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Anti-aliasing and Image Blur

The principle of LCD-based stereolithographic technology is to display sliced images on the LCD screen, and use an UV light source to irradiate the LCD screen vertically. The photosensitive resin will be cured and solided under the irradiation of ultraviolet light transmitted through the LCD screen, and then cured layer by layer to complete the printing of the 3D model.

Schematic diagram of LCD-SLA light source

The display of the LCD screen is realized by controlling the light transmittance of the liquid crystal array, so the displayed image is a discrete grid. Generally, the area where the model sliced is white, and the non-sliced ​​area is black. Therefore, it is easy to print the slices with vertical or horizontal lines, because when the pixels are placed side by side, they will be perfectly aligned and the cured model is also a straight line. However, when displaying arcs and diagonal lines, the edge situation is the intersection of black and white pixels. The edges of the solidified slices are interlaced voxels, and the surface of the model shows layered patterns

Slice view of models

From the left picture above, we could find that the edges of the model are smooth and non-jaggy when sliced ​​horizontally and vertically. The diagonal and arc lines of the slice on the right have obvious jagged edges.

Rendering model(left) and real photo(right)

The picture above is a complex model file. The head of the model is an oval. But after the slice file is represented by pixels, the edges appear irregular jagged. From the real photo of the model, we could see that the surface of the model is not smooth, with obvious jagged and layered patterns.

Studies have shown that by controlling the brightness of each pixel, the size of the solidified voxel at the corresponding position can be controlled, and the half-voxel solidified at the corresponding position of a gray pixel will merge into adjacent voxels. Therefore, we have studied anti-aliasing and image blurring algorithms to achieve the transition of the gray value of the slice edge and improve the surface accuracy of the printed model.