DEK INFINITY USER MANUAL - 第69页
INFINITY 0$&+,1 (352*5 $00,1* 67$*( 9,6 ,216<67(0 6(783 Soft ware Ver sion 7 User Manual 1.67 Fiducial Parameters There are a number of paramete r values which need to be adjuste d when setting up a fiduci…
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1.66 User Manual Software Version 7
STAGE 7 - VISION SYSTEM SETUP
Introduction The printer uses a vision system to carry out the following:
• Stencil/Board Alignment
• 2Di Inspection (optional)
• Board Identification - Selective Print/Pass Through (optional)
After the board is fed into the machine to the board stop position, the camera
moves into position to view the relative board and screen features. The infor-
mation from these camera images is used by the vision system to calculate the
screen correction needed and to identify the board, if selective print/pass through
is enabled. The camera and vision system is also used for 2Di inspection, if
enabled, for further information refer to the 2Di chapter in this manual.
Fiducials A fiducial is an alignment mark which is produced as a part of the artwork of the
board and the screen. There are normally several of these marks on each board,
some of which are used for board alignment and some for alignment when
placing components on the board. These marks, therefore, should be in the same
relative position on both board and screen. The vision system has a library of
synthetic fiducials of the most commonly found shapes. The dimensions of
these fiducials can be tailored by the operator to fit the fiducials on the board and
screen. After the vision system has been taught these fiducial parameters, it is
able to search the field of view of the camera and recognize any features which
resemble these fiducials. The centre of the fiducial is calculated and used as the
point of location.
The vision system conducts a search in the field of view of the camera looking
for any shape that resembles the programmed fiducial. After finding a shape it
is assigned a score comparing its shape and size to the shape and size of the
fiducial in the vision system memory. This score is set between 1 and 999, the
better the fit the higher the score.
NOTE
However, this does not mean that a fiducial score of 999 for example aligns more
accurately than a fiducials score of 700 for example.
This score is used, in conjunction with acceptance parameters set by the opera-
tor, to recognize the fiducial. The available fiducial shapes are:
• Circle
• Rectangle
• Diamond
• Triangle
• Double Square
• Cross
Circle
Cross
Diamond
Triangle Rectangle Double square
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Fiducial
Parameters
There are a number of parameter values which need 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 screen or board fiducial, it assigns a level
of match of that fiducial compared to the fiducial programmed in the vision
system. This is given a score, the better the match the higher the score. The
acceptance score is the minimum level, set by the operator, above which the
vision system accepts the recognition of the fiducial.
Minimum 0
Maximum 999
Increment 10
Default 700
There are various dimensions of each fiducial shape which have to be set by the
operator. As an example, here, the circular fiducial is described.
Fiducial Diameter This needs to be set to the exact 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.
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, to differentiate
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 above. A select mark is only used with 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
model uses the correlation between the image of an area of the screen 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 (see optimizing a video model).
Image Quality The vision system is able to accept a wide variation of quality of fiducial,
therefore any variation in lighting normally causes no problems with fiducial
recognition. However the 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