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SimulateSpectrum.cpp 19.5 KB
da3d4e0e   dmayerich   Initial commit.
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  #include <math.h>
  #include <complex>
  #include <iostream>
  #include <fstream>
  #include "globals.h"
  //#include "cufft.h"
  using namespace std;
  
  #define pi 3.14159
  
  typedef complex<float> scComplex;
  
  int cbessjyva(double v,complex<double> z,double &vm,complex<double>*cjv,
      complex<double>*cyv,complex<double>*cjvp,complex<double>*cyvp);
  int bessjyv(double v,double x,double &vm,double *jv,double *yv,
      double *djv,double *dyv);
  
  complex<double> Jl_neg(complex<double> x)
  {
  	//this function computes the bessel function of the first kind Jl(x) for l = -0.5
  	return ( sqrt(2.0/pi) * cos(x) )/sqrt(x);
  }
  
  double Jl_neg(double x)
  {
  	//this function computes the bessel function of the first kind Jl(x) for l = -0.5
  	return ( sqrt(2.0/pi) * cos(x) )/sqrt(x);
  }
  
  double Yl_neg(double x)
  {
  	//this function computes the bessel function of the second kind Yl(x) for l = -0.5;
  	return ( sqrt(2.0/pi) * sin(x) )/sqrt(x);
  }
  
  void computeB(complex<float>* B, float radius, complex<double> refIndex, float lambda, int Nl)
  {
  	double k = (2*pi)/lambda;
  	int b = 2;
  
  	//allocate space for the real bessel functions
  	double* jv = (double*)malloc(sizeof(double)*(Nl+b));
  	double* yv = (double*)malloc(sizeof(double)*(Nl+b));
  	double* jvp = (double*)malloc(sizeof(double)*(Nl+b));
  	double* yvp = (double*)malloc(sizeof(double)*(Nl+b));
  
  	//allocate space for the complex bessel functions
  	complex<double>* cjv = (complex<double>*)malloc(sizeof(complex<double>)*(Nl+b));
  	complex<double>* cyv = (complex<double>*)malloc(sizeof(complex<double>)*(Nl+b));
  	complex<double>* cjvp = (complex<double>*)malloc(sizeof(complex<double>)*(Nl+b));
  	complex<double>* cyvp = (complex<double>*)malloc(sizeof(complex<double>)*(Nl+b));
  
  	double kr = k*radius;
  	complex<double> knr = k*refIndex*(double)radius;
  	complex<double> n = refIndex;
  
  	//compute the bessel functions for k*r
  	double vm;// = Nl - 1;
  	bessjyv((Nl)+0.5, kr, vm, jv, yv, jvp, yvp);
  	//cout<<"Nl: "<<Nl<<"  vm: "<<vm<<endl;
  	//printf("Nl: %f, vm: %f\n", (float)Nl, (float)vm);
  
  	//compute the bessel functions for k*n*r
  	cbessjyva((Nl)+0.5, knr, vm, cjv, cyv, cjvp, cyvp);
  
  	//scale factor for spherical bessel functions
  	double scale_kr = sqrt(pi/(2.0*kr));
  	complex<double> scale_knr = sqrt(pi/(2.0*knr));
  
  	complex<double> numer, denom;
  	double j_kr;
  	double y_kr;
  	complex<double> j_knr;
  	complex<double> j_d_knr;
  	double j_d_kr;
  	complex<double> h_kr;
  	complex<double> h_d_kr;
  	complex<double> h_neg;
  	complex<double> h_pos;
  
  	//cout<<"B coefficients:"<<endl;
  	for(int l=0; l<Nl; l++)
  	{
  		//compute the spherical bessel functions
  		j_kr = jv[l] * scale_kr;
  		y_kr = yv[l] * scale_kr;
  		j_knr = cjv[l] * scale_knr;
  
  		//compute the Hankel function
  		h_kr = complex<double>(j_kr, y_kr);
  
  		//compute the derivatives
  		if(l == 0)
  		{
  			//spherical bessel functions for l=0
  			j_d_kr = scale_kr * (Jl_neg(kr) - (jv[l] + kr*jv[l+1])/kr )/2.0;
  			j_d_knr = scale_knr * ( Jl_neg(knr) - (cjv[l] + knr*cjv[l+1])/knr )/2.0;
  			h_neg = complex<double>(scale_kr*Jl_neg(kr), scale_kr*Yl_neg(kr));
  			h_pos = complex<double>(scale_kr*jv[l+1], scale_kr*yv[l+1]);
  			h_d_kr = (h_neg - (h_kr + kr*h_pos)/kr)/2.0;
  		}
  		else
  		{
  			//spherical bessel functions
  			j_d_kr = scale_kr * (jv[l-1] - (jv[l] + kr*jv[l+1])/kr )/2.0;
  			j_d_knr = scale_knr * ( cjv[l-1] - (cjv[l] + knr*cjv[l+1])/knr )/2.0;
  			h_neg = complex<double>(scale_kr*jv[l-1], scale_kr*yv[l-1]);
  			h_pos = complex<double>(scale_kr*jv[l+1], scale_kr*yv[l+1]);
  			h_d_kr = (h_neg - (h_kr + kr*h_pos)/kr)/2.0;
  		}
  
  		numer = j_kr*j_d_knr*n - j_knr*j_d_kr;
  		denom = j_knr*h_d_kr - h_kr*j_d_knr*n;
  		complex<double> temp =  numer/denom;
  
  		B[l] = scComplex(temp.real(), temp.imag());
  		//cout<<B[l]<<endl;
  	}
  
  	free(jv);
  	free(yv);
  	free(jvp);
  	free(yvp);
  	free(cjv);
  	free(cyv);
  	free(cjvp);
  	free(cyvp);
  }
  
  void Legendre(float* P, float x, int Nl)
  {
  	//computes the legendre polynomials from orders 0 to Nl-1
  	P[0] = 1;
  	if(Nl == 1) return;
  	P[1] = x;
  	for(int l = 2; l < Nl; l++)
  	{
  		P[l] = ((2*l - 1)*x*P[l-1] - (l - 1)*P[l-2])/l;
  	}	
  
  }
  
  complex<float> integrateUi(float cAngleI, float cAngleO, float oAngleI, float oAngleO, float M = 2*pi)
  {
  	/*This function integrates the incident field of magnitude M in the far zone
  	in order to evaluate the field at the central pixel of a detector.
  	cNAi = condenser inner angle
  	cNAo = condenser outer angle
  	oNAi = objective inner angle
  	oNAo = objective outer angle
  	M = field magnitude*/
  
  	float alphaIn = max(cAngleI, oAngleI);
  	float alphaOut = min(cAngleO,oAngleO);
  
  	complex<float> Ui;
  	if(alphaIn > alphaOut)
  		Ui = complex<float>(0.0, 0.0);
  	else
  		Ui = complex<float>(M * 2 * pi * (cos(alphaIn) - cos(alphaOut)), 0.0f);
  
  	return Ui;
  
  }
  
  void computeCondenserAlpha(float* alpha, int Nl, float cAngleI, float cAngleO)
  {
  	/*This function computes the condenser integral in order to build the field of incident light
  	alpha = list of Nl floating point values representing the condenser alpha as a function of l
  	Nl = number of orders in the incident field
  	cAngleI, cAngleO = inner and outer condenser angles (inner and outer NA)*/
  
  	//compute the Legendre polynomials for the condenser aperature
  	float* PcNAo = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PcNAo, cos(cAngleO), Nl+1);
  	float* PcNAi = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PcNAi, cos(cAngleI), Nl+1);
  
  	for(int l=0; l<Nl; l++)
  	{
  		//integration term
  		if(l == 0)
  			alpha[l] = -PcNAo[l+1] + PcNAo[0] + PcNAi[l+1] - PcNAi[0];
  		else
  			alpha[l] = -PcNAo[l+1] + PcNAo[l-1] + PcNAi[l+1] - PcNAi[l-1];
  
  		alpha[l] *= 2 * pi;
  	}
  
  }
  
  complex<float> integrateUs(float r, float lambda, complex<float> eta, 
  						   float cAngleI, float cAngleO, float oAngleI, float oAngleO, float M = 2*pi)
  {
  	/*This function integrates the incident field of magnitude M in the far zone
  	in order to evaluate the field at the central pixel of a detector.
  	r = sphere radius
  	lambda = wavelength
  	eta = index of refraction
  	cNAi = condenser inner NA
  	cNAo = condenser outer NA
  	oNAi = objective inner NA
  	oNAo = objective outer NA
  	M = field magnitude*/
  
  	//compute the required number of orders
  	float k = 2*pi/lambda;
  	int Nl = ceil( k + 4 * exp(log(k*r)/3) + 3 );
  
  	//compute the material coefficients B
  	complex<float>* B = (complex<float>*)malloc(sizeof(complex<float>)*Nl);
  	//compute the Legendre polynomials for the condenser and objective aperatures
  	float* PcNAo = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PcNAo, cos(cAngleO), Nl+1);
  	float* PcNAi = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PcNAi, cos(cAngleI), Nl+1);
  
  	float* PoNAo = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PoNAo, cos(oAngleO), Nl+1);
  	float* PoNAi = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PoNAi, cos(oAngleI), Nl+1);
  
  	//store the index of refraction;
  	complex<double> IR(eta.real(), eta.imag());
  	
  	//compute the scattering coefficients
  	computeB(B, r, IR, lambda, Nl);
  
  	//aperature terms for the condenser (alpha) and objective (beta)
  	float alpha;
  	float beta;
  	float c;
  	complex<float> Us(0.0, 0.0);
  
  	for(int l=0; l<Nl; l++)
  	{
  		//integration term
  		if(l == 0)
  		{
  			alpha = -PcNAo[l+1] + PcNAo[0] + PcNAi[l+1] - PcNAi[0];
  			beta = -PoNAo[l+1] + PoNAo[0] + PoNAi[l+1] - PoNAi[0];
  		}
  		else
  		{
  			alpha = -PcNAo[l+1] + PcNAo[l-1] + PcNAi[l+1] - PcNAi[l-1];
  			beta = -PoNAo[l+1] + PoNAo[l-1] + PoNAi[l+1] - PoNAi[l-1];
  		}
  		c = (2*pi)/(2.0 * l + 1.0);
  		Us += c * alpha * beta * B[l] * M;
  		
  			
  	}
  	free(PcNAo);
  	free(PcNAi);
  	free(PoNAo);
  	free(PoNAi);
  	free(B);
  
  	return Us;
  
  }
  
  void pointSpectrum()
  {
  	PD.StartTimer(SIMULATE_SPECTRUM);
  	//clear the previous spectrum
  	SimSpectrum.clear();
  
  	float dNu = 2.0f;
  	float lambda;
  	
  	//compute the angles based on NA
  	float cAngleI = asin(cNAi);
  	float cAngleO = asin(cNAo);
  	float oAngleI = asin(oNAi);
  	float oAngleO = asin(oNAo);
  
  	//implement a reflection-mode system if necessary
  	if(opticsMode == ReflectionOpticsType){
  		
  		//set the condenser to match the objective
  		cAngleI = oAngleI;
  		cAngleO = oAngleO;
  
  		//invert the objective
  		oAngleO = pi - cAngleI;
  		oAngleI = pi - cAngleO;
  	}
  
  	//integrate the incident field at the detector position
  	complex<float> Ui = integrateUi(cAngleI, cAngleO, oAngleI, oAngleO, 2*pi);
  	float I0 = Ui.real() * Ui.real() + Ui.imag() * Ui.imag();
  	I0 *= scaleI0;
  
  	
  
  	float I;
  	SpecPair temp;
  	float nu;
  	complex<float> eta;
  	complex<float> Us, U;
  
  	float vecLen = 0.0;
  	for(int i=0; i<EtaK.size(); i++)
  	{
  		nu = EtaK[i].nu;
  		lambda = 10000.0f/nu;
  		if(applyMaterial)
  			eta = complex<float>(EtaN[i].A, EtaK[i].A);
  		else
  			eta = complex<float>(baseIR, 0.0);
  
  
  		//integrate the scattered field at the detector position
  		Us = integrateUs(radius, lambda, eta, cAngleI, cAngleO, oAngleI, oAngleO, 2*pi);
  		U = Us + Ui;
  		float I = U.real() * U.real() + U.imag() * U.imag();
  		
  		temp.nu = nu;
  
  		//set the spectrum value based on the current display type
  		if(dispSimType == AbsorbanceSpecType)
  			temp.A = -log10(I/I0);
  		else
  			temp.A = I;
  
  		if(dispNormalize)
  			vecLen += temp.A * temp.A;
  		
  		SimSpectrum.push_back(temp);		
  	}
  	vecLen = sqrt(vecLen);
  
  	if(dispNormalize)
  		for(int i=0; i<SimSpectrum.size(); i++)
  			SimSpectrum[i].A = (SimSpectrum[i].A / vecLen) * dispNormFactor;
  
  	PD.EndTimer(SIMULATE_SPECTRUM);
  }
  
  /*
  complex<float> sampleUs(complex<float>* B, float* Alpha, int Nl, float r, 
  						   float cAngleI, float cAngleO, float theta, float M = 2*pi)
  {
  	/*This function takes a point sample of the scattered field in the far zone
  	in order to evaluate the field at the central pixel of a detector.
  	r = sphere radius
  	lambda = wavelength
  	eta = index of refraction
  	cNAi = condenser inner NA
  	cNAo = condenser outer NA
  	theta = angle of the sample
  	M = field magnitude*/
  
  /*
  	//compute the material coefficients B
  	//complex<float>* B = (complex<float>*)malloc(sizeof(complex<float>)*Nl);
  
  	//compute the Legendre polynomials for theta (at the objective)
  	float* Ptheta = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(Ptheta, cos(theta), Nl+1);
  
  	//complex<double> IR(eta.real(), eta.imag());
  
  	//aperature terms for the condenser (alpha) and objective (beta)
  	float beta;
  	float c;
  	complex<float> Us(0.0, 0.0);
  
  	for(int l=0; l<Nl; l++)
  	{
  
  		complex<float> numer(0.0, -(l*pi)/2.0);
  		Us += B[l] * exp(numer) * Ptheta[l] * Alpha[l] * pow(complex<float>(0.0, 1.0), l);
  		
  			
  	}
  	//printf("Ptheta: %f\n", Ptheta[Nl-1]);
  
  	return Us;
  
  }*/
  
  
  /*
  void detectorSpectrum(int numSamples)
  {
  	//integrate across the objective aperature and calculate the resulting intensity on a detector
  	PD.StartTimer(SIMULATE_SPECTRUM);
  	//clear the previous spectrum
  	SimSpectrum.clear();
  
  	float dNu = 2.0f;
  	float lambda;
  	
  	//compute the angles based on NA
  	float cAngleI = asin(cNAi);
  	float cAngleO = asin(cNAo);
  	float oAngleI = asin(oNAi);
  	float oAngleO = asin(oNAo);
  
  	//implement a reflection-mode system if necessary
  	if(opticsMode == ReflectionOpticsType){
  		
  		//set the condenser to match the objective
  		cAngleI = oAngleI;
  		cAngleO = oAngleO;
  
  		//invert the objective
  		oAngleO = pi - cAngleI;
  		oAngleI = pi - cAngleO;
  	}
  
  	//compute Nl (maximum order of the spectrum)
  	//****************************************************************************
  	float maxNu = EtaK.back().nu;
  	float maxLambda = 10000.0f/maxNu;
  	float k = 2*pi/maxLambda;
  	int Nl = ceil( k + 4 * exp(log(k*radius)/3) + 3 );
  	int nLambda = EtaK.size();
  
  	//compute alpha (condenser integral)
  	//****************************************************************************
  	//compute the Legendre polynomials for the condenser aperature
  	float* PcNAo = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PcNAo, cos(cAngleO), Nl+1);
  	float* PcNAi = (float*)malloc(sizeof(float)*(Nl+1));
  	Legendre(PcNAi, cos(cAngleI), Nl+1);
  
  	//allocate space for the alpha array
  	float* alpha = (float*)malloc(sizeof(float)*(Nl + 1));
  	computeCondenserAlpha(alpha, Nl, cAngleI, cAngleO);
  	
  	for(int l=0; l<Nl; l++)
  	{
  		//integration term
  		if(l == 0)
  			alpha[l] = -PcNAo[l+1] + PcNAo[0] + PcNAi[l+1] - PcNAi[0];
  		else
  			alpha[l] = -PcNAo[l+1] + PcNAo[l-1] + PcNAi[l+1] - PcNAi[l-1];
  
  		alpha[l] *= 2 * pi;
  	}
  
  	//compute the information based on wavelength and sphere
  
  	//evaluate the incident field intensity
  	float I0 = 0.0;
  	float theta;
  	float dTheta = (oAngleO - oAngleI)/numSamples;
  	complex<float> Ui;
  
  	Ui = integrateUi(cAngleI, cAngleO, oAngleI, oAngleO, 2*pi);
  	I0 = Ui.real()*2*pi;
  
  	float I;
  	SpecPair temp;
  	float nu;
  	complex<float> eta;
  	complex<float> Us, U;
  	
  	
  
  	float vecLen = 0.0;
  	for(int i=0; i<EtaK.size(); i++)
  	{
  		//compute information based on wavelength and material
  		nu = EtaK[i].nu;
  		lambda = 10000.0f/nu;
  		if(applyMaterial)
  			eta = complex<float>(EtaN[i].A, EtaK[i].A);
  		else
  			eta = complex<float>(baseIR, 0.0);
  
  		//allocate memory for the scattering coefficients
  		complex<float>* B = (complex<float>*)malloc(sizeof(complex<float>)*Nl);		
  		
  		complex<double> IR(eta.real(), eta.imag());
  		computeB(B, radius, IR, lambda, Nl);
  
  
  		//integrate the scattered field at the detector position
  		I = 0.0;
  		
  		for(int iTheta = 0; iTheta < numSamples; iTheta++)
  		{
  			theta = oAngleI + iTheta * dTheta;
  			Us = sampleUs(B, alpha, Nl, radius, cAngleI, cAngleO, theta, 2*pi);
  			
  
  			//calculate the intensity and add
  			if(theta >= cAngleI && theta <= cAngleO)
  				U = Us + 2*(float)pi;
  			else
  				U = Us;
  
  			I += (U.real() * U.real() + U.imag() * U.imag()) * sin(theta) * 2 * pi * dTheta;
  			
  		}
  		
  		temp.nu = nu;
  
  		if(i == 0)
  			printf("I: %f        I0: %f\n", I, I0);
  
  		//set the spectrum value based on the current display type
  		if(dispSimType == AbsorbanceSpecType)
  			temp.A = -log10(I/I0);
  		else
  			temp.A = I;
  
  		if(dispNormalize)
  			vecLen += temp.A * temp.A;
  		//temp.A = Us.real();
  		SimSpectrum.push_back(temp);	
  
  		free(B);
  	}
  	vecLen = sqrt(vecLen);
  
  	if(dispNormalize)
  		for(int i=0; i<SimSpectrum.size(); i++)
  			SimSpectrum[i].A = (SimSpectrum[i].A / vecLen) * dispNormFactor;
  
  	free(alpha);
  
  	PD.EndTimer(SIMULATE_SPECTRUM);
  }*/
  
  void updateSpectrum(float* I, float I0, int n)
  {
  	SimSpectrum.clear();
  	SpecPair temp;
  
  	//update the displayed spectrum based on the computed intensity I
  	for(int i=0; i<n; i++)
  	{
  		temp.nu = EtaK[i].nu;
  
  		//set the spectrum value based on the current display type
  		if(dispSimType == AbsorbanceSpecType)
  			temp.A = -log10(I[i]/I0);
  		else
  			temp.A = I[i];
  
  		SimSpectrum.push_back(temp);
  	}
  }
  
  void computeCassegrainAngles(float& cAngleI, float& cAngleO, float& oAngleI, float& oAngleO)
  {
  	//compute the angles based on NA
  	cAngleI = asin(cNAi);
  	cAngleO = asin(cNAo);
  	oAngleI = asin(oNAi);
  	oAngleO = asin(oNAo);
  
  	//implement a reflection-mode system if necessary
  	if(opticsMode == ReflectionOpticsType){
  		
  		//set the condenser to match the objective
  		cAngleI = oAngleI;
  		cAngleO = oAngleO;
  
  		//invert the objective
  		oAngleO = pi - cAngleI;
  		oAngleI = pi - cAngleO;
  	}
  
  
  }
  
  int computeNl()
  {
  	float maxNu = EtaK.back().nu;
  	float maxLambda = 10000.0f/maxNu;
  	float k = 2*pi/maxLambda;
  	int Nl = ceil( k + 4 * exp(log(k*radius)/3) + 3 );
  
  	return Nl;
  }
  
  void computeBArray(complex<float>* B, int Nl, int nLambda)
  {
  	float nu;
  	complex<float> eta;
  	float* Lambda = (float*)malloc(sizeof(float) * nLambda);
  
  	//for each wavenumber nu
  	for(int i=0; i<EtaK.size(); i++)
  	{
  		//compute information based on wavelength and material
  		nu = EtaK[i].nu;
  		Lambda[i] = 10000.0f/nu;
  		if(applyMaterial)
  			eta = complex<float>(EtaN[i].A, EtaK[i].A);
  		else
  			eta = complex<float>(baseIR, 0.0);
  
  		//allocate memory for the scattering coefficients
  		//complex<float>* B = (complex<float>*)malloc(sizeof(complex<float>)*Nl);		
  
  		complex<double> IR(eta.real(), eta.imag());
  		computeB(&B[i * Nl], radius, IR, Lambda[i], Nl);
  	}
  }
  
  void computeOpticalParameters(float& cAngleI, float& cAngleO, float& oAngleI, float& oAngleO, float& I0, float* alpha, int Nl)
  {
  	computeCassegrainAngles(cAngleI, cAngleO, oAngleI, oAngleO);	
  
  	//evaluate the incident field intensity
  	I0 = 0.0;
  	float theta;
  	complex<float> Ui;
  
  	Ui = integrateUi(cAngleI, cAngleO, oAngleI, oAngleO, 2*pi);
  	I0 = Ui.real()*2*pi;
  
  	//compute alpha (condenser integral)
  	computeCondenserAlpha(alpha, Nl, cAngleI, cAngleO);
  }
  
  void gpuDetectorSpectrum(int numSamples)
  {
  	//integrate across the objective aperature and calculate the resulting intensity on a detector
  	PD.StartTimer(SIMULATE_SPECTRUM);
  	//clear the previous spectrum
  	SimSpectrum.clear();	
  
  	//compute Nl (maximum order of the spectrum)
  	int Nl = computeNl();
  
  	float* alpha = (float*)malloc(sizeof(float)*(Nl + 1));
  	float cAngleI, cAngleO, oAngleI, oAngleO, I0;
  	computeOpticalParameters(cAngleI, cAngleO, oAngleI, oAngleO, I0, alpha, Nl);
  
  	//allocate space for a list of wavelengths
  	int nLambda = EtaK.size();
  	
  	//allocate space for the 2D array (Nl x nu) of scattering coefficients
  	complex<float>* B = (complex<float>*)malloc(sizeof(complex<float>) * Nl * nLambda);
  	computeBArray(B, Nl, nLambda);
  	
  
  	//allocate temporary space for the spectrum
  	float* I = (float*)malloc(sizeof(float) * EtaK.size());
  
  	//compute the spectrum on the GPU
  	PD.StartTimer(SIMULATE_GPU);
  	cudaComputeSpectrum(I, (float*)B, alpha, Nl, nLambda, oAngleI, oAngleO, cAngleI, cAngleO, numSamples);
  	PD.EndTimer(SIMULATE_GPU);
  
  	updateSpectrum(I, I0, nLambda);
  
  	PD.EndTimer(SIMULATE_SPECTRUM);
  
  }
  
  void SimulateSpectrum()
  {
  	if(pointDetector)
  		pointSpectrum();
  	else
  		gpuDetectorSpectrum(objectiveSamples);
  		//detectorSpectrum(objectiveSamples);
  }
  
  float absorbanceDistortion(){
  
  	//compute the mean of the spectrum
  	float sumSim = 0.0;
  	for(int i=0; i<SimSpectrum.size(); i++)
  	{
  		sumSim += SimSpectrum[i].A;
  	}
  	float meanSim = sumSim/SimSpectrum.size();
  
  	//compute the distortion (MSE from the mean)
  	float sumSE = 0.0;
  	for(int i=0; i<SimSpectrum.size(); i++)
  	{
  		sumSE += pow(SimSpectrum[i].A - meanSim, 2);
  	}
  	float MSE = sumSE / SimSpectrum.size();
  
  	return MSE;
  }
  
  float intensityDistortion(){
  
  	//compute the magnitude of the spectrum
  	float sumSim = 0.0;
  	for(int i=0; i<SimSpectrum.size(); i++)
  	{
  		sumSim += SimSpectrum[i].A * SimSpectrum[i].A;
  	}
  	float magSim = sqrt(sumSim);
  
  	//compute the distortion (MSE from the mean)
  	float sumSE = 0.0;
  	for(int i=0; i<SimSpectrum.size(); i++)
  	{
  		sumSE += (SimSpectrum[i].A/magSim) * (1.0/SimSpectrum.size());
  	}
  	float MSE = sumSE;
  
  	return MSE;
  }
  
  void MinimizeDistortion(){
  	ofstream outFile("distortion.txt");
  
  	//set the parameters for the distortion simulation
  	float step = 0.001;
  
  	oNAi = 0.2;
  	oNAo = 0.5;
  
  	//compute the optical parameters
  	//compute Nl (maximum order of the spectrum)
  	int Nl = computeNl();
  
  	float* alpha = (float*)malloc(sizeof(float)*(Nl + 1));
  	float cAngleI, cAngleO, oAngleI, oAngleO, I0;
  	
  	//allocate space for a list of wavelengths
  	int nLambda = EtaK.size();
  
  	//allocate temporary space for the spectrum
  	float* I = (float*)malloc(sizeof(float) * EtaK.size());
  
  	//calculate the material parameters
  	//allocate space for the 2D array (Nl x nu) of scattering coefficients
  	complex<float>* B = (complex<float>*)malloc(sizeof(complex<float>) * Nl * nLambda);
  	computeBArray(B, Nl, nLambda);
  
  
  
  	float D;
  	float e = 0.001;
  	for(float i=0.0; i<=oNAo-step; i+=step)
  	{
  		
  		for(float o=oNAi+step; o<=1.0; o+=step)
  		{
  			
  			
  			//set the current optical parameters
  			cNAi = i;
  			cNAo = o;
  
  			//compute the optical parameters
  			computeOpticalParameters(cAngleI, cAngleO, oAngleI, oAngleO, I0, alpha, Nl);
  
  			//simulate the spectrum
  			cudaComputeSpectrum(I, (float*)B, alpha, Nl, nLambda, oAngleI, oAngleO, cAngleI, cAngleO, objectiveSamples);
  			updateSpectrum(I, I0, nLambda);
  
  			if(dispSimType == AbsorbanceSpecType)
  			{
  				if(i + e >= o || i + e >= oNAo || oNAi + e >= o || oNAi + e >= oNAo)
  					D = 0.0;
  				else
  					D = absorbanceDistortion();
  			}
  			else
  			{
  				if(i >= o || oNAi >= oNAo)
  					D=0;
  				else
  					D = intensityDistortion();
  			}
  			outFile<<D<<"       ";
  		}
  		outFile<<endl;
  		cout<<i<<endl;
  	}
  	outFile.close();
  }