[Laser] last message was 8/12/2016?
Jim Moss
n9jim-6 at pacbell.net
Mon May 14 12:21:05 EDT 2018
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
> ______________________________________________________________
> Laser mailing list
> Home: http://mailman.qth.net/mailman/listinfo/laser
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Laser at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
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