Multi-angle Scheimpflug projection 3D microscope: Design, calibration, and three-dimensional reconstruction

[Display omitted] •A new 3D microscope is designed by combining telecentric imaging and multi-angle Scheimpflug projection.•The improved and practical joint calibration method realizes high-accuracy system calibration.•The point-cloud registration error correction model achieves complete and high-precision microscopic 3D measurement.•A simple and effective approach is provided for 3D measurement of complex micro-structures. 3D measurement of complex micro-structures has becoming increasingly important for precision manufacturing. In this paper, a multi-angle Scheimpflug projection 3D microscope (MASP-3DM) is proposed, and the detailed design procedure is given. The system deployed four Scheimpflug projections and one telecentric imaging to overcome the shortcomings of limited depth of field (DOF), occlusion and reflection. Then, an improved and practical system calibration method is proposed, which utilizes pinhole projection model to calibrate the telecentric imaging. Meanwhile, local homography is combined with perspective-n-point (PnP) strategy to improve the calibration accuracy. Further, a point-cloud registration error correction model is established to achieve complete and high-precision measurement. The experimental results indicate that the re-projection error is within ±0.5μm and the registration error is less than 2μm for system calibration, the maximum of mean deviation, measurement bias, standard deviation, and type A uncertainty are respectively less than 3μm, 7μm, 4μm, and 1μm for 3D measurement, within the 10(H)mm×50(W)mm×40(D)mm volume.