Does Jetbeam use real sapphire crystal lens?

[EngrPaul]

Re: Lens

I ordered a UCL lens from flashlightlens.com

28.6mm x 2.84mm with blue AR coating and 99% transmission.

A little bigger than stock, but it appears there is enough room. If it works out, the original lens will become a backup.

 

[orcinus]

is there any way of asking jetbeam and getting a real answer instead of speculating?? - someone must speak chinese - or know someone that does.

What speculating?
If a lens should weigh X grams for a given volume and it weighs Y grams, then it's not made out of advertised material, period. :shrug:

 

[EngrPaul]

The density of sapphire is 4.0 g/cc. Glass is about half that, 2 and change.

That's a broad enough difference to be sure with a simple scale and calipers.

FYI - The density is the weight of the glass, divided by the the volume of the glass. The volume is calculated as: (pi/4)*(diameter^2)*(thickness)

 

[EngrPaul]

Re: Lens

I ordered a UCL lens from flashlightlens.com

28.6mm x 2.84mm with blue AR coating and 99% transmission.

A little bigger than stock, but it appears there is enough room. If it works out, the original lens will become a backup.

I just got the lens. It fits great, nice enhancement to the light!!! The gap between the bezel and head is a little bit more, but now there's room for a subtle GID ring. :tinfoil:

 

[Zatoichi]

I just got mine yesterday, and reading this got me thinking. What I've gathered hanging around watch forums for they last year or two is that 'saphire' is much more scratch resistant than mineral glass (that seems pretty much established), but mineral glass is more impact resistant.

Given that the Jetbeam III m's lens is pretty well recessed, and that mineral glass isn't that easy to scratch, impact resistance may be a more valuable quality in a military type light. Just a thought.

 

[The 8th Man]

Went on Jetbeam's site today and this is what it says for the Jet III M \

Model: JET-III M
LED: CREE 7090 XR-E (Q5 bin)
Max Output: 225 Lumen (Torch Lumen)
Reflector: aluminum reflector
Lens: coated mineral glass
Material: T6061 T6 aircraft aluminum alloy
Finish: HA III Military grade hard annodized
Battery: CR123*2,RCR123*2,18650 Li-ion
Input voltage: 2.7-15V
Switch: Forward clickie switch
Waterproof: Accord to IPX-8 standard
Dimension: Bezel diameter 33mm, Tail diameter 25.4mm,
Overall length 138mm
Weight: 118g
Patented Product.

This should really put it all to rest.

 

[deusexaethera]

Two thoughts:

1. Since optically-clear glass is a synthetic material, I'm pretty sure that all sapphire/lead/whatever-crystal glasses are also synthetic materials.

2. 6-7% reduction in output is a small price to pay for a lense that can all but stop a bullet. UCL just isn't strong enough by comparison; I've had UCL lenses crack in half just from tightening the bezels on my Maglites. (No, I was not using a pipe wrench.)

 

[GarageBoy]

Uhh Sapphire is more brittle than mineral glass...and thus shatter more easily (harder though, so it won't scratch)

 

[bluepilgrim]

For my sort of use, I'd say, so what if the glass cracks if you screw it down too tight -- don't screw it down too tight -- it should be a rare occasion. And so what if it gets a bit of a scratch in it. I can always put a new glass in it, although a scratch should not bother the beam or brightness that much. But the transmission is something which affects the light every time I use it, in it's normal function. As such, I think that's generally the most important factor.

The key issue here is if you are getting what is advertised, which you should.

 

[deusexaethera]

In theory, yes, but as long as the lense is there I want it to provide adequate protection relative to the cost of the light itself; just because it's transparent, I don't want it to be the weakest point in the design. Needless to say, I was very impressed with the thickness of the sapphire lense in the Arc6.

Just wait til you discover the power loss through a car's transmission. You'll be crying on the floor over that one, if a few lumens pisses you off.

 

[bluepilgrim]

I know that auto transmissions are not efficient. On the other hand, neither is lighting, compared to electric motors which have efficiencies into the 90%s -- I wish I had a light that even 1/3 that good.

The way I've always used a light I don't I need much protection beyond keeping it clean -- I can't remember ever breaking a lens but once, although sometimes they were mysteriously misplaced. But then, I never hit people with a light, which seems to be almost a hobby among mag owners and tactical people :laughing: -- it depends on how one uses a light, of course.

For me, just a cut out piece of blister-wrap plastic or cellophane has done well at times for strength, or nothing at all for an old incandescent. I'm not sure how it would be likely for something bump into the front of a light, as opposed to a blow on the side of it. It's getting dirt inside I'm more concerned with, and the reflective loss even with a thin film with good transmission.

The other problem with a high power light is that reflective loss can mean heat buildup, but then you need a heat resistant lens too. I'd be tempted to just leave the lens off in that case -- all the better for cooling by convection.

 

[deusexaethera]

I guess I can't say for certain that LEDs are that efficient, but I suspect they are, or at the very least they are more than 30% efficient as was your implication. I regularly see LED bulbs as replacements for household incandescents that use ~1/10th of the wattage, yet produce the same amount of light; if a regular lightbulb is a little less than 10% efficient, then that means that LEDs are very nearly 100% efficient.

 

[Zatoichi]

I regularly see LED bulbs as replacements for household incandescents that use ~1/10th of the wattage, yet produce the same amount of light

I haven't seen these in the UK yet. CFL's are common, but I've only seen LED's used as decorative lighting in homes and shops etc.

 

[bluepilgrim]

LEDS are generally more efficient than incandescent -- although not necessarily so -- but that's saying much because none of the lighting sources are real great. I guess part of that is that they all emit a wide spectrum electromagnetic radiation but we can see only a small part of it: IR and UV is wasted as far as our eyes are concerned. Much of it goes into heat, of course.

http://en.wikipedia.org/wiki/Electric_motors
"Brushless motors are typically 85-90% efficient, whereas DC motors with brush gear are typically 75-80% efficient."
(But better, high-efficiency, are available.)

It surprised me to see how inefficient LEDS are after reading all the hyped advertisiong about them. Better, but no panacea.


You have to go to the wiki site to see the full formatted table -- it didn't copy over properly (and there is more information there).

http://en.wikipedia.org/wiki/Lighting_efficiency#Lighting_efficiency

Overall luminous efficacy Overall luminous efficiency

(lm/W)Overall
Combustion candle 0.3 [6] 0.04%

200 W tungsten incandescent (220 V) 15.2 [9] 2.2%

photographic and projection lamps 35 [13] 5.1%

Light-emitting diodewhite LED 10–100 [14][15][16] 1.5–15%

low pressure sodium lamp 100–200 [24][25][9] 15–29%

Theoretical maximum Green light at 555 nm 683.0021 100%

 

[jzmtl]

How did you guys manage to turn a thread about sapphire window into automatic transmission, electric motor and incandescent light bulbs?

 

[deusexaethera]

bluepilgrim, LEDs don't emit wide-spectrum EMR; they emit the specific frequency they are tuned for, and nothing else.

The way my physics professor explained it to me is, if you could broadcast a signal from a radio tower at a high enough frequency, you would see it as visible light, but the problem is it's impossible at this point to make a frequency tuner that can oscillate the electrical signal that fast. The crystalline structure of LEDs, however, does that by its very nature, so they are in effect "broadcasting" visible light exactly like the radio-tower example I just gave. White LEDs do this too, but they also have yellow phosphors added to absorb some of the blue light and re-emit it as yellow light.

Presumably, if you cooled an LED until the silicon turned into a superconductor, it would be 100% efficient. At room temperature, however, there is inevitably some heat generated by electrical resistance, but nothing compared to what incandescents or even fluorescents create. I challenge anyone here to run an Arc6 and a comparable incandescent for 5 minutes straight, then touch the emitters directly.

No takers? Hmm.

 

[deusexaethera]

How did you guys manage to turn a thread about sapphire window into automatic transmission, electric motor and incandescent light bulbs?

It's a skill I have. No topic is unrelated to another topic, and I see no reason not to talk about them as well. The original point was made, so it doesn't matter anyway.

 

[bluepilgrim]

How did you guys manage to turn a thread about sapphire window into automatic transmission, electric motor and incandescent light bulbs?

Well --- everything is related: in particular this is related by efficiency of saphire glass as opposed to UCL lenses, and the background information. Strength of the glass is not the only design consideration. (This comes up with reflecting vs refracting telescopes too, with reflecting being more efficient since light is lost in an objective lense -- as well as other design factors.)

Non-LED lights also have to contend with light lost in lenses, of course.

 

[bluepilgrim]

bluepilgrim, LEDs don't emit wide-spectrum EMR; they emit the specific frequency they are tuned for, and nothing else.

My understanding (from what I've read so far) was that they emit UV which then excites the phosphors (unless they are red LEDS, green LEDs, or the like) -- but I'll have to look into that more.

I see what looks like good material at http://en.wikipedia.org/wiki/LED but it will take me a while to digest it, follow the links, and check it out elsewhere too. This gets very complicated very quickly -- but I see just from a quick scan of that link, and the article on Stokes Shift that white can be produced in several ways). I haven't found much information in the form of tables about LED or glass absorption efficiency yet -- the practical stuff, as opposed to general theory.

When I look at a white LED through a spectroscope I see a continuous spectrum -- similar to an incandescent and much different that with a flourescent which shows a distinct series of bright lines. That may be due to the nature of the phosophors more than the LED? In any case, the efficiency is not that good.


In the meantime I found some interesting material abuot lenses (a bit dated) at http://www.molalla.net/~leeper/flashlen.htm -- and see the main page too (link at the bottom of referenced page).

 

[HKJ]

LEDS are generally more efficient than incandescent -- although not necessarily so

The only leds that can not exceed incan by 3 to 4 times in efficiency are very old leds or comparing to bulb's driven at the edge of bursting (There led are only twice as efficiency).