GE XLG3 - Manual (Page 102)

User Manual Chapter 7 Measuring Features and Defects 93
About the Matching Cursors
For each cursor you place on the left image
during stereo measurement, the system
places a matching cursor on the right image
for use in triangulation.
You must place each left cursor on an image
point (a pixel) that has sufficient surrounding
detail to differentiate it from its neighboring
pixels. If the neighboring pixels look the
same as the point you choose — especially
the pixels to the point’s left and right, for
example, pixels along a smooth horizontal
line — the system cannot accurately place
the matching cursor. When there is enough
differentiating detail, the “match strength” is high (meaning that the generated match point
clearly matches better than its neighboring pixels — the system’s confidence in the match
is high). But if there is not enough detail, the match strength is low (meaning that the
generated point and its neighboring pixels match almost equally well — the match may be
correct, but the system’s confidence in the match is low).
For every matching cursor, the system calculates a match strength value between <0>
(lowest confidence) and <5> (highest confidence). If too little detail is present, the system
simply does not generate a matching cursor. Whenever possible, you want to achieve a
match strength of at least <3>. If you can’t, try capturing another image with less glare or
more image details. (Adjust the tip orientation or brighten the image.)
Even when match strength is <5>, and especially when the match strength is lower, you
need to verify that the matching cursor appears to be placed properly. A matching cursor
that is off by just one pixel can have a significant impact on the measurement accuracy.
To Reposition a Matching Cursor
1. If zoom windows are open, press to close them.
2. Move the matching cursor to the correct position, as described on the screen.
When you stop moving the cursor, the system optimizes the match position.
(If you leave zoom windows on while moving the matching cursor, the system does
not optimize the match position.)
Each manually corrected matching cursor is indicated by two things: a square around
it, and the absence of a match strength number.
Note Matching cursors are most likely to be misplaced when the measurement area
contains a repeating pattern. Generally, you get the best results by leaving the
matching cursors exactly where the system places them.
Your cursors Matching cursors
This distance must be accurate.