On axis fringe projection: A new method for shape measurement

• We present a new method for shape measurement using an on axis fringe projection.
• The system presents sensitivity due to divergent projection.
• We validate the results with the ones obtained with a coordinate measuring machine.
• The method has the advantage that reduces the shadows problems in fringe projection.
• The method has the advantage that the phase difference is not wrapped.

The traditional fringe projection technique requires a non-zero angle between projection and observation directions to have sensitivity in the z direction. In this work, a new method for shape measurement using fringe projection is presented. In our case, the angle between projection and observation directions is zero, but the system presents sensitivity due to divergent projection which changes the fringes frequency in each one of the normal planes to z-axis. The accuracy of the new method proposed here is validated with real measurements obtained with a coordinate measuring machine (CMM) and compared with the standard fringe projection technique. Finally, we discuss the advantages of the new method.