Method and apparatus for controlling a drive of a multi-axis microscanner system, and microscanner system

Abstract

The invention relates to a method for controlling a drive of a multi-axis microscanner system having a first vibration axis and a second vibration axis which runs in particular orthogonally, not in parallel, with respect thereto, the method comprising: generating reference information which defines a simultaneous reference vibration, which is in particular harmonic for each vibration axis, about the first and the second vibration axis so that the reference information establishes, for each of the first and the second vibration axes, an associated reference frequency and an associated reference phase of the reference vibration; activating a drive device for the microscanner system such that the drive device is prompted to drive a first, in particular harmonic, rotational oscillation of a deflection element of the microscanner system about the first vibration axes by means of excitation at a first drive frequency and to drive a second, in particular harmonic, rotational oscillation of a deflection element, carried out simultaneously with the first oscillation, about the second vibration axis by means of excitation at a second drive frequency. The drive device is activated such that, with regard to each of the oscillations, the particular drive frequency and / or drive phase thereof is or are varied over time by means of a controller such that, with respect to the vibration axis associated with the particular oscillation, deviation of the particular oscillation from the reference vibration in respect of frequency and phase is counteracted.

Description

[0001] 119077P1280PC METHOD AND DEVICE FOR CONTROLLING A DRIVE OF A MULTI-AXIS MICROSCANNER SYSTEM AND MICROSCANNER SYSTEM The present invention relates to a method and a device for controlling a drive of a multi-axis, in particular two-axis, microscanner system and to a microscanner system with such a device for controlling its drive. Microscanners, which in technical terminology are also referred to as "MEMS scanners", "MEMS mirrors" or "micromirrors" or in English in particular as "micro-scanners" or "micro-scanning mirrors" or "MEMS mirrors", are micro-electro-mechanical systems (MEMS) or more precisely micro-opto-electro-mechanical systems (MOEMS) from the class of micromirror actuators for the dynamic modulation of electromagnetic radiation, in particular visible light.Depending on the design, the modulating movement of an individual mirror can be translational or rotational around at least one oscillation axis. In the first case, a phase-shifting effect is achieved, while in the second case, the deflection of the incoming electromagnetic radiation is achieved. In the following, microscanners and microscanner systems based on them are considered, in which the modulating movement of an individual mirror is, at least partly, rotational. In contrast to mirror arrays, in which the modulation of incoming light occurs via the interaction of several mirrors on a single MEMS component, the modulation in microscanners is typically generated via a single mirror per MEMS component (microscanner).Microscanners can thus be used, in particular, to deflect electromagnetic radiation by modulating the deflection direction of an incident electromagnetic beam using a deflection element ("mirror"). This can be used, in particular, to effect a Lissajous projection of the beam into an observation field or projection field based on a respective harmonic oscillation about a first oscillation axis and a second oscillation axis of the deflection element that runs non-parallel, in particular orthogonal, to this axis. This allows, for example, imaging sensory tasks to be solved or display functionalities to be implemented. Furthermore, such microscanners can also be used to advantageously irradiate materials, in particular for their processing.Other possible applications include the illumination of specific open or closed spaces or spatial areas with electromagnetic radiation, for example, in the context of spotlight applications. 119077P1280PC Microscanners often consist of a mirror plate (deflection plate) suspended laterally on elastically stretchable springs. A distinction is made between single-axis mirrors, which are preferably mounted so they can rotate around a single axis, and dual-axis and multi-axis mirrors, in which rotations, especially rotary oscillations, around a corresponding number of different axes are possible, especially simultaneously.A microscanner system for deflecting an electromagnetic beam can thus in particular comprise a multi-axis microscanner, i.e. a microscanner with at least two different non-parallel, in particular mutually orthogonal, oscillation axes or a combination of several individual, in particular two, single-axis microscanners, which are arranged such that the incident beam can be deflected one after the other by the various individual microscanners of the microscanner system in order to generate a two-dimensional deflection pattern, in particular a Lissajous figure. In a microscanner system with a combination of two or three single-axis microscanners, their non-parallel oscillation axes can in particular be orthogonal to one another in pairs. Both in the case of imaging sensors and in the case of a display function, a multi-axis microscanner system serves to detect electromagnetic radiation such as, for example,to deflect a laser beam or a shaped beam from any other source of electromagnetic radiation at least two-dimensionally, e.g. horizontally and vertically, in order to scan or illuminate an object surface within an observation field. In particular, this can be done in such a way that the scanned laser beam sweeps over a rectangular area on a projection surface in the projection field. Thus, in these applications, microscanner systems with at least one two-axis microscanner or with several, in particular two, single-axis microscanners connected in series in the optical path are used. The wavelength range of the radiation to be deflected can in principle be selected from the entire spectrum from short-wave UV radiation, through the VIS range, NIR range, IR range, FIR range, to long-wave terahertz and radar radiation. Especially with so-called Lissajous microscanners orIn Lissajous microscanner systems, two non-parallel, in particular mutually orthogonal, oscillation axes are operated simultaneously, in particular in resonance or close to the resonant angular frequency ^0 to the respective oscillation axis (i.e. in a 119077P1280PC resonance range of finite resonance width ^0± ^^) for each oscillation axis, in order to generate a trajectory of the deflected radiation in the form of a Lissajous figure based on a respective harmonic oscillation for each oscillation axis. In this way, large amplitudes can be achieved in both axes. EP 2514211 B1 discloses a deflection device for a projection system for projecting Lissajous figures onto an observation field, which is designed to deflect a light beam about at least a first and a second deflection axis to generate Lissajous figures.It is an object of the invention to improve the operation of Lissajous microscanners with regard to a high achievable image quality, in particular with regard to a high degree of homogeneity in the illumination of the observation field. This object is achieved according to the teaching of the independent claims. Various embodiments and developments of the invention are the subject of the subclaims. A first aspect of the solution presented herein relates to a method for controlling a drive of a multi-axis microscanner system having a first oscillation axis and a second oscillation axis extending non-parallel, in particular orthogonally, thereto.The method comprises: (i) generating reference information which defines a simultaneous, in particular harmonic, reference oscillation around the first and the second oscillation axes, such that the reference information defines an associated reference frequency and an associated reference phase of the reference oscillation for the first and the second oscillation axes; (ii) controlling a drive device for the microscanner system such that the drive device is thereby caused to (ii-1) perform a first, in particular harmonic, rotary oscillation of a deflection element (e.g. mirror) of the microscanner system in order to drive the first oscillation axes by means of an excitation with a first drive frequency, and (ii-2) perform a second, in particular harmonic, rotary oscillation of a deflection element (e.g.Mirror of the microscanner system) to drive the second oscillation axis by means of excitation with a second drive frequency. The drive device is controlled in such a way that, with respect to each of the oscillations, its respective drive frequency and / or drive phase is / are varied over time by means of a control system in such a way that, with respect to the oscillation axis assigned to the respective oscillation, a deviation of the respective oscillation in terms of frequency and phase from the reference oscillation is counteracted. The deflection element performing the first oscillation and the deflection element performing the second oscillation can either be identical (multi-axis oscillation of one deflection element) or different (e.g. two deflection elements each oscillating on a single axis).The drive device can, in particular, have a separate drive for each oscillation axis, each of which can, in particular, have one or more actuators, in particular piezo actuators. Such actuators can, in particular, be arranged on or in a suspension of the deflection element(s) in order to excite the respective deflection element to oscillate by exerting force on the suspension. The first and second drive frequencies can, in particular, also be defined as angular frequencies.In the method according to the first aspect, a reference trajectory is thus indirectly defined based on the definition of the reference oscillation. This reference trajectory results when the drive device is controlled in such a way that it causes the microscanner system to execute the reference oscillation and, in doing so, to deflect an incident electromagnetic beam into an observation field assigned to the microscanner system by means of its at least one deflection element that oscillates rotationally about its respective oscillation axis(es) in accordance with the reference oscillation. The control then causes the actual oscillations to follow the actually occurring trajectory at least to a good approximation (depending in particular on the quality of the control and the inertia of the microscanner system) of the specified reference trajectory by varying the drive frequencies and / or drive phases. 119077P1280PC The control can therefore also be referred to as "trajectory following control."If the reference trajectory is adjusted using a suitable definition of the reference oscillation to result in advantageous illumination of the observation field, the trajectory tracking control can counteract a change in this advantageous illumination even if, without such control, a change in the illumination, in particular towards less advantageous trajectories, would result due to changes in temperature, ambient pressure, radiation pressure, and / or other influences on the microscanner system that alter its natural or resonant frequencies. Advantageous illumination can be characterized in particular by a high degree of homogeneity and / or a high line density (i.e., with a high density of adjacent lines of the trajectory of the electromagnetic beam deflected by the microscanner system into the observation field).In contrast to independent control of each oscillation axis or oscillation, the method according to the first aspect provides for a dependency of the controlled oscillations, which results from the fact that both oscillations as a whole are controlled in the sense of the above-mentioned trajectory tracking control on the reference trajectory determined simultaneously by both oscillations. The method can thus be used particularly advantageously in the context of applications in the field of projection displays, where a consistently high image quality of the projected image is required even when external factors influencing the projection change. The term "reference information", as used herein, is understood to mean information that defines an assigned reference frequency and an assigned reference phase of the reference oscillation for each of the first and second oscillation axes.This information can in particular be analogue or digital and can be made available in particular via an appropriately modulated signal, in particular for each oscillation axis. The reference information can in particular be represented by two separate signals for each oscillation axis, one for the reference frequency and one for the reference phase. The term “deflection element”, as used here, is understood to mean in particular a body which has a reflective surface (mirror surface) which is smooth enough that reflected electromagnetic radiation, e.g. visible light, retains its parallelism according to the law of reflection and thus an image can be created. The 119077P1280PC roughness of the mirror surface must therefore be less than approximately half the wavelength of the electromagnetic radiation. In particular, roughnesses with a mean roughness value R. a ≤ 1000 nm, preferably R a ≤ 100 nm, particularly preferably R a< 5 nm. The mean roughness indicates the average distance of a measuring point on the surface from the center line. The mean roughness thus corresponds to the arithmetic mean of the absolute deviation from the center line and is defined in particular in the standard DIN EN ISO 4287:2010. The deflection element can in particular be designed as a mirror plate with at least one mirror surface or have such a surface. In particular, the mirror surface itself can consist of a different material, e.g., a metal, in particular a deposited metal, than the rest of the body of the deflection element. The term "axis of oscillation" or, synonymously, "axis," as used herein, is to be understood in particular as an axis of rotation (rotation axis) of a rotary movement. It is a straight line that defines or describes a rotation or twist. The term "Lissajous projection" (and variations thereof), as used herein,In particular, scanning of an observation field using electromagnetic radiation is to be understood, which is effected by at least two mutually orthogonal harmonic oscillations of a deflection device deflecting the radiation into the observation field, in particular a single deflection element or a combination of at least two deflection elements. The term "piezoelectric element" (and modifications thereof), as used herein, is to be understood as a component that utilizes the (direct) piezoelectric effect to produce an electrical voltage upon application of a mechanical force ("piezoelectric sensor"), or utilizes the inverse piezoelectric effect to execute a mechanical movement by applying an electrical voltage ("piezoelectric actuator" or, synonymously, "piezoelectric actuator"). In particular, ferroelectric materials are always simultaneously piezoelectric. The terms "comprises," "includes," "includes,""Includes," "comprises," "has," "having," or any other variation thereof is intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or that are inherent in such method or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, a condition A or B is satisfied by one of the following: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present). The terms "a" or "an" as used hereinare defined as "one or more." The terms "another" and "another," and any other variations thereof, are to be understood as "at least one further." The term "plural," as used herein, is to be understood as "two or more." The terms "first," "second," "third," and similar terms in the description and claims are used to distinguish between similar or otherwise identically named elements and not necessarily to describe a sequential, spatial, or chronological order. It is understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the solution described herein may also function in orders other than those described or illustrated herein. The term "configured" or "arranged" to perform a particular function,(and respective modifications thereof), as may be used here, is to be understood that a relevant device or component thereof is already present in a configuration or setting in which it can perform the function or is at least adjustable - i.e. configurable - so that it can perform the function after appropriate setting. The configuration can be carried out, for example, via a corresponding setting of parameters of a process sequence or of switches or the like for activating or deactivating functionalities or settings. In particular, the device can have several predetermined configurations or operating modes, so that the configuration can be carried out by selecting one of these configurations or operating modes. 119077P1280PC Various exemplary embodiments of the method are now described below, each of which,Unless expressly excluded or technically impossible, they can be combined with each other as desired, as well as with the other aspects of the present solution described below. In some embodiments, the drive device is controlled in such a way that the driving of the first oscillation is pre-controlled with the first drive frequency and / or the driving of the second oscillation is pre-controlled with the second drive frequency, before the respective drive frequency and / or drive phase of the respective oscillation is varied over time within the scope of the control. In this way, the first and second oscillations are initially excited according to the reference oscillation. This can take place, in particular, until a steady state of the oscillations is reached. In the steady state, this results, at least essentially, in a trajectory,which corresponds to the reference trajectory corresponding to the reference oscillation. Over the further course of time, the control then acts to maintain the reference trajectory (within the scope of the control's capabilities) even when disturbances occur, such as changes in the natural or resonant frequencies of the oscillations (e.g., due to temperature changes). In some embodiments, the temporal variation of the drive frequency and / or the drive phase of the oscillation associated with this oscillation axis for at least one oscillation axis takes place within the scope of the control as a function of measurement information, in particular a measurement signal carrying the measurement information, which represents a measured actual phase of the oscillation about this oscillation axis. The actual phase or a variable dependent thereon, from which the actual phase can be inferred, can be measured in particular by means of one or more position sensors, in particular piezo sensors.which are configured to detect a deflection of the deflection element of the microscanner system associated with the oscillation axis for each oscillation axis. Overall, the control can thus be implemented using a phase-locked loop (PLL).PLL). In some embodiments, the temporal variation of the drive frequency and / or drive phase of the oscillation associated with this oscillation axis takes place within the scope of the control specifically as a function of a phase difference between the actual phase of the oscillation represented by the 119077P1280PC measurement information and the corresponding phase of the reference oscillation with respect to the oscillation axis associated with the oscillation. In some embodiments, the method further comprises: (i) for the at least one oscillation axis: monitoring the phase difference between the drive phase and the actual phase of the oscillation associated with this oscillation axis; and (ii) if a change in the phase difference is detected for this oscillation axis during the monitoring,Varying the respective drive frequencies for the first oscillation and the second oscillation within the framework of the control by raising or lowering them by a factor that is the same for both oscillations, wherein the factor is selected such that, with respect to at least one oscillation axis, a drift of the angular frequency of the associated oscillation out of a defined resonance range (^0± ^^) of the angular frequency of the oscillation is counteracted, in particular such a drift is completely prevented. The deviation ^^ from the resonant angular frequency ^0 can in particular be defined as ^^ = k∙^0 with |k| ≤ 0.1 , in particular with |k| ≤ 0.05. Here, the two oscillations are thus coupled with regard to their control via the common factor. As a result, this common factor determines, in the case of harmonic oscillations, a repetition rate of a frequency generated by the two oscillations (more precisely, their oscillation parameters amplitude,Frequency and phase) determined Lissajous figure-shaped trajectory of the deflected beam. The control thus allows compensation for external disturbances to the oscillations (e.g., due to temperature increases) while maintaining the set or previous Lissajous figure-shaped trajectory. Dynamically changing the repetition rate enables, in particular, resonant operation over a large range of parameter fluctuations in the system. This allows, for example, operation in a wide temperature range. In some of these embodiments, the control is carried out in such a way thatthat the common factor is determined as a function of one of the following variables: (i) the detected phase difference between the drive phase and the actual phase of only one preselected oscillation; 119077P1280PC (ii) the mean value of the detected respective phase differences between the respective drive phase and the respective actual phase of the first oscillation on the one hand and the second oscillation on the other hand; (iii) the detected phase difference between the drive phase and the actual phase of only one of the oscillations, whereby this oscillation is dynamically selected from the two oscillations during control as the one which is the smaller of the phase differences last detected over time. Case (i) represents a particularly simple implementation option, in particular using a PLL, in which only one oscillation is considered.to determine the factor. The phase difference of the other oscillation, however, can be ignored, so it does not even need to be determined. Case (ii) represents a particularly balanced option, in which the phase differences of both oscillations are considered equally, thus enabling at least a good approximation to an optimal adjustment of the factor. This ensures an averagely resonant and efficient operation of both oscillations. Case (iii) represents a particularly stability-promoting option. Control is based on the more critical (usually the smaller) of the two phase differences. This dynamically switches which of the two oscillations is used as the decisive factor for control. This mode promises the greatest stability, especially when the oscillations do not exhibit a restoring force that varies linearly with the deflection according to Hooke's law.but the restoring force at least (also) has a cubic term (Duffing oscillator). In such an oscillator, instability of the oscillation can fundamentally occur depending on the drive frequency and / or drive phase, so that undesirable jumps can occur at certain points on the amplitude / drive frequency characteristic curve when the drive frequency is varied. Case (iii) counteracts the risk of such jumps by adjusting the drive frequency during control in such a way that the jumps are avoided. In some embodiments, in particular also for the reasons stated for case (iii), during control in the steady state of the first oscillation, the first drive phase is limited such that it corresponds to the measured actual phase of the first oscillation by less than 90°, in particular by 85° or less.and / or in the steady state of the second oscillation, the second drive phase is limited so that it leads the measured actual phase of the second oscillation by less than 90°, in particular by 85° or less. This is done against the background that, for the Duffing oscillator, the associated oscillation equation indicates that the largest amplitude is to be expected with a drive phase that leads the actual phase by 90°.However, the range above 90° is unstable. In some embodiments, within the scope of the control with respect to at least one of the oscillations, a correction variable for the drive phase of the oscillation, defined via at least one adjustable parameter, is used to determine a control variable for the control of this oscillation. The correction variable can be used in particular to correct systematic phase measurement errors when determining the actual phase. This allows for the implementation of an even more precise trajectory tracking control. In some embodiments, within the scope of the control with respect to at least one of the oscillations, a phase shift dependent on a dead time of an image processing process for images to be imaged using the microscanner system is used to determine a control variable for the control of this oscillation. This can be achieved,that, despite the finite dead time, a modulation of the electromagnetic beam used for imaging or projection, e.g., a laser beam, is time-coordinated with the actual oscillation movement of the deflection element(s) of the microscanner system such that an undistorted or undisturbed image can be projected into the field of observation. A second aspect of the solution presented herein relates to a device, in particular an electrical (in particular electronic) circuit, for controlling a drive of a multi-axis microscanner system having a first oscillation axis and a second oscillation axis running non-parallel thereto. The device comprises: (i) a reference information source for generating reference information defining a simultaneous, in particular harmonic, reference oscillation about the first and second oscillation axes, such that the reference information,define an associated reference frequency and an associated reference phase of the reference oscillation for each of the first and second oscillation axes; 119077P1280PC (ii) a control device for generating control signals for controlling a drive device of the microscanner system in order to cause the microscanner system, via the drive device controlled by means of the control signals, to (ii-1) drive a first rotary oscillation of a deflection element of the microscanner system about the first oscillation axes by means of an excitation at a first drive frequency (^1), and (ii-2) drive a second rotary oscillation of a deflection element of the microscanner system about the second oscillation axis, carried out simultaneously with the first oscillation, by means of an excitation at a second drive frequency (^1). The control device has a control system and is configured to generate the control signals in such a way,that, with respect to each of the oscillations, the respective drive frequency and / or drive phase is / are varied over time by means of the control system in such a way that, with respect to the oscillation axis assigned to the respective oscillation, a deviation of the respective oscillation in terms of frequency and phase from the reference oscillation is counteracted. The device is thus, in particular, also configured to carry out the method according to the first aspect. Accordingly, one or more of the following variants already explained in relation to the method can also apply to the device: The deflection element executing the first oscillation and the deflection element executing the second oscillation can either be identical (multi-axis oscillation of a deflection element) or different (e.g., two deflection elements each oscillating on a single axis). The drive device can, in particular, have a separate drive for each oscillation axis.which can in particular each have one or more actuators, in particular piezo actuators. Such actuators can in particular be arranged on or in a suspension of the deflection element(s) in order to excite the respective associated deflection element to oscillate by exerting force on the suspension. The first and second drive frequencies can in particular also be defined as angular frequencies. In some embodiments, the reference information source is configured to determine the reference frequencies and the reference phases of the reference oscillation depending on at least the following input variables: 119077P1280PC (i) a setting parameter common to both oscillation axes for setting a repetition rate of the reference oscillation; (ii) a first setting parameter assigned to the first oscillation axis and a second individual setting parameter assigned to the second oscillation axis,The shape of the reference oscillation can be determined based on the two individual setting parameters. Thus, the shape of a trajectory (in particular in the form of a Lissajous figure) can also be determined, which results from deflecting an electromagnetic beam, in particular a laser beam, using the deflection element(s) of the microscanner system when the latter executes the reference oscillation. In some embodiments, the reference information source is further configured to determine the reference frequencies and the reference phases of the reference oscillation additionally as a function of a start phase setting parameter as a further input variable, which defines a start phase for 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 a Lissajous figure, in particular, a rotation angle of the figure can be set. In particular, a setting can be selected,in which only few or no degeneracies, i.e. coincidence of several crossing points of the trajectory, occur. This in turn serves the goal of achieving the highest possible image quality, in particular line density and / or homogeneity. In some embodiments, the control system has a control loop for controlling the drive frequency and / or the drive phase of the first oscillation and a separate control loop for controlling the drive frequency and / or the drive phase of the second oscillation. Thus, each of the two oscillations can be optimally adjusted independently of the other oscillation. However, it is also possible, as already explained above with regard to embodiments of the method according to the first aspect, that the separate control loops are coupled in such a way that the common factor which defines the repetition rate of the reference oscillation,is determined depending on the actual phases of both oscillations and is used to establish both reference frequencies. In some embodiments, the device itself also comprises the drive device. The device is then already capable of defining and driving the first and second oscillations of the microscanner system. 119077P1280PC In some embodiments, the device is further configured to generate the control signals such thatthat the drive device can thus be controlled according to one or more of the embodiments of the method described herein according to the first aspect. The features and advantages already explained with regard to the method thus also apply accordingly to the device. A third aspect of the solution presented herein relates to a microscanner system for deflecting an electromagnetic beam. It comprises: (i) a multi-axis microscanner with two different non-parallel, in particular mutually orthogonal, oscillation axes or a combination of several individual, in particular two, single-axis microscanners arranged such that the incident beam can be deflected successively by the various individual microscanners of the microscanner system to generate a Lissajous figure; and (ii) a device according to the second aspect for controlling a drive of the microscanner system by the drive device. Further advantages,Features and possible applications of the present solution will become apparent from the following detailed description in conjunction with the figures. Figure 1 schematically shows an exemplary embodiment of a projection arrangement with a microscanner system for scanning an observation field with an electromagnetic beam, in particular a laser beam, deflected by the microscanner system; Figure 2 schematically shows an exemplary embodiment of a signal flow diagram of a reference information source for generating reference information.which together define a simultaneous reference oscillation about a first and a second oscillation axis of a multi-axis microscanner system; Fig. 3 schematically shows an exemplary embodiment of a signal flow plan for a trajectory tracking control for controlling a drive of a multi-axis microscanner system; 119077P1280PC Fig. 4 shows, in comparison, exemplary amplitude and phase responses of a harmonic oscillator with a restoring force that is linearly dependent on the deflection, and of a Duffing oscillator; and Fig. 5 schematically shows a further exemplary embodiment of a signal flow plan for an extended control with a combined trajectory tracking control and resonance tracking control for controlling a drive of a multi-axis microscanner system. In the figures, identical reference numerals denote identical,Similar or corresponding elements and elements shown in the figures are not necessarily shown to scale. Rather, the various elements shown in the figures are shown in such a way that their function and general purpose will be understood by those skilled in the art. Connections and couplings between functional units and elements shown in the figures can, unless expressly stated otherwise, also be implemented as indirect connections or couplings. Unless specifically stated otherwise, functional units can, in particular, be implemented as hardware, software, or a combination of hardware and software. Fig. 1 illustrates an exemplary embodiment 100 of a microscanner system comprising a two-axis microscanner 125 for scanning an observation field 115 with a laser beam 110a deflected by the microscanner 125, as well as a device 135,in particular an electrical circuit for controlling a drive of the microscanner system 100 having a first oscillation axis and a second oscillation axis running non-parallel, in particular orthogonal thereto. The microscanner system also has a laser source 105. The microscanner system 100 is configured such that a laser beam 110a generated by the laser source 105 can be directed into the observation field indirectly by way of a mirror image on a deflection element (mirror) 125a of the microscanner 125 that simultaneously oscillates about two mutually orthogonal oscillation axes. The laser beam 110 is guided across the observation field by the oscillating deflection element (mirror) 125a, for example, which is gimballed, in the sense of a scan, thus enabling the illumination of a solid angle. In the example of Fig. 1, this is done using a two-dimensional,A substantially harmonic oscillation of the deflection element 125a, which results in a two-dimensional trajectory, in particular a Lissajous figure, 130 as an irradiation pattern. This oscillation can be effected by a suitable, in particular harmonic, control of a drive (not shown in Fig. 1) of the microscanner 125 controlled by the device 135 and results from a superposition of a first oscillation about the first oscillation axis and a second oscillation about the second oscillation axis. If at least one object 115 (e.g., a projection surface) is located in the observation field, which at least partially reflects the deflected laser beam 110a on its surface to provide a reflected beam 110b,Thus, the trace of the reflection point of the laser beam 110b on the surface (or, in the case of multiple objects, on multiple object surfaces) forms a linear trajectory. With a fixed radiation direction of the laser source 105, the course of the trajectory 130 is essentially determined by the oscillating movement of the mirror 125a of the microscanner 125. In Fig. 1, the laser beam 110b is shown as an example for a point in time during the passage through the irradiation pattern. Fig. 2 illustrates, in the form of a signal flow diagram 200, a reference information source for generating reference information, in particular reference signals, which represent a simultaneous reference oscillation about the first and second oscillation axes of a microscanner system, for example, the microscanner 125 of the microscanner system 100 from Fig. 1.The reference information defines an assigned reference (angular) frequency ^ for the first oscillation axis (indicated by the index "a" in Fig.2) and for the second oscillation axis (indicated by the index "b" in Fig.2). ref,a or ^ ref,band an associated reference phase ^ref,a or ^ref,b of the reference oscillation. The input variables to the signal flow plan 200 are (i) a factor LPS, which is assigned to both oscillations as a common setting parameter and specifies a repetition rate of the Lissajous figure, e.g., in Hz, (ii) the axis-related individual setting parameters M for the first oscillation axis and N for the second oscillation axis, (iii) and a starting phase γ of the oscillation relative to one of the oscillation axes, here, for example, relative to the first oscillation axis. To obtain the respective angular frequencies ^ref,a or ^ref,b of the two-dimensional reference oscillation (or, equivalently, of the first and second oscillations), the associated individual setting parameter M or N is multiplied by a value resulting from a multiplication 205 of the factor LPS by 2π (110, 115). By integrating 220 or 225 of the respective angular frequency ^ref,a or^ref,b 119077P1280PC Over time, the reference phases ^ref,a and ^ref,b of the reference oscillation result. The reference phases ^ref,a and ^ref,b and the reference travel frequencies ^ref,a and ^ref,b represent output variables of the signal flow plan 200 and define the reference oscillation and thus indirectly also a corresponding Lissajous trajectory 130. The signal flow plan 200 can be implemented in the device 135 in particular by an electrical, in particular electronic, circuit or computer-implemented using at least one computer program executable on a processor platform, or a combination of both. Fig. 3 shows schematically in the form of a signal flow plan an exemplary embodiment 300 for a trajectory tracking control for controlling a drive of a multi-axis microscanner system, such as the microscanner system 100 from Fig. 1.To generate reference information, in particular reference signals that define a two-dimensional reference oscillation, the signal flow diagram 300 contains the signal flow diagram 200 of the reference information source from Fig. 2 as a component. In addition to the reference information source, the trajectory tracking controller 300 has a control loop for each oscillation axis or each of its respective drives for controlling a drive phase for the respective oscillation axis. For reasons of clarity, only the control loop for the first oscillation axis "a" is illustrated in Fig. 3, while the control loop for the second oscillation axis "b", which has the same structure as the control loop for the first oscillation axis, is largely not shown. Therefore, the following only addresses the control loop for the first oscillation axis, although the explanations can also be applied to the control loop for the second oscillation axis.A manipulated variable in the control loop of Fig. 3 is the drive angular frequency ^drv,a for driving the first oscillation around the first oscillation axis. At the start of the control, the reference angular frequency ^ref,a is directly pre-controlled as the drive angular frequency ^drv,a and initially largely determines ^drv,a. The manipulated variable ^drv,a is then integrated in a drive phase accumulator 305a to obtain a drive phase ^drv,a. An electronic driver 310a generates an electronic drive signal from this for the drive (e.g., one or more piezo actuators) for the first oscillation, which can in particular be an oscillation around a first oscillation axis of a two-axis microscanner 315. 119077P1280PC The actual phase position of the first oscillation is determined by means of a phase detection 320a.For this purpose, an actual phase of the first oscillation can be measured using one or more piezo sensors, and a phase difference signal ^sen,a can be derived from this, which represents a phase difference between the measured actual phase and the drive phase ^drv,a. From the drive phase ^. drv,a is with the phase difference signal ^ sen,a and optionally a static correction value C with respect to the drive phase ^drv,a to eliminate systematic measurement errors of the actual phase, an image phase ^im,a (e.g. ^im,a = ^drv,a + ^sen,a + C) is generated. This image phase ^ im,ais used in the example for image projection and pixel addressing within the framework of a projection of an electromagnetic beam into an observation field according to Fig. 1, in order to select the next pixel to be projected into the observation field in an image to be projected. By subtracting a dead time D, which occurs during image processing in an image processing unit 325a, from the image phase ^im,a, a momentary (mechanical) phase ^mech,a of the first oscillation is obtained. The image phase ^im,a thus precedes the (mechanical) phase ^ mech,aby the dead time D, so that the image values ​​for the image points (pixels) of the projection image to be displayed are retrieved from an image source, e.g. an image data memory, in such a timely manner as a function of the image phase that their projection takes place after the dead time D has elapsed exactly when the microscanner system projects in the projection direction assigned to the respective image point according to the (mechanical) phase ^mech,a. In this way, it can be ensured that each image point of the image to be projected is actually displayed at the location intended for it in the image projected into the field of observation. This phase ^mech,a is compared via a feedback loop with the reference phase ^ref,a provided by the reference information source in order to determine a control difference e, which is then fed to a controller 330a, which can in particular be designed as a P controller.The controller 330a generates an angular frequency shift as the control variable, which corresponds to the reference angular frequency ^. ref,ais added to obtain an adjusted value for the drive phase ^drv,a. As long as a control difference exists, the drive oscillation is accelerated or decelerated relative to the reference oscillation by the control loop in order to bring both oscillations into phase. As soon as this control target is reached, the drive angular frequency ^drv,a and the reference angular frequency ^ref,a are identical again. 119077P1280PC This applies accordingly to the control loop for the second oscillation axis "b", which is only incompletely indicated in Fig. 3 by dashed arrows and the reference numerals 310b (electronic driver) and 320b (phase detection). Depending on the design, a deflection element of the microscanner system, together with its suspension, can in particular have the characteristics of a non-linear Duffing oscillator or can be well approximated thereby. Fig.For comparison, Figure 4 shows exemplary amplitude and phase responses 400 of, on the one hand, a harmonic oscillator with a restoring force linearly dependent on the deflection (solid curves in Figure 4), and, on the other hand, a Duffing oscillator (dashed curves in Figure 4), each in the case of a forced oscillation driven by a drive angular frequency ^. While the harmonic oscillator, as a function of the drive angular frequency ^, exhibits a stable amplitude curve with a maximum at a resonance or natural frequency. ^0of the harmonic oscillator and a phase of -90° (= -^ / 2), however, with the Duffing oscillator, a phase below -90° (= -^ / 2) results in an unstable region in which the amplitude of the oscillation collapses suddenly. For this reason, an operating point with a phase slightly greater than -90°, e.g., at -80°, is usually selected. There, the amplitude is still large, but some distance from the unstable region is maintained. Fig. 5 schematically illustrates another exemplary embodiment 500 of a signal flow plan for an extended control loop with combined trajectory tracking and resonance tracking control for controlling a drive of a multi-axis microscanner system. This extended control loop is intended to ensure that both oscillations remain in their respective resonant angular frequency range so that (due to resonance) large amplitudes can be maintained.The resonant angular frequency range includes not only the value of a resonant angular frequency ^0 itself, but also a surrounding angular frequency range in which the resonance occurs at least approximately (cf. amplitude response in Fig. 4). For example, the resonant angular frequency range (resonance range) can be defined by [0.96 ^0; 1.04 ^0]. The extended control loop has an additional feedback loop (shown in dotted lines). For this purpose, the lower phase value ("MIN") is first selected from the actual phases ^sen,a and ^sen,b determined for the two oscillations by means of the two phase detections 320a and 320b. In the case of a microscanner that can be written to by a 119077P1280PC Duffing oscillator, this measured value, as shown in Fig. 4, is closer to the unstable region of the oscillation and can therefore be referred to as the "critical" value.This critical value is compared with a defined setpoint SP to determine a control deviation. A PID controller 335 then manipulates the repetition rate LPS of the Lissajous figure and thus the two reference angular frequencies ^, depending on the control deviation and via a multiplier. ref,a or ^ ref,band subsequently via the phase control described above (for each oscillation also the drive phases ^drv,a and ^drv,b). In this way, resonant operation of the oscillations can be ensured. The spatial properties of the resulting trajectory (in particular the Lissajous figure) are retained. It is simply traversed at a slightly different speed. In this way, a Lissajous figure previously selected using the setting parameters N, M and ^ can be maintained. In particular, the mesh size, position of the crossing points in the Lissajous figure and other properties can be ensured. This makes it possible to create a flicker-free and consistent image impression during projection. Scan patterns that can be kept stable in this way can also be selected specifically for 3D sensing applications (e.g. in the sense of "structured light").When using machine learning-based image analysis in such 3D sensing applications, the same Lissajous figure can be reliably used in a virtual projection simulation (especially in the context of a machine learning training process) and in a real-world projection. This simplifies the machine learning process because the training space and the real-world image analysis can be limited to the same predetermined Lissajous figure (same setting parameters N, M, and ^). By selecting the lower value ("MIN") from the actual phases ^. sen,a and ^ sen,bAs a controlled variable, high system stability is ensured. Dynamically varying the repetition rate LPS enables resonant operation over a wide range of parameter fluctuations in the microscanner system. This enables, for example, operation in a broad temperature range. While at least one exemplary embodiment has been described above, it should be noted that a large number of variations exist. It should also be noted that the described exemplary embodiments represent only non-limiting examples and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein.Rather, the foregoing description will provide one skilled in the art with guidance for implementing at least one exemplary embodiment, it being understood that various changes may be made in the operation and arrangement of the elements described in an exemplary embodiment without departing from the subject matter as defined in the appended claims, as well as their legal equivalents.

[0002] 119077P1280PC LIST OF REFERENCE SYMBOLS 100 Microscanner system 105 Laser source 110a Laser beam 110b Reflected beam 115 Object in the field of observation 125 Microscanner 125a Deflection element (mirror) 130 Trajectory, in particular Lissajous figure 135 Device for controlling a drive of the microscanner system 100 200 Reference information source, in particular its signal flow plan 205 Multiplication or multiplication unit 210 Further multiplication or multiplication unit, for oscillation axis b 215 Further multiplication or multiplication unit, for oscillation axis a 220 Integration or integration unit, for oscillation axis b 225 Integration orIntegration unit, for oscillation axis a 300 Trajectory tracking control 305a Drive phase accumulator 310a Electronic driver for oscillation axis a 310b Electronic driver for oscillation axis b 315 Microscanner 320a Phase detection for oscillation axis a 320b Phase detection for oscillation axis b 325a Image processing process or unit 330a Controller 335 PID controller 400 Amplitude and phase responses 500 Trajectory tracking control with resonance follower N Individual setting parameter for oscillation axis b M Individual setting parameter for oscillation axis a γ Start phase setting parameter LPS Common setting parameter (in particular factor) for both oscillations, determines trajectory repetition rate C Correction variable D Dead time 119077P1280PC SP Setpoint ^ref,a Reference (angular) frequency for oscillation axis a ^ref,b Reference (circular) frequency for oscillation axis b ^. ref,aReference phase for oscillation axis a ^ref,b Reference phase for oscillation axis b ^drv,a Drive frequency for oscillation axis a ^ drv,b Drive frequency for oscillation axis b ^drv,a Drive phase for oscillation axis a ^drv,b Drive phase for oscillation axis b ^ sen,a Phase difference signal for oscillation axis a ^sen,b Phase difference signal for oscillation axis b ^ mech,a mechanical phase of oscillation ^ im,a Image phase ^ Drive angular frequency ^0 Resonance angular frequency ^^ Deviation from the resonance angular frequency ^0 to define a resonance range

Claims

119077P1280PC CLAIMS 1. A method for controlling a drive of a multi-axis micro-scanner system (100) having a first oscillation axis and a second oscillation axis running non-parallel thereto, the method comprising: generating reference information (^ref,a, ^ref,b, ^ref,a, ^ref,b) defining a simultaneous reference oscillation about the first and second oscillation axes, such that the reference information for the first and second oscillation axes each has an associated reference frequency (^ref,a, ^ref,b) and an associated reference phase (^ ref,a , ^ ref,b ) of the reference oscillation; controlling a drive device for the microscanner system (100) in such a way that the drive device is thereby caused to initiate a first rotary oscillation of a deflection element (125a) of the microscanner system (100) about the first oscillation axis by means of an excitation with a first drive frequency (^ drv,a), and to drive a second rotary oscillation of a deflection element (125a) of the microscanner system (100) about the second oscillation axis by means of an excitation with a second drive frequency (^drv,b), carried out simultaneously with the first oscillation; wherein the control of the drive device is carried out in such a way that, with respect to each of the oscillations, its respective drive frequency (^drv,a, ^drv,b) and drive phase (^ drv,a , ^ drv,b ) is / are varied over time by means of a control system in such a way that, with respect to the oscillation axis assigned to the respective oscillation, a deviation of the respective oscillation in terms of frequency and phase from the reference oscillation is counteracted.

2. Method according to claim 1, wherein the control of the drive device is carried out in such a way that the driving of the first oscillation with the first reference frequency (^ ref,a) is pre-controlled and / or the driving of the second oscillation with the second reference frequency (^ref,b) is pre-controlled, before the temporal variation of the respective drive frequency (^ drv,a , ^ drv,b ) and drive phase (^ drv,a , ^ drv,b ) of the respective oscillation.

3. Method according to one of the preceding claims, wherein for at least one oscillation axis, the temporal variation of the drive frequency (^ drv,a , ^ drv,b ) and drive phase (^drv,a, ^drv,b) of the oscillation axis corresponding to 119077P1280PC Oscillation occurs within the scope of the control as a function of measurement information that represents a measured actual phase of the oscillation around this oscillation axis.

4. Method according to claim 3, wherein the temporal variation of the drive frequency and / or drive phase of the oscillation associated with this oscillation axis occurs within the scope of the control as a function of a phase difference (^ sen,a , ^sen,b) the actual phase of the oscillation represented by the measurement information and the corresponding phase (^ ref,a , ^ ref,b ) of the reference oscillation with respect to the oscillation axis associated with the oscillation.

5. The method according to claim 3 or 4, further comprising: for the at least one oscillation axis, monitoring the phase difference (^ sen,a , ^ sen,b ) between the drive phase (^ drv,a , ^ drv,b) and the actual phase of the oscillation associated with this oscillation axis; and if, within the scope of the monitoring, a change in the phase difference (^sen,a, ^sen,b) is detected for this oscillation axis, varying the respective drive frequencies (^drv,a, ^drv,b) for the first oscillation and the second oscillation within the scope of the control by raising or lowering them by a factor (LPS) that is the same for both oscillations, wherein the factor (LPS) is selected such that, with respect to the at least one oscillation axis, a drift of the angular frequency of the associated oscillation out of a defined resonance range of the oscillation is counteracted. 6.Method according to claim 5, wherein the control is carried out in such a way that the factor is determined as a function of one of the following variables: ^ determined phase difference (^sen,a, ^sen,b) between the drive phase and the actual phase of only one preselected oscillation; ^ mean value of the determined respective phase differences (^sen,a, ^sen,b) between the respective drive phase (^. drv,a , ^ drv,b ) and the respective actual phase of the first oscillation on the one hand and the second oscillation on the other hand; ^ determined phase difference (^sen,a, ^sen,b) between the drive phase (^ drv,a , ^ drv,b ) and the actual phase of only one of the oscillations, whereby this oscillation is dynamically selected from the two oscillations during the control as the one which is the smaller of the phase differences (^sen,a, ^sen,b) among the phase differences (^sen,a, ^sen,b) last detected over time. 119077P1280PC 7. Method according to one of the preceding claims, wherein, within the scope of the control in the steady state of the first oscillation, the first drive phase (^drv,a) is limited such that it leads the measured actual phase of the first oscillation by less than 90°, in particular by 85° or less; and / or in the steady state of the second oscillation, the second drive phase (^drv,b) is limited such that it leads the measured actual phase of the second oscillation by less than 90°, in particular by 85° or less.

8. Method according to one of the preceding claims, wherein, within the scope of the control with respect to at least one of the oscillations, a correction variable (C) defined via at least one adjustable parameter for the drive phase (^ drv,a , ^ drv,b) of the oscillation is included in the determination of a controlled variable of the control for this oscillation.

9. Method according to one of the preceding claims, wherein, within the scope of the control with respect to at least one of the oscillations, a phase shift dependent on a dead time (D) of an image processing process (325a) for images to be imaged by means of the microscanner system (100) is included in the determination of a controlled variable of the control for this oscillation.

10. Device (135), in particular an electrical circuit, for controlling a drive of a multi-axis microscanner system (100) with a first oscillation axis and a second oscillation axis running non-parallel thereto, wherein the device (135) comprises: a reference information source (200) for generating reference information (^ ref,a , ^ ref,b , ^ ref,a , ^ ref,b), which define a simultaneous reference oscillation around the first and second oscillation axes, so that the reference information (^ ref,a , ^ ref,b , ^ ref,a , ^ ref,b ) for the first and second oscillation axes each have an assigned reference frequency (^ref,a, ^ ref,b ) and an associated reference phase (^ ref,a , ^ ref,b ) of the reference oscillation; a control device for generating control signals for controlling a drive device of the microscanner system (100) in order to 119077P1280PC Microscanner system (100) to cause, by the drive device controlled by means of the control signals, a first rotary oscillation of a deflection element (125a) of the microscanner system (100) about the first oscillation axis to be driven by means of an excitation with a first drive frequency (^drv,a), and a second rotary oscillation of a deflection element (125a) of the microscanner system (100) about the second oscillation axis to be driven simultaneously with the first oscillation by means of an excitation with a second drive frequency (^drv,b); wherein the control device has a control and is configured to generate the control signals in such a way that, with respect to each of the oscillations, its respective drive frequency (^ drv,a, , ^ drv,b ) and drive phase (^ drv,a , ^ drv,b) is / are varied over time by means of the control system in such a way that, with respect to the oscillation axis assigned to the respective oscillation, a deviation of the respective oscillation in terms of frequency and phase from the reference oscillation is counteracted.

11. The device (135) according to claim 10, wherein the reference information source (200) is configured to supply the reference frequencies (^ref,a, ^ref,b) and the reference phases (^ ref,a , ^ ref,b) of the reference oscillation as a function of at least the following input variables: ^ a setting parameter (LPS) common to both oscillation axes for setting a repetition rate of a Lissajous figure corresponding to the reference oscillation; ^ a first individual setting parameter (M) assigned to the first oscillation axis and a second individual setting parameter (N) assigned to the second oscillation axis, wherein the shape of the reference oscillation can be determined based on the two individual setting parameters (N, M).

12. Device (135) according to claim 11, wherein the reference information source (200) is further configured to determine the reference frequencies (^ref,a, ^ref,b) and the reference phases (^ref,a, ^ref,b) of the reference oscillation additionally as a function of a start phase setting parameter (γ) as a further input variable, which defines a start phase for one of the two reference phases (^ ref,a , ^ ref,b) of the reference oscillation. 119077P1280PC 13. Device (135) according to one of claims 10 to 12, wherein the control comprises a control circuit for controlling the drive frequency (^drv,a) and the drive phase (^drv,a) of the first oscillation and a separate control circuit for controlling the drive frequency (^ drv,b) and the drive phase (^drv,b) of the second oscillation.

14. The device (135) according to any one of claims 10 to 13, wherein the device (135) further 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 signals such that the drive device can be controlled thereby according to the method according to 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) with two different non-parallel oscillation axes or a combination of several individual, in particular two, single-axis microscanners arranged such that the incident beam (110a) can be deflected successively by the various individual microscanners (125; 315) of the microscanner system (100) to generate a Lissajous figure; and the device (135) according to claim 15 for controlling a drive of the microscanner system (100) by the drive device.

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