NIST researchers have helped develop a standard testing method for a class of 3D imaging systems called Terrestrial Laser Scanners. These scanners are increasingly becoming critical for applications such as large-scale manufacturing and assembly operations. Developed in close collaboration with the makers and users of these systems, the standard outlines testing procedures for medium-range Terrestrial Laser Scanners, which measure point-to-point distances in spaces of 2-150 meters for applications such as aircraft and ship assembly.
The new standard, ASTM E3125-17, will standardize the evaluation procedures of laser scanners and will enable direct comparisons between the performance of scanners from different manufacturers.
While a previous 2015 standard tested these scanners along only one direction, the new standard tests these scanners in their entire measurement volume. Generating millions of points of 3D data, this information yields quantitative details on the scanner’s performance, such as its accuracy and noise levels.
Traditionally, the procedures for testing these systems have varied greatly from manufacturer to manufacturer, making it hard for users to compare the results from different systems and evaluate which scanner is best for their needs. The new standard specifies a series of approximately 30 tests that can evaluate the performance of laser scanners regardless of manufacturer. The tests take a couple of hours to complete, in contrast to the day or more it previously taken for comprehensive tests.
As part of NIST’s work its Physical Measurement Laboratory produced an international performance evaluation standard. Scientists at the Engineering Physics Division (EPD) designed and constructed a calibration facility to evaluate proposed tests in a draft ASTM International standard being developed. Major manufacturers of 3D laser scanners from all over the world converged at NIST to put their scanners through their paces.
The draft standard specifying the test procedures was the product of three years of work by a standards committee led by EPD’s Bala Muralikrishnan that met biweekly. “With large volume 3D laser scanners, you basically put them in the center of the room, and they sweep across the room, producing 3D point clouds,” Muralikrishnan explains. “The only previous current standard released in 2015 for these types of instruments evaluates the instrument only along one axis.
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