[Problem] It has been impossible to precisely estimate a local optical properties change site of an object interior. [Solution] An object observation device equipped with: a light intensity information acquisition unit for acquiring light intensity information received by light-receiving probes when light of one light intensity is emitted at an object from light-transmitting probes of a near-infrared light measurement device a light intensity change information acquisition unit for acquiring light intensity change information pertaining to a change in light intensity for respective probe sets from reference light intensity information and the light intensity information an estimation unit for using the light intensity change information to acquire three-dimensional optical property change site information pertaining to a position of a change in absorbance in the interior of the object and an output unit for outputting the optical property change site information wherein the estimation unit is equipped with a correcting means for using sensitivity information to make corrections in accordance with an attenuation of sensitivity due to depth, and a sparsity applying means for introducing sparsity raising the spatial resolution and for acquiring the optical property change site information. This makes it possible to precisely estimate the local optical property change site of the object interior as three-dimensional information.Il était jusquà présent impossible destimer précisément un site de changement des propriétés optiques locales de lintérieur dun objet. Linvention concerne un dispositif dobservation dobjet comprenant : une unité dacquisition dinformations sur lintensité lumineuse pour acquérir une information sur lintensité lumineuse reçue par des sondes recevant de la lumière lorsque de la lumière à une intensité lumineuse est émise au niveau dun objet par des sondes transmettant la lumière dun dispositif de mesure de lumière infrarouge proche une unité dacquis
