The reason for two independent loops (sometimes called the Consumer/Producer Design Pattern) is you have two processes that run at different speeds, and you want them to run "simultaneously" and not interfere with each other. One, the "Producer", produces images at regular timed intervals (say one every 5 seconds). The other, the "Consumer", takes the output from the Producer and "consumes" it, i.e. does something such as writing it to disk. As long as the process of Producing takes less (total) time than the process of Consuming, the two processes can (almost always) run simultaneously, with the Consumer never missing any of the data that the Producer is sending.
I think the basic framework for this Design Pattern is one of the Example Projects that ships with LabVIEW. Doing a search for Consumer/Producer (or Producer/Consumer) should also give you helpful ideas.
Bob Schor
