Manufacturing Metrology Team

Calibration of fringe projection for form measurement

Duration: October 2017 – October 2021
Student: George Gayton
Supervisors: Richard Leach, Rong Su
Funding: EPSRC and Manufacturing Technology Centre

Fringe projection is an optical measurement technique that captures a 3D scene and converts it into a cloud of 3D coordinates – a point cloud. Fringe projection works using only a projector and a camera. The projector projects an image onto the surface of interest, and a camera, displaced and rotated from the projector, records the image. The projected image, typically a periodic pattern, is distorted due to the varying height of the surface from a reference plane. This image distortion is the measurement principle that allows the measurement of the surface profile. A significant hurdle limiting the use of fringe projection systems from gaining popularity is the measurement so far is not traceable; the measurement result cannot be related to a reference through a documented unbroken chain of calibration. 

To calibrate the measurement, the measurement model must be expanded to include all of the significant factors that affect the measurement principle and instrument. These factors shall be investigated using a physical measurement system and a simulated twin. The simulation will be based on ray tracing and results will be validated on the physical system. The aim is to build a comprehensive list of influence factors and their corresponding sensitivity coefficients to create a measurement model that is capable of accurately predicting measurement outcomes, and therefore estimating uncertainty.

Calibration of fringe projection for form measurement_1
Fig. 1 A measurement in action.


Calibration of fringe projection for form measurement_2
Fig 2. The corresponding point cloud.


Manufacturing Metrology Team

Room B38 Advanced Manufacturing Building
Jubilee Campus
Wollaton Road
Nottingham, NG8 1BB