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Autocollimator | Autocollimator

Key Words: darkfield, Brightfield, graticule

Definition:An autocollimator is an optical instrument for the non-contact measurement of angles


Autocollimation uses light to measure angles. It operates by projecting light made parallel (collimated) through an objective onto an object with a reflective surface. If the surface is perpendicular to the projected light, the beam is reflected back to its point of origin. If, however, the surface is tilted relative to the optical axis of the collimator, the reflected light is displaced (visualized against a graticule - usually a crossline). Any deviation between the projected and reflected beam is measured against a scale and measured in arcseconds*). Autocollimators may use either visual detection (by eye) or digital detection using a photodetector. Autocollimators can be used to detect and visualize microscopic edges enabling measurement of angular deviations in from parallelism, flatness and perpendicularity.

*An arcsecond is one sixtieth of an arcminute, which is equal one sixtieth (1/60) of a degree or pye/10800 radians.


Autocollimators are used in industrial and manufacturing environments for precision alignment of mechanical components, the detection of angular movement and angular monitoring over time and to ensure there is no angular error in a system and to ensure compliance with angle specifications and standards.


Nikon's autocollimators provide the accuracy and reliability required for measurements such as checking parallelism, squareness, flatness, straightness of movement and calibration of rotary devices. Autocollimators are available using brightfield or darkfield imaging.


Nikon's 6D darkfield autocollimator makes high-precision measurements simultaneously on two axes. This high precision autocollimator has a 70mm aperture, which provides bright and clear reflected images. It also projects a bright, clear crossline for easy alignment and measurement. Reading of angular displacement (with a resolution of 0.5 arcseconds) is via an easy-to-read large-diameter micrometer drum.

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