4 Design and function
3DPIXA
CD40131 Version 1
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Illumination type
Properties
Examples of use
Tube light illumination
Light beams illuminate
the surface from many
different angles.
Very diffuse and
homogenous illumination
Reduces shadow
casting
The contrast depends on
the structure of the
surface.
Brushed aluminum
Electronic board
Solder paste
Connector pins
Coaxial illumination
The object surface is
illuminated with parallel
light beams.
Reduced shadow
casting
The semi-transparent
mirror has a 50%
reflectance. The
irradiance on the camera
sensor is 25%.
Plugs/sockets
Plastic parts
Tab. 11: Illumination types
4.8
Image quality, image sharpness and height accuracy
For accurate height measurement the images taken with the 3DPIXA camera must show as
much texture of the scanned object as possible. Textures in the images are an important pre-
condition for the passive stereo approach. To make the structures of the surface visible in the
image, observe the following:
The interaction of the surface properties and illumination is crucial. The illumination type
(see chapter 4.7, p. 28) and brightness of the illumination is important. Images should
have as few dark and as few overexposed areas as possible.
Acquiring a sharp image will ensure that the visible structures in the left and in the right
image have the best contrast possible. Sharp images of suitable surfaces will show a
visible difference in the color or brightness of neighboring pixels. Thus, pattern matching
can be performed reliably and accurately (see Fig. 10, p. 30).
