Rockwell Automation 5370-CVIM2 Module - Manual (Page 47)

Chapter 3
Image Acquisition Parameters
3–8
Light Reference Settings
The light reference settings are adjusted by picking and dragging the left ( Hi )
and right ( Lo ) cursors up or down, or by picking a point along the left or
right side of the slide bar. In the latter case, the cursor will jump to the
location of the light pen/mouse cursor.
The two references select high and low brightness values or “cutoff points”
that apply to all pixels within the image. They interact to affect the contrast
in the entire image. Individually, the reference settings have the following
effects:
•
Hi reference setting –– The Hi reference has a value within a range of 1
to 255, where 1 is the lowest brightness in this range and 255 is the
highest. This setting determines the upper limit for the brightness of the
lightest pixels in the gray scale image. (Note that the lower limit is
bounded by the
Lo reference setting; thus, if the Lo reference is set to
127, the Hi reference cannot be set lower than 128.)
Thus, any pixels in the image whose original brightness is higher (that is,
lighter) than the corresponding high reference will change to saturated
(255) white. (Note that during the adjustment these parts will appear
green, as explained later.)
•
Lo reference setting –– The Lo reference has a value within a range of 0
to 254, where 0 is the lowest brightness in this range and 254 is the
highest. This setting determines the lower limit for the brightness of the
darkest pixels in the gray scale image. (Note that the upper limit is
bounded by the
Hi reference setting; thus, if the Hi reference is set to 128,
the Lo reference cannot be set higher than 127.)
Thus, any pixels in the image whose brightness is lower (that is, darker)
than the corresponding low reference will change to saturated (0) black.
(Note that during the adjustment these parts will appear blue, as explained
later.)
You can see the high and low values in the boxes above and below the slide
bar. As you move each cursor up and down, the corresponding box displays
the changes in the value.
NOTE: The CVIM2 system acquires a new image every time you move a
light reference cursor. The trigger defined in the
Setup Camera panel is
used for this purpose. Usually, the Auto camera trigger is used when setting
the light references; however, when using an external trigger source, if no
trigger pulse occurs within about five seconds after you attempt to move a
cursor, system warning message #3072 appears on the display, as shown in
Figure 3.4 (page 3–6). If you see this message, you can either pick the
button to discontinue the attempt to move the cursor, or you can
pick the button to try again (when you expect a trigger signal to occur
within five seconds).