Printer 600 Machine Programming.pdf - 第72页
0$&+,1( 352*5$00 ,1* 67$*( 9,6,216 <67(06 (783 1.72 User Manual Software Ve rsion 07SP04 Select Mark A select mark is an identif ication mar k placed only on the board. This dif f eren- tiates between boar…
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Fiducial
Parameters
A number of parameter values are required to be adjusted when setting up a
fiducial.
Fiducial Type This refers to the shape and dimensions of the fiducial.
Background The vision system needs to know if the fiducial is surrounded by a dark or light
background compared to the fiducial colour.
Acceptance Score After the vision system has located a stencil or board fiducial, it is then given a
level of match for that fiducial compared to the fiducial programmed in the vision
system. This match level is assigned a score, the better the match the higher
the score. The acceptance score is set by the operator as the minimum level,
above this minimum level the vision system accepts the recognition of the
fiducial.
There are various dimensions of each fiducial shape which have to be set by
the operator. The figure below describes a circular example portraying these
various dimensions.
Fiducial Diameter This needs to be set to the diameter of the fiducial to achieve a satisfactory
score.
Inner and Outer
Contours
These are set to eliminate any defects that may occur in the surface of either
the fiducial or the background. The vision system ignores anything inside the
inner contour and outside the outer contour. Increasing the distance between
the inner and outer contour can, if the fiducial and background surfaces are
variable, drastically affect the score level.
Minimum Maximum Increment Default
0 999 10 700
Outer Contour
Inner Contour
Geometric Centre
(used as a location point)
Fiducial Diameter
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Select Mark A select mark is an identification mark placed only on the board. This differen-
tiates between boards to be printed and boards to be passed through the printer
without printing. A select mark has the same properties and parameters as a
fiducial, (as described earlier in this chapter). Select marks are only used for
the selective print/pass through option, (where different product boards are fed
through the printer).
Video Model The video model is an alternative to using fiducials for board alignment. Video
models use correlation between the image of an area of the stencil and the
image of the same area of the board to align the two. This is useful if the board
has no fiducials or the condition of the fiducials does not allow satisfactory
recognition (Optimizing a Video Model paragraph refers).
Image Quality The vision system is able to accept a wide variation in the quality of fiducials,
therefore any variation in lighting normally causes no problems with fiducial
recognition. However, image quality can be optimized by ensuring the lighting
levels are correct. Changing the intensity of the vision illumination is achieved
by the adjustment of the software controlled lighting during Fiducial Setup.
X Y Reference
Video Model Fiducial
Mono Monitor Fiducial Box
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Histogram The histogram gives a graphical representation of the grey scale values within
the box set around the fiducial. As can be seen there are two peaks which
represent the light and dark areas of the picture. Ideally there should be two
distinct peaks, the separation of which can be changed by varying the lighting
levels.
Experience of changing these parameters whilst viewing the histogram, dem-
onstrates their effects.
Optimizing a Video
Model
When using a Video Model, selecting a good image shape is critical. In order
to achieve an optimum image selection, the following two paragraphs detail
some basic guidelines.
Fine and Course
Features
As with fiducials, areas of a board selected as a Video Model should have
shapes with a solid consistent tone within the boundaries (course features) and
not shapes with inner lines or lettering (fine features)
Black
% Area
Within Box
Mid Grey White
Model with Fine Features Model with Course Features