Patent ID: 7827003

Claim:
A straightness measuring method comprising: measuring distances from three displacement meters, which are arranged in a first direction and fixed in relative positions therebetween, to three measuring points arranged along a measurement line that extends in the first direction on a surface of an object to be measured while the three displacement meters are opposed to the object to be measured while moving a movable body relative to a stationary body in the first direction, the moving body being either the three displacement meters or the object to be measured and the stationary body being the other one; determining candidate solutions defined by two profiles among a surface profile along the measurement line, a profile of a locus curve which is the locus of a reference point fixed to the movable body, and a profile of a pitching component accompanied with the movement of the movable body; and extracting one candidate solution with highest fitness from the candidate solutions by applying a genetic algorithm to the candidate solutions using a fitness function defined on the basis of the other profile, among the surface profile, the profile of the locus curve, and the profile of the pitching component, which does not define the candidate solutions.