scope:

The present guideline is applicable to optical 3D measuring systems based on area scanning which operate on the triangulation principle and determine the object to be measured from several different images. The measuring systems can be configured so that the application-specific requirements are met. The sensors consist of several components, e. g. one or several imaging probes (cameras) and one or several projection systems imaging structures onto the object surface to be measured, or a system for illuminating existing surface textures. Examples of such sensors are measuring systems on the basis of fringe projection or moiré techniques as well as area-based photogrammetry or scanning systems.

This guideline applies to the measurement of 3D objects using multiple images. Unlike in testing in accordance with VDI/VDE 2634 Part 2, components of the measuring system may be moved relative to each other during the measurement. This can be achieves by re-positioning of the sensor and/or of the object to be measured. The different single images of the measured object are transformed into a uniform object coordinate system, e. g. by

• transformation of the single images through suitable reference markers

• matching of all single images into the total point cloud via the geometry of the object (matching without reference markers)

Systems in which the sensor or the measured object is positioned by measuring translational and/or rotational axes such as sensors on coordinate measuring machines according to guideline VDI/ VDE 2617 Part 6.2 are not covered by this guideline.

In the present guideline, methods and artefacts for acceptance testing and regular re-verification of optical 3D measuring systems are specified. The methods are similarly suitable for

• acceptance testing of optical 3D measuring systems

• re-verification of optical 3D measuring systems (within the meaning of "control of measuring and test equipment" according to standards DIN EN ISO 9000 to DIN EN ISO 9004)

The requirements to be met by the artefacts used for acceptance testing and re-verification are specified and some of them are described as examples. Artefacts within the scope of this guideline are linear, planar and spatial arrangements of probing elements, for example optically probable planes or spheres. Artefacts must have been calibrated with regard to their dimensions and form.

To assess the accuracy of the measuring systems quality parameters are specified. The limits for these parameters are specified by the manufacturer for acceptance testing of the optical 3D measuring systems, and by the user as far as re-verification is concerned.

The quality parameters serve to specify the optical 3D measuring systems as well as to compare different measuring systems.

As these values are dependent on the mode of operation and on the operating conditions, it is advisable to state and specify particular modes and conditions of operation for acceptance testing and reverification so that comparability of the test results is ensured. The quality parameters cannot easily be used for any measurement task whatever.

If no restrictions as to the modes and conditions of operation are made, the specified limits of the quality parameters must be complied with for all potential modes and conditions of operation. If specified restrictions are not complied with, exceeding of the pertinent limit of the quality parameters is possible and admissible.

By modes of operation possibilities of adjusting and configuring the optical 3D measuring system are to be understood such as, for example:

• type of illumination and intensity

• measuring volume and sensor measuring volume

• type, number and arrangement of optical probes used

• type and duration of image acquisition and image evaluation

• data pre-processing (filter parameters, elimination of outliers, thinning of point cloud in overlapping regions, curvature-dependent thinning, etc.)

By operating conditions the external factors influencing the optical 3D measuring system are understood. These are, for example:

• preparation of object to be measured (e. g. spraying)

• temperature and temperature gradient

• humidity

• vibration (mechanical)

• electromagnetic interferences

• illumination of environment

• dust