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surface roughness and straightedge surfaceplate surface gauge visual inspection profilometer opticalflat

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Surface roughness On any finished surface,imperfections are found and these take the form of a succession of hills and valleys Which vary both in height and in spacing and result in a kind of texture which in appearance or feel. Straight edge Straightedges are commonly used for testing the straightness and flatness of plane surfaces Flatness is checked by a light test The narrow edge of the tool is applied to the surface to be tested and kept horizontally at the eye level Watching for light between the straightedge and the surface along the straightedge Light seen at one place or another indicates deviation from straightness Surface plate Surface plate is used for testing the flatness of work itself and is also used for marking out work This is used for small pieces of work while the marking -out table is used for larger jobs It is used in conjunction with other gauges,the plate becomes a functional gauge in itself. Surface gauge Surface gauge is used in lay...
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Autocollimator and tool makers micro scope

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Autocollimator The autocollimator is an optical instrument and is used to measure angular displacements with high accuracy of 0.2 seconds arc It can also be used to measure the flatness of a large surface Collimation of light If a point source of light is placed at the focal point of convex lens ,parallel rays of light are reflected by the lens. This is known as collimation of light A device with a lens suitable for causing light rays from a point source to become parallel is known as a collimato r Auto collimation of light Auto collimation of light occurs when reflecting surface is used in conjunction with a collimation lens system The collimation rays will be reflected back from the surface These rays pass through lens ,and unless reflecting surface is perfectly tangential to the lens axis ,will be brought to a focus along side of the light source Principle of the autocollimator From the fig. The light in the form of parallel rays , i...
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interferometer and interferometry

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Interferometer Interferometer is an optical device used for measuring flatness of a surface and also for determining the thickness of slip gauges. It is an extension of the application of optical flat. Interferometers are based upon the principle of “ interference “ and employ wavelength of light as their measuring units. The interferometers make use of beam divider that splits an incoming ray into two parts. These two parts of the ray travel along different paths until they are recombined, usually in the same beam divider. An interferometer is an optical device which utilizes the effect of interference. Typically, it starts with some input beam, splits it into two separate beams with some kind of beam splitter (a partially transmissive mirror), possibly exposes some of these beams to some external influences (e.g. some length changes or refractive index changes in a transparent medium), and recombines the beams on another beam splitter. The power or the spatial shape of the resulti...
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