Which optics are best?

[gch412001]

I'm building a headtorch for night orienteering and all night races. My plan is to build a 4 LED unit based on the CREE R2 LEDs since these seem to be the brightest ones available.

But how do I get the best out of these LEDs? What sort of reflector/optic is best? Do the very small optics work as well at throwing out an even light?

So far I've seen the following two possibilities
http://www.dealextreme.com/details.dx/sku.1915
http://www.cutter.com.au/proddetail.php?prod=cut781

The first one is 50mm diameter and the second one is a tiny 35mm diameter. Am I going to get as good performance out of the smaller one? Has anyone used either of these optics or can recommend something else that is good?

Oh and does anyone know how the 4xCree R2 LEDs will compare to the 20W silva headlamps currently used in night orienteering events? I'm not sure how to convert from lumins to watts or if it's even possible to directly convert them.

 

[Gunner12]

Best is a very subjective word.

In order to know what kind/brand/model of optics is best for your application(you might need more then one kind) we'll need to know the beam-pattern you want(narrow? floody? smooth? etc.).

If it is a 20w incan headlamp, then 2 R2s or Q5s(cheaper but slightly lower output, hard to notice) should match the output(depends on the current to the LED).

In order to convert from lumen to watts, you'll have to know the efficiency of the source.

:welcome:

 

[gch412001]

I want a narrow beam of light preferably. The aim of the light is to be able to spot things well in the distance and to have enough light to run comfortably with. (if there is some other type of beam that would be more suitable then please tell me.)

Oh and I plan to run the LEDs at 1000mA

 

[ifor powell]

I have some pictures of my night-O / bike lights here.

Optics wise they are not all the same. I only tried the indevidual ones myself rather than the combined. I went for the square Ledil ones as they seamed to work well and meant I could do custom housings with just simple tools. Indevidula means I can tune the beam for my needs.

Compared to a 20W Silva I would say that 2 Q5s driven to 1000mA gives a better light.

Ifor

 

[TorchBoy]

Have you considered something like http://www.dealextreme.com/details.dx/sku.11921 ? I haven't used it, but the stand-alone orange peel reflectors I have used give a nice beam and more spill than optics, which is nice (and very desirable) for caving.

I guess it would depend on the sort of racing you're doing. If you were cycling at high speed along a road then go for optics, but I presume you're on foot?

 

[PeterC]

I've successfully used a DIY LED headlamp for night orienteering. The design of this used two SSC P4 U-bin LEDs, run at about 500mA, with the square Ledil optics (one +/-5 degree smooth spot and one +/-9 degree diffuser). Brilliant for night orienteering (better than my aging Silva lamp)! I chose the Ledils because they were square (easier for me to work with) and provided a range of fully documented beam patterns to experiment with.
NB. During my initial work on the two LED headlamp, I measured the beam width of a reflector from a Silva 10/20W halogen lamp to be about +/-11 degrees.

My personal preference is for a reasonable amount of spread to light up the area where I'm about to put my feet, making it easier to run safely through the terrain at speed and helps in navigating (e.g. less likely to miss vague path junctions). It also gives sufficient peripheral light for reading the map.

This design does lack a little for distance work, however, and I'm currently working on a 4 LED version (essentially the same as the original, but with a couple of pure spot beam optics added). For me, the spot beam is of secondary importance to the medium beam providing the area light.

In terms of brightness, the two LED headlamp easily outperforms a typical Silva 20W halogen headlamp on the 10W setting, but isn't quite as bright as the 20W setting. Light quality for night orienteering, however, (for me) is much better with the very white LEDs compared to the yellowish halogen and this compensates for some of the loss in absolute light quantity. Based on my experience, I'd agree with Gunner 12 and Ifor that two Cree XR-E R2 bin LEDs (driven at 1A) should be at least as bright as the 20W halogen. A 4 LED design should blow it away!