High-speed target tracking control system based on short-time rotational reflection imaging.

High-speed tracking technology has wide applications in the military and aerospace industry. However, existing approaches, such as camera arrays or Doppler radar systems, suffer from high cost and inconvenience. This paper reports a high-speed target tracking control system based on short-time rotational reflection imaging, specifically aimed at overcoming certain limitations. In the system we designed, a high-speed camera coupled with a rotating reflector is used to achieve reliable high-speed target tracking. This paper first introduces the working principle and mathematical model of the system, then analyzes the key technologies, including motor response delay time and rotational speed curve fitting, and, finally, verifies the feasibility of the system and the correctness of the theory based on a series of experiments. Experimental results demonstrated that our work is efficient and accurate in target tracking and image clarity. The developed system demonstrates significant potential for widespread use across military and aerospace sectors. Furthermore, the insights gained from our investigation into key technologies could act as a reference point for fellow researchers in related scientific areas.

Methods for improving imaging quality of a small-distance high-speed rotational reflection tracking system.

The imaging quality of a rotational reflection high-speed tracking system is greatly affected by the optical characteristics of the reflector and the depth of field limitations of the imaging system, especially for tracking systems working in small distances. In order to improve the imaging quality, this paper focused on two factors that affect the imaging quality: double vision caused by the optical characteristics of reflectors and blurring caused by the depth of field of imaging systems. This paper quantified the impact of these two factors on imaging through theoretical analysis, proposed a method of changing the hardware position, and conducted a simulation and experiments. The results show that the proposed solution in this paper can effectively improve the imaging quality of the system. The content studied in this paper has certain significance in the field of high-speed tracking of rotating reflectors and can provide reference for relevant researchers.

Two-step calibration method of the extrinsic parameters with high accuracy for a bistatic non-orthogonal shafting laser theodolite system.

Motivated by the increasing demands on the precision of 3D large-scale measurement, the extrinsic parameters calibration with high accuracy of the bistatic non-orthogonal shafting laser theodolite (N-theodolite) system is required. A two-step method is proposed to achieve the extrinsic parameters calibration with high accuracy in this paper. In the first step, by analyzing and setting the approximate emitted point during the motion of the laser axis in local space, the calculation of the initial extrinsic parameters can be simplified. In the second step, the above results are taken as the initial values of optimization, and the distances between the spatial laser points provided by PSD sensors with high accuracy in global space are used to construct the unconstrained optimal objective function. The proposed method is validated with the measurement experiment of the bistatic N-theodolite system, the average error of 3D coordinate measurement is less than 0.4 mm, and the average error of distance measurement is less than 0.3 mm within 5 m.

Accurate calibration for crosstalk coefficient based on orthogonal color phase-shifting pattern.

The crosstalk coefficient calibration of de-crosstalk in color fringe projection profilometry is an essential step for the high-accuracy measurement. In this paper, a novel approach for calibrating crosstalk matrix of color camera is proposed. The wrapped phase error model introduced by color crosstalk in orthogonal pattern is established. Compared with the existing calibration methods depending on calculating the modulation of the crosstalk channel, the crosstalk coefficients are obtained from phase error in our method. By projecting the designed color orthogonal phase-shifting fringe patterns onto a white plate, the phase-shifting fringe patterns in both horizontal and vertical directions can be separated from captured images. The coefficients between different channels are calibrated by fitting the error relationship between the wrapped phase containing crosstalk and the standard ones. Coefficient fitting simulations and experimental validations including shape measurement of a white plate and distance measurement of a step block are carried out to verify the effectiveness of the proposed method.

Practical zoom camera calibration method for close-range photogrammetry.

Compared to a conventional fixed focus lens, a zoom lens is more flexible and adaptable. However, the challenges involved in precise calibration for a zoom camera prevent its widespread use in close-range photogrammetry. A practical calibration method for a zoom camera is proposed. The zoom-focus model is established through dimension reduction of the setting variables, which is represented as a set of functions of the zoom setting. The zoom and focus settings are updated in real time for objects at different measurement depths. The calibration process only requires the zoom camera to observe the control points distributed in the designed calibration field with several combinations of zoom and focus settings. All the coefficients of the zoom-focus model can be solved by a nonlinear joint optimization. Experimental results have proved that the proposed method is effective for close-range photogrammetry.

Rapid and flexible calibration of DFPP using a dual-sight fusion target.

The parameter calibration of a digital fringe projection profilometry (DFPP) system is a fundamental step and directly related to 3D measurement accuracy. However, existing solutions based on geometric calibration (GC) suffer from the weakness of limited operability and practicality. In this Letter, a novel, to the best of our knowledge, dual-sight fusion target is designed for flexible calibration. The novelty of this target is the ability to directly characterize control rays for ideal pixels of the projector, and to transform the rays into the camera coordinate system, which replaces the traditional phase-shifting algorithm and avoids the error from the nonlinear response of the system. Attributed to the excellent position resolution of a position-sensitive detector within the target, the geometric relationship between the projector and camera can be easily established by projecting only one diamond pattern. Experimental results demonstrated that the proposed method using only 20 captured images is capable of achieving comparable calibration accuracy to the traditional GC method (20 images versus 1080 images, 0.052 pixels versus 0.047 pixels), which is suitable for rapidly and accurately calibrating the DFPP system in the 3D shape measurement field.

High-performance phase measuring profilometry architecture based on Zynq SoC.

This paper presents a novel high-performance heterogeneous computation architecture, to the best of our knowledge, for stereo structure light using the phase measuring profilometry (PMP) algorithm based on a Zynq UltraScale+ system on chip (SoC). The proposed architecture aims to achieve real-time and high-accuracy 3D shape measurement. The experiment results indicate that the calculation time of a standard four-step PMP algorithm with a resolution of 1280×1024 is 14.11 ms. It is nearly 51 times faster than the well-optimized software implementation running on a Raspberry Pi and nearly three times faster than a high-end PC, with 15 times less power consumption. Consequently, the proposed architecture is deemed suitable for real-time 3D measurements in embedded applications.