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User Manual S-23 HM 6 Vision functions Software Vers ion SR.405.xx 05/99 Iss ue 6.5 Teach Fiducial 209 È Ma ke su re that the re are n o other struc tures wi thin the search area . Otherwi se, fiduc ial id enti- fication…
6 Vision functions User Manual S-23 HM
6.5 Teach Fiducial Software Version SR.405.xx 05/99 Issue
208
È Use the arrow keys to change the camera position. You can specify the step width by entering
a number in the range 1 - 6.
È Use the + and - keys to move the fiducial boundaries and teach them at the same time. With
the space bar you can toggle between horizontal and vertical directions. With the Tab key you
can toggle the field step width between 1 pixel and 10 pixels.
È Press Return to launch the teaching process.
The unique value appears on the screen as the measurement result. This may vary between 6
0 = unsatisfactory and
100 = very good differentiation capability. 6
Practice shows that a uniqueness value of at least 60 must be achieved. 6
È Repeat the teaching process a number of times with changed field sizes. In this way you can
optimize the uniqueness value. Reducing the size of the search area to dimensions which are
less than those of the fiducial itself will increase the uniqueness value since the fiducial ends
will, for example, when wetted with solder-stop lacquer, exhibit poor reflection characteristics.
However, you should not select too small a field as this may impair the uniqueness of the fidu-
cial among other things.
È Press Esc to quit this option.
NOTE 6
If you wish to use a fiducial despite the fact that it has a low uniqueness value, you should
ensure that the fiducial has a good quality value (see Section 6.5.6.2 on page 221).
If the quality is bad as well, it would be better to select another fiducial (see Criteria for Cre-
ating Fiducials in Section 6.2.5 on page 176). 6
Changing existing fiducials 6
During each teaching process the centering offsets are set to zero. If this is not done, optical cen-
tering with the fiducial structure field boundaries will not be correct; the measurement results
would be distorted. 6
6.5.4.3 Search Area Option
The search area is a freely selectable field within the field of view of the camera. 6
NOTE 6
È Always select a size for the search area which will still also take into account tolerances in
board positioning.
User Manual S-23 HM 6 Vision functions
Software Version SR.405.xx 05/99 Issue 6.5 Teach Fiducial
209
È Make sure that there are no other structures within the search area. Otherwise, fiducial identi-
fication could be made unnecessarily more difficult.
È Repeat the tests with different search area sizes. It may also be appropriate to optimize the
uniqueness value.
When you select the Search area option 6
– the menu closes,
– the teaching process is launched,
– the video image is shown with fiducial and search area, and
– header and footer with commentary, measurement results, key assignments and command se-
quences are displayed.
6
Fig. 6.5 - 16 Teach fiducial menu, Teach search area video image
È Use the arrow keys to change the camera position. You can specify the step width by entering
a number in the range 1 - 6.
È Use the + and - keys to move the fiducial structure boundaries and teach them at the same
time. With the space bar you can toggle between horizontal and vertical directions. With the
Tab key you can toggle the field step width between 1 pixel and 10 pixels.
È Press Return to launch the teaching process.
Fiducial No. = 8 Uniqueness = 70
Blank: hor./vert.
Tab : step width
Change search area
1..6 : x/y step
: y axis +
: y axis -
x/y step width = ...Direction = ...Field step = ...
Ret: teach
- : smaller
+ : larger
: x axis +
: x axis -
6 Vision functions User Manual S-23 HM
6.5 Teach Fiducial Software Version SR.405.xx 05/99 Issue
210
The uniqueness value appears as the measurement results. This may vary between 0 (= unsat-
isfactory) and 100 (= very good) differentiation capability. 6
Practice shows that a uniqueness value of at least 60 must be achieved for fiducials and ink dots. 6
È Repeat the teaching process a number of times with changed field sizes. In this way you can
optimize the uniqueness value.
È Press Esc to quit this option.
NOTE 6
If you wish to use a fiducial despite the fact that it has a low uniqueness value, you should
ensure that the fiducial has a good quality value (see Section 6.5.6.2 on page 221).
If the quality is bad as well, it would be better to select another fiducial (see Criteria for Cre-
ating Fiducials in Section 6.2.5 on page 176). 6