This project was motivated by the success of my UF-1504 with pre-collimator setup. When comparing the beams of my 1504 with dedomed XPG2 and C8 with smooth reflector and dedomed XPG2, the hotspots were nearly the same size even though the 1504 has ~2.5x the beam lux. The double lens setup is apparently better at getting more lumens in the actual hotspot. The C8 reflector is still getting a lot of the light downrange, but a lot of it is located in the less bright corona.
So I wanted to put a double lens setup in the C8 to try to get the largest hotspot I could. In the left image is the 1504 compared to the C8 reflector. In the right image is the 1504 compared to the final product C8 lens setup. The C8 reflector puts out 184Kcd at 30sec. The C8 double lens setup ended up putting out 166Kcd at 30sec. The hotspot is now nearly as bright as the center of the C8 reflector beam, but is significantly larger. The C8 lens hotspot is ~1.7x the width or 2.9x the area of the 1504 hotspot.
Here are some details on the build. Here it is pictured with an EE X6.
The main lens is this one from edmund optics. It is expensive at $30, but I wanted a fresnel lens instead of a glass lens in order to keep the compact form factor of the C8 and to keep it light. More inexpensive fresnel lenses from fresnelfactory have smaller line densities and so their efficiency is not as high. I cut it out with a dremel cutting tool and cleaned it up with a file.
The precollimator lens is an 18mm glass lens from kaidomain. The difficulty with this build was mounting the precollimator lens and getting the focus distances right. Without the precollimator lens the fresnel lens focal length is too long for the C8 by a few mm (and my C8 has integrated shelf). I had a supfire L6 with removable pill and I happened to have ordered another pill for it that was ~5mm shorter than the stock pill so I started with that. With just the fresnel lens the beam intensity was 177Kcd at 30sec and the beam size was exactly the same size as the 1504 beam above.
I made a precollimator lens mount out of the plastic casing that came with TIR optics from LEDDNA. My XPG2 was on a 16mm MCPCB and this plastic casing was just the right size to fit into the 20mm space in the pill, around the 16mm MCPCB. I drilled it out to the right diameter and trimmed it to the right height so the cone emanating from it was just overfilling the fresnel lens. I used superglue to attach the lens to the mount. Here it is in one of the L6 pills.
When the precollimator lens is in place it makes the LED appear further away from the fresnel lens, and it turns out it was exactly right for the stock C8 shelf-to-lens distance, so I moved it into the C8 with integrated shelf. I was happy about this because I had wanted to use the C8 in the first place because of its compact size compared to the supfire L6.
Here is a shot from a few meters away looking into the lens, shot through “solar viewing” glasses.
Here is the beam compared to a C8 smooth reflector with XPL HI V2 3B (107Kcd at 30sec) on the left, and an EE X6 with dedomed XPL V6 1A (94Kcd at 30sec) on the right. The exposure settings for all the beamshots are the same (f5.6, 1/500s, ISO400), but the white balance was on auto. :person_facepalming:
This C8 double lens beam size is a bit bigger than the C8 reflector hotspot with XPL HI and a bit smaller than the X6 hotspot with dedomed XPL. I’m pretty happy with the result. The lux measurements for the C8 lens light were done without a flat glass lens in place. I plan to get a high transmission lens to put in to protect the fresnel lens.
