Definition of autocollimator

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Photonics Dictionary

autocollimator

An autocollimator is an optical instrument used for measuring small angular deviations with high precision. It operates on the principle of autocollimation, where a light source is directed onto a mirror surface, and the reflected light is observed and analyzed to determine the angular displacement of the mirror.

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The basic components of an autocollimator typically include:

Light source: Autocollimators use a light source, often a lamp or a laser, to generate a beam of light.

Collimating optics: The collimating optics focus the light into a parallel beam, ensuring that the light rays are nearly parallel when they reach the mirror surface.

Mirror: The mirror under test is placed in the path of the collimated light beam. The mirror reflects the light back toward the autocollimator.

Reticle or eyepiece: The autocollimator is equipped with a reticle or an eyepiece with a scale or crosshairs. The observer views the reflected light through the eyepiece and measures the displacement of the reflected image relative to the reference marks on the reticle.

When the mirror is perfectly aligned with the optical axis of the autocollimator, the reflected light beam retraces its path, and the image appears centered on the reticle. Any angular deviation of the mirror from the optical axis causes a displacement of the reflected image relative to the reference marks on the reticle. The magnitude of this displacement is proportional to the angular deviation of the mirror.

Autocollimators are commonly used in various applications, including precision alignment of optical components, measurement of angular deflections in mechanical systems, and calibration of angular instruments. They provide highly accurate and repeatable measurements of angular deviations, making them invaluable tools in fields such as optics, metrology, and precision engineering.