Hello, dear researchers, I want to ask that I am using the system as shown in figure 2. I performed an experiment and I measured total reflected intensity from the CCD as shown in figure 1(a). I used the visible light source. I want to make line graph between Qext and Qscat. Vs the wavelength 400 nm to 700 nm range. For this issue, I have extracted the data in the form of the circle in MATLAB and plotted it as shown in figure 1(b). Now Can I put wavelength 400nm to 700 nm on the horizontal axis or not? Is this is a right way to plot and extracting data? I have also performed this by extracting the data by the horizontal line and take a mean of all line and plotted as in figure 1(c).
Now I want to ask that which way is better for plotting the line graph in which I can take wavelength on x-axis?
How can Calculate Qscat? Is this is equal to reflection intensity?
Can I calculate Qabs=1-Qsca, Qext=Qabs+Qsca? Or what is the right way?
Dear Zoubair, I know there are various numerical techniques which can give us Qext in which Mie is the exact solution. Please read the question carefully, this looks simple but in fact it is not. thanks.
Dear Kaleem,
>For this issue, I have extracted the data in the form of the circle in MATLAB and plotted it as shown in figure 1(b).
Do you mean that you take color image by kind of CCD camera and try to decompose it according its R,G,B components? If so, your spectra will be very questionnable, especially if you use for such "spectroscopy" image in JPG format. Only careful analysis image in RAW format can give very approximate presentation of spectral information. And even more, to estimate such spectra you have to know spectral characteristics of these R,G,B channels.
By the way, angular position of dichroic mirror on your layout should be rotated 90°
@Valeriy Sterligov thanks for your reply. In circle case, I took RGB value in the form of the circle around the particle. But question is that without spectrometer should it be plotted intensity Vs angle, not wavelength.
Basically, from CCD, I took the data and import it in Matlab and by making a program I extracted data in the form of the circle for any radius around the particle. It looks like spectra but in fact it is not. I want to know how can I plot the scattering spectra???
Dear Kaleem, what are R,G,B data? This is convolution of spectral sensitivity characteristic of each color channel and spectra you study. So value of each color channel result gives you practically nothing about value of your spectra. This is the reason why you can't extract spectra from your image. Even more, as I told in my previous post, even if you have monochromatic image, its non-linear and not known processing when producing image in JPG format prevents you from recovering information about intensity of each pixel. So reply on your general question is negative. It is not possible to obtain spectra from color image. And recovery of even monochromatic image intensity is very challenging process.
dear Valeriy Sterligov , I am talking about the data which I directly get from CCD. please tell me, have you an idea If I calculated Stokes parameter then can I measure scattering spectra from Stokes parameters (because we can find out the angle from stokes)?
or I have Stokes, azimuthal angle(phi) , retardation angle(delta), any of the described polarization parameter can help me to extract out the spectra???
any other idea to find out the spectra ???
No, as I explained you in last message, any treatment don't enable you to obtain spectra from RGB image. You should use appropriate to your task spectrometer.
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