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Variable Intensity Programmable Illumination Sensor

IP.com Disclosure Number: IPCOM000047285D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 50K

Publishing Venue

IBM

Related People

Schwartz, JT: AUTHOR

Abstract

Scanning an object in space by a planar light source having varying intensity from edge to edge of the plane, and again scanning the same object by a planar light source having varying intensity from edge to edge of the plane but in the complementary direction, permits a single camera to provide the location of each point on the object's surface through computation of the intensity ratio of the reflected light occurring during the two scans. In their simplest form (Fig. 1), programmable illumination vision systems operate by projecting a single plane of light upon a body to be observed, and exploiting the fact that the intersection of this plane with a known line (direction) from an observing electronic camera K is necessarily a single known point in 3-dimensional space.

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Variable Intensity Programmable Illumination Sensor

Scanning an object in space by a planar light source having varying intensity from edge to edge of the plane, and again scanning the same object by a planar light source having varying intensity from edge to edge of the plane but in the complementary direction, permits a single camera to provide the location of each point on the object's surface through computation of the intensity ratio of the reflected light occurring during the two scans. In their simplest form (Fig. 1), programmable illumination vision systems operate by projecting a single plane of light upon a body to be observed, and exploiting the fact that the intersection of this plane with a known line (direction) from an observing electronic camera K is necessarily a single known point in 3-dimensional space. If a series of observations is taken as the illuminated plane sweeps over the whole visible portion of a scene, a digital representation of all visible body surfaces is gathered. Let H designate a geometric variable measuring distance, in the illuminated scene, perpendicular to the plane of illumination. To speed up and simplify gathering of the data, one can illuminate a scene using a specially modified beam of light upon which any observable property monotonically correlated with the previously defined geometric parameter H has been imposed. Any physical parameter of a light ray which is invariant under diffuse and/or specular reflections can be utilized. If necessary, several successive related patterns of illumination can be used to determine the parameter H. In the following realization of the general concept described in the preceding paragraph, the ratio of two intensities is used as the reflection-invariant optical parameter h. The basic device concept, which avoids all use of moving parts, is shown in Fig. 2. A beam of collimated monochromatic polarized light from source S is introduced into prism P, which must be made of an optically active material. Prism P rotates the plane of polarization in each incident ray of the beam E by an amount proportional to the distance traversed within P, the beam hence varying linearly across its width as it emerges from P. Beam E passes through an interposed electro-optical polarization rotator R, after which it undergoes partial reflection at the surface of a flat glass element G, the reflected portion being designated (E) in Fig. 1. The angle of reflection is chosen to lie near the Brewster angle for light polarized orthogonally to the plane of Fig. 1; then the intensity I of rays in the reflected beam (E) varies systematically, across the beam width, between values Imax and Imin . Beam (E) next passes through a diverging lens system (not shown) and falls upon the body whose surfaces are to be determined. By activating the pola...