Adjusting domestic DLP for PCB Uv photolithography

Jul 2019
Helo; My specialty is electronics, so I need help from experts in optics.
For the past couple of years I have been using a modified domestic DLP projector to impress photosensitized PCBs with dryfilm for the manufacture of my PCBs. In this way I get resolutions of more than 1000 dpi and I avoid making an intermediate photolith. The modifications that I make to the DLP consist of 1º; change the original lamp with a power UV LED and 2nd; modify the focus optics to obtain an image of a square inch, and thus achieve the desired resolution. Finally, I place the modified DLP on a robotic X-Y table and by software impress PCB by sectors until completing the board. The results are truly fantastic;.... at least with the HP DLP that I modified a couple of years ago.
Now I want to do the same with an Acer DLP (K330) that has 20% more resolution and uses LED instead of lamp ... what interests in some aspects. But I have found an insurmountable problem when modifying the focusing optics. To achieve a focus on an image of the right size without spherical distortion, what I did in the first DLP (and that works very well), is to move the entire focusing optics group a few millimeters from the DLP chip, thus allowing to achieve a small image. This displacement is performed on the same original axis of the optical group and without altering anything from the group of lenses, I simply move the entire group of lenses a few millimeters to the outside ... away from the DLP chip. As I say, in the DLP that I already have mounted (an HP) works perfectly, but in this new K330 the image obtained is, effectively, smaller, but does not focus on a plane parallel to the DLP chip ...Assuming that the image is a rectangle, the lower horizontal line focuses closer to the optics, and the upper one, a couple of centimeters further away. In fact, I think the image if it even focuses on a plane ... but in a spherical cap ... I'm not sure. Obviously, the image obtained is unusable. It is not feasible to use the keystone for reasons of DPI alteration. Is this aberration due to the imperfection of the optics? ... that manifests in small images of small focus and not in large, with major focus (original mount)?. Any suggestions for a solution?
Thank in advance and excuse my terrible english ...

I add more data; the optics mounted on the K330 is telecentric (it has TIR). The optics output is vercically shifted to obtain an offset that does not reach 100% ... although the latter is usual in all domestic projectors.
Sep 2019
I saw a piece of information yesterday about using aspheric lenses to improve distortion. You can pay attention to this aspect.
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