Least-Square-Method-Based Optimal Laser Spots Acquisition and Position in Cooperative Target Measurement

• Main Authors: Chen, W. (Author), Du, Y. (Author), Hu, Y. (Author), Lan, C. (Author), Li, K. (Author), Yuan, F. (Author)
• Format: Article
• Language: English
• Published: MDPI 2022
• Subjects: cooperative target; Cooperative targets; Data handling; diode supply current; Diode supply current; Diodes; Equations of state; exposure time; Exposure-time; Focal-spot; Image coordinates system; Laser spots; laser-projected spot; Laser-projected spot; least square method; Least squares approximations; Least-squares- methods; Nonlinear equations; Spot position; Supply currents
• Online Access: View Fulltext in Publisher

 The relative positioning precisions of coordinate points is an important indicator that affects the final accuracy in the visual measurement system of space cooperative targets. Many factors, such as measurement methods, environmental conditions, data processing principles and equipment parameters, are supposed to influence the cooperative target’s acquisition and determine the precision of the cooperative target’s position in a ground simulation experiment with laser projected spots on parallel screens. To overcome the precision insufficiencies of cooperative target measurement, the factors of the laser diode supply current and charge couple device (CCD) camera exposure time are studied in this article. On the hypothesis of the optimal experimental conditions, the state equations under the image coordinates’ system that describe the laser spot position’s variation are established. The novel optimizing method is proposed by taking laser spot position as state variables, diode supply current and exposure time as controllable variables, calculating the optimal controllable variables through intersecting the focal spot centroid line and the 3-D surface, and avoiding the inconvenience of solving nonlinear equations. The experiment based on the new algorithm shows that the optimal solution can guarantee the focal spot’s variation range in 5–10 pixels under image coordinates’ system equivalent to the space with a 3 m distance and 0.6–1.2 mm positioning accuracy. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.