With this thing you can attach a usb cheap usb microscope to your ender 3.

The idea behind it is that it can be used for

1. rigid, precise and repeatable positioning of the microscope
2. automatic bed leveling
3. scanning and stiching of images for a large area high resolution image
4. automatic print quality validation via computer vision
5. low resolution 3d scanning by taking advantage of the narrow field of depth, i.e. only points in the focal plane are sharp this can be detected by e.g. an edge filter, then multiple planes are scanned by moving the head through the corresponding z-positions
6. printing on existing objects is possible if the above features work

There is no software yet. I'm planing to write it in the future. Also there are still problems to move the ender 3 with the stock firmware. If anyone has some helpful info, please let me know.