Programming Manual
PHYTEC Messtechnik GmbH 2008 L-720e_0
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The value
ppl
and
lines
define how many pixels should be generated
from the incoming video picture.
ppl
indicates the number of pixels
per line, and
lines
determines how many lines (pixels in y-direction)
are produced. Both values indicate the resolution of the image.
A whole frame in PAL format has 720 pixel x 576 lines. In order to
digitize the image with the highest resolution,
ppl
will be 720 and
lines
= 576. The smallest resolution for PAL is 50 x 40 pixels per
frame.
If fields are used, the maximum resolution is 720 x 288 lines.
Since the definition of
ppl
and
lines
always refers to fields, the actual
number of lines of the TV-picture to be digitized is twice as high. The
width/height ratio for the digitized field (maximum 720 x 288 pixels)
gives a distortion of two in y-direction. In order to avoid this effect
digitization is done in interlaced mode (if the high resolution is
required) or you can reduce the resolution to
ppl
=360,
lines
=288 and
the resolution will be proportional with 360 x 288 pixels.
Note:
For stereometric work or automatization applications, a correct
proportional resolution is not always required, as long as the distortion
is taken into consideration in the algorithm. So the complete field
resolution of 720 x 288 can be used for stereometric work, which is
more accurate in x-direction than in Y-direction. It is also possible to
adjust the axis of the camera in the direction the measurement has to
be taken.
The window with the proportions
hsize
x
vsize
is a section of the
digitized image, which has the size
ppl
x
lines.
If
hsize = ppl
and
vsize
= lines
the whole digitized image is displayed. If this parameters are
smaller, only a section of the image is displayed. The ratio of hsize to
vsize does not alter the proportions of the image, since no scaling
occurred and only a certain section of the image is taken.
Figure 47
and
Figure 48
demonstrate the significance of the
parameter.
