"635nm" vs 650nm

I have bought a 30mW 635nm laser a while ago. Today I finally got my diffraction gratings and did a quick lil test.
Testing conditions:
- Lasers used: 30mW 635nm, 50mW 650nm
- Diffraction Grating: Diffraction Grating sheets by foot 1,000 lines per mm
- Distance to the wall: ~45feet
- Point reflected to the door
- Camera used: Kodak EasyShare C613


What do you think about it?

Edit: Tell me if you think this laser is a 635nm or not. The brighter dot is the 650nm one!

Have no clue as to what you did... maybe a little more detailed explanation
would help...
What I see 2 red dots on a wall...:thinking:

Jerry

lasersbee said:

Have no clue as to what you did... maybe a little more detailed explanation
would help...
What I see 2 red dots on a wall...:thinking:

Jerry

Click to expand...

I think the (implied) question (and poll) is:
Do you think the new (30mW) laser really is 635nm?

Personally, I have had quite a bit of experience distinguishing between 635, 650, and 660 nm reds. So, I can clearly see that the lower dot is 635nm (light-red) and the upper dot is sightly darker (650nm? or 655nm). :gun:

What do I think about it?

lasersbee said:

Have no clue as to what you did... maybe a little more detailed explanation
would help...
What I see 2 red dots on a wall...:thinking:

Jerry

Click to expand...

I hold the lasers one above the other, the 635nm is the one with the gold cap. The reflected points are on the left side on the door. I also did the test with green and br, the space was really huge. I can do some comparison fotos later on, maybe I find a better place to do the test

Can you take a pic of the beams in a dark environment, perhaps with some smoke/fog?

as I am a huge 632 HeNe fan, my opinion is biased.

Sure, the deep dark red is attractive, love that ruby color, but I like lower power lasers that are easier to see.

I think I see what is going on.
The beams of 2 red lasers are passed through a diffraction grating and projected on the wall.
The supposed ~650nm on top and the supposed 635nm on bottom.

I'm not sure why the diffraction grating was needed, but I can clearly see a difference in hues between the two lasers. The 635 is definitely more orange.

If you were trying to use the diffraction grating as a sort of crude spectrometer, the difference in wavelengths +/- 20nm will be too small to accurately measure this way.

@DJNY....

Now I know what you're trying to do...
You want to know if the 2 lasers are actually different wavelengths..

The test setup is all wrong... it will show you nothing...
At 45 feet... you are way too far from the wall...IMO

1) you need to shine a laser through the diffraction grating onto a wall
at a distance that will allow you to see at lest 2 horizontal dots.
(flip your diffraction grating 90 degrees if the dots are vertical)

2) the longer wavelength will have a greater distance between the dots

3) if the difference is very small... get further away from the wall while
still being able to see the 2 horizontal dots per laser... the dots and
differences will spread out...

I explained this to you in the PMs we exchanged...


Jerry

The cam doesn´t show the 635nm correct, in reality both of them look the same color, the 50mW 650nm is much brighter. I can fill the bathroom with steam and look for a greater distance to do the diffraction test. But it should be a gap between +/-20nm. Yeah I know that you can´t compare it with the 650vs532nm spacing but I think I can expect a lil gap!
I posted some other pics in this thread: http://laserpointerforums.com/f50/looking-635nm-red-46206-2.html

I think only the LPM will show me what is wrong with one of these or both lasers.

I´ve done a short vid of my 4 reds
notice: the second dot on the wall is the dilda

Edit: Ok Jerry, I really misunderstood something ^^ I´ll try to do the test again

Edit2: I cant see any difference, I also went some steps backward (not in vid, pics) and did the test again, no difference.
When the LPM arrives I´ll do a power test and that´s it

Honestly, I can tell the wavelength difference pretty clearly even between my AtlasNova 5mW and my Dilda 200mW. Yes, the dilda is brighter but its still a very different shade of red than the AtlasNova, no matter what.

If you can't tell the difference, it's probably not 635. The only 635 TEM00-capable diodes that I know of in that power range are from JDSU, and i think they'd be a bit more expensive than the $40-$60 this thing cost.

I might be wrong though, and if I am, i'll probably order one.

aryntha said:

Honestly, I can tell the wavelength difference pretty clearly even between my AtlasNova 5mW and my Dilda 200mW. Yes, the dilda is brighter but its still a very different shade of red than the AtlasNova, no matter what.

If you can't tell the difference, it's probably not 635. The only 635 TEM00-capable diodes that I know of in that power range are from JDSU, and i think they'd be a bit more expensive than the $40-$60 this thing cost.

I might be wrong though, and if I am, i'll probably order one.

Click to expand...

I wanted to order the Atlasnova, but they don´t accept PAYPAL. I´m going to ask Robin if I can send my 635nm back. But would be nice to test it vs the Atlasnova.

The camera won't show enough of a difference. The dimmer dot DOES look more orange on the video but i have a feeling that may just be because it's closer in proximity to the green, and the bayer filter pattern and video pixel averaging (why 5mp cameras don't shoot 5mp video) of the camera's CCD is causing it to inherit some adjacent green. (because the dots out to the side do not look more orange.) But in short, the camera doesn't have the sensitivity curve our eyes do.

Overall, its generally very easy to tell 635 from 650 when side by side. Maybe its 645, not 635. (for example my z-bolt "635" is actually around 640, my AtlasNova is pretty much dead on 635.)

Atlasnova accepts paypal if you get it through their eBay store. (abeland1)

ATLASNOVA RED 635nm Laser Pointer AAA SILVER - eBay (item 390160669898 end time Mar-23-10 10:22:17 PDT)

Really I have nothing but good things to say about Atlasnova... The lasers aren't "high power", but theyre definitely built well. I have an Atlasnova 650 and 635, and they really are night and day.

Again 30mW of 635 should be visibly brighter and different than 50mW of 650. But the real deal here is - on the diffraction grating tests there, they almost line up exactly with eachother. That's not a good sign.

I'd say the prognosis isn't good for this being a 635. I wrote to this company too, and they assured me it was 635 not 650, but I didn't order because I was too skeptical.

Do you know anyone with a HeNe to compare it against?

It helps if you try to take brightness/saturation out of the equation. Try waving them both in the same hand to make a line on the wall. It is far easier to tell if the light sources are diffused in some way.

With a 635nm shining next to a 650nm I have no trouble telling them apart. If you have trouble seeing red, it may be a challenge. Have someone else look at them side-by-side. The 635nm will look more orange.

I have an old 5mW AtlasNova 635nm (focusable) that I have stripped the paint off of (so it is "brass") you can have for $20

Peace,
dave

daguin said:

With a 635nm shining next to a 650nm I have no trouble telling them apart. If you have trouble seeing red, it may be a challenge. Have someone else look at them side-by-side. The 635nm will look more orange.

I have an old 5mW AtlasNova 635nm (focusable) that I have stripped the paint off of (so it is "brass") you can have for $20

Peace,
dave

Click to expand...

Thanks! I take your old Atlas Dave. I´m really interested if I can see a big difference between them! Send me your PP pls

Btw: Since today I have to press the button of my 650nm extremly hard to activate it! What can I do?
Edit: I fixed the problem a lil bit, but it still has a loose contact
Edit2: problem totally fixed lol

Got Dave´s Atlasnova today.
Now I know how a 635nm dot should look like.