Phytec eGrabber-4plus, Руководство по оборудованию

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Start-Up of the Grabber with Demo Programs
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PHYTEC Meßtechnik GmbH 2004 L-608e_4
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Figure 28: Creating a Full Image: Two Fields, Each with 7 Rows
According to the PAL-norm, each signal contains 625 rows.
The
rows are divided into field frames: the first field
(odd field1 with rows 1-625) and a second field (even, field2
with rows 2-624). An image section is fully recognizable by one of its
half fields. The image’s vertical resolution is reduced by half, since
the image is only represented by 228 rows (excluding the invisible
rows that precede and succeed the image as well as test and data
rows). A total of approximately 576 from 625 rows remain visible
Digitizing a field is time efficient; compare 20 ms for a field image to
40 ms for both fields (full frame).
If the same field (i.e. the first) needs to be digitized repeatedly, there is
a pause of 20 ms between the processes.
Digitizing a full frame can create a distorted image if the object moves
too quickly. The object is in a different location in the first field than it
is in the second, creating a comb effect. The image may appear as
shown in Figure 29).