Fast Normal Map Acquisition Using an LCD Screen Emitting Gradient Patterns

Abstract

We propose an efficient technique for normal map acquisition, using a cheap and easy to build setup. Our setup consists solely of off-the-shelf components, such as an LCD screen, a digital camera and a linear polarizer filter. The LCD screen is employed as a linearly polarized light source emitting gradient patterns, whereas the digital camera is used to capture the incident illumination reflected off the scanned object's surface. Also, by exploiting the fact that light emitted by an LCD screen has the property of being linearly polarized, we use the filter to surpress any specular highlights. Based on the observed Lambertian reflection of only four different light patterns, we are able to obtain a detailed normal map of the scanned surface. Overall, our techniques produces convincing results, even on weak specular materials.

Screen-Camera Calibration Using Gray Codes

“…Another category of popular new applications are shape acquisition methods, where the screen is used as a planar illuminant, while the camera captures the illuminated scene. For example, methods using a screen-camera setup have been invented for the purpose of photometric stereo [5,12,11], specular surface acquisition [9,23,27], environment matting [29], and many more applications [17,22,19]. The attractive feature that all these techniques have in common, is the fact that a cheap setup consisting only of off-the-shelf components can often replace otherwise expensive hardware setups, while still producing comparable results.…”

“…We distinguish between geometric and radiometric calibration. While geometric calibration tries to find the position and orientation of the screen(s) with respect to the camera [27,2,10,12], radiometric calibration establishes the relation between the light emitted by the screen and the light received by the camera [28,11]. In this work, we will focus on geometric calibration.…”

Photometric approach to surface reconstruction of artist paintings

“…Atkinson and Hancock 27 presented a shape-recovery technique that uses polarization information and the Fresnel theory. Francken et al 28 proposed a technique for surface normal acquisition by using an LCD screen as a polarized light source. Chen et al 29 proposed an active 3-D scanning method using a modulated phase-shifting technique.…”

Display-camera calibration using eye reflections and geometry constraints

“…Photometric stereo methods have been proposed to estimate the shape of lambertian [11,21,52] objects. PC monitor illumination is not directed and focused and is therefore ideal for coping with partially lambertian [20] or non-lambertian objects [29]. Shape reconstruction methods for specular objects [58,7,17,44] identify display-camera correspondences and estimate the respective surface normals.…”

“…Geometric calibration determines the internal camera parameters as well as the external display pose with respect to the camera [7,21,19,58]. Radiometric calibration establishes the relation between the light emitted by the display and the light measured by the camera [58,21,20].…”