Photoacoustic information acquiring apparatus and processing method

Provided is an object information acquiring apparatus having: a receiving unit receiving an acoustic wave generated from an object, which has been irradiated with light, at a plurality of receiving positions and outputting time-series receiving signals; and a processing unit acquiring characteristic information by back-projecting the receiving signals, and the processing unit includes: a unit acquiring, for each receiving position, a dispersion index of light intensity distribution on a back projection spherical surface; a unit acquiring, for each receiving position, an angle range in the back projection based on the dispersion index; and a unit acquiring the characteristic information by back-projecting the receiving signals in the angle range.