A method for controlling a large field of view telescope variable mirror surface type

Abstract

The application is a large field telescope deformable mirror surface type control method, comprising: (1) determining the actuator arrangement matrix M according to the arrangement of the deformable mirror actuator; (2) measuring the on-axis field optical transfer function matrix W corresponding to the deformable mirror in the system; (3) calling the pupil shape matrix P of the field according to the field coordinate Φ Φ ; (4) screening the effective actuator M Φ of the deformable mirror under the field M Φ =P ; (5) calculating the effective transfer function W Φ of the deformable mirror in the field according to the effective actuator W Φ =M ; (6) calculating the voltage value of each actuator according to the input deformable mirror surface type Ψ Φ , generating the control voltage vector (7) limiting the voltage of the edge actuator, calculating the final control voltage vector V' Φ =V Φ ×F; (8) outputting the voltage vector and loading to the deformable mirror, completing the closed-loop control of the deformable mirror.

Description

Technical Field

[0001] This invention relates to the field of aberration correction in telescope systems, specifically to a method for controlling the deformable mirror shape of a large field-of-view telescope with variable pupil. This method is applicable to high-precision deformable mirror shape control in large field-of-view telescope optical systems. Background Technology

[0002] To detect distant and fainter targets, telescope apertures and fields of view are constantly increasing, along with resolution. To simultaneously achieve a large field of view, large aperture, and high resolution, deformable mirrors are typically used for aberration correction. However, for large field-of-view telescopes, especially coaxial systems, there is central obstruction. Furthermore, other optical elements and mechanical structures also obstruct the system, resulting in different pupil shapes for different fields of view. If the traditional method of calculating the off-axis field-of-view deformable mirror voltage based on the on-axis field-of-view transfer function is used, the aberration correction effect will be poor due to effective actuator mismatch, failing to meet the high-resolution requirements. Currently, deformable mirrors are mostly used in small field-of-view systems; therefore, research on how to accurately calculate the control voltage of deformable mirrors in large field-of-view optical systems is still limited. A common method is to measure the transfer function of the deformable mirror in the system at different fields of view, but this method increases the complexity of the correction process. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention discloses a method for controlling the deformable mirror type of a large field-of-view telescope with variable pupil. This method only requires measuring the transfer function of the on-axis field of view. For the off-axis field of view, the effective transfer function is calculated through the pupil function, and the wavefront is smoothed by limiting pressure. This method does not require measuring the optical transfer function of the deformable mirror on-axis and in multiple off-axis fields of view, simplifying the correction process and effectively improving the correction efficiency and accuracy of off-axis field-of-view aberrations. The significant features of this invention are its simple correction process, ease of implementation, and wide applicability. It is applicable not only to reflective systems but also to catadioptric systems; not only to coaxial systems but also to off-axis systems; not only to ground-based telescopes but also to space-based telescopes; and not only to telescope systems but also to other adaptive optics systems containing deformable mirrors.

[0004] The technical solution adopted in this invention is: a method for controlling the deformable mirror shape of a large field-of-view telescope with variable pupil, comprising the following steps:

[0005] Step (1): Determine the arrangement matrix M of the deformable mirror actuators;

[0006] Step (2): Measure the transfer function matrix W of the field of view on the deformable mirror axis;

[0007] Step (3): Call the pupil shape matrix P corresponding to the field of view Φ. Φ ;

[0008] Step (4): Select the effective actuator M for the field deformable mirror. Φ =M×P Φ ;

[0009] Step (5): Generate the deformable mirror transfer function W for the field of view based on the effective actuator. Φ =W×M Φ ;

[0010] Step (6): Based on the input deformable mirror shape Ψ Φ Calculate the voltage of each actuator

[0011] Step (7): Limit the pressure V' on the edge actuator. Φ =V Φ ×F;

[0012] Step (8), Output voltage vector V' Φ And load it onto the deformable mirror.

[0013] Furthermore, in step (1), the arrangement matrix M of the deformable mirror actuators is determined either by determining the arrangement of each actuator according to the deformable mirror design scheme and generating the arrangement matrix M, or by measuring the actuator arrangement using the self-collimating interferometry method and generating the arrangement matrix M based on the centroid position of the influence function of each actuator.

[0014] Furthermore, in step (2), the transfer function matrix W of the field of view on the deformable mirror axis can be measured either by self-collimation interferometry or by a Shack-Hartmann detector.

[0015] Furthermore, in step (3), the pupil shape matrix P corresponding to the field of view Φ It can be obtained by setting different fields of view in optical design software, or it can be calculated directly based on ray tracing.

[0016] Furthermore, in step (4), the effective actuator for screening the deformable mirror is determined by the pupil shape matrix P. Φ The value is obtained by multiplying the average arrangement of the deformable mirror actuators. Actuators within the aperture range are considered effective actuators and are set to 1, while actuators outside the aperture range are considered ineffective actuators and are set to 0.

[0017] Furthermore, in step (5), the deformable mirror transfer function of the field of view is generated based on the effective actuator. This is achieved by selecting the effective actuator through the pupil function and then using the effective actuator matrix M. ΦMultiply by the influence function of each actuator to make the actuator influence function within the light-transmitting area valid, while setting the actuator influence function outside the light-transmitting area to zero, thus invalid.

[0018] Furthermore, in step (6), based on the input deformable mirror type Ψ Φ Calculate the voltage of each actuator in This is the pseudo-inverse of the actuator influence function.

[0019] Furthermore, in step (7), the edge actuator is subjected to a pressure limit V'. Φ =V Φ ×F, where F is the pressure limiting factor. For traditional deformable mirrors with actuators perpendicular to the mirror surface, it can be determined based on the proportion of the actuator in the light transmission aperture. For deformable mirrors with actuators parallel to the mirror surface, it needs to be determined based on the cross-linking coefficient of the influence function of adjacent actuators.

[0020] Furthermore, in step (8), the output voltage vector V' Φ It is then applied to the deformable mirror to create a specific surface shape to compensate for aberrations.

[0021] The advantages of this invention compared to the prior art are:

[0022] (1) This invention only requires measuring the optical transfer function of the on-axis field of view, and does not require measuring the optical transfer function of the off-axis field of view. This can effectively reduce the complexity of the algorithm, simplify the correction process, and improve the correction efficiency.

[0023] (2) This method can achieve high-precision correction of on-axis and off-axis field aberrations of deformable mirrors in large-aperture, large-field-of-view telescope systems.

[0024] (3) This method has a wide range of applications and is applicable to all optical systems containing deformable mirrors. It is applicable not only to reflective systems but also to catadioptric systems; not only to coaxial systems but also to off-axis systems; not only to ground-based telescopes but also to space-based telescopes; not only to telescope systems but also to other adaptive optics systems containing deformable mirrors.

[0025] In summary, this invention solves the problem of high-precision surface shape control of the on-axis and off-axis fields of view of the deformable mirror in a large field-of-view telescope with variable pupil, providing technical support for achieving high-resolution imaging of the telescope system. Attached Figure Description

[0026] Figure 1 This is a flowchart of a method for controlling the deformable mirror type of a large field-of-view telescope with variable pupil according to the present invention;

[0027] Figure 2It is the first implementation example showing the wavefront, pupil shape, and effective actuator under different fields of view;

[0028] Figure 3 This is the distribution of residual wave aberration RMS values ​​in each field of view after correction when performing aberration correction based on the optical transfer function of the deformable mirror on-axis in the first implementation example.

[0029] Figure 4 The first implementation example shows the distribution of residual wave aberration RMS values ​​in each field of view after aberration correction when performing aberration correction based on the optical transfer function of the corresponding field of view of the deformable mirror. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention should include all the contents of the claims. Through the following embodiments, those skilled in the art can implement all the contents of the claims of the present invention.

[0031] like Figure 1 As shown, a method for controlling the deformable mirror shape of a large field-of-view telescope with variable pupil includes the following steps:

[0032] Step (1): Determine the arrangement matrix M of the deformable mirror actuators;

[0033] In step (1), the arrangement matrix M of the deformable mirror actuators is determined either by determining the arrangement of each actuator according to the deformable mirror design scheme and generating the arrangement matrix M, or by measuring the actuator arrangement using the self-collimating interferometry method and generating the arrangement matrix M based on the centroid position of the influence function of each actuator.

[0034] Step (2): Measure the transfer function matrix W of the field of view on the deformable mirror axis;

[0035] In step (2), the transfer function matrix W of the field of view on the deformable mirror axis is measured. This can be done either by self-collimation interferometry or by using a Shack-Hartmann detector.

[0036] Step (3): Call the pupil shape matrix P corresponding to the field of view Φ. Φ ;

[0037] In step (3), the pupil shape matrix P corresponding to the field of view Φ It can be obtained by setting different fields of view in optical design software, or it can be calculated directly based on ray tracing.

[0038] Step (4): Select the effective actuator M for the field deformable mirror. Φ =M×P Φ ;

[0039] In step (4), the effective actuators for the deformable mirror are selected through the pupil shape matrix P. Φ The value is obtained by multiplying the average arrangement of the deformable mirror actuators. Actuators within the aperture range are considered effective actuators and are set to 1, while actuators outside the aperture range are considered ineffective actuators and are set to 0.

[0040] Step (5): Generate the deformable mirror transfer function W for the field of view based on the effective actuator. Φ =W×M Φ ;

[0041] In step (5), the deformable mirror transfer function of the field of view is generated based on the effective actuator. This is achieved by selecting the effective actuator through the pupil function and then using the effective actuator matrix M. Φ Multiply by the influence function of each actuator to make the actuator influence function within the light-transmitting area valid, while setting the actuator influence function outside the light-transmitting area to zero, thus invalid.

[0042] Step (6): Based on the input deformable mirror shape Ψ Φ Calculate the voltage of each actuator

[0043] In step (6), based on the input deformable mirror type Ψ Φ Calculate the voltage of each actuator in This is the pseudo-inverse of the actuator influence function.

[0044] Step (7): Limit the pressure V' on the edge actuator. Φ =V Φ ×F;

[0045] In step (7), the edge actuator is subjected to a pressure limit V' Φ =V Φ ×F, where F is the pressure limiting factor. For traditional deformable mirrors with actuators perpendicular to the mirror surface, it can be determined based on the proportion of the actuator in the light transmission aperture. For deformable mirrors with actuators parallel to the mirror surface, it needs to be determined based on the cross-linking coefficient of the influence function of adjacent actuators.

[0046] Step (8), Output voltage vector V' Φ And load it onto the deformable mirror.

[0047] In step (8), the output voltage vector V' Φ It is then applied to the deformable mirror to create a specific surface shape to compensate for aberrations.

[0048] Example 1:

[0049] Simulation analysis was performed using an RC optical system with a light-transmitting aperture of 4m and F#=3. The selected field of view is shown in Table 1.

[0050] Table 1 Selected Field of View

[0051] Serial Number 1 2 3 4 5 6 7 Field of view (0°,-1.6°) (0°,-1.2°) (0°,-0.8°) (0°,0°) (0°,0.8°) (0°,1.2°) (0°,1.6°)

[0052] The pupils and effective actuators corresponding to each field of view, such as Figure 2 As shown.

[0053] Depend on Figure 2 It is known that different fields of view correspond to different pupil shapes, resulting in different effective actuators for different fields of view. Given three sets of surface shape errors, deformable mirrors are used to correct the aberrations. The distribution of each order of the Zernike coefficients for the three sets of surface shape errors is shown in Table 2.

[0054] Table 2. Distribution of Zernike coefficients of different orders corresponding to the three groups of surface shape errors.

[0055] Surface error distribution Z4 / λ Z5 / λ Z6 / λ Z7 / λ Z8 / λ Z11 / λ 1 1 1 -1 -1 1 1 2 0.3 -0.2 0.8 0.1 -0.6 -0.5 3 -0.1 0.4 -0.5 0.2 0.3 -0.2

[0056] When the control voltage for aberration correction in different fields of view is calculated using the transfer function of an on-axis field-of-view deformable mirror, the residual wave aberrations in each field of view after correction are as follows: Figure 3 As shown.

[0057] Depend on Figure 3 It is known that for large-field-of-view optical systems with variable pupils, if the traditional method of aberration correction based on the optical transfer function of the deformable mirror's on-axis field of view is used, the correction effect is only good within the on-axis field of view and a very small isohalo region. The corrected wavefront RMS value is better than λ / 10. For off-axis fields of view, due to actuator mismatch, the correction effect is poor and cannot meet the requirements of high-resolution imaging of the optical system. Therefore, for off-axis fields of view, it is necessary to screen effective actuators and calculate the optical transfer function that matches the field of view. The conventional method is usually to measure the transfer function of the deformable mirror in the off-axis field of view. However, in this study, effective actuators are selected through the pupil shape function of different fields of view, and the transfer function of the corresponding field of view is calculated, simplifying the correction process and improving the correction efficiency. When aberration correction is performed using the deformable mirror transfer function of the corresponding field of view, the correction effect is as follows: Figure 4 As shown.

[0058] Depend on Figure 4 It can be seen that for a large field-of-view optical system with variable pupil, when the control voltage is calculated using the optical transfer function of the deformable mirror corresponding to the field of view for aberration correction, a good correction effect can be achieved. After correction, the wavefront RMS value of both the on-axis and off-axis fields of view is better than λ / 20, which can meet the requirements of high-resolution imaging.

[0059] The parts of this invention not described in detail are well-known in the field.

[0060] The above description is merely one embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling a large field-of-view telescope anamorphic mirror of variable pupil, characterized in that, The method comprises the following steps: Step (1), determining the arrangement matrix M of the deformable mirror actuator; Step (2), measuring the transfer function matrix W of the on-axis field of the deformable mirror; Step (3), calling the pupil shape matrix corresponding to the field of view Φ according to the field of view Φ ; Step (4), screening the effective actuators of the field deformation mirror ; Step (5), generating a deformable mirror transfer function for the field of view from the effective actuator ; Step (6), determining the mirror surface type from the input Computing the individual actuator voltages ; Step (7), limiting the pressure of the edge actuator ; Step (8), output voltage vector and loaded to the deformable mirror; In the step (6), the deformed mirror surface type is determined according to the input Computing the individual actuator voltages wherein is the pseudo-inverse of the deformed mirror transfer function; The step (7) limits the voltage of the edge actuator Wherein F is a voltage limiting factor, for a conventional actuator deformable mirror perpendicular to the mirror surface, F is determined according to the proportion of the actuator in the clear aperture; for an actuator deformable mirror parallel to the mirror surface, F is determined according to the cross-linking coefficient of the adjacent actuator influence function.

2. The method of claim 1, wherein: The method has wide application range and is suitable for all optical systems comprising a deformable mirror, is suitable for not only a reflection system but also a catadioptric system, is suitable for not only a coaxial system but also an off-axis system, is suitable for not only a ground-based telescope but also a space-based telescope, and is suitable for not only a telescope system but also other adaptive optical systems comprising a deformable mirror.

3. The method of claim 1, wherein: In the step (1), the arrangement matrix M of the deformable mirror actuator can be determined according to a design scheme of the deformable mirror to generate the arrangement matrix M of the actuator, or the arrangement of the actuator can be measured by a self-collimation interference measurement method to generate the arrangement matrix M according to the centroid positions of the influence functions of the actuators.

4. The method of claim 1, wherein: In the step (2), the transfer function matrix W of the on-axis field of the deformable mirror can be measured by a self-collimation interference method or a Shack-Hartmann detector.

5. The method of claim 1, wherein: In the step (3), the pupil shape matrix corresponding to the field of view It can be obtained from optical design software by setting different fields of view, or directly calculated according to the ray tracing method.

6. The method of claim 1, wherein: In the step (4), the effective actuators of the deformable mirror are screened by multiplying the pupil shape matrix The effective actuators are obtained by multiplying the arrangement matrix of the actuators of the deformable mirror, and the actuators within the clear aperture range are effective actuators, and are set to 1, and the actuators outside the clear aperture range are ineffective actuators, and are set to 0.

7. The method of claim 1, wherein: In step (5), the effective actuators are selected by the pupil function, and the effective actuator matrix is multiplied by the influence function of each actuator to make the actuator influence function effective in the through-illumination area and the actuator influence function outside the through-illumination area zero, i.e. invalid. The effective actuators are selected by the pupil function, and the effective actuator matrix is multiplied by the influence function of each actuator to make the actuator influence function effective in the through-illumination area and the actuator influence function outside the through-illumination area zero, i.e. invalid.

8. The method of claim 1, wherein: In the step (8), the output voltage vector The method does not need to measure the deformation mirror transfer function corresponding to each field of view, only needs to measure the optical transfer function of the on-axis field of view, the deformation mirror transfer function of the off-axis field of view is calculated through the pupil function, and the wave surface is smoothed through voltage limiting, so that the correction process is simplified, and high-precision correction of the on-axis and off-axis field aberrations can be realized.

Images