tight beam with 7xml possible?

[dexter9]

Hello guys,
Is it possible to get a tight beam with 7xml and that lens?
http://www.led-tech.de/en/High-Power...2_120_117.html
http://www.led-tech.de/en/High-Power...tml?cross=1730

By tight i mean DIR style, or close to it.
If not, what other high lumens alternatives do i have? i'm building this for a friend and i dont want to see him disappointed.

[jspeybro]

usually the 7 xml optics are pretty floody, but I must admit this optic looks interesting.
The angle is 12° at 50% FWHM, so it is probably not as tight as HID lamps, but certainly usable I think.

[ThomasDK]

Hi

I build a dive light with 7 Xml , and I got a tight beam using a lens build for the mc-e led and putting a small o ring under the lens to lift it a little bit above the dei, and that gives a wary tight spot using a 20mm lens, the lenses I found


build for the xml is all bigger and I wanted to build a small handy light. The lens I used was this one http://www.cutter.com.au/proddetail.php?prod=cut819 the rs model.

Hope this was useful to you.

[DimitrisV]

Very nice build

Do you have any beam shots

Thanks
Dimitris

[ThomasDK]

I have this shot, it is not wary good it is a bit difficult to photograph 6000 lumen my camera keeps telling me that I am photographing against the sun, but it is great for diving in the low visibility water we have where I live.

[Packhorse]

No offence that pic does not tell us any thing.

How about you put the light at a set distance from the wall eg 2 meters. Then put a ruler or other known length object agaist the wall as well.

Set your camera to manual mode and choose a high shutter speed.
Then measure the width of the central beam, and the wider spill beam. From this ( and knowing the distance from the light to the wall) we can calculate the real beam angle.

[ThomasDK]

Sorry

I am new to this forum and don’t know how you do things I do not have the opportunity to take an image right now but I tried to measure the bright spot from a 2 meter distance and it gives me a spot of 75 cm I know this is not as tight as the HID lights, but when diving with my body how has a 21W hid (Halcyon) And he tighten his spot we have just about the same intensity but my spot is a lot larger, that gives me an advantage when diving in low visibility, but he can signal longer when we dive in high visibility, I will try to make a beam shot as you described next week.

[Packhorse]

By my calculations that makes it about 21 degrees full width beam.

2 meters x 2 x Pi= 12.5 meters circle diameter.
Your beam covers 0.75 meters/12.5meters =0.06
0.06x360degrees =21degrees

[lucca brassi]

In water must be even wider because the water is optically denser

[ThomasDK]

Hi

The calculation seems high given the spec on the lens says +/- 4 deg., but I am no math genius so you might be right.

How is this spread compared to what you have done, I have tried a lot of different setups, I tried reflectors but to get a decent beam I needed to go up to at least a 40mm wide reflector I (tried the 20 mm) and with 7 led's that would be a unhandy lamp. I also tried a 100w plate led with a aspheric lens and that looked very god on land but when I got under water it was like driving in fog with the high beams on. This is the best result I have gotten so far there is almost no spill in the beam I have a decent area with light and a decent range, the only thing I miss is the ability to signal over a long distance in clear water I am thinking about making the lamp a little bigger and then putting a 40 mm reflector on the center led and keeping the 6 others with lenses.
But if you have any better ideas I would really appreciate to hear them because I am a bit stuck.

[jspeybro]

based on your measurements of a spot of 75cm on a distance of 2m, the angle is indeed 21°.
in excel, =degrees(atan((75/2)/200)), this gives you the half angle. Multiply by 2 to get the full angle. However, with this measurement, it is unknown if this is measured at half maximum.
I checked the profile of the the spot and it seems more or less at half intensity when you just look at the entire bright spot.

1 reason that this is high compared to the spec, is because you use a different led compared to the specs. Another source of error could be rounded figures.
Also, it is possible (and most likely) that the ±4° is for a single lens and not for the entire lens assembly. I say this because the profile of the light gives a hotspot in the center (about 130 pixels wide which would correspond to about 29cm), then lowers significantly to about half intensity (which is the 75cm) and then slowly further down.
If I calculate the angle of the central hotspot, I actually do get 8.3° (full angle, so ±4.15°) which is close to the spec of Cutter. If you look in the datasheet linked on that page, you get however quite different numbers which are much closer to the measurements.

Having intensity changes in 3 steps is a bit unusual for a TIR optic so it seems to me that the optics are alligned perfectly parallel while you would get a better spot at a certain distance if you would change the angle of the outer optics (including the led) to allign the spot with the center optic.
You can probably verify this by blocking al but 1 optic of the assembly.

anyway, never thrust angles given by others than the manufacturer and always check the datasheet. Given the datasheet numbers and the fact that the OP wants to use XPG's, the optic from polymer optics seems like a reasonably good one.

Johan

[jspeybro]

Dexter9, just noticed that the optic you link to is for XPG and other XP-series leds, so this probably won't fit XML's...

[lucca brassi]

maybe works with LLC49R

http://www.cutter.com.au/proddetail.php?prod=cut1275 full angle 6,6° but you need costum PCB and probably head would be too big

[ThomasDK]

Hi Johan

Thanks for your explanation, I have taken 2 new images with a camera where I can set the exposure time and this give me a totally different result, the first image is the original lamp with cree mc-e led’s that fit the lens and the second is with the xml, as you can see I think my old camera was over exposed as you noticed the hot spot is only 30 cm from 2 meters this is more what I expected, and there is a little les spill on the xml that is also the feeling a get under water.

[jspeybro]

your image is still overexposed in the center... but the profile looks indeed better and closer to the specs.

[dexter9]

The leds and the driver arrived yesterday and i tested them.
The beam is about 20 degrees with lots of spill, narrower if i increase a bit the distance between the leds and the optic.
It's clearly not a dir style beam, but, it sure is ideal for night diving on a reef/wall.

[ThomasDK]

Hi Dexter

I placed a small O-ring under the lens to give the tight spot, I just got back from a diving trip to Norway where we did some 70 meters dives where it was totally dark but in clear water and here the light was perfect we could throw light as long as we could see and we got a large part of the wreck lid up.

[dexter9]

It's all done.
The beam is about 21 degrees with lots of spill.

[dexter9]

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