BLF recoil über-thrower

BLF Special Edition Products
148

Ok here we go, several things. First of all, I would like to point out that this is why djozz's images showed that spotlight with the center blocked out projected a concentrated point instead of a ring of light:

This is how you get a high lux reading, not high throw, past that point at the left the rays diverge and you end up with no good beam.

Next, this is the light rays coming from the focal point of the parabolic lens. This is how you get maximum throw, all light beams collimated. Please ignore the half dozen other reflectors in the bacground, those are inactive.

This is just the 9" mirascope reflector (green) being used. 9" diameter, 1.5" depth.

Now, this is how I test beam divergence. The origin is offset 2mm from focal point, so this is the light coming from the LED at the greatest possible offset angle (in this case it would be an XHP70 which has about 4mm side length)

Ok, now let's take a look at what happens with small vs large reflectors. First the 9" mirascope, then a larger 35" reflector, similar to what is used in the old military searchlights.

As you can see, the larger reflector has much smaller "skew" due to the offset. This means the light that is not coming from the middle of the LED, eg. the edge, still gets very well collimated.

This is because even though the two mirrors have the same curvature (and collect the same 120 degrees of light) the larger lens is farther away (because of a longer focal distance)

So the light rays coming from the center of the LED, vs the edge of the LED, have a much smaller difference angle when they hit the reflector, and are bounced back also at a much smaller difference angle.

This is why for long range lights, the size of the light source matters a lot. Instead of using a huge reflector, you can use a smaller light source and get also a huge amount of throw.

This is why the maxabeam uses a 0.25mm short arc lamp. Even though it only makes a few thousand lumens, it can reach many kilometres with only a 8" or 6" reflector or whatever it uses (i forget).

Lesson is, the light needs to be going straight forward to be collimated, not like the first image, that is bad. That is what you use for burning paper and matches, not for lighting up kilometres away :D

149

Interesting, looks like a neat program. Thanks for posting the pics; this has aided in my understanding of the subject.

One thing that I’ve been thinking and now can put better into words: for smallish reflectors, focusing at 5 or 10m makes a beam that is practically close to collimated. For example, consider a 40mm reflector with an XPL HI that is focused at 10m. The divergence angle from the focus not being actually at infinity is 0.002rad [inverse tan(.04m/(2*10m)]. This would cause the beam to diverge an extra 20cm at 100m, which is a small amount. In particular it is small compared to the beam divergence that exists as a result of the LED size, which is approximately 0.06rad.

So while what you have been saying about reflector focus is true, for most lights that aren’t huge, focusing at 5 or 10m results in a practically collimated beam.

150

Yeah, this kinda only applies to large reflectors like the ones in searchlights, and also to an extent the 6 or 9" reflectors of mirascope size, not the kind of flashlight you use to light a path or carry in your pocket.

If you're interested and have a few days to learn a new program, the optical ray tracer is free to use :) http://arachnoid.com/OpticalRayTracer/

The hardest part is taking manufacturer given height and diameter and putting those in the program by adjusting the parabola radius, since focal point of parabolic reflectors is not given often unfortunately.

But yeah, this program helped me find a good lens setup for my thrower flashlights and is pretty awesome!

151

Hey guys,

Just got my mirascope in, and as a mirascope it’s not impressive, at all…
The mirror surface is a bit messy unfortunately…
But, a quick test with an XP-E2 light looks kind of hopeful none the less.
This evening when dark outside i will see if it’s worth working with or just a waste of time and money.

152

Another benefit of large reflectors is that imperfections/aberrations have less effect on the beam ;)

Like, look how ugly this is, yet it still throws several kilometres xD

153

Meanwhile it got dark outside, so i can do some beamshots.
I placed a ‘screen’ in the garden, will be projecting out the window. :slight_smile:

154

Nice setup!

155

Oh, I am SO looking forward to this! :wink:

156

Well, i’m eating now, i tried some stuff, and well, it works, but…

Beamshots will follow later…

157

I have to admit, I didn’t think this idea would be taken to this level. Great to see people really putting the effort into something new!

158

Okay, some beamshots then:

And compared with Jacob A6:

I should have used a tripod…

So with the same power it seems to throw more light in the right direction than an A60.
This was only 10 meters distance to the screen, so i’m still not sure what it will do over longer distances.

Quite a bunch of anomalies around the hotspot, which seem to come from the outer perimeter of the recoil reflector.
Will do some more pics later to investigate further.

159

What bin XR-E and XP-E are you using? I’m wondering how much of the difference is from the emitters themselves. Or, possibly, the difference in emitters could be working the other way, depending on bin, so the difference from the reflector set-up might even be more than shows in the pics!

160

I have no idea what bin those LEDs are.
The XP-E is from a SingFire 348, so probably nothing special, The XR-E is how i bought the Jacob.
I was assuming it would be similar enough.

161

Sweet.

What's the diameter of the spot?

Is this focused to a point or focused to infinity (collimated)?

162

Dang, camera battery empty…
I’m trying approx. 20 meters now, but either way, this thing does a nice job throwing in the good direction, but a better reflector would have been considerably better, i think…

163

The spot @ 10 meters is approximately 50 cm in diameter.
This is a compromise between collimation and focussing, it’s “the best it can do” so to speak.

164

That is a 1 degree half angle beam divergence, very good for a toy reflector! :)

Do you have a luxmeter to measure?

165

Hmm, when you put it like that, i guess it’s not too bad. :slight_smile:

No i don’t have a lux meter (yet)
I thought i’d compare it with a known light: the Jacob A60.
The recoil setup seems to outthrow the Jacob hands down, which is not bad either.

166

By the way, the XP-E is soldered on a 1.8 mm diameter copper wire, and it seems to be enough for about 1 watt.
Cools better than i expected.

167

Hmm that's alright I guess. Maybe look into buying one in the future if you're into flashlights a lot, I got one for $50 a while ago and it has been extremely useful.

For myself, I also contacted a company that makes real reflectors, and it's like $700-1000 for a nice 16 or 20" reflector xD a bit pricey!