3D Laser Scanning Defined

By Sal Spada

Industry Trends

3D Laser Scanners use non-contact technology that senses the shape of an object through the use of laser light or structured light. Software transforms the data collected by the hardware into an accurate, digitalized 3D representation of the object.

How Does 3D Laser Scanners Work?

The laser scanner shoots a pulse of laser light at an object and accurately measures the direction. It also senses the reflected light and determines the distance traveled. The combination of direction and distance is used to calculate its X, Y, and Z coordinates for the point on the surface struck by the laser pulse. A 3D laser scanner can measure several thousand points per second along the surface. This set of X, Y and Z points is a digital Laser Scanner Source: Leica Geosyste ms : 3D Scanning Global Market Research Study 20 • Copyright 2015 © ARC Advisory Group • ARCweb.com • For Internal Use Only representation of the object’s surface called a “point cloud.” This is analogous to the pointillism by neo-impressionism artist Georges Seurat but put into three dimensions. 3d laser scanner

To capture the various sides of an object, there are two approaches: 1) For smaller items, move the object by placing it on a rotary table, or 2) Move the scanner either via a coordinate measuring machine (CMM) arm (for smaller items), or changing the scanner station’s location and combining several point clouds. The point cloud becomes a 3D model of the surface of the object.

To combine point clouds, a process is needed to ensure the point clouds are accurately located relative to each other. This is done with either shared registration points within each point cloud or the scanner’s GPS location when each point cloud was generated. For as-built plant documentation needing high accuracy, shared registration points (at least three) for each pair of point clouds are required. For applications like land surveys, the scanner’s GPS location will often suffice.

How does Structured Light Work?

Though structured light has seen prolific use by consumers around the globe through the Kinect gaming device for the Xbox console, industrial usage of the technology was, until recently, mostly confined to the European market. Structured light 3D scanners, also known as white light scanners, function by projecting a pattern of light onto a 3D object. A camera looks at the deformation of this light pattern on the object and calculates the distance of every point in its field of view, creating a point cloud.

Hardware for Point Cloud Data Acquisition

Scanner hardware generates the laser pulse or light projection, interprets the reflection, and records the results. Included are the laser beam and light Laser Scanner with Detail of Laser Emitter and Mirror for Scanning Source: FARO Technologies Inc. Point Cloud with Detail of Points Source: Leica Geosystems 3D Scanning Global Market Research Study Copyright 2015 © ARC Advisory Group • ARCweb.com • For Internal Use Only • 21 emitting and receiving devices. The study includes equipment that collects a minimum of 10,000 points per second. It does not include tools for taking single point-to-point measurements.

The market is segmented into three categories by range. They are:

Short range

Typically applied to objects under a meter in any dimension, but some can go up to three meters. They are highly accurate to micro meters. Applications include product design and reverse engineering in the discrete industries. For CMM machines, only the probe is included and not the entire coordinate measurement machine.

Medium range

Usually applied at about 50 meters but can go up to 300 meters. Often used in civil engineering. One type of application measures “as-built” conditions of equipment in a process plant for the design of a modification with accuracy within ±¼”.

Long range

Typically has a range up to 2,000 meters.

Software for Point Cloud Presentation and Manipulation

Output from the scanner becomes input into software applications to obtain value from the point cloud.

Point cloud rendering

This software provides for human-readable visualization, interpretation, and analysis of the point cloud. This software may include features for measurement (like calculating the distance between points) or enhancements (like filling-in the gaps between the points for a 3D solid model). This software may also include point cloud management for combining multiple point clouds.

Design support plug-in

This software imports the point cloud into a CAD design application. The point cloud is compared with the CAD objects to identify interferences or gaps. For industrial applications, this is particularly useful for planning and execution of plant upgrades, modifications and turnarounds. For changes to existing facilities, the “asbuilt” data from a laser scan ensures representation of the real-world environment. The specific software for importing a point cloud is included in this study’s scope.

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