Acquiring spatially varying appearance of printed holographic surfaces

Abstract

We present two novel and complimentary approaches to measure diffraction effects in commonly found planar spatially varying holographic surfaces. Such surfaces are increasingly found in various decorative materials such as gift bags, holographic papers, clothing and security holograms, and produce impressive visual effects that have not been previously acquired for realistic rendering. Such holographic surfaces are usually manufactured with one dimensional diffraction gratings that are varying in periodicity and orientation over an entire sample in order to produce a wide range of diffraction effects such as gradients and kinematic (rotational) effects. Our proposed methods estimate these two parameters and allow an accurate reproduction of these effects in real-time. The first method simply uses a point light source to recover both the grating periodicity and orientation in the case of regular and stochastic textures. Under the assumption that the sample is made of the same repeated diffractive tile, good results can be obtained using just one to five photographs on a wide range of samples. The second method is based on polarization imaging and enables an independent high resolution measurement of the grating orientation and relative periodicity at each surface point. The method requires a minimum of four photographs for accurate results, does not assume repetition of an exemplar tile, and can even reveal minor fabrication defects. We present point light source renderings with both approaches that qualitatively match photographs, as well as real-time renderings under complex environmental illumination.

Polarization mapping

“…Both in computer vision and computer graphics, polarimetric imaging has been used for a while to study material properties, such as classifying material as dieletic or metals [8] or estimating reflectance properties [9,10]. Related to this, the work by Toisul and Dhillon [11] uses a polarization based method to capture the appearance of printed holographic surfaces.…”

“…As RCP and LCP are indistinguishable, we assume our filter behaves like a RCP to calculate V . If it does not, the only difference is the sign in V , which does not limit the filters that can be applied (see Equations ( 4) and (11)).…”