Diffuse Reflectance in time domain

[zahra R.fathi]

Hello,

I am trying to calculate the diffuse reflectance on one detector from the semi-infinite medium. There is an example that calculates the diffuse reflectance in the steady state( drefmc = mcxcwdref(detp, cfg))

Now I am confused about how to use it in the time domain.
Could you clarify this problem for me?

Thanks

[Qianqian Fang]

hi Zahra,

Shijie Yan, my student who wrote mcxcwdref and the below validation script, was mostly focused on the CW case

https://github.com/fangq/mcx/blob/v2023/mcxlab/examples/demo_diffuse_reflectance_validation.m#L70

although, as you can see from his comments, the referred equation, Eq. 8 of Kienle 1997 paper (https://opg.optica.org/josaa/fulltext.cfm?uri=josaa-14-1-246&id=1660) is suitable for both time-resolved or steady-state dref (if using diffusion theory).

for MC, you can modify the below for-loop of mcxcwdref.m to accumulate a time-series for each detector, by calling mcxdettpsf.m (https://github.com/fangq/mcx/blob/v2023/utils/mcxdettpsf.m) instead of a single value for each detector

https://github.com/fangq/mcx/blob/v2023/utils/mcxcwdref.m#L28-L30

the output dref should be converted to the time-domain.

Qianqian

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[zahra R.fathi]

Dear Prof. Fang,

Thank you very much for your response.  I tried to plot diffuse reflectance in time domain according to your advice and I used the 

https://github.com/fangq/mcx/blob/v2023/utils/mcxcwdref.m#L28-L30

function for the time domain, however, the magnitude of the reflectance is not in agreement with Figure 1.  I was wondering if you could guide me through this confusion.

time = [twin(1), twin(end), cfg.tstep];% save positions & directions of escaping photons

[fluence,detp]=mcxlab(cfg);

tpsf = mcxdettpsf(detp,1,cfg.prop,time);

area = pi * (cfg.detpos(:,4)).^2;

td= tpsf./cfg.nphoton; % Eq.12 of photon replay paper[Yao2018]

semilogy(twin(1,1:length(tpsf)).*1e9 , td./area)

Thank you very much for your time.

Sincerely yours,

Zahra