Optics: measuring and testing – Shape or surface configuration – Triangulation
Reexamination Certificate
2000-04-12
2002-12-10
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Shape or surface configuration
Triangulation
C382S154000, C250S23700G
Reexamination Certificate
active
06493095
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical 3D digitizer, a system based on the digitizer and a corresponding method for digitizing an object, for example a full human being. The present invention has numerous applications, for example for computer-assisted 3D vision, human body digitizing, computer animation, computer graphics, electronic gaming, 3D electronic archiving, 3D web, reverse engineering and medical 3D imaging.
BACKGROUND
3D digitizing, particularly non-contact optical 3D digitizing techniques, became commercially available during the recent years. Most of these techniques are based on the principle of optical triangulation. Despite the fact that passive optical triangulation (stereo vision) has been studied and used for many years for photogrametic measurements, the active optical triangulation technique (particularly laser scanning technique) gained popularity because of its robustness and simplicity to process obtained data using a computer. Most of the systems based on the active optical triangulation principle were developed for industrial applications, such as robotic assembly, robot guidance, industrial inspection, reverse engineering, etc.
As an example of such technique, a laser beam or a laser stripe is projected on a 3D surface of an object, scattering the laser beam or laser stripe on the surface. It is measured using a photo-electronic device. A signal can be generated to indicate the position (usually the depth) of the measured point. In most cases, the basic measurements are either a point or a section profile. A mechanical or optical scanning device is usually used to provide a frame of 3D measurements. For industrial applications, mechanical scanning can be accomplished by the mechanism on which the digitizing device is mounted, such as a robot or a conveyer. The scanning process consists of a sequential data acquisition process and takes a relatively longer time to scan a surface. During the scanning, the object should be kept immobilized; this is a major problem when scanning a live being. Different techniques, such as the projection of multiple stripes, laser line scanning during one video frame and high speed scanning, have been developed. These approaches are either too expensive to realize, or their sampling rate is still too low compared to 2D digital imaging.
A laser beam is a monochromatic light source. One single monochromatic laser beam can not provide full color information of the measured surface. On the other hand, a number of today's 3D applications including computer animation, electronic games, 3D web, 3D archiving and 3D medical imaging require information on color texture which contributes to most of the visual effects. In order to measure the color texture of a surface, a 3D digitizing system based on a laser scanning principle must use multiple laser sources (blue, green and red lasers) or use a second camera to get color data. The first solution is very difficult to be implemented and is also very expensive. The second can suffer from problems of misalignment between 3D geometric data and color texture data because they are not captured from the same angle of the view.
When digitizing a full human body, the required ratio between height and width of the measured zone should be 2 to 3 over 1. A system based on laser scanning is more flexible to provide a desired ratio, but its acquisition speed is too slow. All other systems using frame capturing of a CCD camera are limited by the geometric form of the sensor. Most of commercially available CCD sensors have an aspect ratio equal either to 4 or 3 over 1. If such a sensor is used to cover a human body possibly higher than 2 meters, the resulting lateral resolution would be very low. At the same time, many of the pixels are not useful for a measurement.
Known in the art are U.S. Pat. No. 3,619,033 (McMahon); U.S. Pat. No. 3,705,261 (Langley); U.S. Pat. No. 4,622,462 (Eaton et al.); U.S. Pat. No. 4,702,257 (Moriyama et al.); U.S. Pat. No. 4,775,235 (Hecker et al.); U.S. Pat. No. 4,957,369 (Antonsson); U.S. Pat. No. 5,037,207 (Tomei et al.); U.S. Pat. No. 5,198,877 (Schulz); U.S. Pat. No. 5,276,546 (Palm et al.); U.S. Pat. No. 5,313,265 (Hayes et al.); U.S. Pat. No. 5,315,512 (Roth); U.S. Pat. No. 5,377,011 (Koch); U.S. Pat. No. 5,386,124 (Yasuda et al.); U.S. Pat. No. 5,418,608 (Caimi et al.); U.S. Pat. No. 5,432,703 (Clynch et al.); U.S. Pat. No. 5,440,496 (Andersson et al.); U.S. Pat. No. 5,465,284 (Karellas); U.S. Pat. No. 5,559,712 (Kihara et al.); U.S. Pat. No. 5,630,034 (Oikawa et al.); U.S. Pat. No. 5,668,894 (Hamano et al.); U.S. Pat. No. 5,747,822 (Sinclair et al.); U.S. Pat. No. 5,804,830 (Shafir); U.S. Pat. No. 5,815,275 (Svetkoff et al.); U.S. Pat. No. 5,842,473 (Fenster et al.); U.S. Pat. No. 5,850,290 (Horiguchi et al.); 5,851,115 (Carlsson et al.); U.S. Pat. No. 5,864,640 (Miramonti et al.); U.S. Pat. No. Re. 34,566 (Ledley); and U.S. Pat. No. Re. 35,816 (Schulz). The above-mentioned patent documents provide a global idea of the state of the art.
SUMMARY
An object of the invention is to address the various weaknesses in the existing optical 3D digitizers, and to provide a reliable solution for a cost-effective system.
Another object of the invention is to provide a digitizer, a system based on such a digitizer and a digitizing method which are relatively much faster than the presently available digitizers, digitizing systems and methods.
According to the present invention, there is provided an optical 3D digitizer for digitizing an object, comprising a white light source adapted to produce white light, a projection lens optically coupled to the white light source and arranged to project the white light toward the object whereby the object has a fully illuminated side, a grating device optically coupled between the white light source and the projection lens for selectively producing a fringe pattern in the light projected by the projection lens, and first and second cameras positioned aside from the projection lens and aligned in angled directions with respect to each other so that the cameras have complementary fields of view directed on the illuminated side of the object and partially overlapping with each other over a depth of measurement of the object, the cameras having respective video outputs to produce video signals representing complementary images of the object with a common image portion as a result of the fields of view being partially overlapping.
According to the present invention, there is also provided an optical 3D digitizer system for digitizing an object, comprising the aforesaid optical 3D digitizer provided with a control circuit connected to the white light source and the grating device, and a computer including a frame grabber having inputs for receiving the video signals from the cameras, the computer having a communication link with the control circuit of the digitizer.
According to the present invention, there is also provided an optical 3D digitizing method for digitizing an object, comprising the steps of: projecting white light toward the object using a single white light source, whereby the object has a fully illuminated side; selectively producing a fringe pattern in the light projected on the object; and capturing complementary images of the object illuminated by the white light using first and second cameras positioned aside from the white light source and aligned in angled directions with respect to each other so that the cameras have complementary fields of view directed on the illuminated side of the object and partially overlapping with each other over a depth of measurement of the object, the cameras having respective video outputs to produce video signals representing the complementary images of the object with a common image portion as a result of the fields of view being partially overlapping.
The following provides a non-restrictive summary of embodiments and certain features of the invention which are described with more details hereinafter.
The optical 3D digitizer according to the invention can
Beauchamp Dominique
Bourassa Yvan
Lemelin Guylain
Song Li
Altera Law Group LLC
Inspeck Inc.
Pham Hoa Q.
LandOfFree
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