Absolute macroscopic 3-D measurements with the innovative depth-scanning fringe projection technique (DSFP)

We are presenting a new depth-scanning fringe projection technique (DSFP) o n the basis of triangulation for the absolute 3-D measurement of a macrosco pic; scene. The absolute phase can be determined for any desired depth rang e of the measurement volume. Furthermore, the known limitations of the dept h of focus occurring by light projection techniques. will be overcome. Duri ng the measurement procedure, an illuminated Ronchi grating in front of a p rojection lens is moved both in z- and x-directions by two perpendicularly arranged linear translation stages. This results in an oblique shift of the projected grating, resulting in a oblique scan of the projected fringe pat tern in the measurement volume i.e. the object space. For a well-focussed i mage acquisition, a CCD-camera placed oil the same z-stage in front of an o bservation lens takes a series of images of the scene in different z-positi ons. This focusing allows the use of large apertures and therefore a better exploitation of light. In our assembled sensor, the triangulation basis of 75 mm approximately corresponds to the distance of a person's pupils.