High accuracy contouring using grating projection

The projection grating technique is a well-known method to obtain contouring information. However, when high accuracy is required the grating projection technique and the corresponding shadow moiré method pose problems that must be dealt with. In this paper some of these problems are outlined and solutions to overcome the limitations arising from the use of particular mathematical models for fringe data interpretation are proposed. Examples of application are given and it is shown that very good agreement is obtained between the optical results and measurements made by Coordinate Measuring Machines (CMM's).