Bike light beam patterns.

I'm always building or thinking of a new bike light. The problem is a bike light does not need to have a symmetric beam shape, nor is it beneficial to be, like a flashlight. The ideal beam shape is open for debate but something similar to a car's headlight sounds about right. Picture two triangles of light, one with say a 10 degree angle and another with a 45 degree angle. The idea is to have down the trail light for spotting obstacles and up close light for navigating around them.

A sharp upper cutoff also helps; because the glare is reduced for oncoming eyes and upward light is essentially wasted as it does not hit the trail or road surface.

I'm wondering if anyone has any ideas on generating such a beam shape with off the shelf parts. Would it include multiple types of reflectors or some magic reflector that can move its hot spot to the outside of the side spill. Oh did I mention bikers like things small and light.

Also as an aside what color do you think would be best for biking at night. Stick with white or would Cyan be better due to the eye's response curve under low light conditions.

Just a thought on color choices. Your eyes are more sensative to green light than any other color, this can be good or bad. If you are dealing with very low light conditions, green is better, but if you have a bright green light, it is worse for your night vision. Thats why night vision equipment has a green output. I would guess that since you are a CPF'er that you will end up with something that is quite bright, in which case green wouldn't be the best choice. Take a look at this site for some more detailed info. http://www.equipped.com/nitevision.htm

good points
have you seen the Line optics?
like the 6x25 optics? they could form a line, which would be brighter at the closer points, but still extend out.
i think that the 6 degrees might still be to tight.
so (like you said)
a Duel 3W lux light, with something like a 15* opticas on one, and a 4* optics on the other.

Reflectors (on luxes) DO have some of these properties in the ONE package, because only part of the led actually hits the reflector, the rest just passes out at the angle of the reflector "side spill" but MOST reflectors are a useless to bike riding spot in the middle of the road, just as bad as a 5$ incandescent light.

i think a car headlight seems to be about 10-13 degrees, but only trying to read it with a protractor and 2 straws, that is what i got.
and lots of car headlights have certian spread patterns, and blockers to keep light from hitting others, that stuff WASTES light, no reason to waste light , if you can controll it in the first place.

2x 3W luxes would also be just sufficient light, and would give some fair runtime, like you could get (about) 1HR with 3xAA Size or 4 hours with D size battereis.

a nice hunk of aluminum billet with fins, in a 2 lux light with CHANGABLE optics, and a optics SET, with a snap on plastic lens on the front would look nice and have all the features one would want.
have the battery pack be a Bar holding long battery sleeve of about any sort, mix it up /ubbthreads/images/graemlins/smile.gif have it run the length of the bar on the bike that is ALREADY there.

for now i wont mention that a bike already IS a battery tube, and taking the seat off to put batteries in , would not be an inconvience /ubbthreads/images/graemlins/smile.gif

Get some of the optics , and a single rawer lux thing (flashlight you can change optics, or just a rew star) to play with. that wouldnt cost that much, and you could design with the parts IN HAND.

there is no way to please all types of riding, or roads with One light, or one TYPE of light, by having 2 heads, and CHANGABLE optics (or reflectors even) the user can balance out the locations of his spot and his wide for the terrain, pot holes, or road they will travel on.
with a hunk of billet aluminum BOLTED to the bike, and the bike frame as the battery tube, there is no fear of having Just the light itself stolen.

snowman -

A Carclo 10003 L25 6 degree optic has linear ridges on it to direct the beam into a long thin pattern. Maybe V ridges would produce a triangle.

Here is a link to darkzero's thread with lots of beamshots from optics. It is a good study in what can be done. In this pictorial the Carclo 25 X 6 can be seen as well as the NXO5, the rare NXO1 along with one of my favorites, the Carclo 6 degree.

I thought this might be of interest to you.


darkzero's optic comparison thread

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- Jeff

I have been using Luxeons as bike lights for a few years. For general street riding when I get caught after dark, a minimag with a BB500mA current regulator driving a Luxeon bin R2H and Fraen LP optics works OK. I calculate around 55 lumens at 500mA, the run time is over 2 hours and it mounts on my helmet.

It gives off a square beam with very little sidespill and I can ride at 16MPH (26KPH) in pure darkness with no problem. This is street riding and dirt riding is different in that you need more light.

For riding around during the winter months, I added a 2D Mag with a Luxeon R2H driven at 800mA(~75 lumens)to my frame. This gives a bright pencil beam that is less than useful in that it is so narrow. I have since built a 8AA Mag with a Luxeon V bin WX1S (~170 lumen) It works MUCH better as a bike light in that the hotspot is considerably larger (Luxeon V has 4 emitters packed next to each other giving a larger hotspot through Mag optics)

Together, the 55 lumen minimag and 170 lumen "2D" Mag work very well for street riding. I can ride my recumbent at 22MPH (35KPH) with no problems and the helmet mount light points the light were I am looking. The hotspot coming off the 2D frame-mounted light throws a bright spot further down the road and the side spill works well close-up. I am ordering an extended bezel to change the optics in the minimag, a 20mm reflector should work better than the Fraen.

If I was going to have the "ultimate" bike light, it would have 4 Luxeon K2 SWAH emitters in a custom head. Two of the emitters would use the 27mm optics for throw and the other two would have 17mm for the middle range and a flood for close-up. Having the K2 Luxeons running at 750mA each would allow 12 NiMH 2500mAH AA batteries to run 3 hours of even regulated brightness.

Hi snowman,

regarding reflectors and optics - one guy who has put a lot of effort into this kind of things is Olaf Schultz in Germany (not on cpf AFAIK) - check out the links in chapter 2 . All in German, though.
In general, the 6 deg. optics still have too much spill and too much light above the horizontal to be useful as general purpose ('low beam') lights, although you can use the elliptical beam with some additional shading for close-up lighting (see e.g. here or (with the MOBDAR optics) as a high beam).

Personally, I'm using a dual Luxeon III setup with 1/2 of a Lumotech reflector for each Lux for 'low beam' and plan on adding a 3xLux III (with proably SO20XAs) for a high beam.

Regarding the colour: yes, Cyan will give you more visible brightness - if the environment contains enough stuff to reflect the cyan light. I have two cyan Luxeons in our bedroom, and all I can say is that the colour rendition becomes weird. In addition, any coloured lights may get you into trouble with other drivers on the road. Stick to white.

Bye
Markus

I modified a cheap halogen bike light with two LuxIIIs side-by-side and Fraen-LP optics. The stock diffuser helps merge the beams and spread the pattern out a little. There's a lot of wasted spill, but it is useful by being visible to drivers without being intense enough to dazzle them. I found that I had to point it sharply downward to keep from being annoying.

http://www.candlepowerforums.com/ubbthreads/showflat.php?Number=545484

I agree about the need for a sharp cut-off.

I run four oldish 1W Luxeons from a dynamo, two with Fraen 6deg (which come out as 10deg with white Lambertians)and a couple of '30mm' optics which produce a 6 deg (estimated) beam.

Quadlight

This set-up wastes a lot of light above the horizontal and I feel the need to put my hand over it when cycling against other road users on unlit roads.

To get a sharp cut-off, you have to start with collimation that achives a beam with the desired cut-off, then spread it in the directions you want more light from there.

There is no way that I know to add a cut-off to a beam that is already spreading too much without a large lens or a blind some distance from the light source - both scruffy and wasteful of light or weight.

Carclo's 50mm double refracting lens is said to give a 2deg beam which would be a good start if a sharp cut-off was required, perhaps with embossed sub -lenses on the front to spread the light sideways and down.

Maybe we (CPF cyclists) could persuade one of the collimator makers that there is a market for a bike-light optic. - maybe conforming to the German standard, which is pretty sensible with respect to cut-off and beam shape.

I would be tempted to try to make my own if I was better with machine tools and had some more time left after cycling, making bike lights and living a life!

Steve

When you say ride "trails", what do you mean exactly?

1) Asphalt covered maintained bike/rollerblade/pedestrian trails

OR

2) do you mean technical off-road trails that go up and down with sections of water one has to cross

OR

3) do you mean primarily flat off-road woodchipped firetrails/gravel trails?


If it's the middle of the three choices, then I wouldn't suggest a sharp cutoff nor would I suggest a wide beam. Myself, I had played around with a few different incandescent setups at high power ranging from dual 20W setups (40W total) to a 55W low+85W high setup (140W total) and I ride in the #2 scenario, off road.

Any thing with a cutoff like an automotive auxilliary fog beam pattern was totally useless in anything other than linear biking and in many many cases, I would see LESS with the lights off than without them on.

On a quickly cresting hill, a beam with a sharp cutoff will only light the ground immediately in front of you while you struggle to see the actual path in the light's periphery. This causes one to scrub lots of speed and potentially hit something like an overhanging branch or off a cliff or ... well, you get the idea.

Anyway, that's my 2 cents but it may not even be applicable to the author's needs.