Have you ever tried to read a map at nighttime using the overhead courtesy light? If so you will know you get blinded by the light shining directly into your eyes. And that can be dangerous if you are doing 70 mph and your passenger wants to map-read.
Hence the solution above fabricated at great cost using a bit of black card. The delux version would have aluminium foil on the reverse to increase the downward light.
The good news is that I am willing to licence the patented design for mass production at a really reasonable cost.