Unusual astigmatism encountered in an optical assembly having a moderate field of view

Kenneth R. Castle; Martin Tangari Larrategui; Kyle Price

doi:10.1117/12.2677731

28 September 2023 Unusual astigmatism encountered in an optical assembly having a moderate field of view

Kenneth R. Castle, Martin Tangari Larrategui, Kyle Price

Proceedings Volume 12669, Optomechanical Engineering 2023; 1266903 (2023) https://doi.org/10.1117/12.2677731
Event: SPIE Optical Engineering + Applications, 2023, San Diego, California, United States

Abstract

Most optical systems will display signs of axial coma when a single lens is decentered with respect to the others. Optical designers will usually select a sensitive lens as a compensator to correct that misalignment coma during assembly rather than tightening the decenter tolerances to excessively tight values. Recently, a lens design implemented two adjacent compensating lenses to address two errors – axial coma and balancing field performance. During the course of compensating the as-fabricated design, an unusual form of astigmatism was noted that was unexpected and not previously seen in our practice. This atypical astigmatism is hypothesized to be due to the two compensator lenses being decentered with respect to each other and the system optical axis itself. It scales linearly with field angle and is oriented in a specific direction across the field of view. This is opposed to natural field astigmatism, which is rotationally symmetric about the axis and varies quadratically with the field of view. Recent papers discussing linear astigmatism have indicated that it could be a problem with wide FOV optical systems, but we have found that it is evident in even moderate FOV optical systems. Further analysis has shown that this astigmatism arises when the two lenses decenter in opposite directions by roughly equal amounts. This suggests that the method of correction is straightforward in implementation, i.e., move the lenses towards each other. As often happens, orthogonal motion is usually needed as one iterates towards the final solution.

Conference Presentation

(2023) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Kenneth R. Castle, Martin Tangari Larrategui, and Kyle Price "Unusual astigmatism encountered in an optical assembly having a moderate field of view", Proc. SPIE 12669, Optomechanical Engineering 2023, 1266903 (28 September 2023); https://doi.org/10.1117/12.2677731

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