Membrane mirror system with slow beam deflection

Abstract

Embodiments of the present disclosure relate to MEMS mirror systems with slow light beam deflection. A light beam deflection system is configured to transmit a light beam with a time-varying output deflection angle. The system includes a first resonant structure configured to oscillate about a first rotational axis with a first resonant frequency, a second resonant structure configured to oscillate about a second rotational axis with a second resonant frequency, wherein the first rotational axis is parallel to the second rotational axis, and the first resonant frequency and the second resonant frequency are different and define a predetermined frequency difference, and a drive circuit configured to generate a first drive signal to drive the first resonant structure while additionally generating a second drive signal to drive the second resonant structure, such that the output deflection angle of the light beam oscillates according to a beat pattern of a beat wave, extreme values of the beat wave being modulated and defined by a periodic envelope.

Description

Technical Field

[0001] Embodiments of this disclosure relate to MEMS mirror systems, and more particularly to MEMS mirror systems with slow beam deflection. Background Technology

[0002] Beam deflection using microelectromechanical systems (MEMS) mirrors enables numerous applications, including but not limited to optical detection and ranging (LIDAR), micro-projector displays, cameras (visual, hyperspectral, or thermal), spectrometers, laser material processing, and more. The angular velocity (i.e., rate of change of angle) of beam deflection is crucial in some applications where measurement times are long and compromises are not feasible. Frequency-modulated continuous wave (FMCW) LiDAR is an example requiring relatively slow beam deflection speeds. In FMCW applications, the beam is transmitted as a continuous wave rather than, for example, a discrete optical pulse, and one or more MEMS mirrors move (i.e., oscillate) continuously to perform beam steering. Thus, the continuous wave is continuously deflected.

[0003] Slow beam deflection using MEMS mirrors typically means operating the mirror at a low resonant frequency or in a quasi-static manner. Both options have their drawbacks. Low-frequency MEMS mirrors are susceptible to shock and vibration, and also result in lower resolution compared to fast-resonant MEMS mirrors. Similarly, if a quasi-static mirror has a low characteristic frequency, it may also be susceptible to shock and vibration, leading to lower resolution compared to fast-resonant MEMS mirrors. Alternatively, the design of a quasi-static mirror might require a large actuation structure to provide sufficient force to move the mirror, implemented on a rigid suspension, to achieve a high characteristic frequency. However, increasing the size of the actuation structure is undesirable, as it increases the overall volume of the MEMS mirror device.

[0004] Therefore, an improved system and method may be needed that can utilize one or more fast resonant MEMS mirrors to provide slow beam deflection. Summary of the Invention

[0005] One or more embodiments provide a beam deflection system configured to transmit a beam with a time-varying output deflection angle. The beam deflection system includes: a first resonant structure configured to oscillate about a first rotation axis at a first resonant frequency; a second resonant structure configured to oscillate about a second rotation axis at a second resonant frequency; wherein the first rotation axis is parallel to the second rotation axis, and wherein the first and second resonant frequencies are different and define a predetermined frequency difference; and a driver circuit configured to generate a first drive signal to drive the first resonant structure about the first rotation axis at the first resonant frequency, and simultaneously generate a second drive signal to drive the second resonant structure about the second rotation axis at the second resonant frequency, such that the output deflection angle of the beam oscillates according to a beat pattern of a beat wave, the extreme amplitude of which is modulated and defined by a periodic envelope.

[0006] One or more embodiments provide a beam deflection system configured to transmit a beam with a time-varying output deflection angle. The beam deflection system includes a microelectromechanical system (MEMS) device and driving circuitry. The MEMS device includes: an external rotating fixed frame; an internal oscillating frame suspended from the external rotating fixed frame, wherein the internal oscillating frame is a resonant structure configured to oscillate relative to the external rotating fixed frame at a first resonant frequency about a first rotation axis; and a resonant mirror suspended from the internal oscillating frame, wherein the resonant mirror is configured to oscillate relative to the internal oscillating frame at a second resonant frequency about a second rotation axis, wherein the first and second rotation axes coincide, and wherein the first and second resonant frequencies are different and define a predetermined frequency difference. The driving circuitry is configured to generate a first driving signal to drive the internal oscillating frame about the first rotation axis at the first resonant frequency, and simultaneously generate a second driving signal to drive the resonant mirror about the second rotation axis at the second resonant frequency, such that the output deflection angle of the beam oscillates according to a beat pattern of a beat wave, the extreme amplitude of which is modulated and defined by a periodic envelope. Attached Figure Description

[0007] The embodiments are described herein with reference to the accompanying drawings.

[0008] Figure 1A and Figure 1B This is a schematic block diagram of a resonant MEMS mirror scanning system according to one or more embodiments;

[0009] Figure 2 An illustration is provided according to one or more embodiments. Figure 1A The side view of the deflection system of the resonant MEMS mirror scanning system shown in the figure;

[0010] Figure 3AThe illustration shows a portion of the angular trajectory of the output deflection angle θout according to one or more embodiments;

[0011] Figure 3B As just one possible example, a portion of the angular trajectory of the output deflection angle θout is illustrated when the first resonant frequency f1 is set to 2kHz, the second resonant frequency f2 is set to 1.975kHz, and the angular amplitude A is set to 7.5°.

[0012] Figure 3C The diagram shows... Figure 3B The amplified portion of the beat wave is shown below;

[0013] Figure 4A As just one possible example, a portion of the angular trajectory of the output deflection angle θout is illustrated when the first resonant frequency f1 is set to 2kHz, the second resonant frequency f2 is set to 1.950kHz, and the angular amplitude A is set to 7.5°.

[0014] Figure 4B The diagram shows... Figure 4A The amplified portion of the beat wave shown; and

[0015] Figure 5 The illustration shows a MEMS scanning device according to one or more embodiments. Detailed Implementation

[0016] In the following, various embodiments will be described in detail with reference to the accompanying drawings. It should be noted that these embodiments are for illustrative purposes only and should not be construed as limiting. For example, while an embodiment may be described as including multiple features or elements, this should not be construed as indicating that all such features or elements are necessary to implement the embodiment. Rather, in other embodiments, some features or elements may be omitted, or alternative features or elements may be used instead. Furthermore, in addition to the features or elements explicitly shown and described, other features or elements, such as conventional components of a sensor device, may be provided.

[0017] Unless otherwise specifically indicated, features from different embodiments may be combined to form other embodiments. Variations or modifications described with respect to one embodiment may also be applied to other embodiments. In some instances, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments.

[0018] Furthermore, equivalent or similar elements, or elements with equivalent or similar functionality, are designated with equivalent or similar reference numerals in the following description. Since identical or functionally equivalent elements in the drawings are given the same reference numerals, repeated descriptions of elements with the same reference numerals can be omitted. Therefore, the descriptions provided for elements with the same or similar reference numerals are interchangeable.

[0019] Unless otherwise stated, the connections or couplings between the elements shown in the accompanying drawings or described herein can be wire-based connections or wireless connections. Furthermore, such connections or couplings can be direct connections or couplings without additional intermediate elements, or indirect connections or couplings with one or more additional intermediate elements, provided that the general purpose of the connection or coupling remains essentially unchanged, such as transmitting a signal or transmitting information.

[0020] In this disclosure, ordinal expressions such as "first," "second," etc., can modify various elements. However, such elements are not limited to the above expressions. For example, the above expressions do not limit the order and / or importance of elements. The above expressions are only used to distinguish one element from other elements. For example, the first box and the second box indicate different boxes, but they are both boxes. As another example, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element without departing from the scope of this disclosure.

[0021] The embodiments relate to light emitters and light emitter systems configured to emit continuous wave beams (e.g., FMCW beams) according to a scanning or directional pattern. The beams include visible light, infrared (IR) light, or other types of illumination signals. In some applications, transmitted light can be backscattered by an object toward the system, where the backscattered light is detected by a sensor. The sensor can convert the received backscattered light into an electrical signal, such as a current or voltage signal, which can be further processed by the system to generate object data and / or an image.

[0022] For example, in a LiDAR (Light Detection and Ranging) system, a light source transmits a beam into the field of view, and the light is reflected from one or more objects through backscattering. For continuous wave modulation, such as that used for frequency-modulated continuous wave (FMCW) beams, the wave detected after reflection has a deflected frequency and / or phase relative to the emitted beam, and this deflection is proportional to the distance from the reflecting object or surface. Therefore, the distance can be determined based on the measured deflection. This contrasts with pulse modulation, where the system measures the distance to a 3D object by measuring the absolute time it takes for a light pulse to travel from the light source to the 3D scene and back after reflection.

[0023] Pixel arrays can be used to detect and measure reflected light beams. For example, a photodetector array receives reflections from an object illuminated by light, and signal processing circuitry measures frequency or phase shifts based on the detected reflections. The differences in frequency or phase shifts across multiple pixels in the pixel array can then be used to create a digital 3D representation of the environment or generate other sensor data.

[0024] Scanning can illuminate a scene in a continuous scanning manner. By emitting beams in different scanning directions, an area called the field of view can be scanned, and objects within that area can be detected and imaged. Therefore, the field of view is defined by the scanning plane with a projection center.

[0025] Figure 1A and Figure 1B These are schematic block diagrams of fast resonant MEMS mirror scanning systems 100A and 100B according to one or more embodiments.

[0026] Specifically, the scanning system 100A includes two one-dimensional (1D) resonant MEMS mirrors 12 and 14, which are used to steer or otherwise deflect the beam according to a continuous scanning pattern. In one or more embodiments described herein, the MEMS mirrors 12 and 14 oscillate about their respective axes, which are arranged parallel to each other. Thus, two or more resonant MEMS mirrors oscillating about optically coupled or closely arranged parallel axes can be used for beam steering, particularly for transmitting the beam with a time-varying output deflection angle. For example, the output deflection angle can be defined by a maximum positive angle (e.g., +15°) and a maximum negative angle (e.g., -15°), whereby the output deflection angle of the beam oscillates between these two extreme values.

[0027] In this configuration, one MEMS mirror is configured to oscillate at a first resonant frequency f1, while the other MEMS mirror is configured to oscillate at a second resonant frequency f2, different from the first resonant frequency f1. The two MEMS mirrors 12 and 14 form a beam deflection system that produces a slowly moving angular beam trajectory (i.e., a slow rate of angular change) during certain “slow-movement” periods or intervals of the output deflection angle scanning mode. The “slow” “rate of angular change” is below a predetermined threshold.

[0028] The angular beam trajectory (i.e., output deflection angle) generated by two fast-resonant MEMS mirrors 12 and 14 driven at different resonant frequencies around a parallel rotation axis comprises a slowly moving envelope oscillating at beat frequency and a fast-moving oscillating trajectory beneath the envelope. The slow-motion region (along the envelope) can be used for measurements requiring slow motion (such as FMCWLIDAR).

[0029] In contrast, the scanning system 100B includes a single 1D MEMS mirror 14, implemented using a gimbal frame used to steer or otherwise deflect the beam according to a continuous scanning pattern. Further details will follow, and this gimbal frame includes an outer rotating fixed frame, an internal oscillating frame suspended from the outer rotating fixed frame, and the MEMS mirror 14 suspended from the internal oscillating frame. Both the MEMS mirror 14 and the internal oscillating frame are resonant structures, oscillating about their respective axes of rotation at different resonant frequencies (e.g., resonant frequencies f1 and f2), which coincide with each other.

[0030] The angular beam trajectory (i.e., output deflection angle) generated by driving two fast resonant structures (i.e., the internal oscillating frame and the MEMS mirror 14) at different resonant frequencies around parallel (i.e., coincident) rotational axes comprises a slowly moving envelope oscillating at beat frequency and a fast-moving oscillating trajectory beneath the envelope. The slow-moving region (along the envelope) can be used for measurements requiring slow motion (such as FMCW LIDAR).

[0031] Therefore, the above beam deflection system can be used with a separate optically coupled MEMS mirror ( Figure 1A Alternatively, it can be implemented using a single MEMS mirror within a gimbal frame comprising two pairs of suspension structures and two resonant frequencies, but with only one coincident axis of rotation. Figure 1B In both cases, a control loop is used to bring the two resonant structures to resonance with the desired amplitude and resonant frequency. In some cases, another control loop can be used to tune the resonant frequency to obtain the desired frequency difference between the resonant frequencies f1 and f2.

[0032] MEMS mirrors 12 and 14 are mechanically movable mirrors (i.e., MEMS micromirrors) integrated on a semiconductor chip. Both MEMS mirrors 12 and 14 are suspended by a corresponding pair of suspension structures attached to a rotating fixed frame connected to the semiconductor chip. The rotating fixed frame surrounds its MEMS mirror, and the pair of suspension structures extends axially from the frame to the MEMS mirror. The pair of suspension structures of MEMS mirror 12 defines a first resonant scanning axis 13. Similarly, the pair of suspension structures of MEMS mirror 14 defines a second resonant scanning axis 15.

[0033] Therefore, the MEMS mirror according to the embodiments described herein is configured to oscillate via rotation about a single resonant scanning axis (i.e., a 1D MEMS mirror). The oscillation of the MEMS mirror on the scanning axis can thus be performed between two predetermined extreme deflection angles (e.g., + / - 15 degrees). The beam deflection device or system is configured to control the direction of the beam in at least one dimension (e.g., in the horizontal x-direction or the vertical y-direction).

[0034] exist Figure 1A In the example shown, two 1D MEMS mirrors 12 and 14 are used to deflect a light beam in one dimension. MEMS mirror 12 includes a first resonant scanning axis 13, which allows it to deflect the light according to a first deflection angle θ1. Similarly, MEMS mirror 14 includes a second resonant scanning axis 15 extending parallel to axis 13, which allows it to deflect the light with a second deflection angle θ2, wherein the output deflection angle is derived from a combination of the first and second deflection angles (e.g., 2(θ1–θ2)). Oscillations at two different resonant frequencies interfere in a manner that generates a beat pattern of a beat wave, such that the trajectory of the output deflection angle follows the beat pattern of the beat wave. Therefore, the rate of change of the output deflection angle depends on the beat pattern of the beat wave.

[0035] Two MEMS mirrors 12 and 14 are arranged sequentially along the beam propagation path, such that one MEMS mirror (e.g., MEMS mirror 12) first receives the beam and deflects it according to its deflection angle θ1, and the second MEMS mirror (e.g., MEMS mirror 14) receives the beam from the first MEMS mirror and deflects it according to its deflection angle θ2, and simultaneously according to an output deflection angle modulated by the fact that the two MEMS mirrors oscillate at different resonant frequencies on parallel axes. As a result, the two MEMS mirrors 12 and 14 operate together to deflect the beam generated by the illumination unit 10 with the output deflection angle. In this way, the two MEMS mirrors 12 and 14 can guide the beam to the desired coordinates in the field of view.

[0036] exist Figure 1B In another example shown, a 1D MEMS mirror 14, implemented within a gimbal frame, is used to deflect the beam. An internal oscillating frame is configured to oscillate about an external rotating fixed frame at a first resonant frequency f1, and the MEMS mirror 14 is configured to oscillate about the internal oscillating frame at a second resonant frequency f2. In other words, the MEMS mirror 14 is configured to oscillate about its rotation axis 15 about the external rotating fixed frame according to the trajectory of the output deflection angle, the trajectory having a beat wave pattern. In other words, the oscillations of the internal oscillating frame and the MEMS mirror 14 at two different resonant frequencies interfere in a manner that generates a beat wave pattern, such that the trajectory of the output deflection angle follows the beat wave pattern. Therefore, the rate of change of the output deflection angle depends on the beat wave pattern. In this way, a single MEMS mirror can redirect the beam received from the illumination unit 10 according to the modulated angular trajectory.

[0037] Each MEMS mirror 12, 14, and 15 is a resonator (i.e., a resonant MEMS mirror) configured to oscillate "left and right" at a resonant frequency around each of its scanning axes, causing the MEMS mirror to oscillate back and forth in the scanning direction of the respective scanning axis. As will be described in further detail below, different resonant frequencies can be used for each scanning axis 13 and 15 to define the mode.

[0038] Scanning systems 100A and 100B each include an illumination unit 10 (i.e., a light emitter) comprising at least one light source (e.g., at least one laser diode or light-emitting diode) configured to transmit a light beam along a transmission path toward the MEMS mirror(s). The illumination unit 10 can emit the light beam as an FMCW beam according to a trigger signal received from the system controller 23.

[0039] Scanning systems 100A and 100B also include a system controller 23 configured to control components of the scanning system. In some applications, such as LiDAR, the system controller 23 may also be configured to receive raw data from a light sensor (not shown) and perform processing thereon (e.g., via digital signal processing) to generate object data (e.g., point cloud data). Therefore, the system controller 23 includes at least one processor and / or processor circuitry (e.g., phase detector, comparator, ADC, and digital signal processor (DSP)) for processing the data, and control circuitry, such as a microcontroller, configured to generate control signals.

[0040] System controller 23 is configured to generate a trigger signal used to trigger the beam generation of illumination unit 10. System controller 23 is also configured to set the drive frequency of the resonant structure (e.g., MEMS mirror or oscillating frame) for each of its respective scanning axes, and is capable of synchronizing the oscillations around the two scanning axes 13 and 15, for example, according to a desired frequency difference.

[0041] Both scanning systems 100A and 100B include a resonant structure for driving the system around the first scanning axis 13 (e.g., Figure 1A MEMS mirror 12 or Figure 1B The system controller 23 has a driver 25 for the internal oscillation frame and a MEMS driver 26 for driving the MEMS mirror 14 around the second scan axis 15. Each driver 25, 26 actuates and senses the rotational position of its resonant structure about its respective scan axis and provides the system controller 23 with position information of the resonant structure (e.g., rotation degree or tilt angle around the rotation axis). Based on this position information, the system controller 23 can adjust one or more system parameters.

[0042] A driving voltage (i.e., an actuation or drive signal) is applied by a driver to an actuator structure corresponding to a resonant structure on its respective scan axis to drive the resonant structure to oscillate around that scan axis. The driving voltage may be referred to as high voltage (HV). The actuator structure may include interdigital electrodes made of interdigital mirror combs and frame combs, to which the driving voltage (i.e., an actuation or drive signal) is applied by the resonant structure. The driving voltage applied to the actuator structure generates a driving force, for example, between the interdigital resonant structure combs and frame combs, which generates torque on the resonant structure about its axis of rotation. The driving voltage can be switched on or off (HV on / off), thereby generating an oscillating driving force. The oscillating driving force causes the resonant structure to oscillate back and forth between two extreme values ​​on its axis of rotation. The driving voltage can be a constant driving voltage, meaning that the driving voltage is the same voltage when actuated (i.e., switched on). However, it will be understood that the driving voltage is switched on and off to generate oscillation. Depending on the configuration, the actuation can be adjusted or modified by adjusting the drive voltage off time, the drive voltage level, or the duty cycle.

[0043] In other embodiments, an electromagnetic actuator can be used to drive the resonant structure around the corresponding scanning axis. For the electromagnetic actuator, a drive current (i.e., an actuation or drive signal) can be used to generate the oscillating drive force. Therefore, it should be understood that drive / driving voltage and drive / driving current are used interchangeably herein to indicate the actuation signal or drive signal, and both can generally be referred to as the drive force.

[0044] Therefore, the transmission technology includes at least two resonant structures used to transmit continuous light waves from one or both transmission mirrors into the field of view according to the scanning pattern. The resonant structures oscillate continuously in a resonant manner around each scanning axis, such that the continuous wave beam is projected into the field of view and moves across the field of view as the resonant structures change their transmission direction. Furthermore, additional conditions, such as the resonant frequency and frequency difference, are set by the system controller 23 to generate the desired scanning pattern as a beat pattern.

[0045] Figure 2 An illustration is provided according to one or more embodiments. Figure 1A The diagram shows a side view of the deflection system of the resonant MEMS mirror scanning system 100A. The deflection system receives an input beam A (e.g., an FMCW beam) transmitted along a first reference axis (e.g., the x-axis) and outputs an output beam D according to an output deflection angle θout = θD, the output deflection angle having an angular trajectory that follows the beat pattern of the beat wave with respect to a second reference axis parallel to the first reference axis (e.g., the x' axis). In other words, the output deflection angle θout varies (e.g., + / - 15 degrees) with respect to the second reference axis.

[0046] Angle θA is the input beam angle of the input beam A relative to the x-axis. In this case, the input beam angle is set to zero.

[0047] The deflection system includes a MEMS mirror 12 that receives the input beam and deflects it toward the MEMS mirror 14 at a first deflection angle θB. θB is the angle between the beam B after reflection by the MEMS mirror 12 and the x-axis. θB is calculated according to equations 1 and 2.

[0048] AOI1=θ1-180° Equation 1

[0049] θA=θ1+AOI1 Equation 2

[0050] AIO1 indicates the first incident angle (AOI) of the light beam incident on the MEMS mirror 12 (i.e., the angle between the input beam A and the normal vector n1).

[0051] MEMS mirror 14 is configured to receive a beam of light from MEMS mirror 12 and deflect the beam by a second deflection angle θD (i.e., output deflection angle θout).

[0052] It should be noted that the reflecting surface of MEMS mirror 12 is taken as the incident normal n1, from which the first deflection angle θB is calculated, and the reflecting surface of MEMS mirror 14 is taken as the incident normal n2, from which the second deflection angle θD is calculated. The output deflection angle θout of the beam is based on the difference between the first deflection angle and the second deflection angle (e.g., θout = 2(θ1 - θ2)). Specifically, the first mirror angle θ1, the second mirror angle θ2, and the output deflection angle θout are calculated according to Equations 3-7.

[0053] θ1=θ1′+A*sin(2π*f1*t) Equation 3

[0054] θ2=θ2′+A*sin(2π*f2*t) Equation 4

[0055] θ D =2θ2′-2θ1′+180°+2A(sin(2π*f2*t)-sin(2π*f1*t)) Equation 5

[0056] θ1′-θ2′=90° with a 0° offset, Equation 6

[0057]

[0058] Here, A denotes the maximum deflection angle magnitudes of mirror angles θ1 and θ2, where both have equal maximum deflection magnitudes. For example, the angle magnitude A could be equal to 7.5°, which would provide an angle range of + / - 30 degrees for the output deflection angle θout. Equation 7 defines the beat pattern followed by the output deflection angle θout due to the parallelism of axes 13 and 15 and the difference between f1 and f2. In other words, θout = θD and varies relative to the x′ axis according to the beat pattern.

[0059] θ1′ is the angle between the normal vector and the x-axis when MEMS mirror 12 is stationary or at zero position. Similarly, θ2′ is the angle between the normal vector n2 and the x′ axis or the x-axis, as it is the same when MEMS mirror 14 is stationary or at zero position. It is important to note that θ1′ - θ2′ = 90°, therefore 2θ2′ - 2θ1′ + 180° = 0° in Equation 5. In this case, when both mirrors are at 0° (e.g., when neither MEMS mirror 12 nor 14 is moving), the output beam θout = θD is collinear with the input beam A.

[0060] The deflection system also includes a relay optics system comprising two collimating lenses 31 and 32 arranged sequentially along the transmission path between the two MEMS mirrors 12 and 14. The relay optics system relays the beam deflected by MEMS mirror 12 to MEMS mirror 14. Specifically, lens 31, having the axis of rotation 13 of mirror 12 in its focal plane, receives the deflected beam B from MEMS mirror 12 and guides the beam as a collimated beam to lens 32. In this way, the two MEMS mirrors 12 and 14 are optically coupled to each other via the relay optics system, meaning that even if they are mechanically separated, they will receive and deflect the same beam. Lens 32, having the axis of rotation 15 of mirror 14 in its focal plane, then guides beam C to MEMS mirror 14 at an angle θC. MEMS mirror 12, the relay optics system, and MEMS mirror 14 are arranged sequentially along the beam transmission path.

[0061] θC is the angle between the beam C and the x-axis after the propagation relay optics (i.e., after lens 32). θC is calculated according to Equation 8.

[0062] θC = 360° - θB + 180° Equation 8

[0063] θD is the angle between the output beam D and the x′ axis or the x-axis. θD can be calculated using equations 9 and 10.

[0064] AOI2=θC-180°-θ2 Equation 9

[0065] θD=θ2-AOI2 Equation 10

[0066] Where AOI2 is the second incident angle of the beam C incident on the MEMS mirror 14 (i.e., the angle between the beam C and the normal vector n2).

[0067] Figure 3A The illustration shows a portion of the angular trajectory of the output deflection angle θout according to one or more embodiments. The oscillations of MEMS mirrors 12 and 14 at their respective resonant frequencies interfere with each other according to Equation 3 to generate a beat wave with a beat mode (i.e., an interference mode). The beat wave has two types of periodic oscillations: one is a slowly moving envelope oscillating at the beat frequency, and the other is a rapidly moving oscillation trajectory within the envelope (i.e., confined within the envelope).

[0068] The slow motion region is generated along the envelope and can be used for measurements requiring slow mirror motion. For example, the angular velocity, or rate of change, of the output deflection angle θout is maximum when the resonant structure crosses its zero deflection angle and minimum when the output deflection angle θout changes direction at its extreme or peak amplitude. The zero deflection angle is the angular position where the mirror naturally comes to rest without being driven. Therefore, the angular velocity slows down in the angular region near each peak of the angular trajectory of the output deflection angle θout (i.e., near each peak of the beat wave). It is in this region that slow motion measurements can be used.

[0069] like Figure 3A As shown, the output deflection angle θout of the beam oscillates according to the beat pattern of the beat wave, the extreme amplitude of which is modulated and defined by a periodic envelope. The periodic envelope is a sine wave whose frequency is called the beat frequency. The periodic envelope defines the “shape” or “profile” of the beat wave. The extreme amplitude extends to the boundary of this envelope and is therefore constrained by the sinusoidal envelope. The periodic envelope is defined by the sine term in Equation 3. Therefore, the beat frequency is defined by dividing the predetermined frequency difference (f1-f2) by 2.

[0070] Although the extreme amplitude of the output deflection angle θout is modulated by the periodic envelope over time, the oscillation frequency of the output deflection angle θout lies within the envelope defined by the cosine term in Equation 3. Therefore, the oscillation frequency of the output deflection angle θout is defined by the average of the first and second resonant frequencies (i.e., f1 + f2 divided by 2).

[0071] In summary, the output deflection angle θout shifts according to the beat pattern of the beat wave, the extreme amplitude of which is modulated and defined by a periodic envelope, wherein the periodic envelope has a beat frequency defined by a predetermined frequency difference and the beat wave has an oscillation frequency defined by the average of the first and second resonant frequencies.

[0072] Since the predetermined frequency difference between f1 and f2 defines the beat frequency, it is also responsible for defining the shape of the periodic envelope. Specifically, the beat frequency is related to the slope of the periodic envelope, including the maximum slope of the periodic envelope. System controller 23 is configured to control drivers 25 and 26 to control the predetermined frequency difference (f1-f2) such that the maximum slope of the periodic envelope is maintained below a predetermined threshold throughout the entire scan cycle, during which the beam is deflected across the full angular range of the output deflection angle. In this way, a slow motion zone is guaranteed to be generated along the envelope at each angle throughout the entire scan cycle.

[0073] As noted above, slow motion intervals appear in the region near each oscillation peak of the beat wave. This is where the output deflection angle θout slows down due to changes in direction (i.e., from left to right or from right to left). Each slow motion interval occurs only for a portion of the angular space. In other words, each slow motion interval covers a corresponding angular range depending on the beat frequency. As the output deflection angle θout approaches its extreme amplitude, it begins to slow down. At a certain deflection angle, the angular velocity of the output deflection angle θout falls below a predetermined velocity threshold that defines "slow motion," which may be the limit of some slow motion measurements. As the output deflection angle θout passes through its extreme amplitude, the slow motion interval continues, at which point the angular velocity of the output deflection angle θout begins to increase. The slow motion interval ends when the angular velocity again reaches or exceeds the predetermined velocity threshold.

[0074] exist Figure 3A In this system, the “tips” of the beat pattern are marked by slow-motion intervals that follow along the periodic envelope. Since the extreme amplitude of the output deflection angle θout is modulated by the periodic envelope, each oscillation covers a different angular range in which its slow-motion interval occurs. System controller 23 is configured to control drivers 25 and 26 to control a predetermined frequency difference such that the beat pattern of the beat wave has a slow-motion interval along the entire trajectory of the periodic envelope, where the slow-motion interval is a segment of the beat wave where the rate of change of the output deflection angle θout is less than a predefined velocity threshold.

[0075] Figure 3B The diagram illustrates only a portion of the angular trajectory of the output deflection angle θout as a possible example, where the first resonant frequency f1 is set to 2kHz, the second resonant frequency f2 is set to 1.975kHz, and the angular amplitude A is set to 7.5°.

[0076] Figure 3C The diagram shows... Figure 3BThe amplified portion 300 of the beat wave is shown. Each slow motion interval is defined by a corresponding angular range and a corresponding time range. As can be seen, the leftmost oscillation peak of the output deflection angle θout has a slow motion interval covering the angular range AR1 in the angular space. The next adjacent oscillation peak has a slow motion interval covering a different angular range AR2, which is at least adjacent to the angular range AR1. In this case, the angular range AR2 overlaps with the angular range AR1. In this way, all angular values ​​along the periodic envelope trajectory in the angular ranges AR1 and AR2 have a slow motion portion that can be measured.

[0077] Similarly, the next adjacent oscillation peak has a slow motion interval covering at least a different angular range AR3 adjacent to angular range AR2. The next adjacent oscillation peak has a slow motion interval covering at least a different angular range AR4 adjacent to angular range AR3. The next adjacent oscillation peak has a slow motion interval covering at least a different angular range AR5 adjacent to angular range AR4. The next adjacent oscillation peak has a slow motion interval covering at least a different angular range AR6 adjacent to angular range AR5. The next adjacent oscillation peak has a slow motion interval covering at least a different angular range AR7 adjacent to angular range AR6. The next adjacent oscillation peak has a slow motion interval covering at least a different angular range AR8 adjacent to angular range AR7. Finally, the next adjacent oscillation peak has a slow motion interval covering at least a different angular range AR9 adjacent to angular range AR8.

[0078] This pattern of continuous or overlapping slow motion angular ranges continues along the upper extremum of the upper (positive) portion of the periodic envelope and the lower extremum of the lower (negative) portion of the periodic envelope. As a result, all angle values ​​within the full angular range of the output deflection angle θout (e.g., all angle values ​​between + / -15 degrees) have a slow motion portion during which slow motion measurements can be performed. In other words, the periodic envelope has a maximum peak value defining the absolute maximum output deflection angle of the beam, and a minimum peak value defining the absolute minimum output deflection angle of the beam. The maximum and minimum output deflection angles define the full angular range of the output deflection angle of the beam, and the slow motion intervals overlap in angular space along the beat wave trajectory such that the slow motion intervals, as a whole, coincide with all deflection angles within the full angular range of the output deflection angle θout.

[0079] Slow motion intervals with positive angle values ​​can be referred to as the first plurality of slow motion intervals, while those with negative angle values ​​can be referred to as the second plurality of slow motion intervals. Each of the first plurality of slow motion intervals contains a different maximum value among a plurality of maximum values ​​of the beat wave, wherein adjacent slow motion intervals of the first plurality of slow motion intervals have overlapping different corresponding angle ranges, and each of the second plurality of slow motion intervals contains a different minimum value among a plurality of minimum values ​​of the beat wave, wherein adjacent slow motion intervals of the second plurality of slow motion intervals have overlapping different corresponding angle ranges.

[0080] Compared to oscillating waveforms whose extreme amplitudes are constant and therefore do not require modulation using a periodic envelope, slow motion intervals are only possible, for example, around 15 degrees and -15 degrees (i.e., close to the absolute maximum and minimum values). The vast majority of oscillating waveforms (e.g., + / -14.5 degrees) are too fast for slow motion measurements unless the oscillation of the output deflection angle is significantly slowed down by using a low resonant frequency. Even then, not all output deflection angles are likely to coincide with slow motion. However, as noted above, mirror oscillations are susceptible to vibrations, and a further consequence is low resolution.

[0081] Figure 4A The diagram illustrates only a portion of the angular trajectory of the output deflection angle θout as a possible example, where the first resonant frequency f1 is set to 2kHz, the second resonant frequency f2 is set to 1.950kHz, and the angular amplitude A is set to 7.5°.

[0082] Figure 4B The diagram shows... Figure 4A The amplified portion of the beat wave shown is 400°. Each slow motion interval is defined by a corresponding angular range AR10–AR15 and a corresponding time range. However, with Figure 3C Compared to the angular ranges AR1-AR9 shown, the angular ranges AR10-AR15 of adjacent oscillation peaks do not overlap. In this case, there are angular ranges that cannot be used for slow motion during the trajectory of the output deflection angle θout. This will result in certain angular regions in the field of view being unable to be measured for slow motion, thus causing "blind spots" or gaps in slow motion applications. Therefore, the system controller 23 is configured to control the drivers 25 and 26 to control a predetermined frequency difference such that the beat pattern of the beat wave has a slow motion interval along the entire trajectory of the periodic envelope, and additionally, that adjacent slow motion intervals along the trajectory of the periodic envelope have continuous or overlapping angular ranges, so that all angular values ​​of the full angular range of the output deflection angle θout have their corresponding slow motion intervals.

[0083] Figure 5The illustration shows a MEMS scanning device 500 according to one or more embodiments. Specifically, the MEMS scanning device 500 is a one-dimensional MEMS mirror 14 implemented in a gimbal frame, such as... Figure 1B As shown in the diagram, the gimbal frame includes an outer rotating fixed frame 51 that does not rotate or oscillate about an axis, an inner oscillating frame 52 suspended from the outer rotating fixed frame by a pair of suspension structures 53 and 54, and a resonant MEMS mirror 14 suspended from the inner oscillating frame 52 by a pair of suspension structures 55 and 56. Furthermore, the first rotation axis 13 coincides with the second rotation axis 15, and these two rotation axes can be considered as identical, common rotation axes.

[0084] The internal oscillation frame 52 is a resonant structure configured to oscillate relative to the external rotating fixed frame 51 at a first resonant frequency f1 around a first rotation axis 13. Additionally, the MEMS mirror 14 is configured to oscillate relative to the internal oscillation frame 52 at a second resonant frequency f2 around a second rotation axis 15. Furthermore, the MEMS mirror 14 is configured to oscillate relative to the external rotating fixed frame 51 around the second rotation axis 15 according to the beat frequency of the beat wave. In other words, the oscillation trajectory of the output deflection angle θout follows the beat pattern of the beat wave.

[0085] The first pair of suspension structures 53 and 54 extend along the first rotation axis 13 and mechanically couple the inner oscillating frame 52 to the outer rotating fixed frame 51. The second pair of suspension structures 55 and 56 extend along the second rotation axis 15 and mechanically couple the resonant reflector to the inner oscillating frame. The suspension structures behave similarly to torsion springs, twisting about their rotation axes as their respective resonant structures oscillate.

[0086] The entire device 500 can be made of semiconductor material into a single integrated structure. An external rotating fixed frame 51 surrounds an internal oscillating frame 52, and the internal oscillating frame 52, coupled between the external rotating fixed frame 51 and the MEMS mirror 14, surrounds the MEMS mirror 14.

[0087] As mentioned earlier, the first resonant frequency f1 and the second resonant frequency f2 are different and a predetermined frequency difference is defined. As a result, the output deflection angle of the beam oscillates according to the beat pattern of the beat wave, and the extreme amplitude of the beat wave is modulated and defined by the periodic envelope, similar to... Figures 3A-3C As shown in the diagram.

[0088] The following describes other example embodiments.

[0089] 1. A beam deflection system configured to transmit a beam with a time-varying output deflection angle, the beam deflection system comprising:

[0090] A first resonant structure configured to rotate about a first rotation axis;

[0091] A second resonant structure configured to rotate about a second rotation axis, wherein the first rotation axis is parallel to the second rotation axis; and

[0092] The driver circuit is configured to continuously drive a first resonant structure around a first rotation axis at a first resonant frequency by generating a first drive signal, and simultaneously generate a second drive signal to continuously drive a second resonant structure around a second rotation axis at a second resonant frequency, such that the first and second resonant frequencies interfere to generate a beat wave.

[0093] The output deflection angle of the beam is based on the beat mode oscillation of the beat wave, the extreme amplitude of which is modulated and defined by the periodic envelope.

[0094] The first resonant frequency and the second resonant frequency are different and a predetermined frequency difference is defined.

[0095] 2. The beam deflection system according to Embodiment 1, wherein:

[0096] The first and second resonant structures are optically coupled, and

[0097] The first resonant structure is configured to oscillate around a first rotation axis at a first resonant frequency, while the second resonant structure oscillates around a second rotation axis at a second resonant frequency, such that the output deflection angle varies with time according to the beat pattern of the beat wave.

[0098] 3. The beam deflection system according to Embodiment 2, wherein the first resonant structure and the second resonant structure are microelectromechanical systems (MEMS) mirrors.

[0099] 4. The beam deflection system according to Embodiment 1, wherein the second resonant structure is configured to deflect the beam with an output deflection angle, wherein the output deflection angle varies with time according to the beat pattern of the beat wave.

[0100] 5. The beam deflection system according to Embodiment 1, wherein:

[0101] The first and second resonant structures are mechanically coupled to each other, wherein the first rotation axis coincides with the second rotation axis, and

[0102] The first resonant structure is configured to oscillate around a first rotation axis at a first resonant frequency, while the second resonant structure oscillates around a second rotation axis at a second resonant frequency, such that the output deflection angle varies with time according to the beat pattern of the beat wave.

[0103] 6. The beam deflection system according to Embodiment 5 further includes:

[0104] Microelectromechanical systems (MEMS) devices include an external rotating fixed frame, an internal oscillating frame suspended from the external rotating fixed frame, and a second resonant structure suspended from the internal oscillating frame.

[0105] The internal oscillation frame is the first resonant structure, and

[0106] The second resonant structure is a MEMS mirror.

[0107] 7. The beam deflection system according to Embodiment 6, wherein:

[0108] An external rotating fixed frame surrounds an internal oscillating frame, and

[0109] An internal oscillating frame, coupled between an external rotating fixed frame and a second resonant structure, surrounds the second resonant structure.

[0110] 8. The beam deflection system according to Embodiment 1, wherein the periodic envelope has a beat frequency defined by a predetermined frequency difference, and the beat wave has an oscillation frequency defined by the average of a first resonant frequency and a second resonant frequency.

[0111] Although the embodiments described herein relate to MEMS devices having at least one MEMS mirror, it should be understood that other implementations may include optical devices other than MEMS mirror devices, including other non-MEMS resonant oscillation structures used to direct light according to a scanning pattern. Furthermore, while some aspects have been described in the context of the device, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or feature of a method step. Similarly, aspects described in the context of method steps also represent a description of a corresponding block or item or feature of the corresponding device. Some or all of the method steps may be performed by (or using) hardware devices, such as, for example, a microprocessor, a programmable computer, or electronic circuitry. In some embodiments, some or more method steps may be performed by such devices.

[0112] It should also be noted that the methods disclosed in the specification or claims can be implemented by a device having components for performing each of the corresponding actions of these methods. Furthermore, it should be understood that the disclosure of multiple actions or functions in the specification or claims may not be construed as being in a particular order. Therefore, the disclosure of multiple actions or functions does not limit these to a particular order unless such actions or functions are not interchangeable for technical reasons. Additionally, in some embodiments, a single action may include or may be divided into multiple sub-actions. Unless expressly excluded, such sub-actions may be included within and part of the disclosure of such a single action.

[0113] The techniques described in this disclosure can be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of the described techniques can be implemented within one or more processors, including one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable logic arrays (FPGAs), programmable logic controllers (PLCs), or any other equivalent integrated or discrete logic circuitry, and any combination of such components. The terms "processor" or "processing circuitry" can generally refer to any of the aforementioned logic circuitry, alone or in combination with other logic circuitry or any other equivalent circuitry. Control units, including hardware, can also perform one or more of the techniques of this disclosure. Control units can use electrical signals and digital algorithms to perform their receiving, analyzing, and controlling functions, and may also include correction functions. Such hardware, software, and firmware can be implemented within the same device or in separate devices to support the various techniques described in this disclosure.

[0114] One or more aspects of this disclosure can be implemented as a non-transitory computer-readable recording medium having a program embodying a method / algorithm for instructing a processor to execute a method / algorithm recorded thereon. Therefore, the non-transitory computer-readable recording medium can have electronically readable control signals stored thereon that cooperate (or are capable of cooperating with) a programmable computer system to cause the corresponding method / algorithm to be executed. The non-transitory computer-readable recording medium can be, for example, a CD-ROM, DVD, Blu-ray disc, RAM, ROM, PROM, EPROM, EEPROM, flash memory, or electronic storage device.

[0115] Although various embodiments have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made to achieve some of the advantages of the concepts disclosed herein without departing from the spirit and scope of the invention. It will be apparent to those skilled in the art that other components performing the same function can be suitably substituted. It should be understood that other embodiments can be utilized and structural or logical changes can be made without departing from the scope of the invention. It should be mentioned that features interpreted with reference to specific drawings can be combined with features in other drawings, even those not explicitly mentioned. Such modifications to the general inventive concept are intended to be covered by the appended claims and their legal equivalents.

Claims

1. A beam deflection system configured to transmit a beam with a time-varying output deflection angle, the beam deflection system comprising: The first resonant structure is configured to oscillate around a first rotation axis at a first resonant frequency. The second resonant structure is configured to oscillate around the second rotation axis at the second resonant frequency. The first axis of rotation is parallel to the second axis of rotation. The first resonant frequency and the second resonant frequency are different and a predetermined frequency difference is defined; as well as The driver circuit is configured to generate a first driving signal to drive the first resonant structure around the first rotation axis at the first resonant frequency, and simultaneously generate a second driving signal to drive the second resonant structure around the second rotation axis at the second resonant frequency, such that the output deflection angle of the beam oscillates according to the beat pattern of the beat wave, the extreme amplitude of the beat wave being modulated and defined by a periodic envelope.

2. The beam deflection system of claim 1, wherein the periodic envelope has a beat frequency defined by the predetermined frequency difference, and the beat wave has an oscillation frequency defined by the average of the first resonant frequency and the second resonant frequency.

3. The beam deflection system of claim 2, wherein the output deflection angle of the beam oscillates at the oscillation frequency of the beat wave.

4. The beam deflection system according to claim 1, wherein the beat mode is an interference mode of the first resonant frequency and the second resonant frequency.

5. The beam deflection system according to claim 1, wherein the first resonant structure and the second resonant structure are optically coupled.

6. The beam deflection system according to claim 5, wherein: The first resonant structure and the second resonant structure are arranged sequentially along the transmission path of the light beam. The first resonant structure and the second resonant structure are optically coupled such that the first resonant structure is configured to receive the light beam and deflect the light beam toward the second resonant structure at a first deflection angle, and the second resonant structure is configured to receive the light beam from the first resonant structure and deflect the light beam at a second deflection angle.

7. The beam deflection system of claim 6, wherein the output deflection angle of the beam is based on the difference between the first deflection angle and the second deflection angle.

8. The beam deflection system of claim 7, wherein the output deflection angle of the beam oscillates at the average of the first resonant frequency and the second resonant frequency.

9. The beam deflection system according to claim 6, further comprising: A relay optical system is arranged between the first resonant structure and the second resonant structure, wherein the relay optical system relays the beam deflected by the first resonant structure to the second resonant structure.

10. The beam deflection system according to claim 6, further comprising: The transmitter is configured to transmit the light beam along the transmission path so as to receive and sequentially deflect it through the first resonant structure and the second resonant structure.

11. The beam deflection system according to claim 1, wherein the first resonant structure and the second resonant structure are microelectromechanical systems (MEMS) mirrors.

12. The beam deflection system of claim 1, wherein the beam is a frequency-modulated continuous wave (FMCW).

13. The beam deflection system of claim 1, wherein the driver circuit is configured to control a predetermined frequency difference such that the beat pattern of the beat wave has a slow motion interval along a trajectory of the periodic envelope, wherein the slow motion interval is a segment of the beat wave in which the rate of change of the output deflection angle is less than a predefined threshold.

14. The beam deflection system according to claim 13, wherein: The periodic envelope has a maximum peak value and a minimum peak value, wherein the maximum peak value defines the absolute maximum output deflection angle of the beam, and the minimum peak value defines the absolute minimum output deflection angle of the beam. The maximum output deflection angle and the minimum output deflection angle define the full angular range of the output deflection angle of the beam, and On the trajectory of the beat wave, the slow motion intervals overlap in angular space such that the slow motion intervals, when considered as a whole, are consistent with all deflection angles across the full angular range of the output deflection angle.

15. The beam deflection system according to claim 13, wherein: Each slow motion interval is defined by a corresponding angular range and a corresponding time range, and The corresponding angular range of the slow motion interval is continuous or overlapping along the trajectory of the periodic envelope.

16. The beam deflection system according to claim 13, wherein: Each slow motion interval is defined by a corresponding angle range and a corresponding time range. The beat wave has multiple maximum and multiple minimum values, the amplitudes of which are defined by the periodic envelope. The slow motion interval includes a first set of slow motion intervals and a second set of slow motion intervals. Each of the first plurality of slow motion intervals contains a different maximum value among the plurality of maximum values ​​of the beat wave, wherein adjacent slow motion intervals have overlapping different corresponding angular ranges, and Each of the second plurality of slow motion intervals contains a different minimum value among the plurality of minimum values ​​of the beat wave, wherein adjacent slow motion intervals of the second plurality of slow motion intervals have overlapping different corresponding angular ranges.

17. The beam deflection system of claim 1, wherein the driver circuit is configured to control the predetermined frequency difference such that the maximum slope of the periodic envelope is maintained below a predetermined threshold throughout the entire scan period, wherein the beam is deflected over the full angular range of the output deflection angle during the entire scan period.

18. The beam deflection system according to claim 17, wherein: The driver circuit is configured to control the predetermined frequency difference such that the beat pattern of the beat wave has a slow motion interval along the trajectory of the periodic envelope, wherein the slow motion interval is a segment in which the rate of change of the output deflection angle of the beat wave is less than a predefined threshold. On the trajectory of the beat wave, the slow motion intervals overlap in angular space such that the slow motion intervals, as a whole, are consistent with all deflection angles across the full angular range of the output deflection angle.

19. The beam deflection system according to claim 1, wherein the first resonant structure and the second resonant structure are mechanically coupled.

20. The beam deflection system according to claim 19, further comprising: A microelectromechanical system (MEMS) device, the MEMS device comprising an external rotating and fixed frame, an internal oscillating frame suspended from the external rotating and fixed frame, and a second resonant structure suspended from the internal oscillating frame. The internal oscillation frame is the first resonant structure. The second resonant structure is a MEMS mirror, and The first rotation axis coincides with the second rotation axis.

21. The beam deflection system according to claim 20, wherein: The MEMS device includes a gimbal frame, which comprises an external rotating and fixing frame and an internal oscillating frame. The outer rotating fixed frame surrounds the inner oscillating frame, and The internal oscillation frame is coupled between the external rotating fixed frame and the second resonant structure, and surrounds the second resonant structure.

22. The beam deflection system of claim 20, wherein the internal oscillating frame is configured to oscillate at the first resonant frequency with respect to the external rotating fixed frame, and the second resonant structure is configured to oscillate at the second resonant frequency with respect to the internal oscillating frame.

23. The beam deflection system of claim 22, wherein the second resonant structure is configured to oscillate about the second rotation axis about the external rotating fixed frame according to the beat mode of the beat wave.

24. A beam deflection system configured to transmit a beam with a time-varying output deflection angle, the beam deflection system comprising: Microelectromechanical systems (MEMS) devices, including: External rotating fixed frame; An internal oscillating frame, suspended from the external rotating fixed frame, wherein the internal oscillating frame is a resonant structure configured to oscillate relative to the external rotating fixed frame about a first rotation axis at a first resonant frequency; and A resonant mirror, suspended from the internal oscillating frame, wherein the resonant mirror is configured to oscillate relative to the internal oscillating frame at a second resonant frequency about a second rotational axis. The first axis of rotation coincides with the second axis of rotation. Wherein the first resonant frequency is different from the second resonant frequency and a predetermined frequency difference is defined; and A driver circuit configured to generate a first drive signal to drive the internal oscillating frame around the first rotation axis at the first resonant frequency, and simultaneously generate a second drive signal to drive the resonant reflector around the second rotation axis at the second resonant frequency, such that the output deflection angle of the beam oscillates according to the beat pattern of a beat wave, the extreme amplitude of which is modulated and defined by a periodic envelope.

25. The beam deflection system of claim 24, wherein the resonant mirror is configured to deflect the beam at the output deflection angle, wherein the output deflection angle varies with time according to the beat pattern of the beat wave.

26. The beam deflection system of claim 25, wherein the periodic envelope has a beat frequency defined by the predetermined frequency difference, and the beat wave has an oscillation frequency defined by the average of the first resonant frequency and the second resonant frequency.

27. The beam deflection system of claim 24, wherein the MEMS device further comprises: A first pair of suspension structures extends along the first rotation axis, wherein the first pair of suspension structures mechanically couples the internal oscillating frame to the external rotating fixed frame. as well as A second pair of suspension structures extends along the second axis of rotation, wherein the second pair of suspension structures mechanically couples the resonant mirror to the internal oscillating frame.

28. The beam deflection system of claim 24, wherein the MEMS device includes a gimbal frame, the gimbal frame comprising the outer rotation fixing frame and the inner oscillation frame. The outer rotating fixed frame surrounds the inner oscillating frame, and The internal oscillating frame is coupled between the external rotating fixed frame and the resonant reflector, and surrounds the resonant reflector.

29. The beam deflection system of claim 24, wherein the resonant mirror is configured to oscillate about the second rotation axis about the external rotating fixed frame according to the beat pattern of the beat wave.

30. A method for deflecting a beam with a time-varying output deflection angle, the method comprising: The first oscillator structure is driven to oscillate around the first rotation axis at the first resonant frequency according to the first driving signal. When the first oscillator structure is driven at the first resonant frequency, the second oscillator structure is driven to oscillate around the second rotation axis at the second resonant frequency according to the second driving signal, wherein the first rotation axis is parallel to the second rotation axis. The first drive signal and the second drive signal are controlled such that the first resonant frequency and the second resonant frequency are different and have a predetermined frequency difference between them. The beam is transmitted to be deflected by at least the second oscillator structure such that the output deflection angle of the beam oscillates according to the beat pattern of a beat wave, the extreme amplitude of which is modulated and defined by a periodic envelope.

31. The method of claim 30, wherein the oscillation of the first oscillator structure interferes with the oscillation of the second oscillator structure to generate the beat wave that modulates the output deflection angle of the beam.

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