CN114815133A - An automatic confocal method for an optical multi-aperture imaging system - Google Patents

Abstract

The invention discloses an automatic confocal method of an optical multi-aperture imaging system, which can be used for pre-calibration of the sub-aperture pointing direction of the optical multi-aperture imaging system. The method utilizes a multi-connected region centroid extraction algorithm and a binarization area method to calculate the distances between multiple light spots and a confocal point and the total area of the light spots, constructs an evaluation function according to the distances and the total area, adaptively adjusts the weights of the distances and the areas by combining focal plane information at the current moment and the previous moment, and automatically controls a pointing actuator through an optimization algorithm to realize the automatic coincidence of the focal plane light spots of the multi-aperture system. The method can realize multi-aperture light spot confocal by one key aiming at a complex light spot initial state, does not need time sequence shutter modulation and additional optical elements, and is less limited by aperture arrangement, aperture number, light path structure, system parameters and the like.

Description

An automatic confocal method for an optical multi-aperture imaging system

technical field

The invention belongs to the field of optical multi-aperture imaging, in particular to an automatic confocal method for an optical multi-aperture imaging system.

Background technique

Large-scale optoelectronic telescope systems are widely used in many important fields such as environmental monitoring, astronomical observation, and remote sensing imaging, and are playing an increasingly important role in national security, space research, and human life. The demand for high-quality detection with high noise suppression, high resolution accuracy, and high detection efficiency is increasing day by day. In theory, the larger the telescope aperture, the stronger its light-gathering ability and the higher the resolution. However, with the existing technical process, a single primary mirror cannot achieve the required aperture. Until the 1970s, with the maturity of optical multi-aperture imaging theory and the gradual accumulation of telescope manufacturing technology, optical multi-aperture imaging technology provided new ideas for breaking through the limitation of system aperture.

Optical multi-aperture needs to improve the resolution through confocal and co-phase between each sub-aperture system, otherwise it will not work. During multi-aperture imaging, confocality is a prerequisite. Especially in the initial state, there are obvious pointing differences between the sub-apertures, which causes the images of the sub-apertures to be interlaced with each other, and confocal calibration is required. When the multiple spots are completely separated from each other, although the centroid of the sub-aperture spot can be extracted, it is difficult to identify the correspondence between the spot and the aperture; when the multiple spots overlap, even the centroid of the sub-aperture spot becomes difficult to extract.

Therefore, in engineering, the decoupling of each sub-aperture light spot is often achieved by means of timing shutter modulation or a special spot separation module. James Webb Telescope uses timing shutter modulation to traverse all sub-mirrors through pairwise calibration to achieve confocal primary mirror. The STAR-9 telescope array developed by Lockheed Martin also uses timing shutter modulation to achieve 9-aperture confocality; the three-aperture telescope array developed by the National Astronomical Observatory of the Chinese Academy of Sciences in China divides three sub-aperture light spots through a spot separation module composed of multiple prisms . Timing shutter modulation significantly increases calibration complexity and reduces engineering reliability as the number of apertures increases. The specially designed spot separation module will undoubtedly increase the complexity of the system, and is limited by the arrangement of apertures, the number of apertures, the structure of the optical path, and the system parameters, resulting in poor universality and portability.

SUMMARY OF THE INVENTION

In order to overcome the problems and limitations of the existing methods, the present invention provides an automatic confocal method for an optical multi-aperture imaging system, which does not require a complex spot separation module and tedious timing calibration, and is suitable for optical multi-aperture imaging systems of various structural forms. .

The technical scheme adopted in the present invention is: an automatic confocal method for an optical multi-aperture imaging system. During the confocal process, the point spread function image of the focal plane is collected; the multi-connected area centroid extraction algorithm is used to calculate the distance between the multi-spot and the confocal point, and the The binarized area method calculates the total area of the light spot, and builds an evaluation function based on the distance and area; adaptively adjusts the weight of the distance and area in the evaluation function based on the focal plane information at the current moment and the previous moment; controls the pointing actuator through an optimization algorithm to make the The evaluation function is optimized to realize the automatic confocal of the multi-aperture imaging system.

Among them, the centroid position of the multi-spot area is obtained in real time from the image collected by the detector through the multi-connected area centroid extraction algorithm, and it is not necessary for each sub-aperture spot to be in a separated or incoherent state.

Among them, the evaluation function comprehensively utilizes the distance and area information to avoid the problem of gradient disappearance.

Among them, the evaluation function uses the focal plane information of the current moment and the previous moment at the same time, which reduces the local extreme value in the optimization process.

Among them, the initial state should ensure that all sub-aperture light spots are within the field of view of the detector.

The specific steps are as follows:

Step 1), performing imaging detection on the convergent beam behind the imaging primary mirror of the n-hole telescope array, where n≥2;

Step 2), placing the detector on the optical multi-aperture imaging focal plane, and selecting a point (x0, y0) on the focal plane as the confocal point of the light spot;

Step 3), extract multi-region centroids through the multi-connected region centroid extraction algorithm, the number of centroids m≥n, obtain the centroid positions (x1, y1), ..., (xm, ym), thereby calculating the distance information from the confocal point;

Step 4), obtain the total spot area S by the binarization area method, and Smax is the area when the spot is completely separated and there is no overlapping area;

Step 5), use the distance and area to construct an evaluation function, carry out optimization iteration, drive the high-precision deflection mirror to perform confocal through the servo control module, and at the same time adjust the area in the evaluation function adaptively through the distance and area information of the current moment and the previous moment. With the weight of distance, the automatic confocal closed loop of the n-hole telescope array is finally realized, and the light spot coincides with the confocal point after the loop is closed.

Compared with the prior art, the present invention has the following advantages:

1) The present invention utilizes the focal plane information optimization technology to realize automatic confocal, without additional optical elements and complicated timing shutter calibration, which improves the engineering applicability and reliability of the optical multi-aperture imaging system.

2) The present invention is less restricted by aperture arrangement, aperture number, optical path structure and system parameters, etc., and has strong universality and portability, and can be used for automatic sharing of optical multi-aperture imaging systems of various structural forms. Focus calibration.

Description of drawings

FIG. 1 is a schematic diagram of the centroid extraction effect of the multi-connected region centroid extraction algorithm when the light spots overlap.

FIG. 2 is a schematic diagram of the total area of the light spot obtained by the binarization area method.

FIG. 3 is a schematic diagram of the result of the eight-aperture imaging system using the method of the present invention to realize automatic confocal.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

The present invention is an automatic confocal method for an optical multi-aperture imaging system, which uses a multi-connected area centroid extraction algorithm and a binarized area method to construct an evaluation function, and adaptively adjusts the area and the area in the evaluation function according to the focal plane information at the current moment and the previous moment. The weight of the distance, eliminating the local extreme value, and completing the confocal process by optimizing the iterative control pointing to the execution structure.

The embodiment of the present invention is an eight-aperture imaging system, and the specific implementation steps are as follows:

1) The eight-aperture imaging system converges the beam;

2) Place the detector on the system imaging focal plane, and select the center point (x0, y0) of the focal plane image as the confocal point of the light spot;

3) Use the multi-connected region centroid extraction algorithm to extract the multi-region centroid, as shown in Figure 2, m ≥ 8; obtain the centroid positions (x1, y1), ..., (xm, ym), and calculate these positions and the confocal point. distance;

4) Use the binarized area method to obtain the total spot area S, as shown in Figure 2, Smax is the area when the spots are completely separated and do not overlap;

5) Using the distance and area as the evaluation indicators, carry out the SPGD optimization iteration, drive the high-precision deflection mirror to perform confocal through the servo control module, and combine the information of the current moment and the previous moment to do the proportion and integration of the two frames of information based on the time series. The adaptive factor is obtained by iterative operation, the weight of the area and distance in the evaluation function is adjusted, the evaluation function is adaptively changed to eliminate the local extreme value, and the automatic confocal closed loop of the eight-aperture imaging system is realized. shown.

The above descriptions are merely specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. As long as the evaluation function is constructed using the time-varying area and distance information, the automatic confocal method, algorithm and device for adaptive optimization of the focal plane image of the optical multi-aperture system belong to the protection scope of the present invention.

Claims (6)

1. An automatic confocal method of an optical multi-aperture imaging system is characterized in that: collecting a focal plane point spread function image in a confocal process; calculating the distance between multiple light spots and a common focus by using a multi-connected region centroid extraction algorithm, calculating the total area of the light spots by using a binarization area method, and constructing an evaluation function based on the distance and the area; the focal plane information at the current moment and the previous moment is combined to adaptively adjust the weights of the distance and the area in the evaluation function; the pointing actuator is controlled by an optimization algorithm to optimize an evaluation function, so that automatic confocal of the multi-aperture imaging system is realized.

2. An optical multi-aperture imaging system auto-confocal method according to claim 1, wherein: the centroid position of the multi-spot area is obtained in real time from the image collected by the detector through a multi-connected area centroid extraction algorithm, and each sub-aperture spot is not required to be in a separated or incoherent state.

3. An optical multi-aperture imaging system auto-confocal method according to claim 1, wherein: the evaluation function comprehensively utilizes distance and area information, and avoids the problem of gradient disappearance.

4. An optical multi-aperture imaging system auto-confocal method according to claim 1, wherein: the evaluation function simultaneously utilizes the focal plane information of the current moment and the previous moment, and the local extreme value in the optimization process is reduced.

5. An optical multi-aperture imaging system auto-confocal method according to claim 1, wherein: the initial state is to ensure that all sub-aperture spots are in the detector field of view.

6. An optical multi-aperture imaging system auto-confocal method according to claim 1, wherein: the method comprises the following specific steps:

step 1), carrying out imaging detection on a converged light beam after an n-hole telescope array imaging main mirror, wherein n is more than or equal to 2;

step 2), placing the detector on an optical multi-aperture imaging focal plane, and selecting a point (x0, y0) on the focal plane as a light spot confocal point;

step 3), extracting multi-region centroids through a multi-connected region centroid extraction algorithm, wherein the number m of the centroids is more than or equal to n, and obtaining centroid positions (x1, y1), …, (xm, ym) so as to calculate and obtain distance information with a common focus;

step 4), obtaining the total area S of the light spots by a binarization area method, wherein Smax is the area of the light spots which are completely separated and have no overlapped area;

and 5) constructing an evaluation function by using the distance and the area, optimizing and iterating, driving the high-precision deflection mirror to perform confocal through the servo control module, and adaptively adjusting the weight of the area and the distance in the evaluation function according to the distance and the area information at the current moment and the previous moment to finally realize the automatic confocal closed loop of the n-hole telescope array, wherein the light spot is coincided with the light spot confocal point after the closed loop.

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