[Laser] last message was 8/12/2016?

Chuck Hast wchast at gmail.com
Mon May 14 18:07:58 EDT 2018 

Jim
Oops, yes at 1 um the line would not exist, I was following another
calculation
on the spacing and somehow I did not see where the line width was, the
forumla
gave me 1 um, also gives 3.33 um for the 300 line grate, I had better go
back
and check that.

Thank you,


On Mon, May 14, 2018 at 11:21 AM, Jim Moss <n9jim-6 at pacbell.net> wrote:

> Chuck,
> d is the slit width, this is not the same as lines/mm. It is the space
> between the lines.  The line as are m
> Not zero width.
> So d will be < 1um.
> Since the other parameters are known... d must be 0.848 um
>
> Jim
>
> Sent from my iPad
>
> > On May 13, 2018, at 4:39 PM, Chuck Hast <wchast at gmail.com> wrote:
> >
> > Jim,
> > here are my parameters
> > Laser is a DPSS 532nm (using it as a reference as this DPSS is always
> 532nm)
> >
> > I am using this document as my formula source. I have gone at it using
> trig
> > too and it still comes out wrong.
> >
> > http://laserclassroom.com/products/measure-wavelength-laser-light/
> >
> > L= Distance grating to the screen with the meter stick on it  =  1000mm
> > d = line spacing on grating @ 1000/mm = 1/micron
> > N = Maxima N0 = Maxima #0, N1 = Maxima #1
> > X = Distance N0 to N1 = 627mm
> > λ = 532nm
> >
> > The formula I am using is as follows:
> > λ= (X)(d)/L  λ= (627)(0.001)/1000  λ=0.000627 mm or 627 nm which is NOT
> > 532 nm. Either my data is bad OR the line count is bad. I have 10 of
> these
> > grating slides (it was cheaper to buy the pack than one) and all of them
> > give
> > the same error.  Just for grins I tried 3 different DPSS lasers and of
> > course
> > all of them gave the same number.
> >
> >
> >> On Sun, May 13, 2018 at 10:34 AM, Jim Moss <n9jim-6 at pacbell.net> wrote:
> >>
> >> Chuck,
> >>
> >> I remember using the cd as grating experiments.
> >>
> >> Sin(x) = wavelength / gratings
> >> X is diffraction angle
> >>
> >> Increasing the grating from 300 to 1000 decreases sin(x) by 3.3x.
> >> X also decreases.
> >>
> >> For the measurement device you read the diffraction offset and distance
> to
> >> the target
> >>
> >> Accuracy depends on a few variables.
> >> Increasing the grating density will decrease the angle.
> >> If you kept the same target distance, this increases the sensitivity of
> >> measuring the offset.
> >>
> >> I’m not sure what you did to decrease the spot size in your instrument,
> >> but that also can add error.
> >>
> >> See this for a short description.
> >> http://www.nnin.org/sites/default/files/files/Karen_rama_TG_part2_0.pdf
> >>
> >> Jim
> >>
> >>
> >>
> >>
> >> Sent from my iPad
> >>
> >>> On May 12, 2018, at 4:47 PM, Chuck Hast <wchast at gmail.com> wrote:
> >>>
> >>> Nuu, no paper, just a question. I am building a spectrograph to measure
> >> the
> >>> wavelength of lasers I am incorporating into some tools.
> >>>
> >>> Some years back I built one to determine the wavelength of lasers I was
> >>> using
> >>> in glass container inspectors. The thing was spot on, I checked the
> >> device
> >>> using a DPSS laser at 532nm, and a HeNe at 632.8nm. In both cases it
> was
> >>> well within 5nm of what it should have been.
> >>>
> >>> I have built one just recently, but I am not getting anywhere near the
> >>> precision
> >>> I was getting with the one back then. I have tested it with one of the
> >> DPSS
> >>> lasers I used on the original one. I do not have a HeNe here at this
> >> moment
> >>> so not sure where the red end is.
> >>>
> >>> The  original used a grate at 300 L/mm, figuring on greater accuracy I
> >>> bought
> >>> the 1000 L/mm grate.
> >>>
> >>> The series of test I have done have given me about 548nm for a 532nm
> DPSS
> >>> laser, that is way off. The only real difference between the original
> >>> instrument
> >>> and this one is the grating is 1000 L/mm, the original was 300 L/mm.
> The
> >>> only
> >>> thing that I can suspect is the 1000 L/mm is NOT 1000 L/mm but
> something
> >>> more. I guess I will have to reverse the calculations and see if I can
> >>> determine
> >>> the real number of lines/mm.
> >>>
> >>> I may also buy a 300 L/mm grate, then I will have it all the same as
> the
> >>> original.
> >>>
> >>>
> >>> Wonder if anyone else has run into this sort of thing.
> >>>
> >>>
> >>>
> >>> On Sat, May 12, 2018 at 11:01 AM, John McNulty <john at generalrobots.com
> >
> >>> wrote:
> >>>
> >>>> Greetings All,
> >>>>
> >>>> Perhaps there’s a learned paper title forthcoming?
> >>>>
> >>>> "Loop-back Latency in Laser Links" ;-)
> >>>>
> >>>> Best Wishes to All,
> >>>>
> >>>> J McN
> >>>>
> >>>>> On 12 May 2018, at 15:48, Glenn Thomas <glennt at gbis.com> wrote:
> >>>>>
> >>>>> FWIW, the last message I had on this group was August 12, 2016...
> >>>>>
> >>>>>> On 5/12/2018 7:33 AM, Zack Widup wrote:
> >>>>>> I'm still here. Haven't seen any activity on this group in ages. Go
> >>>> ahead
> >>>>>> with your question!
> >>>>>>
> >>>>>> 73, Zack W9SZ
> >>>>>>
> >>>>>>
> >>>>>
> >>>>> --
> >>>>> "i" before "e" except after "c", or when sounded as "a" as in
> neighbor
> >>>> and weigh.
> >>>>>
> >>>>> This rule is “counterfeit”. General spelling rules “forfeit”
> >> generality.
> >>>>> They are “foreign”, being not “either” or “neither”, possibly the
> >> result
> >>>> of some
> >>>>> “leisure” activity of a “sovereign heir” who, lacking “height”, is
> >>>> studying,
> >>>>> without “conscience, inefficient glacier science”. It’s not as
> >>>> nutritious
> >>>>> as "protein". It's just plain old "weird"
> >>>>>
> >>>>> Is this example “sufficient”?
> >>>>>
> >>>>>
> >>>>> ______________________________________________________________
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> >>>
> >>> --
> >>>
> >>> Chuck Hast  -- KP4DJT --
> >>> I can do all things through Christ which strengtheneth me.
> >>> Ph 4:13 KJV
> >>> Todo lo puedo en Cristo que me fortalece.
> >>> Fil 4:13 RVR1960
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> >
> >
> >
> > --
> >
> > Chuck Hast  -- KP4DJT --
> > I can do all things through Christ which strengtheneth me.
> > Ph 4:13 KJV
> > Todo lo puedo en Cristo que me fortalece.
> > Fil 4:13 RVR1960
> > ______________________________________________________________
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-- 

Chuck Hast  -- KP4DJT --
I can do all things through Christ which strengtheneth me.
Ph 4:13 KJV
Todo lo puedo en Cristo que me fortalece.
Fil 4:13 RVR1960

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