I need some help with this project (optics and lens design)

[Warsaw]

The diagram below is not to scale. I'm trying to add a lens (or lenses) behind the one shown in this camera so that I can focus the image on a film plane of 15mm, rather than the current 120mm (Y). The focal length (X) needs to be at or greater than the current 60mm. What would the specifications be of a lens to accomplish this? Is it possible?

Thank you in advance for any help you can provide!

 

[mgb_phys]

If you have a chosen focal length then the size of the image is already fixed.
You can add extra lenses but that changes the focal length.
Or you can also chose to only use the central 15mm of the image

 

[Warsaw]

It's not a problem if I have to change the focal length. Shrinking the 120mm image down to 15mm is my goal here.