This is study how this would work. I need to make sign that will be used in day as just sign and be backlit at night. So i have made small sign for me bcs its i need to see final result . I used polycarbonate again, just this time is enclosed in plywood with oak frame to completely close light inside and back is painted black from inside, logo is engraved into playwood and 0,5mm into polycarbonate, then spray painted with clear varnish. As light source I used white led strip.
Enjoy
@dantak