A compact encoder-based focusing mechanism is proposed to compensate for axial focal-plane displacement in a space optical camera. The mechanism converts the rotation of a stepper motor into linear motion of the CCD focal plane assembly through a worm gear pair, a gear pair, and a cylindrical cam pair, while an encoder provides position feedback for closed-loop control. A displacement-count transmission model was developed and verified through MTF simulation, positioning tests, autofocusing experiments, finite element analysis, and vibration tests. The mechanism achieved a single-step control resolution of 1.38 μm and an encoder-based displacement measurement accuracy of 0.486 μm. The positioning test showed a maximum absolute error of 7 μm within a ±2 mm travel range, satisfying the ±7.5 μm requirement. Optical simulation indicated that axial defocus broadened the PSF and reduced the MTF near the 50 lp/mm Nyquist frequency. Autofocusing experiments using a resolution target showed that the normalized stripe contrast recovered to its maximum near the best-focus position, supporting the practical image-quality recovery trend predicted by the MTF simulation. The measured first natural frequency was 174.64 Hz, and the random vibration amplification ratios were below 3 in all tested directions. The results demonstrate that the proposed mechanism can provide accurate and mechanically robust compensation of focal-plane displacement.

To meet the requirements of high resolution, compact size, and ultra-lightweight for micro–nano satellite optoelectronic payloads while ensuring high structural stability during launch and in-orbit operation, mirrors were designed with high surface accuracy. The opto-thermo-mechanical system of the space camera was designed and analyzed accordingly. First, an optical system was designed to achieve high resolution and a compact form factor. A coaxial triple-reflector configuration with multiple refractive paths was adopted, which significantly shortened the optical path and laid the foundation for a lightweight, compact structure. This design also defined the accuracy and tolerance requirements for the primary and secondary mirrors. Subsequently, mathematical models for topology optimization and dimensional optimization were established to optimize the design of the main support structure, primary mirror, and secondary mirror. Two design schemes for the main support structure and primary mirror were compared. Steady-state thermal analysis and thermal control design were carried out for both mirrors. Simulations were then performed on the main system (including the primary/secondary mirror assemblies and the main support structure). Under the combined effects of gravity, a 4 °C temperature increase, and an assembly flatness deviation of 0.01 mm, the surface accuracy of both mirrors, the displacement of the secondary mirror relative to the primary mirror reference, and the tilt angle all met the overall specification requirements. The system’s first-order natural frequency was 156.731 Hz. After precision machining, fabrication, and assembly, wavefront aberration testing was conducted on the main system with the optical axis horizontal. Under gravity, the root mean square (RMS) wavefront error at the center of the field of view was 0.073λ, satisfying the specification of ≤1/14λ. The fundamental frequency measured during vibration testing was 153.09 Hz, which aligned closely with the simulated value and well exceeded the requirement of 100 Hz. Additionally, in-orbit imaging verification was conducted. All results satisfied the technical specifications of the satellite’s overall requirements.