 Method and apparatus for a digital video cassette (DVC) decode system |
| OF THE INVENTION The invention will be described with respect to the Figures in which FIG. 1 ... |
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| Card issuing machine and a method for controlling the same |
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| Image binarization apparatus |
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Depth-from-defocus optical apparatus with invariance to surface reflectance properties
| Details |
Inventors: Sissom, Bradley; Sussman, Michael;
Assignee: Cognex Corporation (Natick, MA)
Primary Examiner: Pham; Hoa Q.
Assistant Examiner: Ratliff; Reginald A.
Attorney, Agent or Firm: Weinzimmer; Russ
A depth-from-defocus optical apparatus is provided for use with a depth-from-defocus three-dimensional imaging system for obtaining a depth image of an object. The invention facilitates the formation of depth images of objects exhibiting specular reflection, either alone or in combination with diffuse reflection, thereby allowing the application of depth-from-defocus three-dimensional imaging to objects such as microelectronic packages. The optical apparatus of the invention generally includes an illumination source, a projection lens assembly for converging rays of incident light towards an object, and a viewing lens assembly for converging rays of reflected light towards an image plane. Importantly, the viewing lens assembly is of the same working f-number as the projection lens assembly. In preferred embodiments, both the projection lens assembly and the viewing lens assembly exhibit object-side telecentricity so as to substantially eliminate vignetting of off-axis specular object features, and consequently, substantially eliminate specular false depth. The invention can also include an uncrossed polarizer/analyzer pair to balance the dynamic range of specular reflections with the dynamic range of diffuse reflections so as to effectively utilize the limited dynamic range of a single image detector. |
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DETAILED DESCRIPTION A depth-from-defocus optical apparatus is provided for use with a depth-from-defocus three-dimensional imaging system for obtaining a depth image of an object.
The optical apparatus of the invention generally includes an illumination source, a projection lens assembly for converging rays of incident light towards an object located at an object plane, a viewing lens assembly for converging rays of reflected light originating from the surface of the object towards an image plane, and a beam splitting device located so as to permit a portion of the rays of incident light to reach the object, and so as to permit a portion of the rays of reflected light to enter the viewing lens assembly.
In a preferred embodiment, the viewing lens assembly is cooperative with a single image sensor.
Importantly, the viewing lens assembly is of the same working f-number as the projection lens assembly.
In various preferred embodiments, the projection lens assembly includes an adjustable aperture stop, and/or the viewing lens assembly includes an adjustable aperture stop.
In other alternate embodiments, the viewing lens assembly and the projection lens assembly share at least one common optical element, such as one or more common lens elements.
In some preferred embodiments, the illumination source includes a light source, a condenser lens, and a periodic illumination mask.
In other preferred embodiments, the illumination source includes a light source and a condenser lens, but no structured illumination mask.
In other preferred embodiments, the projection lens assembly includes a first polarizer in a first angular orientation, and the viewing lens assembly includes a second polarizer in a second angular orientation.
Further, the first angular orientation preferably differs from the second angular orientation by a difference angle magnitude substantially different from both 90 degrees and 270 degrees.
In other embodiments, the relative orientation of the pair of polarizers is adjustable.
In further preferred embodiments, the first polarizer and the second polarizer are angularly oriented relative to each other such that a range of intensities of specular object feature reflections is substantially close to a range of intensities of diffuse object feature reflections
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Image Analysis 
