Need fine engineering help please! desperate (thank you)

[saabluster]

I actually already ordered a slew of lenses from Surplus Shed. Also talking to them for a minute, I learned how great of people they really are. Wonderful customer service.

So my current setup that will be arriving soon is the XRE R2 with a 12mm focal length lens.

On the XPG that I have, it seems a 15mm focal length is perfect, and a 10mm focal length is about 4X the necessary size. Since the XRE die is exactly half the size, a 12.5-13mm focal length should give me the 10deg viewing angle I desire.

I would be very wary of using Surplus Shed if you have very many of these to make.

You should know that although the XR-E will give you the best performance as far as brightness is concerned it will also come with a built-in halo. My suggestion is to use the R3 bin XP-E assuming CRI is no concern for this project. If you would like to talk about your setup just send me a PM with your phone# and I will give you a call.

In that photo where you are holding the lens about 14mm from the LED, what is a good estimate of the % light lost that never reaches the target due to the very wide dispersion angle of the LED?

Is it here where a pre-colimator lens could "capture" some of this wasted light?

Judging from his remarks it seems he is going for lux not throughput so the pre-collimator is unlikely to help with his setup. That said it depends on the quality of the lenses he is using.

 

[eatkabab]

In that photo where you are holding the lens about 14mm from the LED, what is a good estimate of the % light lost that never reaches the target due to the very wide dispersion angle of the LED?

Is it here where a pre-colimator lens could "capture" some of this wasted light?

While using the pre-collimator would definitely help in that sense, it also introduces so many new angles of the light that cannot be focused. There must be a very sharp delineation of bright/dark (the focus must be very sharp). In my experience, lenses are designed for and work best with point lights rather than light coming in at all directions...

 

[saabluster]

While using the pre-collimator would definitely help in that sense, it also introduces so many new angles of the light that cannot be focused.

It doesn't affect how well it can focus. It just allows you to gather up more light and send it out. Focusability is the same or better. However even though more light gets out the intensity will be about the same.

 

[ama230]

Here is a site with cheap prices on optics and there are many for the xp series including your xp-g and there is all types of finishes and coats to the plastic to get the diffusion right.

http://www.cutter.com.au/products.php?cat=30&pg=2

just type in xp optics in search as they have tons...

 

[eatkabab]

Here is a site with cheap prices on optics and there are many for the xp series including your xp-g and there is all types of finishes and coats to the plastic to get the diffusion right.

http://www.cutter.com.au/products.php?cat=30&pg=2

just type in xp optics in search as they have tons...

I've actually tried every variation of these TIR lenses made just for the rebels and XPG's. They don't perform as advertised (or I might just not be understanding the advertised specifics). They may be good for crude applications, but unfortunately not for mine.

 

[eatkabab]

My suggestion is to use the R3 bin XP-E assuming CRI is no concern for this project. If you would like to talk about your setup just send me a PM with your phone# and I will give you a call.

Thank you so much for your extremely generous offer. I messaged you but I'm not sure if it went through since I cannot find a "sent PM" folder in this sites forum system...

 

[saabluster]

Thank you so much for your extremely generous offer. I messaged you but I'm not sure if it went through since I cannot find a "sent PM" folder in this sites forum system...

hmm.. no PM is showing. Try shooting an email to omglumens at gmail dot com.

 

[MikeAusC]

On the XPG that I have, it seems a 15mm focal length is perfect, and a 10mm focal length is about 4X the necessary size. Since the XRE die is exactly half the size, a 12.5-13mm focal length should give me the 10deg viewing angle I desire.

I've tried using the SAME lens in front of an XPG and an XRE and I found that the image size projected at 75cm is virtually the same.

Both LEDs come with lenses mounted directly on the emitter, so Die Size is academic - unless you're going to remove the lens.

 

[MikeAusC]

What Beamwidth do you need ?

Work on the optics. If I would do dental work I do not want to get closer to 30cm and no mouth is 14cm wide.

I'm sorry my number was off. The beam is ~2 degrees. That 30cm was supposed to be 75cm

When you talked about wanting a 2 degree beamwidth, I pointed out that you can get a 5 degree beamwidth using a $1 lens within the size limits of your existing housing - 5 degrees is 6.5cm at 75cm. 2 degrees is 2.6cm at 75cm and if you really want that within your existing case size, you will need to use 2 lenses.

On the XPG that I have, it seems a 15mm focal length is perfect, and a 10mm focal length is about 4X the necessary size. Since the XRE die is exactly half the size, a 12.5-13mm focal length should give me the 10deg viewing angle I desire.

10 degrees is 14cm at 75cm - is this the beam size you actually want ?

 

[HarryN]

BTW - I don't think your lens designer is that bad - what you are trying to do is very difficult. That being said, if you are not using a high CRI led in your application, it might still fail, as the standard LEDs are really poor for medical use. They typically just don't provide sufficient red delination.

 

[eatkabab]

Re: What Beamwidth do you need ?

10 degrees is 14cm at 75cm - is this the beam size you actually want ?

Yes you are correct. I intended to type "~12" degrees but didn't realize the "1" didn't come out. The ideal viewing angle is 13.5degrees (after slightly diffusing the light by setting the focal length to a little less than the lens focal length).

In testing, I too just realized that I cannot use the diode size for my measurements since both the XRE and XPG have lenses over the diode. You said that both the XRE and XPG ultimately produce the same size spot if all extra-LED lens/distance variables are constant. I have yet to receive my XRE samples, so do you mind me asking how close in size they were?

This information would be very helpful. Thank you very much for catching that.

 

[MikeAusC]

Re: What Beamwidth do you need ?

how close in size they were? Was the XRE only about 1cm smaller from that distance?

I've just done another test where I tried to make the focussed image as small as possible - the results at 75 cm using a DX4584 22mm dia lens are -

4.5cm - XRE Q4 (EDIT - older one with the larger die)
5.0cm - XPG R4
6.5cm - SSC-P7 (but big cross through it)
10.0cm - SST50
11.5cm - SST90

Hopefully this helps - let me know if more tests are needed.

 

[Walterk]

Here is a thread about calculating on Led's combined with Aspheric lenses.

Here is a thread about the apparant die-size, it might explain someting about the size of the die of the diode, and the dome on top of it.
It also has some information about TIR on the end.

For how to calculate the angle of the spotsize:
It's best to try in real life as you want a specific beampattern.
Instead of calculating I find it easier to use drafting software.

Two notes:
1 - The sketch is using the die, but that is wrong, you should use the 'apparant-die-size' as it is perceived by your eye, projected on the dome.
2 - The optical center of the lens is not at the first plane, but somewhere in the middle of the glass mass, towards the curved side.

So the sketch mainly shows how you can derive an indication for the beamangle.

Edit: My suggestions FWIW;
Use one lens, thats easier and still you can shape the beam as desired.
The Led does not need to be at the focal length, overfocussing, closer to the lens still can give a sharp cut-off.
Dont use a lens with very short focal length, it gives a wider beam and usually more distortion.
Longer focal length gives more narrow beam.

Edit2: Corrected link to thread about 'apparent die-size'.

 

[eatkabab]

In order to choose the correct lens with the 9.5deg sharp viewing angle I need, it appears I must know the 'apparent size' of the XR-E diode. I've yet to receive my XR-E's but I did the following test to measure the apparent size of an XPG.

so using a 33mm focal length lens, I measured a sharp focus angle of 3.29deg.
Plugging that number into the following formula, I derived for "d" the diode size: (which is I'm assuming the apparent size of the diode)

View angle = 2 Arctan(d/2f) - http://en.wikipedia.org/wiki/Angle_of_view
d = 1.898mm

Using this new d, I derived that an f=12mm lens will give me a 9.04deg viewing angle. Is this correct?


With this information and MikeAusC's note that the XRE and XPG LED's have almost the same apparent size, can I assume that an f=12mm lens will give me the same 9.04deg angle? (But I would assume that the XRE's apparent size is slightly smaller and go with an f=11.8mm)

Is that also correct?

 

[MikeAusC]

Just to complicate things, the original XREs (EDIT-corrected from XPE) use 1.0mm die, whereas newer ones use a 0.9mm die.

So if you were designing for production, it would neeed to be based on the 0.9mm die.

I'm not sure if there's an easy way to determine if mine or your XRE has a 1.0 or 0.9 die.

 

[eatkabab]

Just to complicate things, the original XPEs use 1.0mm die, whereas newer ones use a 0.9mm die.

So if you were designing for production, it would neeed to be based on the 0.9mm die.

I'm not sure if there's an easy way to determine if mine or your XRE has a 1.0 or 0.9 die.

Well either way, if you can tell me with high likelihood that the apparent sizes of the XPG and XRE are the same, it would prove very very useful to me. the .1mm can make a difference, but I'll consider that to be why I choose a 11.8mm focal length rather than 12mm

 

[MikeAusC]

if you can tell me with high likelihood that the apparent sizes of the XPG and XRE are the same, it would prove very very useful to me.

Don't the test results in my Msg 72 above give you that ?

 

[eatkabab]

Don't the test results in my Msg 72 above give you that ?

oooo sorry, must have missed that one. Thanks

 

[saabluster]

Just to complicate things, the original XPEs use 1.0mm die, whereas newer ones use a 0.9mm die.

So if you were designing for production, it would neeed to be based on the 0.9mm die.

I'm not sure if there's an easy way to determine if mine or your XRE has a 1.0 or 0.9 die.

I am assuming you meant to say XR-E and not XP-E. There is no evidence as yet that the XP-E uses the ez900 die. The XR-E does however use both. It is very easy to tell the difference as the ez900 has a copper colored band around the die.

 

[MikeAusC]

I am assuming you meant to say XR-E and not XP-E.

aarrrgghhh - thanks, now corrected to XR-E.

The XR-E does however use both. It is very easy to tell the difference as the ez900 has a copper colored band around the die.

Thanks - that makes it clear that my XR-E Q4 5C from Cutter is the 1.0mm die.