CN109522573B

CN109522573B - Simulation method of active optical system of optical remote sensing camera

Info

Publication number: CN109522573B
Application number: CN201710852253.5A
Authority: CN
Inventors: 李晓波; 杨勋
Original assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Current assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Priority date: 2017-09-20
Filing date: 2017-09-20
Publication date: 2023-03-21
Anticipated expiration: 2037-09-20
Also published as: CN109522573A

Abstract

The embodiment of the invention discloses a simulation method of an active optical system of an optical remote sensing camera, which integrates three disciplines of optics, machinery and control, relates to an optical structure of the camera, a six-degree-of-freedom active optical execution mechanism, a wavefront sensing algorithm, a correction quantity algorithm and an error item simulation model, and is easier to obtain a global optimal solution compared with single discipline optimization when global optimization is developed on the basis of the simulation model. The embodiment effectively solves the problems that the existing active optical simulation method adopts a single discipline and ideal model, which causes larger error and is difficult to simulate the actual active optical correction process.

Description

Simulation method of active optical system of optical remote sensing camera

Technical Field

The invention relates to the technical field of optical remote sensing camera integrated simulation, in particular to a simulation method of an active optical system of an optical remote sensing camera.

Background

The optical remote sensing camera is widely applied to the fields of resource detection, national survey, astronomical observation and the like, and plays an important role in economic and social development and scientific research. At present, the technical development trend of optical remote sensing cameras is towards the directions of large caliber, large visual field, high resolution and the like, the difficulty of corresponding processing, manufacturing, supporting and adjusting is increased, and the optical remote sensing cameras are easily interfered by factors such as emission, gravitational environment, temperature and the like in the actual imaging process, so that the observation performance is influenced.

Currently, two methods are used to improve the observation performance of optical remote sensing cameras: one is passive optics and the other is active optics. The passive optics adopts a hard-reactance mode, adopts a material with high rigidity and zero expansion coefficient and a complex support design structure to ensure the imaging quality of the camera, but the mode has high realization difficulty, and simultaneously has the problems of cost improvement, reliability reduction and the like. The active optics takes image quality detection as an evaluation standard and a feedback channel, and actively adjusts the wave phase difference of the system by adjusting the mirror surface shape, the reflector posture and the like, thereby improving the imaging quality to the design level.

Currently, active optical technology can be applied to ground-based or space equipment. Whether ground-based active optics or space active optics, a large number of simulation tests are required. The existing active optical simulation method usually adopts a single-disciplinary and idealized model, and the error caused by the simulation method is large and the actual active optical correction process is difficult to simulate.

Therefore, it is necessary to provide an active optical simulation method capable of integrating multiple disciplines, so as to comprehensively consider correction strategies, sensitivity calculation and control execution, thereby considering error terms in the actual process and realizing simulation of active optical image quality correction in the actual process.

Disclosure of Invention

Aiming at the problems that the single discipline and ideal models are adopted in the existing active optical simulation method, so that the error is large and the actual active optical correction process is difficult to simulate, the embodiment of the invention provides the active optical simulation method integrating multiple disciplines, which effectively combines factors such as correction strategies, sensitivity calculation, control execution and the like, considers error items in the actual process and realizes the simulation of the active correction of the optical image quality in the actual process.

The method comprises the following specific scheme: a simulation method of an active optical system of an optical remote sensing camera comprises the following steps: step one, establishing an optical model of a camera, and calculating the full-field average wave aberration in an initial state; step two, establishing a structural model and a finite element model of the camera, and calculating rigid body displacement and surface shape Zernike coefficients of each reflector caused by changes of the ground and the on-orbit environment; step three, establishing an optical system wavefront sensing algorithm and an active optical correction value solving algorithm model; step four, establishing a dynamic model of the camera, calculating a transfer function in the model, and establishing a six-degree-of-freedom active optical actuator control algorithm model based on the dynamic model and the transfer function; and fifthly, integrating the optical model, the dynamic model and the control algorithm model together to perform active optical simulation.

Preferably, in the fifth step, the optical model, the dynamic model and the control algorithm model are integrated into an isight platform to form a simulation model, and the rigid body displacement and the surface zernike coefficient obtained in the second step are used as input parameters to perform iterative correction in the simulation model until the system wave aberration of the model reaches the full-field average wave aberration in the initial state.

Preferably, in the fifth step, at least one error of a machining error, a setup error, a calculation error and an execution error is used as an input parameter.

Preferably, in the first step, the optical model is an optical full model from each optical reflection mirror surface to an imaging focal plane, and an average value obtained by the imaging focal plane is used as an average wave aberration of a full field of view in an initial state.

Preferably, the optical model is designed and simulated by using optical software Code V or Zemax.

Preferably, the ground and on-orbit environmental change in the second step includes at least one of emission vibration, gravity, impact and temperature change.

Preferably, the finite element model is modeled and solved using MSC.

Preferably, in the second step, the rigid body displacement and the surface zernike coefficient of each reflector are obtained by fitting through optical machine integration tool software Sigfit.

Preferably, the third step specifically includes selecting a plurality of fields on the imaging focal plane as wavefront sensing measurement fields, generating PSF images under the focal condition and the defocused condition of the wavefront sensing measurement fields as input of wavefront calculation, obtaining system wave aberration by using a wavefront sensing algorithm, and obtaining correction values required by each optical assembly by using a correction value calculation algorithm.

Preferably, the kinetic model is established using the Adams and MATLAB/Simulink software platforms.

According to the technical scheme, the embodiment of the invention has the following advantages:

the embodiment of the invention provides an active optical system simulation method for integrating three disciplines of light, machine and control, and relates to a camera optical-mechanical structure, a six-degree-of-freedom active optical execution mechanism, a wavefront sensing algorithm, a correction quantity algorithm and an error item simulation model. The embodiment of the invention also considers actual error factors such as a wavefront sensing algorithm, the calculation of a correction value, the processing and execution precision of a supporting leg and a spherical hinge of the six-degree-of-freedom active optical execution mechanism, the assembly error of the six-degree-of-freedom active optical execution mechanism and the like in an actual active optical correction integrated model, so that the actual correction process is closer to the actual correction process, and the problem in the actual design is favorably found. The embodiment of the invention also converts the dynamic model into an MATLAB/Simulink platform, thereby easily exchanging data with the control model, and integrates the optical model, the dynamic model and the control model into an ight platform, thereby effectively realizing the integrated simulation analysis of light, machine and control.

Drawings

FIG. 1 is a flow chart illustrating a simulation method for an active optical system according to an embodiment of the present invention;

FIG. 2a is a diagram illustrating a wavefront sensing view field focal PSF image in an embodiment of the present invention;

FIG. 2b is a diagram illustrating a PSF image of a wavefront sensing field of view that is out of focus in an embodiment of the present invention;

FIG. 3 is a schematic diagram of an active optical calibration process of an optical remote sensing camera according to an embodiment of the present invention;

FIG. 4 is a diagram of inverse kinematics calculation simulation of a six-degree-of-freedom adjustment mechanism in a Simulink environment according to an embodiment of the present invention;

FIG. 5 is another method of presenting the flow diagram of FIG. 1.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terms "first," "second," "third," "fourth," and the like in the description and in the claims, as well as in the drawings, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Referring to fig. 1, a flow chart of a simulation method of an active optical system according to an embodiment of the present invention is shown. The method mainly comprises five steps, and the specific steps are as follows.

Step S1: and establishing an optical model of the camera, and calculating the full-field average wave aberration in the initial state. An optical model of the camera is established by adopting optical software Code V or Zemax, and the average wave aberration RMS-0 of the whole field of view of the optical system in an initial design state is calculated. In an actual optical system, since wave aberration is affected by the position of the field of view, its distribution is not uniform over the entire field of view. In this embodiment, the average value of the wave aberration of the full field of view is found, and this average value is taken as the wave aberration RMS _0 of the initially designed optical system, thereby effectively equalizing the unevenness of the wave aberration caused by the change in the position of the field of view.

Step S2: and establishing a structural model and a finite element model of the camera, and calculating rigid body displacement U and surface Zernike (Zernike) coefficient U' of each reflector caused by the change of the ground and on-orbit environment. In this embodiment, a three-dimensional structure model of the camera is created using three-dimensional design software, and a finite element model is created using finite element analysis software. The three-dimensional design software comprises Solidworks, pro-E, 3ds-Max, rhino, maya and the like, and a designer selects appropriate software according to the complexity of a camera structure model and hardware conditions. The finite element analysis software comprises MSC, patran, MSC/NASTRAN, ANSYS, patran/Nastran, abaqus, hypermesh and the like, and designers select proper software according to analysis requirements and hardware conditions.

And loading working conditions according to the actual constraint state and boundary conditions, calculating the displacement of each reflector mirror surface node in finite element software, and respectively fitting each mirror surface node by using an optical machine integration tool sigfit to obtain each reflector rigid body displacement U caused by the change of the ground and on-orbit environment of the camera and a surface shape U' represented by a surface shape Zernike (Zernike) polynomial. Ground and on-orbit environmental changes generally include launching vibrations, impacts, gravitational environments, temperature environments, and the like.

And step S3: and establishing an optical system wavefront sensing algorithm and an active optical correction value solving algorithm model. And establishing an optical system wavefront sensing algorithm and an active optical correction value solving algorithm model in Matlab software. The wavefront sensing generally adopts a Phase Difference (PD) algorithm, which is mainly used for calculating a system aberration Zernike (Zernike) coefficient U' of the camera in a disturbance state. The wavefront sensing input includes an out-of-focus PSF image and an in-focus PSF image. And respectively acquiring an in-focus PSF image and an out-of-focus PSF image of the same star point target by Matlab driving optical software. Fig. 2 (a) and 2 (b) show an in-focus PSF image and an out-of-focus PSF image acquired by Matlab on the same star target, respectively. From comparison, the in-focus PSF image occupies fewer pixel points than the out-of-focus PSF image. The two images, the in-focus image and the out-of-focus image, are typically converted into a matrix representation to facilitate the solution calculations. And finally, solving the adjustment quantity of the reflector through an active optical adjustment quantity resolving model. Preferably, an optical software plug-in is installed in Matlab software to drive the optical software to generate in-focus and out-of-focus images.

And step S4: the method comprises the steps of establishing a dynamic model of a camera, calculating a transfer function in the model, and establishing a six-degree-of-freedom active optical actuator control algorithm model based on the dynamic model and the transfer function. And establishing a rigid-flexible coupling dynamic model of the camera according to the structural model characteristics of the camera in the step S2. In this embodiment, the active optical actuator may also adopt other degree-of-freedom mechanisms, such as a five-degree-of-freedom actuator and a three-degree-of-freedom actuator, and the specific degree-of-freedom parameters may be selected in due course according to the accuracy requirement. In this embodiment, the adjustment of the active optical system requires precise movement of the mirror by the amount of adjustment. Specific embodiment as shown in fig. 3, the active optical correction system of the optical remote sensing camera includes a primary mirror 300, a secondary mirror 400, a six-degree-of-freedom active optical actuator 100 located at the back of the secondary mirror 400, and an object 200 observed by the optical remote sensing camera. The six-degree-of-freedom active optical actuator 100 on the back of the secondary mirror 400 is used to drive the secondary mirror 400 to perform active calibration. In order for the six-dof active optical actuator 100 to accurately move the secondary mirror 400, the transfer function of the six-dof active optical actuator needs to be calculated. The amplitude-frequency and phase-frequency curves of the six-degree-of-freedom active optical actuator are obtained through the transfer function of the six-degree-of-freedom active optical actuator, and a control algorithm model of the six-degree-of-freedom active optical actuator is established on the basis of the amplitude-frequency and phase-frequency curves for driving the adjusting mechanism.

The six-degree-of-freedom active optical actuator drives the movement amount of the secondary mirror, and conversion is performed according to the adjustment amount required by the mirror calculated in step S3. In this embodiment, the specific process of converting the required adjustment of the mirror into the extension or shortening of the legs of the six-degree-of-freedom active optical actuator is shown in fig. 4. As shown in fig. 4, in the conversion process, a simulation algorithm is used to perform inverse kinematics calculation of the six-degree-of-freedom active optical actuator in the Simulink environment. In fig. 4, 1 represents the displacement Δ X of the mirror to be adjusted in the X direction; 2 represents the displacement delta Y of the reflector needing to be adjusted in the Y direction; 3 represents the displacement delta Z of the reflector needing to be adjusted in the Z direction; 4 represents an angle Δ RX of the reflector needed to be adjusted around the X-axis direction; 5 represents an angle delta RY of the reflector needing to be adjusted around the Y-axis direction; 6 represents an angle delta RZ of the reflector needing to be adjusted around the Z-axis direction; 7 represents a new length L1 of the support leg of the six-degree-of-freedom active optical actuator after being extended/shortened; 8 represents a new length L2 of the supporting leg of the six-degree-of-freedom active optical actuator after being extended or shortened; 9 represents a new length L3 of the supporting leg of the six-degree-of-freedom active optical actuator after being extended or shortened; 10 represents a new length L4 of the leg of the six-degree-of-freedom active optical actuator after extension/contraction; 11 represents a new length L5 of the leg of the six-degree-of-freedom active optical actuator after extension/contraction; 12 represents the new length L6 of the leg of the six-degree-of-freedom active optical actuator after extension/contraction. By adopting the simulation algorithm, the adjustment quantity required by the reflector can be converted into the extension quantity or the shortening quantity of the supporting leg of the six-degree-of-freedom active optical actuating mechanism. And then the supporting leg elongation or shortening obtained by simulation is adopted to drive the reflector to realize the attitude adjustment quantity solved by the active optical correction value solving algorithm in the step S3.

Preferably, the kinetic model is established using the Adams and MATLAB/Simulink software platforms to facilitate data exchange with the control model.

And S5, integrating the optical model established in the step S1, the dynamic model established in the step S4 and the control algorithm model together to perform active optical simulation. The specific simulation steps are as follows: integrating an optical model, a dynamic model and a control algorithm model under an light platform through software interface programs to form light, machine and control integrated simulation; substituting each reflector rigid body displacement U and a Zernike (Zernike) coefficient U 'obtained by calculation in the step S2 into an optical model to obtain an imbalance optical system, wherein the average wave aberration of the imbalance optical system is RMS _0'; performing wavefront calculation on the detuning optical system to solve the adjustment quantity; and then the adjustment amount is realized through a six-degree-of-freedom adjusting mechanism and a control algorithm. In the preferred embodiment, factors such as machining errors, assembly and adjustment errors, solving errors, execution errors and the like are considered in the design process of the simulation model.

Active optical correction typically requires multiple iterations to correct the detuned optical system wave aberration RMS _0' to the RMS _0 level. The calculation method of the wave aberration RMS _0' of the detuned optical system is the same as the calculation method of the wave aberration RMS _0 of the initially designed optical system, and the average value of the wave aberration of the system is used.

In the embodiment, the optical model, the dynamic model and the control model are integrated under the light platform, so that the integrated simulation analysis of light, machine and control is effectively realized.

The simulated active optical process in the above embodiment is a one-time complete active optical correction process of the optical remote sensing camera, and mainly takes active adjustment of the posture of the mirror as an example for explanation. Other methods for adjusting the mirror profile are similar to those provided in the present embodiment, and will be apparent to those skilled in the art in light of the foregoing embodiments, and will not be described herein. The above embodiment optimizes parameters such as structural parameters, control parameters, algorithm parameters and the like on the basis of simulation to obtain a global optimal solution. Because the optimal adjustment of the parameters needs to be adjusted in real time by combining the actual application condition and the simulation condition of the optical remote sensing camera, the change form and the range are more, and the optimization is not expanded here.

The flowchart shown in fig. 1 is divided according to the operation steps of the simulation method, which can also be explained by using the flowchart shown in fig. 5 according to the optical system calibration flow. As shown in fig. 5, the method includes 6 steps. In step S11, an initial optical system is designed; obtaining the detuning optical system of the step S22 by simulating rigid body displacement of the optical element; through wavefront solution and pose solution, the settlement amount of the secondary mirror and the position attitude of the focusing mirror is obtained in step S33; through inverse motion calculation, the elongation or shortening of the secondary mirror and the six-legged supporting leg of the focusing mirror (equivalent to the supporting leg of the six-degree-of-freedom active optical actuator in fig. 1) in S44 is obtained; controlling the six-legged support leg to move according to a control algorithm, so as to correct the optical system in the step S55; in step S66, it is determined whether the average wave aberration RMS _0' of the corrected detuned optical system reaches the average wave aberration RMS _0 of the initial optical system in step S11, and if so, the whole adjustment process is ended; and if not, jumping to the wavefront calculation and pose calculation step before the step S33, and continuing to circulate.

In the flow steps shown in fig. 5, the specific solving processes of wavefront solution, pose solution, and inverse motion solution are as described in the embodiment in fig. 1, and are not described herein again.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Moreover, various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without being mutually inconsistent.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. A simulation method of an active optical system of an optical remote sensing camera is characterized by comprising the following steps:

step one, establishing an optical model of a camera, and calculating the full-field average wave aberration in an initial state;

step two, establishing a structural model and a finite element model of the camera, and calculating rigid body displacement and surface-shaped Zernike coefficients of each reflector caused by changes of the ground and the on-orbit environment;

establishing an optical system wavefront sensing algorithm and an active optical correction value solving algorithm model;

step four, establishing a dynamic model of the camera, calculating a transfer function in the model, and establishing a six-degree-of-freedom active optical actuator control algorithm model based on the dynamic model and the transfer function;

integrating the optical model, the dynamic model and the control algorithm model together to perform active optical simulation;

the optical model in the first step is an optical full model from each optical reflector to an imaging focal plane, and an average value obtained by the imaging focal plane is used as an average wave aberration of a full field of view in an initial state;

and step five, integrating the optical model, the dynamic model and the control algorithm model to an height platform to form a simulation model, taking the rigid body displacement and the surface-shaped Zernike coefficient obtained in the step two as input parameters, and performing iterative correction in the simulation model until the system wave aberration of the model reaches the full-field average wave aberration in the initial state.

2. The method as claimed in claim 1, wherein at least one of machining error, setup error, solution error and execution error is used as input parameter in the step five.

3. The method for simulating the active optical system of the optical remote sensing camera according to claim 1, wherein the optical model is designed and simulated by adopting optical software Code V or Zemax.

4. The method for simulating the active optical system of the optical remote sensing camera according to claim 1, wherein the ground and on-orbit environmental changes in the second step include at least one of emission vibration, gravity, impact and temperature change.

5. A method for simulating an active optical system of an optical remote sensing camera according to claim 1, characterized in that the finite element model is modeled and solved using MSC.

6. The method according to claim 1, wherein in step two, the rigid body displacement and the surface zernike coefficients of each reflector are obtained by fitting using optical machine integration tool software Sigfit.

7. The method for simulating the active optical system of the optical remote sensing camera according to claim 1, wherein the third step specifically comprises selecting a plurality of fields of view on an imaging focal plane as wavefront sensing measurement fields of view, generating a PSF image under a focal condition and a PSF image under an out-of-focus condition of the wavefront sensing measurement fields of view as input of wavefront calculation, obtaining system wavefront aberration by adopting a wavefront sensing algorithm, and obtaining correction values required by each optical component by adopting a correction value solving algorithm.

8. The method for simulating the active optical system of the optical remote sensing camera according to claim 1, wherein the dynamic model is built by using Adams and MATLAB/Simulink software platforms.