We present an analytical design method for the three-mirror anastigmatic (TMA) telescope with mirror spacings as the free design parameter. After the optical designer determines, the system focal length and the mirror spacings according to the design requirements, the design solutions of all TMA telescopes that meet the conditions can be obtained directly according to the formulas for the mirror radius and conic constants derived. The method here can predetermine the mirror position and system envelope size before design, and can quickly give all design solutions. We give a design example using the method and compare and discuss all design solutions of TMA.
The aberration fields of misaligned on-axis telescopes can be described by nodal aberration theory. However, traditional nodal aberration theory cannot directly apply to pupil-offset off-axis systems. In our previous work, the net aberration fields of pupil-offset off-axis two-mirror astronomical telescopes induced by lateral misalignments were investigated by extending nodal aberration theory to include pupil-offset off-axis telescopes with a system-level pupil coordinate transformation through simulation. An experimental study on the net aberration fields of pupil-offset off-axis three-mirror anastigmatic (TMA) telescopes induced by lateral misalignments is further presented. Specifically, the astigmatism and coma aberration fields as well as their inherent relations are analytically expressed, simulated, and quantitatively validated with a real pupil-offset off-axis TMA telescope. Meanwhile, the differences between the aberration fields of misaligned off-axis and on-axis TMA telescopes are revealed and explicated. Our work not only contributes to a deep understanding of the net aberration fields of pupil-offset off-axis TMA telescopes induced by lateral misalignments but also represent an important validation for the extension of nodal aberration theory to pupil-offset off-axis telescopes.
In order to meet the requirement of miniaturization, high image quality and large field of view of monitor lens, based on the characteristics of monocentric lenses, and the development of curved image sensors, we designed a monitor lens optical system and all refraction surfaces and its curved image surface have the same spherical center. The monitoring optical system's FOV is 140°, the focal length is 7.88mm, the F-number is 1.50, and the total length is 14.47 mm. The monitoring optical system is up to 11-megapixel. The final design result shows that the MTF value is closed to the diffraction limit in the central field of view and the 0.7 field of view, and is greater than 0.59 at all fields of view. The RMS radiuses of different fields of view are all less than 1.1 μm . It can be clearly seen that the aberrations of each field of view are well controlled from the quantitative analysis of the transverse ray fan plot. The monitor lens has good performance in quite a large FOV with a miniaturization structure.
A large aperture space telescope with a passive structure with high stiffness and thermal stability can maintain a good image quality in a large span of disturbance. However, for the proposed more stringent requirements, it is beneficial to add active optics to the conventional design. In these telescopes, the off-axis design provides more design variables than the coaxis system and also provides greater adjusting ability for the active optics. We introduce an active optics system prototype deployed on an off-axis space telescope working at low Earth orbit. By adjusting the low-order aberrations of the primary mirror shape and adjusting the positions and attitudes of certain mirrors and the focal plane, the optical system’s image quality corrupted by gravity discharge and temperature variation is increased to the undegraded level in the average sense in the full field of view.
Active optics usually uses the computation models based on numerical methods to correct misalignments and figure errors at present. These methods can hardly lead to any insight into the aberration field dependencies that arise in the presence of the misalignments. An analytical alignment model based on third-order nodal aberration theory is presented for this problem, which can be utilized to compute the primary mirror astigmatic figure error and misalignments for two-mirror telescopes. Alignment simulations are conducted for an R-C telescope based on this analytical alignment model. It is shown that in the absence of wavefront measurement errors, wavefront measurements at only two field points are enough, and the correction process can be completed with only one alignment action. In the presence of wavefront measurement errors, increasing the number of field points for wavefront measurements can enhance the robustness of the alignment model. Monte Carlo simulation shows that, when −2 mm ≤ linear misalignment ≤ 2 mm, −0.1 deg ≤ angular misalignment ≤ 0.1 deg, and −0.2 λ ≤ astigmatism figure error (expressed as fringe Zernike coefficients C5 / C6, λ = 632.8 nm) ≤0.2 λ, the misaligned systems can be corrected to be close to nominal state without wavefront testing error. In addition, the root mean square deviation of RMS wavefront error of all the misaligned samples after being corrected is linearly related to wavefront testing error.
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