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SYMBOL VERIFICATION OVERVIEW
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2.4 AIM DPM QUALITY GUIDELINE
The AIM DPM Quality Guideline is applicable to the symbol quality assessment of direct
parts marking performed in using two-dimensional bar code symbols. It defines modifi
cations to the measurement and grading of several symbol quality parameters.
The marking processes covered by this guideline are as follows: Dot Peening, Ink Jet, Laser
Etching and Electro-Chemical Etching.
The defined lighting environments are denoted in the reported grade using the format defined
in IEC/ISO 15415 using the angle specifier with a combination of numbers and letters as
defined below.
Diffuse perpendicular (on-axis/bright field) (90)
The symbol is uniformly illuminated with diffuse light incident at 90 degrees to the plane of
the symbol. The angle specifier shall be 90 to denote this lighting environment.
Diffuse off-axis (D)
A diffusely reflecting dome is illuminated from below so that the reflected light falls non-
directionally on the part and does not cast defined shadows. This is commonly used for
reading curved parts. The angle specifier shall be D.
30T Low angle, two direction
Light is aimed at the part at an angle of 30 +/- 3 degrees from two sides. The light may be
incident from any of the two possible orientations with respect to the symbol (see 6.2.2
below). The lighting shall illuminate the entire symbol area with uniform energy. The angle
specifier shall be 30T.
30Q Low angle, four direction
Light is aimed at the part at an angle of 30 +/- 3 degrees from four sides such that the lines
describing the center of the beams from opposing pairs of lights are co-planar and the planes
at right angles to each other. The lighting shall illuminate the entire symbol area with uniform
energy. The angle specifier shall be 30Q.
30S
Overall Symbol Grade :
The (Overall) Symbol Grade is only meaningful if it is expressed in conjunction with the
measurement wavelength and aperture used. It should be shown in the format:
DPM Grade / Aperture / Wavelength [/ Lighting ]
Where:
•
“Grade” is the Overall Symbol Grade (i.e. the the arithmetic mean of the individual Scan
Grades for a number of tested images of the symbol, normally one).
•
“Aperture” is the diameter in thousandths of an inch (to the nearest thousandth) of the
synthetised aperture used to obtain the grade for the symbol.
•
“Wavelength” is the Peak Light Wavelength in nanometres.
•
“Lighting” is the lighting environment used to obtain the grade of the symbol (if 45Q it is
omitted).
DPM2.0/10-20/640/(30Q|90|30T)
DPM1.0/10-20/640/(30Q|90|30T|D)
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