Metrology using Moire fringes for level change determn. - with independent camera and projector with single grid operating with shared exposure time

摘要

The procedure uses a projector (1) having a single grid (2) of small dimension whose image is projected onto a reference plane (3), and a camera (4) which records the image of the grid on a recording medium during an exposure time equal to half the normal exposure time. A second exposure of the recording medium is made in order to form a view of the object to be treated. It is placed in front of the reference plane and the image at the grid is projected onto it for an exposure time corresponding to half the normal exposure time. A normally exposed negative is thus obtained on which appear contour lines as well as the image of the grid. The projector and camera are able to be totally independent of each other. The image of objects of different cuts are recorded by variation of the distance between the projector and camera in one part and of the plane or planes of reference in the other part while keeping the same grid. The procedure is used for dimensional control of objects particularly in medicine.