Angular velocity measuring device based on optical suspension harmonic oscillator

Abstract

The invention discloses an angular velocity measuring device based on an optical suspension harmonic oscillator, which belongs to the field of inertial measurement technology and optical tweezers technology, and comprises an imaging camera, a first band-pass filter, a first non-polarization splitting prism, a first objective lens, a second objective lens and a coaxial light source which are coaxially arranged in sequence, the first objective lens and the second objective lens are both mounted in the vacuum cavity and are confocal; the emergent direction of the capture laser is perpendicular to the gravity direction, and a first dichroscope is mounted at the intersection point of the emergent direction of the capture laser and the z-axis; the emitting direction of the modulated laser is the x-axis positive direction and is coplanar with the z-axis; the center of the first non-polarization splitting prism is arranged at the intersection point of the z-axis and the incident direction of the modulated laser; the second dichroscope is arranged between the coaxial light source and the vacuum cavity; and the second band-pass optical filter and the four-quadrant detector are sequentially arranged in the x-axis negative direction of the second dichroscope. According to the invention, high vacuum environment capture and angular velocity measurement of the optical suspension harmonic oscillator are realized.

Description

Technical Field

[0001] This invention belongs to the fields of inertial measurement technology and optical tweezers technology, specifically relating to an angular velocity measurement device based on an optically levitated resonator. Background Technology

[0002] The interaction between a highly focused laser field and micro / nano-scale particles generates gradient and scattering forces, forming a three-dimensional trapping potential well for the particles. By analyzing information such as the center-of-mass motion and spatial orientation of the particles suspended in the trap, highly sensitive measurements of physical quantities (e.g., torque, gas damping, electric field) can be achieved. In the field of inertial measurement, the measurement of the carrier's angular velocity and acceleration is the core of the inertial measurement system, achieved by gyroscopes and accelerometers, respectively. By integrating these quantities, the system can autonomously calculate the carrier's attitude, velocity, and position without relying on external signals, forming a fully autonomous inertial navigation system. This is an indispensable fundamental tool in fields such as deep space exploration and deep-sea submersible navigation.

[0003] Accelerometers primarily utilize Newton's second law. When a carrier experiences acceleration, the mass block connected by elastic forces experiences an "inertial force." The acceleration can be measured by the relationship between the displacement of the mass block and the input force. Particles suspended in an optical trap can be considered as being bound by a three-dimensional, non-contact elastic optical force. Therefore, many optically suspended particle acceleration measurement schemes have been designed and implemented based on the analogy of accelerometer principles.

[0004] Gyroscopes are mainly classified into electromechanical, optical, and atomic types according to their working principle. Electromechanical gyroscopes utilize the Coriolis force introduced by a high-speed rotor or resonator in response to the angular velocity input of a carrier to achieve rate or position gyroscopes. Optical gyroscopes primarily utilize the Sagnac effect (in a rotating closed optical path, two beams of light propagating in opposite directions will produce a phase difference; this effect is widely used in modern fiber optic and laser gyroscopes for measuring rotational angular velocity), that is, detecting the change in the position of interference fringes as the carrier's angular velocity input changes to calculate the input angular velocity. Atomic gyroscopes are mainly divided into hot atom spin-free exchange relaxation gyroscopes and cold atom interferometric gyroscopes. Currently, rotor angular velocity measurement has been achieved based on optical levitation, which mainly utilizes a single beam to levitate a high-speed rotor, and by analyzing the correspondence between the rotor speed and the carrier's angular velocity input, the carrier's angular velocity is measured. Other optical levitation angular velocity measurement schemes are still in the theoretical verification stage.

[0005] Traditional electromechanical gyroscopes require the design of drive and detection structures, and their mechanical friction losses limit their accuracy and lifespan. Optical gyroscopes are expensive and struggle to achieve both high precision and miniaturization. Therefore, developing a novel high-precision angular velocity measurement device that achieves high-precision measurement of a carrier's angular velocity while also possessing low cost and miniaturization potential is a pressing technical challenge in the field of inertial measurement. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] An angular velocity measurement device based on an optically levitated resonator includes:

[0008] An imaging camera, a first bandpass filter, a first non-polarizing beam splitter, a first objective lens, a second objective lens, and a coaxial light source are arranged in sequence on the same axis.

[0009] The tube of the first objective lens is parallel to the direction of gravity, and the exit pupil is vertically upward. The positive z-axis is defined as vertically upward. The exit pupil of the second objective lens is in the negative z-axis direction. Both the first and second objectives are installed in a vacuum chamber and are confocal.

[0010] The capturing laser is a Gaussian single-mode continuous laser source used to provide a levitation light field. Its emission direction is perpendicular to the direction of gravity. The incident direction of the capturing laser is defined as the positive x-axis, and the positive y-axis is determined by the right-hand coordinate system. A first dichroic mirror is installed at the intersection of the emission direction of the capturing laser and the z-axis. The reflecting surface of the first dichroic mirror faces the positive z-axis and makes an angle of 45° with the z-axis.

[0011] The modulated laser is a Gaussian single-mode continuous laser source used to provide the driving optical field. The output direction of the modulated laser is the positive x-axis and is coplanar with the z-axis.

[0012] The center of the first unpolarized beam splitter is located at the intersection of the z-axis and the incident direction of the modulated laser.

[0013] Also includes:

[0014] The second dichroic mirror is placed between the coaxial light source and the vacuum cavity, with its center coinciding with the z-axis and its reflecting surface facing the negative z-axis direction, making an angle of 45° with the z-axis.

[0015] The second bandpass filter and the four-quadrant detector are sequentially positioned in the negative x-axis direction of the second dichroic mirror.

[0016] The present invention has the following beneficial effects:

[0017] 1. This invention achieves the capture of optically suspended resonators in a high-vacuum environment through a non-contact levitation method using an optical field. The system operates without mechanical friction, resulting in low energy dissipation and a high quality factor.

[0018] 2. This invention is built through optical path integration, resulting in a simple system structure, low installation difficulty, no need for complex optical path alignment, and an imaging system, which is beneficial for system assembly, adjustment, and monitoring of working status, and has the potential for miniaturization.

[0019] 3. This invention achieves particle suspension, actuation, and signal detection through all-optical means, without the need to introduce external electromagnetic fields, effectively isolating external interference and possessing integrated advantages.

[0020] 4. This invention achieves the same resonant frequency between the driving shaft and the detection shaft of the resonator by precisely adjusting the light field of the captured beam, which can effectively amplify the precession response signal of the resonator, resulting in high detection sensitivity and good timeliness. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the angular velocity measurement device based on an optically levitated harmonic oscillator according to the present invention, wherein 1-imaging camera, 2-first bandpass filter, 3-first unpolarized beam splitter prism, 4-first dichroic mirror, 5-vacuum cavity, 6-first objective lens, 7-second objective lens, 8-second dichroic mirror, 9-second bandpass filter, 10-four-quadrant detector, 11-coaxial light source;

[0022] Figure 2 This is a schematic diagram of the optical levitation resonator drive of the present invention, wherein 12 is the exit pupil of the first objective lens and 13 is the exit pupil of the second objective lens;

[0023] Figure 3 This is a schematic diagram of the angular velocity input response of the optically suspended resonator sensitive carrier of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Considering that the optical force experienced by the particles suspended in the optical trap can be analogized to a three-dimensional Hooke contactless spring, by precisely adjusting the light field of the captured beam and ensuring the circular symmetry of the beam interface, the stiffness of the optical trap in the two radially orthogonal directions can be made almost identical, which can reduce the dissipation of driving energy and amplify the precession response of the input angular velocity of the detection axis. Therefore, this invention designs an angular velocity measurement device based on an optically suspended resonant oscillator. By resonantly driving the suspended particles in the optical trap, high-precision measurement of the carrier's angular velocity can be achieved, while also possessing the potential for low cost and miniaturization.

[0026] like Figure 1As shown, the angular velocity measurement device based on an optically levitated resonator of the present invention includes an imaging camera 1, a first bandpass filter 2, a first non-polarizing beam splitter 3, a first objective lens 6, a second objective lens 7, and a coaxial light source 11 arranged coaxially in sequence. The tube of the first objective lens 6 is parallel to the direction of gravity, and its exit pupil is vertically upward. The exit pupil direction of the first objective lens 6 is taken as the positive z-axis direction (the positive z-axis direction is vertically upward), and the exit pupil direction of the second objective lens 7 is taken as the negative z-axis direction. Both the first objective lens 6 and the second objective lens 7 are installed in a vacuum cavity 5 and are confocal. The capturing laser is a Gaussian single-mode continuous laser source used to provide a levitation light field. Its emission direction is perpendicular to the direction of gravity. The incident direction of the capturing laser is defined as the positive x-axis direction, and the positive y-axis direction is determined by a right-hand coordinate system. A first dichroic mirror 4 is installed at the intersection of the captured laser emission direction and the z-axis. Its reflecting surface faces the positive z-axis direction, and the angle between it and the z-axis is 45°. The modulated laser is a Gaussian single-mode continuous laser source used to provide the driving optical field. The output direction of the modulated laser is in the positive x-axis direction and coplanar with the z-axis. The center of the first unpolarized beam splitter 3 is located at the intersection of the z-axis and the incident direction of the modulated laser. The second dichroic mirror 8 is installed between the coaxial light source 11 and the vacuum cavity 5, with its center coinciding with the z-axis and its reflecting surface facing the negative z-axis direction at an angle of 45° (depending on the reflection direction). The second bandpass filter 9 and the four-quadrant detector 10 are sequentially arranged in the negative x-axis direction of the second dichroic mirror 8. Sufficient margins must be allowed between the imaging camera 1, the first bandpass filter 2, the first unpolarized beam splitter 3, and the first dichroic mirror 4, and between the coaxial light source 11, the second dichroic mirror 8, and the second bandpass filter 9, to avoid mechanical interference and ensure that there is no obstruction or additional aberration introduced by edge diffraction within the light-passing aperture.

[0027] The capturing laser is a Gaussian single-mode continuous laser source with adjustable intensity, used to focus the capturing laser and form a stable three-dimensional optical trap to achieve particle capture, and to provide the initial elastic optical trap for the drive axis and detection axis. Precision beam shaping ensures the beam quality factor in any radial direction. To ensure full utilization of the numerical aperture of the first objective lens 6, the diameter of the captured laser spot is adjusted to be slightly larger than the entrance pupil diameter of the first objective lens 6, as close to 1 as possible. The wavelength of the laser reflected by the first dichroic mirror 4 is the same as that of the captured laser. The first dichroic mirror 4 is used to adjust the direction of the captured laser incident on the first objective lens 6, ensuring that the incident direction of the captured laser is coaxial with the first objective lens 6 to generate a stable three-dimensional captured light field for particles, and to transmit the modulated laser and imaging background light. The vacuum cavity 5 is used to provide a vacuum environment, reduce air damping, and improve the system quality factor. The first objective lens 6 is a captured objective lens with a numerical aperture of not less than 0.8, a numerical aperture range of 0.8 to 0.95, and a magnification of 100x.

[0028] like Figure 1As shown, after the direction of the captured laser incident on the first objective lens 6 is adjusted, optically suspended particles are loaded using either atomization or piezoelectric ceramic support. The optically suspended particles are dielectric particles with a radius of 1-25 micrometers, such as silicon dioxide. When the size of the optically suspended particles is small (less than 10 micrometers), atomization can be used to atomize and spray out the liquid containing the optically suspended particles. When the optically suspended particles suspended in the air approach the optical trap, they will fall into the three-dimensional optical trap due to scattering and gradient forces. When the size of the optically suspended particles is large (greater than 10 micrometers), piezoelectric ceramic support can be used. The optically suspended particles are placed in a transparent sheet connected to a piezoelectric ceramic. The transparent sheet can be a cover glass, etc. The plane of the transparent sheet is parallel to the exit pupil plane of the first objective lens 6, and its height is slightly lower than the center of the captured laser focusing optical trap. After the piezoelectric ceramic is activated to allow the particles to overcome van der Waals forces and fall into the optical trap, the piezoelectric ceramic operation is immediately stopped, completing the loading of the optically suspended particles.

[0029] like Figure 1 As shown, the modulated laser is a Gaussian single-mode continuous laser source with adjustable azimuth or intensity, used to provide resonant driving force for the optically levitated particles in the driving axis direction. The orientation of the first unpolarized beam splitter 3 is adjusted to ensure that the incident direction of the driving laser emitted by the modulated laser for the resonance of the optically levitated particles is coaxial with the first objective lens 6. The driving mode for the optically levitated particles is either fixed-point beam driving or focused scanning driving. The wavelength of the modulated laser differs from that of the capturing laser to pass through the first dichroic mirror 4, and its spot diameter is slightly larger than the entrance pupil diameter of the first objective lens 6. After being reflected by the first unpolarized beam splitter 3, the modulated laser passes through the first dichroic mirror 4 and is focused by the first objective lens 6 to generate a three-dimensional driving optical trap.

[0030] The driving mode for the optically levitated particles can be either fixed-beam driving or focused scanning driving. When the driving mode is fixed-beam driving, the driving laser consists of two modulated laser beams, each with modulated intensity, oriented in the positive and negative x-axis directions, respectively. The height of the modulated laser light trap center is the same as the height of the capturing laser light trap center, and the distance from the capturing laser center does not exceed one particle size. When the driving mode is focused scanning driving, the driving laser consists of a single modulated laser beam with adjustable orientation, oriented in the positive and negative x-axis directions (the orientation of the single modulated laser beam can vary between the positive and negative x-axis directions).

[0031] like Figure 1As shown, the coaxial light source 11 uses a light source with a wavelength different from that of the captured laser and the modulated laser. It is focused onto the center of the capture range by the second objective lens 7 to provide illumination for the imaging field of view. The magnification of the second objective lens 7 is selected as 10x or 20x (or an aspherical lens with a numerical aperture in the range of 0.2 to 0.6 is used). The imaging camera 1 can be a color visible light band camera or an infrared band camera depending on the specific optical path design, and is equipped with a variable focal length lens. The magnification is adjusted by the variable focal length lens, and it is combined with the first objective lens 6 to form a microscope system, providing an optical path-aided alignment reference and real-time monitoring of the capture status of light-suspended particles. The passable band of the first bandpass filter 2 is matched with that of the coaxial light source 11 to filter out the captured laser and the modulated laser, ensuring that only the field of view light of the coaxial light source 11 is received, thereby providing image information of the capture area.

[0032] The wavelength of the laser reflected by the second dichroic mirror 8 is the same as the wavelength of the captured laser. The forward-scattered light from the optically suspended particles is collected by the second objective lens 7 and emitted in parallel, then reflected by the second dichroic mirror 8 to the four-quadrant detector 10. The four-quadrant detector 10 is used to convert the forward-scattered light signal from the optically suspended particles into a voltage signal and extract the triaxial centroid displacement information of the optically suspended particles in real time. The backscattered light from the optically suspended particles may contain the driving laser; therefore, the second bandpass filter 9 is used to filter out the interfering light. When the centroid position of the optically suspended particles deviates from the captured light field, the intensity difference between the upper and lower halves, the intensity difference between the left and right halves, and the total intensity sensed by the four-quadrant detector 10 are proportional to the displacement of the centroid of the optically suspended particles along the x-axis, y-axis, and z-axis, respectively.

[0033] Figure 2 The diagram shows a schematic of the optical levitation resonator drive of the present invention, where the exit pupil 12 of the first objective lens and the exit pupil 13 of the second objective lens are identified. When the optically levitation particles are captured, the vacuum cavity 5 is evacuated, and a modulated laser is activated to drive the particles resonantly. When the drive mode is fixed-point beam drive, the drive light consists of two modulated laser beams whose intensity can be modulated only, and are fixed at... Figure 2 The A and B directions are both located in the xz plane and on opposite sides of the x-axis, forming a small angle with the z-axis. This ensures that the center of the modulated laser focusing beam is at a certain distance from the center of the capturing laser, a distance not exceeding the size of one optically suspended particle. Furthermore, the height of the modulated laser optical trap center is the same as the height of the capturing laser optical trap center. Due to the optical trap force, the optically suspended particles suspended in the capturing laser optical trap are simultaneously subjected to the levitation force of the capturing laser. and the traction force of modulated laser and The two modulated laser beams are directed towards the positive and negative x-axis directions, respectively, forcing the particles to move in the direction of the modulated laser along the x-axis. Intensity modulation can be achieved using acousto-optic modulators, electro-optic modulators / liquid crystals with polarizers, etc. The modulation frequency is the resonant frequency of the optically suspended particles, and the intensity can be modulated using sine or square wave signals. The peak-to-peak value is adjusted to the maximum intensity of the driving laser. The two modulated laser beams have a 180° phase difference, causing the optically suspended particles to resonate under the alternating traction force of the two modulated laser beams. When the driving mode is focused scanning, the driving light consists of a single beam of azimuthally adjustable modulated laser. High-frequency modulation of the driving laser direction introduces the resonant driving force. Azimuth modulation can be achieved using acousto-optic deflectors, piezoelectric deflectors, etc. The modulation frequency is the same as the resonant frequency of the optically suspended particles, and the modulation azimuth is along directions A and B, which have a small angle with the x-axis. The laser modulation distance is the same from the origin at its maximum in both the positive and negative x-axis directions, and does not exceed the size of one optically suspended particle.

[0034] Figure 3 The diagram illustrates the angular velocity input response of the optically levitated resonator sensing carrier according to the present invention. When the carrier is stationary, the optically levitated resonator resonates along the radial drive axis (x-axis) under the action of the driving light. When the carrier moves with angular velocity, the input angular velocity introduces a Coriolis force, causing the optically levitated resonator to precess. Its resonant direction changes from the driving direction of the driving laser to the precession direction, and the precession angle is proportional to the angular velocity. The centroid motion signal of the optically levitated resonator can be extracted in real time by the detection system. The angular velocity of the carrier is measured by real-time detection of the spatial position (x-axis displacement amplitude, y-axis displacement amplitude) and angular changes of the optically levitated resonator.

[0035] The above description is merely an embodiment of the present invention and does not limit the scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the protection scope of the present invention.

[0036] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. An angular velocity measuring device based on an optically levitated resonator, characterized in that, include: An imaging camera, a first bandpass filter, a first non-polarizing beam splitter, a first objective lens, a second objective lens, and a coaxial light source are arranged in sequence on the same axis. The tube of the first objective lens is parallel to the direction of gravity, and the exit pupil is vertically upward. The positive z-axis is defined as vertically upward. The exit pupil of the second objective lens is in the negative z-axis direction. Both the first and second objectives are installed in a vacuum chamber and are confocal. The capturing laser is a Gaussian single-mode continuous laser source used to provide a levitation light field. Its emission direction is perpendicular to the direction of gravity. The incident direction of the capturing laser is defined as the positive x-axis, and the positive y-axis is determined by the right-hand coordinate system. A first dichroic mirror is installed at the intersection of the emission direction of the capturing laser and the z-axis. The reflecting surface of the first dichroic mirror faces the positive z-axis and makes an angle of 45° with the z-axis. The modulated laser is a Gaussian single-mode continuous laser source used to provide the driving optical field. The output direction of the modulated laser is the positive x-axis and is coplanar with the z-axis. The center of the first unpolarized beam splitter is located at the intersection of the z-axis and the incident direction of the modulated laser. Also includes: The second dichroic mirror is placed between the coaxial light source and the vacuum cavity, with its center coinciding with the z-axis and its reflecting surface facing the negative z-axis direction, making an angle of 45° with the z-axis. The second bandpass filter and the four-quadrant detector are sequentially positioned in the negative x-axis direction of the second dichroic mirror.

2. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, The first dichroic mirror reflects the same wavelength as the captured laser. The first dichroic mirror is used to adjust the direction of the captured laser incident on the first objective lens, ensuring that the incident direction of the captured laser is coaxial with the first objective lens to generate a stable three-dimensional captured light field for microparticles, and transmits the modulated laser and imaging background light.

3. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, The first objective is a capture objective with a numerical aperture of not less than 0.

8.

4. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, After the direction of the captured laser incident first objective lens is adjusted, light-suspended microparticles are loaded using atomization or piezoelectric ceramic support.

5. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, The modulated laser is a Gaussian single-mode continuous laser source with adjustable azimuth or intensity, used to provide resonant driving force for light-suspended particles in the driving axis direction; the wavelength of the modulated laser is different from that of the captured laser to pass through the first dichroic mirror, and the diameter of the modulated laser spot is slightly larger than the entrance pupil diameter of the first objective lens; after being reflected by the first unpolarized beam splitter, the modulated laser passes through the first dichroic mirror and is focused by the first objective lens to generate a three-dimensional driving optical trap.

6. The angular velocity measuring device based on an optically levitated resonator according to claim 5, characterized in that, The driving modes for the optically suspended particles are fixed-beam driving or focused scanning driving. When the driving mode is fixed-beam driving, the driving laser consists of two modulated lasers whose intensity can be modulated only. The directions of the two modulated lasers are the positive and negative directions of the x-axis, respectively. The center height of the modulated laser light trap is the same as the center height of the capturing laser light trap, and the distance from the center of the capturing laser does not exceed one particle size. When the driving mode is focused scanning driving, the driving laser consists of a single modulated laser whose orientation can be adjusted, with the direction being the positive and negative directions of the x-axis.

7. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, The coaxial light source is a light source with a wavelength different from that of the capturing laser and the modulated laser. It is focused to the center of the capturing range through the second objective lens to provide illumination for the imaging field of view.

8. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, The second objective lens has a magnification of 10 or 20x, or the second objective lens can be replaced by an aspherical lens with a numerical aperture in the range of 0.2 to 0.

6.

9. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, The passable band of the first bandpass filter is matched with the coaxial light source to filter out the capture laser and modulated laser, ensuring that only the field light of the coaxial light source is received, thereby providing image information of the capture area.

10. The angular velocity measuring device based on an optically levitated resonator according to claim 1, characterized in that, The wavelength of the laser reflected by the second dichroic mirror is the same as the wavelength of the captured laser. The forward scattered light of the optically suspended particles is collected by the second objective lens and emitted in parallel. It is then reflected by the second dichroic mirror to the four-quadrant detector. The four-quadrant detector is used to convert the forward scattered light signal of the optically suspended particles into a voltage signal and extract the triaxial centroid displacement information of the optically suspended particles in real time. The second bandpass filter is used to filter out interference light; when the centroid position of the light-suspended particle shifts to capture the light field, the light intensity difference between the upper and lower halves, the light intensity difference between the left and right halves, and the total light intensity sensed by the four-quadrant detector are proportional to the displacement of the centroid of the light-suspended particle along the x-axis, y-axis, and z-axis, respectively.

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