Static rapid detection method for co-phase error of synthetic aperture telescope

Abstract

The invention discloses a common-phase error static rapid detection method for a synthetic aperture telescope, and belongs to the field of optical imaging telescopes. According to the method, a laser is used as a point target light source, the light source is received by a synthetic aperture telescope system through a beam expander, a convergent light beam passing through a telescope is collimated and then equivalently and uniformly divided into a plurality of light paths, specific phase delay is applied to light beams transmitted by the same sub-aperture (hereinafter referred to as a reference aperture) in each light path, and the light beams are transmitted through the synthetic aperture telescope system. And finally, converging the light beams to a detector through respective imaging lenses, calculating point spread function distribution of point targets which are simultaneously collected by each light path and pass through the synthetic aperture telescope system, and solving to obtain a co-phase error of each sub-aperture of the synthetic aperture telescope system relative to a reference aperture. According to the method, the common-phase error static rapid detection of the synthetic aperture telescope system can be realized without changing the state of the primary mirror and time-sharing modulation, and the practical value is relatively high.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical imaging telescopes, and particularly relates to a method for static and rapid detection of the common phase error of a synthetic aperture telescope. Background Art

[0002] According to the diffraction limit formula, under the condition of a fixed observation wavelength, the main factor restricting the resolution of a telescope is the aperture of the telescope. The larger the telescope aperture, the stronger the light-gathering ability and the more details that can be resolved. With the increase of human observation requirements, the telescope aperture has also increased, but the preparation of the primary mirror of an ultra-large aperture telescope has become a new problem. On the one hand, the existing technical level of humans cannot meet the requirements for the development of large aperture primary mirrors, and the research progress of new technologies is slow; on the other hand, the cost of manufacturing ultra-large aperture telescopes is relatively high. For this reason, some scholars have proposed synthetic aperture telescope technology, which refers to a telescope technology that uses an array of multiple independent small aperture telescopes to achieve the resolution ability equivalent to that of a large aperture telescope. The synthetic aperture telescope has the following advantages: on the one hand, the design of small aperture telescopes is less difficult, the manufacturing cost is low, and it is easy to replicate and process; on the other hand, the synthetic aperture telescope system can be folded and unfolded, meeting the requirements of the volume and weight of existing rocket payloads, and can be used in the scheme of space large aperture telescopes. In the synthetic aperture telescope system, the segmented structure brings specific common phase errors. The common phase errors can be divided into translational errors and tilt errors. The translational errors will cause the synthetic aperture system to be unable to image with high resolution due to the different optical paths of the light beams transmitted between sub-apertures, and the tilt errors will cause the imaging of the synthetic aperture system to deviate and thus affect the imaging quality due to the included angle between the light beams transmitted between sub-apertures. Therefore, the detection and correction of common phase errors are of great significance for the synthetic aperture telescope system to achieve high-resolution imaging.

[0003] There are some limitations in the existing synthetic aperture common phase error detection methods: some need to transform the primary mirror of the synthetic aperture telescope (such as installing electronic sensors) to monitor the position information of the primary mirror in real time, and the common phase error detection of a high duty cycle system cannot be achieved; some need to rely on specific devices (such as Hartmann sensors, dispersion fringe sensors, etc.) to complete the common phase error detection, and real-time detection cannot be achieved. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for static and rapid detection of the common phase error of a synthetic aperture telescope, which can realize the static and rapid detection of the common phase error of the synthetic aperture telescope system without changing the state of the primary mirror and without time-sharing modulation, and has high practical value.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect, the present invention proposes a method for static and rapid detection of the common phase error of a synthetic aperture telescope, and the method includes:

[0007] Set the wavelength of the laser to , set the number of apertures of the synthetic aperture telescope system to N, and select one of the apertures as the reference aperture;

[0008] After being expanded by an expander, the laser enters the synthetic aperture telescope system. The imaging beam of the synthetic aperture telescope system is collimated by a collimator and then sent to a reflector, and then the beam is evenly divided into M paths of beams by a beam splitter;

[0009] In each path of the beam, a phase delay is added to the beam transmitted by the reference aperture by using a phase delay device;

[0010] Each path of the beam after adding the phase delay is converged to a detector by an imaging lens;

[0011] Obtain the point spread function of the laser point target collected by the detector, and perform Fourier transform to obtain the corresponding optical transfer function of the synthetic aperture telescope system;

[0012] Multiply the optical transfer function by the corresponding delayed phase and linearly superpose them to obtain the common phase error of each sub-aperture of the synthetic aperture telescope system relative to the reference aperture.

[0013] In a second aspect, the present invention provides an electronic device, including: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the foregoing method for static and fast detection of the common phase error of a synthetic aperture telescope.

[0014] In a third aspect, the present invention provides a computer-readable storage medium, on which executable instructions are stored, and when the instructions are executed by a processor, the processor can implement the foregoing method for static and fast detection of the common phase error of a synthetic aperture telescope.

[0015] The beneficial effects of the present invention are as follows:

[0016] This method does not require the installation of complex common phase error detection sensors, and can complete detection by using a beam splitter, a wave plate, a camera, etc. in the imaging optical path, and is applicable to synthetic aperture telescope systems with a high duty cycle;

[0017] This method does not require time-sharing modulation, and can realize real-time detection of the common phase error of all sub-apertures of the synthetic aperture telescope system, and is applicable to the detection of fast moving targets. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of an implementation of a method for static and fast detection of the common phase error of a synthetic aperture telescope according to the present invention.

[0019] Among them, 1 is a laser, 2 is a beam expander, 3 is a synthetic aperture telescope system, 4 is a collimator, 5 is a reflector, 6 is a beam splitter, 7 is a phase delay device, 8 is an imaging lens, and 9 is a detector. Specific embodiments

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0021] As Figure 1 shown, the present invention provides a method for static fast detection of the common phase error of a synthetic aperture telescope, including:

[0022] Assume that the wavelength of the laser 1 is , the number of apertures of the synthetic aperture telescope system is N, the radius of each sub-aperture is R, and its pupil function can be expressed as: , where x, y represent the spatial coordinates on the spliced primary mirror. Select one of the apertures as the reference aperture, denoted by .

[0023] The laser 1 is expanded by the beam expander 2 and then enters the synthetic aperture telescope system 3. The imaging beam of the synthetic aperture telescope system 3 is collimated by the collimator 4 and then sent to the reflector 5, and then the beam is evenly divided into M paths of beams by the beam splitter 6;

[0024] In each path of the beam, a specific phase delay is added to the beam transmitted to the reference aperture by the phase delay device 7. Among them, the reference aperture phase delay of the m-th path of the beam is:

[0025] (1)

[0026] Each path of the beam is finally converged by the imaging lens 8 onto a detector 9, and the M paths of the beam correspond to M detectors. Among them, the point spread function collected by the m-th detector for the laser point target after passing through the synthetic aperture telescope system is:

[0027] (2)

[0028] Through Fourier transform, the corresponding optical transfer function of the synthetic aperture telescope system is obtained as:

[0029] (3) In the formula, represents the optical transfer function of the synthetic aperture telescope system corresponding to the m-th detector;

[0030] Multiply the above optical transfer function of the synthetic aperture telescope system by the corresponding delayed phase and linearly superimpose them to obtain expression C:

[0031] (4)

[0032] Among them, represents the central coordinates of the nth sub-aperture, is the pupil function of the reference aperture, is the pupil function of the remaining apertures, represents convolution, is the wavefront distribution of the nth sub-aperture of the synthetic aperture telescope system. i represents the imaginary unit, and N represents the total number of sub-apertures.

[0033] C contains both the phase information and position information of each sub-aperture. The phase information is reflected in its complex exponential term. The common phase error can be solved using the following formula:

[0034] (5)

[0035] Among them, Im[ ] and Re[ ] respectively represent taking the imaginary part and real part of a complex number.

[0036] So far, the common phase error wavefront distribution of each sub-aperture of the synthetic aperture telescope system relative to the reference aperture has been obtained .

[0037] According to the wavefront distribution of the sub-apertures, the attitude misalignment of each sub-aperture can be deduced. This process is specifically reflected in that: the wavefront phase distribution of each sub-aperture of the synthetic aperture telescope contains the translation error (Piston) and tilt error (Tip / Tilt) of the sub-aperture itself in the actual splicing state. By analyzing the phase difference between the wavefront of each sub-aperture and the reference aperture, the corresponding linear (tilt) and constant (translation) terms are extracted, so as to quantitatively deduce the attitude misalignment degree of the sub-aperture.

[0038] Furthermore, use the collimator 4 to collimate the imaging beam of the synthetic aperture telescope system 3, and then evenly divide the beam into M paths through the beam splitter 6. M can be selected as 3 paths, or 4 paths or more beam path numbers, but the complexity of the beam splitting optical path and the detection accuracy of the common phase error need to be considered simultaneously;

[0039] Furthermore, in each beam path, a specific phase delay is added to the beam transmitted to the same sub-aperture. That is, first split the beam, and then delay it.

[0040] Furthermore, a specific phase delay is added to the beam transmitted to the same sub-aperture (reference aperture). The phase delay amounts of the reference apertures in different beam paths are (0, 2π / M,..., (M - 1)2π / M);

[0041] Furthermore, use multiple cameras to simultaneously collect the point spread functions of the synthetic aperture telescope system 3 under different phase delays of multiple beam paths, and then calculate the actual common phase error of each sub-mirror of the synthetic aperture telescope system.

[0042] Furthermore, the synthetic aperture telescope can be an array of synthetic aperture telescopes or a segmented primary mirror telescope in terms of structure, and can be made of glass or polyimide in terms of material. In terms of imaging method, it can be a transmissive mirror or a reflective mirror.

[0043] Furthermore, the phase delay device 7 can be a device with a fixed phase type such as a wave plate, or a device with a variable phase type such as a reflective liquid crystal spatial light modulator or a transmissive liquid crystal phase retarder, or can also be a displacement stage such as a fast steering mirror.

[0044] Furthermore, the detector 9 can be a CCD camera, or a CMOS camera, or other area array detectors that meet the conditions.

[0045] Embodiment

[0046] The object measured in this implementation scheme is a 4-hole synthetic aperture telescope system. A laser with a wavelength of 650 nm is used as the light source, and a wave plate is used as the phase delay device. The specific implementation steps are as follows:

[0047] Set the wavelength of the laser to 650 nm and set the aperture number of the synthetic aperture telescope system to 4;

[0048] The laser enters the synthetic aperture telescope system after beam expansion. A collimating mirror is used to collimate the imaging beam of the synthetic aperture telescope system, and then the beam is evenly divided into 3 beams by a beam splitter;

[0049] Among the 3 beams, a specific wave plate is added to the beam transmitted to the No. 1 sub-aperture. The phase delays generated by the 3 wave plates are (0, π / 3, 2π / 3) respectively;

[0050] The 3 beams are finally imaged on 3 CCD cameras at the same time. The point spread functions collected by the 3 CCD cameras are respectively: (PSF 1 , PSF 2 , PSF 3 ). Through Fourier transform, the corresponding optical transfer functions of the synthetic aperture telescope system are respectively (OTF 1 , OTF 2 , OTF 3 ):

[0051] Multiply the optical transfer functions of the above synthetic aperture telescope system by the corresponding delay phases and linearly superimpose them to obtain expression C, and then calculate the co-phase error of the remaining 3 sub-apertures of the synthetic aperture telescope system relative to the No. 1 sub-aperture according to formula (5).

[0052] The present invention divides the modulation optical path into three paths to achieve static common-phase error detection, with higher real-time performance. Compared with the multi-step modulation phase shifters in the prior art, the present invention uses a beam splitter and a static phase retarder to apply a delay phase to the reference aperture optical path; it can achieve static and real-time common-phase error detection, and can reduce the impact of dynamic modulation on detection.

[0053] Compared with the solution in the prior art that uses a multi-step phase shifter to modulate different phases at different times and requires at least three or more modulation operations to complete a common-phase error measurement, the present invention adopts a static optical path design. The input beam is directly statically divided into three paths by a beam splitter, and a fixed phase delay is applied to the reference aperture in each optical path; the three optical paths correspond to three different phase delay states, and a set of point spread functions (PSFs) with different phase states can be obtained simultaneously in one imaging, so as to directly and statically calculate the common-phase error; without the movement of dynamic modulation devices, the introduction of movement errors and the time consumption of the modulation process are completely avoided; the measurement real-time performance reaches the millisecond level, significantly improving the detection performance.

[0054] In a second aspect, the present invention provides an electronic device, including: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the foregoing method for static and fast detection of common-phase error of a synthetic aperture telescope.

[0055] In a third aspect, the present invention provides a computer-readable storage medium, on which executable instructions are stored, and when the instructions are executed by a processor, the processor can implement the foregoing method for static and fast detection of common-phase error of a synthetic aperture telescope.

[0056] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A static fast detection method for common phase error of synthetic aperture telescope, characterized in that: The method comprises: Set the laser wavelength to , set the number of apertures of the synthetic aperture telescope system to N, and select one of the apertures as the reference aperture; The laser enters the synthetic aperture telescope system after being expanded by a beam expander. The imaging beam of the synthetic aperture telescope system is collimated by a collimator and sent to a reflector. The beam is then evenly divided into M beams by a beam splitter. In each beam, a phase delay device is used to add a phase delay to the beam transmitted by the reference aperture; Each beam after adding phase delay is converged onto the detector by the imaging lens; Obtain the point spread function of the laser point target collected by the detector, perform Fourier transform, and obtain the corresponding optical transfer function of the synthetic aperture telescope system; The optical transfer functions are multiplied by the corresponding delay phases and linearly superimposed to obtain the common phase errors of each sub-aperture of the synthetic aperture telescope system relative to the reference aperture.

2. The method for static fast detection of common phase error of synthetic aperture telescope according to claim 1, characterized in that: The step of adding a phase delay to the light beam transmitted by the reference aperture by using a phase delay device comprises: （1） In the formula, is the reference aperture phase delay of the mth beam.

3. The method for static fast detection of common phase error of synthetic aperture telescope according to claim 1, characterized in that: The point spread function of the laser point target collected by the detector is: （2） In the formula, It represents the point spread function of the laser point target collected by the mth detector after passing through the synthetic aperture telescope system, and M light beams correspond to M detectors.

4. The method for static fast detection of common phase error of synthetic aperture telescope according to claim 1, characterized in that: The Fourier transform is performed to obtain the corresponding optical transfer function of the synthetic aperture telescope system: （3） In the formula, represents the optical transfer function of the synthetic aperture telescope system corresponding to the mth detector; The optical transfer function of the synthetic aperture telescope system is multiplied by the corresponding delay phase and linearly superposed to obtain the expression C: （4） in, represents the spatial coordinates on the spliced ​​primary mirror, represents the center coordinate of the nth subaperture, is the pupil function of the reference aperture, is the pupil function of the remaining apertures, represents convolution, is the wavefront distribution of the nth subaperture of the synthetic aperture telescope system, i represents the imaginary unit, and N represents the total number of subapertures.

5. The method for static fast detection of common phase error of synthetic aperture telescope according to claim 4, characterized in that: The wavefront distribution of the subaperture for: （5） Among them, Im[ ] and Re[ ] represent the imaginary part and real part of the complex number respectively; According to the wavefront distribution of the sub-aperture, the attitude misalignment of each sub-aperture is estimated.

6. The method for static fast detection of common phase error of synthetic aperture telescope according to claim 1, characterized in that: The synthetic aperture telescope is divided into a synthetic aperture telescope array or a spliced ​​primary mirror telescope according to its structure, is divided into glass or polyimide according to its material, and is divided into a transmission mirror or a reflection mirror according to its imaging method.

7. The method for static fast detection of common phase error of synthetic aperture telescope according to claim 1, characterized in that: The phase delay device is a fixed phase type device, a variable phase type device, or a translation stage.

8. The method for static fast detection of common phase error of synthetic aperture telescope according to claim 1, characterized in that: The detector is a CCD camera, a CMOS camera or an array detector.

9. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; Wherein, when one or more programs are executed by the one or more processors, the one or more processors implement a static rapid detection method for common phase errors of a synthetic aperture telescope as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that: Executable instructions are stored thereon, and when the instructions are executed by the processor, the processor can implement a static fast detection method for common phase errors of a synthetic aperture telescope as described in any one of claims 1-8.

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