A High Speed Dynamic System for Scanning Reflective Surface with Rotating Polarized Filters

Abstract

Shiny materials are commonly used in traditional Asian arts. Taking an image of such objects often poses serious challenges because the intensity of specular reflection component is usually much higher than that of the diffuse reflection which could lead to image saturation. Many methods for obtaining the specular component have been developed. But these methods do not satisfy the requirements of a final image with good reflection characteristics practical enough to be used onsite. It usually requires multiple images obtained at different light source or polarization filter angle. Using this method poses other practical problems like accuracy of image registration of different layers, long data acquisition time, and high computing requirements. This paper proposes a new method for acquiring specular information in high resolution for large cultural heritage objects from a single image using dynamic polarization direction control. The main idea is implemented by allowing the polarized filters placed in front of the camera to rotate at a fixed angular speed while the object is being scanned. This study discusses both the development of new equipment for acquiring the image and the image processing algorithm. The technique was used on the site on a large Japanese sliding door panel to show how it can be implemented for acquiring images with good quality and precise image registration taken at high resolution (>500dpi).