Published: 2019-10-30 | Categories: [»] Engineering, [»] Opticsand[»] Chemistry.

Those of you who have been following me certainly know that I have been extensively working on a DIY Raman spectrometer with top-notch professional features such as a 12 cm-1 resolution at low cost. The truth is that I had been working on this project for several years and it was until recently that I got the results I have now shared with you. Today, a new milestone has been reached with the official release of OpenRaman, a fully open source Raman spectrometer. But before we talk about it, I would like to step a few years back in time.

The story actually begun in 2014 where I successfully recorded the Raman spectra of a PMMA fiber using a simple [»] spectrophotometer setup. The spectrometer was however not sensitive enough to record Raman signal of common solvents due to the low light efficiency I had at that time. However, the signal of a PMMA fiber is so strong that you cannot miss it. This experiment is really easy to perform and I urge you to try it at home if you haven’t done it yet!

I had to wait November 2016 to record my first Raman spectra of a liquid (ethyl acetate). The resolution was not so good (about 30 cm-1) and I had little signal but the various peaks of the solvent were clearly there! I was extremely happy with this result (I was literally dancing in my lab - seriously) that I decided to continue working secretly on this very hot project. It was however too soon to release any article as I wanted it to be perfect!

2016 is also the year I was promoted as contact person for camera-related questions at the company I’m working for, which allowed me to dig a little bit into camera technology by both discussing directly with many suppliers and also by experimenting directly with detectivity threshold levels. It is by that mean that I discovered that some cameras have extremely low detection thresholds of only a few photons. This is serious and not a commercial scam: I tested the camera I’m currently using to a detectivity of 4 photons per pixel. My colleagues were a bit sceptical in a first place but the experimental result was talking by itself!

In 2017 I had the chance to join an ESA (European Space Agency) training of 1 week in a 5 stars, sea-shore, hotel in Italy about Optical Design for Space at which occasion I started learning about optical design. The training ended-up containing only a very small introduction to optical design (most of it was more dedicated to system level management of space instruments) but I was so stressed that people would laugh at me due to some lack of skills in optics that I read as many books as I could about optical design before I went there. It is just before the training that I wrote my very first raytracing program which helped me conducting my first [»] microscopy objective I shared with you. By the way, I was way ahead of most people in the training on the topic – at the exception of one or two guys from Airbus who were actual senior optical designers. All of that just to hide that I had no clue what a lens actually was :) All of these efforts were not done in vain because in mid-2018 I was promoted part-time optical designer at the office, in addition to the work I was already doing as a system engineer. I gained there access to professional optical design softwares and time to actually practice my design skills.

All of these put together allowed me to produce a revised version of my [»] 400-800 nm spectrometer in March 2018 which ultimately yielded the first version of the [»] DIY Raman spectrometer during 2018 winter holiday. The first few months of 2019 were dedicated to increasing the performances of both the [»] imaging part, [»] cuvette and [»] light source of the spectrometer.

At that time, it was relatively clear that this experiment went way beyond the simple intend of the usual experiments I perform here. Because I was deeply convinced of the great potential of a full DIY Raman spectrometer with professional performances, I decided to pursue the journey and open a dedicated website to summarize the conception and construction of replicas.

The address of the new website is [∞] http://www.open-raman.org. Bookmark it as it is going to hit hard the DIY scientific community! The official price target is <2000 EUR for 12 cm-1 and ultra-high SNR on common solvents!

The new website is more structured on how to assemble your own version of the spectrometer and has some exclusive content such as Bill of Materials and how-to pictures. Apart from that, I will continue posting the results here although the format may be slightly different. So, check both websites to stay tuned for updates :)

To be honest with you, I initially wanted to release the website once I would have solved the laser issue. If you haven’t followed all the details, the current spectrometer is fully operational but the cheap (but great) $150 laser I’m using requires a $3000 current and TEC driver at the moment. The laser driver I’m using is clearly overkill in terms of performances (like superfast modulation and so on) but I’m struggling to replace it with cheaper alternative. My attempt at an improved [»] 1 Amp current driver resulted in a fried laser and a $500-worth of PCBs and electronic components that are now useless (I purchased enough to build 5 prototypes as I regularly do). Driving the laser also requires a TEC system with its mechanical interface which also takes some time. I’m progressing on all these theatre of operations (it has really been a war these last few months) but I haven’t anything to show for yet. A few months have pasted since and I still feel like I haven’t done a single step forward. All of that put together, I decided to release the website now so that you can already benefit from it :) I will advertise later on external websites such as youtube, when a prototype is operational.

I have created basically two parts in the new website. The first part contains the assembly instructions which are much more detailed than what I presented on thepulsar.be. It contains really everything you need to reproduce the spectrometer at home, even with very little background in optics. The second part of the website, currently empty, will be technical articles that highlight both the design of the spectrometer and experiments done with it. To give you an example, I’m currently working on several chemical reaction for which I would like to either assess the purity of the product using spectroscopy or to study the reaction kinetic. I already have one experiment scheduled for the end of this week! This second part is much more like the article you have on thepulsar.be except that they will probably be slightly shorter. Anyway, you will find the content for the experiments on both of the websites.

Last but not least, you may have noticed a new button in the menu which says [∞] “donate!”. As mentioned in an earlier post, I have decided to open a Patreon account to collect some money to perform the experiments. This is not motivated in any way by a form of lucre but simply because I cannot spend the kind of money I used to on my projects anymore. I recently became a Daddy of a wonderful little girl and I was honestly horrified to see how much the daycare ladies were asking for :-/ Since I don’t have much choice, I had to cut on my expenses baddly… So from now on I really have to think twice before placing an order for $500-worth of PCBs! More seriously, I just can’t do that anymore and I will have to focus on a more reasonable $50/month maximum. The idea of the Patreon account is to collect some money to finish the spectrometer first using a much rationale as I can (I promise not to throw that money away!). I have no idea if it will work or not but, please, please, if you like what you read here, consider donating – even as little as $1 is already something at the moment!

That being said, I hope to see you shortly for more science!

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