Step-Free Coating Technique for Four-Quadrant Wind Imaging Interferometer.

The four-quadrant wind imaging interferometer achieves wind field measurement by acquiring interferograms of the target scene in four distinct phase states while maintaining identical radiation intensity. This unique operational principle endows the system with notable advantages, including low sensitivity to temporal variations of the light source and exceptional compactness in instrument design. This paper proposes a step-free, four-quadrant, stepped-phase coating technique, which is applicable to an all-solid-state wind imaging interferometer scheme while offering advantages such as high reflectivity and improved stepped-phase precision for quadrants of wind imaging interferometers. Beginning with the underlying principles, we provide a detailed analysis of the four-quadrant material selection and coating architecture. This is followed by computer-aided thin-film design and simulation for verification.