3D reconstruction from multiple images is the creation of three-d imensional models from a set of images. It is the reverse process of obtaining 2D images from 3D scenes.
The essence of an image is a projection from a 3D scene onto a 2D plane,during which pr- ocess the depth is lost. The 3D point corresp onding to a specific image point is constrained to be on the line of sight. From a single image, it is impossible to determine which point on this line corresponds to the image point. If two i- mages are available, then the position of a 3D point can be found as the intersection of the two projection rays. This process isre- ferred to as triangulation. The key for this process is the relat- ions between multiple views which convey the information that corr- esponding sets of points must contain some structure and that this structure is related to the poses and the calibration of the camera.

References
[1].Multi-camera scene reconstruction via graph cuts, In ECCV 2002.
[2].Scene Reconstruction and Visualization from Internet Photo Collections,PhD Thesis, 2008.
[3].https://graphics.stanford.edu/~mdfisher/SceneReconstruction.html