To overcome the impacts of nonparallelism of 3d rotation and laser speckle on the accuracy of measurement, modification is made by slope fitting of the laser blade.

The undersigned did deem that if the non-parallelism of the crank pin exceeds permissible limitation, crank pin and bearing were caused to be burnt.

The entire system error is mainly caused by the length error and time error and light-beams non-parallelism.