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248 Andrei Mihalache et al.
CMM
with laser
system
CMM
with
touching
probe
Physical model
(sample or prototype)
CNC – milling
machine with
touching probe
Digitizing
software
Points cloud
(3D coordinates)
CNC –
milling
machine with
laser system CT
Computer
tomography
Fig. 2 – Digitizing techniques for 3D-geometries and generated data.
3. Differences between Digitizing and Scanning Processes
3D scanning (digitizing) is the process of gathering data from undefined
three-dimensional surface. During the scanning process, an analogue scanning
probe is commended to move back and forth (contact or non-contact) across the
unknown surface. During the process, the system records information about the
surface in form of numerical data’s – and generates a points cloud matrix (3D
coordinates). The terms of digitizing and scanning are often used to describe the
same process. Traditionally, digitizing refers to the process of taking discrete
points using a touch-sensible probe. However, with the introduction of new
technologies in data capture, such as laser or camera, digitizing term is now
used as general description for the process of data acquisition from undefined
surfaces [2] – [4]. The digital points cloud can be captured using different
digitizing techniques (Fig. 2), classified into two major groups:
‐ Mechanical techniques (by physical contact sensors);
‐ Optical techniques (by non-contact with the object).
Related to the first group, usually they use a coordinate measuring machine
– CMM, or a CNC-milling machine equipped with physical touching probe
sensors (ex. Retroscan or Renscan – Renishaw, UK). Related to the second