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05-15-2011, 08:08 PM #1
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rhd
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NEW TOOL: Determine Wavelength Using a Diffraction Grating

Hey all,

This is a follow-up to my Wavelength to RGB / HEX and my Relative Laser Beam Brightness web tools.

A few months ago, Cyparagon pointed me in the direction of his thread on calculating the wavelength of a laser by using a diffraction grating (this thread), and suggested that it would make a good candidate for one of my web-based tools. I agreed! While it took me a few months, I finally got to it this weekend

Using a diffraction grating, and a ruler, you can calculate the wavelength of your laser. This tool helps bypass any math on your end. Math is hard. Have a look
Calculate Wavelength (nm) Using Diffraction Grating

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05-15-2011, 09:00 PM #2
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lasersbee
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

Nicely done....
I'll check this out tomorrow...

Jerry
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05-15-2011, 09:24 PM #3
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laser_freak
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

This is a great tool. Well done. My only suggestion is to be able to calculate the lines per mm of a diffraction grating using a known wavelength. This would be helpful for people who have diffraction gratings with unknown line densities.

Last edited by laser_freak; 05-15-2011 at 09:25 PM.

05-15-2011, 09:34 PM #4
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rhd
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

Quote:
 Originally Posted by laser_freak This is a great tool. Well done. My only suggestion is to be able to calculate the lines per mm of a diffraction grating using a known wavelength. This would be helpful for people who have diffraction gratings with unknown line densities.
Interesting - ok

In order to keep this tool as simple as possible for those who do know their density, I think I'll make that a separate tool.

EDIT: You'd probably only want to do that with a DPSS right ?
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Last edited by rhd; 05-15-2011 at 09:36 PM.

05-15-2011, 09:43 PM #5
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laser_freak
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

Also does this use the small angle approximation using tan(x) ~ x, so that x ~ (m lambda L) / d ?
I would suggest not using it just in case.

Yes, you would only want to calculate the line density using a known wavelength laser, such as a DPSS or gas laser.

Last edited by laser_freak; 05-15-2011 at 09:45 PM.

05-15-2011, 10:04 PM #6
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rhd
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

Quote:
 Originally Posted by laser_freak Also does this use the small angle approximation using tan(x) ~ x, so that x ~ (m lambda L) / d ? I would suggest not using it just in case. Yes, you would only want to calculate the line density using a known wavelength laser, such as a DPSS or gas laser.
It uses:
λ = diffraction-grating * sin(arctan(distance-between-dots/distance-from-screen))
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SAFETY & IMPORTANT READING (threads authored and contributed to by various members of LPF):
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- The Necessity of Safety Goggles (link)

05-15-2011, 10:18 PM #7
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

Cool

05-16-2011, 01:33 AM #8
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

Now . . .

who did I buy those diffraction gratings from:

LarryDFW
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Last edited by LarryDFW; 05-16-2011 at 03:29 AM.

05-16-2011, 01:48 AM #9
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

Quote:
 Originally Posted by rhd Using a diffraction grating, and a ruler, you can calculate the wavelength of your laser. This tool helps bypass any math on your end. Math is hard. Have a look
Here's to no more math!

05-16-2011, 02:22 AM #10
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jakeGT
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

I. HATE. MATH

So, this is cool!
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05-16-2011, 03:01 PM #11
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Cyparagon
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

I use this type of grating. For better accuracy, take the average of the distance to the dot directly to the left and the dot directly to the right.

And yes: small angle approximation is a no-no because many gratings will... not have a small angle.

Quote:
 Originally Posted by rhd You'd probably only want to do that with a DPSS right ?
Yes. Only DPSS or gas lasers have precise known wavelengths for all operating conditions.

Thanks, rhd!
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05-16-2011, 06:59 PM #12
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Re: NEW TOOL: Determine Wavelength Using a Diffraction Grating

I vote for a sticky! Very cool tool!
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