What considerations were taken into account when the upper part of the lens was designed to be so thick? The upper part is solid inside, and the top of the lens is also flat. This part is just like a thick piece of plate glass and basically doesn’t play any role in shaping the light path. Removing this part or making it thinner won’t have any optical impact either. I can’t figure out the advantages of such a design, but I can think of several disadvantages. For example, it increases the length of the flashlight head, adds to the weight, and reduces the floodlight range. However, the designers of SureFire are not fools. They surely can’t have failed to consider the things that an amateur like me can think of. They shouldn’t have designed it randomly for no reason. So, what were the considerations for designing this lens in this way? Are there any experts who understand this and can come forward to answer my questions?
Looks like a retrofitted TIR for a head designed for reflectors. They increased the length of the TIR so they don’t have to change tooling for the metal part. They could either raise the shelf by using a thicker MCBCP, or lenghten the TIR by making the front part thicker.
Generally a TIR is shorter than a reflector for the same optical properties, since the refractive index of the PMMA material is higher than air, it bends the lights more so it doesn’t need as long to shape the beam to the same intensity. As for why they choose to use TIR to replace the reflector, maybe for better shock resistant and spill control. The TIR spill is always different to reflector spill, with soft fade to darkness instead of a hard cutoff.
From the pictures provided by the seller, when looking in from the glass side, one can faintly discern the thickness of the lens flange.
From the pictures, it seems to me that the flange on the upper part of the lens in the official version is thicker than that of the prototype, but the seller mentioned that they look almost the same in thickness.
In other words, the design of the lens shape was essentially finalized in the prototype, and it doesn’t seem like there was a previous structure that was later removed.
It seems that the thickness of the flange on the upper part of the lens has been this way since the prototype, or perhaps it wasn’t as thick in the prototype and was later modified and thickened in the official version.
The reason for making it this thick, I guess, might be for shock resistance and to prevent stress concentration.
Because that seller mentioned he has disassembled many KL3 lamp heads, and the flange at the top of the KL3’s lens is not as thick. He also noted that almost all the lenses he took out had cracks.
