Optical Design and Tolerance Analysis of a New Off-Axis Infrared Collimator

摘要

In this study, a Cassegrain type infrared collimator capable of being used in the far-infrared wavelength band of 8～12 μm was designed, and its optical tolerance caused by structural deflections was analyzed using finite element analysis (FEA). The entrance pupil diameter (EPD) and focal length of the infrared collimator were set at 200 mm and 2,000 mm, respectively. Through the optical tolerance analysis, it was observed that the deflection related to a-tilt, β-tilt, despace, and back focal length (BFL) can affect the spot diameter at the focal plane. From the results of FEA of the primary mirror stage and support shaft as well as from the results of analysis of the tolerance of a-tilt due to deflection, it was found that the deflection was caused by the self weight of the primary mirror stage and support shaft. When converted to a-tilt, the deflection reached a 0.0015°. However, it was confirmed that this deflection was extremely small compared to the marginal range of the spot diameter (±1°), which can adversely affect performance. Therefore it can be affirmed that the optical tolerance caused by deflection in the infrared collimator designed in this study did not significantly affect performance of the optical system.