Wavefront control device for adaptive optical telescope based on variable resolution Hartmann

Abstract

The present invention discloses a variable resolution Hartmann-based adaptive optical telescope wavefront control device, comprising a reflective primary mirror, a deformable secondary mirror, an active deformable secondary mirror support frame, a beam splitter, a microlens array, a wavefront detector, a fine-tuning translation stage, a spatial resolution adjustment translation stage, an imaging detector, a control computer and a driver. By combining the deformable secondary mirror and the variable spatial resolution wavefront detector, the original adaptive optical telescope system architecture is greatly simplified, and the system's detection capability for weak targets is greatly improved. At the same time, the system has higher adaptability and is suitable for tracking and imaging detection capabilities of targets with various extension degrees.

Description

Technical Field

[0001] The invention relates to an adaptive optical system, in particular to an adaptive optical telescope wavefront control device based on variable resolution Hartmann. Background Art

[0002] Adaptive optics technology is an effective measure to solve the problem of image quality degradation caused by temporal and spatial wavefront distortion. Conventional adaptive optical systems need to go through multiple optical transfer systems to achieve optical aperture matching, which has a complex structure and low light energy utilization. At the same time, conventional adaptive optical systems have limited adaptive capabilities and can only work effectively within the design range, which limits the expansion of adaptive optical systems.

[0003] To this end, domestic and foreign counterparts have carried out a lot of research work on wavefront correctors and wavefront detectors. The adaptive optical system based on deformable secondary mirrors has greatly simplified the system structure. However, since the system still uses the traditional Hartmann sensor, the system light energy utilization rate has not been maximized, and the scope of application of the adaptive optical system is still limited. Although the adaptive optical system without wavefront sensor is the simplest in structure and light energy utilization, the complex coupling optical system between the wavefront detector and the wavefront corrector has greatly limited the real-time effect of adaptive optical wavefront control.

[0004] Until recently, we proposed the spatially variable resolution Hartmann sensor, which has well preserved and utilized both detection flexibility and detection energy utilization, but the previous work was limited to the scope of wavefront detection.

[0005] The above methods have solved the requirement of variable resolution for wavefront detection to varying degrees, but it is also obvious that there are problems when using the above methods, such as low light energy utilization and a small scope of application. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in view of the above-mentioned difficulties and contradictions, a variable resolution Hartmann-based adaptive optical telescope wavefront control device is provided, which is a new adaptive optical system based on a deformable secondary mirror and a Hartmann sensor with variable spatial resolution. The device combines a deformable secondary mirror and a Hartmann sensor with variable spatial resolution into a closed-loop control system to achieve effective detection and control of temporal and spatial wavefront distortion. The combined use of the deformable secondary mirror and the Hartmann sensor with variable spatial resolution enables the new adaptive optical system to have both the simplest optical path structure and stronger adaptability, thereby maximizing the utilization rate of light energy.

[0007] The reason why the present invention can achieve a more compact and simple optical path structure while retaining the original working performance of traditional adaptive optics is that the key lies in the combination of the deformable secondary mirror and the Hartmann sensor with variable spatial resolution, that is, two devices working on spherical waves. Whether it is a traditional adaptive optical system or an adaptive optical system based on a deformable secondary mirror, it either adopts a planar reflector structure or a Hartmann sensor working on parallel light incidence. The wavefront corrector and the wavefront detector need to satisfy the aperture matching relationship. Therefore, the optical path structure is necessarily more complex than the present invention. Based on the spherical Hartmann, the present invention introduces a variable spatial resolution structure, so that the spatial resolution and field size of the Hartmann sensor are adjustable, and the adaptability of the system is further improved, which is suitable for real-time wavefront control of targets with different extension degrees and field of view targets.

[0008] The technical solution adopted by the present invention is: a variable resolution Hartmann-based adaptive optical telescope wavefront control device, including a reflective primary mirror, a deformable secondary mirror, an active deformable secondary mirror support frame, a dichroic prism, a field diaphragm, a microlens array, a wavefront detector, a fine-tuning translation stage, a spatial resolution adjustment translation stage, an imaging detector, a control computer and a driver. The working process of the device light path is as follows: the incident light from the field of view of the telescope is reflected by the reflective primary mirror and reaches the deformable secondary mirror. After the wavefront information of the deformable secondary mirror is regulated, the transmitted light enters the variable resolution Hartmann sensor after passing through the dichroic prism and the field diaphragm, and the reflected light enters the imaging detector. Among them, the variable resolution Hartmann sensor is composed of a microlens array, a wavefront detector, a fine-tuning translation stage and a spatial resolution adjustment platform. The variable resolution Hartmann sensor controls the fine-tuning translation stage and the spatial resolution adjustment platform according to the intensity of the incident light beam and the degree of wavefront distortion. Taking the intensity information obtained by the wavefront detector as an indicator, the spatial resolution of the wavefront detector is increased or decreased by moving the spatial resolution adjustment platform back and forth. Under the condition that the signal-to-noise ratio of the wavefront detector spot is greater than the specified target N, the spatial resolution of the wavefront detector is maximized, where N is a real number greater than 1; the active deformable secondary mirror support frame is used to support the deformable secondary mirror to achieve the overall angle, translation and front and back position adjustment of the deformable secondary mirror; the driver realizes the driving of the active components of the deformable secondary mirror and the active deformable secondary mirror support frame; the control computer realizes feedback control of the deformable secondary mirror and the active deformable secondary mirror support frame according to the wavefront distribution information obtained by the variable resolution Hartmann sensor and the imaging information of the imaging detector.

[0009] Furthermore, in the variable resolution Hartmann-based adaptive optical telescope wavefront control device, the deformable secondary mirror uses piezoelectric or magnetostrictive materials or a voice coil motor to drive the mirror surface to deform, and the deformable secondary mirror surface can be a convex or concave mirror.

[0010] Furthermore, in the variable resolution Hartmann-based adaptive optical telescope wavefront control device, the dynamically deformable secondary mirror support frame adopts a six-axis parallel platform or a piezoelectric inertial six-axis positioning platform.

[0011] Furthermore, in the variable resolution Hartmann-based adaptive optical telescope wavefront control device, the beam splitter prism is implemented using an intensity beam splitter, a spectrum beam splitter or a polarization beam splitter device.

[0012] Furthermore, in the variable resolution Hartmann-based adaptive optical telescope wavefront control device, the wavefront detector and the imaging detector adopt a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) detector.

[0013] Furthermore, in the variable resolution Hartmann-based adaptive optical telescope wavefront control device, the control computer can be a high-performance desktop computer or an embedded computing platform.

[0014] Furthermore, in the variable resolution Hartmann-based adaptive optical telescope wavefront control device, the feedback control process adopts a proportional-integral control method, and the calculation method of the wavefront to the voltage of the deformable secondary mirror piezoelectric driver adopts a pattern or direct slope recovery algorithm.

[0015] The advantages of the present invention compared with the prior art are:

[0016] (1) Compared with the traditional adaptive optical system and the deformable secondary mirror adaptive optical system, the patented structure of the present invention is simpler, uses fewer optical reflective mirrors, and has a higher light energy utilization rate;

[0017] (2) The present invention uses a wavefront detector with variable spatial resolution, which has stronger adaptability and can adapt to complex conditions such as targets with different spreads, targets with different brightness, and different atmospheric turbulence, thereby realizing real-time wavefront detection and correction of wavefront aberrations.

[0018] (3) Compared with the traditional "optical telescope" + "adaptive optics" design model, the present invention has a simple optical structure and a short optical path, which greatly reduces the probability and power of ambient stray light entering the optical detector, while improving the transmittance of target reflected light and significantly improving the comprehensive detection signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the variable resolution Hartmann-based adaptive optical telescope wavefront control device of the present invention. DETAILED DESCRIPTION

[0020] The specific implementation of the variable resolution Hartmann-based adaptive optical telescope wavefront control device proposed by the present invention is described in detail below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the present invention discloses a variable resolution Hartmann-based adaptive optical telescope wavefront control device, comprising a reflective primary mirror 1, a deformable secondary mirror 2, an active deformable secondary mirror support frame 3, a beam splitter prism 4, a field aperture 5, a microlens array 6, a wavefront detector 7, a fine-tuning translation stage 8, a spatial resolution adjustment translation stage 9, an imaging detector 10, a control computer 11 and a driver 12. The working process of the device light path is as follows: the incident light from the field of view of the telescope is reflected by the reflective primary mirror 1 and reaches the deformable secondary mirror 2. After the wavefront information of the deformable secondary mirror 2 is regulated, the transmitted light enters the variable resolution Hartmann sensor after passing through the beam splitter prism 4 and the field aperture 5, and the reflected light enters the imaging detector 10; wherein the variable resolution Hartmann sensor is composed of a microlens array 6, a wavefront detector 7, a fine-tuning translation stage 8 and a spatial resolution adjustment platform 9. The Hartmann sensor controls the fine-tuning translation stage 8 and the spatial resolution adjustment platform 9 according to the intensity of the incident light beam and the degree of wavefront distortion, and takes the intensity information obtained by the wavefront detector 7 as an indicator, and increases or decreases the spatial resolution of the wavefront detector 7 by moving the spatial resolution adjustment platform 9 back and forth, and maximizes the spatial resolution of the wavefront detector 7 while ensuring that the signal-to-noise ratio of the wavefront detector 7 spot is greater than the specified target N, where N is a real number greater than 1; the active deformable secondary mirror support frame 3 is used to support the deformable secondary mirror 2 to achieve the overall angle, translation and front and back position adjustment of the deformable secondary mirror 2; the driver 12 drives the active components of the deformable secondary mirror 2 and the active deformable secondary mirror support frame 3; the control computer 11 realizes feedback control of the deformable secondary mirror 2 and the active deformable secondary mirror support frame 3 according to the wavefront distribution information obtained by the variable resolution Hartmann sensor and the imaging information of the imaging detector 10.

[0022] The deformable secondary mirror 2 uses piezoelectric or magnetostrictive materials or a voice coil motor to drive the mirror surface to deform. The deformable secondary mirror 2 can use a convex mirror or a concave mirror.

[0023] The active deformable secondary mirror support frame 3 adopts a six-axis parallel platform or a piezoelectric inertial six-axis positioning platform.

[0024] The beam splitter prism 4 is implemented by using intensity splitting, spectrum splitting or polarization splitting devices.

[0025] The wavefront detector 7 and the imaging detector 10 are charge coupled devices (CCD) or complementary metal oxide semiconductor (CMOS) detectors.

[0026] The control computer 11 may be a high-performance desktop computer or an embedded computing platform.

[0027] The feedback control process adopts a proportional-integral control method, and the calculation method of the voltage from the wavefront to the piezoelectric driver of the deformable secondary mirror adopts a mode or direct slope recovery algorithm.

[0028] The working process of the variable resolution Hartmann-based adaptive optical telescope wavefront control device of the present invention is divided into three steps. The first step is to adjust the system state, that is, to minimize the system imaging aberration by adjusting the position of the active deformable secondary mirror support frame 3, so as to prepare for the next step of realizing real-time wavefront aberration control.

[0029] The second step is to adjust the optimal control state. According to the light energy distribution detected by the wavefront sensor 7, the spatial resolution adjustment platform 9 is controlled so that the light spot detected by the wavefront sensor 7 has a sufficient signal-to-noise ratio, thereby achieving the effect of optimizing wavefront detection and control.

[0030] Finally, real-time closed-loop control is performed to control the deformable secondary mirror 2 in real time to perform wavefront control according to the wavefront phase difference detected by the wavefront sensor 7, and the imaging detector 10 is controlled by the control computer 11 to obtain a clear and stable target image sequence.

[0031] System status adjustment: Figure 1 As shown, a star or artificial target with higher brightness is selected, and the light within the field of view is converged to the deformable secondary mirror 2 through the reflective primary mirror 1, and then passes through the deformable secondary mirror 2 and the beam splitter prism 4, and then enters the wavefront detector 7 through the field of view aperture 5 and the microlens array 6 in sequence. The wavefront detector 7 obtains the spot array image, and uses the centroid algorithm to obtain the offset of the single sub-aperture spot from the ideal spot position, and uses the offset of all array spots and the pattern wavefront restoration algorithm to calculate the wavefront distribution of the current incident phase difference. According to the measured phase difference distribution, the random active deformable secondary mirror support frame 3 is adjusted, and the adjustment direction of the wavefront distribution decreases is retained until there is no obvious improvement in the wavefront distribution.

[0032] Optimal control state adjustment: point the telescope to the observation target, and obtain the spot distribution of the target object on the wavefront detector 7 in the same system state adjustment process. According to the spot distribution intensity on the detector 7, if the spot is weak, change the spatial resolution adjustment platform 9 to reduce the number of spot arrays and increase the spot intensity so that the spot signal-to-noise ratio (signal peak to noise variance) reaches more than 3; otherwise, increase the number of spot arrays to maximize the wavefront detection resolution.

[0033] Real-time closed-loop control: Keep the telescope pointed at the target, obtain the wavefront information of the atmosphere and the system in real time through the variable-resolution wavefront detector, calculate the voltage required for all drivers of the deformable secondary mirror 2 according to the direct slope closed-loop control algorithm, and use the proportional-integral feedback control algorithm to achieve real-time control of the wavefront. At the same time, control the imaging detector to record the imaging effect of the target object.

[0034] This implementation case is for the case where the incident wavefront to be measured is a parallel wavefront. If the wavefront to be measured is a spherical wavefront, the beam divergence system 1 can be omitted during the measurement process, and the other steps are consistent with this implementation case.

Claims

1. A variable resolution Hartmann based adaptive optical telescope wavefront control device, characterized in that: The device comprises a reflective primary mirror (1), a deformable secondary mirror (2), an active deformable secondary mirror support frame (3), a beam splitter prism (4), a field diaphragm (5), a microlens array (6), a wavefront detector (7), a fine-tuning translation stage (8), a spatial resolution adjustment translation stage (9), an imaging detector (10), a control computer (11) and a driver (12). The optical path of the device has the following working process: the incident light from the field of view of the telescope is reflected by the reflective primary mirror (1) and reaches the deformable secondary mirror (2). After the wavefront information of the deformable secondary mirror (2) is regulated, the transmitted light enters the variable resolution Hartmann sensor after passing through the beam splitter prism (4) and the field diaphragm (5), and the reflected light enters the imaging detector (10). The variable resolution Hartmann sensor is composed of a microlens array (6), a wavefront detector (7), a fine-tuning translation stage (8) and a spatial resolution adjustment platform (9). The variable resolution Hartmann sensor adjusts the spatial resolution of the image according to the intensity of the incident light beam and the The wavefront distortion degree control fine-tuning translation stage (8) and the spatial resolution adjustment platform (9) use the intensity information obtained by the wavefront detector (7) as an indicator, and increase or decrease the spatial resolution of the wavefront detector (7) by moving the spatial resolution adjustment platform (9) forward and backward, so as to maximize the spatial resolution of the wavefront detector (7) while ensuring that the spot signal-to-noise ratio of the wavefront detector (7) is greater than a specified target N, where N is a real number greater than 1; the active deformable secondary mirror support frame (3) is used to support the deformable secondary mirror (2) to achieve overall angle, translation and front and rear position adjustment of the deformable secondary mirror (2); the driver (12) drives the active components of the deformable secondary mirror (2) and the active deformable secondary mirror support frame (3); the control computer (11) implements feedback control of the deformable secondary mirror (2) and the active deformable secondary mirror support frame (3) based on the wavefront distribution information obtained by the variable resolution Hartmann sensor and the imaging information of the imaging detector (10); System status adjustment: Select a brighter star or artificial target. The light within the field of view is converged by the reflective primary mirror (1) to the deformable secondary mirror (2). After passing through the deformable secondary mirror (2) and the beam splitter (4), it enters the wavefront detector (7) through the field of view aperture (5) and the microlens array (6). The wavefront detector (7) obtains the spot array image and uses the centroid algorithm to obtain the offset of a single sub-aperture spot from the ideal spot position. The offset of all array spots is used and the wavefront distribution of the current incident phase difference is calculated according to the pattern wavefront restoration algorithm. The randomly active deformable secondary mirror support frame (3) is adjusted according to the measured phase difference distribution, and the adjustment direction of the wavefront distribution decrease is retained until there is no obvious improvement in the wavefront distribution; Optimal control state adjustment: the telescope is pointed at the observation target, and the light spot distribution of the target object on the wavefront detector (7) is obtained in the same system state adjustment process. According to the light spot distribution intensity on the detector (7), if the light spot is weak, the spatial resolution adjustment platform (9) is changed to reduce the number of light spot arrays and increase the light spot intensity so that the light spot signal-to-noise ratio reaches more than 3; otherwise, the number of light spot arrays is increased to maximize the wavefront detection resolution; Real-time closed-loop control: Keep the telescope pointed at the target, obtain the wavefront information of the atmosphere and the system in real time through the variable-resolution wavefront detector, and calculate the voltage required for all drivers of the deformable secondary mirror (2) according to the direct slope closed-loop control algorithm. Use the proportional-integral feedback control algorithm to achieve real-time control of the wavefront. At the same time, control the imaging detector to record the imaging effect of the target object.

2. The variable resolution Hartmann-based adaptive optical telescope wavefront control device according to claim 1, characterized in that: The deformable secondary mirror (2) uses piezoelectric or magnetostrictive materials or a voice coil motor to drive the mirror surface to deform. The deformable secondary mirror (2) can be a convex or concave mirror.

3. The variable resolution Hartmann-based adaptive optical telescope wavefront control device according to claim 1, characterized in that: The active deformable secondary mirror support frame (3) adopts a six-axis parallel platform or a piezoelectric inertial six-axis positioning platform.

4. The variable resolution Hartmann based adaptive optical telescope wavefront control device according to claim 1, characterized in that: The beam splitting prism (4) is implemented by using an intensity beam splitting, a spectrum beam splitting or a polarization beam splitting device.

5. The variable resolution Hartmann based adaptive optical telescope wavefront control device according to claim 1, characterized in that: The wavefront detector (7) and the imaging detector (10) are charge coupled devices (CCD) or complementary metal oxide semiconductor (CMOS) detectors.

6. The variable resolution Hartmann based adaptive optical telescope wavefront control device according to claim 1, characterized in that: The control computer (11) can be a high-performance desktop computer or an embedded computing platform.

7. The variable resolution Hartmann based adaptive optical telescope wavefront control device according to claim 1, characterized in that: The feedback control process adopts a proportional-integral control method, and the calculation method of the voltage from the wavefront to the piezoelectric driver of the deformable secondary mirror adopts a mode or direct slope recovery algorithm.

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