It is an object of one of the inventions to acquire a radiation image in
which a stripe pattern originating from a scattered ray removing grid is
less apt to interfere with observation. An image acquisition apparatus of
one of the inventions includes a sensor for spatially sampling a radiation
transmission distribution of an object to be imaged at a spatial sampling
interval and acquiring an image of the object, and a scattered ray
removing grid for removing scattered rays from the object, wherein an
interval of elements of the scattered ray removing grid is set such that a
spatial frequency of a stripe pattern, in the image, which originates from
the scattered ray removing grid becomes not greater than 40% of a sampling
frequency that is a reciprocal of the spatial sampling interval.
