A laser based SLA printing technique utilizes a single laser spot, leading to highly uniform beam intensity across the whole build size, given the scanning angle is reasonably small. However DLP and LCD based printers use a wide spread beam source, so uneven light intensity is an intrinsic issue. The easiest way to effectively remove this issue is using a so-called grayscale mask. Without the mask, the layer information usually consists of fully off (normally 0) and fully on (normally 255). With the mask on, the intermediate gray values are used to suppress higher intensity areas into the lowest value to make even light illumination across the build size.
There are several previous works to make this feature feasible to everyone. I guess the first one was done by nc42 on buildyourownsla.com (here), using UV sensor and interpolation using Rhino. It works great, but it looks a bit complicated to me for both of hardware and software parts. Most recently Will Kostelecky on Wanhao duplicator 7 facebook group uses a NanoDLP's embedded feature (might be created by Will's request) to create the mask and successfully make an even light intensity. I like his approach, especially for bluetooth connection and options for UV or normal light sensors. However it's still using spreadsheet and requires multiple steps for creating a compensation mask file. His device is great, but still it's complicated for how often we need.
Therefore I decided to create a similar feature inside MonoWare. It still requires either of UV light sensor or print a test structure, but you don't need a spreasheet work anymore and everything is processed inside a tool.
I'll briefly explain the procedure assuming you have a UV light sensor. You can buy a sensor or build your own using ML8511 breakboard. (I'll explain the ML8511 part later)
1. Connect your PC with MonoWare with a projector or LCD panel.
2. Launch the MonoWare and go to Printer -> Printer setting -> Correction -> Intensity Compensation
3. Push the button, "Create a new compensation image"
4. It will open a window showing a grid table. Try to change the grid size and output image size. You can just type the information on the table and then select the data is light intensity or required exposure time.
5. There are two methods for filling up the table. If you already have a data file that is formatted to MonoWare requirement (*), you can just import the file into the table using "Load data from TXT file" button. Or you can display local spots by pressing "Display local spots" button. Once you click the button, each rectangular spot will be displayed on the DLP projector or LCD screen. Then you can type the reading from the sensor into the table.
6. When you're done with the data, press OK button and then specify file name for PNG file and TXT data file. These files will be saved under Program Files/MonoWare/. You may want to see the text file and image file if they are correctly created.
7. Good! You just make a grayscale mask with MonoWare. You can continue to use this file with MonoWare to make even light intensity of the DLP projector or LCD display, or you can export this file into NanoDLP or CreationWorkshop.
All Mono1 complete packages and Mono2 printers will be pre-calibrated using UV light sensor and above procedure. You can start printings with even light intensity across the whole build plate.
If you have any questions/comments, please leave here or send an email at firstname.lastname@example.org.