S. Kaveh Hedayati | Searcharxiv

arXiv2025

Upscaling Tomographic Volumetric 3D Printing via Virtual Stitching of Coordinated Projections

Tomographic volumetric 3D printing offers layer free, rapid fabrication of objects with high design freedom, but is limited to relatively small curing volumes because of the optical constraints imposed by an assumed need for telecentricity. We present a method to virtually stitch multiple projections from different light sources to build a single workpiece. To avoid the built in requirement for telecentricity and thus the need for an index matching vat, projections are produced by a graphics processing unit accelerated raytracing solver. The method accounts for non ideal light propagation, including nontelecentricity, reflection, refraction, attenuation, as well as any output power mismatch among projectors.Tomographic volumetric 3D printing offers layer free, rapid fabrication of objects with high design freedom, but is limited to relatively small curing volumes because of the optical constraints imposed by an assumed need for telecentricity. We present a method to virtually stitch multiple projections from different light sources to build a single workpiece. To avoid the built in requirement for telecentricity and thus the need for an index matching vat, projections are produced by a graphics processing unit accelerated raytracing solver. The method accounts for non ideal light propagation, including nontelecentricity, reflection, refraction, attenuation, as well as any output power mismatch among projectors.

physics.optics↗

arXiv2025

Lateral Contrast Enhancement in Tomographic Volumetric 3D-Printing via Binary Photoinhibition

Tomographic volumetric 3D-printing (TVP) utilizes a nonlinear photoresponse of polymer precursor to cure all points in a three-dimensional (3D) object in parallel. A key challenge in TVP is to build up dose contrast between in-part and out-of-part points in a lateral plane, which relies on coordinated illumination from various projecting angles. This challenge has mainly been tackled by projection optimization. Here we show that designing material responses to photo-excitation can be a more effective way of addressing this challenge. By introducing a secondary photo-inhibitory species that reacts to external ultraviolet (UV) stimulus, we create a binary photoinhibition (BPI) system that greatly enhances the achievable dose contrast in a lateral plane. We first show that, in theory, combining dose subtraction with sufficient projection angles can guarantee an exact mathematical reconstruction of any greyscale design. We then propose a theoretical framework for BPI, in which a single stationary state with swappable stability can be used to realize dose subtraction. We use oxygen-lophyl radical pair as an approximation to show improvements in print quality enabled by enhanced dose contrast. In situ shadowgraphy shows that BPI improves the lateral patterning with various geometric features, creating differentiable changes in refractive index within 54 um or less. We show qualitative improvements in surface features and internal hollowness in physical prints. The direct impacts of UV light on the formation of positive and negative features on vertical and lateral planes of 5 workpieces are analyzed quantitatively. We conclude that introducing BPI with UV irradiation grants us direct control over the formation of negative features on the lateral plane.

physics.optics↗