ARC AAA-P (DS) beam ring (pic included)

I recently got a new ARC AAA-P DS. I noticed that it has a ring of light surrounding the beam itself.

There is the central hot spot and then the spill area which is pretty well defined. Then out around the spill area is darkness. A bit further out is a ring of light. It is actually pretty annoying in use. I have a couple older versions of the AAA and they seem to have the outside ring but it is nowhere near as noticeable.

Here is a beamshot to try to illustrate this.



The point of light on the left is the light itself. Then, moving right, you can see the ring. Finally you see the beam itself.

Has anyone else seen this? Is this normal?

Mine looks exactly the same. However, my older CS AAA-P's all have rings like that too, and they look proportionally as bright as the DS's ring :shrug:

Mine does the same thing. I never noticed it till I laid the light down on a table while lit up. Does not bother me.

Billl

Never noticed until this thread and I checked.

Super cool......like having an extra light to increase your peripheral vision.

I never noticed this "sub-beam" until I used my AAA-P DS when I went for a walk in severe fog. It actually looks really cool when it's manifested in a 3-dimensional form. I would imagine that it's more a function of the LED optic design than the Arc itself, though. Does anybody know?

Tip it slowly and you can see the bright spot is from the actual tip of the LED.
From almost sideways, it's very bright. Like the various reflections you can get in a raindrop.

If the reflector were significantly deeper and wider, the light coming off at that angle could be caught and reflected forward -- but the light source has to be way down inside the reflector for that, and the reflector much deeper.

I was trying to figure out where it was coming from and couldn't. I think Hank has nailed it.

I compared an older "Limited Edition" unit I have to the new unit. I noticed that the distance from the top of the LED to the end of the bezel on the old unit was nearly twice the distance of the new unit.

Is the DS LED longer than the older LEDs? Or perhaps there is a design change that causes it to be less recessed on the newer unit.

Both my CS have that ring, although it is not uniform, leading me to believe that they are somewhat reflections from the outer part of the reflector, wich has some minor (and very natural) damage from contacting objects in the pocket. Just a possibility, since the oldest Arc has the more rippled "secondary beam".

crocodilo said:

Both my CS have that ring, although it is not uniform, leading me to believe that they are somewhat reflections from the outer part of the reflector, wich has some minor (and very natural) damage from contacting objects in the pocket. Just a possibility, since the oldest Arc has the more rippled "secondary beam".

Click to expand...

That could be part of it. However, if you look at an exposed LED at an oblique angle while slowly turning it you can see the die cup edges and the anode/cathode supporting posts.

You can also make out the difference betwen the two so it could help anyone so inclined to do a ray trace on the epoxy dome.

In fact, with a bare LED, you can see that light will also get reflected backwards (>90deg from horizontal) from the inside of the top of the dome.

chimo said:

That could be part of it. However, if you look at an exposed LED at an oblique angle while slowly turning it you can see the die cup edges and the anode/cathode supporting posts.

You can also make out the difference betwen the two so it could help anyone so inclined to do a ray trace on the epoxy dome.

In fact, with a bare LED, you can see that light will also get reflected backwards (>90deg from horizontal) from the inside of the top of the dome.

Click to expand...

The ring seems to come not from the reflector but from the dome. seems like an inside reflection. I wonder if it is more visible in the GS.

I got curious an decided to do some manual raytracing.

I used a homemade Bluray laser because I know that the beam can be seen in the dome of the LED. The index o frefraction will be a little different for the bluray than white LED but it does well to demonstrate the effect.

Below are some pics and I have a YouTube video as well. Link will come later. I used a Nichia CS and a Larger 10mm LED because it is easier to see.

Here are some raytrace pics using a Bluray Laser. Unfortunately, you cannot see the source, but it is almost horizontal to the LED. Note that you can see a reflection of the phosphor cup at the top of the LED. (1st pic is a Nichia CS, others is a 10mm LED)






Look at the number of internal reflections on this one! This one also demonstrates the reason for the dead spot between the outer ring and the main beam.

I realized that you could not see the laser angle of entry so I have added it (roughly) as well as some notes.

Wow. And I thought I was doing good to post a beamshot. You guys sure know how to make a guy feel inadaquate.

I am not sure I completely understand though. Are you saying that the first two pictures illustrate the source of the beam ring?

I think I understand that the third picture illustrates the angle that represents the outside edge of the spill area of the regular beam. The fourth picture shows the reason for the dark area between the spill area and the ring.

If I am interpreting this correctly, then I am still having problems understanding the source of the light in the ring. Are you saying that it is the reflection off the cathode post (and anode post) that is the source of this light? If so, why is it uniform around the beam? Shouldn't we see two bright areas corresponding to the locations of the posts?

Utik said:

Wow. And I thought I was doing good to post a beamshot. You guys sure know how to make a guy feel inadaquate.

I am not sure I completely understand though. Are you saying that the first two pictures illustrate the source of the beam ring?

I think I understand that the third picture illustrates the angle that represents the outside edge of the spill area of the regular beam. The fourth picture shows the reason for the dark area between the spill area and the ring.

If I am interpreting this correctly, then I am still having problems understanding the source of the light in the ring. Are you saying that it is the reflection off the cathode post (and anode post) that is the source of this light? If so, why is it uniform around the beam? Shouldn't we see two bright areas corresponding to the locations of the posts?

Click to expand...

I guess I was not very clear in my explaination. What I intended by th first three pics was to illustrate the "arcs of fire" (no pun intended) of the ring. The light source is the phosphor - the "posts" comments were to show the outermost edge of the phosphor. The last pic was to show the cause of the dark area between the rings.

Paul