Development of a topographical imaging device for the near-planar surfaces of paintings

Abstract

Paintings are versatile near-planar objects with material characteristics that vary widely. The fact that paint has a material presence is often overlooked, mostly because of the fact that we encounter many of these artworks through two dimensional reproductions. The capture of paintings in the third dimension is not only interesting for study, restoration and conservation, but it also facilitates making three dimensional reproductions through novel 3-D printing methods. These varying material characteristics of paintings are first investigated, after which an overview is given of the feasible imaging methods that can capture a painting’s color and topography. Because no imaging method is ideally suited for this task, a hybrid solution between fringe projection and stereo imaging is proposed involving two cameras and a projector. Fringe projection is aided by sparse stereo matching to serve as an image encoder. These encoded images processed by the stereo cameras then help solve the correspondence problem in stereo matching, leading to a dense and accurate topographical map, while simultaneously capturing its color. Through high-end cameras, special lenses and filters we capture a surface area of 170 cm2 with an in-plane effective resolution of 50 ?m and a depth precision of 9.2 ?m. Semi-automated positioning of the system and data stitching consequently allows for the capture of surfaces up to 1m2. The reproductive properties are conform the digitization guidelines for cultural heritage. The preliminary results of the capture of a painting by Rembrandt reveal that this system is indeed ideally suited as a topographic imaging device for the near-surface of paintings. This data can be used for making a lifelike reproduction in full dimension and full color.