Need fine engineering help please! desperate (thank you)

[eatkabab]

Newcomers, please skip to post #87 on page 3 - Thank you
http://www.candlepowerforums.com/vb/showthread.php?t=286288&page=3

The following is a lamp I have developed for medical/surgery use. I'm just about finished creating it, but in testing, have realized that it must be about 15% brighter to be as useful as possible.

I cannot increase the package size, and have no idea what else to do to increase brightness. Lenses and machining are all custom work.

I will be eternally grateful to whoever can help me out. I would even go so far as to giving whoever helps me out one of these lights when completed.

Thank you to everyone on this forum and all your infinite wisdoms.

Edit:
Options that have been brought up (more discussion on any is more than welcome):
- TIR lens: might be a solution, but unlikely as these lenses do not provide sharp focus
- Lens coatings: a partial solution
- Having just one proper lens: I'm attempting to produce this
- Using a different LED: SST-50-W or OSRAM: New LED being used is the XRE
- Polish the bore from the LED to the first lens: possible gain, but will likely result in sloppy focus.
- Increasing current to LED: the complete casing cannot be increased in size and cannot get any hotter than it already does at 1amp
- Add heat-sinking fins and such: Do little or nothing due to small size requirement.

What has been established:
- A lot of light is lost with the current focusing strategy.
- For the application, there must be a very sharp delineation between light/dark at the edge of the ~13.5 degree focus beam (hence all the black on the inside)


Best possible solution so far:
Replace the XPG LED for an XRE LED. The XRE may provide less light, but its illuminated field is 90deg rather than the XPG's 125deg. The result should be more light down the center where its needed. Use a highly specific short focal length lens.

 

[kingofwylietx]

Depending on the led's angle of emittance, you may be able to pick up 10-15% by coating the internal bore between the LED and lens 1 with a reflective substance. This would be easy to test using reflective aluminum tape. If it works, you can improve on that with a more reflective substance or by chroming it. Try that (if that doesn't improve it enough, can you fit a reflector in there)?

 

[LV426]

I'll guess the driver is located externally, you'll ''just'' have to beef it up to 1.2-1.5A...

 

[eatkabab]

Depending on the led's angle of emittance, you may be able to pick up 10-15% by coating the internal bore between the LED and lens 1 with a reflective substance. This would be easy to test using reflective aluminum tape. If it works, you can improve on that with a more reflective substance or by chroming it. Try that (if that doesn't improve it enough, can you fit a reflector in there)?

I've tried numerous reflectors and have found that they don't work well with lenses. Doing the math, reflectors + lenses = a mess. That seems to be the case in reality as well.

I haven't tried chroming the bore, but I assume it will cause the same problems as a reflector. Of course I will try anyways.

Unfortuantely, I can't crank the amps up above 1A due to heat problems. Its only about 25mm long and 18mm diameter. I can't get any more heatsinking outta it.


I've read in other forums that the SST-90 LED may be more efficient at 1A. Is this true? Thank you for your advice

 

[entoptics]

Perhaps you could expand the external diameter by a couple mm, then mill the exterior with circumferential rings to increase the surface area? Essentially creating miniature cooling fins?

If you did this at the back, you could make it a little bit bigger still at the rear most portion around the LED and make the "fins" a bit taller, then step the diameter down to near original size towards the front?

Just an idea. Might get you enough heat sinking to step up your current enough for the brightness you need, without significantly increasing the size of the light.

 

[KuKu427]

Replacing the lens assembly with a TIR should help.
Or get coated lenses.

 

[Connor]

Like the others said, coated lenses will help. There's a 4% loss at each glass/air border.

One more thing: It seems the inside of your light is mostly black? Spray-painting it with a high gloss silver should yield a few more lumens as well. Especially your "black spacer" will eat up quite some photons.

-Connor

 

[IMSabbel]

If the diagram is at the right scale, you are wasting >75% of the lumens. The lens only fills a small solid angle from the led, while the XP-G is near lambertian.

Would a TIR optic not be better suited if brightness is a requirement?

 

[bigchelis]

The easiest is to put a TIR Optic...maybe the Surefire L1 type will fit.

You would gain as much as 50% more light just from that alone.


Then you could get a 1.4A driver from shinningbeam.com



bigC

 

[eatkabab]

Thank you very much for your responses. Something I failed to explain is that the light needs to have a very sharp focus. When you look directly at the light, it must be as dark as possible until your eye moves into the actual beam. This is the reason for the matte black outter ring and the black spacer. In my experience with this, using even a mirror spacer doesn't seem to increase the central beam brightness and only adds to the bright halo around the center.

Connor and KuKu427 said something about lens coatings to increase optical efficiency. What kind of a coating are you referring to? I'm actually using high grade plastic lenses.

 

[eatkabab]

If the diagram is at the right scale, you are wasting >75% of the lumens. The lens only fills a small solid angle from the led, while the XP-G is near lambertian.

Would a TIR optic not be better suited if brightness is a requirement?

I've realized this as well. We haven't looked into using TIR lenses. Can a TIR be used on the LED die and then also the lenses as well to provide the proper focus? Producing these lenses are extremely expensive. Do you know of any manufacturers that may already produce one that small?

Another option is using a different LED all together. Possibly an SST-50 @1a or OSLON OSRAM?

 

[Connor]

Connor and KuKu427 said something about lens coatings to increase optical efficiency. What kind of a coating are you referring to? I'm actually using high grade plastic lenses.

The 4% loss I mentioned is for *each* glass/air border. Plastic/air borders will have a (slightly) different loss.

Optical grade coatings are usually made of several layers of metal vapor deposits, at least that's what they use on things like photographic lenses etc.
Those vapor deposits are applied in vacuum chambers, which is a costly process. There may be cheaper/different processes available for plastic lenses - maybe you can get them readily made from your current supplier.

-Connor

 

[UberLumens]

You could try changing the material to copper, especially directly under the led the more heat u can pull away the better.

 

[eatkabab]

You could try changing the material to copper, especially directly under the led the more heat u can pull away the better.

There is a very small bit of copper directly behind the LED chip. The heat pull from the LED is very good. The heat-sinking is also adequate, the problem is that the light must be very small and light weight, therefore it gets very hot and can burn someone during handling (It will be handled while on). I cannot increase the size at all and we've tried adding all sorts of fins. They don't do anything significant but increase manufacturing cost and difficulty.

As far as I can tell (and some of you have realized as well), I am wasting a lot of light and need a more efficient light gathering strategy. If I could find a TIR lens that was cheap and fit perfectly, I'd be all over it (looking...). Another obvious option would be to find an LED chip thats a similar size but more efficient at 1amp... (still looking but not hopeful)

 

[bshanahan14rulz]

With a TIR, you'd be able to move the LED forward more, leaving more room for extra thermal mass. While the border between light and dark won't be as sharp, you'll have more lumens going forward.

May I ask what these are going to be used for?
Edit: oh, read in another thread, headlight for medical professionals.

You might also try out a few different tints of LED. If you have a few prototypes that you will be loaning to medical professionals for field testing, they might want something that makes the warmer colors pop out too, not simply more light. And I bet a TIR would work great for you.

Here's some manufacturers. After you find a lens you like, check with typical distributors to see if they have any. Cutter offers quite a few, and you can get some carclo stuff from newark and futureelectronics.

some links for your browsing fun

Carclo optics products page:
http://www.carclo-optics.com/opticselect/

Fraen products:
http://www.fraensrl.com/prodinfo.html

Ledil products:
http://www.ledil.fi/index.php?page=xp-g

khatod:
http://www.khatod.com/cms/general_led_lighting___home_page-1237430.html

 

[KuKu427]

If you need a sharp delineation between lit and unlit areas then a TIR probably won't do.
You should try to get coated glass or sapphire lenses.
http://www.edmundoptics.com/onlinecatalog/browse.cfm?categoryid=11

Please note that a 15% increase in overall lumen will not equal a perceived 15% increase in brightness.
Have you tried a single large lens placed closer to the LED? Might be more efficient than the two lens system you have now.

 

[Whineyweim]

Beg Cree for an S3?

 

[eatkabab]

With a TIR, you'd be able to move the LED forward more, leaving more room for extra thermal mass. While the border between light and dark won't be as sharp, you'll have more lumens going forward.

May I ask what these are going to be used for?
Edit: oh, read in another thread, headlight for medical professionals.

You might also try out a few different tints of LED. If you have a few prototypes that you will be loaning to medical professionals for field testing, they might want something that makes the warmer colors pop out too, not simply more light. And I bet a TIR would work great for you.

Yes this is a dental surgery headlamp. The goal is to produce a super cheap dental headlamp for the students at UCSF since the current ones on the market are ridiculously expensive.

To be honest, I believe that if we had one proper lens it would do the trick. Unfortunately, the manufacturer we're using doesn't understand anything I've told them and has produced maybe five terrible lenses. We've sunk plenty of money into this and don't really have much more to develop more lenses.

I believe someone talked about TIR lenses and brought a few to show us, but we quickly rejected them due to their inability to function as intended. Its just very difficult to get TOTAL internal reflection and if I remember correctly, the result is sloppy light that is difficult to focus further.

 

[the.Mtn.Man]

To be honest, I believe that if we had one proper lens it would do the trick. Unfortunately, the manufacturer we're using doesn't understand anything I've told them and has produced maybe five terrible lenses.

Sounds like you need to find a new manufacturer.

 

[eatkabab]

Sounds like you need to find a new manufacturer.

I wish! But we have little money left...