/* Function to compute the solution to the correct photon counting signal
	for a coherent source.  The solution is found by bisection to within 10^-2.  The signal
	is the variable sig, the dead time is the variable dt.  The corrected signal
	is returned from the variable sol.
*/


float nlexp (float sig, float dt)
{
	int j;
	float x1, x2, dx, xmid;
	float f, fmid, sol;
	
	x1 = sig;
	x2 = 1.5*sig;
	
	f = sig - x1*exp(-dt*x1);
	fmid = sig - x2*exp(-dt*x2);
	sol = f < 0.0 ? (dx = x2 - x1, x1) : (dx = x1 - x2, x2);
	for (j = 1; j <= 40; j++){
		xmid = sol + (dx *= 0.5);
		fmid = sig - xmid*exp(-dt*xmid);
		if (fmid <= 0.0) sol = xmid;
		if (fabs(dx) < 1e-2 || fmid == 0.0) return sol;
	}
}