Hi SCIUSCIA,
As per my understanding of the question, you are using a monochromatic light source to capture images and want to convert it to a spectrum in the range of frequency or wavelength.
According to my knowledge of monochromatic light sources, these types of sources give out a single wavelength/frequency. Hence, the question of making a spectrum of an image captured by such a source makes sense only if you are somehow varying the source wavelength.
In either case, I don’t think that there is use of calibration curves.
This is my assumption of the question, and the answer is according to the assumption. Please feel free to follow up in comments if you think I misunderstood or have missed a point.
Hope this helps!
Regards
Akshat
