The operation of a Geiger-mode avalanche photo diode (GM-APD) LIDAR is severely disturbed by background noise, which makes it challenging to rapidly and accurately estimate the target depth. Therefore, we propose an adaptive fading Kalman depth estimation technique based on chi-square hypothesis testing for GM-APD LIDARs. First, by analyzing the consistency of the echo photon distribution between adjacent pixels of the GM-APD, the pixels are fused to rapidly obtain the echo data of the target surface, thereby accelerating the depth estimation process. Second, we design a chi-square hypothesis test condition based on the statistical characteristics of the innovation vector, which can help evaluate whether the fading factor is introduced at the current moment, promote the convergence of the algorithm, and reduce the depth estimation time. Third, we propose a fading memory index weighted method to adaptively adjust the weight of the observed values to accurately estimate the innovation matrix covariance and determine the optimal fading factor. We demonstrate the effectiveness of the proposed algorithm through simulations and experiments. The results show that the proposed algorithm can rapidly and accurately estimate the target depth in the presence of strong background noise.
The technique of tagging lapping and polishing slurries with fluorescent material is a promising subsurface damage (SSD) detection method for detecting SSD of optical component and perceiving its formation. However, currently only CdSe/ZnS QDs, CdSSe/ZnS QDs and Rhodamine 6G (R6G) were used to detect SSD, the feasibility of other types of QDs for SSD detection is not been analyzed in detail. And compared with QDs, R6G have a lower fluorescence intensity and is prone to photobleaching. Therefore, in this paper, we not only investigated the feasibility of various types of QDs for SSD detection theoretically and experimentally, but also used the anti-fluorescence quenching agent to enhance the fluorescence of R6G solution, and further studied the influence of anti-fluorescence quenching agent on the fluorescence of SSD tagged by R6G. It is found that (1) no matter how excitation intensity changes, the InP/ZnS QDs, CuInS2/ZnS QDs, R6G, R6G containing anti-fluorescence quenching agent and C QDs can be used to detect SSD; (2)CdSe/ZnS QDs can be used to detect SSD when the excitation intensity is higher than 33 mW; (3)Si QDs, Perovskite QDs, CdSe QDs, and InP QDs can’t be used to detect SSD; (4) The influence of anti-fluorescence quenching agent on the fluorescence of R6G in SSD is related to excitation intensity. This study lays a foundation for detecting the distribution and depth of SSD and perceiving the formation mechanism of SSD in brittle optical materials.
This paper proposes a CdSe/ZnS quantum dot-based reconstruction technique for fused silica subsurface damage to obtain accurate information on subsurface damage, since the current fused silica subsurface damage reconstruction detection method cannot accurately obtain information on the depth and distribution of subsurface damage and cannot make a more accurate assessment of the quality of fused silica optical elements. The technique uses CdSe/ZnS quantum dots to enhance the fluorescence at the subsurface damage of fused silica, and uses the Marching Cubes (MC) algorithm to realize the 3D reconstruction of subsurface damage of fused silica by analyzing the characteristics of the fluorescence section images of subsurface damage of fused silica acquired by fluorescence confocal microscopy, which solves the problem of incomplete acquisition of subsurface damage information by the 3D reconstruction technique of subsurface damage. The problem of incomplete information acquisition of subsurface damage by subsurface damage 3D reconstruction technique is solved. By comparing the 3D reconstruction results of fluorescence slices with and without the addition of quantum dots, it was verified that the addition of CdSe/ZnS quantum dots could obtain more subsurface damage information and achieve a more accurate assessment of the quality of fused silica elements.
To compensate for disturbances in an aircraft’s forward flight and variations in its attitude and angular velocity in the imaging process of photoelectric imaging system, a method of image motion compensation using a fast steering mirror was put forward. First, the working sequence of the image motion compensation system was designed. The position of the fast steering mirror is established by increasing the oblique wave to allow the fast steering mirror to move at the desired speed and compensate for the image motion speed. Then, a mathematical model of the fast steering mirror was established. A linear extended-state observer is designed to estimate the disturbance in real-time, and disturbance compensation is generated to offset the disturbance. Finally, a step response experiment and a tracking experiment were performed to test the characteristics. The step response curve shows that the system’s stable time is 1.8 ms. The tracking characteristic is determined by a given scan curve. The fast steering mirror can satisfy the requirement for a high-speed and highly precise tracking system. It improves the system’s interference rejection performance and reduces the difficulty of controller design.
KEYWORDS: Mirrors, Kinematics, Line of sight pointing, Precision calibration, Optoelectronics, Imaging systems, Composites, Line of sight stabilization, Systems modeling, Error analysis
To improve the control accuracy of optoelectronic imaging equipment, the factors that affect the accuracy of the optoelectronic axis pointing are analyzed. Following Snell’s law, the kinematic coupling equation of the line-of-sight (LOS) angle based on the fast steering mirror (FSM) is established. The calibration method of the FSM system is designed according to the obtained motion characteristics, and a nonlinear correction method is designed to decouple the LOS equation. For a two-axis fast mirror with a stroke of ±20 mrad, the LOS pointing error is <1 μrad when the incident angle is 45 deg, which equates to an improvement of at least 78.9 times compared with linear correction methods. The nonlinear correction method is verified by practical experiments. The method provides a theoretical basis for generating position instructions and thus enables a precise FSM-based pointing system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.