Identification of Sir Raman's handheld scope

I read an article somewhere around 5-10 years ago that talked a little bit about the life of Sir C. V. Raman. The focus was on the effect of Raman spectroscopy but included an interesting little tidbit. 


Sir Raman apparently used to carry a small handheld scope of some description which allowed him to examine an object and only see the scattered light. He would always keep it in his pocket so that he could pick a flower or look at an everyday object and see how it changed. The article included a photo of him using it. I think I even remember seeing a video of him using it. As I recall, it was a small tube, about a hands length in size, and I think it was made from brass. 


**What was that tube, how did it work, and is there a resource for me to get one of my own?**




I think you are referring to a handheld prism based spectroscope with an eye-view/eyepiece. Using such spectroscope one does not observe Raman signal but only observe the dispersed light coming from an object giving information about the absorption characteristics of the object or emission characteristics (for light sources).


The following is such device (personal photo).


[![enter image description here](https://i.stack.imgur.com/8wQcmm.jpg)](https://i.stack.imgur.com/8wQcmm.jpg)


Here is a ray diagram for understanding the working principle. White light is the light entering the device. Yellow lines are normal. (Other ways to achieve this are possible, hence this ray diagram is only an example.) On the right, is the image taken from the eyepiece of the device using a cell phone. Sun light has continuous spectra, while white fluorescent lamp (Hg vapor based) shows distinct lines. (Ray diagram is drawn by me. Images shown on the right are captured by me.)


[![Ray diagram](https://i.stack.imgur.com/F8i1V.png)](https://i.stack.imgur.com/F8i1V.png)


Such device works using prism(s) to achieve dispersion. The amount of dispersion provided by the spectroscope is a parameter governed by the prism used. Higher the dispersion, more fine grained are wavelengths of light dispersed and in such cases one may need to move the eye or (prism) to see full range of spectrum. 


Prism based spectroscopes are frequently used for studying gems and diamonds. White light which passes through such samples undergoes absorption (usually by the minor impurities, which imparts color) and the dispersed light gives this information.


You can easily make such portable spectroscope using combination of small optical quality glass prisms. (Or you can just buy, available on Amazon and some companies dealing with optics sell these.)




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About observing Raman signal using eyes, it is very difficult since Raman signal is very weak, but it is possible. As per my knowledge no commercial product exists which can do that.


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Sir Martyn Poliakoff did the video about the [spectroscope](https://www.youtube.com/watch?v=_UET11Pt6Qw) on his Periodic Videos channel on youtube. 


To my knowledge, he presented the original instrument but did not mention where to obtain a replica.


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