Spatially resolved diagnosis of aero-optical transmission effects in enclosed high-temperature imaging via segmented...

Aero-optical transmission effects induced by thermally driven flow structures can severely degrade imaging performance in enclosed high-temperature environments. This study proposes a spatial-window segmented ray-tracing framework combined with covariance-based segmented contribution (CBSC) analysis to decompose the optical path difference (OPD) accumulation along the propagation axis and to enable spatially resolved diagnosis for targeted mitigation. In the representative configuration studied here, the high-temperature chamber is imaged through an observation window with a characteristic length (diameter) of approximately 88 mm. A coupled CFD-ray-tracing workflow is established to map the temperature-density field to refractive-index distributions via the Gladstone-Dale relation, and a CBSC metric based on the inter-window covariance of segmental OPD is used to quantify regional contributions to the accumulated OPD variance. Numerical results indicate that the wavefront distortion is strongly localized and dominated by the strong shear mixed-layer regions adjacent to the observation-window recess. The CBSC analysis further reveals that, under the original configuration, the single-sided dominant aberration regions (DARs) contribute 45.2% - 49.7% of the accumulated OPD variance budget over the investigated thermal conditions. Guided by this spatial diagnosis, a localized thermal-boundary optimization using thermal insulation cladding is implemented. The steady CFD-ray-tracing results show an average OPD RMS reduction of 44.9% within the identified DARs. A Zernike modal analysis of the simulated mean wavefront further indicates an 81.5% reduction in the energy of higher-order modal components, defined as the sum of squared Z₉-Z₃₆ coefficients. High-temperature target imaging experiments further validate the proposed strategy, demonstrating an average increase of 0.149 in the structural similarity index over the tested temperature range.