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angle
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A figure formed at the intersection of two lines.
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angle measurement
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A type of measurement method that compares an unknown angle with a known angle. Many charts are available with different angle markings.
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ball bearing
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A rotating support containing metal balls that is placed between two parts allowing them to move easily with little friction.
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caliper
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A measuring device on the optical comparator that has a scale and is used to measure the length of a part.
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chart
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A piece of translucent paper or frosted glass that contains measurement information for comparison. Charts can quickly determine if a part fits within tolerance specifications.
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collimator lens
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A type of lens that produces parallel beams of light. The collimator lens projects intense light toward the part.
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comparison measurement
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A type of measurement method that compares an unknown measurement with a known measurement. Comparison measurement allows inspectors to accept or reject a part quickly.
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contoured surface
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Any curved surface or feature differing from a straight line.
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direct measurement
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A type of measurement method that allows an inspector or operator to use a hand-held instrument to directly measure a part feature on the optical comparator screen.
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electron
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A negatively charged particle that orbits the nucleus of an atom. Electrons emit energy in the form of light.
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fixture
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A dedicated workholding device used to locate and hold a part during machining or inspection.
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ground glass
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The finely grained glass material used to make a viewing screen. Ground glass produces a fine texture that provides a bright, clear image for inspection.
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lamp enclosure
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The part on the optical comparator that covers the light source. The lamp enclosure protects the optical comparator from heat damage.
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laser
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A type of instrument that emits an intense, narrow beam of light to measure part features. Laser light yields very accurate and consistent measurements.
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lenses
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A shaped piece of glass with two opposite curved surfaces used in an optical instrument to form an image by focusing light.
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light
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The energy emitted from electrons. Light is what makes vision possible.
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light source
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The place where light originates in an optical instrument. The light source is usually very powerful and must be protected by an enclosure.
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magnification
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The enlarged view of an object by an optical instrument. Magnification allows you to see details that you cannot see with the naked eye.
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measuring microscope
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An instrument that magnifes part features for direct measurement. The measuring microscope is much smaller than the optical comparator.
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mirror
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A smooth piece of glass that forms images by reflection. Mirrors are used in optical comparators to redirect light.
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non-contact measurement
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A measurement method that inspects a part without actually touching it. Non-contact instruments often use light to inspect a part.
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optical comparator
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An instrument that projects a magnified image of a part feature onto a screen for inspection. It is also known as an optical projector.
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optical inspection
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A method of inspection that uses sight, light, and magnification to inspect the features of a part.
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optical projector
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A common term for the optical comparator.
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overlay chart
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A type of chart made of translucent paper that contains an outline of a specific part and its dimensions. An overlay chart is placed over the viewing screen and checks if a part fits in acceptable tolerance zones.
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projection magnification lens
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A type of lens that magnifies an illuminated image onto the optical comparator screen. Projection magnification lenses come in a variety of different magnifications.
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projector screen
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Another term for a viewing screen.
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radii
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The distance from the center of a circle to a point on its circumference. The plural term for "radius" is "radii."
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range
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The limit of measurement values that an instrument is capable of reading. The dimension being measured must fit inside the range of the instrument.
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screen ring
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A ring consisting of markings around its edge for measuring angles. The screen ring fits around the entire viewing screen.
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slide
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A moving piece on the staging table that allows a part to move to different positions. Slides allow the user to position the part so its shadow falls in the correct location on the optical comparator screen.
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staging table
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The surface that supports the part on an optical comparator. The staging table has slides that move the part in different positions to change its view.
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standard
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A unit of measurement to which other units are compared. The length of a light wave is used as the ultimate standard for measurements of length.
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tolerance
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The unwanted but acceptable deviation from a desired dimension. Increasingly accurate dimensions require tighter tolerances.
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translucent paper
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A type of paper that permits the passage of light. Overlay charts are made of translucent paper.
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viewing screen
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A round, glass surface on the optical comparator that displays a magnified image of a part. The viewing screen is also known as a projector screen.
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vision system
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An instrument that uses a type of video camera to magnify part features for inspection.
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watt
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A measurement that describes the intensity of light or power.
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wave
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A shape or outline that has successive curves. Light travels in waves.
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