1. A wide-angle image pickup unit, comprising a predetermined number of cameras to take digital images, wherein said predetermined number of cameras are arranged such that optical axes of said predetermined number of cameras cross each other on a same plane at one crossing point and said optical axes of said predetermined number of cameras are provided in radial direction at a predetermined angular interval so that total circumferential images with said crossing point as a center are acquired, wherein a field angle of each camera of said predetermined number of cameras is equal in size and is of a size such that end portions of field angles of adjacent cameras of said predetermined number of cameras are superimposed on each other and form overlapping portions, wherein end portions of adjacent overlapping portions are further superimposed on each other, and an angle formed by said optical axes of said adjacent cameras is 360° divided by said predetermined number of cameras, and the size is such that said overlapping portions are formed over a total circumference, wherein a total circumferential image is obtained using only said overlapping portions formed by said predetermined number of cameras and stereoscopic measurement is performed in an arbitrary direction and at an arbitrary position based on two images of said overlapping portion, and wherein said wide-angle image pickup unit further comprises a displacement amount measuring means and a calculation processing unit, wherein said calculation processing unit performs measurement of three-dimensional coordinates by said stereoscopic measurement in case an object to be measured is at a short distance and is present on said overlapping portion, and said calculation processing unit acquires three-dimensional coordinates of an object to be measured according to images taken from two different points and according to a distance between said two points obtained by said displacement amount measuring means in case an object to be measured is at a long distance.