CN114757987A

CN114757987A - Method for extracting centroids of multiple sub light spots based on edge detection and target tracking

Info

Publication number: CN114757987A
Application number: CN202210385803.8A
Authority: CN
Inventors: 金睿焱; 王帅; 高泽宇; 杨平
Original assignee: Institute of Optics and Electronics of CAS
Current assignee: Institute of Optics and Electronics of CAS
Priority date: 2022-04-13
Filing date: 2022-04-13
Publication date: 2022-07-15

Abstract

The invention discloses a method for extracting the mass centers of a plurality of sub light spots based on edge detection and target tracking, which can provide a more advanced technical means for wavefront detection and correction under the conditions of wide view field and multiple targets. The existing multi-view wavefront detection is mainly realized by simply adopting a method of a plurality of sensors and stacking hardware quantity, and no theoretical breakthrough is made from a wavefront reconstruction method, so that the system complexity is increased linearly. In order to solve the problem, the invention realizes the centroid detection of the multi-target light spots by using an edge detection and target tracking algorithm and introducing a detection mechanism of multi-target multi-sight beam common diffraction imaging, and is expected to promote the essential breakthrough of the Hartmann-shack wavefront sensing technology in measuring the dimension from a point source to a surface field.

Description

Method for extracting centroids of multiple sub light spots based on edge detection and target tracking

Technical Field

The invention belongs to the technical field of wavefront sensing, and particularly relates to a method for extracting the mass centers of a plurality of sub light spots based on edge detection and target tracking.

Background

A shack-hartmann wavefront sensor (HS) consists of a microlens array and a CCD. The micro-lens array divides the incident light beam to be measured by sub-aperture and converges on the photoelectric detector to form a light spot array image. After the image is collected by a photoelectric detector arranged on a focal plane of the micro lens, the spatial distribution of the wavefront distortion to be measured in the full aperture can be reconstructed by calculating the centroid position offset data (equivalent to the wavefront slope in each sub aperture) of each sub light spot.

In recent years, new requirements for the development of HS are being raised by increasingly expanding application fields and application scenarios. From the detection objects, the detection objects of the HS wavefront sensor are not limited to traditional single-point source targets, but are further expanded to wide-field-of-view and multi-target scenes. At present, the wave front extraction technology for the extended target has been obviously developed. In 1988, J.M. Beckers proposed the concept of multilayer conjugate technology (MACO), which uses multiple beacon illuminations in different line-of-sight directions for atmospheric aberration multi-line-of-sight wavefront detection, providing the basis for adaptive optical correction in a Large field of view (see reference [1] J.M. Beckers.incorporating the size of the anisotropic patch with multiple conjugate adaptive optics, Proc. European Southern Observativity Conference and work hop on Very Large lenses and Heat Instrument analysis 30:693-703 (1988)); the German institute of Sun physics (KIS) pioneers the MCAO technical verification test in 2002, obtains the reconstruction of two layers of atmospheric wavefronts and the correction field of 35' by double-layer conjugation, and enlarges the correction field by three times compared with the original system; a multilayer conjugate technology optical test system developed by an astronomical table in southern Europe utilizes atmospheric wavefront information of three bright directors to realize high-resolution observation of a 2' field of view in 2007; in addition to the MCAO technique mentioned above, theoretical studies around wide-field Adaptive optics have recently evolved Multi-beacon Adaptive optics (see reference [2] Visor shmanium, Natales Iaitsky, Multi-beacon Adaptive optics and field-of-viewing evaluating protocol, Proc. SPIE 4338:97-106 (2000)), Multi-object Adaptive optics (MOAO) technique (see reference [3] R.G.Dekany, M.C.Britton, D.T.vel, B.L.L.legacy, G.Herriot, C.E.Max, and J.P.Verny, Adaptation optics preferences decision, F.890, III.54IE, Proc. SPC. 8790).

However, the traditional wavefront extraction technologies for wide view field and multi-target scenes do not make a breakthrough on the wavefront reconstruction principle technology, multi-target detection is realized mainly by a hardware mode of increasing the number of sensors, and the traditional weighted centroid extraction algorithm is still relied on, so that the requirements of wide view field astronomical observation on multi-beacon wavefront detection and the requirements of laser atmospheric transmission on multi-target real-time detection are difficult to meet. Aiming at the problem, the invention provides a method for extracting the centroids of a plurality of sub light spots in a single sub aperture based on edge detection and target tracking. The invention is different from a measurement mechanism that only a single-target single-sight wave front distortion is extracted by a traditional weighted centroid extraction algorithm, and can extract the centroids of a plurality of sub light spots at one time, so that the wave front extraction of a wide field of view and a multi-target scene can be completed by only using a single sensor, and the extension of the wave front measurement dimension from a point (single sight) to a surface (multi sight) of HS is promoted. The method is essentially different from the existing multi-sensor scheme at home and abroad or the strategy based on the prior array position, and is a novel method.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: as shown in fig. 1, light beams of a plurality of targets (O1, O2, O3) are transmitted through the atmosphere and enter the wide-field hartmann-shack wavefront sensor through an optical matching system (L1, L2). The same micro-lens array in the multi-target light beam sharing sensor is imaged on the CCD detector to form a multi-spot array overlapped image, and a plurality of sub-spots corresponding to the multiple targets exist in a single sub-aperture in the overlapped image. The traditional weighted centroid extraction algorithm can only detect a single-point source target, and the requirements of the multi-target scene are difficult to meet. The invention provides a multi-spot array centroid real-time extraction algorithm for a multi-target scene, which can complete extraction, separation and reconstruction of mutually coupled multi-sight wave front information and realize real-time wave front reconstruction of a double target and a three target at one time.

The technical scheme adopted by the invention for solving the technical problem is as follows: and (4) segmenting all sub-light spots by adopting an edge extraction algorithm so as to extract the mass center of each sub-light spot. Subsequently, a domain search based algorithm is used to automatically match the different sub-spots with the respective sub-apertures into a multi-array.

The concrete implementation steps are as follows:

step 1, aiming at the mass center of a multi-sight light spot array, realizing automatic mass center extraction of a plurality of sub light spots based on an edge extraction algorithm;

step 1.1, firstly, each sub-light spot in the whole HS light spot array chart is subjected to preliminary centroid extraction. And (4) segmenting the spot area in the whole image by using a Canny edge extraction algorithm and calculating the centroid of the spot.

Step 1.2, filling the inside of the light spot edge to segment an independent and complete light spot area because the Canny edge detection algorithm can only detect the edge of the light spot, namely the outline of the light spot area;

and step 1.3, further screening the segmented light spot region based on morphological characteristics so as to reduce the centroid extraction error.

Step 2, after obtaining the sub-light spot mass center, establishing a corresponding relation between the light spot mass center and the multi-array sub-aperture by using a neighborhood search matching algorithm;

Step 2.1: selecting any one of the sub-light spots as a first calibration light spot to serve as an initial point of iterative search, and then establishing a neighborhood search window which can be reduced and amplified according to actual conditions at the light spot centroid coordinate to search for the light spot centroid with the nearest distance so as to establish a corresponding relation with the calibration light spot, thereby completing matching;

step 2.2: and repeating the steps by taking the matched spot centroid as a new reference until all spots are matched.

The method is characterized in that the limitation of extraction quantity of the sub-aperture centroids in the traditional weighted centroid algorithm is broken through, and the centroids of all light spots are obtained from the whole light spot array diagram. Compared with the prior art, the invention has the following advantages: different from a traditional measurement mechanism that only single-target single-sight-line wavefront distortion can be extracted by a weighted centroid extraction method, the method can realize the centroid extraction of multiple targets and multiple sub light spots at one time based on a single Hartmann sensor, and is essentially different from the existing MCAO technology at home and abroad. In comparison, the multi-wavefront reconstruction capability is skillfully obtained through algorithm innovation under the condition that the existing structure of the classical HS wavefront sensor is not changed through algorithm innovation by the MCAO, and the MCAO has great advantages in the aspects of cost, efficiency and economy.

Drawings

FIG. 1 is a schematic diagram of multiple targets forming a multiple spot array overlay image on a Hartmann sensor according to the present invention;

FIG. 2 is a schematic diagram of the contour of the light spot detected by the edge detection operator according to the present invention;

FIG. 3 is a schematic diagram of the automatic matching of different sub-spots into a multi-array according to the present invention;

fig. 4 is a flowchart of a method for extracting the centroids of a plurality of sub-light spots in a single sub-aperture based on edge detection and target tracking according to the present invention.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

As shown in fig. 2 and 4, in this embodiment, the HS spot array map is derived from a 12 × 12 HS front sensor, with 116 effective sub-apertures, a reference beam wavelength of 532nm, and an image signal-to-noise ratio of about 12. The specific implementation method comprises the following steps:

a preliminary centroid extraction is first performed for each of the 116 sub-apertures. And (3) segmenting the light spots in the whole image by using an edge extraction algorithm and filling the interior of the intercepted light spot edges so as to ensure the integrity of segmentation. Because the intensity of partial areas of the light beam is insufficient due to noise and atmospheric disturbance in an actual scene, errors may exist in the light spot segmentation, and therefore the result of the preliminary segmentation is further screened based on morphological features so as to reduce the centroid extraction errors, and the centroids are calculated from the independent light spot areas.

After the sub-spot mass center is obtained, the corresponding relation between the spot mass center and each sub-aperture is established on the basis of a neighborhood search matching algorithm. Firstly, selecting any one of a plurality of sub light spots as a first calibration light spot as an initial point of iterative search, then establishing a neighborhood search window which can be reduced and enlarged according to actual conditions at the position of the light spot centroid coordinate to search for the light spot centroid with the nearest distance so as to establish a corresponding relation with the calibration light spot, completing matching, and then taking the matched light spot centroid as a new reference, repeating the steps until the matching of all the light spots is completed

Those matters not described in detail in the present specification are well known in the art to which the skilled person pertains.

Claims

1. A method for extracting the centroids of a plurality of sub light spots based on edge detection and target tracking is characterized by comprising the following steps: based on a single Hartmann-shack wavefront sensor (HS), the method can realize multi-sight-line wavefront reconstruction and is realized by the following steps:

step 1: aiming at the multi-sight light spot array centroid, automatic centroid extraction of a plurality of sub light spots is realized based on an edge detection algorithm;

and 2, step: after the sub-spot centroid is obtained, the corresponding relation between the spot centroid and the multi-array sub-aperture is established on the basis of a neighborhood search target tracking algorithm.

2. The method for extracting the centroids of the plurality of sub-light spots based on the edge detection and the target tracking as claimed in claim 1, wherein:

3. The method for establishing the corresponding relation between the spot centroid and the multi-array neutron aperture based on the neighborhood search target tracking algorithm according to claim 2, wherein: