope include eyepieces or oculars, eyepiece tubes, diopter adjustment ring, objective lenses, focus control, working stage, stage clips, and transmitted illumination.
The eyepieces are used for looking through the top of the microscope while the eyepiece tube holds the eyepieces in position over the objective lens. The diopter adjustment ring of the microscope enables the user to modify the focus on one eyepiece to balance the disparity in vision between the two eyes. The objective lenses are the principal optical lenses on a microscope and provide fixed magnification or zoom magnification. The focus control allows the microscope to focus on the specimen. The working stage is where the sample to be viewed is positioned, and stage clips are used when the mechanical stage is not present. Transmitted illumination consists of a top light or a bottom light.
To begin using the stereomicroscope, place your microscope on a flat surface such as a tabletop which allows a lot of space to work.
Connect the power cord of the instrument to a switch, ensuring that the excessive cord is out of the way.
Now, turn on the transmitted illuminator (if a microscopic slide or other translucent object needs to be viewed, base lighting will be more suitable but if the specimen under observation is opaque or solid, the top lighting ought to be utilized so that the light can reflect off the object’s surface).
Next, set the object on the stage plate.
If the sample is thin and flat, try to utilize the stage clips to set its position by pulling up the pointed end of one stage clip and placing it on the end of the sample.
Repeat the same process with the stage clip on the other side.
Adjust the eyepiece(s) according to the proper interpupillary distance, so it is comfortable enough to view through the microscope without exerting strain on the eyes.
To adjust the eyepiece, move the eyepieces closer together or farther apart until a single field of view is obtained.
While glancing through the eyepiece, gradually spin the adjustment knob to the lowest power and allow the image to come into focus by utilizing the focus control.
If you are unable to see anything, ensure that the specimen is placed directly below the objective lens and try again.
Once the specimen has come into focus, move it around in order to view its different parts.
Adjust the focus to a certain extent on each new region as a three-dimensional image being viewed may have a lot of different levels and it may not be possible to focus on each characteristic clearly at the same time.
Once the use of the microscope is finished, switch off the device and take out the sample.
Remove the power cord and cover the microscope to protect it from dust.
Store the device in a place where it will not be damaged from severe hot or cool temperatures etc.
Stereomicroscopes are useful for applications that require three-dimensional examination and when the perception of depth and contrast is significant to understanding the structure of the sample. These microscopes are additionally utilized when micromanipulation of the sample is needed in a big and comfortable working space. The broad field of view and variable magnification provided by stereomicroscopes is additionally helpful for biological research that revolves around the careful manipulation of fragile and sensitive living organisms.
These microscopes are also utilized in various disciplines such as education (biology, chemistry, botany, geology, and zoology), medicine, and pathology. Another application of this device is in the observation of opaque thick objects where the transmission of light is impossible for example rocks, coins, insects, etc. Stereomicroscopes are generally used in various industries like the semiconductor business, circuits, metallurgy, textiles, and different enterprises that require assembly and assessment of miniature parts.
Stereomicroscopes are irreplaceable in countless numbers of applications ranging from the production business, quality control, and materials research to forensics, biotechnology, genetic sciences, and almost all fields of biomedical research. The microscope is also used extensively in zoology, botany, entomology, histology, geology, mineralogy, and archaeology and dermatology tools of research and anatomy. It can also assist the paleontologists during the procedure of cleaning and studying fossils.
Surgical and Medical Applications
A major application of the stereomicroscope lies in the surgical and medical field where is it frequently utilized as a laboratory tool for examining, dissecting, and performing surgical procedures on the specimen. It is extensively utilized in sectioning operations and micro-surgery. Stereomicroscopes can help enhance the standard work of researchers and professionals performing research related to surgery on small animals and rodents, i.e., mice, rats, hamsters, and so forth, for developmental biology or medical studies. The purpose of utilizing stereomicroscopes is to help make the work steps proficient and cost-effective. In order to maximize the results and reduce the costs of the studies, it is essential to remove variability through optimized surgical techniques and apparatus.
Rodents and small animals are frequently used as model organisms to study and evolve treatments for diseases and medical issues which impact humans, i.e., cancer, coronary illness, stroke, neurodegenerative sickness, liver ailment, joint inflammation, diabetes, obesity, and so forth. The rodents and small animals commonly utilized in these studies are mice, rats, hamsters, guinea pigs, rabbits, etc., for their anatomical, histological, hormonal, and hereditary likeness between these animals and humans.
Many different factors play a role in making small animal surgery with microscopy a success. First, a clear image of the animal’s desired anatomical region must be obtained. This is accomplished by the bright illumination available in the stereomicroscope’s field of view from suitable light resources and high transmission optics. Next, an adequately large region of the animals’ anatomical structure must be viewed with the stereomicroscope which is achieved with the help of a large field of view utilizing eyepieces or a camera (up to 23 mm). Also, it is essential to have a lot of room to work with surgical instruments under the stereomicroscopes which entails a large working distance (up to 20 cm). When work with animals is being done in a fume hood or on a heating plate or pad, the microscope can be finely positioned over the animal effectively with an adequately rigid stand that limits vibration.
The typical approach for stroke investigations involving small animals begins with inducing an artificial stroke in an animal, normally a middle cerebral artery occlusion (MCAO). Users can work efficiently at a rapid pace by utilizing stereo microscopes with top-quality optics, pragmatic and ergonomic stands, and adaptable, built-in illumination sources. For this type of animal surgery, a stereomicroscope will give a large overview of the targeted anatomical structure with its capacity to zoom in on a particular area and also provide an ideal balance between resolution and in-focus depth.
Stereomicroscopes can also be used for performing neurosurgery where live clamping on particular nerves is needed, e.g., on the sciatic nerve on the hind limb. During this surgery, resolution and working distance become a primary concern, and stereomicroscopes on a large swing arm stand provide a good working solution. Along with better visualization during MCAO, more efficiency, and higher reproducibility, the stereomicroscopes also provide a clean setup in order to keep the working conditions hygienic. Their integrated illumination system allows for a less crowded workspace with no cables or cold lights in the area.
Stereomicroscopes can also prove to be useful in small animal cancer research to understand the process behind the role of hormones and additional signaling proteins in mammary carcinogenesis. The hormone signaling pathway found in the mammary gland could provide answers to the cancer growing effects. Transgenic mice with fluorescent proteins in the breast tissue are frequently used for such types of development studies. Presently, the surgical transplantation of mammary epithelial tissue is the only method to extensively examine the capacity of different types of cells to regenerate mammary tissue. Characterizing fluorescence of surgically extracted tissue from small animals such as mice can be possible with the stereomicroscope with a fluorescence module. The stereo fluorescence microscope has an exceptional resolution, high numerical aperture, quick magnification change, and intense fluorescence illumination all of which facilitate the examination of target anatomical structures in breast cancer research.
Store the stereomicroscope in a dry, cool, and sufficiently ventilated room to avoid fungus development on the optics (lenses).
Consistently clean the optical components as indicated by the optical cleaning guidelines provided by the manufacturer.
In case, fungus development occurs, clean as indicated by the guidelines given by the manufacturer.
To shield it from dust when not being used, wrap a cover over the microscope – preferably a vinyl covering.
Wipe down the external surfaces with a moist fabric absorbed in warm, soapy water.
Utilize a voltage stabilizer with the microscope to prevent damage to the bulbs from sudden surges in voltage.
Abstain from twisting or bending the fiber optic cables.
When replacing the bulbs in the microscope, avoid contact with fingers.
Try not to shift the microscope while the bulb is still hot since extreme vibrations may harm the filament.
Perform maintenance checks after six months and cleans and oil the wheels and brakes.
One of the primary advantages of utilizing the stereo microscope is the comfort of the two eyepieces which you barely get in any of the customary microscopes. Most of the time, it gets exceptionally irritating and aggravating when we have to close one eye and analyze through the other while seeing through the old and conventional microscopes. In the stereo microscope, the two-way eyepieces allow the user to keep both eyes open while looking at the sample. Additionally, the eyepieces have rubber fitting supports which make the work easier.
Another advantage of the stereomicroscope is that the device provides a three-dimensional image of the sample which makes it possible to obtain a realistic and original image of the object which is very clear. The stereomicroscope, unlike a conventional microscope, also has a great option of adjusting the focus of the microscope. This provides a large magnified and clear image of the specimen which makes the examination of the object all the more easy and precise.
The dual illuminator system is also an additional benefit of the stereomicroscope. The framing of the device is done in such a way that the dual illuminator gives light from over the sample as well as the light from under the sample. This provides an ideal observation of the image’s inadequate light, thus making the examination more efficient and accurate.
Furthermore, the low-power stereomicroscope provides a large depth of field and a wide field of view. This facilitates observation of samples where it is essential to demonstrate elements in relation to encompassing structures simultaneously with those at various levels, for example, in the dissection technique.
The stereo microscope comes with its own set of limiting factors. The main concern of this device is the working distance between the lens and the specimen. Magnification has an inverse correlation with working distance and field of view. This implies, in basic terms, that as the magnification being used on the microscope increases, there will be a decrease in the working distance and field of view and vice versa. So, it is important to select a microscope with magnification settings that will provide a sufficiently large field of view to observe the sample and most importantly, a working distance large enough to accommodate the sample between the lens and the base along with achieving the focus at the required level of magnification.
Additionally, a limitation of the Greenough model is known as the keystone effect. There is a minor tilt in the focal plane because of the two lenses seeing the same image at different angles. Due to the fact that the lenses are not entirely parallel, the outer region of the image in the field of view may become slightly over focused or under-focused. As a result, only the central parts of the image are properly focused at identical magnifications. Whereas the Common Main Objective (CMO) model practically removes any image tilt in the focal plane, it may create an optical anomaly – known as perspective distortion – that makes the examined image appear to be elevated in the center.
The stereoscopic microscope – or the dissecting microscope – is designed for low magnification three-dimensional viewing of a sample, using the light reflected from the surface of the sample as opposed to being transmitted through it.
Stereomicroscopes are divided into two basic types: the Greenough model and the Common Main Objective (CMO) model.
A stereo microscope has three primary parts: a viewing head/body, a focus block, and a stand.
The other components include eyepieces, eyepiece tubes, diopter adjustment ring, objective lenses, focus control, working stage, stage clips, and transmitted illumination.
Stereomicroscopes are used in a wide variety of fields like surgery, medical science, forensics, biotechnology, genetics, biological sciences, geology, mineralogy, archaeology, semiconductor industry, metallurgy, and textile industry, etc.
The benefits of the stereomicroscopes include the comfort of the two eyepieces, a three-dimensional image, a dual illuminator system, a large depth of field, and a wide field of view.
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Girman, P., Kriz, J., & Balaz, P. (2015). Rat Experimental Transplantation Surgery. Switzerland: Springer International.
Siemionow, M. Z. (2015). Plastic and Reconstructive Surgery. London: Springer.