Inter-satellite laser interference measuring method with extremely small optical path change front finger angle adjusting unit

Abstract

The invention discloses an inter-satellite laser interference measurement method with an extremely small optical path change front finger angle adjusting unit, the method is applied to an inter-satellite laser interference measurement device, and the device comprises two adjacent satellites, a test mass, an optical platform, a telescope, the front finger angle adjusting unit and a detector; the satellites rotate along with the test mass, and each satellite is provided with an optical platform and a telescope; the front finger angle unit comprises a laser used for emitting laser beams, a first precise rotating mirror, a second precise rotating mirror and a telescope pupil. The laser, the first precise rotating mirror, the second precise 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; according to the invention, the front finger angle adjusting unit is matched with the two precise rotating mirrors, so that the light beam is emitted from the pupil center of the telescope at a specified front finger angle with small optical path change, and the purpose of suppressing the optical path error so as to realize high-precision inter-satellite laser interference 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 intersatellite laser interferometry measurement method with a front finger angle adjustment unit with extremely small optical path change. Background Art

[0002] The Tianqin Project is expected to have a height of about 1×10 8 Three spacecraft are deployed in an Earth orbit of 1.7×10 meters, forming an arm with a length of about 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 intersatellite laser interferometer, 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. 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 by, the distance between the two test masses of the same arm of the two satellites will change slightly. Therefore, the Tianqin Project uses a laser interferometer measurement system to accurately read the change in the distance between the test masses. This distance is measured in three stages: the distance between the local test mass and the local optical platform, the distance between the opposite optical platform and the opposite test mass, and the distance between the local optical platform and the opposite optical platform. The first two are read out using a test mass optical reading interferometer, and the latter is read out using a long-baseline intersatellite laser interferometer. The outgoing beam of the long-baseline intersatellite laser interferometer is emitted from the laser of the local optical platform. After the outgoing beam is pointed at the front finger angle by the front finger angle adjustment unit, it is emitted from the center of the telescope exit pupil and is received by the detector of the opposite optical platform through intersatellite long-distance transmission. The front finger angle adjustment unit will generate significant TTL coupling noise in the process of adjusting the 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 angle 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 reflection 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 change caused by ±3.4urad is 2.31e -11 m. This is unacceptable for intersatellite laser ranging tasks that require the optical path stability to be less than the pm level. Therefore, it is necessary to design a fore-angle adjustment unit with extremely small optical path changes to achieve the output beam to be emitted from the center of the telescope pupil at a specified fore-angle, thereby achieving high-precision intersatellite laser interferometry.

[0005] At present, the space gravitational wave detection mission LISA is expected to use a method of adjusting the optical path of multiple tiltable plane lens groups to solve the error of the optical path change of the beam caused by the deflection of the front-pointing angle mirror. The light beam reflected by the front-pointing angle mirror will undergo a lateral translation after passing through the plane lens group without changing the beam exit angle, thereby achieving the exit from the center of the telescope pupil at a specified front-pointing angle. However, due to the limited tilt angle of the plane lens group, the lateral offset generated is limited, so it is only suitable for situations with a small optical path adjustment range, and it is difficult to meet the measurement requirements of high-precision intersatellite 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 extremely small optical path change, which is used to solve the technical problem that the existing intersatellite laser interferometry measurement schemes are difficult to achieve the emission of an outgoing light beam in a specified emission direction with extremely small 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 change, the method being applied to an intersatellite laser interferometry measurement device having a front finger angle adjustment unit with minimal optical path change;

[0008] The measuring device comprises two adjacent satellites, a test mass, an optical platform, a telescope, a front-pointing angle adjustment unit and a detector; the test mass is placed inside each of the satellites so that the satellite rotates following the test mass; the optical platform and the telescope are placed on each of the satellites; the front-pointing angle 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 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 following the attitude change of the satellite, a specified forward pointing angle is obtained in combination with the orbital position of the satellite;

[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 finger angle direction;

[0013] Expanding the laser beam emitted from the pupil of the telescope through the telescope to obtain an output beam, and emitting the output 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 pupil of the telescope, 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 change in the optical path of the receiving 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] The second aspect of the present invention also provides an intersatellite laser interferometry device with a front finger angle adjustment unit with minimal optical path change, the device comprising: two adjacent satellites, a test mass, an optical platform, a telescope, a front finger angle adjustment unit and a detector;

[0028] The inspection mass is placed inside each of the satellites, so that the satellite rotates along with 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 a 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, and is used to emit 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 for calculating 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 following the attitude change of the satellite, controlling the first precision rotating mirror to rotate the first rotation angle and controlling the second precision rotating mirror to rotate the second rotation angle, so as to adjust the 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 front pointing angle;

[0036] The telescope is used to expand the laser light beam emitted from the pupil of the telescope to obtain an outgoing light beam, and to emit the outgoing light beam to the satellite on the opposite side; after receiving the outgoing light beam sent by the satellite on the opposite side, a receiving light beam is obtained, and the receiving light beam is passed through the pupil of the telescope, so that the receiving light 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 to the first precision rotating mirror, and reflect the local reference light to the second beam splitter;

[0040] The second beam splitter is used to, after receiving the laser beam from the second precision rotating mirror, direct the laser beam from the second precision rotating mirror to the telescope pupil and direct the local reference light to the surface of the detector; after receiving the receiving beam from the telescope pupil, direct the receiving beam to 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 source and a second driving power source;

[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 used for calculating a first rotation angle and a second rotation angle according to a required specified front pointing angle when the optical platform and the telescope rotate following the attitude change of the satellite, generating corresponding drive signals based on the first rotation angle and the second rotation angle, and sending the drive signals to the first drive power supply and the second drive power supply respectively;

[0045] The first driving power supply is used 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-pointing angle adjustment unit with minimal optical path change, and the method is applied to an intersatellite laser interferometry device with a front-pointing angle adjustment unit with minimal optical path change; wherein the method comprises: when an optical platform and a telescope rotate following the attitude change of a satellite, a specified front-pointing angle is obtained in combination with the orbital position of the satellite; a first rotation angle and a second rotation angle are calculated according to the specified front-pointing angle; a first precision rotating mirror is controlled to rotate by a 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; a second precision rotating mirror is controlled 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 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-pointing angle direction;

[0057] The laser beam emitted from the pupil of the telescope is expanded by the telescope to obtain an outgoing beam, and then the outgoing beam is emitted to the satellite on the opposite side; after the outgoing beam is received by the satellite on the opposite side, a receiving beam is obtained; after the receiving beam passes through its telescope and enters the pupil of the telescope, the receiving beam is incident on the surface of the detector 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.

[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 achieving the purpose of suppressing the optical path error to realize high-precision intersatellite laser interferometry displacement measurement, thereby solving the technical problem that the existing intersatellite laser interferometry measurement schemes are difficult to achieve the emission of the output light beam in a specified emission direction with an extremely small optical path change, 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0060] Figure 1 A flow chart of the steps of an intersatellite laser interferometry measurement method of a front finger angle adjustment unit with minimal optical path change provided in 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 by the intersatellite laser interferometry measurement device provided in this application;

[0063] Figure 4 A 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 A schematic diagram of a front pointing angle adjustment unit for a single satellite provided in this application using two precision rotating mirrors to coordinately adjust the beam pointing;

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

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

[0067] Among them, the figure markings are: 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] The embodiments of the present invention provide a device and method for precise alignment of light beam pointing with extremely small optical path variation, which are used to solve the technical problem that existing laser interferometry measurement schemes are difficult to achieve better optical path error compensation while realizing the light beam to be emitted in a specified emission direction, and thus are difficult 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 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", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0071] Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to 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 extremely small optical path change, and the method is applied to an intersatellite laser interferometry measurement device having a front finger angle adjustment unit with extremely small optical path change.

[0073] For details, please refer to Figure 2-Figure 5 The intersatellite laser interferometry measuring device with a front finger angle adjustment unit with minimal optical path change provided by the present invention comprises two adjacent satellites, an optical platform, a telescope, a front finger angle adjustment unit and a detector 12; wherein the two satellites are completely identical, and a test mass 13 is placed inside the satellites, and the satellites protect the test mass 13 from external forces and rotate following the movement and orientation of the test mass 13;

[0074] An optical platform and a telescope are placed on each satellite; the front 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; wherein, the optical platform and the telescope change their attitude synchronously with the satellite.

[0075] In the front finger angle unit, the first precision rotating mirror 6 is placed on the light exit side of the laser 5, and is used to receive the laser beam emitted by the laser 5 and reflect the laser beam through the reflection surface; the second precision rotating mirror 3 is placed on the light exit side of the first precision rotating mirror 6, and is used to receive the laser beam reflected from the first precision rotating mirror 6, and reflect the laser beam to the telescope pupil 4 through the reflection surface; the telescope pupil 4 is placed on the light exit side of the second precision rotating mirror 3, and is used to emit the laser beam;

[0076] The telescope is used to expand the laser beam emitted from the telescope pupil 4 to obtain an outgoing beam, and then 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 4, so that the receiving beam is reflected on the surface of the detector 12 to cause interference.

[0077] The front pointing angle unit in the present invention adjusts the front pointing angle of the outgoing light beam through two precision rotating mirrors; specifically, the control device is electrically connected to the first precision rotating mirror 6 and the second precision rotating mirror 3, respectively, and is used to obtain the required specified front pointing angle in combination with the orbital position of the satellite when the optical platform and the telescope rotate following the attitude change of the satellite, and calculate the first rotation angle and the second rotation angle according to the required specified front pointing angle, control the first precision rotating mirror 6 to rotate the first control angle and control the second precision rotating mirror 3 to rotate the second rotation angle, thereby adjusting the exit angle of the laser light beam from the telescope pupil 4, so that the laser light beam is emitted from the center of the telescope pupil 4 and the emission direction is parallel to the specified front pointing angle.

[0078] Taking one of the satellites as an example, during the high-precision intersatellite laser interferometry measurement process, the front finger angle adjustment unit needs to adjust the outgoing light beam to specify the front finger angle to be emitted from the center of the telescope pupil 4. If the outgoing light beam of the front finger angle adjustment unit does not emit from the center of the telescope pupil 4, the outgoing light beam may be cut off by the telescope pupil 4, thereby affecting the intersatellite laser interferometry 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 to rotate and adjust 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° to the propagation direction of the laser beam directed to the first precision rotating mirror 6, and the placement angle of the second precision rotating mirror 33 is 45° to the propagation direction of the laser beam directed to the second precision rotating mirror 3. Then, when the optical platform does not rotate, the laser 5 emits a laser beam incident on the center of the reflection surface of the first precision rotating mirror 6, and the laser beam is reflected by the reflection surface of the first precision rotating mirror 6 and then emitted to the center of the reflection surface of the second precision rotating mirror 3. The laser beam reflected by the reflection surface of the second precision rotating mirror 3 is emitted to the center of the exit pupil 4, and the exit beam is emitted perpendicular to the plane of the telescope pupil 4.

[0080] During the process of adjusting the direction of the outgoing beam, if only one precision rotating mirror is used to adjust the direction of the outgoing beam, the outgoing beam cannot be guaranteed to be emitted from the center of the telescope pupil 4. For example, please refer to 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 that cooperate with each other, and 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 intersatellite laser interferometry.

[0081] In a specific embodiment, see Figure 2 , the device is also provided with a spectroscope, which realizes beam splitting and changes the optical path of the beam through the spectroscope, so that the received beam and the reference local light are directed to the surface of the detector 12 to achieve interference. Specifically, the optical platform is also equipped with a first spectroscope and a second spectroscope; the first spectroscope 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 spectroscope; the second spectroscope 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 front-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 front-pointing angle direction, maintain the stability of the optical path, and achieve the effect of suppressing the optical path error to achieve high-precision intersatellite 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 following 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 used to output a first driving voltage according to the received driving signal to drive the first precision rotating mirror 6 to rotate according to the first rotation angle; the second driving power supply 2 is used to output a second driving voltage according to the received driving signal to drive the second precision rotating mirror 3 to rotate according to the second rotation angle. It can be understood that using two driving power supplies to accurately drive the two precision rotating mirrors respectively can provide more stable current and voltage, maintain the precise rotation of the precision rotating mirror, and thus better meet specific scientific goals and task 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 the beam emission jitter angle range to 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 much smaller than the current requirement 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 change is 2.8×10 -17 m, which is also much smaller than the picometer-level measurement required for gravitational wave detection in Tianqin space.

[0093] In the conventional front finger angle adjustment scheme, Figure 7 As shown, the present invention also provides a solution of using a precision rotating mirror and a fixed reflecting mirror 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 the Fermat principle, the optical path of the light beam propagating between these two points remains unchanged. Therefore, it can be ensured 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 emitting the outgoing light beam from the center of the telescope pupil 4 at a specified forward pointing angle. The change in the optical path of the light beam in this example The rotation angle of the first precision rotating 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 50 mm and 200 mm 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, the device can realize the emission of the outgoing light beam from the center of the telescope pupil 4 at a specified fore-pointing angle with a very small optical path change, thereby achieving the purpose of suppressing the optical path error to realize high-precision intersatellite laser interferometry displacement measurement.

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

[0099] Step 101, when the optical platform and the telescope rotate following the attitude change of the satellite, a specified forward pointing angle is obtained in combination with the orbital position of the satellite;

[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 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 specified front finger angle according to the required specified 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, 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 pupil of the telescope, thereby adjusting the 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 direction of the specified front finger angle;

[0106] Step 104, the laser beam emitted from the pupil of the telescope is expanded by the telescope to obtain an output beam, and the output beam is emitted to the satellite on the opposite side;

[0107] Step 105, 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 pupil of the telescope, the received light beam is incident on the detector surface and interferes with the local reference light to generate an interference signal;

[0108] Step 106, by measuring the interference signal, the change in the optical path of the receiving light beam propagating between the two satellites is calculated, thereby realizing 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 finger angle through the front finger 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 a very small optical path change and emits it in the specified front finger 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, so that the optical path change of the light beam propagating between the two satellites, that is, the distance change, can be solved by measuring the interference signal, 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 aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may 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 finger 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 comprises two adjacent satellites, a test mass, an optical platform, a telescope, a front-pointing angle adjustment unit and a detector; the test mass is placed inside each of the satellites so that the satellite rotates following the test mass; the optical platform and the telescope are placed on each of the satellites; the front-pointing angle 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 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 following the attitude change of the satellite, a specified forward pointing angle is obtained in combination with the orbital position of the satellite; 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 finger angle direction; Expanding the laser beam emitted from the pupil of the telescope through the telescope to obtain an output beam, and emitting the output 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 pupil of the telescope, 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 change in the optical path of the receiving 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 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.

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 finger angle adjustment unit with minimal optical path change, 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 along with 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 a 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, and is used to emit 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 for calculating 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 following the attitude change of the satellite, controlling the first precision rotating mirror to rotate the first rotation angle and controlling the second precision rotating mirror to rotate the second rotation angle, so as to adjust the 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 front pointing angle; The telescope is used to expand the laser light beam emitted from the pupil of the telescope to obtain an outgoing light beam, and to emit the outgoing light beam to the satellite on the opposite side; after receiving the outgoing light beam sent by the satellite on the opposite side, a receiving light beam is obtained, and the receiving light beam is passed through the pupil of the telescope, so that the receiving light 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 to the first precision rotating mirror, and reflect the local reference light to the second beam splitter; The second beam splitter is used to, after receiving the laser beam from the second precision rotating mirror, direct the laser beam from the second precision rotating mirror to the telescope pupil and direct the local reference light to the surface of the detector; after receiving the receiving beam from the telescope pupil, direct the receiving beam to 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 source and a second driving power source; 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 used for calculating a first rotation angle and a second rotation angle according to a required specified front pointing angle when the optical platform and the telescope rotate following the attitude change of the satellite, generating corresponding drive signals based on the first rotation angle and the second rotation angle, and sending the drive signals to the first drive power supply and the second drive power supply respectively; The first driving power supply is used 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