Pixel Geometry, Anti-Aliasing and Projection Optics in Masked Vat Photopolymerisation: Edge Placement and Feature Fidelity

The nominal pixel pitch of a masked vat-photopolymerisation system is not its printable resolution. A commanded mask is sampled on a finite grid, transformed by pixel aperture and fill factor, projector or LCD optics, focus, magnification, distortion, angular distribution, field nonuniformity, resin transport and cure threshold. Raster orientation and neighbouring pixels alter the delivered edge. Anti-aliasing may improve mean edge placement while broadening transitions, changing local dose or erasing small negative features. A visually smoother contour is therefore not sufficient evidence of dimensional fidelity. This review defines a metrology-led framework for qualifying pixel geometry, rasterisation, anti-aliasing and projection optics. It separates the design boundary, sampled command, irradiance field, cure-state boundary and measured final edge; treats positive and negative features independently; and distinguishes sampling pitch, optical resolution, process resolution and minimum reliable feature. Point-spread and modulation-transfer measurements are combined with printed line-space, slanted-edge, corner and isolated-feature artefacts. Validation spans orientation, field position, exposure, feature neighbourhood and independent builds. No universal anti-aliasing level, pixel-to-feature ratio, optical kernel or minimum feature size is supported. The defensible result is a bounded edge-placement capability for a declared mask, optical state, resin and process.