Image Acquisitionand Proces

Setting Up 23
2.1.3.2 Control and Imaging Hardware Configuration
The remote computer control system is mounted in a bay of four 24-in. wide racks.
There are four 21-in. monitors controlled by one computer and a multi-monitor
video card. There is also one CRT with four video sources that is used for video
surveillance of the system. One of the four computer monitors is used for controlling
the scan process and for entering user and pallet information. The other three
monitors are used to display and manipulate the three x-ray images (Transmission
1, Transmission 2 and Backscatter). The images are generated by acquiring PMT
data on a PCI-6052E DAQ board. One thousand vertical pixels are acquired for each
x-ray scan. This is duplicated 1000 times in the horizontal direction while pallets
are moving on the conveyors to create a 1000 ¥ 1000 pixel image for each of the
three images. A PC-TIO-10 timing board carefully times the x-ray system and the
data collection. The Remote Device Access Server (RDA) that is built into NI-DAQ
and a Þber-optic Ethernet link allow the data to be acquired from a remote computer.
This isolates the operator’s console from high voltage and prevents EMI/RFI problems.
RDA provides the full 333 kS/s bandwidth of the PCI-6052E DAQ board in
a double-buffered mode. All DC analog and digital controls use Group3’s Þberoptically
distributed control hardware. The Group3 hardware is speciÞcally designed
for accelerator and high voltage applications where isolation is critical.
FIGURE 2.10 Control screen.
2.1.3.3 Control Software
The control software (Figure 2.10) was designed to allow operators with little or no
computer experience to inspect pallets without having any knowledge of how the
x-ray machine works. This meant that a very complicated process of control, conditioning
and fault detection had to be totally automated. This was accomplished by