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Calibration and Certification
- Nicolas Marmet, Senior Systems Engineer

Most devices used to make measurements require calibration and can be certified to a certain standard. 3D scanners are no exception. ShapeGrabber provides both of these services to its customers and often receives questions about these subjects. In this article, I'll explain the types of calibration and certification services that we offer, as well as why, how, and how these services benefit you.

Calibration Overview 3D Scanhead Calibration System Calibration System Certification

Calibration Overview

Calibration is the process by which a measuring device is compared to an independent reference of known value, usually one which is more accurate and/or authoritative, and is then adjusted to best match the reference.

A 3D scanner is composed of multiple elements, and regular calibration of 3D scanners is necessary to ensure their accuracy. The calibration and certification of a ShapeGrabber system involves three elements:

Scanhead calibration
System calibration
System certification

With ShapeGrabber systems, the x and z coordinates are provided by the scanhead, while the rest of the system provides the y coordinate and a reference for all coordinates.

3D Scanhead Calibration

Scanhead calibration is necessary to ensure that the raw data generated by the camera-laser assembly is converted to accurate x-z coordinates. Scanhead calibration is performed in the calibration lab at the ShapeGrabber factory using specialized equipment, procedures and qualified technical staff, who:

Verify the scanhead geometry and alignment, and adjust if necessary.
Take a large number of measurements and generate compensations for always present but subtle optical and geometric imperfections.
Verify the newly calibrated scanhead with certified and NIST-traceable objects, such as gauge blocks and balls bars, and create the certificate of scanhead calibration with accuracy results.

ShapeGrabber Scanheads

We recommend recalibrating your scanhead annually to ensure accurate scan data. In fact, this is a requirement for most ISO 9000 certified organizations.

System Calibration

System calibration is necessary to properly place the scanhead (x,z) reference frame into the reference frame of the motion subsystem (y), as well as the coordinates of the index platter, if present. This is accomplished with ShapeGrabber-supplied calibration objects using the calibration wizard built-into the ShapeGrabber software. It typically requires 15 minutes to perform and is performed periodically, typically weekly, by the operator.

When ShapeGrabber first builds a new system, the calibration objects are themselves fully characterized and calibrated to yield the best possible accuracy.

On-site System Certification

Certification is the process by which a calibrated measuring device is compared to an official reference and a statement regarding the performance of the device is issued.

In order to certify the ShapeGrabber scanner for specific accuracies, it is not enough to know the scanhead accuracy, as the motion subsystem also affects accuracy. To certify the system, a series of measurements using certified objects is taken, and the resulting accuracy is calculated. ShapeGrabber offers this certification service to its customers using NIST-traceable objects in partnership with an independent ISO 17025 certified lab.

A field calibration technician travels to the customer site, typically shortly after scanhead calibration has been completed. The technician will:

Perform preventative maintenance of the structure, electronics components, motors and linear motion subsystems.
Make a series of measurements and perform adjustments to optimize the accuracy. This will optimize linearity, orthogonality and scale.
A second series of measurements is then taken to produce a certificate.

We recommend having your system certified annually, shortly after your scanhead calibration.