LAUSR

Abstract The Beam Parallelism Translation System (BPTS) based on double pentaprisms can keep the incident beam and the emergent beam parallel. When there is relative rotation error between two pentaprisms, the image rotation still exists in the BPTS although the incident and emergent beam remain parallel. As the incident beam changes, the emergent beam and the incident beam are not parallel to each other due to the image rotation. In this paper, a mathematical model of the BPTS is established, and the image rotation caused by the alignment error of the two pentaprisms is investigated. The relationship between image rotation and the accuracy of the BPTS is analyzed. The experimental result shows that the deviation of parallelism becomes larger with the increment of the image rotation angle and the incident angle error. If the parallelism accuracy of the BPTS is required within 20′′ and the incident angle error −2° to 2°, we need to ensure the image rotation angle caused by the relative rotation of two pentaprisms less than 9′, without considering other error sources.