A relative attitude monitoring device between a star sensor and a camera

Abstract

The application discloses a relative attitude monitoring device between a star sensor and a camera, which is composed of a point light source, a corner reflector, a Fresnel double mirror, a light spot sensor and a relative attitude processing unit. The monitoring device realizes the monitoring of the relative attitude change between the star sensor and the camera by calculating and analyzing the centroid position change of the light spot formed by the light source on the light spot sensor in real time, reduces the angle error between the visual axis of the star sensor and the visual axis of the camera, improves the determination precision of the visual axis of the camera, and further improves the geometric positioning precision of the camera.

Description

Technical Field

[0001] This invention relates to the field of high geometric positioning accuracy space optical remote sensing technology, and in particular to a relative attitude monitoring device between a star sensor and a camera. Background Technology

[0002] With the continuous development of space optical remote sensing technology, the spatial resolution, temporal resolution, and radiometric imaging quality of remote sensing satellites have been continuously improved. In recent years, users have put forward increasingly higher requirements for the geometric positioning accuracy of remote sensing satellites. Earth observation not only needs to be "visible" and "clear," but also "accurate."

[0003] There are many factors that affect the geometric positioning accuracy of remote sensing satellites, including orbit measurement error, attitude measurement error, camera internal orientation element error, relative attitude error between star sensor and camera, attitude stability introduced error, ground processing error, time synchronization accuracy introduced error, calibration error, processing algorithm error, atmospheric introduced error, and optical aberration.

[0004] In recent years, with the continuous improvement of satellite platform attitude stability, orbit determination accuracy, and time synchronization accuracy, the impact on ground positioning accuracy has become relatively minor, becoming a secondary factor. Domestic institutions have reached internationally advanced levels in geometric calibration and processing analysis, achieving high accuracy in calibration and processing errors, thus minimizing their impact on geometric positioning accuracy. Algorithms for handling atmospheric errors and optical aberrations are relatively mature and can correct most errors.

[0005] Therefore, the main factors affecting positioning accuracy are attitude measurement error, relative attitude error between the star sensor and the camera, and orientation element error within the camera. Attitude measurement error is mainly studied and resolved by the star sensor development unit, while orientation element error within the camera is mainly studied and resolved by the camera development unit. In recent years, significant progress has been made in controlling attitude measurement error and orientation element error within the camera, and the errors can be controlled to a relatively small level.

[0006] The relative attitude error between the star sensor and the camera is a boundary problem between different payload development units, and it has not been effectively solved for a long time.

[0007] Traditional methods for reducing the relative attitude error between star sensors and cameras primarily involve optimizing structural stability design, improving thermal control accuracy, and increasing the accuracy and frequency of on-orbit geometric calibration. However, these traditional methods have significant limitations, mainly due to:

[0008] 1) Traditional methods for reducing the relative attitude error between the star sensor and the camera still leave a large residual error, generally greater than 3″ (3σ);

[0009] 2) Traditional methods for reducing the relative attitude error between the star sensor and the camera require increasing mass, power consumption, and cost;

[0010] 3) Traditional methods for reducing the relative attitude error between the star sensor and the camera require periodic geometric calibration, which is constrained by the calibration frequency. Summary of the Invention

[0011] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a relative attitude monitoring device between a star sensor and a camera. This device effectively solves the problem of high-precision, real-time monitoring of the relative attitude between the star sensor and the camera, and can significantly improve the accuracy of camera line-of-sight pointing determination, thereby significantly improving the geometric positioning accuracy of the target.

[0012] The objective of this invention is achieved through the following technical solutions:

[0013] A relative attitude monitoring device between a star sensor and a camera includes: a point light source, a corner mirror, a Fresnel double mirror, a spot sensor, and a relative attitude processing unit;

[0014] The point light source is fixedly connected to the camera's image sensor. The point light source is located at the camera's image plane. The point light source emits a divergent beam of light against the direction of light entering the camera, and the divergent beam of light enters the camera's lens.

[0015] The corner mirror is fixedly connected to the camera lens and is located at the light entrance of the camera lens; the mirror receives the parallel light beam after it has been collimated by the camera lens.

[0016] An angle mirror is used to fold a parallel beam of light 180 degrees, and the folded parallel beam of light is then incident on a Fresnel double mirror.

[0017] The Fresnel double mirror is fixedly connected to the star sensor. The Fresnel double mirror is used to reflect the incident parallel beam of light back and split it into two parallel beams for transmission to the corner mirror.

[0018] The corner mirror folds the two reflected parallel beams by 180 degrees. The two parallel beams after the folding are then incident on the camera lens. The camera lens converges the two parallel beams into two converging beams that converge at the camera's image plane and are then incident on spot sensor I and spot sensor II, respectively.

[0019] Spot sensor I and spot sensor II are fixedly connected to the camera image sensor and located at the image plane of the camera. They are used to receive two converging beams from the camera lens to achieve spot image acquisition.

[0020] The relative attitude processing unit extracts the centroid position of the light spot based on the light spot images acquired by light spot sensor I and light spot sensor II, and calculates the relative attitude change between the star sensor and the camera based on the change data of the light spot centroid.

[0021] Preferably, the size of the emitting surface of the point light source corresponds to the pixel size of the spot sensor I and the spot sensor II; the spectral band of the point light source is within the response spectral band range of the spot sensor I and the spot sensor II.

[0022] Preferably, the included angle of the Fresnel double mirror is equal to (180-ω)°; where ω is equal to half of the camera field of view angle corresponding to the line segment connecting the center point of the two spot sensor I and the center point of the spot sensor II.

[0023] Preferably, both the corner mirror and the Fresnel double mirror are made of microcrystalline materials.

[0024] Preferably, the surface shape accuracy of the reflecting surfaces of the corner mirror and the Fresnel double mirror is less than or equal to 1 / 30λRMS, where λ is the center wavelength of the point light source.

[0025] Preferably, the pixel size of the area array image sensor is ≤10μm, and the photosensitive area is greater than or equal to 2fε; where f is the camera focal length, and ε is the maximum angle change between the optical axis of the star sensor and the optical axis of the camera.

[0026] Preferably, the point light source, the spot sensor, and the camera image sensor are mounted on the same structure.

[0027] Preferably, both spot sensor I and spot sensor II are area array image sensors;

[0028] The center points of spot sensor I and spot sensor II are symmetrical about the OXZ plane of the camera coordinate system;

[0029] The origin O of the camera coordinate system is located at the midpoint of the line connecting the center point of spot sensor I and the center point of spot sensor II; the X-axis is along the column direction of the pixel array of spot sensor I, and the Y-axis is along the row direction of the pixel array of spot sensor I; the Z-axis is perpendicular to the X-axis and Y-axis, forming a right-handed rectangular coordinate system.

[0030] Preferably, the relative attitude processing unit calculates the relative attitude change (ε) between the star sensor and the camera. x , ε y , ε z Specifically:

[0031]

[0032]

[0033]

[0034] Wherein, Δx1 is the spot offset of the spot on the spot sensor I along the X1 axis relative to the calibrated spot centroid position, Δx2 is the spot offset of the spot on the spot sensor II along the X2 axis relative to the calibrated spot centroid position, Δy1 is the spot offset of the spot on the spot sensor I along the Y1 axis relative to the calibrated spot centroid position, and Δy2 is the spot offset of the spot on the spot sensor II along the Y2 axis relative to the calibrated spot centroid position;

[0035] The origin O of the coordinate system of the light spot sensor I is located at the center point of the light spot sensor I. The X1 axis is along the column direction of the pixel array of the light spot sensor I, and the Y1 axis is along the row direction of the pixel array of the light spot sensor I.

[0036] The origin O of the coordinate system of the light spot sensor II is located at the center point of the light spot sensor II. The X2 axis is along the column direction of the pixel array of the light spot sensor II, and the Y2 axis is along the row direction of the pixel array of the light spot sensor II.

[0037] ω x ω is the camera field of view corresponding to the component on the X-axis of the camera coordinate system from the center point of the light spot sensor I to the intersection of the camera optical axis and the image plane; y The camera field of view is the component on the Y-axis of the camera coordinate system corresponding to the intersection of the center point of the light spot sensor I and the intersection of the camera optical axis and the image plane.

[0038] L is the distance from the center point of light spot sensor I to the center point of light spot sensor II.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) The present invention uses a relative attitude monitoring device between a star sensor and a camera, which can accurately monitor the random angle changes between the star sensor and the camera in real time on orbit.

[0041] (2) The present invention uses a high-precision optical measurement method and a high-stability optical component (Fresnel double mirror, plane mirror), which has high measurement accuracy and can realize sub-arcsecond level relative attitude monitoring;

[0042] (3) The present invention uses an internal high-stability point light source, which does not require external reference information such as calibration field, and can realize on-orbit autonomous calibration. It has strong availability, high reliability, high measurement frequency and high measurement accuracy. Attached Figure Description

[0043] Figure 1 This is a block diagram of the star sensor and camera relative attitude monitoring device of the present invention;

[0044] Figure 2 This is a schematic diagram of the light spot sensor and imaging focal plane layout of the present invention.

[0045] Among them, 1-a beam emitted by a point source, 2-a parallel beam after collimation by the camera lens, 3-a parallel beam after 180-degree folding by the corner mirror, 4-two parallel beams after folding by the Fresnel double mirror, 5-two parallel beams after 180-degree folding by the corner mirror, 6-two converging beams after convergence by the camera lens, and 7-spot image data from the spot sensor. Detailed Implementation

[0046] This invention proposes a star sensor and camera relative attitude monitoring device, which can realize real-time high-precision on-orbit measurement of the relative attitude of the star sensor and camera, effectively solves the problem of relative attitude offset between the star sensor and camera caused by factors such as temperature changes, effectively improves the accuracy of camera line-of-sight pointing determination, and thus improves the geometric positioning accuracy of camera imaging targets.

[0047] like Figure 1 As shown, the present invention discloses a relative attitude monitoring device between a star sensor and a camera, comprising: a point light source, a corner reflector, a Fresnel double-sided mirror, a spot sensor, and a relative attitude processing unit;

[0048] A star sensor is an attitude measurement device that provides attitude information to the camera. This invention utilizes a Fresnel double-sided mirror to characterize the positional relationship between the star sensor and the camera;

[0049] A camera is an imaging device, mainly composed of a camera lens and a camera image sensor, used to acquire image information of the observed target; a star sensor and a camera are the objects monitored by the relative attitude monitoring device; the camera and the star sensor are fixedly connected.

[0050] The light source is fixed to the camera image sensor and located at the image plane of the camera. It emits a divergent beam 1 against the direction of light entering the camera and the divergent beam 1 enters the camera lens.

[0051] The camera lens collimates the divergent beam 1 emitted by the light source to obtain a parallel beam 2, which exits from the camera's light inlet and enters the corner mirror.

[0052] The corner mirror is fixed to the camera lens and located at the camera lens entrance. The corner mirror is used to deflect the parallel beam 2 by 180 degrees, and the deflected parallel beam 3 is incident on the Fresnel double mirror;

[0053] The Fresnel double mirror is fixed to the star sensor. The Fresnel double mirror is used to reflect the incident parallel beam 3 and split it into two parallel beams 4 to be transmitted to the corner mirror.

[0054] The corner mirror folds the two parallel beams 4 by 180 degrees, and the two parallel beams 5 after the folding are incident on the camera lens. The camera lens converges the two parallel beams 5 into two converging beams 6, which converge at the camera image plane and are incident on the spot sensor I and spot sensor II respectively.

[0055] There are two spot sensors, namely spot sensor I and spot sensor II, which are fixedly connected to the camera image sensor and located at the image plane of the camera. They are used to receive two converging light beams 6 converged by the camera lens to realize spot image acquisition.

[0056] The relative attitude processing unit extracts the centroid position of the light spot based on the light spot image data 7 from the light spot sensor, and calculates the relative attitude change between the star sensor and the camera based on the change data of the light spot centroid.

[0057] The size of the emitting surface of the point light source is comparable to the pixel size of spot sensor I and spot sensor II, and the spectral band of the point light source is within the response spectral band range of the spot sensor.

[0058] The corner mirror and Fresnel double mirror are made of highly stable materials such as microcrystals. The surface shape accuracy of the reflecting surface of the corner mirror and Fresnel double mirror is better than 1 / 30λRMS, where λ is the center wavelength of the point light source.

[0059] The included angle of the Fresnel double mirror is equal to (180-ω)°, where ω is equal to half of the camera field of view angle corresponding to the line segment connecting the center point of the two spot sensor I and the center point of the spot sensor II. The included angle stability of the Fresnel double mirror is better than 0.03 times the camera angular resolution.

[0060] Both light spot sensor I and light spot sensor II use area array image sensors with a pixel size ≤10μm and a light-sensitive area ≥(2f×ε), where f is the camera focal length and ε is the maximum angle change between the optical axis of the star sensor and the optical axis of the camera.

[0061] The point light source, spot sensor, and camera image sensor are all located on the image plane of the camera lens. The three are mounted on the same structure, and the relative positional stability between them is better than 1μm.

[0062] The relative attitude processing unit uses the position of the spot centroid calibrated by the spot sensor as a reference value to calculate the offset of the subsequent spot centroid position relative to the reference position, thereby obtaining the relative attitude change (ε) between the camera and the star sensor. x , ε y , ε z );

[0063]

[0064]

[0065]

[0066] Where, ε x ε represents the angular variation of the Fresnel double mirror around the X-axis of the camera coordinate system. y ε represents the angular variation of the Fresnel double mirror around the Y-axis of the camera coordinate system. z This refers to the change in angle around the Z-axis;

[0067] The origin O of the camera coordinate system is located at the midpoint of the line connecting the center point of spot sensor I and the center point of spot sensor II; the X-axis is along the column direction of the spot sensor pixel array, and the Y-axis is along the row direction of the spot sensor pixel array; the Y-axis direction is along the line connecting the center points of the two spot sensors; the Z-axis is perpendicular to the X-axis and Y-axis, forming a right-handed rectangular coordinate system.

[0068] The light spot sensor includes light spot sensor I and light spot sensor II. The origins of the coordinate systems of light spot sensor I and light spot sensor II are located at the center points of their respective light spot sensors.

[0069] The origin O of the coordinate system of spot sensor I is located at the center point of spot sensor I. The X1 axis is along the column direction of the pixel array of spot sensor I, and the Y1 axis is along the row direction of the pixel array of spot sensor I. The origin O of the coordinate system of spot sensor II is located at the center point of spot sensor II. The X2 axis is along the column direction of the pixel array of spot sensor II, and the Y2 axis is along the row direction of the pixel array of spot sensor II. The positive directions of the Y1 axis and the Y2 axis are the same.

[0070] Δx1 is the spot offset of light sensor I along the X1 axis relative to the centroid position of light sensor I as calibrated; Δx2 is the spot offset of light sensor II along the X2 axis relative to the centroid position of light sensor II as calibrated; Δy1 is the spot offset of light sensor I along the Y1 axis relative to the centroid position of light sensor I as calibrated; Δy2 is the spot offset of light sensor II along the Y2 axis relative to the centroid position of light sensor II as calibrated.

[0071] The center points of spot sensor I and spot sensor II are symmetrical about the OXZ plane of the camera coordinate system; ω x ω is the camera field of view corresponding to the component on the X-axis of the camera coordinate system from the center point of the light spot sensor I to the intersection of the camera optical axis and the image plane; y The camera field of view is the component on the Y-axis of the camera coordinate system corresponding to the intersection of the center point of the light spot sensor I and the intersection of the camera optical axis and the image plane.

[0072] L is the distance from the center point of light spot sensor I to the center point of light spot sensor II.

[0073] Figure 2 This is a schematic diagram and coordinate diagram of the relative attitude monitoring device between the star sensor and the camera of the present invention.

[0074] The relative angle change information between the camera and the star sensor can eliminate the angle stability error between the star sensor and the camera. Combined with the attitude information of the star sensor, the line of sight of the camera can be accurately determined, thereby improving the target positioning accuracy.

[0075] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention using the disclosed methods and techniques without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall fall within the protection scope of the present invention. Where there is no conflict, the embodiments of this application and the technical features thereof can be combined with each other.

[0076] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A device for monitoring the relative attitude between a star sensor and a camera, characterized in that, include: Point light source, corner reflector, Fresnel double mirror, spot sensor I, spot sensor II, and relative attitude processing unit; The point light source is fixedly connected to the camera's image sensor. The point light source is located at the camera's image plane. The point light source emits a divergent beam of light against the direction of light entering the camera, and the divergent beam of light enters the camera's lens. The corner mirror is fixedly connected to the camera lens and is located at the light entrance of the camera lens; the mirror receives the parallel light beam after it has been collimated by the camera lens. An angle mirror is used to fold a parallel beam of light 180 degrees, and the folded parallel beam of light is then incident on a Fresnel double mirror. The Fresnel double mirror is fixedly connected to the star sensor. The Fresnel double mirror is used to reflect the incident parallel beam of light back and split it into two parallel beams for transmission to the corner mirror. The corner mirror folds the two reflected parallel beams by 180 degrees. The two parallel beams after the folding are then incident on the camera lens. The camera lens converges the two parallel beams into two converging beams that converge at the camera's image plane and are then incident on spot sensor I and spot sensor II, respectively. Spot sensor I and spot sensor II are fixedly connected to the camera image sensor and located at the image plane of the camera. They are used to receive two converging beams from the camera lens to achieve spot image acquisition. The relative attitude processing unit extracts the centroid position of the light spot based on the light spot images acquired by light spot sensor I and light spot sensor II, and calculates the relative attitude change between the star sensor and the camera based on the change data of the light spot centroid.

2. The relative attitude monitoring device between a star sensor and a camera according to claim 1, characterized in that, The size of the emitting surface of the point light source corresponds to the pixel size of spot sensor I and spot sensor II; the spectral band of the point light source is within the response spectral band range of spot sensor I and spot sensor II.

3. The relative attitude monitoring device between a star sensor and a camera according to claim 1, characterized in that, The included angle of the Fresnel double mirror is equal to (180-ω)°; where ω is equal to half of the camera field of view corresponding to the line segment connecting the center point of the two spot sensor I and the center point of the spot sensor II.

4. The relative attitude monitoring device between a star sensor and a camera according to claim 1, characterized in that, Both the corner mirror and the Fresnel double mirror are made of microcrystalline materials.

5. The relative attitude monitoring device between a star sensor and a camera according to claim 1, characterized in that, The surface shape accuracy of the reflecting surface of corner mirrors and Fresnel double mirrors is less than or equal to λ / 30, where λ is the center wavelength of the point light source.

6. The relative attitude monitoring device between a star sensor and a camera according to claim 1, characterized in that, The pixel size of the area array image sensor is ≤10μm, and the photosensitive area is greater than or equal to 2fε; where f is the camera focal length and ε is the maximum angle change between the optical axis of the star sensor and the optical axis of the camera.

7. The relative attitude monitoring device between a star sensor and a camera according to claim 1, characterized in that, The point light source, the spot sensor, and the camera image sensor are all mounted on the same structure.

8. A relative attitude monitoring device between a star sensor and a camera according to any one of claims 1 to 7, characterized in that, Both spot sensor I and spot sensor II use area array image sensors; The center points of spot sensor I and spot sensor II are symmetrical about the OXZ plane of the camera coordinate system; The origin O of the camera coordinate system is located at the midpoint of the line connecting the center point of spot sensor I and the center point of spot sensor II; the X-axis is along the column direction of the pixel array of spot sensor I, and the Y-axis is along the row direction of the pixel array of spot sensor I; the Z-axis is perpendicular to the X-axis and Y-axis, forming a right-handed rectangular coordinate system.

9. The relative attitude monitoring device between a star sensor and a camera according to claim 8, characterized in that, The relative attitude processing unit calculates the relative attitude change between the star sensor and the camera. ε x , ε y , ε z Specifically: Wherein, Δx1 is the spot offset of the spot on the spot sensor I along the X1 axis relative to the calibrated spot centroid position, Δx2 is the spot offset of the spot on the spot sensor II along the X2 axis relative to the calibrated spot centroid position, Δy1 is the spot offset of the spot on the spot sensor I along the Y1 axis relative to the calibrated spot centroid position, and Δy2 is the spot offset of the spot on the spot sensor II along the Y2 axis relative to the calibrated spot centroid position; ε x For the angle change of the Fresnel double mirror around the X-axis of the camera coordinate system, ε y For the angle variation of the Fresnel double mirror around the Y-axis of the camera coordinate system, ε z This refers to the change in angle around the Z-axis; The origin O of the coordinate system of the light spot sensor I is located at the center point of the light spot sensor I. The X1 axis is along the column direction of the pixel array of the light spot sensor I, and the Y1 axis is along the row direction of the pixel array of the light spot sensor I. The origin O of the coordinate system of the light spot sensor II is located at the center point of the light spot sensor II. The X2 axis is along the column direction of the pixel array of the light spot sensor II, and the Y2 axis is along the row direction of the pixel array of the light spot sensor II. ω x ω is the camera field of view corresponding to the component on the X-axis of the camera coordinate system from the center point of the light spot sensor I to the intersection of the camera optical axis and the image plane; y The camera field of view is the component on the Y-axis of the camera coordinate system corresponding to the intersection of the center point of the light spot sensor I and the intersection of the camera optical axis and the image plane. f is the camera focal length, and L is the distance from the center point of light spot sensor I to the center point of light spot sensor II.

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