Spectroscopes

[Atomicrox]

Due to lack of funds to buy a proper monochromator or spectrometer, I'm inclined to buy one of the spectroscopes on feebay. Thought I should ask for help since I don't have any expertise on the subject.

Going to use it for lasers, LEDs and other light sources, not for geology.

Here are the options, ordered by price:
Diffraction Spectroscope Gemstone Gem Gemological 7206 | eBay
High Quality All Metal Prism Direct Vision Gem Spectroscope in Case | eBay
"Prismatic Spectroscope" Gem Tools Good Quality New | eBay
Focusable DVS 5 Prism Spectroscope Fr Gems w Wavelength Scale Slit Adjustment | eBay

Are these any good or am I better of with a diffraction grating in a black box?
Is the larger price of the prismatic ones justified?
What kind of WL resolution can I expect with the most expensive one?

 

[Sigurthr]

Prismatic spectroscopes spread light nonlinearly by wavelength, keep that in mind. Grating based scopes will have a relatively accurate linear scale.

Personally, I just use an off the shelf equivalent of a grating in a box with a slit. It has an almost accurate scale built in, accuracy comes to about +-5nm (which is a delta of 10nm). Ah, here's the one I have New Quantitative Spectroscope Light Measuring Colors Boreal Laboratories | eBay. You have to fine tune or calibrate it by widening, thinning, or effectively moving (by covering and making a new) the slit in the end.

 

[Rifter]

Prismatic spectroscopes spread light nonlinearly by wavelength, keep that in mind. Grating based scopes will have a relatively accurate linear scale.

Personally, I just use an off the shelf equivalent of a grating in a box with a slit. It has an almost accurate scale built in, accuracy comes to about +-5nm (which is a delta of 10nm). Ah, here's the one I have New Quantitative Spectroscope Light Measuring Colors Boreal Laboratories | eBay. You have to fine tune or calibrate it by widening, thinning, or effectively moving (by covering and making a new) the slit in the end.

Those things really work? i wrote them off as gimmicks lol

 

[Sigurthr]

Haha, yup. That's the nice thing about simple physics, you don't need grandiose designs to get working results. If you calibrate it to Hg lines you'll get within 10nm of the scale's marking if you fine tune the slit position just right, and the precision is about 5nm with an ideal slit width, which isn't bad for $10 of plastic. You won't see the two individual ~588 lines of sodium, but you'll see them as a single line at nearly the right spot.

 

[Atomicrox]

Interesting, I had skipped that one because it seemed too simple to work properly

I may just cut some cardboard, buy some razors for the slit and save myself 3 months of waiting for that to arrive. I already have a big sheet of diffraction plastic anyways.

 

[Alaskan]

What do you use for infrared up to 2um?

 

[Atomicrox]

2um is completely invisible, you're gonna need something with a sensor, like a spectrometer. And the grating will have to be proper, which means low resolution on the blue end of the spectrum..

 

[Cyparagon]

They'll sharpen the spectrum you're viewing, which may be handy for a diffuse light source. But as you may know, Lasers are not diffuse. Even if you get one with a scale built in, it will not be much more accurate than your guess. These are handy for some things, but pretty much useless if you want to know the wavelength of a laser.

 

[Rifter]

They'll sharpen the spectrum you're viewing, which may be handy for a diffuse light source. But as you may know, Lasers are not diffuse. Even if you get one with a scale built in, it will not be much more accurate than your guess. These are handy for some things, but pretty much useless if you want to know the wavelength of a laser.

So what would be the best spectroscope that could be used to bin laser diodes?

 

[Alaskan]

What do you use for infrared up to 2um?

I've been looking for one at IR and either I don't know what I'm looking for on ebay, or they just don't show up there often.

 

[Sigurthr]

Unless you're just looking to rule out differences of ~20nm or greater and have a calibration/reference source at one end of the delta wavelength you're going to need a digital spectrophotometer like what RHD, Cyparagon, and others have. I.e. you could pick 470nm diodes from 445nm diodes with these hand spectros, but you can't bin the high wavelength ones.

 

[Atomicrox]

I can see the difference between my high 445nm and my low one by the following procedure:
-Point both dots at the same place on the wall.
-Look at the mixed dot with a grating from 1-2m away.

Of course it isn't good enough to say what the WL is, but it's enough to bin if you have many diodes and a lot of patience