CN115079370A - Pupil offset correction method for large-aperture self-adaptive telescope - Google Patents
Pupil offset correction method for large-aperture self-adaptive telescope Download PDFInfo
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- CN115079370A CN115079370A CN202210809076.3A CN202210809076A CN115079370A CN 115079370 A CN115079370 A CN 115079370A CN 202210809076 A CN202210809076 A CN 202210809076A CN 115079370 A CN115079370 A CN 115079370A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
- G02B7/182—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors
- G02B7/1822—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors comprising means for aligning the optical axis
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
- G02B23/02—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices involving prisms or mirrors
- G02B23/06—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices involving prisms or mirrors having a focussing action, e.g. parabolic mirror
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
- G02B23/16—Housings; Caps; Mountings; Supports, e.g. with counterweight
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/62—Optical apparatus specially adapted for adjusting optical elements during the assembly of optical systems
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Abstract
The invention relates to the technical field of telescope adjustment, in particular to a pupil offset correction method of a large-aperture self-adaptive telescope, which can correct pupil offset of a large-sized foundation self-adaptive telescope, ensures that an optical axis of a main optical system of a telescope system is superposed with an optical axis of an under-machine self-adaptive correction platform, creatively provides alignment of the optical axis of the main optical system and the optical axis of the under-machine self-adaptive correction platform based on a secondary mirror coma-free point, ensures system wave fronts of the main mirror and the secondary mirror while changing the optical axis of the main optical system, eliminates optical axis change caused by deflection of the telescope, and can enable the self-adaptive correction effect of the telescope to reach the best state. The method and the device perform real-time compensation and correction on the optical axis deviation of the system, and improve the correction effect of the self-adaptive system.
Description
Technical Field
The invention relates to the technical field of telescope adjustment, in particular to a pupil offset correction method for a large-aperture self-adaptive telescope.
Background
Along with the increasing of the aperture of a foundation telescope, the weight of a truss of a clamping type main optical system is increased continuously, the rear intercept of the main optical system is increased continuously, the problem of imaging quality reduction caused by maladjustment errors caused by structure and temperature changes is more and more obvious, especially the influence on a self-adaptive high-resolution imaging system is more and more serious, and a compensation mode of the maladjustment errors becomes a research focus and a difficulty of the foundation large-aperture telescope. Taking a classical card-type primary and secondary mirror system as an example, the misalignment error of the optical system is mainly that the relative position of the primary and secondary mirrors changes along with the gravity deflection of the change of the pitch angle and the temperature change, which causes the optical axis of the system to shift, and the pupil position of the system shifts after the secondary mirror is folded to an under-machine imaging system through the Kude optical system. For the self-adaptive imaging optical system, the Hartmann measuring system and the deformable mirror system are respectively arranged at the pupil position of the main mirror, wherein the deformable mirror is the exit pupil of the main mirror, and the Hartmann detector is the exit pupil of the deformable mirror. The pupil shift causes the mapping surface of the main mirror to perform circling motion on the optical surface of the deformable mirror, and as the aperture of the main mirror is increased and the rear intercept of the system is lengthened, the circling motion influence is increasingly enhanced, the correction effect of the self-adaptive high-resolution imaging system is seriously influenced, and the imaging quality is influenced.
The misadjustment error is a main factor influencing the imaging performance of the large-caliber self-adaptive telescope. In the aspect of misalignment error correction of a telescope, an active optics-based misalignment error correction method is firstly used on an NTT telescope by an European southern astronomical telescope, a wavefront sensor is used for monitoring a wavefront function of the whole system and decomposing the wavefront function into the relative offset of a main optical system, the offset error correction of the main optical system is realized by taking the relative offset as feedback, wherein the VLT telescope adopts three relatively independent adjusting mechanisms to realize misalignment error compensation aiming at defocusing, eccentricity and inclination respectively, and the MMT telescope adopts a deformable mirror to perform misalignment error compensation. In China, the galloping and the like utilize a vector wave aberration theory to establish the relationship between the systematic maladjustment error and the wavefront zenike aberration coefficient, and the secondary mirror position error is reversely calculated through the measurement of the aberration coefficient to realize the correction of the maladjustment error.
In principle, the position deviation of the secondary mirror causes defocusing and coma aberration of the system, the secondary mirror can be compensated and corrected easily through a Hexapod platform of a five-dimensional adjusting mechanism of the secondary mirror, the compensation and correction mode cannot correct the change of the optical axis of the main optical system from the angle of the system, the standard of the Kude optical path is that the optical axis after three mirrors of the main optical system are folded is superposed with a pitching axis, the optical axis after six mirrors are folded is superposed with an azimuth axis, and the influence of the deviation of the optical axis on pupil deviation still exists and influences the correction effect of the self-adaptive high-resolution imaging system.
For the small-caliber self-adaptive telescope, the main mirror, namely the secondary mirror supporting system is light in weight, and the rear intercept (Kudet optical path length) of the main optical system is short due to the limited light-passing caliber of the main mirror, so that a large pupil offset phenomenon cannot be caused. For a telescope system with the aperture reaching 4 meters, the rear intercept of a main optical system reaches 56m, the length of a curde optical path is increased, the influence of circle-drawing motion is increasingly enhanced, the correction effect of the self-adaptive high-resolution imaging system is seriously influenced, and the imaging quality is influenced.
The 4m telescope system developed by Changchun optical machine is domestic largest caliber foundation high resolution telescope, the pupil shift phenomenon of the domestic built large caliber self-adaptive telescope is not obvious such as Chengdu optical station 1.8m self-adaptive telescope and Changchun optical station 2m telescope, although the pupil circle drawing problem can occur in the adjusting process, the pupil misalignment problem can be solved by adjusting the positions of the three mirrors in the adjusting process of the telescope to ensure that the light beam refracted by the three mirrors is completely coincident with the pitch axis. The method is feasible for telescopes with the aperture of less than 2m, but for telescopes with the aperture of 4m magnitude, the change of an optical axis caused by a telescope deflection effect is inevitably brought along with the change of pointing direction in the tracking process of the telescope, so that a method for correcting pupil shift of the telescope with 4m magnitude is still to be further developed.
Disclosure of Invention
The embodiment of the invention provides a pupil offset correction method for a large-aperture self-adaptive telescope, which at least solves the technical problem of pupil offset of the existing telescope.
According to an embodiment of the invention, a pupil offset correction method for a large-aperture adaptive telescope is provided, which comprises the following steps:
s100: building a telescope system to enable the telescope system to have a fixed star shooting condition; the method comprises the following steps that the shooting fixed star adjustment at least comprises the step of ensuring that the optical axis of a main optical system of a telescope system is overlapped with the optical axis of an under-machine self-adaptive correction platform when the telescope rotates in the direction of the telescope under the condition that the pitching angle of the telescope is not changed;
s200: under the condition of ensuring that the azimuth angle of the telescope is not changed, measuring the change of the optical axis of the telescope according to the fine tracking in an imaging platform of the telescope system and a Hartmann detector by rotating the pitch angle of the telescope, adjusting a secondary mirror of the telescope system to rotate around a coma-free point according to measured data, and eliminating the change of the optical axis caused by the deflection of the telescope on the premise of ensuring that the wavefront of a primary optical system of the telescope system is not changed;
s300: tracking a satellite target through the telescope, tracking the satellite target by the under-machine self-adaptive correction platform in a closed loop and correcting the satellite target in real time, verifying whether pupil offset correction of the telescope is finished or not through the number of effective sub-apertures in the Hartmann detector, and repeating the steps S100 and S200 until the pupil offset correction is finished if the pupil offset correction still exists.
Further, a telescope system is built to enable the telescope system to have a fixed star shooting condition; wherein, shoot the fixed star and adjust at least including guaranteeing under the unchangeable condition of the every single move angle of telescope, guarantee when telescope azimuth rotates, the main optical system optical axis of telescope system specifically does with the self-adaptation under the machine and corrects platform optical axis coincidence:
s101: the telescope system has a star shooting condition, the pitch angle of the telescope is guaranteed to be unchanged, a fixed star with the brightness meeting a preset condition is shot according to four directions of south, east, west and north, if the fixed star is not located at the same position of the target surface of the fine tracking detector in the under-machine self-adaptive correction platform, the track in the Hartmann detector is a complete circle in the four directions due to the fact that the telescope direction is rotated by 360 degrees in the star shooting process, the central position of the track is obtained through data analysis, the fixed star shot in the north direction is adjusted to the central position of the fine tracking detector through two reflectors in the under-machine self-adaptive correction platform, and the star point image collected by the Hartmann detector is guaranteed to be concentric with the drawn grid;
s102: the pitch angle of the telescope is guaranteed to be unchanged, and a fixed star with the brightness meeting preset conditions is shot according to four directions of south, east, west and north; after the adjustment, the fixed star image is positioned at the same position of the target surface of the fine tracking detector, and the circle drawing phenomenon in the Hartmann detector is observed at the moment; the telescope is rotated by 360 degrees in azimuth in the process of shooting the star, so that the track in the Hartmann detector in four azimuths is a complete circle, and the central position of the track is obtained through data analysis; adjusting the central position of a track in the Hartmann detector to the center of a Hartmann detector grid by adjusting the translation and inclination values of the three mirrors, and at the moment, drawing circles around the central positions of respective detectors for the fixed star images in the fine tracking detector and the Hartmann detector;
s103: repeating the step S101: the fixed star shot in the north direction is adjusted to the central position of the fine tracking detector and the star point image collected by the Hartmann detector is ensured to be concentric with the drawn grid through adjusting the two reflectors in the under-machine self-adaptive correction platform, and at the moment, the superposition of the optical axis of the main optical system and the optical axis of the under-machine self-adaptive correction platform is completed.
Further, the constant pitch angle of the telescope is ensured as follows:
the telescope pitch angle is ensured to be unchanged by 45 degrees.
Further, guaranteeing under the unchangeable circumstances of telescope azimuth angle, through the every single move angle that rotates the telescope, according to the imaging platform of telescope system in the fine tracking measure with the change of hartmann's detector telescope optical axis, according to actual measurement's measured data, the secondary mirror of adjustment telescope system rotates round no coma point, under the unchangeable prerequisite of assurance primary optical system wave front, the optical axis change that eliminates the deflection of telescope and arouse specifically does:
ensuring that the azimuth angle of the telescope is unchanged, enabling the pitch angle to be in a range from 0 degree to 90 degrees, and shooting each pair of fixed stars meeting preset conditions at intervals of a preset adjusting angle; the target surface of the fine tracking detector is not in the same position due to the deflection of the telescope, and the track of the fixed star image on the fine tracking detector under different pitch angles is in a quarter circle shape due to the fact that the telescope rotates to pitch for 90 degrees in the process of shooting the star, and the central position of the track is obtained through data analysis;
and adjusting the secondary mirror of the telescope system to rotate around the coma-free point, under the premise of ensuring that the wavefront of the main optical system is unchanged, adjusting the fixed star image in the fine tracking detector under each pitch angle to the central position in the fine tracking detector after the step S103 is finished, and eliminating the optical axis change caused by telescope deflection.
Further, the preset adjustment angle is 15 degrees.
Further, the primary mirror of the telescope system is a primary mirror of silicon carbide material.
Furthermore, the surface type precision of the primary mirror is ensured by adopting an active supporting mode.
Furthermore, the high-precision constant of the position of the primary mirror is realized in a mode of regulating and controlling a hydraulic support system, so that the optical axis of the primary mirror is kept unchanged.
Furthermore, the telescope system is provided with a supporting structure for supporting the secondary mirror, and five-dimensional posture adjustment of the secondary mirror and the supporting structure is realized in a six-axis platform mode so as to compensate position deviation and optical axis deviation of the main optical system caused by gravity and temperature change.
Furthermore, the circle drawing condition of the Hartmann camera of the telescope system is eliminated by adjusting the three-mirror translation and inclination modes, so that the optical axis of the main optical system of the telescope system is coincident with the optical axis of the under-machine self-adaptive correction platform when the telescope rotates in the azimuth direction.
The pupil offset correction method of the large-aperture self-adaptive telescope in the embodiment of the invention can correct pupil offset of a large-size foundation self-adaptive telescope, ensures that the optical axis of a main optical system of a telescope system is superposed with the optical axis of an under-machine self-adaptive correction platform, creatively provides alignment between the optical axis of the main optical system and the optical axis of the under-machine self-adaptive correction platform based on the coma-free point of a secondary mirror, ensures system wavefront of the main mirror and the secondary mirror while changing the optical axis of the main optical system, eliminates optical axis change caused by deflection of the telescope, and can enable the self-adaptive correction effect of the telescope to reach the best state. The method and the device perform real-time compensation and correction on the optical axis deviation of the system, and improve the correction effect of the self-adaptive system.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a flow chart of the pupil shift correction method of a large-aperture adaptive telescope according to the present invention;
FIG. 2 is a diagram of an overall implementation of a pupil shift correction procedure according to the present invention;
FIG. 3 is a schematic diagram of a 4 m-stage ground-based telescope system according to the present invention;
FIG. 4 is a schematic view of a main optical system of the present invention;
FIG. 5 is a star point image acquired by the Hartmann detector of the present invention.
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.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those 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.
In order to realize the compensation of the primary mirror and secondary mirror maladjustment errors and the compensation of the optical axis variation, after the correction is finished based on the telescope pointing error, the optical axis offset of the system is compensated in real time based on the Hartmann detector main optical system optical axis calibration method and the pupil offset compensation technology, so that the correction effect of the self-adaptive system is improved. Based on the defects of the prior art, the invention carries out real-time compensation on the optical axis offset of the system based on the Hartmann detector main optical system optical axis calibration method and the pupil offset compensation technology, thereby improving the correction effect of the self-adaptive system. First, the cause of the optical axis shift of the main optical system will be described in detail. Then, an optical axis calibration and compensation process is briefly introduced, and based on a card system primary mirror and secondary mirror zero-coma-point theory, a method for calibrating and compensating the optical axis of the double detectors of the Hartmann camera and the calibration camera is provided on the basis. And thirdly, adjusting the telescope by taking the calibration data as a reference to eliminate the pupil shift phenomenon. And finally, verifying the effectiveness of the correction method provided by the text by the number of effective sub-aperture points of the Hartmann detector in the actual correction process of the under-machine self-adaptive high-resolution imaging system.
Referring to fig. 3 and 4, the present invention corrects the pupil shift generated by a 4 m-caliber ground-based large-caliber adaptive telescope, so the specific structure of the telescope system is described as follows in the specific embodiment:
in the embodiment, a 4m grade ground-based telescope system is schematically shown in fig. 3, the overall height is 12.5m, the width is 5.8m, and the overall mass is close to 90 tons. From the optical-mechanical structure perspective, the telescope mainly includes tracking frame, primary mirror, secondary mirror, kude system, under-machine adaptive correction platform and a plurality of imaging terminals, etc., and in order to simplify the analysis flow in this embodiment, only the first five parts are considered.
The tracking frame is a carrier of a telescope optical system, and high-precision tracking measurement of the telescope on each sky area target is realized through high-precision rotation of a pitching axis system and an azimuth axis system. The connection of the tracking frame to each optical system is shown in fig. 3.
The main mirror material is SiC, and has the advantages of specific stiffness, light weight and good thermal conductivity. The gravity deformation of the 4 m-magnitude primary mirror along with the change of pitching is serious, the ultrahigh surface accuracy of the primary mirror is ensured by adopting an active supporting mode, the high-accuracy constancy of the position of the primary mirror is realized through a hydraulic supporting system, and the optical axis of the primary mirror is kept unchanged. The secondary mirror system is connected with the telescope four-way through a truss. In addition, the secondary mirror and the supporting structure thereof adopt a high-precision Hexapod platform to realize five-dimensional attitude adjustment so as to compensate the position deviation and the optical axis deviation of the main optical system caused by gravity and temperature change.
Pupil matching of Hartmann detection is realized through detailed optical design, and calibration camera and Hartmann detection collaborative imaging are realized through spectral splitting. The Coidel system realizes the connection between the under-machine self-adaptive correction platform and the main optical system through the turning of 4 reflectors, and ensures that the focal position of the main optical system does not change along with the change of the pointing direction of the telescope. The self-adaptive system consists of a relay system, a fine tracking system, a thousand-unit deformable mirror, a Hartmann detection and high-precision imaging system, and realizes high-resolution imaging of the target by the imaging terminal.
The invention corrects the pupil offset of a ground-based large-caliber self-adaptive telescope in the observation process, and the misalignment error of the telescope in the tracking process is the main reason causing the pupil offset. Taking a classical card-type primary and secondary mirror system as an example, the misalignment error of the optical system is mainly the gravity deflection of the primary and secondary mirrors along with the change of the pitch angle and the relative position change of the primary and secondary mirrors along with the change of the temperature, which causes the optical axis of the system to shift. After the light beam is refracted to an under-machine imaging system through a Kude optical system, the precise tracking system tracks a target in a closed loop mode to realize the function of image stabilization, and along with the change of the azimuth angle and the pitch angle of the target, a certain amount of position deviation can be generated when the light beam after image stabilization irradiates a pupil plane. For the self-adaptive imaging optical imaging, the Hartmann measuring system and the deformable mirror system are respectively arranged at the pupil position of the main mirror, the pupil shift causes the mapping surface of the main mirror to perform circle-drawing motion on the optical surface of the deformable mirror, the circle-drawing motion influence is increasingly enhanced along with the increase of the aperture of the main mirror and the lengthening of the system back intercept, the correction effect of the self-adaptive high-resolution imaging system is seriously influenced, and the imaging quality is influenced. From the perspective of the telescope structure, the main causes of the telescope pupil shift include:
1) primary mirror positional deviation caused by deformation of the primary mirror support assembly: the flexible rod is adopted in the primary mirror supporting structure to reduce the temperature variation deviation of the optical material and the structural material, so that the rigidity of the primary mirror supporting structure is reduced, the primary mirror generates position deviation and angle deviation relative to the primary mirror chamber under the action of gravity, and the deviation changes along with the change of the pitch angle of the telescope. The primary mirror ensures that the absolute position deviation of the primary mirror is 0.02mm through an active support technology, and the influence on the optical axis deviation can be ignored;
2) deviation of secondary mirror caused by truss gravity deformation: as shown in fig. 3, in the height direction, the span of the truss is very large, which is close to 5.5m, and although a rod with a large diameter is used in the truss structure, since the structural loads of the ring beam, the four spars and the like are very large, which is close to 1.5 tons, the position deviation and the angle deviation of the secondary mirror occur along with the change of the gravity direction;
3) thermal deformation leads to offset errors: the change of the environmental temperature can lead to the thermal deformation of the structure, so that the primary mirror and the secondary mirror deviate from the theoretical position, the interval deviation of the primary mirror and the secondary mirror is mainly caused, the effect of the influence of the verticality deviation of the optical axis of the primary mirror relative to the four-way plane is aggravated along with the increase of the caliber of the telescope, and the interval deviation of the primary mirror and the secondary mirror can also cause the relative position deviation of the primary mirror and the secondary mirror.
Although each cause of the pupil offset change can be analyzed, the law and magnitude of the pupil offset change caused by the superposition of all the factors during the observation of the target by the telescope are quite complex. The invention provides a main optical system optical axis calibration method and a pupil offset compensation technology based on a Hartmann detector, which are used for compensating and correcting the optical axis offset of a system in real time and improving the correction effect of an adaptive system.
Referring to fig. 1 to 4, according to an embodiment of the present invention, there is provided a method for correcting pupil shift of a large-aperture adaptive telescope, including the following steps:
s100: building a telescope system to enable the telescope system to have a fixed star shooting condition; the fixed star adjustment during shooting at least comprises the step of ensuring that the optical axis of a main optical system of the telescope system coincides with the optical axis of the under-machine self-adaptive correction platform when the telescope rotates in the azimuth direction under the condition that the pitching angle of the telescope is not changed.
After the telescope is integrally built, the telescopic telescope is provided with a shooting fixed star condition, the circle drawing condition of the Hartmann camera is eliminated by adjusting the translation and the inclination of the three mirrors under the condition that the pitching angle of the telescope is unchanged, namely, when the telescope rotates in the azimuth direction, the coincidence of the optical axis of a main optical system passing through a Kude optical path and the optical axis of an under-machine adaptive correction platform is ensured. The telescope system comprises a main optical system (for collecting energy), a Kude system (for deflecting light path), and an under-machine self-adaptive correction platform (for optical imaging); the primary optical system mainly comprises a primary mirror and a secondary mirror.
Step S100 specifically includes:
s101: the telescope system has a star shooting condition, the pitch angle of the telescope is guaranteed to be unchanged, a fixed star with the brightness meeting a preset condition is shot according to four directions of south, east, west and north, if the fixed star is not in the same position of the target surface of the fine tracking detector in the under-machine self-adaptive correction platform, due to the fact that the azimuth of the telescope is rotated by 360 degrees in the star shooting process, the track in the Hartmann detector in the four directions is required to be a complete circle, the central position of the track is obtained through data analysis, the fixed star shot in the north direction is adjusted to the central position of the fine tracking detector through adjusting two reflectors in the under-machine self-adaptive correction platform, and the star point image collected by the Hartmann detector is guaranteed to be concentric with the drawn grids.
After the telescope has the condition of shooting stars, the pitch angle of the telescope is ensured to be unchanged, specifically, the pitch angle of the north star can be 45 degrees, a fixed star with proper brightness is found according to four directions of south, east, west and north (the brightness can be preset, and the fixed star with the brightness meeting the preset condition is selected), and whether the fixed stars are all located at the same position of the target surface of the fine tracking detector in the self-adaptive correction platform under the machine is judged; if the telescope is not in the same position, the track of the fine tracking detector in the four directions is a complete circle due to the fact that the telescope is rotated by 360 degrees in the process of shooting the star, and the central position of the track is obtained through data analysis; the first step of adjustment is completed by adjusting pick-up mirrors (two reflecting mirrors of which the main optical system is connected and folded with the under-machine adaptive platform after passing through the kudet optical path) in the under-machine adaptive correction platform, adjusting the polaris to the central position of the fine tracking detector and ensuring that the star point image acquired by the Hartmann detector is concentric with the drawn grid, and the star point image acquired by the Hartmann detector is as shown in figure 5.
S102: the pitch angle of the telescope is guaranteed to be unchanged, and a fixed star with the brightness meeting preset conditions is shot according to four directions of south, east, west and north; after the adjustment, the fixed star image is positioned at the same position of the target surface of the fine tracking detector, and the circle drawing phenomenon in the Hartmann detector is observed at the moment; the telescope is rotated by 360 degrees in azimuth in the process of shooting the star, so that the track in the Hartmann detector in four azimuths is a complete circle, and the central position of the track is obtained through data analysis; and adjusting the central position of the track in the Hartmann detector to the center of the grid of the Hartmann detector by adjusting the translation and inclination values of the three mirrors, and at the moment, the fixed star images in the fine tracking detector and the Hartmann detector draw circles around the central positions of the respective detectors.
Ensuring that the pitch angle of the telescope is unchanged (the pitch angle of a north star is 45 degrees), respectively finding a fixed star with proper brightness according to four directions of south, east, west and north, after the adjustment in the step 101, enabling the image of the fixed star to be located at the same position of the target surface of the fine tracking detector, and observing the circle-drawing phenomenon in the Hartmann detector at the moment; because the telescope is rotated by 360 degrees in the satellite shooting process, the track in the Hartmann detector in four directions is a complete circle, and the central position of the track is obtained through data analysis; and adjusting the central position of the track in the Hartmann detector to the center of the grid of the Hartmann detector by adjusting the translation and inclination values of the three mirrors, and at the moment, the fixed star image in the fine tracking and Hartmann detector circles around the central position of each detector.
S103: repeating the step S101: by adjusting two reflectors (two reflectors which are connected and folded with the under-machine adaptive correction platform after a main optical system passes through a Kudet optical path) in the under-machine adaptive correction platform, a fixed star shot in the north direction (a polaris star can be selected for shooting) is adjusted to the central position of a fine tracking detector, and a star point image collected by a Hartmann detector is ensured to be concentric with a drawn grid, and at the moment, the coincidence of the optical axis of the main optical system and the optical axis of the under-machine adaptive correction platform is completed.
S200: under the unchangeable circumstances of assurance telescope azimuth angle, through the every single move angle that rotates the telescope, according to in the imaging platform of telescope system fine tracking measure with the change of telescope optical axis with the Hartmann detector, according to the measured data of actual measurement, the secondary mirror of adjustment telescope system rotates round no coma point, under the unchangeable prerequisite of assurance primary optical system wave front, eliminates the optical axis change that telescopic's deflection arouses.
Step S200 specifically includes:
s104: the azimuth angle of the telescope is kept unchanged, the pitch angle ranges from 0 degree to 90 degrees, and a fixed star with proper brightness is respectively found at intervals with an angle of 15 degrees as a preset adjusting angle for shooting. Due to the fact that the telescope deflects, the target surface of the fine tracking detector is not located at the same position, due to the fact that the telescope rotates to pitch for 90 degrees in the process of shooting the star, the track of the fixed star image on the fine tracking detector under different pitch angles is one fourth of a circle, and the center position of the track is obtained through data analysis. Adjusting the fixed star image in the fine tracking detector at each pitch angle to the central position in the fine tracking detector after the step S103 is finished on the premise of ensuring that the wavefront of the main optical system is unchanged by adjusting the secondary mirror to rotate around the coma-free point, and eliminating the change of the optical axis caused by the deflection of the telescope; after step S103 is completed, the central positions of the hartmann detector and the fine tracking detector are consistent, the fixed star image is located at the central position of the fine tracking detector, and the fixed star image in the hartmann detector is not circled.
S300: tracking a satellite target through the telescope, tracking the satellite target by the under-machine self-adaptive correction platform in a closed loop and correcting the satellite target in real time, verifying whether pupil offset correction of the telescope is finished or not through the number of effective sub-apertures in the Hartmann detector, and repeating the steps S100 and S200 until the pupil offset correction is finished if the pupil offset correction still exists.
Tracking a satellite target through a telescope (aiming at random change of azimuth and pitch values), tracking a closed loop on the satellite target by an under-machine self-adaptive correction platform and correcting the satellite target in real time, verifying whether pupil offset correction is finished or not through the number of effective sub-apertures in a Hartmann detector (or whether a fixed image and a grid in the Hartmann detector are concentric or not), and repeating the steps from S101 to S104 until the pupil offset correction is finished if deviation still exists.
In a preferred embodiment, the preset adjustment angle is 15 degrees. The 15 degree angle is a non-absolute angle, and in other embodiments, other angles may be selected for shooting.
In a preferred embodiment, the primary mirror of the telescopic system is a primary mirror of silicon carbide material. The main mirror material is SiC, and has the advantages of specific stiffness, light weight and good thermal conductivity.
In a preferred embodiment, the gravity deformation of the 4 m-order primary mirror along with the change of the pitching is serious, so that the ultrahigh surface accuracy of the primary mirror is ensured by adopting an active supporting mode, and the high-accuracy constancy of the position of the primary mirror is realized by a hydraulic supporting system.
The main mirror generates position deviation and angle deviation relative to the main mirror chamber under the action of gravity, and the deviation changes along with the change of the pitch angle of the telescope. In a preferred embodiment, the surface shape precision of the primary mirror is ensured by adopting an active supporting mode; the primary mirror ensures that the absolute position deviation of the primary mirror is 0.02mm through an active support technology, and the influence on the optical axis deviation can be ignored.
In a preferred embodiment, the telescope system secondary mirror and its supporting structure adopt a high-precision Hexapod platform to realize five-dimensional attitude adjustment to compensate the position deviation and optical axis deviation of the main optical system caused by gravity and temperature changes.
The invention has the obvious advantages that the pupil offset of the large-scale foundation self-adaptive telescope can be corrected, the optical axis of the main optical system is aligned with the optical axis of the under-machine self-adaptive platform based on the secondary mirror without a coma point, the system wavefront of the main and secondary mirrors is ensured while the optical axis of the main optical system is changed, the self-adaptive correction effect of the telescope can reach the optimal state, and the invention has higher application value and innovation compared with the traditional method.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.
Claims (10)
1. A pupil offset correction method for a large-aperture self-adaptive telescope is characterized by comprising the following steps:
s100: building a telescope system to enable the telescope system to have a fixed star shooting condition; the shooting fixed star adjustment at least comprises the steps of ensuring that the optical axis of a main optical system of the telescope system is superposed with the optical axis of an off-machine self-adaptive correction platform when the telescope rotates in the azimuth under the condition that the pitching angle of the telescope is not changed;
s200: under the condition that the azimuth angle of the telescope is not changed, measuring the change of the optical axis of the telescope according to fine tracking in an imaging platform of the telescope system and a Hartmann detector by rotating the pitching angle of the telescope, adjusting a secondary mirror of the telescope system to rotate around a coma-free point according to measured data, and eliminating the change of the optical axis caused by deflection of the telescope on the premise that the wavefront of a primary optical system of the telescope system is not changed;
s300: tracking a satellite target through the telescope, tracking the satellite target by an off-board adaptive correction platform in a closed loop and correcting the satellite target in real time, verifying whether pupil offset correction of the telescope is finished or not through the number of effective sub-apertures in the Hartmann detector, and if deviation still exists, repeating the steps S100 and S200 until the pupil offset correction is finished.
2. The large-aperture self-adaptive telescope pupil deviation correction method according to claim 1, wherein the telescope system is built to enable the telescope system to have a shooting star condition; wherein, the fixed star adjustment for shooting at least comprises ensuring that the optical axis of a main optical system of the telescope system and the optical axis of an under-machine adaptive correction platform coincide when the telescope rotates in azimuth under the condition that the pitching angle of the telescope is not changed:
s101: the telescope system has a star shooting condition, the pitch angle of the telescope is guaranteed to be unchanged, a fixed star with the brightness meeting a preset condition is shot according to four directions of south, east, west and north, if the fixed star is not located at the same position of the target surface of the fine tracking detector in the under-machine adaptive correction platform, the track in the Hartmann detector is a complete circle in the four directions due to the fact that the telescope rotates by 360 degrees in the direction of the star shooting process, the central position of the track is obtained through data analysis, the fixed star shot in the north direction is adjusted to the central position of the fine tracking detector by adjusting two reflectors in the under-machine adaptive correction platform, and the star point image collected by the Hartmann detector is guaranteed to be concentric with the drawn grid;
s102: the pitch angle of the telescope is guaranteed to be unchanged, and a fixed star with brightness meeting preset conditions is shot according to four directions of south, east, west and north; after the adjustment, the fixed star image is positioned at the same position of the target surface of the fine tracking detector, and the circle-drawing phenomenon in the Hartmann detector is observed at the moment; the track in the Hartmann detector is a complete circle in four directions due to the fact that the telescope is rotated by 360 degrees in the direction of the satellite shooting process, and the central position of the track is obtained through data analysis; adjusting the central position of a track in the Hartmann detector to the center of a grid of the Hartmann detector by adjusting the translation and inclination values of three mirrors, wherein the fixed star images in the fine tracking detector and the Hartmann detector circle around the central positions of the detectors respectively;
s103: repeating the step S101: and adjusting the fixed star shot in the north direction to the central position of the fine tracking detector and ensuring that the star point image collected by the Hartmann detector is concentric with the drawn grid by adjusting two reflectors in the under-machine self-adaptive correction platform, and finishing the coincidence of the optical axis of the main optical system and the optical axis of the under-machine self-adaptive correction platform.
3. The method for correcting the pupil offset of the large-aperture adaptive telescope according to claim 2, wherein the step of ensuring that the pitch angle of the telescope is unchanged is as follows:
and the pitch angle of the telescope is ensured to be unchanged by 45 degrees.
4. The method for correcting pupil offset of a large-aperture self-adaptive telescope according to claim 3, wherein the method for correcting pupil offset of a large-aperture self-adaptive telescope according to the present invention comprises the steps of, under the condition that the azimuth angle of the telescope is not changed, rotating the pitch angle of the telescope, measuring the change of the optical axis of the telescope according to the fine tracking and hartmann detector in the imaging platform of the telescope system, and adjusting the secondary mirror of the telescope system to rotate around the coma-free point according to the measured data, wherein the method for correcting pupil offset of the large-aperture self-adaptive telescope specifically comprises the steps of:
ensuring that the azimuth angle of the telescope is unchanged, ensuring that each pair of fixed stars meeting preset conditions are shot at intervals of a preset adjusting angle within a range from 0 degree to 90 degrees at a pitch angle; the target surface of the fine tracking detector is not in the same position due to the deflection of the telescope, and the track of the fixed star image on the fine tracking detector under different pitch angles is in a quarter circle shape due to the fact that the telescope rotates to pitch for 90 degrees in the process of shooting the star, and the central position of the track is obtained through data analysis;
through adjusting telescope system' S secondary mirror rotates round no coma point, under the prerequisite of guaranteeing that main optical system wavefront is unchangeable, with each pitch angle down fixed star image adjustment in the accurate tracking detector is to step S103 back central point in the accurate tracking detector, eliminates the optical axis change that telescope deflection arouses.
5. The large aperture adaptive telescope pupil offset correction method of claim 4, wherein the predetermined adjustment angle is 15 degrees.
6. The large aperture adaptive telescope pupil offset correction method of claim 5, wherein the primary mirror of the telescope system is a primary mirror of silicon carbide material.
7. The method for pupil offset correction of large-aperture adaptive telescope according to claim 6, wherein the surface shape accuracy of the primary mirror is ensured by active support.
8. The large-aperture self-adaptive telescope pupil deviation correction method according to claim 7, wherein the main mirror position is kept constant with high precision by means of regulation and control of a hydraulic support system, so that the optical axis of the main mirror is kept constant.
9. The method according to claim 8, wherein the telescope system is provided with a support structure for supporting the secondary mirror, and five-dimensional attitude adjustment of the secondary mirror and the support structure is performed by means of a six-axis platform to compensate for the position deviation and the optical axis deviation of the primary optical system caused by gravity and temperature changes.
10. The method for pupil offset correction of a large-aperture adaptive telescope according to claim 1, wherein the circle of Hartmann camera of the telescope system is eliminated by adjusting the three-mirror translation and tilt modes to ensure that the optical axis of the main optical system of the telescope system coincides with the optical axis of the under-machine adaptive correction platform during the azimuth rotation of the telescope.
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