Inverse Adding-Doubling

by Scott Prahl

July 2018

OVERVIEW

Inverse Adding-Doubling is a command-line program that determines the intrinsic optical properties of a flat scattering and absoption sample using measurements of the total reflection and transmission. Basically, optical properties are repeatedly guessed until the calculated reflection and transmission match the measured values.

This package provides two executables ad and iad. The first does a forward adding-doubling calculation (i.e., given the albedo, optical thickness, and anisotropy it returns the total reflection and transmission). The second does the reverse.

This program Prahl et al., Applied Optics, 32, 559-568, 1993 uses the Adding-Doubling method of van de Hulst Multiple Light Scattering, Academic Press, 1978. I extended the Adding-Doubling method to account for Fresnel reflection at boundaries as well as corrections that must accompany integrating sphere experiments.

Finally, integrating spheres do not always collect all the light that exits from the front or back surface of a sample. Since this is impossible to account for the 1D adding-doubling technique, a Monte Carlo simulation is included in the inverse calculation.

Details about using the program are documented in the accompanying manual.

INSTALLATION

In principle, in a unix environment you should be able to just type

make install

to create and install executable versions of the ad and iad programs. See INSTALL.md for more details. Then run

iad test/basic-A.rxt

to translate the reflection and transmission measurements to optical properties in the generated file test/basic-A.txt

For Windows, there are executable binaries ad.exe and iad.exe compiled using MinGW-w64. These apps can be run using the Command Prompt application cmd.exe. These binaries are packaged in a separate iad-win distributions on github or omlc.

Changelog

This is located in the doc/ directory.

Python support

Once you have installed the shared library (.dylib under macOS) or (.so under linux) then you can install python bindings

pip install iadpython

then in Jupyter

import numpy as np
import matplotlib.pyplot as plt
import iadpython as iad

g = np.linspace(0.5,0.8,50)
plt.plot(g, iad.rt(1,1,0.5,1.0,g))
plt.show()

Shared library support.

Edit the Makefile to select the right type of shared library for your platform

make install-lib

Mathematica support.

If you have Mathematica, then (and only if you have installed the right tools and edited the Makefile for your platform) and have the libraries installed then you should be able to type

make mma
make install mma

and then load the iad module and then type

Plot[UR1[0.5,1.0,g], {g,0.5,0.8}]

in Mathematica to get a graph. Very cool.

Author

Scott Prahl

http://omlc.org/~prahl