An imaging apparatus (100) adjusts the polarization directions of irradiation beams (to a diffraction grating) corresponding to first and second beams (175 1 175 2) respectively which have different polarization directions (for example by adjusting a relative angle formed between light emitting ends of respective polarization maintaining fibers) so that the spectral characteristics of the irradiation beams at the diffraction grating (141) coincide with each other. Then the imaging apparatus acquires a tomographic image indicating polarization information for a object based on beams (that come from the diffraction grating for splitting and diffracting a beam from the adjustment unit) corresponding to the first and second beams respectively which have different polarization directions.
