The diffusion equation of the photon transport in a multi-layered medium with mismatched refractive index is analyzed

and the accurate solution of the diffuse equation is set up. The equation is checked by Monte-Carlo simulation. The comparison between the spatially resolved reflectance of mismatched media and Monte-Carlo simulation shows an excellent agreement between our theory and Monte-Carlo simulation. Meanwhile

the effect of the variety of refractive index on spatially resolved reflectance caused by finite size flat beam is discussed. Experimental results show that diffuse result changes with the variety of the refractive index

while the refractive index is changed at the range of 1.35~1.45

and the maximum error is 7%.