The light of the build area of a DLP UV printer isn't evenly spread. The source of light is a 9 LED UV array. The light mainly falls of to the sides. This results in objects curing too much in the center, or not enough on the outer sides of the build area. One can compensate for this, making the LCD build area have a homogeneous intensity of light, using a mask. But it needs to be specifically created for each physically unique printer. Having a homogeneous illuminated build area results in better quality prints.
How can I create such an mask accurately for a UV 3D resin printer that uses DLP technique, like for example for a Wanhao Duplicator D7?
To summarize: you measure the LCD build area using a multi-meter and a light dependent resistor. You do this with low and high intensity masks. You feed the numbers in CSV files to the software, and the software will generate a mask for you by polynomial curve fitting. See this page that explains in detail how the mask is created, if you are interested.
You can download a release here.