Image-type displacement measurement resolution improvement without magnification imaging

Abstract

The imaging-type displacement measurement (IDM) technique is better-suited to high-resolution measurement than the traditional moiré fringe technique. In Angular displacement measurement, IDM generally requires lens-magnified imaging processes to reach the proper resolution, which depends on overly large imaging lenses and highly complex, generally unreliable equipment, making the technique not conducive to industrial application. The resolution of an IDM device was improved in this study without the use of an imaging lens. The lensless imaging principle was established, then a new algorithm based on multi-line fusion and denoising was developed to improve the displacement subdivision resolution. The proposed algorithm was verified by both simulation and experimentation. The simulation shows that the proposed algorithm effectively reduces positioning operation noise. In the experiment, an angular measurement resolution of 0.039″ (25-bit) was achieved on a 70 mm diameter circular grating. The proposed method lays a foundation for further high-resolution displacement measurement techniques.