Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Jul 7;22(14):5110.
doi: 10.3390/s22145110.

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

Kai Li  1 , Feng Yuan  1 , Yinghui Hu  1 , Yongbin Du  1 , Wei Chen  2 , Chunyun Lan  2
Affiliations

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

Kai Li et al. Sensors (Basel). .

Abstract

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.

Keywords: cooperative target; diode supply current; exposure time; laser-projected spot; least square method.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic of space cooperative target measurement based on projected laser.
Figure 2
Figure 2
The gray level picture of a projected spot.
Figure 3
Figure 3
Light intensity distribution.
Figure 4
Figure 4
The diagram of a monocular camera under three coordinate systems.
Figure 5
Figure 5
LED current vs. luminous flux.
Figure 6
Figure 6
Data processing and optimizing flowchart.
Figure 7
Figure 7
Laser spot images with different supply current (t = 500 ms). (a) Supply current = 0.12 A; (b) Supply current = 0.18 A; (c) Supply current = 0.35 A; (d) Supply current = 0.63 A.
Figure 8
Figure 8
Laser spot images with a different exposure time. (i = 0.86 A) (a) Exposure time = 600 ms; (b) Exposure time = 1000 ms; (c) Exposure time = 1500 ms; (d) Exposure time = 2000 ms.
Figure 8
Figure 8
Laser spot images with a different exposure time. (i = 0.86 A) (a) Exposure time = 600 ms; (b) Exposure time = 1000 ms; (c) Exposure time = 1500 ms; (d) Exposure time = 2000 ms.
Figure 9
Figure 9
Distribution of laser spot centroid position. (a) Variation of supply current (t = 500 ms); (b) Variation of exposure time (i = 0.86 A).
Figure 10
Figure 10
The optimal controllable variables selection of different lasers. (a) Laser spot 1 (supply current); (b) Laser spot 1 (exposure time); (c) Laser spot 2 (supply current); (d) Laser spot 2 (exposure time); (e) Laser spot 3 (supply current); (f) Laser spot 3 (exposure time).
Figure 11
Figure 11
The schematic of target disc with three green LEDs.
Figure 12
Figure 12
The on-site photos of the experimental platform.
Figure 13
Figure 13
Calibration results and position error distribution. (a) Optimized results; (b) Optimized position error distribution; (c) Unoptimized results; (d) Unoptimized position error distribution.
Figure 13
Figure 13
Calibration results and position error distribution. (a) Optimized results; (b) Optimized position error distribution; (c) Unoptimized results; (d) Unoptimized position error distribution.
Figure 14
Figure 14
Comparative simulation results (a) Optimized simulation curves; (b) Unoptimized simulation curves.
See this image and copyright information in PMC

References

    1. Barnes R.A., Brown S.W., Lykke K.R., Guenther B., Xiong X., Butler J.J. Comparison of Two Methodologies for Calibrating Satellite Instruments in the Visible and Near-Infrared. Appl. Opt. 2015;54:10376–10395. doi: 10.1364/AO.54.010376. - DOI - PMC - PubMed
    1. Qi N., Xia Q., Guo Y., Chen J., Ma Z. Pose Measurement Model of Space Cooperative Target Capture based on Zoom Vision System. Adv. Mech. Eng. 2016;8:1687814016655954. doi: 10.1177/1687814016655954. - DOI
    1. Huo J., Yang N., Yang M. Tracking and Recognition of Projective Spots for Cooperation Targets in Vehicle Simulation Test. Opt. Precis. Eng. 2015;8:2134–2142. doi: 10.3788/OPE.20152308.2134. - DOI
    1. Wang F., Dong H., Chen Y., Zheng N. An Accurate Non-Cooperative Method for Measuring Textureless Spherical Target Based on Calibrated Lasers. Sensors. 2016;16:2097. doi: 10.3390/s16122097. - DOI - PMC - PubMed
    1. Yang N., Huo J., Yang M. A Method for Attitude Measurement of A Test Vehicle based on the Tracking of Vectors. Meas. Technol. 2015;26:085019. doi: 10.1088/0957-0233/26/8/085019. - DOI

LinkOut - more resources