Beam-forming lens with internal cavity that prevents front losses

DETAILED DESCRIPTION FIG.
1 shows lens body 10 with front face 11, recessed convex lens 12, forwardly divergently curved sidewall 13, rear cylindrical cavity 14, with sidewall 15, and front wall 16, the walls intersecting at corner 17, incandescent lamp 20 with filament 21 supported by posts 22, with base 23, and with glass enclosure 24.
The cavity has a forwardly extending axis 14a.
The circular corner 17 of cavity 14 is a key feature in that it prevents light from filament 21 from directly reaching front surface 11.
Rearward-going ray 30 is reflected by curved sidewall 13 into collimated ray 31.
Upward-going (i.
e.
, forward-going) ray 32 aims toward or is directed toward corner 17, but ideally must strike either front wall 16 or sidewall 15.
If striking front wall 16, it is refracted to form a more vertical (forward-going) ray 33, which is refracted by convexity 12 to collimated ray 34.
If striking sidewall 15, it is refracted to less vertical ray 35, which strikes the uppermost part of curved sidewall 13, which reflects it into collimated ray 36.
To the extent that it is ideally sharp, corner 17 prevents light from filament 21 from being lost out front face 11, which is the case with conventional reflectors.
This is a key teaching of this invention: the internal cavity 14 in dielectric lens 10 has sharp corner 17 that prevents front losses typical of conventional reflectors.
FIG.
2 shows lens body 40, which is similar in operation to body 10 of FIG.
2, but has totally planar front face 41 to facilitate production by molding.
Internal cavity 44 has curved front face 46 that performs the same collimating function as convexity 12 in FIG.
1.
Refracting sidewall 45 of cavity 44 is slightly conical to facilitate removal of lens body 40 from a mold.
Front face 11 and sidewall 13 remain the same, but recessed convex lens 12 is omitted.
FIG.
3 shows lens body 50 modified further to facilitate molding for larger embodiments of this invention, such as an automobile headlight.
Front surface 51 is slightly forwardly convex to prevent the slumping typical of a planar front