October 27-28—SACRAMENTO, CALIFORNIA: 82nd Annual Gem, Jewelry, Mineral and Rock Show; Sacramento Mineral Society; Sat. 10-5, Sun. 10-4
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Thu Oct 18, 2018 2:32 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 10 posts ] 
Author Message
 Post subject: Can I build a simple spectrometer with this
PostPosted: Sat Jul 21, 2012 2:05 pm 
Offline
Valued Contributor

Joined: Thu Sep 24, 2009 3:44 pm
Posts: 151
Location: Kingman,Az
Ebay has a listing for
Compact Fiber Coupled CCD Spectrometer Kit (DIY)

http://www.ebay.com/itm/Compact-Fiber-C ... 33791fd3d2

I am wondering if I can build a simple ccd spectrometer for gem identification with these parts.
I am blue blind and can not use my OPL to discern much of a spectrum (old eyes).
I was thinking these items would give me the basics to build something similiar to the MDM or Challenger.

Any ideas would be greatly appreciated.

Harold


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Sat Jul 21, 2012 2:39 pm 
Offline
Site Admin
User avatar

Joined: Fri Apr 17, 2009 3:53 pm
Posts: 2048
Location: Sweden
That is possible. One drawback is that it is rather slow. I guess Mikko Åström can chime in on this.

_________________
_____________
Conny Forsberg


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Sat Jul 21, 2012 4:07 pm 
Offline
Valued Contributor

Joined: Wed Oct 22, 2008 5:00 am
Posts: 344
Location: Finland
It is actually quite decent spectrometer for the price. Slowness comes from serial port communication instead of USB bus. Slowness is relative subject. Each spectrum takes about half an second to be transferred to computer. Typically 20-30 spectra are averaged for each dark spectrum, light source spectrum and sample spectrum, so typical measurement time is 30-60 seconds.

This spectrometer has relatively good signal to noise ratio and 16 bit resolution, both very desirable properties.
While not actively cooled it's massive aluminum frame keeps the CCD pretty cool. It has good light sensitivity due to focusing lens on the front of the CCD. Unfortunately this lens is not UV type which means absolute minimum wavelength is about 300nm.

Spectrometer comes with 1800 grooves/mm grating giving small spectral range (about 250nm) and 1nm resolution. I bought another grating (900l/mm) from the same seller for about $80. It gives spectral range from 300 to 860nm with <2nm resolution.

As the seller says this is not a turnkey solution. It takes patience to align (2-5 hours for the first time) and you will need Hg-lamp and neon or argon light source for calibration. Additionally, you will need to do some math with excel for calculating calibration coefficients. If you want to get rid of second order false readings you must provide a red gelatine filter on the front of the CCD. All this is too much for somebody who just wants working product but actually fun if one wants to learn spectroscopy from the bottom up.

The software is pretty basic and allows only scope mode. I have made a small utility program for calculating both transmission and absorption spectra if anyone is interested.

This box is not all u need…there is fibers, light sources, sample chambers, reflection probes etc etc… and I must WARN you. Spectroscopy is costly DISEASE without cure. This cute blue devil just looked so cheap to me as well... :D :D :D

_________________
GemmoRaman GemmoFtir GemmoSphere


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Sat Jul 21, 2012 6:25 pm 
Offline
Valued Contributor
User avatar

Joined: Sat Oct 13, 2007 9:03 am
Posts: 109
Location: Italy
Conny Forsberg wrote:
Spectroscopy is costly DISEASE without cure. This cute blue devil just looked so cheap to me as well... :D :D :D


ah ah ah....it is infecting me too!!!!! :mrgreen:

_________________
Paolo Cerruti G.G. (GIA)

"When the winds of change blow,
some people build walls and others build windmills"

www.paolocerruti.it


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Mon Jul 23, 2012 5:32 pm 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1448
mikko wrote:
This box is not all u need…there is fibers, light sources, sample chambers, reflection probes etc etc…


There is always one more small item, costing between $200 - $20,000, that will make the setup perfect for what you have in mind!


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Wed Jul 25, 2012 1:41 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2642
:twisted: :smt005 :smt043 :smt044


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Fri Aug 10, 2012 6:39 am 
Offline
Established Member
User avatar

Joined: Tue Jul 24, 2012 2:18 am
Posts: 22
Location: Potchefstroom, South Africa
Hi everyone – I’m quite new to the forum but have been dabbling in gemmology (and reading all your posts) for a while. If all goes well I’ll be completing my Gem-A diploma early next year. My questions are all related to Mikko’s previous posts on spectrometers but please feel free to pitch in.

I’ve already ordered a spectrometer from Science Surplus (http://www.science-surplus.com/products/spectrometers) and asked them to fit/install the 900 l/mm grating (365 – 910nm rage) and align the unit before hand. Michael was very helpful and the service I have received to date excellent though the unit will only be here in South Africa in three weeks…

In any case, I have a few questions that I hope you can answer:

1. What type of light source do I need to use to cover the 365 – 910nm range? I was thinking that I can build my own making use of standard of the shelf 12V Osram Xenon Bulbs or maybe HID Xenon 12V car bulbs? The reason I’m looking at a standard Xenon is that it would be easy to replace if it blows – but any advice will be welcome.

2. The guys at Thorlabs can’t ID the components you (Mikko) used on this post:http://gemologyonline.com/Forum/phpBB2/viewtopic.php?f=11&t=14016 (I'm esspecialy intrested in the sampling cage on this one: http://www.timantit.com/laser/spectrometer/DSC01405.gif ). To be precise Yuxin Wang (Thorlabs Applications Engineer) is unable to ID the components used. So giving a bit of detail on the parts used (so I can possibly order them) would be greatly appreciated.

3. Mikko mentioned that a red gelatine filter is required to get rid of second order false readings, is this only required for alignment purposes or am I going to use it regularly for gemstone analysis? If it’s a regular thing and part of my setup is there a specific one you can recommend (I assume that the filter will have to be installed in the light source before light is transmitted through the gemstone)?

4. I am aware of the fact that the unit is far from complete when it is shipped. The only thing that I know is a sure bet, and ordered, is the 5V 3A DC power source as the American 110V AC thing won’t work on our 220V (50Hz) AC power supply here in RSA. The power source aside – what else do I need to get? I’ve been looking at integrating spheres but I’m not quite sure that I need one (I’m not planning on doing opaque materials and the small amount of rough I occasionally do can be cut into very thin slices to do analyses with transmitted light?).

5. Mikko, did you buy a D9 to USB cable or are you running yours directly from the old D9 socket on your PC. These cables are really expensive and I’m not going to fork out 100USD for a cable if it’s not necessary.

6. The small utility program you wrote sounds like “magic” and I will contact you when I finally did ten posts/contributions (and can send personal messages).

Thanks in advance for helping me out…

Bert


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Fri Aug 17, 2012 3:19 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2642
Quote:
1. What type of light source do I need to use to cover the 365 – 910nm range? I was thinking that I can build my own making use of standard of the shelf 12V Osram Xenon Bulbs or maybe HID Xenon 12V car bulbs? The reason I’m looking at a standard Xenon is that it would be easy to replace if it blows – but any advice will be welcome.


A xenon filled quartz halogen such as an Osram Xenophot or a MagLite xenon filled bulb, either run with a variable power supply so that you can juice up the UV output while actually taking the spectrum should do just fine. You won't have as much energy available on shortest wavelength locations.


Unfortunately automotive HID lamps are not pure xenons. They are actually metal halides and have a big line structure in their spectrum which will most likely be too disruptive for spectral measurements. The same line structure that makes them not very useful for lighting gem microscopes.

You could use a 150 watt qh fiber optic illuminator with a blue daylight filter. If you run it all the way up it might put out enough blue.


Quote:
2. The guys at Thorlabs can’t ID the components you (Mikko) used on this post:http://gemologyonline.com/Forum/phpBB2/viewtopic.php?f=11&t=14016 (I'm esspecialy intrested in the sampling cage on this one: http://www.timantit.com/laser/spectrometer/DSC01405.gif ). To be precise Yuxin Wang (Thorlabs Applications Engineer) is unable to ID the components used. So giving a bit of detail on the parts used (so I can possibly order them) would be greatly appreciated.

That piece actually looks kind of homemade to me. In any case there are lots of ways to skin that cat. Search Newport Research and Edmund Optics. Ocean Optics , Avantes and many others have the kind of hardware for this purpose. Of course the best place to look is ebay. These optical legos are very very expensive when bought new for list price.


Quote:
3. Mikko mentioned that a red gelatine filter is required to get rid of second order false readings, is this only required for alignment purposes or am I going to use it regularly for gemstone analysis? If it’s a regular thing and part of my setup is there a specific one you can recommend (I assume that the filter will have to be installed in the light source before light is transmitted through the gemstone)?


When using a diffraction grating spectrometer , depending on the design it may be necessary to include an order sorting filter. The grating makes multiple rainbows that overlap and when you use color filters you can eliminate the overlapping spectrum. But the necessity depends on the design of the spectrometer and the grating. The guys at Science Surplus probably know whether an order sorting filter is required. The guys at BW Tek would know for certain. Sometimes they paint these onto the detector window glass.
Quote:
4. I am aware of the fact that the unit is far from complete when it is shipped. The only thing that I know is a sure bet, and ordered, is the 5V 3A DC power source as the American 110V AC thing won’t work on our 220V (50Hz) AC power supply here in RSA. The power source aside – what else do I need to get? I’ve been looking at integrating spheres but I’m not quite sure that I need one (I’m not planning on doing opaque materials and the small amount of rough I occasionally do can be cut into very thin slices to do analyses with transmitted light?).


Even on ebay integrating spheres cost a few hundred dollars. I would wait until you receive the unit and have familiarized yourself with it and gotten some spectra. A sampling chamber can also be flat black. Get some flat black barbeque grill spray at the hardware store and make a sample chamber out of a can to start with. But your xenon lamp in the bottome and have a deck with a hole to put the gemstone on with washers painted black to adjust the size. Let the lamp shine on the table facet and collect light from the pavillion.

You might want to buy or make a collection lens. Find some quartz lenses to use for good UV transmission.


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Mon Jun 10, 2013 10:54 am 
Offline
New to the Forum or The Quiet Type

Joined: Fri Jun 07, 2013 2:18 pm
Posts: 2
Bert wrote:
1. What type of light source do I need to use to cover the 365 – 910nm range? I was thinking that I can build my own making use of standard of the shelf 12V Osram Hid Kits or maybe HID Xenon 12V car bulbs? The reason I’m looking at a standard Xenon is that it would be easy to replace if it blows – but any advice will be welcome.


Just use xenon HID bulb. It is %300 brighter than halogen bulb.


Top
 Profile  
Reply with quote  
 Post subject: Re: Can I build a simple spectrometer with this
PostPosted: Sun Jun 23, 2013 9:34 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2642
Quote:
Unfortunately automotive HID lamps are not pure xenons. They are actually metal halides and have a big line structure in their spectrum which will most likely be too disruptive for spectral measurements. The same line structure that makes them not very useful for lighting gem microscopes.


If you meant regular xenon short arc lamps (NOT automotive) those are indeed the best light source there is for any purpose. Color matching, spectroscopy, photography, stone color evaluation.

Automotive lamps are more or less useless for the above purposes. They can be useful if color rendition does not have to be perfect. But useless as a spectroscopic source. Never used in ANY professional instrumentation.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock