I am reading about the Diffuse Correlation Spectroscopy for non-invasive, micro-vascular cerebral blood flow measurament.The device used for the topic is a combination of DCS+NIRS/DOS.
The system employs continous-wave lasers in the NIR and the light is delivered to tissue via a multi-mode fiber.
The detected light is often collected by single-mode fiber, sometimes by few-mode fibers and this is a limitation because the detectors are small and the light collection via the fibers is sensitive to the presence of hair.
Light detection is done by fast photon counting detectors like Photomultipliers or single-photon counting avalanche photo-diodes.
The electrical output of the detector is converted into a TTL pulse (one for each detected photon) and fed to a digital autocorrelator board.The output of the autocorrelator is the DCS intensity autocorrelation function from which i could calculate the Blood Flow Index.
How would I design a new device based on OEM detectors, sources and FPGA's? What kind of cost, size reduction?
Could you suggest me new technologies for sourses,detectors and FPGA?
Hi, for lasers, check the website of FITEL (=FURUKAWA) they have highly reliable lasers in the telecommunication window. For other wavelengths see NEL or NANOSYS.
For the detectors, check HAMAMATSU, THORLABS, NEWPORT...
Rergarding to the FPGA and the data processing,what photon rate (count/sec) do you estimate?
David
Many thanks but maybe my question is not done so well. I meant ...could I use other different tools to reach the same goal, maybe in a better way?
For example.... could I use LED or quantum dots laser instead of a continous-wave laser?
could I use quantum dots detectors instead of Photomultipliers or single-photon counting avalanche photo-diodes.?
would be realistic and possible? and what kind of advantages there will be?
about FPGA the photon rate used is less than 50(count/s), could you suggest me somethign?
Thank you so much!!
Hi, what is the exact wavelength used? It might be a good choice to use fiber coupled DFB laser diodes which are highly reliable. For detection, it is very convenient to use SiPMs (arrays) which are less susceptible than common photo multipliers or APDs. Sources are SensL oder Ketek. If you expect a count-rate of 50 1/s, the use of FPGAs is unneccessarry. I would recommend to use a cheap micro-controller instead.
Hi Stephan :D, many thanks for the answer!!
In order to provide a better solution or, anyway, different solutions ( also in terms of coast and dimensions)compared to that one described in the question, I need to change sources,detectors and FPGA used in the experiment that I talked about in my first question.
The device ( DCS-NIRS/DOS) utilizes:
SOURCES:narrow-bandwidth lasers operating at 785 nm with a coherence length of 10m.
DETECTORS: photomultipliers and SPADs.
FPGA : digital correlator board.( the article I was reading talks also about a multi-tau delay time scheme for the temporal autocorrelation function). The article doesn't talk about the count-rate..this is the problem. I thought it was 50 1/s but I really don't know, and I can't reflect about FPGA because this is not the best part of my knowledge.
For this reason I asked an help.
I was thinking about QD lasers or LED for sources. I found QD laser cheaper and of smaller dimension compared to the classic laser used but QD laser wavelength in the market is 1000-1300 nm, With this higher wavelength compared to that one used in the experiments which would be the effect? it will be better or worst?
What kind of LED could be considered and why?
I was reading about the advantegs of fiber coupled DFB laser diodes that you suggested me. I will let you know about it!
I will investigate about the detectors you suggested me.
I will be very thankfull if you will help me, I'm in bed waters at this moment.
Thx so much!!!!
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