Detecting Digital Micromirror Device Malfunctions in High-throughput Maskless Lithography

Kang, Minwook; Kang, Dong Won; Hahn, Jae Won

doi:10.3807/josk.2013.17.6.513

Cited by 2 publications

(1 citation statement)

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“…Examinations of print relation and light field intensity in these axes have been rarer as fixed optics limits the user's scope for control. In optical design, the issue of most concern in the misalignment of pixels and beam skew rather than the impact of the field on the material properties of the resin [25][26][27] . Modelling the 2D light field has been attempted by a number of groups with the strategy of superimposing a series of Gaussian profiles corresponding to each 'on' pixel in the DMD 28,29 .…”

Section: Introductionmentioning

confidence: 99%

Impact of Beam Shape on Print Accuracy in Digital Light Processing Additive Manufacture

Reid

Windmill

2024

3D Printing and Additive Manufacturing

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Photopolymerization based additive manufacturing requires selectively exposing a feedstock resin to ultraviolet light, which in digital light processing (DLP) is achieved either using a digital micromirror device or a digital mask. The minimum tolerances and resolution for a multi-layer process are separate for resolution through the z-axis, looking through the thickness of a printed part, and resolution in the xy-axes, in the plane of the printed layer. The former depends wholly on the rate of attenuation of the incident UV light through the material relative to the mechanical motion of the build layer, while the latter is determined by a 2D pattern of irradiance on the resin formed by the DMD or the digital mask. The size or the spacing of elements or pixels of this digital mask is frequently given by manufacturers as the 'resolution' of the device, however in practice the achievable resolution is first determined by the beam distribution from each pixel.The beam distribution is, as standard, modeled as a two-parameter Gaussian distribution but the key parameters of peak intensity and standard-deviation of the beam are hidden to the user and difficult to measure directly. The ability of models based on the Gaussian distribution to correctly predict the polymerization of printed features in the microscale is also typically poor.Here we demonstrate an alternative model of beam distribution based on a heavy-tailed Lorentzian model which is able to more accurately predict small build areas for both positive and negative features. We show a simple calibration method to derive the key space parameters of the beam distribution from measurements of a single-layer printed model. We propose that the standard Gaussian model is insufficient to accurately predict a print outcome as it neglects higher-order terms, such as beam skew and kurtosis, and in particular failing to account for the relatively heavy tails of the beam distribution. Our results demonstrate how the amendments to the beam distribution can avoid errors in microchannel formation, and better estimates of the true xy-axes resolution of the printer. The results can be used as the basis for voxel-based models of print solidification that allow software prediction of the photo-polymerization process.

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