Method for generating a rectangular 2d pattern with lissajous scans

Abstract

A method of Lissajous scanning includes transmitting a plurality of light pulses at a plurality of time points based on a trigger signal; driving around a first rotation axis at a first drive frequency (f1) according to a first drive signal and around a second rotation axis at a second drive frequency (f2) according to a second drive signal; controlling the first drive signal and the second drive signal to generate a Lissajous scanning pattern according to a predefined frame rate (FR); selecting the first drive frequency and the second drive frequency such that the frame rate is their greatest common divisor and such that they satisfy the following equation: f2 - f1 = (2*N + 1)*FR; determining the plurality of time points; and generating the trigger signal based on the determined plurality of time points, wherein the plurality of time points (t i ) is determined according to the following equation: wherein:

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for generating a rectangular 2D pattern with Lissajous scanning, in particular to a Lissajous scanning system and a method of Lissajous scanning. BACKGROUND

[0002] Lissajous scanning is a type of scanning implemented in display applications, light scanning applications and light steering applications, to name a few examples. For example, Lissajous scanning can be used in displays, Light Detection and Ranging (LIDAR) and automotive headlamps, where a light beam is steered by a scanning system according to a Lissajous pattern.

[0003] Lissajous scanning is typically done by two resonant scanning axes, each of which is driven at a constant scanning frequency with a defined frequency ratio / difference between the constant scanning frequencies, which forms a specific Lissajous pattern and frame rate. However, so far, Lissajous scanning results in the generation of random irregular patterns, non-rectangular patterns and / or non-maximized pattern density. Therefore, Lissajous scanning has not been optimized for sensitive applications requiring regular, dense patterns, such as LIDAR. In safety critical applications, again such as LIDAR, this can result in lower resolution or gaps in the data.

[0004] Therefore, there can be a need for an improved system and method capable of generating dense, rectangular, repeatable patterns with Lissajous scanning. SUMMARY

[0005] One or more embodiments provide a Lissajous scanning system, comprising: a transmitter configured to transmit a plurality of light pulses at a plurality of time points based on a trigger signal, wherein each light pulse is triggered at a respective time point; a first oscillator structure configured to oscillate around a first rotation axis; a second oscillator structure configured to oscillate around a second rotation axis; a driver circuit configured to generate a first drive signal for driving the first oscillator structure around the first rotation axis at a first drive frequency (f1) and to generate a second drive signal for driving the second oscillator structure around the second rotation axis at a second drive frequency (f2); and a controller configured to control the first drive signal and the second drive signal so as to synchronize the first oscillator structure and the second oscillator structure and to generate a Lissajous scanning pattern according to a predefined frame rate (FR),

[0006] wherein the controller is configured to select the first drive frequency and the second drive frequency such that the frame rate is a greatest common divisor of the first drive frequency and the second drive frequency, and such that the first drive frequency and the second drive frequency satisfy the following equation:

[0007] f2 - f1 = (2*N+1)*FR, where N is an integer equal to or larger than zero,

[0008] wherein the controller is further configured to determine a plurality of time points, and to generate the trigger signal based on the determined plurality of time points,

[0009] wherein the controller is configured to determine the plurality of time points (ti) according to the following formula:

[0010] wherein: i = 0, 1, 2... (4F1F2-1).

[0011] One or more embodiments provide a Lissajous scanning system, the Lissajous scanning system comprising a transmitter configured to transmit a plurality of light pulses at a plurality of time points based on a trigger signal, wherein each light pulse is triggered at a respective time point; an oscillator structure configured to oscillate about a first rotation axis and to oscillate about a second rotation axis; a driver circuit configured to generate a first drive signal for driving the oscillator structure about the first rotation axis at a first drive frequency (f1) and to generate a second drive signal for driving the oscillator structure about the second rotation axis at a second drive frequency (f2); and a controller configured to control the first drive signal and the second drive signal so as to synchronize the oscillations of the oscillator structure about the first rotation axis and the second rotation axis and to generate a Lissajous scanning pattern according to a predefined frame rate (FR),

[0012] wherein the controller is configured to select the first drive frequency and the second drive frequency such that the frame rate is a greatest common divisor of the first drive frequency and the second drive frequency, and such that the first drive frequency and the second drive frequency satisfy the following formula:

[0013] f2 - f1 = (2*N+1)*FR, where N is an integer equal to or larger than zero,

[0014] wherein the controller is further configured to determine a plurality of time points, and to generate the trigger signal based on the determined plurality of time points,

[0015] wherein the controller is configured to determine the plurality of time points (ti) according to the following formula:

[0016] wherein: i = 0, 1, 2... (4F1F2-1).

[0017] One or more embodiments provide a method for Lissajous scanning, comprising: transmitting a plurality of optical pulses at a plurality of time points based on a trigger signal, wherein each optical pulse is triggered at a corresponding time point; driving a first oscillator structure about a first rotation axis at a first drive frequency (f1) according to a first drive signal; driving a second oscillator structure about a second rotation axis at a second drive frequency (f2) according to a second drive signal; controlling the first drive signal and the second drive signal to synchronize the first oscillator structure and the second oscillator structure and to generate a Lissajous scanning pattern according to a predefined frame rate (FR); selecting the first drive frequency and the second drive frequency such that the frame rate is the greatest common divisor of the first drive frequency and the second drive frequency, and such that the first drive frequency and the second drive frequency satisfy the following formula: f2 – f1 = (2*N+1)*FR, where N is an integer equal to or greater than zero; determining a plurality of time points; and generating a trigger signal based on the determined plurality of time points, wherein the plurality of time points (ti) are determined according to the following formula:

[0018] in: i = 0, 1, 2…(4F1F2-1).

[0019] One or more embodiments provide a method for Lissajous scanning, comprising: transmitting a plurality of optical pulses at a plurality of time points based on a trigger signal, wherein each optical pulse is triggered at a corresponding time point; driving an oscillator structure about a first rotation axis at a first driving frequency (f1) according to a first driving signal; driving the oscillator structure about a second rotation axis at a second driving frequency (f2) according to a second driving signal; controlling the first driving signal and the second driving signal to synchronize the oscillation of the oscillator structure about the first rotation axis and the second rotation axis, and generating a Lissajous scanning pattern according to a predefined frame rate (FR); selecting the first driving frequency and the second driving frequency such that the frame rate is the greatest common divisor of the first driving frequency and the second driving frequency, and such that the first driving frequency and the second driving frequency satisfy the following formula: f2–f1=(2*N+1)*FR, where N is an integer equal to or greater than zero; determining a plurality of time points; and generating a trigger signal based on the determined plurality of time points, wherein the plurality of time points (ti) are determined according to the following formula:

[0020] in: i = 0, 1, 2…(4F1F2-1). Attached Figure Description

[0021] An embodiment is described herein with reference to the accompanying drawings.

[0022] Figure 1A and Figure 1B This is a schematic block diagram of a Lissajous scanning system according to one or more embodiments;

[0023] Figure 2 Showing according to Figure 1A and Figure 1B An example of a Lissajous pattern resulting from setting parameters implemented in a Lissajous scanning system;

[0024] Figure 3A The illustration shows a Lissajous scanning pattern generated by driving one or two MEMS galvanometers around their respective scanning axes, according to one or more embodiments, the Lissajous scanning pattern being further overlaid with a laser emission pattern that tracks the Lissajous scanning pattern according to calculated time points;

[0025] Figure 3B The diagram shows the product generated according to one or more embodiments. Figure 3A The laser emission pattern shows a dense, rectangular, repeatable real-time light transmission pattern; and

[0026] Figure 4 A control diagram is shown, implemented by a Lissajous scanning system according to one or more embodiments, for generating a rectangular 2D light transport pattern by Lissajous scanning. Detailed Implementation

[0027] Various embodiments will now 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 required to implement the embodiment. Rather, in other embodiments, some features or elements may be omitted or replaced by alternative features or elements. Additionally, besides the features or elements explicitly shown and described, other features or elements, such as conventional components of a sensor device, may be provided.

[0028] 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 apply to other embodiments. In some cases, to avoid obscuring the embodiments, well-known structures and apparatuses are shown in block diagram form rather than in detail.

[0029] Furthermore, in the following description, equivalent or similar reference numerals are used to denote equivalent or similar elements or elements having equivalent or similar functions. 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 of elements with the same or similar reference numerals can be interchanged.

[0030] Unless otherwise indicated, the connections or couplings between the elements shown in the accompanying drawings or described herein can be based on wired 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, as long as the general purpose of the connection or coupling is substantially maintained, such as for transmitting a signal or transmitting information.

[0031] In this disclosure, expressions including "first," "second," and / or similar ordinal numbers may modify various elements. However, these elements are not limited by the foregoing expressions. For example, the foregoing expressions do not limit the order and / or importance of elements. The foregoing expressions are only used to distinguish one element from other elements. For example, a first box and a second box represent different boxes, although both boxes are boxes. As a further example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0032] The embodiments relate to optical transmitters and optical transmitter systems configured to transmit light beams or pulses according to a scanning pattern, and more specifically according to a Lissajous scanning pattern. The light beam includes visible light, infrared (IR) light, or other types of illumination signals. In some applications, the transmitted light can be backscattered towards the system by an object, wherein the backscattered light is detected by a sensor. The sensor can convert the received backscattered light into an electrical signal, such as a current signal or a voltage signal, which can be further processed by the system to generate object data and / or an image.

[0033] For example, in a LiDAR (Light Detection and Ranging) system, a light source delivers light pulses into the field of view, and the light is reflected from one or more objects via backscattering. In particular, LiDAR is a direct time-of-flight (TOF) system, where light pulses (e.g., a laser beam of infrared light) are emitted into the field of view, and an array of pixels detects and measures the reflected beams. For example, a photodetector array receives reflections from objects illuminated by the light. The difference in return time of each light pulse across multiple pixels in the pixel array can then be used to generate a digital 3D representation of the environment or to generate other sensor data.

[0034] Lissajous scanning (e.g., according to a Lissajous scanning pattern employing two scanning axes) illuminates a scene in a continuous scanning manner. By emitting consecutive light pulses 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 represents the scanning plane with a projection center.

[0035] Lissajous scanning can also be used in other applications, such as electronic displays on which images are presented and car headlights for manipulating light.

[0036] Figure 1A and Figure 1B These are schematic block diagrams of Lissajous scanning systems 100A and 110B according to one or more embodiments. Specifically, Lissajous scanning system 100A includes two one-dimensional (1D) MEMS mirrors 12x and 12y, which are used to manipulate or otherwise deflect a beam (pulse) according to a Lissajous scanning pattern. In contrast, Lissajous scanning system 100B includes a single two-dimensional (2D) MEMS mirror 12xy, which is used to manipulate or otherwise deflect a beam (pulse) according to a Lissajous scanning pattern.

[0037] MEMS mirrors 12x and 12y are mechanically movable mirrors (i.e., MEMS micromirrors) integrated on a semiconductor chip (not shown). The MEMS mirrors according to embodiments described herein are configured to oscillate via rotation about a single resonant scanning axis (i.e., a 1D MEMS mirror) or two resonant scanning axes that are generally orthogonal to each other (i.e., a 2D MEMS mirror). The oscillation of the MEMS mirrors on the scanning axes can be performed between two predetermined extreme deflection angles (e.g., + / - 15 degrees). The Lissajous scanner is configured to manipulate the beam in two dimensions (e.g., in the horizontal x-direction and the vertical y-direction).

[0038] exist Figure 1A In the example shown, two 1D MEMS mirrors 12x and 12y are used to manipulate the light beam in two dimensions. MEMS mirror 12x includes a first resonant scanning axis 13x, which enables the MEMS mirror 12x to manipulate the light in the x-direction, while MEMS mirror 12y includes a second resonant scanning axis 13y, which enables the MEMS mirror 12yx to manipulate the light in the y-direction. The two MEMS mirrors 12x and 12y are arranged sequentially along the light beam's propagation path, such that one MEMS mirror (e.g., MEMS mirror 12x) first receives the light beam and manipulates it in the first dimension, and the second MEMS mirror (e.g., MEMS mirror 12y) receives the light beam from the first MEMS mirror and manipulates it in the second dimension. As a result, the two MEMS mirrors 12x and 12y operate together to manipulate the light beam generated by the illumination unit 10 in two dimensions. In this way, two MEMS mirrors 12x and 12y can guide the beam to the desired 2D coordinates (e.g., xy coordinates) in the field of view. Multiple beams can be manipulated by the two MEMS mirrors 12x and 12y at different 2D coordinates in a Lissajous pattern.

[0039] exist Figure 1BIn another example shown, a 2D MEMS mirror 12xy is used to manipulate a light beam in two dimensions. The MEMS mirror 12xy includes a first resonant scanning axis 13x that enables the MEMS mirror 12xy to manipulate the light in the x-direction and a second resonant scanning axis 13y that enables the MEMS mirror 12xy to manipulate the light in the y-direction. Thus, a single MEMS mirror can manipulate the light beam received from the illumination unit 10 in both the x and y directions. As a result, the MEMS mirror 12xy can guide the light beam to the desired 2D coordinates (e.g., xy coordinates) in the field of view. Multiple light beams can be manipulated by the MEMS mirror 12xy at different 2D coordinates in a Lissajous pattern.

[0040] Each MEMS mirror 12x, 12y, and 12xy is a resonator (i.e., a resonant MEMS mirror) configured to oscillate "left and right" around each of its scanning axes at a resonant frequency, causing light reflected from the MEMS mirror to oscillate back and forth in the scanning direction of the corresponding scanning axis. As will be described in further detail below, different resonant frequencies can be used for each scanning axis 13x and 13y to define a Lissajous pattern.

[0041] Both Lissajous scanning systems 100A and 110B include an illumination unit 10 (i.e., a light transmitter), which includes at least one light source (e.g., at least one laser diode or light-emitting diode) configured to transmit a light beam (pulse) along a transmission path toward one or more MEMS mirrors. The illumination unit 10 can sequentially transmit multiple light pulses according to a trigger signal received from the system controller 23.

[0042] The Lissajous scanning systems 100A and 110B 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 illustrated) and perform processing (e.g., via digital signal processing) on ​​that raw data 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., comparator, TDC, ADC, and digital signal processor (DSP)) for processing the data, and control circuitry, such as a microcontroller, configured to generate control signals.

[0043] System controller 23 is configured to generate a trigger signal for triggering illumination unit 10 to generate light pulses. Therefore, system controller 23 controls the timing of light pulses emitted from illumination unit 10 via the trigger signal. System controller 23 is also configured to set the drive frequency of the MEMS mirror for each of the scanning axes of the MEMS mirror and to synchronize the oscillations around the two scanning axes 13x and 13y.

[0044] Both the Lissajous scanning systems 100A and 110B include a MEMS driver 25x for driving a MEMS mirror (i.e., MEMS mirror 12x or 12xy) around a first scanning axis 13x and a MEMS driver 25y for driving a MEMS mirror (i.e., MEMS mirror 12y or 12xy) around a second scanning axis 13y. Each MEMS driver 25x, 25y excites and senses the rotational position of the mirror about its respective scanning axis and provides the mirror's position information (e.g., tilt angle or rotation angle around the axis of rotation) to the system controller 23. Based on this position information, the laser source of the illumination unit 10 can be triggered by the system controller 23. Therefore, the higher accuracy of the MEMS mirror position sensing results in more precise and accurate control over other components of the scanning system.

[0045] A driving voltage (i.e., an actuation or drive signal) is applied by a MEMS driver to an actuator structure corresponding to the scanning axis of the MEMS mirror to drive the MEMS mirror to oscillate around that scanning axis. The driving voltage may be referred to as a high voltage (HV). The actuator structure may include interdigitated finger electrodes made of interdigitated mirror combs and frame combs, to which the driving voltage (i.e., an actuation or drive signal) is applied by the MEMS driver. The driving voltage applied to the actuator structure generates a driving force, for example, between the interdigitated mirror combs and the frame combs, which produces a torque about the axis of rotation on the mirror body. The driving voltage can be switched on or off (HV on / off), resulting in the driving force of the oscillation. The oscillating driving force causes the mirror 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 when actuated (i.e., switched on). However, it will be understood that the driving voltage is switched on and off to generate mirror oscillation. Depending on the configuration, the actuation can be adjusted or regulated by adjusting the drive voltage off-time, the drive voltage level, or the duty cycle.

[0046] In other embodiments, an electromagnetic actuator can be used to drive a MEMS galvanometer around a corresponding scanning axis. For an electromagnetic actuator, a drive current (i.e., an actuation or drive signal) can be used to generate an oscillating driving force. Therefore, it will be understood that drive / drive voltage and drive / drive current are used interchangeably herein to indicate an actuation signal or a drive signal, and both can generally be referred to as driving force.

[0047] Therefore, the transmission technique involves transmitting a light beam into the field of view from one or two transmission mirrors using two resonant scanning axes to transmit the beam according to a Lissajous scanning pattern. The transmission mirrors oscillate continuously in resonance around each scanning axis, causing the light beam to be projected into the field of view, which moves within the field of view as the transmission direction(s) changes. Furthermore, the system controller 23 sets additional conditions to generate a Lissajous scanning pattern as a dense, rectangular, repeatable pattern. The driving around the two scanning axes is synchronized using the following conditions, while also maximizing the pattern density triggered by the laser according to the Lissajous pattern.

[0048] In order for the Lissajous pattern to reproduce itself periodically at a frame rate FR frequency [Hz], there are additional conditions regarding frequencies f1 and f2 to be satisfied, where f1 is the time-domain driving frequency of the MEMS mirror (e.g., MEMS mirror 12x or 12xy) around the scan axis 13x, and f2 is the time-domain driving frequency of the MEMS mirror (e.g., MEMS mirror 12y or 12xy) around the scan axis 13y. However, the oscillations around the two scan axes may be asynchronous and must be synchronized by the system controller 23.

[0049] For example, the coordinates X and Y of the transmitted beam are parametrically defined as oscillatory behavior variables in the time domain according to the following formula:

[0050] X = sin(2π*f1*t) (1),

[0051] Y = sin(2π*f2*t) (2).

[0052] X is the x-coordinate corresponding to the rotation angle X of the MEMS galvanometer around the scanning axis 13x, and Y is the y-coordinate corresponding to the rotation angle Y of the MEMS galvanometer around the scanning axis 13y. The X and Y coordinates are sinusoidal functions dependent on the drive frequencies f1, f2, and time (t). However, before synchronization, the X and Y angles can be expressed by the following formula:

[0053] angle

[0054] Angle Y = sin(2πtf²r) (4),

[0055] Among them, random phase The random frequencies f1r and f2r indicate that the oscillations around the two scanning axes may be out of sync.

[0056] To generate repeatable patterns (frames) with a frame rate FR, system controller 23 is configured to apply synchronization and frequency tuning to MEMS drivers 25x and 25y via control signals. When the frame rate FR is predefined, system controller 23 uses the predefined frame rate FR as the greatest common divisor for selecting frequencies f1 and f2. In other words, system controller 23 selects frequencies f1 and f2 such that the frame rate FR is their greatest common divisor:

[0057] Greatest common divisor (f1, f2) = FR (predefined) (5).

[0058] Furthermore, frequencies f1 and f2 are set to satisfy the following formula:

[0059] f2–f1=(2*N+1)*FR, where N=0,1,2,3… (6).

[0060] Therefore, N is an integer equal to or greater than zero. Finally, for synchronization and tuning operations, system controller 23 synchronizes the oscillations around the two scan axes such that the phase difference between them is zero:

[0061]

[0062] Therefore, the two resonant scanning axes are driven at constant scanning frequencies f1 and f2, respectively, with a defined frequency ratio / difference between these scanning frequencies according to formulas (5), (6) and (7), which forms a repeatable Lissajous pattern (frame) with a frame rate FR. For example, with a frame rate FR of 50 Hz and N set to zero, f1 = 450 Hz and f2 = 500 Hz. Figure 2 An example of the Lissajous pattern obtained according to these setting parameters is shown. As a result of synchronization and tuning, the system controller 23 has determined frequencies f1 and f2 according to the desired frame rate FR and has eliminated any existing phase difference between the scan axes.

[0063] The next step in generating a Lissajous scan pattern as a dense, rectangular, repeatable pattern requires determining t for laser triggering. i The time point (i.e., the time step). The time point is the moment when the illumination unit 10 is triggered to emit a light pulse and also corresponds to the target X, Y coordinates of the Lissajous pattern. The system controller 23 generates a trigger signal (e.g., a pulse signal) at each defined time step. i A time-triggered light pulse is generated. The illumination unit 10 can generate a light pulse at the signal pulse of the trigger signal. The time point ti is calculated such that the X and Y coordinates of the light pulses transmitted to the field of view define a dense rectangular repeatable pattern, wherein the pattern density of the X and Y coordinates is maximized for a predefined frame rate FR.

[0064] To determine each time point ti used for laser triggering, the system controller 23 converts the drive frequencies f1 and f2 into dimensionless frequencies (i.e., into the dimensionless time domain) according to the following formula:

[0065]

[0066]

[0067] Here, F1 is the dimensionless frequency of the driving frequency f1, and F2 is the dimensionless frequency of the driving frequency f2. As can be understood, the dimensionless frequencies F1 and F2 are calculated by dividing f1 and f2 by the frame rate FR. The dimensionless frequencies F1 and F2 represent the number of oscillations experienced by the MEMS galvanometer around its respective scan axis within one frame (i.e., on a single Lissajous pattern). For example, examples using f1 = 450, f2 = 500, and FR = 50, F1 = 9, and F2 = 10.

[0068] Next, the system controller 23 uses dimensionless frequencies F1 and F2 to calculate the dimensionless time interval Δt between time points according to the following formula:

[0069]

[0070] Next, the system controller 23 uses the dimensionless time interval Δt to calculate the dimensionless time point ti for each laser trigger according to the following formula:

[0071] Where i = 0, 1, 2, 3, ... (4F1F2-1) (11).

[0072] The dimensionless time points ti can be calculated directly from formulas (8) and (9). Each time point ti represents the time at which a light pulse is triggered at illumination unit 10, and there are 4F1F2 time points that are determined and stored (i.e., the number of time points in one cycle of the Lissajous pattern). In other words, a 4F1F2 light pulse is triggered in a single Lissajous frame or cycle before the pattern repeats itself. Multiple 4F1F2 light pulses are triggered for each Lissajous frame or cycle.

[0073] The Lissajous pattern is reproduced by a set of Xi and Yi coordinates. The Lissajous pattern is rectangular and periodic in time, with a period T equal to 1 / FR. FR The coordinates of Xi and Yi are represented by the following formulas:

[0074] X i =sin(2π*t) i *F1) (12),

[0075] Y i =sin(2π*t)i *F2) (13).

[0076] Therefore, the laser pulse triggered at time point ti is transmitted into the field of view by MEMS mirrors 12x, 12y or MEMS mirror 12xy at the 2D coordinates of Xi, Yi. The Xi, Yi coordinates correspond to the angular positions around the scanning axis 13x and the scanning axis 13y. Thus, when one or more MEMS mirrors 12x, 12y, 12xy are driven around their respective scanning axes 13x and 13y according to a configured Lissajous scanning pattern, the illumination unit 10 is triggered to emit each light pulse at a precise time point ti, which corresponds to the angular positions around the scanning axis 13x and the scanning axis 13y (i.e., according to the Xi, Yi coordinates).

[0077] The Xi and Yi coordinates can also be expressed in real time and by frequency according to the following formula:

[0078]

[0079] X i =sin(2π*t) i *f1) (15),

[0080] Y i =sin(2π*t) i *f2) (16),

[0081] i=0,1,2,3,…(4F1F2-1) (17).

[0082] Figure 3A The diagram illustrates a Lissajous scanning pattern generated by driving one or two MEMS mirrors around scanning axes 13x and 13y. This Lissajous scanning pattern is further overlaid with a laser emission pattern that tracks the Lissajous scanning pattern at calculated time points ti. In other words, each point represents a light pulse emitted at time point ti corresponding to the Xi, Yi coordinates. The resolution of the laser emission pattern is defined by 2*F1 and 2*F2 or 4F1F2.

[0083] Figure 3B Show Figure 3A The laser emission pattern is shown to more clearly illustrate the dense, rectangular, repeatable real-time optical transmission pattern generated by the algorithm described above.

[0084] Figure 4The control diagram implemented by system controller 23 is shown to generate a rectangular 2D optical transport pattern using Lissajous scanning as described above. The control diagram begins by running two MEMS mirrors 12x and 12y in Lissajous scanning mode, then continues to create a repeatable Lissajous scanning pattern with a frame rate FR and zero phase difference, then continues to calculate the time points ti as expressed by formula (14), and finally continues to trigger laser pulses at each of the determined time points ti using a trigger signal, while the two MEMS mirrors 12x and 12y oscillate synchronously according to the controlled Lissajous scanning pattern.

[0085] It should also be understood that the sin function can be replaced by any periodic continuous function func(x) with the following additional characteristics:

[0086] 1) func(x+2π) = func(x) and is symmetric about π / 2 and 3π / 2, and

[0087] 2) func(k*π / 2+x)=func(k*π / 2-x), k=1,3.

[0088] func(x+2π)=func(x) is a continuous periodic function, and is also symmetric about π / 2 and 3π / 2. func(k*π / 2+x)=func(k*π / 2-x), k=1,3. x represents 2π*t*f1 or 2π*t*f2. Written in different ways, the function func(2π*t*f1+2π)=func(2π*t*f1) is a continuous periodic function, and is also symmetric about π / 2 and 3π / 2, func(k*π / 2+2π*t*f1)=func(k*π / 2-2π*t*f1), k=1 or 3, and the function func(2π*t*f2+2π)=func(2π*t*f2) is a continuous periodic function, and is also symmetric about π / 2 and 3π / 2, func(k*π / 2+2π*t*f2=func(k*π / 2-2π*t*f2), k=1 or 3.

[0089] Therefore, sine wave functions, triangular wave functions, square wave functions, etc., can be used to reproduce Lissajous scanning patterns and determine the timing points for laser triggering.

[0090] While the embodiments described herein relate to MEMS devices having at least one MEMS galvanometer, it should be understood that other implementations may include optical devices other than MEMS galvanometer devices, including other non-MEMS resonant oscillation structures for manipulating light according to a Lissajous scanning pattern. Furthermore, although 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, wherein blocks or devices correspond to method steps or features of method steps. Similarly, aspects described in the context of method steps also represent a description of corresponding blocks or items or features of the corresponding device. Some or all of the method steps in the method steps may be performed by (or using) hardware devices, such as microprocessors, programmable computers, or electronic circuit devices. In some embodiments, one or more method steps in the method steps may be performed by such a device.

[0091] It should also be noted that the methods disclosed in the specification or claims can be implemented by means of devices having means for performing each of the various actions of these methods. Furthermore, it should be understood that the disclosure of multiple actions or functions in the specification or claims should not be construed as being in a particular order. Therefore, the disclosure of multiple actions or functions will 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 decomposed into multiple sub-actions. Unless expressly excluded, these sub-actions may be included in and are part of the disclosure of this single action.

[0092] 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 these components. The terms "processor" or "processing circuitry device" can generally refer to any of the aforementioned logic circuitry devices, alone or in combination with other logic circuitry devices, or any other equivalent circuitry device. Control units, including hardware, can also perform one or more of the techniques disclosed herein. Control units can use electrical signals and digital algorithms to perform their receiving, analyzing, and controlling functions, which 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.

[0093] One or more aspects of this disclosure can be implemented as a non-transitory computer-readable recording medium having a program recorded thereon embodying instructions for a processor to execute a method / algorithm. 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 execution of the corresponding method / algorithm. 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 memory device.

[0094] 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 appropriately 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 explained with reference to specific drawings can be combined with features of other drawings, even those not explicitly mentioned. Such modifications to the general conception of the invention are intended to be covered by the appended claims and their legal equivalents.

Claims

1. A Lissajous scanning system, comprising: The transmitter is configured to transmit multiple optical pulses at multiple time points based on a trigger signal, wherein each optical pulse is triggered at a corresponding time point; The first oscillator structure is configured to oscillate about a first rotation axis; The second oscillator structure is configured to oscillate about the second rotation axis; A driver circuit is configured to generate a first drive signal to drive the first oscillator structure around the first rotation axis at a first drive frequency f1, and to generate a second drive signal to drive the second oscillator structure around the second rotation axis at a second drive frequency f2; and The controller is configured to control the first drive signal and the second drive signal to synchronize the first oscillator structure and the second oscillator structure and generate a Lissajous scan pattern according to a predefined frame rate FR. The controller is configured to select the first drive frequency and the second drive frequency such that the frame rate is the greatest common divisor of the first drive frequency and the second drive frequency, and such that the first drive frequency and the second drive frequency satisfy the following formula: f2–f1 =(2 N+1) FR, where N is an integer equal to or greater than zero. The controller is further configured to determine the plurality of time points and generate the trigger signal based on the determined plurality of time points. The controller is configured to determine the plurality of time points (t) according to the following formula. i ): ,in: , , .

2. The Lissajous scanning system of claim 1, wherein the controller is configured to control the first drive signal and the second drive signal to synchronize the first oscillator structure and the second oscillator structure such that the phase difference between the oscillation of the first oscillator structure and the oscillation of the second oscillator structure is zero.

3. The Lissajous scanning system according to claim 1, wherein: The first oscillator structure defines a first portion of the optical transmission coordinates at a first angular position around the first rotation axis, and the second oscillator structure defines a second portion of the optical transmission coordinates at a second angular position around the second rotation axis. Each of the plurality of optical pulses is transmitted at a different optical transmission coordinate.

4. The Lissajous scanning system according to claim 3, wherein the transmission pattern of the plurality of optical pulses is rectangular.

5. The Lissajous scanning system of claim 4, wherein the pattern density of the transmitted pattern is maximized for a predefined frame rate.

6. The Lissajous scanning system according to claim 3, wherein the optical transport coordinates of each of the plurality of optical pulses are defined as follows: ， ,and ， in, X i It is the first part of the light transmission coordinates, and Y i It is the second part of the light transmission coordinates.

7. The Lissajous scanning system according to claim 3, wherein the optical transport coordinates of each of the plurality of optical pulses are defined as follows: ， ,and ， in, X i It is the first part of the light transmission coordinates, and Y i It is the second part of the light transmission coordinates, and func is a continuous periodic function symmetric about π / 2 and 3π / 2.

8. The Lissajous scanning system of claim 1, wherein the Lissajous scanning pattern is reproduced on a Lissajous frame, the plurality of optical pulses are transmitted during the Lissajous frame, and the controller is configured to repeat the Lissajous scanning pattern for each of the plurality of Lissajous frames.

9. The Lissajous scanning system according to claim 8, wherein, The controller is configured to repeat the trigger signal based on a plurality of time points determined for each of the plurality of Lissajous frames.

10. The Lissajous scanning system of claim 1, wherein the Lissajous scanning pattern is defined as follows: angle ,as well as angle , in, Angle X is the rotation angle of the first oscillator structure about the first rotation axis over time (t), and angle Y is the rotation angle of the second oscillator structure about the second rotation axis over time (t).

11. The Lissajous scanning system of claim 1, wherein the Lissajous scanning pattern is defined as follows: angle ,as well as angle , in, Angle X is the rotation angle of the first oscillator structure about the first rotation axis with time (t), and angle Y is the rotation angle of the second oscillator structure about the second rotation axis with time (t). Wherein, the function = func( ) is a continuous periodic function symmetric about π / 2 and 3π / 2, func(k π / 2 + = func(k) π / 2 - ), k = 1 or 3, and Wherein, the function = func( ) is a continuous periodic function symmetric about π / 2 and 3π / 2, func(k π / 2 + = func(k) π / 2 - ), k = 1 or 3.

12. A Lissajous scanning system, comprising: The transmitter is configured to transmit multiple optical pulses at multiple time points based on a trigger signal, wherein each optical pulse is triggered at a corresponding time point; An oscillator structure is configured to oscillate about a first rotation axis and about a second rotation axis; The driver circuit is configured to generate a first drive signal for driving the oscillator structure around the first rotation axis at a first drive frequency f1, and to generate a second drive signal for driving the oscillator structure around the second rotation axis at a second drive frequency f2. as well as The controller is configured to control the first drive signal and the second drive signal to synchronize the oscillations of the oscillator structure about the first rotation axis and the second rotation axis, and to generate a Lissajous scan pattern according to a predefined frame rate FR. The controller is configured to select the first drive frequency and the second drive frequency such that the frame rate is the greatest common divisor of the first drive frequency and the second drive frequency, and such that the first drive frequency and the second drive frequency satisfy the following formula: f2–f1 =(2 N+1) FR, where N is an integer equal to or greater than zero. The controller is further configured to determine the plurality of time points and generate the trigger signal based on the determined plurality of time points. The controller is configured to determine the plurality of time points (t) according to the following formula. i ): ,in: , , .

13. The Lissajous scanning system of claim 12, wherein the controller is configured to control the first drive signal and the second drive signal to synchronize the oscillations of the oscillator structure about the first rotation axis and the second rotation axis such that the phase difference between the oscillations is zero.

14. The Lissajous scanning system according to claim 12, wherein: The oscillator structure defines a first portion of the optical transmission coordinates around a first angular position on the first rotation axis, and the oscillator structure defines a second portion of the optical transmission coordinates around a second angular position on the second rotation axis. Each of the plurality of optical pulses is transmitted at a different optical transmission coordinate.

15. The Lissajous scanning system according to claim 14, wherein the transmission pattern of the plurality of optical pulses is rectangular.

16. The Lissajous scanning system of claim 15, wherein the pattern density of the transmitted pattern is maximized for a predefined frame rate.

17. The Lissajous scanning system of claim 14, wherein the optical transport coordinates of each of the plurality of optical pulses are defined as follows: ， ,and ， in, X i It is the first part of the light transmission coordinates, and Y i It is the second part of the light transmission coordinates.

18. The Lissajous scanning system of claim 14, wherein the optical transport coordinates of each of the plurality of optical pulses are defined as follows: ， ,and ， in, X i It is the first part of the light transmission coordinates, and Y i It is the second part of the light transmission coordinates, and func is a continuous periodic function symmetric about π / 2 and 3π / 2.

19. The Lissajous scanning system of claim 12, wherein the Lissajous scanning pattern is reproduced on a Lissajous frame, the plurality of optical pulses are transmitted during the Lissajous frame, and the controller is configured to repeat the Lissajous scanning pattern for each of the plurality of Lissajous frames.

20. The Lissajous scanning system of claim 19, wherein the controller is configured to repeat the trigger signal according to the plurality of time points determined for each of the plurality of Lissajous frames.

21. The Lissajous scanning system of claim 12, wherein the Lissajous scanning pattern is defined as follows: angle ,as well as angle , in, Angle X is the rotation angle of the oscillator structure about the first rotation axis over time (t), and angle Y is the rotation angle of the oscillator structure about the second rotation axis over time (t).

22. The Lissajous scanning system according to claim 12, wherein, The Lissajous scan pattern is defined as follows: angle ,and angle , Wherein, angle X is the rotation angle of the oscillator structure about the first rotation axis with time (t), and angle Y is the rotation angle of the oscillator structure about the second rotation axis with time (t). Wherein, the function = func( ) is a continuous periodic function symmetric about π / 2 and 3π / 2, func(k π / 2 + = func(k) π / 2- ), k = 1 or 3, and Wherein, the function = func( ) is a continuous periodic function symmetric about π / 2 and 3π / 2, func(k π / 2 + = func(k) π / 2- ), k = 1 or 3.

23. A method for Lissajous scanning, comprising: Multiple optical pulses are transmitted at multiple time points based on a trigger signal, wherein each optical pulse is triggered at a corresponding time point; The first oscillator structure is driven around the first rotation axis at a first driving frequency f1 according to the first driving signal; The second oscillator structure is driven around the second rotation axis at a second driving frequency f2 according to the second driving signal; The first drive signal and the second drive signal are controlled to synchronize the first oscillator structure and the second oscillator structure, and to generate a Lissajous scan pattern according to a predefined frame rate FR. The first driving frequency and the second driving frequency are selected such that the frame rate is the greatest common divisor of the first driving frequency and the second driving frequency, and the first driving frequency and the second driving frequency satisfy the following formula: f2–f1 =(2 N+1) FR, where N is an integer equal to or greater than zero; Determine the plurality of time points; and The trigger signal is generated based on the determined multiple time points. Among them, multiple time points (t) are determined according to the following formula. i ): ,in: , , .

24. A method for Lissajous scanning, comprising: Multiple optical pulses are transmitted at multiple time points based on a trigger signal, wherein each optical pulse is triggered at a corresponding time point; The oscillator structure is driven around the first rotation axis at a first driving frequency f1 according to the first driving signal; The oscillator structure is driven around the second rotation axis at a second driving frequency f2 according to the second driving signal; The first drive signal and the second drive signal are controlled so that the oscillation of the oscillation structure around the first rotation axis and the second rotation axis are synchronized, and a Lissajous scan pattern is generated according to a predefined frame rate FR; The first driving frequency and the second driving frequency are selected such that the frame rate is the greatest common divisor of the first driving frequency and the second driving frequency, and the first driving frequency and the second driving frequency satisfy the following formula: f2–f1 =(2 N+1) FR, where N is an integer equal to or greater than zero; Determine the plurality of time points; and The trigger signal is generated based on the determined multiple time points. Among them, multiple time points (t) are determined according to the following formula. i ): ,in: , , .

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