The Tuning Process of Reflective Apertures

A reflective aperture is a front surface concave, or dome shaped mirror in which an aperture effect is created (same thing as in a camera, a “hole” for light passage), along with a reflective effect occuring when a return image of the LED chip is in perfect focus back on the LED chip. The perfect focus occurs at R=1 with R being mirror radius. Since parabolas produce focal points further than R=1, they do not capture as much light. Also, radius is not constant in a parabola, so only part of the mirror can be in focus if this shape were used.

Our eyes are not good enough to see an image in perfect focus on an LED die surface to use the die itself as the only method for alignment/focus. At R=0.9 focus, or R=1.1 focus, you wouldn’t be able to notice that the image was slightly out of focus, since a die is so small, it will look identical and still like a clear square, but not all light will be collimated onto the die. Tilt of the mirror is a problem, even a couple degrees. Centering of the mirror is extremely important, as is mirror distance from the die.

Two methods exist for checking focus and centering of the reflective aperture. Once you have devised a method to mount and center the mirror, method one would be to check lux at the center of the output circle. The output spot is uncollimated, so wash is fairly smooth and even looking to your eye, but try to be sure things are lined up so the meter lands in the same place in the output spot on each test. You do not want other optics involved at this point, since it is another variable. Since the light output spreads rapidly from the aperture, lux would be checked using a highly repeatable setup (so that the test measure distance remains a constant), at a range of 1/4 to a 1/2 meter, before intensity grows too weak for accurate measurement.

Before you begin checking the lux though, the reflective aperture must be mounted, over and over to check height, until you know the exact real-value required. Centering should also be practiced with height adjustment, this is not done with lux reading, but a laser (coherent light source).

Centering and height (FL) must be checked by reflection. For this, I use a laser with small beam diameter (at the usage distance), mounted in a mill or CNC, using a digital readout in 100ths mm, or 1000ths inch, aimed down at the die through the aperture hole. The laser dot, green or red, should be used, with green being preferred, and not at a high power either (5mW to 8mW is more than sufficient). You must be able to observe the effect of return reflection of the laser while aiming it into the aperture hole (wear safety shades, this is bright), which is far easier than viewing the return image of an entire LED square while moving the mirror around. Since it is a concave mirror and not a flat mirror, the reflection image jumps to the opposite quadrant of the die. If a tiny needle-focused laser is used, and -X/+Y quadrant corner of the die is struck to begin, the same image will appear in the same location on the +X/-Y quadrant of the die if mirror is aligned right. If the aperture mirror is centered, the laser can get extremely close to touching its return reflection at the die center until two dot halves exist, but the halves can never touch each other in reality—an imaginary boundary line will exist neither reflection can cross. If the images cannot butt up against each other at the die center like this to make a virtual appearance of one single dot when the two halves meet, but rather a line gap of area on the die exists where the two beams cannot meet but may come close, the die is not at the correct focal length from the mirror. If the input laser dot is tight and crisp on the die, the second returning dot should be of equal size and shape/look (again, in exact opposite die quadrant position). If the input laser dot is crisp, and the return beam strikes the die but does not look of equal size but larger and more blurred, the die is at the wrong focal length from the mirror. If these previous details can simply never be met no matter at what height or centering position, this means the mirror you are using is not capable of working effectively, either due to curvature being poor or wrong, or surface being non-optical grade, such as bare metal, which will highly distort a laser reflection typically. If the mirror shape is a few percent off in some areas of curvature, it may look like a great mirror to the eye, but at the macro scale of actual use, it is probably highly inadequate. This is why optical grade surface quality is the most important feature of the mirror.

When these things are done right, lux will approach 80-110% of original LED intensity, and nearly all available excess light will be used to produce the return image on the die.

I have created a 3-axis adjustment spacer for my mirrors, so that I can make minute adjustments via set screw, laser check the adjustment, and when I feel I have reached the closest adjustment I can using a laser, I then test lux for the final, extremely small adjustments. These small adjustments account for another 10-25% intensity gain depending on the LED. Also, when lux testing is initiated, the die should be powered by an accurate DC supply at a constant current, being sure conditions are repeated and heat sagging output is not occurring during the test too quickly, which would be creating another variable to deal with. So, lux should be checked quickly after LED power-on. If the supply is not highly accurate, it may make sense to run the LED at bumped up wattage, to minimize supply variance per test. Intensity should never be checked with batteries when lux testing, or in a light that has rapid heating taking place, therefore it makes the most sense to test lux at very low, consistent wattage levels just high enough to obtain some lux reading that is comparible (200-300 starting lux for example). Move the LED closer to the meter if you want to run even lower LED testing wattages, just be sure a spacer is used between them. Do test maximum lux possible first before adding the mirror, and maximum lux to end with, to realize actual total gain in usage conditions.

Since gain can reach 100% or more, gains are simply massive, and there is no reason not to use one of these aperture types, especially if your goal is maximum throw. As I say, it’s like moving 10+ intensity bins into the future, and many jump when only one higher new bin becomes available (I.E., U3 to U4). Just remember that adjustment is everything, along with mirror material/grade. Similar gains can be seen with a dome still on the LED, but this makes alignment much harder and more time consuming, as you must work through a lens instead of open air. With the dome, no the gains will not be as high, but they can still get way up there.

I hope this helps some figure it all out. Producing the mirrors is far more effort and labor, and requires careful glass grinding.

Very thoroughly detailed explanation of a process very few could pull off successfully. Thank you. That really helps in understanding the lengths taken and materials used to achieve results beyond, far beyond, the normal possibility. I, for one, really do appreciate the intense application of time and labor to achieve this result.

I will now return to scrubbing the toilet where I belong. :wink: :slight_smile: lol

I know that MEM is 3D printing the holders for the lenses, and that he produces holders in a few thousandth’s of an inch increments until he gets it “perfect”, even printing 8 or more for a single lens, and then using a double lens arrangement. So it’s painstaking exacting work he’s doing to squeeze absolutely every last flicker of light out the front.
I also know he’s buying pretty expensive optics from a top manufacturer. It’s not a budget mission, this.

Edit: I will definitely be showing beamshots of the D80 he is working on for me, but I will NOT be disassembling it. We have discussed him sending along one of his even stronger thowers for a beamshot attempt at a 2 mile distant target. Wouldn’t THAT be interesting? :wink: I haven’t done the math on what that would take, but easily well over 1Mcd, well over. (Yes, well over 1 million candela.)

Edit II: It would take a 2.59Mcd lux reading to do 2 miles, for the record.

Well, I can imagine lots of reasons why someone would want to buy his “technology” in order to use it in their products. But, why would anyone want it to never be implemented? The existence of this “technology” doesn’t hurt anybody’s business. It doesn’t favor one manufacturer over another. It is an enhancement across the board. There are no losers with light recycling. So, what are you talking about? Also, he has already shown some photos of his work. Try using the search function.

Intensity gains, not output, that’s the same concept a commercial company names Wavien used for their RLT product if i understand it well enough, tuning is obviously critical and seems to be where MEM directed his efforts.

The principle is simple. Most of the light produced behind an aspheric lens is wasted. It either never reaches the lens or hits it at the wrong angle for throw. A well made and properly focused reflective aperture recycles the wasted light back onto the die, so that it can have a second chance at coming onto the lens at the correct angle for good throw. Since it is most of the light that is under the influence of the reflective aperture and otherwise would not contribute to throw, it should be easy to understand how this process can bring throw gains of 100% or better. For a real life example used in industry, look at a digital media projector bulb. The design is a little different, but the process of light recycling is the same. MEM’s “technology” is that he applies this to flashlights, and meticulously tunes it to get the greatest gain possible.

interesting wall of text.

i’d love to see a example of this.

Well said David. I think it boils down to elbow grease.

There are those that don’t believe the outputs of some of my creations, and I understand why… I have a very poor time sense so when I’m working on a light the amount of time involved is of little consequence to me. I work very hard to eliminate resistance at every possible point and get the most output from an optimum emitter and top cell combination. The cost of materials is not to be taken lightly, budget mindset cannot produce optimum results and I don’t usually look very hard at the cost of the items I use. I believe MEM does this same kind of labor intensive work in the fine tuning of his optics and the cost of the materials.

Zero tolerance, it’s a nice term but an extremely difficult thing to pull off. Most people probably just don’t have the time or inclination to go to these kinds of extremes.

Anyone using silver wire instead of copper for bypassing? OT

Interesting concept Westin, but why? Silicon covered copper wire is already being used in most cases to wire up the emitter, with the span being short enough that any potential gain would be so minimal as to be difficult to measure. I prefer to use a slightly coiled insulated wire inside the spring over the more traditional braid, for durability and safety. I’ve seen braids break and flop around loose, whereas I’ve not seen this happen with a silicone insulated wire.

Braid is designed to be a wick, so it’s difficult to solder to the spring without the braid sucking solder into it’s weave as it was designed to do, making it stiff and inflexible which leads to that breakage of course.

Silver wire? Well if you have some already, you could give it a go, see how it holds up, but I wouldn’t think it would be prudent to go out of the way in purchasing some for this application. Just my 2 cents, for whatever that’s worth.

With the precisely tuned RAs that MEM is apparently making, 2.59Mcd is achievable with a reasonably sized light. A dedomed XPG2 can have a luminance around 190cd/mm^2 at 4.5A. As I understand, a RA can roughly double that. So it would take a lens with an area of 7194mm^2 to achieve 2.59Mcd, or about 96mm in diameter.

I don’t understand one thing , just cant get it on my mind . What do you mean by “double lens arrangement” ??

Found some pictures in Wavien patent here:

Extremely cool! Extremely exciting! What is the “world” record meter reading now?

I don’t think a mirrored collimator (such as the wavien collar style) is used in the dual lens set-up, instead, the first optic is placed very close to the de-domed emitter, gathering light in a pre-focus to allow the outer larger aspheric a tighter incoming source such that it’s outgoing is cleaner and more defined. If I understand it correctly, this results in a larger hot spot with a higher percentage of collected lumens. Effectively, a high quality precision ground glass element is replacing the dome on the emitter as the first in the 2 optic set. Where a typical aspheric has large losses in lumens output, this 2 lens system regains much of the original capability of the die.

The use of the mirror is for a very targeted tight beam profile where extreme throw is required. Fairly sure this is used in conjunction with a single aspheric as it blocks the outer peripheral losses that would normally be cast into a reflector for collimation into the central hot spot. By recycling this outer (low angle) emissivity, the die is more efficient at directing light directly into the aspheric.

MEM is doing both, depending on the host used and the target goal of the beam profile.

I will again remind the reader that I am extremely forgetful, either totally losing information or sometimes getting unrelated information mixed up, so my take on this is unreliable.

I can’t beleive it took almost ten (10) months for someone to see this and reply to it. What a great read.

Pretty sure I saw it back then, but wasn’t interested enough at the time in aspherics to comment on it. And then forgot about it. I am now playing with a few aspherics for a long range sword to cut the darkness and as such, this has taken on new meaning. :slight_smile: (And I’ve been talking with MEM while he is working on my D80. :smiley: )

Learning curves are steep for me, as my fishnet trap of a mind rarely holds all of anything I take in. :wink: I know I joke about it a lot, but it’s due to a medical condition and the ensuing meds I am required to take so there’s not a lot I can do about all the “burned bridges”.

For example. I DID remember to use the 2 components required to enable moon mode on an LD-2 driver, but when it showed only 3 modes I couldn’t for the life of me figure out why. I hunted down the original thread from led4power and found that I have to enable moon in the firmware after modifying the driver with said components, now it works like a charm. lol Sometimes even things I do on a regular basis I forget details and it costs me time and effort hunting down where I went amiss.

Why did I say all this? Because MEM has a way of spilling vast amounts of information and it’s quite challenging to take it all in, keep it, and recall it intact.

viperbart, ’tis your fault, sir :smiley: You did mention reflective aperture in the other thread so… :wink:

I would love to see some pictures, though…. MEM, when you finally have some time, any chance for some pics?

I’m not sure which parts you disagree with. I may have been a little liberal with some of my numbers. The luminance of a dedomed XPG2 has been measured to be as high as 179 cd/mm^2 (~540,000cd in a UF1504 which has a lens area of 3019mm^2). There is less data on RAs. I remember reading somewhere on the forum that MEM’s RA can increase the luminance by a factor of 1.8.

An RA is just a spherical hemisphere that is reflective on the inside. The LED is located at its center. A hole is cut in the hemisphere right above the LED so that light can escape towards the focusing lens. The light leaving the LED to the side hits the RA and is reflected back to the LED surface where it is diffusely reflected or converted again. So some of the reflected light, which would have just been wasted, is focused by the lens into the beam. This process increases the LED luminance.

It is not even so complicated to make a (rough example of a) RA. I bought a 1/8 tsp. stainless steel measuring spoon whose spoon part was roughly spherical. I polished it with a range of sandpaper grits, cut a hole in it, and put it over an LED. I measured the lux directly above the LED (45cm away). Current was controlled using a current controlled power supply. I got a factor of 1.2 improvement in lux when the RA was properly positioned. Since the LED area stayed the same, the lux increase means the luminance of the LED increased by the same factor. Stainless steel is not the ideal material since its reflectivity is only ~0.6 (paper). With a more reflective material along with a more precisely shaped hemisphere, a 1.8x increase in luminance is believable to me.

It seems to me you are being willfully ignorant. A healthy skepticism is good, but it seems you are not making any effort to understand the concepts presented here, and you are not asking questions that might help you understand.