Scan Accuracy Checks for the Focus

Overview

A quick way to check if your FARO Focus is scanning accurately is to scan and measure a known distance between two objects. If you have a scale bar, scan it and measure the distance between two points on the bar. If not, use an object in the surrounding scene that has two known distances, for instance the edges of a door or window frame.

If you have time, you can do more comprehensive checks to completely evaluate the full range of the Focus performance. In this article, we describe two different comprehensive methods for testing the accuracy of the Focus. The first compares scans from the Focus to a known reference system. The second does not need a known reference system. It uses two sets of scans with different orientation to check accuracy. 
 

Details

Regardless of which method you use, place target spheres or checkerboards in the scene completely around the scanner, including at the full horizontal and vertical scan-range points. Place some targets at different heights, including high and low. Avoid having most targets at the horizon or down low, as does not test the full range of the Focus.

Compare Scans to a Known Reference System

1. Set up a network of target spheres.
2. Measure the sphere center points with a FARO Laser Tracker, giving them accurate and known locations relative to each other. This creates a known reference system you can use for comparison.
3. Scan the network of spheres with the Focus and register the scans using the spheres.
4. Measure the center points of the spheres in the scans.
5. Compare this to the known known reference system.
6. Optionally, if the network of sphere center points has a level XY plane, tilt the scanner, and re-scan the network of spheres. The registration should still work well and verify the Focus inclinometer.  

Compare Scans Taken with Different Orientations

1. Set up a network of spheres or checkerboard targets.
2. Scan them with the Focus.
3. Move the scanner for at least 2 meters or 6,5 feets and rotate it.
4. Scan the target network again.
5. Register the two sets of scans together. Depending on the laser scanner that was used, the point distance should not exceed the following limits:
   Focus 3D / X / XHDR: 4mm
   Focus M70: 6mm
   Focus S70/S150/S350/Max/Premium/Core: 2mm

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