Bausch + Lomb 39676 Ruled Diffraction Grating

The Lightning Stalker · Feb 12, 2015

Does anyone have an idea of what the line
count is on these? I think the number may
be a serial and not the actual part number.
It's mostly rubbed off and nearly
unreadable. There is also an arrow to
indicate something. Is it maybe something
to do with the blaze? Here is a link to
some pictures if it helps.

Diffraction Grating Fine Ruled Monochrometer Lab Instrument | eBay

Oh, and if you're thinking of buying any
fragile equipment from this guy, I don't
recommend it. He doesn't know how to
handle this stuff properly. The metal
cover was installed on the back like in the
pictures during shipment and it arrived
with some scratches or marring. I think
there is still enough here to work with,
though. I was not happy when I saw it.

Alaskan · Feb 12, 2015

I almost bought that myself, seemed interesting.

The Lightning Stalker · Feb 12, 2015

Yeah, I have never seen a ruled grating for
that cheap. He had no idea what it was
worth. It's just such a shame how it was
packaged. It was obviously perfect when he
took the pictures. It looks like it will
be alright, though. There is still plenty
of usable surface on there.

Cyparagon · Feb 13, 2015

You can calculate the line-count if you know the light wavelength and angle between the orders that the grating produces.

ultimatekaiser · Feb 20, 2015

If it goes in a monochromator I'd hazard a guess it's a low peroidicity echelle grating, not a ruled one. And considering I can't pull up pics on ebay....no idea. But I can say don't try to clean it. Anything touching the surface will destroy it. Gentle compressed air only. They're usually high angle, low period, medium to low lines compared to ruled ones, made for a particular small range/set of wavelengths.

The Lightning Stalker · Feb 21, 2015

ultimatekaiser said:
If it goes in a monochromator I'd hazard a guess it's a low peroidicity echelle grating, not a ruled one. And considering I can't pull up pics on ebay....no idea. But I can say don't try to clean it. Anything touching the surface will destroy it. Gentle compressed air only. They're usually high angle, low period, medium to low lines compared to ruled ones, made for a particular small range/set of wavelengths.

I thought echelle gratings had to be
ruled. If it's ruled doesn't that just
mean it was cut with a ruling engine? It
looks to be a 1350 line grating, which
seems like a common size.

Thanks for your help. This looks like it
will work nicely despite the flaws.

ultimatekaiser · Feb 21, 2015

The Lightning Stalker said:
I thought echelle gratings had to be
ruled. If it's ruled doesn't that just
mean it was cut with a ruling engine? It
looks to be a 1350 line grating, which
seems like a common size.

Thanks for your help. This looks like it
will work nicely despite the flaws.

Echelle are ruled, but with a different geometry IIRC. sorry for being unclear. I think my old rather scratched one is 1200 lines/mm which is quite high so it probably is just a regular plane ruled grating. Most echelle gratings are less than a few hundred lines, with huge blaze angles to my knowledge and are used in high resolution spectrographs.

Cyparagon · Feb 21, 2015

ultimatekaiser said:
...high angle, low period, medium to low lines

I think you've got something backwards. Lower line-count means a smaller diffraction angle (and consequently, more beam orders)

ultimatekaiser · Feb 21, 2015

Cyparagon said:
I think you've got something backwards. Lower line-count means a smaller diffraction angle (and consequently, more beam orders)

dunno the only Echelle I used was over 60 degrees and 300 lines/mm or something crazy like that. i'd have to look at the back of it. I'm certainly no expert. I don't really ever use it.... I prefer my 1800 line plane ruled aluminum grating for most things. I just remember it didn't make huge repeating patterns like the others I've used. but to my knowledge line count and angle are not tied together at all. the angle has to do with the way the ruling was cut. the lines/mm is...well...just that. the number of grooves in a particular space.

The Lightning Stalker · Feb 21, 2015

ultimatekaiser said:
I prefer my 1800 line plane ruled aluminum grating for most things. I just remember it didn't make huge repeating patterns like the others I've used.

Yeah, I noticed the repeating pattern, a
line of dots. It seems to go away and come
back depending on how the laser hits it.

Alaskan · Feb 21, 2015

Curious what you are using the grating for?

The Lightning Stalker · Feb 21, 2015

I see your cat, and raise you a Henry.

It's for a homemade spectrometer.

Alaskan · Feb 21, 2015

Please share the project when ready to do so, now that I have a grating, I could use an example to build from.

This grating has divisions on it of some kind, why? It came out of a Flourometer. http://www.ebay.com/itm/391048944720

Bausch + Lomb 39676 Ruled Diffraction Grating

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