Bruce R. Altschuler

Measuring Surfaces Space-Coded By A Laser-Projected Dot Matrix

We describe a mathematically-rigorous easy-to-use portable topographical mapping technique that within seconds or less can determine the heights of a surface at 16,000 (128x128) distinct sample points. The necessary data derive from (narrow-optical-bandpass) TV images of a surface which has been illuminated and space-coded by a rapid sequence of laser-projected dot patterns.

Laser Electro-Optic System For Rapid Three-Dimensional (3-D) Topographic Mapping Of Surfaces

A method is described for high-resolution remote three-dimensional mapping of an unknown and arbitrarily complex surface by rapidly determining the three-dimensional locations of M x N sample points on that surface. Digital three-dimensional (3-D) locations defining a surface are acquired by (1) optically transforming a single laser beam into an (expanded) array of M x N individual laser beams, (2) illuminating the surface of interest with this array of M x N (simultaneous) laser beams, (3) using a programmable electro-optic modulator to very rapidly switch on and off specified subsets of laser beams, thereby illuminating the surface of interest with a rapid sequence of mathematical patterns (space code), (4) image recording each of the mathematical patterns as they reflect off the surface using (a) a wavelength-specific optically filtered video camera positioned at a suitable perspective angulation and (b) appropriate image memory devices, (5) analyzing the stored im-ages to obtain the 3-D locations of each of the M x N illuminated points on the surface which are visible to the camera or imaging device, and (6) determining which of the laser beams in the array do not provide reflec-tions visible to the imaging device. Space coding of the light beams allows automatic correlation of the camera image (of the reflected spot pattern from the surface) with the projected laser beam array, thus enabling triangulation of each illuminated surface point. Whereas ordinary laser rangefinders aim and project one laser beam at a time and expect to receive one laser beam reflection (bright dot image) at a time, the pres-ent system is optical (nonmechanical and vibration-free) and can collect all the data needed for high-resolution 3-D topographic mapping (of an M x N sample of surface points) with the projection of as few as 1 + log2N light patterns. In some applications involving a rapidly changing time-dependent environment, these 1 + log2N patterns can be projected simultaneously in different wavelengths to allow virtually

Robot Vision by Encoded Light Beams

A robot eye is more than a camera and less than a complete vision understanding system. It is a device which can scan or sense objects in the three-dimensional environment and extract useful numerical information about those objects. The information obtained by the robot eye should be of a form that can be interrogated by a vision understanding system. This article describes the development of a dependable, robust, and versatile robot eye which can rapidly mensurate a surface in three dimensions. Using an active/passive camera pair, surface mensuration is achieved with fast electro-optic implementation of well-known stereophotogrammetric principles. We discuss the calibration of the robot eye and the application of the robot eye to exploring and mensurating 3-D objects.

Laser Electro-Optic System For Three-Dimensional (3D) Topographic Mensuration

Applications and system hardware are described for a new comparative topographic spatial mapping device. The device will remotely, automatically, and non-destructively measure any specified surface. A unique optical method, generates a well-defined orthogonal array of individual laser beams. Variable adjustment of beam pattern spatial frequency permits either wide-angle coverage of large-sized objects or high resolution capability for detailed areas. A novel programmable electro-optic filtering system encodes the beam array. A synchronized electro-optic selective wavelength scene capture system decodes and stores scene data in real-time in ambient light. The hardware described interfaces with suitable algorithms for the rapid calculation of the three-dimensional coordinates of sample points which mathematically define the surface of an object. The derived spatial coordinates of surface sample points then form a data base for numerically-controlled fabrication machines. A completely automated real-time scene acquisition and analysis capability could lead to machine interactive systems for pattern recognition, casting or mold comparisons, vector analysis of dimensional changes, and servo-controlled robot vision applications. The device can be ruggedly configured for use in surgical operatories, hazardous industries, outdoor inspection, etc.

Initial progress in the recording of crime scene simulations using 3D laser structured light imagery techniques for law enforcement and forensic applications

Representation of crime scenes as virtual reality 3D computer displays promises to become a useful and important tool for law enforcement evaluation and analysis, forensic identification and pathological study and archival presentation during court proceedings. Use of these methods for assessment of evidentiary materials demands complete accuracy of reproduction of the original scene, both in data collection and in its eventual virtual reality representation. The recording of spatially accurate information as soon as possible after first arrival of law enforcement personnel is advantageous for unstable or hazardous crime scenes and reduces the possibility that either inadvertent measurement error or deliberate falsification may occur or be alleged concerning processing of a scene. Detailed measurements and multimedia archiving of critical surface topographical details in a calibrated, uniform, consistent and standardized quantitative 3D coordinate method are needed. These methods would afford professional personnel in initial contact with a crime scene the means for remote, non-contacting, immediate, thorough and unequivocal documentation of the contents of the scene. Measurements of the relative and absolute global positions of object sand victims, and their dispositions within the scene before their relocation and detailed examination, could be made. Resolution must be sufficient to map both small and large objects. Equipment must be able to map regions at varied resolution as collected from different perspectives. Progress is presented in devising methods for collecting and archiving 3D spatial numerical data from crime scenes, sufficient for law enforcement needs, by remote laser structured light and video imagery. Two types of simulation studies were done. One study evaluated the potential of 3D topographic mapping and 3D telepresence using a robotic platform for explosive ordnance disassembly. The second study involved using the laser mapping system on a fixed optical bench with simulated crime scene models of the people and furniture to assess feasibility, requirements and utility of such a system for crime scene documentation and analysis.

Intra-Oral Dental Laser Grid Surface Mapping

An optical system was devised which generates a parallelopiped grid interference pattern in 3-D space. When the pattern is projected on a given surface, the surface creates a well-defined modification of the grid pattern which is recorded (by photography, electronic video imaging, etc.) for subsequent topographic analysis. The inexpensive system, designed for safety, ease of use, and versatility in a clinical environment, has been used to record intra-oral surface topography of oral structures in-vivo , as well as other concave and convex structures of health sciences interest. Two low-powered lasers are used, each generating parallel fringe patterns by reflection from thin optical wedges. The two fringe patterns generated are optically adjusted and aligned so that they are of equal spatial frequency, mutually perpendicular, coaxial, and collimated. The spatial frequency of the optically generated parallelopiped grid may be adjusted to optimize topographic measurement of a variety of subjects.

Computerized Multiangular Tomography

Radiographic diagnostic evaluation of numerous specific pathogenic entities in medicine and dentistry can be significantly enhanced through the use of recently developed mathematical data processing techniques. A method is described to non-destructively section a human organ, at any desired angle of orientation, using computer processed data derived from a series of ordinary radiographs.

Rapid 3D video/laser sensing and digital archiving with immediate on-scene feedback for 3D crime scene/mass disaster data collection and reconstruction

We describe a system for rapid and convenient video data acquisition and 3-D numerical coordinate data calculation able to provide precise 3-D topographical maps and 3-D archival data sufficient to reconstruct a 3-D virtual reality display of a crime scene or mass disaster area. Under a joint U.S. army/U.S. Air Force project with collateral U.S. Navy support, to create a 3-D surgical robotic inspection device -- a mobile, multi-sensor robotic surgical assistant to aid the surgeon in diagnosis, continual surveillance of patient condition, and robotic surgical telemedicine of combat casualties -- the technology is being perfected for remote, non-destructive, quantitative 3-D mapping of objects of varied sizes. This technology is being advanced with hyper-speed parallel video technology and compact, very fast laser electro-optics, such that the acquisition of 3-D surface map data will shortly be acquired within the time frame of conventional 2-D video. With simple field-capable calibration, and mobile or portable platforms, the crime scene investigator could set up and survey the entire crime scene, or portions of it at high resolution, with almost the simplicity and speed of video or still photography. The survey apparatus would record relative position, location, and instantly archive thousands of artifacts at the site with 3-D data points capable of creating unbiased virtual reality reconstructions, or actual physical replicas, for the investigators, prosecutors, and jury.

Image processing and 3D visualization in the interpretation of patterned injury of the skin.

The use of image processing is becoming increasingly important in the evaluation of violent crime. While much work has been done in the use of these techniques for forensic purposes outside of forensic pathology, its use in the pathologic examination of wounding has been limited. We are investigating the use of image processing in the analysis of patterned injuries and tissue damage. Our interests are currently concentrated on 1) the use of image processing techniques to aid the investigator in observing and evaluating patterned injuries in photographs, 2) measurement of the 3D shape characteristics of surface lesions, and 3) correlation of patterned injuries with deep tissue injury as a problem in 3D visualization. We are beginning investigations in data-acquisition problems for performing 3D scene reconstructions from the pathology perspective of correlating tissue injury to scene features and trace evidence localization. Our primary tool for correlation of surface injuries with deep tissue injuries has been the comparison of processed surface injury photographs with 3D reconstructions from antemortem CT and MRI data. We have developed a prototype robot for the acquisition of 3D wound and scene data.

Multiangular Tomography By Computer

Any object which is not opaque to x-ray radiation may be serially sectioned in any specified orientation (for any specified section thicknesses) without destruction,by means of internal density maps derived mathematically from the data provided by a series of ordinary radiographic images. The object must be rotated through 1800 about a given axis and radiographed at equiangular increments. Digitized intensity data obtain ed from the radiographs permit numerical analysis on a computer. The internal serial-section maps are derived by means of a suitable mathematical algorithm, and then drawn on a computer-controlled oscilloscope and photographed on microfilm. The numerical values for one set of serial-section maps (in our case, corresponding to sections perpendicular to the rotation axis) can also be stored on computer tape or disk to be later used to draw internal density maps for other desired object orientations. A single radiographic series provides all the necessary information to produce serial-section maps for any and all orientations of the object.