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

[Jim Moss]

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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