CN109470236B - Star sensor - Google Patents
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- CN109470236B CN109470236B CN201811414471.1A CN201811414471A CN109470236B CN 109470236 B CN109470236 B CN 109470236B CN 201811414471 A CN201811414471 A CN 201811414471A CN 109470236 B CN109470236 B CN 109470236B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/02—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by astronomical means
- G01C21/025—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by astronomical means with the use of startrackers
Abstract
The invention provides a star sensor, which comprises: the system comprises a front checkerboard grating, a rear checkerboard grating, a checkerboard optical wedge array, a converging optical system and an area array detector, wherein total input light consisting of target light and sky background light is incident into a shearing interferometer consisting of the front checkerboard grating and the rear checkerboard grating, forming a complete period of two-dimensional interference fringe by adjusting the relative angle of the front checkerboard grating and the rear checkerboard grating, the checkerboard optical wedge array performs two-dimensional light splitting on the incident two-dimensional interference fringes, the split light beams formed after the two-dimensional light splitting by the checkerboard optical wedge array are collected to the target surface of the area array detector after passing through the convergence optical system, and acquiring two-dimensional phase information of the two-dimensional interference fringes according to the light intensity of the light spots on the target surface and a corresponding phase extraction algorithm, thereby realizing two-dimensional synchronous high-precision positioning.
Description
Technical Field
The invention relates to the technical field of optical tracking equipment, in particular to a star sensor.
Background
Optical tracking is a widely used technique. The device can be used for precise pointing of laser beams, position and attitude keeping of a flying platform, high-precision tracking of a large-caliber photoelectric telescope and the like. Star tracking devices, commonly referred to as star sensors, acquire position and attitude information of an aircraft (satellites, etc.) by detecting the star field distribution over a large area.
The traditional star sensor generally utilizes an optical lens to converge star light on a target surface of an array detector, and realizes high-precision positioning of a target by methods such as long-focus, small-pixel and interpolation-based sub-pixel centroid extraction. The currently achievable accuracy is about 1/10 to 1/50 pixels. For a 2K by 2K camera, the positioning accuracy of the conventional star sensor in a 20 degree field of view is about 1-2'. In order to obtain higher positioning accuracy, a longer focal length lens and a larger target surface camera are generally adopted, which causes larger volume, more weight and higher power consumption, which is very disadvantageous for a flight platform with resource shortage.
In order to solve the above problems, opc (optical Physics company) company has proposed a novel interferometric star sensor based on shearing interference and fringe phase extraction methods. OPC corporation has demonstrated that this technique can achieve 20 ° -20 ° field of view, 2Hz response speed, and 0.11 "(3 σ) accuracy. However, the star sensors proposed by them can only realize one-dimensional measurement. To achieve two-dimensional measurements, they require two independent star sensors to be co-axially registered. The registration process increases the complexity and cycle of manufacturing. In addition, the volume, the weight and the power consumption of the combined two devices are also multiplied, which is not beneficial to the optimal configuration of the load of the flight platform.
Disclosure of Invention
Therefore, it is necessary to provide a star sensor capable of realizing two-dimensional synchronous high-precision positioning in view of the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a star sensor, comprising: the grating interferometer comprises a front checkerboard grating, a rear checkerboard grating, a checkerboard optical wedge array, a converging optical system and an area array detector, wherein the front checkerboard grating and the rear checkerboard grating form a shearing interferometer, and the shearing interferometer comprises:
the total input light composed of target light and sky background light enters a shearing interferometer composed of the front checkerboard grating and the rear checkerboard grating, and a two-dimensional interference fringe with a complete period is formed by adjusting the relative angle of the front checkerboard grating and the rear checkerboard grating;
the checkered optical wedge array performs two-dimensional light splitting on the incident two-dimensional interference fringes, split light beams formed after the two-dimensional light splitting of the checkered optical wedge array are collected to the target surface of the area array detector after passing through the convergence optical system, and two-dimensional phase information of the two-dimensional interference fringes is obtained according to the light intensity of light spots of the target surface and a corresponding phase extraction algorithm.
In some preferred embodiments, the pre-checkerboard grating and the post-checkerboard grating are phase-type gratings.
In some preferred embodiments, the size of the checkerboard wedge array is equal to or slightly smaller than the area of interference fringes formed by the front checkerboard grating and the rear checkerboard grating constituting the shearing interferometer.
In some preferred embodiments, the number of wedge units per dimension of the checkered wedge array is at least 3.
In some preferred embodiments, the number of wedge elements per dimension of the checkered wedge array corresponds to the phase extraction algorithm employed.
In some preferred embodiments, the converging optical system is an achromatic lens group.
In some preferred embodiments, the clear aperture of the converging optical system is larger than the array range of the light beams output by the checkered wedge array.
In some preferred embodiments, the focusing spot size of the collection optics is approximately equal to 1 or 2 pixels in the area array detector.
In some preferred embodiments, the area-array detector is a CCD camera or a CMOS camera or a photodiode array PDA.
The invention adopts the technical scheme that the method has the advantages that:
the star sensor provided by the invention has the advantages that total input light consisting of target light and sky background light enters a shearing interferometer consisting of the front checkered grating and the rear checkered grating, a complete period of two-dimensional interference fringe is formed by adjusting the relative angle of the front checkered grating and the rear checkered grating, the checkered optical wedge array performs two-dimensional light splitting on the incident two-dimensional interference fringe, split light beams formed by the two-dimensional light splitting of the checkered optical wedge array are converged to the target surface of the area array detector through the converging optical system, and two-dimensional phase information of the two-dimensional interference fringe is obtained according to the light spot light intensity of the target surface and a corresponding phase extraction algorithm, so that two-dimensional synchronous high-precision positioning is realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a star sensor provided by the present invention;
fig. 2 is a schematic structural diagram of a pre-checkerboard grating and a post-checkerboard grating and two-dimensional interference fringes formed according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a checkerboard optical wedge array according to an embodiment of the present invention;
FIG. 4 is a distribution diagram of an array of spots on a target surface of a detector according to an embodiment of the present invention.
Detailed Description
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.
Referring to fig. 1, a schematic structural diagram of a star sensor according to an embodiment of the invention includes: the grating interferometer comprises a front checkerboard grating 2, a rear checkerboard grating 3, a checkerboard optical wedge array 4, a converging optical system 5 and an area array detector 6, wherein the front checkerboard grating 2 and the rear checkerboard grating 3 form a shearing interferometer.
The specific embodiments of the respective components are described in detail below.
The front checkerboard grating 2 and the rear checkerboard grating 3 form a shearing interferometer, so that shearing interference in the horizontal direction and the vertical direction can be achieved simultaneously, two-dimensional interference fringe distribution is formed, and the two-dimensional interference fringe distribution corresponds to two-dimensional angular positions of a target respectively.
Referring to fig. 2, a total input light 1 composed of a target light and a sky background light is incident into a two-dimensional interference fringe 10 formed in a shearing interferometer composed of the front checkerboard grating 2 and the rear checkerboard grating 3.
In some preferred embodiments, the pre-checkerboard grating 2 and the post-checkerboard grating 3 are phase type gratings.
It will be appreciated that the phase grating should be chosen to suppress the interference of zero-order light, since the pre-checkerboard grating 2 and the post-checkerboard grating 3 are chosen to be phase-type gratings. The grating period and the grating distance of the pre-checkerboard grating 2 and the post-checkerboard grating 3 can be selected according to specific functional requirements such as working spectral bandwidth, dispersion suppression, high-level diffraction light suppression and the like.
Preferably, the grating periods of the grating horizontal and vertical directions of the front checkerboard grating 2 and the back checkerboard grating 3 can be selected to be 50 μm, and the distance between the two can be selected to be 5 cm. It will be appreciated that other dimensions of grating period and inter-grating distance may be selected depending on specific functional requirements of operating spectral bandwidth, dispersion suppression and higher order diffraction light suppression.
In some preferred embodiments, the number of wedge units per dimension of the checkered wedge array 4 is at least 3.
It will be appreciated that the two-dimensional interference fringes are incident on the surface of the checkered wedge array 4, and each wedge element may direct a beam incident on its surface at an oblique angle.
In some preferred embodiments, the number of wedge units per dimension of the checkered wedge array 4 is at least 3, and the number of wedge units per dimension of the checkered wedge array 4 corresponds to the phase extraction algorithm employed.
It will be appreciated that in practice the checkerboard wedge array 4 may comprise 4 wedge units, or more (up to 5, 8 or even more than 10). The number of elements per dimension of the checkerboard wedge array 4 corresponds to the phase extraction algorithm employed. If each dimension adopts 3 units, a 3-step phase extraction algorithm is selected, if each dimension adopts 4 units, a 4-step phase extraction algorithm is adopted, and the like. In addition, more cell numbers can cover more fringe periods (> 1), so the measurement data has redundancy to suppress noise effects and improve signal-to-noise ratio.
Please refer to fig. 3, which is a schematic structural diagram of the checkerboard optical wedge array 4 according to a preferred embodiment of the present invention.
In this embodiment, wedge units 11 and 13 correspond to wedge type 27, wedge units 16 and 18 correspond to wedge type 28, wedge units 19 and 21 correspond to wedge type 29, wedge units 24 and 26 correspond to wedge type 30, wedge units 12 and 14 correspond to wedge type 31, wedge units 15 and 17 correspond to wedge type 32, wedge units 20 and 22 correspond to wedge type 33, and wedge units 23 and 25 correspond to wedge type 34. Different optical wedge types have different combinations of two-dimensional wedge angles (i.e., a combination of wedge angles in the horizontal or x-axis direction and wedge angles in the vertical or y-axis direction).
In some preferred embodiments, the size of the checkerboard wedge array 4 is equal to or slightly smaller than the area of interference fringes formed by the front checkerboard grating 2 and the rear checkerboard grating 3 which constitute a shearing interferometer.
In some preferred embodiments, the converging optical system 5 is an achromatic lens group.
Furthermore, the clear aperture of the converging optical system 5 is larger than the range of the light beam array output by the checkerboard optical wedge array 4, and the focal length of the converging optical system ensures that the diameter of a converging light spot is smaller and is approximately equal to the size of 1 or 2 pixels in the area array detector 6.
The area array detector 6 is a CCD camera or a CMOS camera or a photodiode array PDA. It is understood that the indexes of the area array detector 6, such as detection sensitivity, working spectral width, resolution and pixel size, should be selected according to the specific application requirements.
Referring to fig. 1 and fig. 3, the star sensor provided by the present invention operates as follows:
a total input light 1 consisting of a target light and a sky background light enters a shearing interferometer consisting of the front checkerboard grating 2 and the rear checkerboard grating 3, and a two-dimensional interference fringe with a complete period is formed by adjusting the relative angle of the front checkerboard grating 2 and the rear checkerboard grating 3;
the checkered optical wedge array 4 performs two-dimensional light splitting on the incident two-dimensional interference fringes, split light beams formed after the two-dimensional light splitting of the checkered optical wedge array 4 are gathered to the target surface of the area array detector 6 after passing through the convergence optical system 5, and two-dimensional phase information of the two-dimensional interference fringes is obtained according to the light spot light intensity of the target surface and a corresponding phase extraction algorithm.
It can be understood that the output light beams of the checkered wedge array 4 are converged on the target surface of the area array detector 6 after passing through the converging optical system 5, so as to form 8 light spots with different brightness. The correspondence between the unit of the checkered optical wedge array 4 and the target surface light spot of the area array detector 6 is as follows: wedge units 11 and 13 correspond to spot 35, wedge units 16 and 18 correspond to spot 36, wedge units 19 and 21 correspond to spot 37, wedge units 24 and 26 correspond to spot 38, wedge units 12 and 14 correspond to spot 39, wedge units 15 and 17 correspond to spot 40, wedge units 20 and 22 correspond to spot 41, and wedge units 23 and 25 correspond to spot 42.
It is understood that the intensities of the spots 35, 36, 37 and 38 represent 4 intensity values of the equally spaced (with phase spacing of π/2) distribution in the horizontal or x-axis direction intensity distribution in the two-dimensional interference fringe 10 formed by the shearing interferometer, respectively; the intensities of the light spots 39, 40, 41 and 42 respectively represent 4 light intensity values which are distributed at equal intervals (phase interval is pi/2) in the light intensity distribution in the vertical or y-axis direction in the two-dimensional interference fringe 10 formed by the shearing interferometer, after convergence, the light intensity distribution of each dimension of the interference fringe respectively corresponds to four light spots, so that the two-dimensional distribution corresponds to eight light spots, and the four light spots corresponding to each dimension have phase difference of pi/2.
It can be understood that the phase of the fringe in the dimension is calculated by using a phase extraction method similar to a phase-shift interferometer through the light intensities of the four light spots, and the fringe phase extraction method is mature and has the precision superior to lambda/100, so that the method can realize high positioning precision; similarly, the fringe phase of the other dimension can also be calculated, so that the simultaneous extraction of two-dimensional phase information of interference fringes can be realized through the star sensor, and the two-dimensional synchronous high-precision positioning can be realized.
Of course, the star sensor of the present invention may have various changes and modifications, and is not limited to the specific structure of the above-described embodiments. In conclusion, the scope of the present invention should include those changes or substitutions and modifications which are obvious to those of ordinary skill in the art.
Claims (4)
1. A star sensor, comprising: the grating interferometer comprises a front checkerboard grating, a rear checkerboard grating, a checkerboard optical wedge array, a converging optical system and an area array detector, wherein the front checkerboard grating and the rear checkerboard grating form a shearing interferometer, and the shearing interferometer comprises:
the total input light composed of target light and sky background light enters a shearing interferometer composed of the front checkerboard grating and the rear checkerboard grating, and a two-dimensional interference fringe with a complete period is formed by adjusting the relative angle of the front checkerboard grating and the rear checkerboard grating;
the checkered optical wedge array performs two-dimensional light splitting on incident two-dimensional interference fringes, split light beams formed after the two-dimensional light splitting of the checkered optical wedge array are gathered to a target surface of the area array detector through the convergence optical system, and two-dimensional phase information of the two-dimensional interference fringes is obtained according to light spot light intensity of the target surface and a corresponding phase extraction algorithm; the number of optical wedge units of each dimension of the checkerboard optical wedge array is at least 3; the optical wedge units correspond to corresponding optical wedge types, and different optical wedge types have different two-dimensional wedge angle combinations.
2. The star sensor of claim 1 wherein the pre-checkerboard grating and the post-checkerboard grating are phase type gratings.
3. The star sensor of claim 1, wherein the number of wedge elements per dimension of the checkered wedge array corresponds to the phase extraction algorithm employed.
4. The star sensor of claim 1 wherein the collection optics have a clear aperture that is larger than the array extent of the light beams output by the checkered wedge array.
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| CN110888177B (en) * | 2019-12-12 | 2021-07-02 | 中国科学院长春光学精密机械与物理研究所 | Dark and weak target detection device under strong sky light background |
| CN112198579B (en) * | 2020-11-11 | 2021-06-01 | 中国科学院长春光学精密机械与物理研究所 | Sky light background noise suppressor, optical search telescope and star sensor |
| CN113280810B (en) * | 2021-06-02 | 2023-04-07 | 中国科学院长春光学精密机械与物理研究所 | Star sensor and detection method thereof |
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