Essentially, a metallurgical microscope refers to a high power microscope used for the purposes of viewing opaque objects (objects in which light cannot pass through) these types of microscopes are different from the typical biological microscopes in that they use the principle of reflected light microscopy. This makes them ideal for viewing metallurgical samples as well as a variety of other opaque objects (ceramics, plastics, rocks etc).
There are several different types depending on configurations and function.
On the basis of configurations, there are three main types of Metallurgical microscopes. These include:
These are for the most part simple microscopes that come with an inclinable body with course and fine motion. They may also come with a stand as well as variable light control transformer in addition to a number of optics such as M10x and M45x (SL) Eye Piece.
While some of these microscopes may be binocular, they are mostly
monocular and use a bright field horizontal illuminator that allow for filter
Bench Top Metallurgical Microscopes are more advanced and are typically used for enhanced, reliable and quick assessment of metallurgical properties and other objects. They are used on the bench (working bench) and come with a number of important features including a manually revolving nosepiece, tilting binocular tube and simple polarized light. These microscopes may weigh about 10kg, which allows them more stability when is use.
A majority of these microscopes come with a trinocular head or a binocular/monocular head that allows for additional attachments such as a camera.
A good example of a research metallurgical Microscope is the Olympus GX71 that comes with a versatile modular design and used for observation methods ranging from bright field to dark field.
The Olympus is more advanced in that it allows for enhanced flexibility depending on the needs of the user through such features as a built-in magnification changer, super wide field observation as well as motorization that allows for enhanced efficiency.
*the motorized components of a research metallurgical Microscope is particularly important in that it cuts costs and saves time when the sample under investigation are many. This is because such components as the motorized filter wheel and the automated scanning stage support the process.
See Also: Trinocular Microscopes
Metallurgical microscopes are also categorized as follows:
One of the distinctive features of the semiconductor metallurgical microscopes is that they have a very big stage as well as a bigger throat depth that allows the microscope to accommodate samples of different sizes.
Advanced models of the microscope come with a number of important features such as 4 plan achromatic objectives, incident dark field and DIC illumination that allow for a better viewing of small and fine details of the specimen. This type of microscope also comes with polarized light and filters (the upright type of microscope).
One of the distinctive features of inverted microscopes is that they come with an illumination system mounted beneath the stage. This allows light to pass through the objectives, to the specimen and back to the eyepiece through reflection. One of the biggest advantages of this microscope is that it allows for much larger samples that cannot be viewed using the upright microscope.
This makes them ideal in a number of fields involved in engineering and manufacturing where the microscope serves to investigate cracks or corrosion of fractures. Some of the common features of inverted microscopes include a DIC option, adjustable intensity control, a diopter as well as plan achromatic infinity corrected objectives.
See Also: Inverted Microscopes
MicroscopeMaster Inverted Metallurgical Reviews:
Amscope 50x-1000x Inverted Metallurgical Microscope + 10MP Camera
What differentiates upright metallurgical microscopes from the others is that the illumination system is located above the sample stage, which allows light to be directed (from objectives) onto the sample and back to the eyepieces.
The microscope may come with a pillar stand or the typical base stand depending on the needs of the user. For instance; whereas the typically base stand allows for more stability of the microscope to be used for relatively small samples, the pillar stand allows for enhanced flexibility allowing for different sized samples to be viewed.
Some of the features of the upright microscope include an adjustable intensity control, a diopter, 10x wide field eyepieces as well as plan achromatic infinity corrected objectives.
MicroscopeMaster Upright Metallurgical Reviews:
OMAX 40X-2000X Infinity Trinocular Metallurgical Microscope
AmScope 40X-800X Polarizing Metallurgical Microscope with Top and Bottom Lights and 16MP Camera
Omax 40x-2500x 5MP USB3.0 Infinity Trinocular Metallurgical Microscope
While the different types of metallurgical microscopes present an advantage depending on their intended use, the inverted microscope has been shown to have a number of advantages over the upright microscope. These include:
More freedom - With the inverted microscope, optics are located below the microscope stage while the sample is typically placed above the objectives. This eliminates the limitations that the upright microscope faces with regards to the size of the sample.
Here, the user benefits from the greater working distance, which allows for bigger and heavier samples to be placed on the microscope for observations (up to 30kg)
Efficiency - Using an inverted microscope, users benefit from the fact that they view more samples within a shorter period of time.
For an upright microscope, viewing the sample involves a number of steps including lowering the stage, adjusting it, taking care to protect the sample on the stage holder etc. This is not the case with the inverted microscope given that the user can simply place the object on the stage and image it after focusing.
Focus is retained for different magnifications, which means that for the same type of sample, the user would find viewing easier.
The objective is protected - The objective of the inverted microscope is located beneath the stage in addition to the presence of a focus stop functionality (with some microscopes) which protects the objective at all times minimizing chances of damage. This is not the case with upright microscopes where the objective is above the sample stage where it can come into contact with the sample or other hard objects at any given time.
Metallurgical microscopes use EPI illumination, which is a special type of illuminator that is also referred to as reflected light or epifluorescence illumination. With this system, the object under investigation is illuminated from above. Here, the objective serves to illuminate the object.
Light (reflected) light in the system originates from lamp compartment and passes through the collector lens towards the vertical illuminator. Here, the light is controlled by other features of the microscope (light aperture and the diaphragms) and reflected by the beam splitter where it ultimately passes through the objective and illuminates the sample under investigation.
Apart from illuminating the object/sample, the microscope objective also serves to collect light that is reflected from the sample surface. From the objective, the light travels through the beam splitter before finally reaching the eyepiece.
In a system where the camera has been attached, light travels to the photomicrography port.
Metallurgical microscopes come with a number of features used for various functions. A good example of these is the filters used for the purposes of changing polarization and light intensity to view different types of samples.
These features make it possible for the user to view different types of objects using the bright field and dark field applications.
Dark field - this technique is particularly useful for viewing fractures on metal and metallic elements. Here, the dark field element is positioned in the objective head, which causes light to bend from above. This method typically results in a dark field around the specimen.
Bright field - This method has been shown to be particularly ideal for viewing alloys (composed of two or more elements). Here, light passes through a polarized lens as well as an analyzer before reaching the sample. Depending on the type of sample, a variety of colors are reflected back to the objective that travels to the eyepieces for viewing.
Using a camera is the same as with ordinary microscopes.
Metallurgical microscopes come with different microscope heads ranging from a monocular head to a trinocular head. With a trinocular head, a photo tube is available for attaching a camera. This is easy given that the user can simply attach a camera on the tube designated for the camera.
Some of the microscopes come with a camera already attached making it even easier to use the camera for capturing images or videos. While some of the cameras have a sensor that captures the real image, others have to be operated manually.
For microscopes without the trinocular head (monocular and binocular) attaching the camera simply involves removing the eyepiece or the eyepiece tube in order to directly attach the camera.
Some of the cameras allow the microscope to be connected to the microscope through a USB cable and software. Here, users simply install the software (by either downloading or using the software CD). Once installed, the software allows the user to view the image on the PC after connecting the camera.
This not only enables more than one user to view the image, but also allows for the use of the software for the purposes of making edits, measurements and comparing fields of view.
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