An OCT technique enabling tomography observation of a portion of an organism difficult to constrain and a tomography observation technique for observation of a constrainable portion while eliminating the burden on the organism without constrain are disclosed. A variable-wavelength light generator (variable-wavelength light source) is used as a light source of a light interference tomograph. The variable-wavelength light generator has a variable range of wave number of 4.7x10<-2> mum<-1> or more and a frequency width of the output light of 13 GHz or less, and includes a means for changing stepwise the wave number at wave number intervals of 3.1x10<-4> mum<-1> or less and at time intervals of 530 mum or less.
VARIABLE-WAVELENGTH LIGHT GENERATOR AND LIGHT INTERFERENCE TOMOGRAPH