High-accuracy optical measurement of flatness for large objects

A high-accuracy non-contact optomechanical system has been designed for measuring the surface profile of relatively flat and large objects. The experimental set-up consists of a motorized gantry, a rangefinder, a CCD chip and a laser diode. This set-up permits discrete measurements to be performed on objects with a maximum plane surface area of 2.6 x 0.5 m(2) along both the X and Y axes. Experiments were carried out on carbon sandwich panels. An uncertainty of +/-8 mum has been obtained on flat and smooth surfaces; a +/-30 mum uncertainty has been determined for a rough carbon sandwich panel.