Large-Area Projection Stitching in Vat Photopolymerisation: Registration, Dose Overlap, Seam Formation and Qualification

Projection vat photopolymerisation can enlarge its build area by translating or multiplexing a finite optical field. Every tile boundary then becomes a coupled geometric and photochemical interface. Registration error creates steps or duplicated features; irradiance non-uniformity changes local conversion; overlap adds dose; gaps subtract dose; resin and machine drift make a calibration unstable over time. A seamless image on a calibration target is therefore not sufficient qualification evidence. This review defines qualification of large-area projection stitching. It separates stage geometry, optical distortion, radiometric response, temporal sequencing and cured-part outcome. It requires boundary-oriented artefacts, field-wide uncertainty, endurance tests and non-compensatory gates. No universal overlap width, blend function, correction map or seam tolerance is supported.