Proceedings Article | 21 June 2011
Proc. SPIE. 8085, Videometrics, Range Imaging, and Applications XI
KEYWORDS: Metrology, Optical spheres, Imaging systems, Calibration, Inspection, Optical testing, 3D metrology, Optics manufacturing, Surface finishing, Nanolithography
Flexible manufacturing technologies are supporting the routine production of components with freeform surfaces in a
wide variety of materials and surface finishes. Such surfaces may be exploited for both aesthetic and performance criteria
for a wide range of industries, for example automotive, aircraft, small consumer goods and medial components. In order
to ensure conformance between manufactured part and digital design it is necessary to understand, validate and promote
best practice of the available measurement technologies. Similar, but currently less quantifiable, measurement
requirements also exist in heritage, museum and fine art recording where objects can be individually hand crafted to
extremely fine levels of detail.
Optical 3D measurement systems designed for close range applications are typified by one or more illumination sources
projecting a spot, line or structured light pattern onto a surface or surfaces of interest. Reflections from the projected
light are detected in one or more imaging devices and measurements made concerning the location, intensity and
optionally colour of the image. Coordinates of locations on the surface may be computed either directly from an
understanding of the illumination and imaging geometry or indirectly through analysis of the spatial frequencies of the
projected pattern. Regardless of sensing configuration some independent means is necessary to ensure that measurement
capability will meet the requirements of a given level of object recording and is consistent for variations in surface
properties and structure. As technologies mature, guidelines for best practice are emerging, most prominent at the current
time being the German VDI/VDE 2634 and ISO/DIS 10360-8 guidelines. This considers state of the art capabilities for
independent validation of optical non-contact measurement systems suited to the close range measurement of table top
sized manufactured or crafted objects.
