1. An image acquisition apparatus, comprising: a light guide plate; a light source for emitting light into the light guide plate, wherein the light source is disposed at one side of the light guide plate; a pinhole imaging plate disposed to be spaced apart from the light guide plate, wherein the pinhole imaging plate has at least one imaging pinhole; and an image sensor for acquiring an image of an object above the light guide plate, wherein the image sensor is disposed to be spaced apart from the pinhole imaging plate; wherein, vertical distance from a surface of the light guide plate away from the pinhole imaging plate to a center plane of the pinhole imaging plate is defined as object distance h object and the object distance h object satisfies a formula of h object ≥ 2 ⁢ r 2 ⁢ ⁢ tg ⁡ ( α / 2 ) , wherein r represents distance between centers of two adjacent imaging pinholes, and α represents angular field of view of the imaging pinhole, wherein the image acquisition apparatus is configured for: making at least part of light emitted by the light source enter and propagate inside the light guide plate through total internal reflection; establishing multiple scanning regions corresponding to multiple imaging pinholes for the object above the light guide plate, wherein adjacent scanning regions are overlapping with each other; capturing multiple imaging regions corresponding to multiple imaging pinholes by the image sensor as partial images of the object above the light guide plate being scanned in corresponding scanning regions, wherein the partial images do not overlap with each other; and stitching together the partial images in each of the imaging regions to obtain a complete image of the object being scanned.