Skip to main content
                     
As-Built As-Built - Revit As-Built - AutoCAD VirtuSurv - VirtuSurv 2018 As-Built - Modeler VirtuSurv - VirtuSurv 2019          
BuildIT BuildIT - Projector BuildIT - Construction BuildIT - Metrology              
CAM2 CAM2 - SmartInspect CAM2 - 2018 CAM2 - Measure 10 CAM2 - Measure Q CAM2 - Measure X CAM2 - Measure 3/4 CAM2 - AnthroCAM CAM2 - 2019 CAM2 - 2020 CAM2 - 2021
Cobalt 3D Imager 3D Imager - Cobalt                  
Cobalt Design Cobalt Design - M Cobalt Design - S Cobalt Design - Dual              
Computers Computers - All Computers                  
FARO Aras 360 & CAD Zone FARO CAD Zone - Fire & Insurance FARO CAD Zone - Crime & Crash FARO CAD Zone - CZ Point Cloud FARO CAD Zone - First Look Pro FARO 360 - Reality FARO 360 - HD FARO 360 - Blitz FARO 360 - Genius    
FARO Zone present4D - present4D                  
FARO Zone 2D FARO Zone 2D - 2018 FARO Zone 2D - 2019 FARO Zone 2D - 2020 FARO Zone 2D - 2021            
FARO Zone 3D FARO Zone 3D - 2018 FARO Zone 3D - 2019 FARO Zone 3D - 2020 FARO Zone 3D - 2021            
FARO Zone 3D Advanced FARO Zone 3D Advanced - 2018 FARO Zone 3D Advanced - 2019 FARO Zone 3D Advanced - 2020 FARO Zone 3D Advanced - 2021            
FaroArm/ScanArm FaroArm/ScanArm - Quantum S FaroArm/ScanArm - Quantum M FaroArm/ScanArm - Quantum E FaroArm/ScanArm - Edge FaroArm/ScanArm - Fusion FaroArm/ScanArm - Prime FaroArm/ScanArm - Platinum FaroArm/ScanArm - Legacy Quantum FaroArm/ScanArm - Titanium FaroArm/ScanArm - Advantage
FaroArm/ScanArm FaroArm/ScanArm - Digital Template FaroArm/ScanArm - Gage FaroArm/ScanArm - Quantum S Max FaroArm/ScanArm - Quantum M Max FaroArm/ScanArm - Quantum E Max FaroArm/ScanArm - Gage Max        
Hand Held Scanner 2D Hand Held Scanner - ScanPlan 3D Hand Held Scanner - Freestyle3D 3D Hand Held Scanner - Freestyle3D X 3D Hand Held Scanner - Freestyle3D Objects 3D Hand Held Scanner - Freestyle 2          
Language Quality HT MT AT NT INT - Internal Sales - Internal Resources Sales - Order and Quote Sales - Product Info Sales - Sales Readiness Sales - Training
Language Quality CS - Procedures and Product Sales - Product Launch Sales - Promotions CS - Quote to Invoice CS - Phone System CS - New Hire Training CS - General CS - FARONow New User CS - Salesforce Settings CS - Product Info
Language Quality CS - Licensing                  
Languages Language - English Language - Japanese Language - German Language - Chinese Language - Spanish Language - Italian Language - Portuguese Language - French    
Laser Projector RayTracer - RayTracer Laser Projector - Tracer M Laser Projector - Tracer SI              
Laser Radar Imaging Laser Radar - VectorRI                  
Laser Scanner 3D Laser Scanner - Focus S 3D Laser Scanner - Focus M 3D Laser Scanner - Focus3D 3D Laser Scanner - Focus3D X 3D Laser Scanner - Focus3D X HDR 3D Laser Scanner - Focus3D S 3D Laser Scanner - Photon 3D Laser Scanner - Focus S Plus 3D Laser Scanner - Swift  
Laser Tracker Laser Tracker - Vantage Laser Tracker - ION Laser Tracker - Vantage S Laser Tracker - Si Laser Tracker - X Laser Tracker - Xi Laser Tracker - Vantage E Laser Tracker - Vantage S6 Laser Tracker - Vantage E6  
Legacy Gage Legacy Gage - Bluetooth Legacy Gage - Plus Legacy Gage - Standard Legacy Gage - Power            
Legacy Software Legacy Software - CAM2 Gage Legacy Software - Gage Software Legacy Software - Insight              
PointSense PointSense - Basic PointSense - Pro PointSense - Building PointSense - Plant PointSense - Heritage PointSense - Revit CAD Plugin - TachyCAD Building CAD Plugin - TachyCAD Archeology CAD Plugin - TachyCAD Interior CAD Plugin - PhoToPlan Basic
PointSense CAD Plugin - PhoToPlan CAD Plugin - PhoToPlan Pro CAD Plugin - PhoToPlan Ultimate CAD Plugin - DisToPlan CAD Plugin - MonuMap CAD Plugin - hylasFM CAD Plugin - VirtuSurv      
RevEng RevEng - RevEng                  
ScanArm ScanArm - Design ScanArm 2.0 ScanArm - Design ScanArm ScanArm - Forensic ScanArm ScanArm - Design ScanArm 2.5C            
SCENE SCENE - Capture and Process SCENE - WebShare Server and 2Go SCENE - WebShare 2Go App SCENE - 2018 SCENE - 7.x SCENE - 6.x SCENE - 5.x SCENE - 4.x SCENE - LT SCENE - 2019
SCENE SCENE - 2go App SCENE - 2020 SCENE - 2021              
Serial FaroArm Serial FaroArm - Silver Serial FaroArm - Gold Serial FaroArm - Bronze              
Visual Inspect Visual Inspect - App Visual Inspect - CAD Translator                
WebShare WebShare - Enterprise WebShare - WebShare Cloud                

BuildIT

Projector

FARO® Knowledge Base

Setting up Projectors for Coverage and Accuracy

Overview

There are many, many factors that should be considered to get the most coverage with the fewest projectors while achieving the desired accuracy. This article goes through each of these factors in increasing level of complexity, with examples and links to helpful articles on related BuildIT Projector capabilities. 

Standoff distance

The apex of the projected beam has an angle of 60 degrees. Imagine you want to project on the ground, straight down, and wanted to know how wide the coverage is at 5 meters. To be precise, we can use trigonometry to get:

5m * tan(30 deg) * 2 = 5.77m
Proj_down.png

If you don’t have a scientific calculator nearby, 2*tan(30 deg) is about 1 so you can rely on this rule of thumb: The side of the projected square is about as long as the stand-off distance.

Whatever size the part is, try to get that standoff distance to get full coverage with just one projector.

If you can place the projector rigidly (minimal vibrations, like on an I-beam) directly above the workspace that would be ideal. However, whether it is due to ceiling height or lack of mounting points that are available, you may not have that luxury. Often, you will need to project at an angle instead.

Projecting at an Angle

In many cases the setup must project from the side. This allows you to get more coverage, where instead of projecting a ~ 5x5 square, we project a trapezoid with much wider sides at the same 5m height, as seen in this view.
Proj_20degdown.png

If you need additional coverage area, remember that you can also rotate the projector.
Proj_20degdownand45twist.png

Otherwise, if all projections fit within the FOV and range, and from its vantage point it has line of sight for all projections, then your next preoccupation should be accuracy. In the above example, we have drastically increased the distance and incidence angle at the far ends of the coverage area. While this might be a good solution for projecting on to a shaft or long beam, steep angles and long distances reduce accuracy. We must convert the angular accuracy at a given distance, to a projection accuracy for a given grazing angle.

If your environment does not allow you to place the unit far enough from the surface to get full coverage and maintain desired accuracy, then you will need additional projectors.

Accuracy Over Distance

The projector is an angular device, so all inaccuracies are angular. Convert an angular inaccuracy to linear one, and you obtain a distance value that grows over the range of the projection.

The accuracy of TracerM and TracerSI is specified as 0.25mm at 4.6m range. That range is the distance at which we certify our units.

As a rule of thumb, linear error increases proportionally to distance. So, at double the distance (9.2m) you get 0.5mm.

Error Magnification by Angle of Incidence

Double distance will double linear error, but this is a projection device and you need to account for the projection plane and the angle of incidence, which magnifies the error.

AngleofIncidence.png

The error magnified becomes:

linear error / cos(angle of incidence)

So, for example, if the laser beam hits a surface at an incident angle of 30 degrees, 1/cos(30) = 2, which is to say that the error is double what it would be if the beam were perpendicular (90 degrees) to the surface.

Error Due to As-Built Differences

There is yet another source of error, which is caused by the difference between whether the projection surface is expected to be (according to CAD), and where it is in reality (referred to as "as-built"). Since the projector is not a measurement device and is unable to determine the as-built surfaces, there is no way of predicting what the error will be. There is no equation for it.

However, the impact of as-built differences can be mitigated by limiting the angle of incidence of your projection. In the image below, there are two rays aiming at the same point on the CAD with different angles of incidence: The green one, and the red one. Because they land on the as-built surface, they land at different places. The ray with the largest angle of incidence (red) falls much further than the other one (green).
CADvsAsbuilt.png

A rule of thumb is to limit the angle to 45 degrees, though for the applications that require highest accuracy it may be limited to 30 degrees.

Max. angle of incidence setting.png

Any projection that cannot be projected with a low enough angle of incidence will be disabled, and shown as a grey dotted line with arrows showing the local surface' normal direction.

Angle of Incidence simulation.png 

Learn more about how to find the optimal projector setup using BuildIT in this article: Simulate Projection Plans in BuildIT Projector

Multiple Sessions per Projector

For very long parts, multiple projectors are required to project its full length like so:
ProjectorAngle20-2Projectorsv-1part.png

Keep in mind that a projector can run multiple sessions simultaneously. And so, if two parts fit in that projection space, then they can be assembled simultaneously, allowing you to double your productivity with the same set of projectors:
ProjectorAngle20-2Projectorsv-2parts.png

Alignment Point Accuracy

One last consideration, but not the least, once you have a setup where the projector can realistically provide the coverage and accuracies desired, it is critical that the alignment points are as accurate as possible. Projections cannot be more accurate than the alignment points.

Generally speaking, if you want an accuracy of 1 millimeter you would want the alignment RMS to be no more than one millimeter.

 

  • Was this article helpful?