A hybrid optical metrology framework integrating telecentric imaging and an optical micrometer for multi-scale geometric evaluation of aero-engine shafts

88 % the stringent operational demands of aero-engine rotary shafts present a significant metrological conflict: traditional contact methods like CMM are prohibitively slow, while single-modality optical techniques struggle to reconcile the trade-off between large measurement volumes and high resolution. This paper introduces a novel hybrid optical metrology framework that fundamentally resolves this conflict through a synergistic fusion of complementary non-contact modalities and advanced algorithms. For meter-scale axial metrology, a telecentric imaging module is coupled with a robust affine transformation-based stitching algorithm that maintains metrological integrity for distortion-free axial and hole measurements across a 1300 mm range. A key methodological innovation is our mathematical datum referencing algorithm, which computationally establishes a virtual rotation axis directly from workpiece features. This approach delivers high-accuracy runout measurements that are robust against mounting inaccuracies, a critical source of error in conventional systems. Concurrently, an optical micrometer subsystem provides high-speed, sub-micron quantification of radial dimensions and dynamic geometric tolerances. By fusing data from these complementary sensors within a single clamping operation, the system achieves synchronized evaluation of over 200 geometric parameters. Experimental validation against a metrological CMM demonstrates a high radial repeatability, with a standard deviation (σ) of 0.8 µm. The system achieves an expanded uncertainty of 1.2 µm for macro-contour profiling and ±1 µm for runout measurement. Critically, this synergistic architecture enables a full shaft inspection in 15 min, reducing the measurement cycle time by 88 % compared to a benchmark commercial system while achieving metrologically equivalent accuracy. This work therefore provides a high-efficiency, high-fidelity solution, validated by novel algorithms and a multi-sensor architecture, for the comprehensive geometric evaluation of large-scale, complex shafts, paving the way for 100 % in-line quality control in advanced manufacturing.