I added a thread to the base and made two screws out of brass to hold lenses.
Now I can adjust focus by turning the lenses.
Because the lenses are taken from scrapped equipment, it all does not fit perfectly:
There is a notable defocus aberration between center and margin, which could be corrected with the correct set of lenses which I don't have.
Added an aperture to the lenses to minimize defocus aberration and it worked quiet well.
It is made out of black electrical tape. I marked three lines each 120° to another and parallel lines to each to get a template for the lens. On the lens i marked them with a cutter knive because the groves can be seen through the tape.
I'll upload some pictures as soon as I developed them.