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Pulsed UV laser irradiation alters the physical and chemical properties of polymer surfaces.1,2 These property changes have a dominant effect on the production of texture in laser-etched polymers. The chemical and physical nature of the laser-modified surface of polyethylene terephthalate) (PET) has been studied by infrared spectroscopy in the work reported here. These studies show that chemical and physical modification occurs in distinctly different power regions. When the infrared absorption intensities of the laser-modified PET are monitored as a function of depth in the polymer, the depth profile of the physical and chemical changes has also been measured. These measurements will be related to excimer laser texturing of semicrystalline polymers.

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The reflectance function of a scene point captures the appearance of that point as a function of lighting direction. We present an approach to printing the reflectance functions of an object or scene so that its appearance is modified correctly as a function of the lighting conditions when viewing the print. For example, such a “photograph” of a statue printed with our approach appears to cast shadows to the right when the “photograph” is illuminated from the left. Viewing the same print with lighting from the right will cause the statue's shadows to be cast to the left. Beyond shadows, all effects due to the lighting variation, such as Lambertian shading, specularity, and inter-reflection can be reproduced. We achieve this ability by geometrically and photometrically controlling specular highlights on the surface of the print. For a particular viewpoint, arbitrary reflectance functions can be built up at each pixel by controlling only the specular highlights and avoiding significant diffuse reflections. Our initial binary prototype uses halftoning to approximate continuous grayscale reflectance functions.

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