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Structured Highlight Method:
This device has 128 point sources distributed over a hemisphere. Each source is created using an LED and an optical fiber. Binary coding is used to scan the 128 sources using just seven patterns. The seven captured images are then used to compute the surface normals of the object.
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The SHINY System:
The structure highlight method was used by Westinghouse Corporation in 1987 to develop the SHINY (Structured Highlight Inspection System) that was used to inspect solder joints on surface-mount circuit boards.
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Photosampler:
This device uses a set of point light sources placed at the vertices of a tessellated sphere. A spherical diffuser is placed between the point sources and the object of interest to convert the point sources into extended sources. The object of interest is placed at the center of the diffuser and its images are captured while the sources are scanned. This set of images is used to compute the surface normal and the reflectance for each point on the object.
(An example result can be seen in the picture at the top of this page).
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Diffuse Interreflections:
This image of a set of concave Lambertian objects shows the effects of interreflections. Once can see the increase in brightness close to concave edges that results from multiple reflections of light between surface points that are visible to each other. Shape from brightness methods will produce erroneous results if interreflections are ignored.
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The Pseudo Shape of a Concave Lambertian Object:
Due to interreflections, a concave Lambertian object of given shape and albedo function behaves like an Lambertian object without interreflections but with a different shape and albedo function. This table shows a few examples of actual and pseudo shapes. In all cases the pseudo shape is shallower than the actual shape.
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Actual Surface from Pseudo Surface (2D):
This picture shows shape and reflectance recovery results for two objects with translational symmetry. In each case, the pseudo shape and reflectance were measured using traditional photometric stereo. The actual shape and reflectance were then recovered from the pseudo ones using a recovery algorithm that is based on an interreflection model.
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Actual Surface from Pseudo Surface (3D):
Recovery results for a 3D object. The strong interreflections between the three faces of the inverted pyramid cause the measured pseudo shape to be much shallower than the actual shape.
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