A procedure is proposed for deriving the aerosol microphysical characteristics of the spherical particle, the complex refractivity index m = mreal + i*mimage and the bimodal size distribution function U(r), using laser sensing data at the wavelengths within 355-1064 nm. A possibility of different optical set, (3β + 2σ) and (3β + 3σ), is studied for weakly absorbing particles for mimage ≤ 0.010, when mfine ≠ mcoarse holds. The algorithms are tested for one mfine (1.50+i*0.01) and nine mcoarse (mreal= 1.40, 1.50, 1.60; mimage = 0.0001, 0.001, 0.01). In order to include the influence of the contribution from the modal particles into the total concentration, 462 empirical models of U(r) are used.