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New! Sharp Diodes 1W 520nm & 5W 455nm & +2W 638nm

CDBEAM777

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Well....Thanx Steve001......I have no formal training in Optics but am always very eager to learn and learn !! SO....Far Field is when the beam geometry is 1.4 times the initial LD diameter. OK...good to learn the proper definition ! To me....that is not really to far.... SO...Most of out LD's have an initial OD of say...2.5MM....SO....the Far Field would be when X or Y axis exceeds 5.0mm ?? That geometry happens relatively quickly...Or, have I over simplified this ??

I need to study this more. It is not surprising that there are well defined terms for almost every aspect of Optics. I do not now or have ever presented myself as an expert in Optics. Just a Hack with much to learn....and a passion for tinkering with this stuff !!

That said....I suppose we need to explore this area of beam viewing at various distances. The NDG7475 + G8...when the beam geometry is examined at say 13M appears to be fairly compact, almost round. BUT....when the beam geometry is noted at ...say 100M....well.....if one can see detail at that distance...the shape is more recognizable as a rectangle. When the beam is viewed at a skyward angle ( Never do this )….Parallax view takes command...and the beam again appears thin and compact. SO.....I guess....beam geometry all depends on the distance to where the beam terminates and our human perception !!

CDBeam
 



Alaskan

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For myself, although a relationship exists, I don't care what the distance the beam diameter doubles (four times more spot area), what I care about is what happens to the beam hundreds of feet out which will be far beyond that. No practical reason for this, just want to know and correct as best I can so the beam stays as tight with as close a size ratio to one another as I can reasonably achieve for both the fast and slow axis sides of the beam. I'm going to refer to that distance as the far-far field to avoid any confusion over the stricter definitions.
 

CDBEAM777

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OK....On to what this Hack is now doing with the Blue FAC. Achieved a mRad of 0.75. Beam geometry at 13M / 12mm x 10mm. Very minor vertical and horizontal spill.

Set-up @ NUBM08 FAC+ G8 + 6X Cylindrical lens pair. PCV/PCX placement is...er....demanding. On to tame the Red....IF possible !!

CDBeam
 

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CDBEAM777

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" Far Far field "....good way to describe it....at least we have a common language in our HH world. I doubt that the Optical Engineers would agree.
They are so demanding !! HAHA...Later, CDBeam
 

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Alaskan

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Well, in RF engineering we refer to the far field and it has nothing to do with the diameter of the beam. To each discipline their own definitions, of course.

Quote Wikipedia:" The far field is the region in which the field acts as "normal" electromagnetic radiation. ... The boundary between the two regions is only vaguely defined, and it depends on the dominant wavelength (λ) emitted by the source and the size of the radiating element".

Yes, I too can google! My magic hat has an interface directly to it.
 

Alaskan

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Eagerly awaiting a post about the FAC red laser diode, hoping the spot size at that distance is close to the measurement you had for blue.

Edit: NOT likely, but hope springs eternal!
 
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steve001

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I am not questioning the definition, just think he didn’t mean it that way nor have I in the past, in the far distance would be a better way of putting it less someone challenges a choice of words. Yes, I understood you were googling it.
Any distance passed the Rayleigh Length which varies greatly. He's right. I think he mentioned 150m which would certainly be in the far field in this case.
 

steve001

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I used a 25mm bi convex lens and was able to focus to a tight spot/line @ 2 meters from about 75mm out but the beam ran from about 15-17mm wide to the point, not the beautiful beam we like for lightshows ect...also the beam strikes the lens square but focuses down unevenly becoming ( ribbon like ) and ending as a small line/spot
Was your objective to focus or to achieve infinite conjugation (infinite focus)?
 

steve001

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MMMmmmm ???? Define Far Field...is that 15M....or 150M....or other ??? My FF is 14M... IMNSHO...after that...to some degree...Parallax View presides. CDB
In a reply yesterday to Alaskan and today the far field depends on where the beam starts to expand linearly. Before that the beam is in the Rayleigh Length (RL). Did you measure the RL?
 

CDBEAM777

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MMM …. Infinite Conjugation THAT is what we want....as close to it as possible. I have not measured the Rayleigh Length. Will study this. Each lesson in Optics is a fight to understand when one is missing formal training....Possible...but hard earned....driven by passion and unending curiosity.

Also...a few more pics of the NUBM08 FAC + G8 + 6X C Lens pair ...Set up and the Beam termination @ 13M.

A Cold Beer awaits the First Rocket Scientist whom identifies what movie the last pick was borrowed from !!!!

CDBeam
 

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steve001

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MMM …. Infinite Conjugation THAT is what we want....as close to it as possible. I have not measured the Rayleigh Length. Will study this. Each lesson in Optics is a fight to understand when one is missing formal training....Possible...but hard earned....driven by passion and unending curiosity.

Also...a few more pics of the NUBM08 FAC + G8 + 6X C Lens pair ...Set up and the Beam termination @ 13M.

A Cold Beer awaits the First Rocket Scientist whom identifies what movie the last pick was borrowed from !!!!

CDBeam
Without knowing where the RL ends you'd be unable to know where the far field begins. In other words far field begins where the beam expands linearly.

I sure appreciate the input from you guys! Makes LPF a much better resource. Steve, you, you, tripple poster you.
I forget how to easily multi-quote.

[/QUOTE]
Focused to as small of a spot as I could get at 2 meters.
Try this to see what happens. Place that lens a distance equal to the focal length from the diode.
 
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RedCowboy

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Well....Thanx Steve001......I have no formal training in Optics but am always very eager to learn and learn !! SO....Far Field is when the beam geometry is 1.4 times the initial LD diameter. OK...good to learn the proper definition ! To me....that is not really to far.... SO...Most of out LD's have an initial OD of say...2.5MM....SO....the Far Field would be when X or Y axis exceeds 5.0mm ?? That geometry happens relatively quickly...Or, have I over simplified this ??

I need to study this more. It is not surprising that there are well defined terms for almost every aspect of Optics. I do not now or have ever presented myself as an expert in Optics. Just a Hack with much to learn....and a passion for tinkering with this stuff !!

That said....I suppose we need to explore this area of beam viewing at various distances. The NDG7475 + G8...when the beam geometry is examined at say 13M appears to be fairly compact, almost round. BUT....when the beam geometry is noted at ...say 100M....well.....if one can see detail at that distance...the shape is more recognizable as a rectangle. When the beam is viewed at a skyward angle ( Never do this )….Parallax view takes command...and the beam again appears thin and compact. SO.....I guess....beam geometry all depends on the distance to where the beam terminates and our human perception !!

CDBeam
Good work BEAM :)
 

CDBEAM777

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NEWS...Red FAC TAMED.....Red FAC + G8 + 6X Set Cylindrical lenses =
@ 13 M =====> 7mm x 7mm Beam Geometry !
This equates to a 0.4 mRad.....0.4mRad.....Really.....so, some ghost aberration....above and below the spot geometry....nothing that cannot be masked out.
See pics. Must measure the PO of these diodes....seems awful bright ????

SO....What's next....also need to experiment what effect the C-Lenses have on the Green FAC..... Whada Wild Ride !!!

CDBeam
 

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