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Gu NT, Chen H, Tang A et al. Embedded solar adaptive optics telescope: achieving compact integration for high-efficiency solar observations. Opto-Electron Adv 8, 250025 (2025). doi: 10.29026/oea.2025.250025
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Article Open Access
Embedded solar adaptive optics telescope: achieving compact integration for high-efficiency solar observations
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Abstract
Adaptive optics (AO) has significantly advanced high-resolution solar observations by mitigating atmospheric turbulence. However, traditional post-focal AO systems suffer from external configurations that introduce excessive optical surfaces, reduced light throughput, and instrumental polarization. To address these limitations, we propose an embedded solar adaptive optics telescope (ESAOT) that intrinsically incorporates the solar AO (SAO) subsystem within the telescope's optical train, featuring a co-designed correction chain with a single Hartmann-shack full-wavefront sensor (HS f-WFS) and a deformable secondary mirror (DSM). The HS f-WFS uses temporal-spatial hybrid sampling technique to simultaneously resolve tip-tilt and high-order aberrations, while the DSM performs real-time compensation through adaptive modal optimization. This unified architecture achieves symmetrical polarization suppression and high system throughput by minimizing optical surfaces. A 600 mm ESAOT prototype incorporating a 12×12 micro-lens array HS f-WFS and 61-actuator piezoelectric DSM has been developed and successfully conducted on-sky photospheric observations. Validations including turbulence simulations, optical bench testing, and practical observations at the Lijiang observatory collectively confirm the system's capability to maintain about λ/10 wavefront error during active region tracking. This architectural breakthrough of the ESAOT addresses long-standing SAO integration challenges in solar astronomy and provides scalability analyses confirming direct applicability to the existing and future large solar observation facilities. -
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References
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Gu NT, Chen H, Tang A et al. Embedded solar adaptive optics telescope: achieving compact integration for high-efficiency solar observations. Opto-Electron Adv 8, 250025 (2025). doi: 10.29026/oea.2025.250025
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Figure 1.
Schematic of solar telescope and ESAOT wavefront correction. (a) Traditional solar telescope and solar adaptive optical system. (b) ESAOT architecture. (c) Wavefront correction principle in a ESAOT. PM: Primary mirror; DSM: Deformable secondary mirror; FM: Fold mirror; TTM: Tip-tilt mirror; DBS: Dichroic beam-splitter; M1, M2, M3: collimator and off-axis parabolic mirrors for beam shrinking.
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Figure 2.
Wavefront detection process of conventional cross-correlation HS WFS. NCC: Normalized cross-correlation; Recon.: Reconstruction.
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Figure 3.
Measurement principle of the HS f-WFS for detecting global tip-tilt and higher-order aberrations using time-sequenced sub-images.
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Figure 4.
Design Optimization of the 61-DSM and the HS f-WFS configuration. (a) Preliminary actuator distribution of the 61-DSM. (b) Optimized actuator arrangement of the 61-DSM. (c) Zernike mode compensation performance (the first 25 orders) for both actuator configurations. (d) Control matrix condition number versus HS f-WFS spatial sampling resolution. (e) Co-registered HS f-WFS lenslet array and DSM actuator positions. Annotation: Annular region bounded by white circles denotes the clear aperture.
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Figure 5.
Schematic diagram of the numerical simulation workflow (CCC: Cross-correlation coefficient).
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Figure 6.
Numerical validation process and outcomes. (a) Representative random phase screen generated under Kolmogorov turbulence conditions. (b) First 65 Zernike mode coefficients corresponding to the phase screen in (a). (c) Temporal evolution of wavefront aberration RMS values before and after 61-DSM correction. (d) Structural similarity index (SSIM) progression for degraded and corrected images, reflecting quality improvement through adaptive optics compensation.
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Figure 7.
Laboratory validation of ESAOT using the 61-actuator DSM. (a) Screened PZT actuators. (b) Optical polishing of the 61-DSM. (c) Delivered 61-DSM. (d) Surface profile of the 61-DSM after self-correction (RMS=12.5 nm). (e) Schematic of laboratory validation system. (f) Image before wavefront correction. (g) Image after wavefront correction, showing a 15-fold increase in peak intensity. (h) Dynamic wavefront aberration correction results: the purple region represents the RMS curve with the DSM OFF (average RMS≈0.91λ), and the green region represents the RMS curve with the DSM ON (average RMS≈0.07λ).
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Figure 8.
Prototype of the 600 mm ESAOT and its first-light on-sky observation results. (a) Light-weighted primary mirror (PM) during polishing. (b) DSM integrated with the hexapod structure. (c) Completed fold mirror (FM). (d) Operational 600 mm ESAOT, with the 2.4 m Lijiang telescope visible approximately 300 m away. First-light images of the 600 mm ESAOT capturing the solar photosphere. (e) Uncorrected image. (f) Image after wavefront correction. (g) Image after wavefront correction and reconstruction. (h) Time-varying RMS of high-order wavefront aberrations before (average RMS≈0.71λ) and (average RMS≈0.17λ) DSM correction.
