Horizon UserManualV6 - 第90页
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 t…
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 strategy set 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.
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.
Software Version 6 User Manual 1.73
MACHINE PROGRAMMING
STAGE 6
GEOMETRIC CENTRE
(USED AS LOCATION POINT)
FIDUCIAL DIAMETER
INNER CONTOUR
OUTER CONTOUR
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.
1.74 User Manual Software Version 6
MACHINE PROGRAMMING
STAGE 6
Mono Monitor
X Y Reference
Fiducial Box
Video Model Fiducial
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, while viewing the histogram,
demonstrates their effects.
Optimizing a
Video Model
When using a Video Model, selection of a good image shape is critical. The
following are some basic guidelines for selection of an optimum image.
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):
Software Version 6 User Manual 1.75
MACHINE PROGRAMMING
STAGE 6
Black
%Area
Within Box
Mid Grey
White
Darker Lighter
Model with
Fine Features
Model with
Course Features