What is Upright Metallurgical Microscope
The Metallurgical Microscope consists essentially of an optical system and an illumination system. The optical system, includes the eyepiece lens, relay system and the objective lens. This kind of microscopes has lots of application but it is most commonly used for observation of microstructures such as material’s grain sizing, phase, grain size orientation etc. It can also be used for measurement of layer thickness, non-metallic inclusion analysis (NMI). Normally such microscope is fitted with simple polariser and Analyzer filters for filtration of reflected light.
In some case, both transmitted light and reflected light mode is included. The transmitted light is only used for transparent or translucent material observation.
The Illuminating System consists of a high intensity light source, condenser lenses (for transmitted light), an aperture diaphragm, and a plane glass reflector. The Illuminating System may also include coloured or polarising filters. Green filters are often used to improve detail and polarising filters, to reduce surface glare and to improve grain boundary definition. The aperture diaphragm is used to control the amount of light entering the objective lens, and the field diaphragm is used to minimise internal reflection within the microscope and to enhance contrast of various constituents in the specimen. The quality of objective lenses used in the microscope is perhaps the most critical in influencing image quality. Objective lenses should be properly matched to the eyepiece lens to obtain optimum quality images.
Magnifying power of both objective and eyepiece lenses is engraved on the lens mount. Total magnification of a microscope may be determined by finding the product of the eyepiece and objective lens magnification. For example: A 10X eyepiece used in conjunction with an 50X objective lens gives a magnification of 500X optically. Maximum magnification of optical microscopes is limited to about 2000X. Higher magnification does not reveal greater detail and is called “empty magnification”. Contrary to popular opinion, high magnifying power does not necessarily reveal fine details. It is the numerical aperture, or light gathering ability of a lens which largely determines the ability to resolve fine detail.
The Characteristics of a Upright Metallurgical Microscope
– 2 eyepieces of typically 10x magnification
– Objective facing down
– Rotatable nose piece / objective revolver
– Normally, more than one objective are included giving the microscope a range of magnification eg. 5x, 10x, 20x, 50x, 100x objectives
– A mechanical stage which allow sample to be move in X and Y direction
– Course and fine focusing knob for focusing of sample in the microscope
– A imaging device / camera is optional
– When necessary, software that perform NMI, grain sizing, phase analysis can be added.