Optical square

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A pentaprism.

The optical square uses a pentaprism to reflect and refract a beam or sighting 90 degrees, it is used in pairs in surveying and in a singular block in metrology.

Metrology[edit]

Used with an autocollimator or angle dekkor and mirror it can be used for machine tool axis squareness checking. For measuring the squareness of surfaces.

Optical square in surveying[edit]

Double pentaprism as used in surveying.

In surveying it is used both as a hand held tool for sighting between two poles (often with a plumb bob hung from the handle) and also mounted on a Jacob's staff.

References[edit]