Conference Paper

A Planar Light Probe

University of California, San Diego
DOI: 10.1109/CVPR.2006.37 Conference: Computer Vision and Pattern Recognition, 2006 IEEE Computer Society Conference on, Volume: 2
Source: DBLP


We develop a novel technique for measuring lighting that exploits the interaction of light with a set of custom BRDFs. This enables the construction of a planar light probe with certain advantages over existing methods for measuring lighting. To facilitate the construction of our light probe, we derive a new class of bi-directional reflectance functions based on the interaction of light through two planar surfaces separated by a transparent medium. Under certain assumptions and proper selection of the two surfaces, we show how to recover Fourier series coefficients of the incident lighting parameterized over the plane. The results are experimentally validated by imaging a sheet of glass with spatially varying patterns printed on either side.

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    • "Ackermann et al. [2] proposes a new technique for accurately modeling reflections on a sphere. Other methods also use either reflective spheres [12] [23] [18] or specially designed planar light probes [3] or analyze shading of known geometric objects [22]. The case of a near point light rigidly attached to a camera has been analyzed for near light photometric stereo [10] and the light fall-off effect due to distance from the light is modeled. "
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    ABSTRACT: We show that a non-isotropic near point light source rigidly attached to a camera can be calibrated using multiple images of a weakly textured planar scene. We prove that if the radiant intensity distribution (RID) of a light source is radially symmetric with respect to its dominant direction, then the shading observed on a Lambertian scene plane is bilaterally symmetric with respect to a 2D line on the plane. The symmetry axis detected in an image provides a linear constraint for estimating the dominant light axis. The light position and RID parameters can then be estimated using a linear method. Specular highlights if available can also be used for light position estimation. We also extend our method to handle non-Lambertian reflectances which we model using a biquadratic BRDF. We have evaluated our method on synthetic data quantitavely. Our experiments on real scenes show that our method works well in practice and enables light calibration without the need of a specialized hardware.
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    • "They employed a pair of reference spheres as light probes and introduced the difference sphere that can be acquired by differencing the intensities of two image regions of the reference spheres. Alldrin and Kriegman (2006) developed a planar light probe for measuring low frequencies of the lighting. Their method is based on the interaction of light through two planar surfaces separated by a transparent medium . "
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    ABSTRACT: We present a method to recover the reflectance of objects and the parameters of multiple lights using a 3D image acquired by a depth sensor and a stereo intensity pair. Experimental evaluation shows the ability to recover varying diffuse and constant specular reflectance parameters from object images, and simultaneously the locations and intensities of up to three distinct light sources.
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    ABSTRACT: Creating uniform lighting for archival-quality document acquisition remains a non-trivial problem. We propose a novel method for automatic photometric correction of non- planar documents by estimating a single, point light-source using a simple light probe. By adding a simple piece of folded white paper with a known 3D surface to a scene, we are able to extract the 3D position of a light source, auto- matically perform white balance correction, and determine areas of poor illumination. Furthermore, this method is designed with the purpose of adding it to an already im- plemented document digitization pipeline. To justify our claims, we provide an accuracy analysis of our correction technique using simulated ground-truth data which allows individual sources of error to be determined and compared. These techniques are then applied on real documents that have been acquired using a 3D scanner.
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