An inter-satellite laser interferometry method with a front angle adjustment unit with minimal optical path variation

Abstract

The application discloses an inter-satellite laser interferometry method with a front angle adjusting unit with a small optical path change, and the method is applied to an inter-satellite laser interferometry device, and the device comprises two adjacent satellites, a test mass, an optical platform, a telescope, a front angle adjusting unit and a detector; the satellites rotate along with the test mass, and the optical platform and the telescope are arranged on each satellite; the front angle adjusting unit comprises a laser for emitting a laser beam, a first precision rotating mirror, a second precision rotating mirror and a telescope pupil; the laser, the first precision rotating mirror, the second precision rotating mirror and the detector are arranged on the optical platform, and the telescope pupil is located at a joint of the optical platform and the telescope; in the application, the front angle adjusting unit is used to realize the emission of the laser beam from the center of the telescope pupil at a specified front angle with a small optical path change through the cooperation of the two precision rotating mirrors, so that the optical path error is suppressed, and the purpose of realizing high-precision inter-satellite laser interferometry displacement measurement is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of space gravitational wave detection, and in particular to an interstellar laser interferometry measurement method with a front angle adjustment unit having an extremely small optical path change. Background Art

[0002] The Tianqin Project is expected to have a height of approximately 1×10 8 Three spacecraft are deployed in the Earth orbit at a height of 1.7×10 8 m equilateral triangle constellation. At this intersatellite distance, the measurement sensitivity of the intersatellite laser interferometer needs to reach 1pm / Hz 1 / 2 , thereby detecting gravitational wave signals with a frequency range of 0.1 mHz to 1 Hz. The long-distance propagation of the laser beams on the three spacecraft results in a non-negligible beam transmission time delay of 0.58 seconds. Therefore, on each spacecraft, there is an angular difference between the optimal outgoing and incoming laser beams of the interstellar laser interferometer, which is called the forward pointing angle. Due to the relative motion between the three spacecraft, the forward pointing angle of the laser beams of the three satellites of the Tianqin program is about 23.070 , the dynamic range is ±25nrad, and a front finger angle mechanism is required to perform high-precision compensation for the front finger angle to reduce the laser beam pointing error, thereby maintaining the intersatellite laser measurement link and reducing the tilt-to-length (TTL) coupling noise, which is crucial for space gravitational wave detection.

[0003] When gravitational waves pass, they cause subtle changes in the distance between the two test masses in the same arm of the two satellites. Therefore, the Tianqin project uses a laser interferometry system to accurately read the change in the test mass separation. This separation is measured in three stages: the distance between the local test mass and the local optical platform, the distance between the contralateral optical platform and the contralateral test mass, and the distance between the local optical platform and the contralateral optical platform. The first two are read out using a test mass optical reading interferometer, while the latter is read out using a long-baseline intersatellite laser interferometer. The outgoing beam of the long-baseline intersatellite laser interferometer originates from the laser on the local optical platform. After the outgoing beam's fore-angle adjustment is adjusted by the fore-angle adjustment unit, it is emitted from the center of the telescope's exit pupil and transmitted across long distances between satellites to be received by a detector on the contralateral optical platform. The fore-angle adjustment unit generates significant TTL coupling noise during beam pointing, which is one of the main noise sources affecting intersatellite laser ranging.

[0004] During the process of adjusting the front angle of the outgoing beam by the front angle unit, according to the reflection theorem, the outgoing beam pointing angle is twice the rotation angle of the reflecting surface of the front angle mechanism. The reflected beam will deviate from the original beam path and cannot be emitted from the center of the telescope's exit pupil. In addition, the optical path of the beam passing through the front angle unit changes significantly compared to the optical path without angular deflection. The change in the optical path can be calculated as ,in is the distance from the reflection point of the outgoing beam to the center of the exit pupil, The precision mirror reflective surface is the rotation angle around the optical reflection center. Taking the front finger angle adjustment unit of the LISA mission as an example, d is 250mm. The optical path length change caused by ±3.4urad is 2.31e -11 m. This is unacceptable for interstellar laser ranging missions, which require optical path stability of less than pm. Therefore, it is necessary to design a lead angle adjustment unit with minimal optical path variation to ensure that the outgoing beam emerges from the center of the telescope pupil at a specified lead angle, thereby achieving high-precision interstellar laser interferometry.

[0005] The current space-based gravitational wave detection mission, LISA, aims to address the optical path error caused by the deflection of the forward-pointing angle mirror by employing an optical path adjustment method with multiple tiltable planar lens groups. This method involves applying a lateral shift to the beam reflected by the forward-pointing angle mirror after passing through the planar lens group, without changing the beam's exit angle. This allows the beam to exit from the center of the telescope pupil at a specified forward-pointing angle. However, due to the limited tilt angles of the planar lens group and the resulting lateral shift, it is only suitable for use within a narrow optical path adjustment range and is unable to meet the measurement requirements of high-precision interstellar laser interferometry. Summary of the Invention

[0006] The present invention provides an intersatellite laser interferometry measurement method with a front finger angle adjustment unit with minimal optical path change, which is used to solve the technical problem that existing intersatellite laser interferometry measurement schemes are difficult to achieve the emission of an outgoing light beam in a specified emission direction with minimal optical path change, and thus are difficult to meet the measurement requirements of high-precision intersatellite laser interferometry.

[0007] A first aspect of the present invention provides an intersatellite laser interferometry measurement method having a front finger angle adjustment unit with minimal optical path variation, wherein the method is applied to an intersatellite laser interferometry measurement device having a front finger angle adjustment unit with minimal optical path variation;

[0008] The measuring device includes two adjacent satellites, a proof mass, an optical platform, a telescope, a front angle adjustment unit, and a detector; the proof mass is placed inside each of the satellites so that the satellite rotates with the proof mass; the optical platform and the telescope are placed on each of the satellites; the front angle adjustment unit includes a laser for emitting a laser beam, a first precision rotating mirror, a second precision rotating mirror, and a telescope pupil; the laser, the first precision rotating mirror, the second precision rotating mirror, and the detector are all placed on the optical platform, and the telescope pupil is located at the junction of the optical platform and the telescope;

[0009] The measuring method comprises:

[0010] When the optical platform and the telescope rotate in response to the satellite's attitude change, a specified forward pointing angle is obtained in combination with the satellite's orbital position;

[0011] Calculating a first rotation angle and a second rotation angle according to the specified front finger angle;

[0012] controlling the first precision rotating mirror to rotate by a first rotation angle to adjust the incident point position of the laser beam on the first precision rotating mirror and reflect the laser beam to the second precision rotating mirror; controlling the second precision rotating mirror to rotate by a second rotation angle to adjust the incident point position of the laser beam on the second precision rotating mirror and reflect the laser beam to the telescope pupil, thereby adjusting the exit angle of the laser beam from the telescope pupil, so that the laser beam is emitted from the center of the telescope pupil and the exit direction is parallel to the specified front pointing angle direction;

[0013] Expanding the laser beam emitted from the pupil of the telescope through the telescope to obtain an outgoing beam, and directing the outgoing beam toward the satellite on the opposite side;

[0014] After the outgoing light beam is received by the satellite on the opposite side, a received light beam is obtained; after the received light beam passes through its telescope and enters the telescope pupil, the received light beam is incident on the detector surface and interferes with the local reference light to generate an interference signal;

[0015] By measuring the interference signal, the optical path change of the received light beam propagating between the two satellites is calculated, thereby achieving high-precision intersatellite laser interferometry measurement.

[0016] More specifically,

[0017] The calculation process of the first rotation angle is as follows:

[0018]

[0019] Where: represents the first rotation angle, represents the specified front finger angle, l1 represents the distance between the center of the reflection surface of the first precision rotating mirror and the center of the reflection surface of the second precision rotating mirror, and l2 represents the distance between the center of the reflection surface of the second precision rotating mirror and the center of the exit pupil.

[0020] More specifically,

[0021] The calculation process of the second rotation angle is as follows:

[0022]

[0023] Where: Indicates the second rotation angle.

[0024] More specifically,

[0025] During the rotation of the two precision mirrors, the change in the optical path of the beam With the specified front finger angle The relationship is shown as follows:

[0026] .

[0027] A second aspect of the present invention further provides an intersatellite laser interferometry device having a front angle adjustment unit with minimal optical path variation, the device comprising: two adjacent satellites, a proof mass, an optical platform, a telescope, a front angle adjustment unit, and a detector;

[0028] The inspection mass is placed inside each of the satellites so that the satellite rotates following the inspection mass;

[0029] The optical platform and the telescope are placed on each of the satellites;

[0030] The front finger angle unit includes a laser, a first precision rotating mirror, a second precision rotating mirror, a telescope pupil and a control device;

[0031] The laser, the first precision rotating mirror, the second precision rotating mirror and the detector are all placed on the optical platform, and the telescope pupil is located at the junction of the optical platform and the telescope;

[0032] The first precision rotating mirror is placed on the light-emitting side of the laser, and is used to receive the laser beam emitted by the laser and reflect the laser beam through the reflecting surface;

[0033] The second precision rotating mirror is placed on the light-emitting side of the first precision rotating mirror, and is used to receive the laser beam reflected from the first precision rotating mirror and reflect the laser beam to the telescope pupil through a reflecting surface;

[0034] The telescope pupil is placed on the light-emitting side of the second precision rotating mirror, for emitting the laser beam;

[0035] The control device is electrically connected to the first precision rotating mirror and the second precision rotating mirror, respectively, and is used to calculate a first rotation angle and a second rotation angle according to a required specified forward pointing angle when the optical platform and the telescope rotate following a change in the attitude of the satellite, and to control the first precision rotating mirror to rotate by the first rotation angle and the second precision rotating mirror to rotate by the second rotation angle, thereby adjusting an exit angle of the laser beam from the pupil of the telescope so that the laser beam is emitted from the center of the pupil of the telescope and the exit direction is parallel to the specified forward pointing angle;

[0036] The telescope is used to expand the laser beam emitted from the telescope pupil to obtain an outgoing beam, and to send the outgoing beam to the satellite on the opposite side; after receiving the outgoing beam sent by the satellite on the opposite side, a receiving beam is obtained, and the receiving beam is passed through the telescope pupil so that the receiving beam is reflected on the detector surface to cause interference.

[0037] More specifically, the first precision rotating mirror is placed at an angle of 45° to the propagation direction of the laser beam directed toward the first precision rotating mirror, and the second precision rotating mirror is placed at an angle of 45° to the propagation direction of the laser beam directed toward the second precision rotating mirror.

[0038] More specifically, the optical platform is further provided with a first beam splitter and a second beam splitter;

[0039] The first beam splitter is placed on the light-emitting side of the laser, and is used to split the laser beam emitted by the laser into a transmitted laser beam and a local reference light, direct the transmitted laser beam toward the first precision rotating mirror, and reflect the local reference light toward the second beam splitter;

[0040] The second beam splitter is configured to, after receiving the laser beam from the second precision rotating mirror, direct the laser beam from the second precision rotating mirror toward the telescope pupil and direct the local reference light toward the surface of the detector; and after receiving the received beam from the telescope pupil, direct the received beam toward the surface of the detector;

[0041] The detector is used to interfere the received light beam with the local reference light to generate an interference signal.

[0042] More specifically, the control device includes a computer, a first driving power supply, and a second driving power supply;

[0043] The computer is electrically connected to the first driving power supply and the second driving power supply respectively, and the first driving power supply is connected to the first precision rotating mirror, and the second driving power supply is connected to the second precision rotating mirror;

[0044] The computer is configured to calculate a first rotation angle and a second rotation angle according to a required specified forward pointing angle when the optical platform and the telescope rotate in response to a change in the attitude of the satellite, generate corresponding drive signals based on the first rotation angle and the second rotation angle, and send the drive signals to the first drive power supply and the second drive power supply, respectively;

[0045] The first driving power supply is configured to output a first driving voltage according to a received driving signal to drive the first precision rotating mirror to rotate according to a first rotation angle;

[0046] The second driving power supply is used to output a second driving voltage according to the received driving signal to drive the second precision rotating mirror to rotate according to a second rotation angle.

[0047] More specifically,

[0048] The calculation process of the first rotation angle is as follows:

[0049]

[0050] Where: represents the first rotation angle, represents the designated target exit angle of the laser beam from the exit pupil, l1 represents the distance between the center of the reflection surface of the first precision rotating mirror and the center of the reflection surface of the second precision rotating mirror, and l2 represents the distance between the center of the reflection surface of the second precision rotating mirror and the center of the exit pupil.

[0051] More specifically,

[0052] The calculation process of the second rotation angle is as follows:

[0053]

[0054] Where: Indicates the second rotation angle.

[0055] It can be seen from the above technical solutions that the present invention has the following advantages:

[0056] The present invention provides an intersatellite laser interferometry method with a front-point angle adjustment unit having minimal optical path variation, and the method is applied to an intersatellite laser interferometry device with a front-point angle adjustment unit having minimal optical path variation; wherein the method comprises: when an optical platform and a telescope rotate following a satellite's attitude change, obtaining a specified front-point angle in combination with the satellite's orbital position; calculating a first rotation angle and a second rotation angle based on the specified front-point angle; controlling a first precision rotating mirror to rotate by the first rotation angle to adjust the incident point position of a laser beam on the first precision rotating mirror and reflect the laser beam to a second precision rotating mirror; controlling a second precision rotating mirror to rotate by the second rotation angle to adjust the incident point position of the laser beam on the second precision rotating mirror and reflect the laser beam to a telescope pupil, thereby adjusting the exit angle of the laser beam from the telescope pupil, so that the laser beam is emitted from the center of the telescope pupil and the exit direction is parallel to the specified front-point angle direction;

[0057] The laser beam emitted from the pupil of the telescope is expanded by the telescope to obtain an outgoing beam, and the outgoing beam is emitted to the satellite on the opposite side; the outgoing beam is received by the satellite on the opposite side to obtain a receiving beam; after the receiving beam passes through its telescope and enters the telescope pupil, the receiving beam is incident on the detector surface and interferes with the local reference light to generate an interference signal; by measuring the interference signal, the change in the optical path of the receiving beam propagating between the two satellites is calculated, thereby realizing high-precision intersatellite laser interferometry measurement.

[0058] The present invention uses two precision rotating mirrors to cooperate with each other at the fore-angle adjustment unit to achieve the emission of a light beam from the center of the telescope pupil at a specified fore-angle with a small optical path change, thereby suppressing the optical path error to achieve high-precision intersatellite laser interferometry displacement measurement. This solves the technical problem that existing intersatellite laser interferometry measurement schemes are difficult to achieve the emission of the output light beam in a specified emission direction with extremely small optical path changes, and thus are difficult to meet the measurement requirements of high-precision intersatellite laser interferometry. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0060] Figure 1 A flowchart of the steps of an intersatellite laser interferometry measurement method for a front finger angle adjustment unit with minimal optical path variation provided by the present application;

[0061] Figure 2 Schematic diagram of the Tianqin spacecraft orbit provided for this application;

[0062] Figure 3 Schematic diagram of laser interferometry measurement between two satellites of the Tianqin Project using the intersatellite laser interferometry device provided in this application;

[0063] Figure 4 Schematic diagram of the initial stage of measurement of the front finger angle adjustment unit of a single satellite provided in this application;

[0064] Figure 5 Schematic diagram of the front pointing angle adjustment unit of a single satellite provided in this application using two precision rotating mirrors to adjust the beam pointing;

[0065] Figure 6 Schematic diagram of a single satellite's front angle adjustment unit provided in this application using only one precision rotating mirror to adjust the beam pointing;

[0066] Figure 7 Schematic diagram of the front pointing angle adjustment unit of a single satellite provided in this application using a precision rotating mirror combined with a lens group to adjust the beam pointing;

[0067] Among them, the accompanying drawings are marked as: computer 1, second driving power supply 2, second precision rotating mirror 3, telescope pupil 4, laser 5, first precision rotating mirror 6, first driving power supply 7, first precision rotating mirror reflection center 8, lens group 9, center of telescope pupil 10, fixed reflecting mirror 11, detector 12, inspection mass 13. DETAILED DESCRIPTION

[0068] Embodiments of the present invention provide a device and method for precise alignment of light beam pointing with minimal optical path variation, which are used to address the technical problem that existing laser interferometry measurement solutions are difficult to achieve better optical path error compensation while achieving the emission of a light beam in a specified emission direction, and thus are unable to meet the measurement requirements of space gravitational wave detection missions.

[0069] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0070] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0071] Unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed, removable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0072] See also Figure 1 The present invention provides an intersatellite laser interferometry measurement method having a front finger angle adjustment unit with minimal optical path change, and the method is applied to an intersatellite laser interferometry measurement device having a front finger angle adjustment unit with minimal optical path change.

[0073] For details, please refer to Figure 2-Figure 5 The intersatellite laser interferometry device with a minimal optical path variation front angle adjustment unit provided by the present invention includes two adjacent satellites, an optical platform, a telescope, a front angle adjustment unit, and a detector 12. The two satellites are identical, and a test mass 13 is placed inside each satellite. The satellites protect the test mass 13 from external forces and rotate in accordance with the movement and orientation of the test mass 13.

[0074] An optical platform and a telescope are placed on each satellite; the forward pointing angle unit includes a laser 5 for emitting a laser beam, a first precision rotating mirror 6, a second precision rotating mirror 3, a telescope pupil 4 and a control device; the laser 5, the first precision rotating mirror 6, the second precision rotating mirror 3 and the detector 12 are all placed on the optical platform, and the telescope pupil 4 is located at the junction of the optical platform and the telescope; the optical platform and the telescope change their attitude synchronously with the satellite.

[0075] In the fore-finger angle unit, the first precision rotating mirror 6 is placed on the light emitting side of the laser 5, used for receiving the laser beam emitted by the laser 5 and reflecting the laser beam through the reflecting surface; the second precision rotating mirror 3 is placed on the light emitting side of the first precision rotating mirror 6, used for receiving the laser beam reflected from the first precision rotating mirror 6 and reflecting the laser beam to the telescope pupil 4 through the reflecting surface; the telescope pupil 4 is placed on the light emitting side of the second precision rotating mirror 3, used for emitting the laser beam.

[0076] The telescope is used for expanding the laser beam emitted by the telescope pupil 4 to obtain an emitted beam, and shooting the emitted beam to the satellite on the opposite side; after receiving the emitted beam sent by the satellite on the opposite side, a received beam is obtained, and the received beam is passed through the telescope pupil 4, so that the received beam is reflected on the surface of the detector 12 to interfere.

[0077] In the fore-finger angle unit, the first precision rotating mirror 6 is placed on the light emitting side of the laser 5, used for receiving the laser beam emitted by the laser 5 and reflecting the laser beam through the reflecting surface; the second precision rotating mirror 3 is placed on the light emitting side of the first precision rotating mirror 6, used for receiving the laser beam reflected from the first precision rotating mirror 6 and reflecting the laser beam to the telescope pupil 4 through the reflecting surface; the telescope pupil 4 is placed on the light emitting side of the second precision rotating mirror 3, used for emitting the laser beam.

[0078] Taking one of the satellites as an example, in the process of high-precision inter-satellite laser interferometric measurement, the fore-finger angle adjusting unit needs to adjust the emitted beam to be emitted from the center of the telescope pupil 4 at a specified fore-finger angle, if the emitted beam of the fore-finger angle adjusting unit is not emitted from the center of the telescope pupil 4, the emitted beam may be truncated by the telescope pupil 4, thereby affecting the inter-satellite laser interferometric measurement.

[0079] In the initial stage of measurement, in order to reduce the initial optical path error caused by the eccentric emission of the laser beam, and reduce the complexity of the control device for adjusting the rotation of the two precision rotating mirrors, the first precision rotating mirror 6 and the second precision rotating mirror 3 can be adjusted to the initial angle zero position, that is, the placement angle of the first precision rotating mirror 6 is 45° with the propagation direction of the laser beam shot to the first precision rotating mirror 6, and the placement angle of the second precision rotating mirror 33 is 45° with the propagation direction of the laser beam shot to the second precision rotating mirror 3. Then, when the optical platform does not rotate, the laser 5 emits the laser beam to the center of the reflecting surface of the first precision rotating mirror 6, the laser beam reflected by the reflecting surface of the first precision rotating mirror 6 is shot to the center of the reflecting surface of the second precision rotating mirror 3, and the laser beam reflected by the reflecting surface of the second precision rotating mirror 3 is shot to the center of the emitted pupil 4, at this time, the emitted beam is emitted vertically to the plane of the telescope pupil 4.

[0080] During the adjustment of the output beam direction, if only one precision rotating mirror is used to adjust the output beam direction, the output beam cannot be guaranteed to be emitted from the center of the telescope pupil 4. For example, see Figure 6 ,exist Figure 6 In the embodiment, only the first precision rotating mirror 6 is used to realize rotation adjustment; in contrast, the present invention proposes the use of two precision rotating mirrors in cooperation with each other, whereby the first precision rotating mirror 6 and the second precision rotating mirror 3 are respectively rotated by a certain angle, so that the outgoing light beam is emitted from the center of the telescope pupil 4 at a specified fore-pointing angle with a smaller optical path change, thereby achieving high-precision interstellar laser interferometry measurement.

[0081] In a specific embodiment, see Figure 2 , the device is also provided with a spectrometer, which realizes beam splitting and changes the optical path of the beam through the spectrometer, so that the received light beam and the reference local light are directed to the surface of the detector 12 to achieve interference. Specifically, a first spectrometer and a second spectrometer are also installed on the optical platform; the first spectrometer is placed on the light-emitting side of the laser 5, and is used to split the laser beam emitted by the laser 5 into a transmitted laser beam and a local reference light, and direct the transmitted laser beam to the first precision rotating mirror 6, and reflect the local reference light to the second spectrometer; the second spectrometer is used to direct the laser beam of the second precision rotating mirror 3 to the telescope pupil 4 after receiving the laser beam from the second precision rotating mirror 3, and direct the local reference light to the surface of the detector 12; after receiving the received beam from the telescope pupil 4, the received beam is directed to the surface of the detector 12;

[0082] The detector 12 is used to interfere the received light beam with the local reference light to generate an interference signal. By measuring the interference signal, the change in the optical path of the light beam propagating between the two satellites, that is, the change in distance, can be calculated, thereby realizing high-precision intersatellite laser interferometry measurement.

[0083] Therefore, the present invention can realize the laser beam being emitted in a specified direction and the emitted beam being emitted in a specified forward pointing angle direction through the precise coordination of two precision rotating mirrors, realize real-time dynamic compensation with a small optical path change, compensate the laser beam in real time at the telescope pupil 4 and emit it in a specified forward pointing angle direction, maintain the stability of the optical path, and achieve the effect of suppressing the optical path error to achieve high-precision interstellar laser interferometry displacement measurement.

[0084] In a specific embodiment, see Figure 5The control device includes a computer 1, a first driving power supply 7, and a second driving power supply 2; the computer 1 is electrically connected to the first driving power supply 7 and the second driving power supply 2, respectively, and the first driving power supply 7 is connected to the first precision rotating mirror 6, and the second driving power supply 2 is connected to the second precision rotating mirror 3; the computer 1 is used to calculate the first rotation angle and the second rotation angle according to the required specified front pointing angle when the optical platform and the telescope rotate in response to the attitude change of the satellite, generate corresponding driving signals based on the first rotation angle and the second rotation angle, and send the driving signals to the first driving power supply 7 and the second driving power supply 2, respectively;

[0085] The first driving power supply 7 is configured to output a first driving voltage based on a received driving signal to drive the first precision rotating mirror 6 to rotate at a first rotation angle. The second driving power supply 2 is configured to output a second driving voltage based on a received driving signal to drive the second precision rotating mirror 3 to rotate at a second rotation angle. It will be appreciated that using two driving power supplies to precisely drive the two precision rotating mirrors provides more stable current and voltage, maintaining precise rotation of the precision mirrors and thereby better meeting specific scientific objectives and mission requirements.

[0086] like Figure 4 As shown in the figure, when the optical platform rotates following the satellite attitude change, the first rotation angle of the first precision rotating mirror 6 is and the second rotation angle of the second precision rotating mirror 3 With the specified front finger angle The following relationship should be satisfied:

[0087]

[0088] Wherein, l1 represents the distance between the center of the reflection surface of the first precision rotating mirror 6 and the center of the reflection surface of the second precision rotating mirror 3, and l2 represents the distance between the center of the reflection surface of the second precision rotating mirror 3 and the center of the telescope pupil 4.

[0089] Therefore, during the rotation of the two precision mirrors, the change in the laser beam optical path is With the specified front finger angle The relationship is shown as follows:

[0090]

[0091] In general intersatellite laser interferometry, for example, the precision measurement of the Earth's gravity field based on intersatellite laser interferometry, the beam pointing requirement requires that the beam exit jitter angle range reach about 10urad. 、 They are 50mm and 200mm respectively. According to the above formula, the rotation angles of the two precision rotating mirrors can be calculated 、 They are 0.02mrad and 0.01mrad respectively, and the corresponding optical path change is 5×10 -11 m, which is far smaller than the current demand for measuring interstellar distance changes at the nanometer level.

[0092] In the Tianqin space gravitational wave detection plan, the beam output jitter angle range is 10nrad, assuming 、 They are 50mm and 200mm respectively. According to the above formula, the rotation angles of the two precision rotating mirrors can be calculated 、 The values ​​are 20nrad and 25nrad respectively, and the corresponding optical path length change is 2.8×10 -17 m, which is also much smaller than the picometer-level measurement requirements for gravitational wave detection in the Tianqin space.

[0093] In the conventional front finger angle adjustment scheme, such as Figure 7 As shown, the present invention also provides a solution of using a precision rotating mirror and a fixed reflector 11 to cooperate with each other. Figure 7 In the figure, the laser 5, the first precision rotating mirror 6, the lens group 9, and the telescope pupil 4 are all located on the optical platform and rotate with the optical platform; the outgoing light beam emitted by the laser 5 is incident on the reflection center 8 of the first precision rotating mirror 6, and the first precision rotating mirror 6 is placed at an angle of 45° to the propagation direction of the outgoing light beam directed to the first precision rotating mirror 6; the outgoing light beam is reflected by the reflection surface of the first precision rotating mirror 6 and then directed to the fixed reflector 11, and the fixed reflector 11 is placed at an angle of 45° to the propagation direction of the outgoing light beam directed to the fixed reflector 11; the outgoing light beam is reflected by the fixed reflector 11 and passes through the lens group 9 to the center of the telescope pupil 4.

[0094] Computer 1 outputs a driving signal to the first driving power supply 7. The first driving power supply 7 outputs a specified voltage to drive the first precision rotating mirror 6 to rotate so as to adjust the direction of the outgoing light beam, while the fixed reflector 11 can translate a certain displacement forward and backward along the normal direction of the reflector; the two pupils of the lens group 9 are respectively designed at the reflection center 8 of the first precision rotating mirror 6 and the center 10 of the telescope pupil 4. According to Fermat's principle, the optical path of the light beam propagating between these two points remains unchanged. Therefore, it can be guaranteed that in the process of adjusting the direction of the outgoing light beam by the first precision rotating mirror 6, theoretically, no optical path change occurs, thereby achieving the purpose of the outgoing light beam being emitted from the center of the telescope pupil 4 at a specified forward pointing angle. The optical path change of the light beam in this example The rotation angle of the first precision mirror 6 The relationship is shown as follows:

[0095]

[0096] Where l1 represents the distance between the center of the reflection surface of the first precision rotating mirror 6 and the center of the fixed reflector 11, and l2 represents the distance between the center of the fixed reflector 11 and the pupil 4 of the telescope. Then when the beam emission angle range is 10nrad, assuming 、 are 50mm and 200mm respectively. According to the above formula, the corresponding optical path change can be calculated to be 1.5×10 -9 m, which cannot meet the picometer-level measurement requirements for gravitational wave detection in the Tianqin space.

[0097] Therefore, through the cooperation of two precision rotating mirrors, this device can achieve the output light beam from the center of the telescope pupil 4 at a specified fore-pointing angle with a very small optical path change, thereby suppressing the optical path error and realizing the purpose of high-precision interstellar laser interferometry displacement measurement.

[0098] See also Figure 6 The present invention provides a method for precise alignment of light beams with minimal optical path variation, comprising:

[0099] Step 101: When the optical platform and the telescope rotate in response to the satellite's attitude change, a designated forward pointing angle is obtained in combination with the satellite's orbital position.

[0100] Step 102, calculating a first rotation angle and a second rotation angle according to a specified front finger angle;

[0101] It can be understood that, according to the required designated front finger angle, the present invention calculates the first rotation angle of the first precision rotating mirror and the second rotation angle of the second precision rotating mirror corresponding to the designated front finger angle.

[0102] Specifically, when the optical platform rotates following the satellite attitude change, the first rotation angle of the first precision rotating mirror 6 is and the second rotation angle of the second precision rotating mirror 3 With the specified front finger angle The following relationship should be satisfied:

[0103]

[0104] Wherein, l1 represents the distance between the center of the reflection surface of the first precision rotating mirror 6 and the center of the reflection surface of the second precision rotating mirror 3, and l2 represents the distance between the center of the reflection surface of the second precision rotating mirror 3 and the center of the telescope pupil 4.

[0105] Step 103: Control the first precision rotating mirror to rotate by a first rotation angle to adjust the incident point position of the laser beam on the first precision rotating mirror and reflect the laser beam to the second precision rotating mirror; control the second precision rotating mirror to rotate by a second rotation angle to adjust the incident point position of the laser beam on the second precision rotating mirror and reflect the laser beam to the telescope pupil, thereby adjusting the exit angle of the laser beam from the telescope pupil, so that the laser beam is emitted from the center of the telescope pupil and the exit direction is parallel to the specified front pointing angle direction;

[0106] Step 104: Expand the laser beam emitted from the telescope pupil through the telescope to obtain an outgoing beam, and direct the outgoing beam toward the satellite on the opposite side.

[0107] Step 105: After the outgoing beam is received by the satellite on the opposite side, a received beam is obtained; after the received beam passes through its telescope and enters the telescope pupil, the received beam is incident on the detector surface and interferes with the local reference beam to generate an interference signal;

[0108] Step 106 , by measuring the interference signal, the optical path change of the receiving light beam propagating between the two satellites is calculated, thereby achieving high-precision intersatellite laser interferometry measurement.

[0109] In intersatellite laser interferometry, when the optical platform rotates following the change of satellite attitude, the present invention calculates the rotation angle of the first precision rotating mirror and the rotation angle of the second precision rotating mirror according to the required specified front angle through the front angle unit, so as to drive the two precision rotating mirrors to cooperate with each other for precise rotation, and compensates the light beam in real time at the telescope pupil with minimal optical path change and emits it in the specified front angle direction, so that the satellite can emit the light beam to the satellite on the opposite side through the telescope. After the satellite on the opposite side receives the receiving light beam, it enters the telescope pupil through the telescope, passes through the spectrometer, is incident on the detector surface, and interferes with the local reference light. Therefore, by measuring the interference signal, the optical path change of the light beam propagating between the two satellites, that is, the distance change, can be calculated, thereby realizing high-precision intersatellite laser interferometry.

[0110] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An intersatellite laser interferometry measurement method with a front angle adjustment unit with minimal optical path change, characterized in that: The method is applied to an intersatellite laser interferometry device having a front finger angle adjustment unit with minimal optical path variation; The measuring device includes two adjacent satellites, a proof mass, an optical platform, a telescope, a front angle adjustment unit, and a detector; the proof mass is placed inside each of the satellites so that the satellite rotates with the proof mass; the optical platform and the telescope are placed on each of the satellites; the front angle adjustment unit includes a laser for emitting a laser beam, a first precision rotating mirror, a second precision rotating mirror, and a telescope pupil; the laser, the first precision rotating mirror, the second precision rotating mirror, and the detector are all placed on the optical platform, and the telescope pupil is located at the junction of the optical platform and the telescope; The measuring method comprises: When the optical platform and the telescope rotate in response to the satellite's attitude change, a specified forward pointing angle is obtained in combination with the satellite's orbital position; Calculating a first rotation angle and a second rotation angle according to the specified front finger angle; controlling the first precision rotating mirror to rotate by a first rotation angle to adjust the incident point position of the laser beam on the first precision rotating mirror and reflect the laser beam to the second precision rotating mirror; controlling the second precision rotating mirror to rotate by a second rotation angle to adjust the incident point position of the laser beam on the second precision rotating mirror and reflect the laser beam to the telescope pupil, thereby adjusting the exit angle of the laser beam from the telescope pupil, so that the laser beam is emitted from the center of the telescope pupil and the exit direction is parallel to the specified front pointing angle direction; Expanding the laser beam emitted from the pupil of the telescope through the telescope to obtain an outgoing beam, and directing the outgoing beam toward the satellite on the opposite side; After the outgoing light beam is received by the satellite on the opposite side, a received light beam is obtained; after the received light beam passes through its telescope and enters the telescope pupil, the received light beam is incident on the detector surface and interferes with the local reference light to generate an interference signal; By measuring the interference signal, the optical path change of the received light beam propagating between the two satellites is calculated, thereby achieving high-precision intersatellite laser interferometry measurement.

2. The intersatellite laser interferometry method according to claim 1, characterized in that: The calculation process of the first rotation angle is as follows: Where: represents the first rotation angle, represents the specified front pointing angle, l1 represents the distance between the center of the reflecting surface of the first precision rotating mirror and the center of the reflecting surface of the second precision rotating mirror, and l2 represents the distance between the center of the reflecting surface of the second precision rotating mirror and the center of the exit pupil.

3. The intersatellite laser interferometry method according to claim 2, characterized in that: The calculation process of the second rotation angle is as follows: Where: Indicates the second rotation angle.

4. The intersatellite laser interferometry method according to claim 3, characterized in that: During the rotation of the two precision mirrors, the change in the optical path of the beam With the specified front finger angle The relationship is shown as follows: 。 5. An intersatellite laser interferometry device with a front angle adjustment unit for minimal optical path variation, characterized in that: The device includes: two adjacent satellites, a proof mass, an optical platform, a telescope, a front angle adjustment unit and a detector; The inspection mass is placed inside each of the satellites so that the satellite rotates following the inspection mass; The optical platform and the telescope are placed on each of the satellites; The front finger angle unit includes a laser, a first precision rotating mirror, a second precision rotating mirror, a telescope pupil and a control device; The laser, the first precision rotating mirror, the second precision rotating mirror and the detector are all placed on the optical platform, and the telescope pupil is located at the junction of the optical platform and the telescope; The first precision rotating mirror is placed on the light-emitting side of the laser, and is used to receive the laser beam emitted by the laser and reflect the laser beam through the reflecting surface; The second precision rotating mirror is placed on the light-emitting side of the first precision rotating mirror, and is used to receive the laser beam reflected from the first precision rotating mirror and reflect the laser beam to the telescope pupil through a reflecting surface; The telescope pupil is placed on the light-emitting side of the second precision rotating mirror, for emitting the laser beam; The control device is electrically connected to the first precision rotating mirror and the second precision rotating mirror, respectively, and is used to calculate a first rotation angle and a second rotation angle according to a required specified forward pointing angle when the optical platform and the telescope rotate following a change in the attitude of the satellite, and to control the first precision rotating mirror to rotate by the first rotation angle and the second precision rotating mirror to rotate by the second rotation angle, thereby adjusting an exit angle of the laser beam from the pupil of the telescope so that the laser beam is emitted from the center of the pupil of the telescope and the exit direction is parallel to the specified forward pointing angle; The telescope is used to expand the laser beam emitted from the telescope pupil to obtain an outgoing beam, and to send the outgoing beam to the satellite on the opposite side; after receiving the outgoing beam sent by the satellite on the opposite side, a receiving beam is obtained, and the receiving beam is passed through the telescope pupil so that the receiving beam is reflected on the detector surface to cause interference.

6. The intersatellite laser interferometry device according to claim 5, characterized in that: The first precision rotating mirror is placed at an angle of 45° to the propagation direction of the laser beam directed toward the first precision rotating mirror, and the second precision rotating mirror is placed at an angle of 45° to the propagation direction of the laser beam directed toward the second precision rotating mirror.

7. The intersatellite laser interferometry device according to claim 6, characterized in that: The optical platform is also equipped with a first beam splitter and a second beam splitter; The first beam splitter is placed on the light-emitting side of the laser, and is used to split the laser beam emitted by the laser into a transmitted laser beam and a local reference light, direct the transmitted laser beam toward the first precision rotating mirror, and reflect the local reference light toward the second beam splitter; The second beam splitter is configured to, after receiving the laser beam from the second precision rotating mirror, direct the laser beam from the second precision rotating mirror toward the telescope pupil and direct the local reference light toward the surface of the detector; and after receiving the received beam from the telescope pupil, direct the received beam toward the surface of the detector; The detector is used to interfere the received light beam with the local reference light to generate an interference signal.

8. The intersatellite laser interferometry device according to claim 6, characterized in that: The control device includes a computer, a first driving power supply and a second driving power supply; The computer is electrically connected to the first driving power supply and the second driving power supply respectively, and the first driving power supply is connected to the first precision rotating mirror, and the second driving power supply is connected to the second precision rotating mirror; The computer is configured to calculate a first rotation angle and a second rotation angle according to a required specified forward pointing angle when the optical platform and the telescope rotate in response to a change in the attitude of the satellite, generate corresponding drive signals based on the first rotation angle and the second rotation angle, and send the drive signals to the first drive power supply and the second drive power supply, respectively; The first driving power supply is configured to output a first driving voltage according to a received driving signal to drive the first precision rotating mirror to rotate according to a first rotation angle; The second driving power supply is used to output a second driving voltage according to the received driving signal to drive the second precision rotating mirror to rotate according to a second rotation angle.

9. The intersatellite laser interferometry device according to claim 6, characterized in that: The calculation process of the first rotation angle is as follows: Where: represents the first rotation angle, represents the designated target exit angle of the laser beam from the exit pupil, l1 represents the distance between the center of the reflection surface of the first precision rotating mirror and the center of the reflection surface of the second precision rotating mirror, and l2 represents the distance between the center of the reflection surface of the second precision rotating mirror and the center of the exit pupil.

10. The intersatellite laser interferometry device according to claim 6, characterized in that: The calculation process of the second rotation angle is as follows: Where: Indicates the second rotation angle.

Images