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Search Publications by: Daniel S. Sawyer (Fed)

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Displaying 76 - 100 of 143

POINT REMOVAL FOR FITTING SPHERES TO 3-D LASER SCANNER DATA

November 11, 2014
Author(s)
Katharine M. Shilling, Balasubramanian Muralikrishnan, Daniel S. Sawyer
The proliferation of laser scanners in a number of industries such as the metrology of large artifacts, digitization and reverse engineering, historical preservation and archiving has led to the need for documentary Standards to establish and compare the

A Proposed Interim Check for Field Testing a Laser Trackers 3-D Length Measurement Capability Using a Calibrated Scale Bar as a Reference Artifact

October 1, 2014
Author(s)
Vincent D. Lee, Christopher J. Blackburn, Balasubramanian Muralikrishnan, Daniel S. Sawyer, Mark Meuret, Aaron Hudlemeyer
This paper describes a proposed interim check for field testing a laser tracker’s 3-D length measurement capability using a calibrated scale bar as a reference artifact. The tests described here are constructed to be sensitive to uncompensated errors in

EVALUATION OF A LASER SCANNER FOR LARGE VOLUME COORDINATE METROLOGY - A COMPARISON OF RESULTS BEFORE AND AFTER FACTORY CALIBRATION

October 1, 2014
Author(s)
Massimiliano Ferrucci, Bala Muralikrishnan, Daniel S. Sawyer, Steven D. Phillips, Peter Petrov, Yuri Yakovlev, Andrey Astrelin, Spike Milligan, John Palmateer
Large volume laser scanners are increasingly being used for a variety of dimensional metrology applications. Methods to evaluate the performance of these scanners are still under development and there are currently no documentary standards available. This

Common-Path Method for Laser Tracker Ranging Calibration

March 31, 2014
Author(s)
Christopher J. Blackburn, Daniel S. Sawyer, Craig M. Shakarji
We present an alternative to the back-to-back method of testing laser tracker ranging systems. Our approach uses a common air path for both the measurement and reference laser beams. This technique allows for more accurate determination of the reference

Ranging Performance Evaluation of a Laser Scanner

October 20, 2013
Author(s)
Massimiliano M. Ferrucci, Balasubramanian Muralikrishnan, Christopher J. Blackburn, Daniel S. Sawyer, Steven D. Phillips, Vincent D. Lee, Peter Petrov, Yuri Yakovlev, Andrey Astrelin, Spike Milligan, John Palmateer
Large volume laser scanners are used for a variety of purposes, including dimensional metrology of large artifacts, digitization and reverse engineering, as well as historical preservation and archiving. In evaluating the performance of laser scanners, we

VOLUMETRIC PERFORMANCE EVALUATION OF A LASER SCANNER

October 20, 2013
Author(s)
Balasubramanian Muralikrishnan, Massimiliano M. Ferrucci, Daniel S. Sawyer, Grant Gerner, Vincent D. Lee, Christopher J. Blackburn, Steven D. Phillips, Peter Petrov, Yuri Yakovlev, Andrey Astrelin, Spike Milligan, John Palmateer
There are several sources of error in a laser scanner measurement. The optical and material properties of the target, the shape, form, surface texture, color, reflectivity, and orientation of the target in space, environmental effects, etc., all contribute

Standard Reference Materials for Medical CT

June 27, 2013
Author(s)
Zachary H. Levine, Huaiyu H. Chen-Mayer, Adam L. Pintar, Daniel S. Sawyer
NIST Standard Reference Materials 2087 and 2088 for medical computed tomography (CT) have become available. The materials allow CT reconstructions to be tied to the International System of Units in length, density, and mass attenuation coefficient.

Assessing Ranging Errors as a Function of Azimuth in Laser Trackers and Tracers

April 18, 2013
Author(s)
Balasubramanian Muralikrishnan, Vincent D. Lee, Christopher J. Blackburn, Daniel S. Sawyer, Steven D. Phillips, Wei Ren, Ben Hughes
Tilt and radial error motion of a laser tracker head as it spins about the two axes results in small but measurable ranging and angle errors. The laser tracer, on the other hand, measures range with respect to the center of a high quality stationary sphere

A Model for Geometry-Dependent Errors in Length Artifacts

September 27, 2012
Author(s)
Daniel S. Sawyer, Brian Parry, Christopher J. Blackburn, Balasubramanian Muralikrishnan, Steven D. Phillips
We present a detailed model of dimensional changes in long length artifacts, such as step gauges and ball bars, due to bending under gravity. The comprehensive model is based on evaluation of the gauge points relative to the neutral bending surface. It

Measuring Scale Errors in a Laser Tracker s Horizontal Angle Encoder through Simple Length Measurement and Two-face System Tests

November 1, 2010
Author(s)
Balasubramanian Muralikrishnan, Christopher J. Blackburn, Daniel S. Sawyer, Steven D. Phillips, Robert Bridges, Quan Ma
We describe a method to estimate the scale errors in the horizontal angle encoder of a laser tracker in this paper. The method does not require expensive instrumentation such as a rotary stage or even a calibrated artifact. An uncalibrated but stable

Choosing test positions for laser tracker evaluation and future Standards development

July 15, 2010
Author(s)
Balasubramanian Muralikrishnan, Daniel S. Sawyer, Christopher J. Blackburn, Steven D. Phillips, Craig M. Shakarji, Ed Morse, Robert Bridges
A working group within the ISO TC 213 committee is developing a draft document [11] for evaluating the performance of laser trackers. The ASME B89.4.19 Standard [1] and the draft VDI/VDE 2617 part 10 [2] describe some useful tests that are incorporated

ASME B89.4.19 Performance Evaluation Tests and Geometric Misalignments in Laser Trackers

January 30, 2009
Author(s)
Balasubramanian Muralikrishnan, Daniel S. Sawyer, Christopher J. Blackburn, Steven D. Phillips, Bruce R. Borchardt, William T. Estler
Small and unintended offsets, tilts, and eccentricity of the mechanical and optical components in laser trackers introduce systematic errors in the measured spherical coordinates (angles and range readings), and possibly in the calculated lengths of