Method to apply photo-stimulation, photo-dynamic therapy and/or ablation laser treatment to biological tissue including directing radiation from at least one radiation energy source for supplying a treatment radiation； adjusting a collimator assembly for directing radiation from the at least one radiation energy source to the treatment site； collecting radiation not absorbed at the treatment site and reflecting the radiation back to the treatment site, while a contact surface of the collector is engaged with the surface of the biomass； maintaining a set distance between the adjustable collimator assembly and the contact surface； and moving a lens relative to an outlet aperture of the adjustable collimator assembly when the collector is adjusted to thereby produce a given spot size, shape or energy density of the treatment radiation emitted from the adjustable head assembly.
