Image Acquisitionand Proces

224 Image Acquisition Processing with LabVIEW
and background is at least 30, and each digit to be detected is larger than 18 ¥ 12
pixels, IMAQ Read LCD is generally successful.
As described previously, using the Vision Toolkit LCD VIs is quite simple. Figure
8.5 is an example application. As you can see, the user has deÞned the ROI to
encompass the two digits on the right, and IMAQ Get LCD ROI has detected two
digits within the ROI. IMAQ Read LCD has then successfully determined that the
two digits are both eights. This example was achieved using the code shown in
Figure 8.6.
FIGURE 8.5 Interactive 7-segment LCD example.
FIGURE 8.6 Interactive 7 segment LCD example — wiring diagram.
8.2.2 BARCODES
Labeling parts with machine-readable codes has become extremely common in
recent years. From every packaged product in a supermarket, to library books, and
even employee cards, barcodes are one of the cheapest and easiest systems that we
can introduce. LED or laser handheld barcode scanners are inexpensive and are
simple to interface to computers either through the PC’s serial port or in line with
the output of the keyboard (often known as a keyboard wedge). The Vision Toolkit
includes VIs that can resolve and read barcodes that are part of an image. If you are
already acquiring an image of an object for other vision-based reasons, it makes