What is a spectrometer? A nice Youtube video by NC Community College exists which answers this question: http://www.youtube.com/watch?v=xHQM4BbR040.
- A typical one has one source, an input slit, a diffraction grating with its angle from the slit modifiable via a nob, an exit slit, a sample bay, and a detector.
- The source emits light.
- The emitted light goes through the input slit.
- A beam of light through the slit reaches the diffraction grating and gets split into an array of different colors beams.
- By the nob, an angle of diffraction grating is changed, and the beam of a single color going through the exit slit is selected.
- The beam of the selected color shines the sample at the sample bay.
- The detector measures the transmittance and the absorbance of the sample at the selected wavelength.
- With the nob control, the experiment can be repeated for different wavelengths.
- The transmittance pattern and the absorbance pattern across different wavelengths can be collected and drawn into graphs.
- These patterns in graphs are compared with the patterns found in a library of known materials.
- The item in the library that matches most well with that of the sample is determined to be included in the sample.
- What should we do when there are many materials included in the sample? For example, suppose a cup of water in which several different substances are dissolved.
- The spectrometer problem has estimation and detection questions, learning and classification questions.
Can we make a spectrometer? Yes!!!
- 10$ spectrometer
- There is a publiclab.org spectrometer. They teach how to make a $10 spectrometer. They have smartphone base and PC base spectrometers.
- http://publiclab.org/wiki/spectrometer. They are made of very cheap USB web camera for PC version.
Now I have a transmittance pattern.
Where can I obtain the library of known materials so that I can compare the transmittance pattern of my sample with those included in the library?
Spectral library of known materials 을 얻어야 함. Public 일 것 같은데.
- There are a total of 647 spectra published in a gemological Raman and photoluminescence library: http://www.gemmoraman.com/Libraries.aspx.