3-D optical profilometry at micron scale with multi-frequency fringe projection using modified fibre optic Lloyd’s mirror technique

•A new flexible fringe projection system is introduced for 3D profilometry.•It is capable to be applicable at the micron scale.•Allows the fringe frequency to be easily adjustable.•It has no resolution limitations and is nonsensitive to external factors.•It allows discontinuous surface measurements by changing the fringe frequency.