Hi guys,
For various flashlight/dive light projects I have been looking for good fresnel lenses to focuss the light of LEDs.
I know many of you are familiar with aspheric lenses. Fresnel lenses can provide the same functionallity using a very thin lens, typically only 2mm thick.
The advantage is a very light weight plastic lens. Due to the nature of the fresnel lens, it also doesn’t stick out of flaslights like aspherics do, so you can often place it behind the standard glass lens or replace the glass lens by the fresnel lens.
People that already experimented with fresnel lenses and aspherics, probably noticed that you need lenses that have short focal length relative to their diameter, otherwise known as a low F number.
While searching for good lenses, I often ran into high shipping costs out of China mainland.
Therefore, I ordered more than I needed so I have some to spare, and I’m willing to sell them here. Some forum members here on BLF and on CPF already have some. If they want to post pictures here, that’s fine for me.
I currently have 3 types of lenses for sale:
- 25mm diameter
- 38mm diameter
- 50mm diameter
The 25mm lens is very similar to the ahorton lens, but I think it is more interesting pricewise and if you don’thave a lot of space like in dive lights. I used this lens in several projects where often P60 style dropins can be used. I used them with custom made spacers which keep the lens in place and put it at the right distance from the LED.
The 38mm lens I just bought for testing, but haven’t finished the build yet so don’t have pictures of this yet.
The 50mm lens fits perfect behind the front lens of a Maglite. I just added an o-ring to push it against the lens so it wouldn’t rattle and an o-ring to seal it (since the edge of the reflector is not there anymore).
When specifying the distance to the LED, I prefer to give the distance between the lens and the heatsink, as this makes it easier to make a heatsink.
I place the 25mm lens at about 15,5mm from the heatsink, the 38mm at 18,5-19mm (haven’t measured this exaclty yet) and the 50mm lens at about 28,5-29mm depending on how far away you want to focus it.
The lens should be used with the side with the rings pointing away from the LED, otherwise the lens doesn’t work.
Prices (paypal fee included):
- 25mm lens: 6€/lens
- 38mm lens: 7€/lens
- 50mm lens: 7.5€/lens
I ship them from Belgium in a standard bubble envelope
International shipping: 1.5€, for tracked shipping +5€
For these shipping costs, I can ship multiple lenses.
You can pay via Paypal at [my_username]@gmail.com where you need to replace the [my_username] by my actual username.
current stock (I’ll try to keep this up to date):
- 25mm: out of stock
- 38mm:7
- 50mm: 25pcs
If many people are interested, I can order more and try getting the price a bit down.
Some pictures of these lenses and results:
25mm lens in plastic holder (not included)
result with an XML (image underexposed):
comparison between the 25mm lens with XML and the original led and optic (driver was nog changed)
50mm lens installed in a maglite:
XRE with 50mm lens in a maglite, focussed on the ceiling:
comparison between the 50mm lens and the gaggione LLC49R optic, both with XML, image is underexposed:
50mm lens installed in a greenforce PRO dive light:
If you have any questions, let me know.
Best regards,
Johan
Sales:
username: 25mm-38mm-50mm-status
MosesM: 1-1-1-shipped
Confusius: 1-1-1-shipped
djozz: 0-0-1-shipped
waehrik: 0-0-2-shipped
John Murtagh: 0-0-4/4-shipped
NVF1: 1-1-1: shipped
NV2: 0-3-2: shipped
NV3: 0-2-0: 2 shipped
cat eyes: 2-2-2 shipped
cereal_killer: 0-1-0
onetrickpony: 0-0-2
Dave_: 0-1-0