CURVE LENGTH MEASURING DEVICE AND MEASURING METHOD THEREFOR AND STORAGE MEDIUM WHICH STORES CONTROL PROGRAM FOR MEASURING LENGTH OF CURVE

A curve length measuring device which processes image data obtained by the photographing of an object to be measured to measure a length of an arbitrary curve on a surface of the object to be measured includes a photographing unit for photographing the object to be measured from two or more different viewpoints to obtain a plurality of image data, a measuring point setting unit for setting, on a photographed image, a measuring point sequence along a curve to be measured, a curved surface calculation unit for setting parabolic half-lines directed from a predetermined reference point at a photographing position of the object to be measured by the photographing unit toward each measuring point sequence set by the measuring point setting unit and interpolating a group of half-lines to obtain a curved surface, an intersection calculation unit for obtaining an intersection between the plurality of said curved surfaces obtained by the curved surface calculation unit, and an intersection length calculation unit for obtaining a length of an intersection obtained by the processing by the intersection calculation unit.