This is a thread for people to share their experiences and knowledge about LED light focusing solutions. Master Yoda said it would be cool if we had a thread with info about lenses and I must obey my master. :D
This is a stumbling block for our hobby because of the lack of choices of narrow beam LED products that actually fit in a hilt.
Beam patterns and intensities are very difficult to quantify and compare even with fancy equipment so I will take a more simple approach on the subject to try and convey my findings on the matter. Besides the fact I don't have 2 of everything to compare side by side. ;)
I have found a fairly simple way to tell whether or not a a lens or reflector can be a good match for a LED, and if it is worth trying to use. I basically look straight down the optic then turn it at an angle a bit and note what I see. Feel free to inject your opinion whether similar or different.
We seem to be limited to two basic groups of solutions. Clear plastic lenses, and reflectors.
Some fundamental differences that stand out to me regarding performance are.
More difficult to get a even, narrow beam, free of hot spots.
More light lost to the side rather than straight out the front.
More available options.
Can make a tighter, evenly spread out beam.
Less available options.
Must be suited to fit a certain LED type exactly to work well.
Must have super smooth surface.
Must be positioned precisely in the right spot.
Here are some examples to support my findings and to show a simple method I use to tell if a solution should work or not. You can right click and view image to see bigger pic.
Here is a LEDEngin 10w. With this reflector if you look straight at the LED you can see the reflection of the 4 dies off the reflector ok. This tells us that most of the light will go where we want it to. But the dead dark circle around the led dome shows that it isnít a great fit for the LED.
This is an example of a poor reflector. The surface is polished but the texture sends the light in all directions. And the dark circle again.
Here is a good clear lens but poorly positioned. The 4 dies in the center are mostly in focus but the lens is mounted too high and you canít see much reflection of the dies around the outer part. And a dead circle around the dome again.
Here is a really bad lens. You can barely see any trace of the dies anywhere and what you can see is all distorted. Unfortunately I donít have a good example of a 10w with a lens I wish one of the makers would do one and keep it available.
Here is just the wrong lens. The outer portion looks great showing the center of all 4 dies but the middle is completely dark.
This is why the reflector has a more difficult time with making a narrow beam. The line of sight off the dies limits them to around 50 degrees. It can only focus the light it can catch it around the sides.
Its hard to see here but this is a rebel with the 8 degree lens. From the front you only see parts of the die no dead dark spots at all. Thatís why these work great.
Here is the same thing off to the side a little. Already the die is hardly seen anymore and dark spots appear. This signifies that the lens creates a pretty narrow beam.
Here is a SSR90 with a good aluminum reflector setup. I took it out of a nice flashlight that made a pretty tight beam and was the right size. No dark spots here Every part of the reflector shows the die. With this setup and a blade with 6 feet of gift wrap butted up against the reflector it is a close 2nd behind a good lens setup.
Here is the same led with a good lens but poorly positioned. You can see a big ring around the center.
Here is a lens that I took out of a head mounted lamp. It is a good fit for the led and positioned well. No dead spots.
And the same from a bit to the side. You can still see a little of the die from the side but its almost gone. Not as narrow as the 8 degree but better than the reflector.
The SSR90 is the only led I have both a good reflector and lens for so this is the best comparison I can make. Here is the same lens as above but mounted in a blade holder shown on a wall. It is not super narrow, probably about 15 degrees.
Here is the reflector mounted in a blade holder shown against the wall. It does produce a good fairly tight spot. The down side is all the light not going in the right direction that appears as the big ring around the outside.
Here are the last two together. Showing the major differences. The green one with the reflector has a less even center with some hot spots. The blue with lens is more even. When light intensity is measured with a light meter. The hot spots are a ring around the center as strong as the lens center witch can work to our advantage. But the lens covers more area with high readings. I would guess the reflector is losing about 10% of the light to the side.
Due to our space constraints a lens has the potential to work better than a reflector. Like with the rebel the Carclo 8.7 degree is hard to beat. But it is very hard to find lenses or reflectors that can work good for many leds. So whatever fits best (less visible dead spots and more die) is best. Basically ether can work good if they fit the led well, have a smooth surface that transferís light well, and the light is dumped directly into gift wrap forcing it down the blade. And if you like more flair at the bottom of the blade there are more parts available to use or find.
So for those who have eliminated those dead spots please add the details of your solution to this thread with a picture if possible. Or if you can add more detailed information even better.