Hotspot compensation

Background

Every projector has a hotspot. The hotspot is an area of the display that is stronger than the rest of the display. Our projectors usually have a hotspot in the bottom corner of the display.

This image will give you an idea of how it works. Positions 5 and 6 are where the power is the strongest. We need to try and make sure the power is uniform over the whole display/build area. That is where hotspot compensation comes in.

When active, hotspot compensation will display a gradient image over each layer. This causes white pixels to be grey. The darker the pixels the less power will hit the resin. The image below is much darker than usual. This is just for demonstration purposes. The image you will generate with hotspot compensation will be extremely light. It might even be difficult to see that there is something being displayed.

Hotspot compensation method 1

GiziPrint has two ways of generating the image. Method 1 will give the most accurate results but it will also take the longest.

Open the CSV file in Gizmo3DPrinters\toolbox\calibrate called Hotspot calibration - Captured with sensor 2.csv in Notepad++ or a similar text file editor. Don't use Wordpad or Word.

This is an example file. We have 6 columns and 4 rows. You can have unlimited rows and columns. More will mean you will have finer control over each pixel but it will also take longer. The higher the number the darker the area will display. In this example Column 6 row 1 will be much lighter than Column 6 row 4

The below image is what will be produced by the values. It has been enhanced slightly so that it is possible to see it a little easier.

To generate this image, go to the Hotspot tab in GiziPrint. Click the "Import hotspot compensation CSV file" and select the CSV file. GiziPrint will automatically generate a png file called hotspot_compensation.png and place it in Gizmo3DPrinters\toolbox. If you have a tool to test UV strength you can generate a test pattern through the projector and test each location.

Hotspot compensation method 2

The software ships with a test image generated with method 2. In Step 4 you can decide where the strongest part of the image is and then generate the hotspot image.

Please note: Hotspot compensation will slow down the printing. The compensation reduces the power overall. You will get better printing results because you will have a more uniform power output over the build plate. You can remove hotspot compensation by removing the file Gizmo3DPrinters\toolbox\hotspot_compensation.png

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