Method and apparatus for adjusting drive of multi-axis microscanner system and microscanner system

Abstract

A method for adjusting the drive of a multi-axis microscanner system having a first vibration axis and a second vibration axis extending non-parallel, in particular orthogonally, to the first vibration axis, comprises: generating reference information, the reference information defines simultaneous resonant reference vibrations about the first and second vibration axes, in particular each vibration axis, such that the reference information determines a corresponding reference frequency and a corresponding reference phase of the reference vibrations for the first and second vibration axes, respectively; a drive device of the microscanner system is actuated in such a way that the drive device drives a first, in particular resonant, rotational oscillation of a deflection element of the microscanner system about a first oscillation axis by means of an excitation having a first drive frequency, and driving a second, in particular resonant, rotational oscillation of the deflection element about the second oscillation axis by means of an excitation having a second drive frequency, said second rotational oscillation being carried out simultaneously with the first oscillation. The actuation of the drive device is carried out in such a way that the respective drive frequency and / or drive phase of each oscillation is varied over time by adjustment in order to counteract deviations of the respective oscillation from the reference oscillation in terms of frequency and phase for the oscillation axis corresponding to the respective oscillation.

Description

Technical Field

[0001] The present invention relates to a method and a device for regulating the drive of a multi-axis, in particular a dual-axis, microscanner system, and a microscanner system having such a device for regulating its drive. Background Art

[0002] Microscanners, also referred to in technical language as "MEMS scanners," "MEMS mirrors," or "micromirrors," or in English as "microscanners," "microscanning mirrors," or "MEMS mirrors," belong to the class of microelectromechanical systems (MEMS), or more precisely, micro-opto-electro-mechanical systems (MOEMS) of the type of micromirror actuators for the dynamic modulation of electromagnetic beams, in particular visible light. Depending on the design, the modulation movement of the individual mirrors can be performed translationally or rotationally about at least one oscillation axis. In the first case, a phase shift effect is achieved, in the second case, a deflection of the incident electromagnetic beam is achieved. Also considered are microscanners and microscanner systems based thereon, in which the modulation movement of the individual mirrors is at least also rotational. In contrast to mirror arrays, in which the incident light is modulated by the cooperation of multiple mirrors on a single MEMS component, in microscanners the modulation is usually produced by individual mirrors of the respective MEMS component (microscanner).

[0003] The microscanner can therefore be used in particular for deflecting an electromagnetic beam so as to modulate the electromagnetic beam incident thereon with respect to its deflection direction by means of a deflection element ("mirror"). This can be used in particular for realizing a Lissajous projection of the beam in an observation field or projection field based on corresponding resonant vibrations of a first vibration axis and a second vibration axis about the deflection element, wherein the second vibration axis extends non-parallel to the first vibration axis, in particular orthogonally. This makes it possible, for example, to perform imaging sensing tasks or to realize display functions. In addition, such a microscanner can also be used to irradiate materials in an advantageous manner, in particular to process them. Other possible applications include the field of illuminating (Beleuchtung) or lighting (Ausleuchtung) certain open or closed spaces or spatial areas with electromagnetic beams, for example in headlight applications.

[0004] In many cases, microscanners consist of mirror plates (deflection plates) that are laterally suspended on elastically stretchable springs. A distinction is made between single-axis mirrors, which are preferably suspended so as to rotate only about a single axis, and dual-axis and multi-axis mirrors, in which rotation, in particular rotational oscillation, can occur about a corresponding number of different axes, in particular simultaneously.

[0005] Therefore, the microscanner system for deflecting an electromagnetic beam can in particular have a multi-axis microscanner, i.e., a microscanner having at least two different, non-parallel, and in particular mutually orthogonal vibration axes, or a combination of a plurality of individual, in particular two, uniaxial microscanners, which are arranged such that an incident beam can be deflected successively by different individual microscanners of the microscanner system in order to generate a two-dimensional deflection pattern, in particular a Lissajous figure. In a microscanner system having a combination of two or three uniaxial microscanners, their non-parallel vibration axes can in particular be orthogonal to one another in pairs.

[0006] Whether in the context of an imaging sensor or a display function, a multi-axis microscanner is used to deflect an electromagnetic beam, such as a laser beam or a shaped beam from any other electromagnetic beam source, at least two-dimensionally (e.g., horizontally and vertically) to scan or illuminate an object surface within the field of view. This can be accomplished, in particular, by sweeping the scanning laser beam across a rectangular area on the projection surface within the field of view. Therefore, in these applications, microscanner systems are used that have at least a two-axis microscanner or a plurality, in particular two, of single-axis microscanners connected in series in the optical path. The wavelength range of the beam to be deflected can, in principle, be selected from the entire spectrum, from short-wave UV radiation through the VIS range, the NIR range, the IR range, the FIR range, and up to long-wave terrestrial and radar radiation.

[0007] In particular, in so-called Lissajous microscanners or Lissajous microscanner systems, two non-parallel, in particular orthogonal, vibration axes are operated simultaneously, in particular at or near the resonant frequency ω0 of the respective vibration axes (i.e., within a resonant range of a limited resonant width ω0 ± δω), so that the deflected beam generates a trajectory in the form of a Lissajous figure, depending on the respective resonant vibration of each vibration axis. This allows for large amplitudes to be achieved on both axes.

[0008] Patent document EP 2 514 211 B1 discloses a deflection device of a projection system for projecting a Lissajous figure onto an observation field, which is designed to deflect a light beam about at least a first and a second deflection axis to generate a Lissajous figure. Summary of the Invention

[0009] The object of the present invention is to improve the operation of a Lissajous microscanner in order to achieve a higher image quality, in particular a higher homogeneity, when illuminating the observation field.

[0010] The object of the present invention is achieved by the teaching of the independent claim. The dependent claims provide various embodiments and developments of the present invention.

[0011] A first aspect of the present invention relates to a method for regulating the drive of a multi-axis microscanner system having a first oscillation axis and a second oscillation axis, the second oscillation axis extending non-parallel to the first oscillation axis, in particular orthogonally. The method comprises:

[0012] (i) generating reference information defining a simultaneous, in particular resonant, reference vibration about the first and second vibration axes, wherein the reference information determines a corresponding reference frequency and a corresponding reference phase of the reference vibration for the first and second vibration axes, respectively;

[0013] (ii) controlling the driving device of the micro scanner system so that the driving device

[0014] (ii-1) driving a first, in particular resonant, rotational oscillation of a deflection element (eg a mirror) of the microscanner system about a first oscillation axis by means of an excitation having a first drive frequency, and

[0015] (ii-2) Driving a second rotational oscillation of a deflection element (eg a mirror of a microscanner system) about a second oscillation axis simultaneously with the first oscillation, in particular resonantly, by means of an excitation having a second drive frequency.

[0016] The drive is controlled in such a way that the drive frequency and / or drive phase of each oscillation is varied over time by regulation in order to compensate for deviations of the individual oscillations from a reference oscillation in terms of frequency and phase for the oscillation axis associated with the individual oscillations.

[0017] The deflection element performing the first oscillation and the deflection element performing the second oscillation may be the same (multi-axis oscillation of the deflection element) or different (eg two deflection elements each performing a uniaxial oscillation).

[0018] The drive device can, in particular, have a separate drive for each vibration axis, which can in particular each have one or more actuators, in particular piezoelectric actuators. Such actuators can, in particular, be arranged on or in the suspension of one or more deflection elements in order to excite the respective deflection element to vibrate by exerting a force on the suspension.

[0019] The first and second driving frequencies may in particular be defined as angular frequencies.

[0020] Therefore, in the method according to this first aspect, a reference trajectory is indirectly defined by defining a reference vibration, which is generated when the drive device is controlled so that the microscanner system performs the reference vibration and thereby deflects the incident electromagnetic beam into the observation field corresponding to the microscanner system through at least one of its deflection elements, wherein the deflection elements rotate and oscillate around their respective vibration axes according to the reference vibration.

[0021] This control then results in the actual oscillation being adjusted by varying the drive frequency and / or drive phase such that the actually occurring trajectory tracks the determined reference trajectory at least to a high degree of approximation (depending in particular on the quality of the control and the inertia of the microscanner system). This control can therefore also be referred to as "trajectory tracking control." If the reference trajectory is adjusted to achieve a favorable illumination of the observation field by means of a suitably defined reference oscillation, this trajectory tracking control can counteract changes in this favorable illumination, for example, due to temperature changes, changes in ambient pressure, changes in beam pressure, and / or other influences on the microscanner system that alter the natural or resonant frequency of the microscanner system and that, without this control, would result in a change in illumination, in particular a less favorable trajectory. The favorable illumination can be characterized in particular by a high degree of uniformity and / or a high line density (i.e., a high density of adjacent lines of the trajectory of the electromagnetic beam deflected into the observation field by the microscanner system).

[0022] Unlike each vibration axis or oscillation being regulated independently, in the method according to the first aspect, the regulated oscillations are dependent, which comes from the fact that, in the sense of the above-mentioned trajectory tracking regulation, the two oscillations are generally regulated according to a reference trajectory determined by both oscillations.

[0023] The method can therefore be used particularly advantageously in the field of projection displays, in which the projected image must maintain a consistently high image quality despite changes in external influencing factors on the projection.

[0024] As used herein, the term "reference information" should be understood as information that specifies a corresponding reference frequency and a corresponding reference phase of the reference vibration for the first and second vibration axes, respectively. This information can be, in particular, analog or digital and, in particular, provide a correspondingly modulated signal, in particular for each vibration axis. The reference information can, in particular, be represented by two separate signals for each vibration axis: one for the reference frequency and one for the reference phase.

[0025] The term "deflecting element" as used herein is understood to mean, in particular, an object having a sufficiently smooth reflective surface (mirror) so that electromagnetic radiation (e.g., visible light) reflected according to the law of reflection maintains its parallelism and thus produces an image. To this end, the roughness of the mirror surface must be less than approximately half the wavelength of the electromagnetic radiation. Particularly suitable are average roughness values Ra ≤ 1000 nm, preferably Ra ≤ 100 nm, and particularly preferably Ra < 5 nm. The average roughness value here denotes the average distance of a measuring point on a surface from the center line. The average roughness value thus corresponds to the arithmetic mean of the numerical deviations from the center line and is defined, in particular, in accordance with standard DIN EN ISO 4287:2010.

[0026] The deflection element can be designed in particular as a mirror plate with at least one mirror surface or comprise such a mirror plate. In particular, the mirror surface itself can consist of a different material than the rest of the deflection element, for example of metal, in particular of deposited metal.

[0027] As used herein, the term "axis of vibration" or the synonym "axis" is to be understood as meaning in particular the axis of rotation of a rotational movement (axis of rotation), which is a straight line that defines or describes a rotation or a rotation.

[0028] The term "Lissajous projection" (and its variants) used in this document should in particular be understood as scanning of an observation field by means of an electromagnetic beam, which scanning is caused by at least two mutually orthogonal resonant vibrations (oscillations) of a deflection device, in particular a single deflection element or a combination of at least two deflection elements, which deflects the beam into the observation field.

[0029] As used herein, the term "piezoelectric element" (and its variants) is understood to mean a component that exploits the (direct) piezoelectric effect to generate a voltage under the action of a mechanical force (a "piezoelectric sensor") or exploits the inverse piezoelectric effect to perform a mechanical movement by applying a voltage (a "piezoelectric actuator" or its synonym "piezoelectric actuator"). In particular, ferroelectric materials always exhibit piezoelectric properties at the same time.

[0030] As used herein, the terms "comprises," "includes," "involving," "having," "with," "having" or any other variations thereof are intended to cover a non-exclusive inclusion. Thus, for example, a method or apparatus that comprises or has a list of elements is not necessarily limited to those elements but may include other elements not expressly listed or inherent in such method or apparatus.

[0031] In addition, unless expressly specified to the contrary, "or" refers to an inclusive "or" and not a non-inclusive "or". For example, one of the situations in which condition A or B is satisfied is: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0032] The terms "a" or "an," as used herein, are defined as "one / one or more." The terms "another" and "another" and any other variations thereof should be construed to mean "at least one other."

[0033] The term "plurality" as may be used herein should be understood as "two or more."

[0034] The terms "first," "second," "third," etc., in the specification and claims are used to distinguish similar or identically named elements and are not necessarily used to describe a sequential, spatial, or temporal order. It should be understood that the terms used in this manner are interchangeable where appropriate, and that the embodiments of the technical solutions described herein may be performed in an order other than that described or illustrated herein.

[0035] The terms "configured" or "designed" to fulfill a certain function (and their corresponding variations) as used herein should be understood to mean that the relevant device or its components have been designed or configured to perform the function, or at least can be adjusted, i.e., configured, to perform the function according to the corresponding settings. Configuration can be achieved, for example, by adjusting process parameters accordingly or by using switches for activating or deactivating functions or settings. In particular, a device may have multiple predefined configurations or operating modes, and configuration can be performed by selecting one of these configurations or operating modes.

[0036] Various exemplary embodiments of the method will be described below. Unless explicitly excluded or technically infeasible, these embodiments can be arbitrarily combined with each other and with other aspects of the technical solution of the present invention.

[0037] In some embodiments, the drive device is controlled as follows: before the respective drive frequencies and / or drive phases of the respective oscillations are changed over time within the framework of regulation, the drive of the first oscillation is pre-controlled at a first drive frequency, and / or the drive of the second oscillation is pre-controlled at a second drive frequency. In this way, the first and second oscillations are initially excited according to the reference oscillation. This can, in particular, continue until the oscillations reach a settling state. In the settling state, a trajectory at least substantially corresponds to the respective reference trajectory of the reference oscillation. Over time, the regulation ensures (within the limits of regulation capabilities) that the reference trajectory is maintained, even in the event of disturbances, such as changes in the natural or resonant frequency of the oscillations (e.g., due to temperature changes).

[0038] In some embodiments, the temporal variation of the drive frequency and / or drive phase of the oscillation of at least one oscillation axis within the framework of the regulation is based on measurement information, in particular a measurement signal carrying the measurement information, which describes the measured actual phase of the oscillation about the oscillation axis. This actual phase, or a variable dependent thereon (from which the actual phase can be derived), can be measured, in particular, by one or more position sensors, in particular piezoelectric sensors, which are generally configured to detect, for each oscillation axis, the deflection of a deflection element of the microscanner system corresponding to the oscillation axis. Thus, the regulation can generally be achieved by means of a phase-locked loop (PLL).

[0039] In some embodiments, the temporal variation of the drive frequency and / or drive phase of the oscillation corresponding to the vibration axis within the framework of regulation depends in particular on the phase difference between the actual phase of the oscillation represented by the measurement information and the corresponding phase of the reference oscillation with respect to the vibration axis corresponding to the oscillation.

[0040] In some embodiments, the method further comprises: (i) monitoring, for at least one vibration axis, a phase difference between a drive phase and an actual phase of the oscillation corresponding to the vibration axis; and (ii) if a change in the phase difference is determined for the vibration axis within the framework of the monitoring, changing the drive frequency of each of the first oscillation and the second oscillation within the framework of the regulation by increasing or decreasing both oscillations by the same factor, wherein the factor is selected such that a deviation of the angular frequency of the corresponding oscillation from a defined resonant range of the angular frequencies of the oscillations (ω0±δω) with respect to the at least one vibration axis is counteracted, in particular completely prevented. The deviation δω from the resonant angular frequency ω0 can in particular be determined as δω=k·ω0, where |k|≤0.1, in particular |k|≤0.05.

[0041] The regulation of the two oscillations is thus coupled via this common factor. Consequently, in the case of resonant oscillations, this common factor determines the repetition rate of the Lissajous trajectory of the deflected beam, which is determined by the two oscillations (more precisely, their vibration parameters, amplitude, frequency, and phase). This regulation thus allows compensation for external disturbances of the oscillations (e.g., temperature rise) while maintaining the set or current Lissajous trajectory. In particular, dynamically varying the repetition rate allows the system to operate resonantly within a wide range of parameter fluctuations. This makes operation possible, for example, over a wide temperature range.

[0042] In some embodiments, the adjusting is performed by determining a common factor based on one of the following parameters:

[0043] (i) a determined phase difference between the drive phase and the actual phase of only one preselected oscillation;

[0044] (ii) an average value of the determined phase differences between the respective drive phases of the first oscillation and the respective actual phases of the second oscillation;

[0045] (iii) The determined phase difference between the drive phase and the actual phase of only one oscillation, wherein the oscillation is dynamically selected from the two oscillations during the control as the oscillation with the smaller phase difference of the phase difference last determined in the time profile.

[0046] Case (i) represents a particularly simple implementation option, in particular with the aid of a PLL, in which only one oscillation is considered for determining the factor. The phase difference of the other oscillation can then be neglected and does not even need to be determined.

[0047] Case (ii) represents a particularly balanced option, in which the phase difference of the two oscillations is equally considered and thus allows at least a good approximation to the optimal adjustment of the factors. This ensures that both oscillations achieve resonant and efficient operation on average.

[0048] Case (iii) represents an option that is particularly conducive to stabilization. It is the case that the regulation is performed on the more critical (usually smaller) of the two phase differences. This allows for a dynamic switchover of which of the two oscillations plays a decisive role in the regulation. This mode is particularly capable of providing the greatest stability if the oscillation does not have a restoring force that is linearly dependent on the offset according to Hooke's law, but if this restoring force (also) has at least one cubic term (Duffing oscillator). In such oscillators, vibration instabilities can essentially occur depending on the drive frequency and / or drive phase, so that when the drive frequency changes, undesirable jumps (Sprüngen) can occur at certain points in the amplitude / drive frequency-characteristic curve. Case (iii) counteracts the risk of such jumps by avoiding these jump points by setting the drive frequency within the framework of the regulation.

[0049] In some embodiments, particularly for the reasons also mentioned in case (iii), within the framework of regulation, at the start of the first oscillation, the first drive phase is limited to be less than 90°, particularly 85° or less, ahead of the measured actual phase of the first oscillation; and / or at the start of the second oscillation, the second drive phase is limited to be less than 90°, particularly 85° or less, ahead of the measured actual phase of the second oscillation. This is done because, according to the relevant vibration equation of a Duffing oscillator, the maximum amplitude can be achieved when the drive phase leads the actual phase by 90°, but instability occurs in the range exceeding 90°.

[0050] In some embodiments, within the framework of the regulation, for at least one oscillation, a correction for the drive phase of the oscillation, defined by at least one adjustable parameter, is incorporated into the determination of a control variable for the regulation of the oscillation. This correction can be used, in particular, to correct systematic phase measurement errors when determining the actual phase. This allows for more precise trajectory tracking regulation.

[0051] In some embodiments, within the framework of the control, for at least one oscillation, a phase shift associated with the downtime of the image processing process of an image generated by the microscanner system is incorporated into the determination of a control variable for the control of this oscillation. This allows the modulation of the electromagnetic radiation beam (e.g., a laser beam) for imaging or projection to be time-aligned with the actual oscillating movement of one or more deflection elements of the microscanner system, despite the limited downtime, so that an undistorted or undisturbed image can be projected in the observation field.

[0052] A second aspect of the present invention relates to a device, in particular an electrical (especially sub-electronic) circuit, for regulating the drive of a multi-axis microscanner system having a first oscillation axis and a second oscillation axis extending non-parallel to the first oscillation axis. The device comprises:

[0053] (i) a reference information source for generating reference information, the reference information defining a simultaneous, in particular resonant, reference vibration about the first and second vibration axes, wherein the reference information determines a corresponding reference frequency and a corresponding reference phase of the reference vibration for the first and second vibration axes, respectively;

[0054] (ii) a control device for generating a control signal to control a drive device of the micro scanner system, so that the micro scanner system is controlled by the drive device controlled by the control signal.

[0055] (ii-1) driving a first rotational oscillation of a deflection element of the microscanner system about a first vibration axis by means of an excitation having a first drive frequency (ω1), and

[0056] (ii-2) Driving the deflection element of the microscanner system to a second rotational oscillation about a second oscillation axis simultaneously with the first oscillation by means of an excitation having a second drive frequency (ω1).

[0057] The control device has a regulator and is configured to generate a control signal in such a way that, for each oscillation, its respective drive frequency and / or drive phase is varied over time by regulation so as to cancel out deviations of the respective oscillation from the reference oscillation in terms of frequency and phase for the oscillation axis corresponding to the respective oscillation.

[0058] Therefore, the device is in particular also configured to perform the method according to the first aspect. Accordingly, one or more variants explained below for the method may also apply to the device: the deflection element performing the first oscillation and the deflection element performing the second oscillation may be identical (multi-axis vibration of the deflection element) or different (for example two deflection elements with uniaxial vibrations, respectively). The drive device may in particular have a separate drive for each vibration axis, which may in particular each have one or more actuators, in particular piezoelectric actuators. Such actuators may in particular be arranged on or in the suspension of one or more deflection elements so as to excite the respective deflection element to vibrate by exerting a force on the suspension. The first and second drive frequencies may in particular also be defined as angular frequencies.

[0059] In some embodiments, the reference information source is configured to determine a reference frequency and a reference phase of the reference vibration based on at least the following input parameters:

[0060] (i) a common adjustment parameter applicable to both vibration axes for setting the repetition rate of the reference vibration;

[0061] (ii) a first control parameter corresponding to the first oscillation axis and a second individual control parameter corresponding to the second oscillation axis, wherein the form of the reference oscillation can be determined based on the two individual control parameters. This also allows the shape of the trajectory (in particular in the form of a Lissajous figure) produced by the electromagnetic beam, in particular a laser beam, deflected by the deflection element of the microscanner system during the reference oscillation to be determined.

[0062] In some embodiments, the reference information source is further configured to determine the reference frequency and reference phase of the reference oscillation based on an initial phase adjustment parameter as a further input variable, which defines the initial phase of one of the two reference phases of the reference oscillation. This allows, in particular, the shape of the trajectory to be further influenced. In the case of Lissajous figures, the rotation angle of the figure can be specifically set. This setting can be selected in particular so that only minimal degradation, or no degradation at all, occurs, i.e., multiple intersection points of the trajectory coincide. This, in turn, contributes to achieving the highest possible image quality, in particular with respect to line density and / or uniformity.

[0063] In some embodiments, the control device includes a control circuit for adjusting the drive frequency and / or drive phase of the first oscillation, and a separate control circuit for adjusting the drive frequency and / or drive phase of the second oscillation. Thus, each of the two oscillations can be optimally controlled independently of the other oscillation. However, as previously explained with respect to the embodiments of the method according to the first aspect, these independent control circuits can also be coupled such that a common factor defining the repetition rate of the reference oscillation is determined based on the actual phases of the two oscillations and used to set the two reference frequencies.

[0064] In some embodiments, the device itself also has a drive device. In this case, the device itself is already able to define and drive the first and second oscillations of the microscanner system.

[0065] In some embodiments, the device is further configured to generate a control signal, thereby enabling the drive device to be controlled according to one or more embodiments of the method according to the first aspect described herein. Therefore, the above-mentioned features and advantages related to the method also apply to the device accordingly.

[0066] A third aspect of the present invention relates to a micro scanner system for deflecting an electromagnetic beam. The system comprises:

[0067] (i) a multi-axis microscanner having two different, non-parallel, in particular mutually orthogonal vibration axes, or a combination of a plurality of individual, in particular two, single-axis microscanners arranged such that an incident beam can be deflected sequentially by different individual microscanners of the microscanner system to generate a Lissajous figure; and

[0068] (ii) The device according to the second aspect is used to adjust the driving of the micro scanner system by the driving device. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] More advantages, features and application options of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0070] Figure 1 Schematically shows an exemplary embodiment of a projection device having a microscanner system for scanning an observation field with an electromagnetic beam, in particular a laser beam, deflected by the microscanner system;

[0071] Figure 2 schematically illustrates an exemplary embodiment of a signal flow diagram of a reference information source for generating reference information that collectively define simultaneous reference vibrations about first and second vibration axes of a multi-axis microscanner system;

[0072] Figure 3 Schematically illustrates an exemplary embodiment of a signal flow diagram for trajectory tracking regulation of actuation of a multi-axis microscanner system;

[0073] Figure 4 illustratively showing, by way of comparison, the amplitude and phase changes of a resonant oscillator and a Duffing oscillator in which the restoring force is linearly related to the deflection; and

[0074] Figure 5 Another exemplary embodiment of a signal flow diagram for extended regulation, which combines trajectory tracking regulation and resonant tracking regulation, for regulating the drive of a multi-axis microscanner system is schematically illustrated. DETAILED DESCRIPTION

[0075] In the accompanying drawings, the same reference numerals are used to represent the same, similar or corresponding elements, and the elements shown in the drawings are not necessarily drawn to scale. On the contrary, the various elements shown in the drawings are presented in a manner that allows those skilled in the art to understand their functions and general purposes. Unless otherwise expressly stated, the connections and couplings between the functional units and elements shown in the drawings may also be implemented as indirect connections or couplings. Unless otherwise stated, the functional units can be implemented in particular in hardware, software, or a combination of hardware and software.

[0076] Figure 1An exemplary embodiment 100 of a microscanner system is shown, comprising a two-axis microscanner 125 for scanning an observation field 115 using a laser beam 110a deflected by the microscanner 125; and a device 135, in particular an electrical circuit, for regulating the drive of the microscanner system 100. The microscanner system has a first oscillation axis and a second oscillation axis extending non-parallel to the first oscillation axis, in particular orthogonally. The microscanner system also has a laser source 105.

[0077] Here, the microscanner system 100 is configured so that the laser beam 110a generated by the laser source 105 can be directed to the observation field indirectly through the mirror image on the deflection element (mirror) 125a that oscillates about two mutually orthogonal vibration axes at the same time as the microscanner 125. Here, the laser beam 110 scans the observation field through the oscillating deflection element (mirror) 125a, which is, for example, gimbal-mounted, thereby achieving illumination of the spatial angle. Figure 1 In the example of FIG. 1 , a two-dimensional, essentially resonant vibration of the deflection element 125 a is achieved, which creates a two-dimensional trajectory, in particular a Lissajous figure 130, as an illumination pattern. This vibration can be achieved by driving the microscanner 125 (in FIG. 1 ) by means of a device 135. Figure 1 The embodiment is realized by suitable control, in particular resonant control, of the first oscillation about the first oscillation axis and the superposition of the second oscillation about the second oscillation axis.

[0078] If there is at least one object 115 (e.g., a projection surface) in the observation field, which at least partially reflects the deflected laser beam 110a on its surface to provide a reflected beam 110b, then the trajectory of the reflection points of the laser beam 110b on the surface (or in the case of multiple objects: on multiple object surfaces) forms a linear trajectory. When the radiation direction of the laser source 105 is fixed, the course of the trajectory 130 is mainly determined by the vibration movement of the mirror 125a of the microscanner 125. Figure 1 , the laser beam 110b is exemplarily depicted as a point in time during the illumination mode.

[0079] Figure 2 The reference information sources for generating reference information, in particular reference signals, which define the microscanner system (eg, Figure 1 The reference information is for the first vibration axis (in Figure 2 The second vibration axis (indicated by the subscript "a") Figure 2The corresponding reference (angular) frequency ω of the reference vibration is set respectively. ref,a or ω ref,b And the corresponding reference phase or

[0080] The input parameters of the signal flow diagram 200 are (i) the factor LPS, which serves as a common adjustment parameter for the two oscillations and gives the repetition rate of the Lissajous figure, for example in Hz; (ii) the axis-specific individual adjustment parameter M for the first vibration axis and the axis-specific individual adjustment parameter N for the second vibration axis; and (iii) the initial phase γ of the oscillation of one of the vibration axes, here for example the first vibration axis.

[0081] To obtain the corresponding angular frequency ω of the two-dimensional reference vibration (or equivalently the first and second oscillations) ref,a or ω ref,b , respectively multiplying the respective individual adjustment parameters M or N by the value obtained by multiplying the factor LPS by 2π 205 (110, 115). ref,a or ω ref,b The time integral 220 or 225 of the reference phase of the reference vibration is obtained. or Reference Phase and and the reference frequency ω ref,a and ω ref,b is an output variable of the signal flow graph 200 and defines a reference oscillation and thereby indirectly defines the Lissajous locus 130 corresponding thereto.

[0082] Signal flow graph 200 may be implemented in device 135 , in particular by electrical, in particular electronic, circuits, or by computer according to at least one computer program executable on a processor platform, or by a combination of both.

[0083] Figure 3 The signal flow diagram schematically shows the signal flow for adjusting the multi-axis micro-scanner system (e.g. Figure 1 In order to generate reference information, in particular a reference signal, defining a two-dimensional reference vibration, the signal flow diagram 300 includes Figure 2 The signal flow graph 200 of the reference information source in is an integral part.

[0084] In addition to the reference information source, the trajectory tracking control 300 has, for each vibration axis or its respective drive, a control loop for regulating the drive phase of the associated vibration axis. Figure 3For clarity, only the control circuit for the first vibration axis "a" is shown, while the control circuit for the second vibration axis "b" (whose structure is identical to that of the first vibration axis) is largely omitted. Therefore, only the control circuit for the first vibration axis will be discussed below, but the description also applies to the control circuit for the second vibration axis.

[0085] Figure 3 One of the control variables in the control loop shown is the drive angular frequency ω for driving the first oscillation about the first oscillation axis. drv,a At the beginning of regulation, the reference angular frequency ω ref,a Directly used as the driving angular frequency ω drv,a was pre-controlled and authoritatively preliminarily determined ω drv,a Then, the control parameter ω drv,a is integrated in the driving phase accumulator 305a to obtain the driving phase The electronic driver 310 a thereby generates an electronic drive signal for driving a first oscillation (eg, one or more piezoelectric actuators), which oscillation may be specifically an oscillation about a first vibration axis of the dual-axis micro-scanner 315 .

[0086] The actual phase of the first oscillation is determined by phase detection 320a. For this purpose, the actual phase of the first oscillation can be measured by sensor technology, in particular with the aid of one or more piezoelectric sensors, and the phase difference signal can be derived therefrom. The phase difference signal represents the difference between the measured actual phase and the driving phase According to the phase difference between the driving phase And use the phase difference signal And optional about the drive phase The static correction C (used to eliminate the systematic measurement error of the actual phase) generates the image phase (For example, ). In this example, the image phase Used in accordance with Figure 1 Image projection and pixel addressing in the framework of the projection of an electromagnetic beam in the observation field in order to select the next image point to be projected into the observation field in the image to be projected. The instantaneous (mechanical) phase of the first oscillation is obtained by subtracting the downtime D that occurs during the image processing process of the image processing unit 325a from the image processing unit 325a. Therefore, the image phase Specific (mechanical) phase The downtime D is advanced so that the image value of the image point (pixel) to be displayed of the projection image can be called from the image source, such as the image data memory, in time according to the image phase, so that the image value of the image point (pixel) to be displayed of the projection image can be called in time according to the (mechanical) phase of the micro scanner system. When projecting along the projection direction corresponding to the corresponding image point, the image point to be displayed is projected exactly after the downtime D. This ensures that each image point of the image to be projected is actually projected at the position specified for it in the image projected in the observation field.

[0087] The phase The reference phase provided by the feedback loop and the reference information source The control difference e is then provided to the controller 330a, which can be a P controller. The controller 330a generates an angular frequency shift as a control variable for the control, which is added to the reference angular frequency ω. ref,a to obtain an adjusted drive phase As long as there is a regulation difference, the drive vibration can be accelerated or decelerated relative to the reference vibration by the regulation loop in order to make the two vibrations in phase. Once this regulation target is achieved, the drive angular frequency ω drv,a and the reference angular frequency ω ref,a The same thing again.

[0088] The same applies to the control loop for the second oscillation axis "b", which is Figure 3 This is only partially indicated by dashed arrows and reference numerals 310b (electronic drive) and 320b (phase detection).

[0089] Depending on the design, the deflection element of the microscanner system together with its suspension can in particular have the characteristics of a nonlinear Duffing oscillator or can be described by it in a good approximation. Figure 4 A resonant oscillator with a linear relationship between restoring force and deflection is shown as an example for comparison ( Figure 4 The solid curve in the figure) and the Duffing oscillator ( Figure 4 The dashed curve in FIG4 shows the amplitude and phase changes 400 under the forced vibration condition driven at the driving angular frequency ω.

[0090] In a resonant oscillator, a stable amplitude curve appears as a function of the drive angular frequency ω, reaching its maximum at the resonant oscillator's resonant frequency, or natural frequency, ω0, and a phase of -90° (=-π / 2). In contrast, in a Duffing oscillator, an unstable region occurs when the phase falls below -90° (=-π / 2), where the oscillation amplitude suddenly collapses. For this reason, an operating point with a phase slightly greater than -90°, such as -80°, is typically chosen. At this operating point, the amplitude is still relatively large, but remains somewhat distant from the unstable region.

[0091] Figure 5Another exemplary embodiment 500 of a signal flow diagram for an extended control loop is schematically shown, which combines trajectory tracking control and resonance tracking control for regulating the drive of a multi-axis microscanner system. The extended control loop is intended to ensure that both oscillations remain within their respective resonant angular frequency ranges, thereby enabling the maintenance of large amplitudes (under resonance conditions). Here, the resonant angular frequency range includes not only the resonant angular frequency ω0 itself, but also the frequencies around it that at least approximately resonate (see Figure 4 For example, the resonant angular frequency range (resonance range) can be defined as [0.96ω0; 1.04ω0].

[0092] The extended control loop has another feedback loop (shown as a dashed line). For this purpose, first the actual phases determined for the two oscillations by means of two phase detections 320a and 320b are used. and The lower phase value is selected as the manipulated variable ("MIN"). For a microscanner that can be described by a Duffing oscillator, according to Figure 4 , this measured value is closer to the unstable region of oscillation and can therefore be called a "critical" value. This critical value is compared with the defined target value SP to determine the regulation deviation. The PID regulator 335 then controls the repetition rate LPS of the Lissajous figure based on this regulation deviation through a multiplier, thereby controlling the two reference angular frequencies ω. ref,a or ω ref,b , and thus by the above phase adjustment (the driving phase of each oscillation and ) is achieved. This ensures resonant operation of the oscillation. Here, the spatial properties of the resulting trajectory (especially the Lissajous figure) are preserved. It only runs at a slightly changed speed.

[0093] In this way, the Lissajous figures selected in advance according to the adjustment parameters N, M, and γ can be maintained. In particular, the grid size, intersection positions and other characteristics of the Lissajous figures can be ensured. During the projection process, a flicker-free and stable image effect can therefore be produced. For 3D sensing applications (for example, in the sense of "structured light"), a scanning mode can also be selected in a targeted manner, which can be kept stable in this way. When using machine learning-based image evaluation within the framework of such 3D sensing applications, the same Lissajous figures can be reliably used in virtual projection simulations (especially during machine learning training) and in real projections, thereby simplifying the machine learning process because the training space and the image evaluation in reality can be confined to the same predetermined Lissajous figures (same adjustment parameters N, M, γ).

[0094] By selecting the actual phase and The lower value ("MIN") is used as the adjustment parameter to ensure high stability of the system.

[0095] Dynamically changing the repetition rate LPS allows the microscanner system to achieve resonant operation within a larger parameter fluctuation range, thereby enabling operation within a wider temperature range, for example.

[0096] While at least one exemplary embodiment has been described above, it should be noted that numerous variations are possible. In this regard, it should also be noted that the exemplary embodiments described are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the apparatus and methods described herein. Rather, the foregoing description will provide guidance to those skilled in the art for implementing at least one exemplary embodiment, wherein it should be understood that various changes may be made in the operation and arrangement of the elements described in the exemplary embodiments without departing from the subject matter defined in the appended claims and their legal equivalents.

[0097] Reference Signs List

[0098] 100 Micro Scanner System

[0099] 105 laser source

[0100] 110a laser beam

[0101] 110b reflected beam

[0102] 115 Observation Field Objects

[0103] 125 Micro Scanner

[0104] 125a Deflection element (mirror)

[0105] 130 Loci, especially Lissajous figures

[0106] 135 Device for regulating the drive of the micro scanner system 100

[0107] 200 Reference sources, especially their signal flow diagrams

[0108] 205 Multiplication or multiplication unit

[0109] 210 Another multiplication or multiplication unit for vibrating axis b

[0110] 215 Another multiplication or multiplication unit for vibrating shaft a

[0111] 220 Integral or integrating unit for vibrating shaft b

[0112] 225 Integral or integrating unit for vibrating shaft a

[0113] 300 Tracking Adjustment

[0114] 305a drives the phase accumulator

[0115] 310a Electronic drive for vibrating shaft a

[0116] 310b Electronic drive for vibrating shaft b

[0117] 315 Micro Scanner

[0118] 320a is used for phase detection of vibration axis a

[0119] 320b is used for phase detection of vibration axis b

[0120] 325a Image processing process or image processing unit

[0121] 330a Regulator

[0122] 335 PID Regulator

[0123] 400 Amplitude and Phase Changes

[0124] 500 Tracking Regulation with Resonant Tracker

[0125] N Individual adjustment parameters of vibration axis b

[0126] M Individual adjustment parameter of vibration axis a

[0127] γ Initial phase adjustment parameter

[0128] LPS is used to adjust the common parameters of the two oscillations (especially the factor), which determines the trajectory repetition rate

[0129] C correction amount

[0130] D. Downtime

[0131] SP target value

[0132] ω ref,a Reference (loop) frequency of vibration axis a

[0133] ω ref,b Reference (loop) frequency of vibration axis b

[0134] Reference phase of vibration axis a

[0135] Reference phase of vibration axis b

[0136] ω drv,aDriving frequency of vibration axis a

[0137] ω drv,a Drive frequency of vibration axis b

[0138] ω drv,a Drive phase of vibration axis a

[0139] Drive phase of vibration axis b

[0140] Phase difference signal of vibration axis a

[0141] Phase difference signal of vibration axis b

[0142] Mechanical phase of oscillation

[0143] Image Phase

[0144] ω driving angular frequency

[0145] ω0 resonant angular frequency

[0146] δω is the deviation from the resonant angular frequency ω0 used to determine the resonance range.

Claims

1. A method for regulating the drive of a multi-axis microscanner system (100), the multi-axis microscanner system having a first oscillation axis and a second oscillation axis extending non-parallel to the first oscillation axis, wherein: The method comprises: Generate reference information The reference information defines a simultaneous reference vibration about the first vibration axis and the second vibration axis, such that the reference information determines a corresponding reference frequency (ω) of the reference vibration for the first vibration axis and the second vibration axis, respectively. ref,a ,ω ref,b ) and the corresponding reference phase Controlling the driving device of the micro scanner system (100) so that the driving device, By means of a first driving frequency (ω drv,a ) to drive the deflection element (125a) of the micro scanner system (100) to oscillate in a first rotation around the first vibration axis; and By means of a second driving frequency (ω drv,b ) to drive the deflection element (125a) of the micro scanner system (100) to perform a second rotational oscillation around the second vibration axis simultaneously with the first oscillation; The drive device is controlled as follows: the drive frequency (ω drv,a ,ω drv,b ) and / or drive phase By means of a regulation which varies over time, the deviations of the individual oscillations from the reference oscillation in terms of frequency and phase are compensated for for the oscillation axis corresponding to the individual oscillations.

2. The method according to claim 1, wherein The drive is controlled as follows: at the respective drive frequency (ω drv,a ,ω drv,b ) and drive phase Before the respective time variation within the framework of the regulation, the first reference frequency (ω ref,a ) pre-controls the driving of the first oscillation, and / or controls the driving of the first oscillation with the second reference frequency (ω ref,b ) performs pre-control on the drive of the second oscillation.

3. A method according to any one of the preceding claims, wherein For at least one vibration axis, the driving frequency (ω) corresponding to the oscillation of the vibration axis drv,a ,ω drv,b ) and / or drive phase The temporal variation within the framework of the control is carried out as a function of measurement information which describes the actual phase of the measured oscillation about the oscillation axis.

4. The method according to claim 3, wherein: The temporal variation of the drive frequency and / or drive phase of the oscillation corresponding to the oscillation axis within the framework of the regulation depends on the actual phase of the oscillation represented by the measurement information and the corresponding phase of the reference oscillation about the oscillation axis corresponding to the oscillation Phase difference 5. The method according to claim 3 or 4, further comprising: For at least one vibration axis, the driving phase of the oscillation corresponding to the vibration axis is monitored. The phase difference from the actual phase as well as If the phase difference is specified for the vibration axis within the framework of monitoring , then the driving frequencies (ω) of the first oscillation and the second oscillation are changed by increasing or decreasing the two oscillations by the same factor (LPS) within the framework of the regulation. drv,a ,ω drv,b ), wherein the factor (LPS) is selected such that, with respect to the at least one vibration axis, the corresponding angular frequency of the oscillation is offset from a defined resonance range of angular frequencies of the oscillation.

6. The method according to claim 5, wherein: The regulation is performed as follows: the factor is determined as a function of one of the following variables: - the determined phase difference between the drive phase and the actual phase of only one preselected oscillation - the determined driving phases of the first oscillation and the second oscillation, respectively The phase difference between the actual phase The average value of - The determined driving phase in only one oscillation The phase difference from the actual phase The oscillation is dynamically selected from the two oscillations during the control so that the phase difference last determined in the time curve is The smaller phase difference oscillation.

7. A method according to any one of the preceding claims, wherein In the framework of regulation, In the first oscillation starting state, the first drive phase limited to leading the measured actual phase of said first oscillation by less than 90°, in particular 85° or less; and / or In the starting state of the second oscillation, the second drive phase The limitation is that the actual phase of the second oscillation measured is advanced by less than 90°, in particular by 85° or less.

8. A method according to any one of the preceding claims, wherein Within the framework of the regulation, for at least one oscillation, a drive phase for the oscillation defined by at least one adjustable parameter is set. The correction variable (C) is incorporated into the determination of the control variable for regulating the oscillation.

9. A method according to any one of the preceding claims, wherein Within the framework of the regulation, for at least one oscillation, a phase shift associated with a downtime (D) of an image processing process (325a) of an image formed by the microscanner system (100) is incorporated into the determination of a control variable for regulating the oscillation.

10. A device (135), in particular a circuit, for regulating the drive of a multi-axis microscanner system (100), said microscanner system having a first oscillation axis and a second oscillation axis extending non-parallel to said first oscillation axis, wherein said device (135) comprises: To generate reference information A reference information source (200) is provided, wherein the reference information defines a simultaneous reference vibration around the first vibration axis and the second vibration axis, such that the reference information The corresponding reference frequencies (ω ref,a ,ω ref,b ) and the corresponding reference phase A control device for generating a control signal to control a driving device of the micro scanner system (100), so that the micro scanner system (100) is controlled by the driving device controlled by the control signal. By means of a first driving frequency (ω drv,a ) to drive a first rotational oscillation of a deflection element (125a) of the micro scanner system (100) around the first vibration axis, and By means of a second driving frequency (ω drv,b ) to drive the deflection element (125a) of the micro scanner system (100) to perform a second rotational oscillation around the second vibration axis simultaneously with the first oscillation; The control device has a regulator and is configured to generate a control signal in the following manner: for each oscillation, its respective drive frequency (ω drv,a, ,ω drv,b ) and / or drive phase The control device is used to vary the frequency and phase of the respective oscillation over time in order to compensate for the deviation of the respective oscillation from the reference oscillation in terms of frequency and phase for the oscillation axis associated with the respective oscillation.

11. The device (135) according to claim 10, wherein The reference information source (200) is configured to determine the reference frequency (ω) of the reference vibration according to at least the following input parameters: ref,a ,ω ref,b ) and reference phase a common tuning parameter (LPS) for both vibration axes, for setting the repetition rate of the Lissajous figures corresponding to the reference vibration; a first individual adjustment parameter (M) corresponding to the first axis of vibration and a second individual adjustment parameter (N) corresponding to the second axis of vibration, wherein the form of the reference vibration can be determined from the two individual adjustment parameters (N, M).

12. The device (135) according to claim 11, wherein The reference information source (200) is further configured to determine the reference frequency (ω) of the reference vibration in addition to the initial phase adjustment parameter (γ) as another input parameter. ref,a ,ω ref,b ) and reference phase The initial phase adjustment parameters define the two reference phases of the reference vibration One of the initial phases.

13. The device (135) according to any one of claims 10 to 12, wherein The regulating device has a driving frequency (ω) for regulating the first oscillation. drv,a ) and drive phase A regulating loop, and a separate regulating loop for regulating the driving frequency (ω) of the second oscillation drv,b ) and drive phase regulation loop.

14. The device (135) according to any one of claims 10 to 13, wherein The device (135) also comprises the drive device.

15. The device (135) according to any one of claims 10 to 14, wherein The device (135) is further configured to generate the control signal, thereby enabling the drive device to be controlled according to the method of any one of claims 2 to 9.

16. A microscanner system (100) for deflecting an electromagnetic beam (110a), comprising: a multi-axis microscanner (125; 315) having two different, non-parallel vibration axes, or a combination of a plurality of individual, in particular two, single-axis microscanners, the single-axis microscanners being arranged such that an incident beam (110a) can be deflected sequentially by different individual microscanners (125; 315) of the microscanner system (100) to generate a Lissajous figure; and The device (135) according to claim 15, is used for regulating the driving of the microscanner system (100) by means of the driving device.

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