Microscanner having a projection system and coupled oscillator for projecting a lissajous figure

Abstract

A projection system for projecting a Lissajous figure onto an observation field comprises a microscanner, which has a deflection unit with a deflection element for deflecting an incident electromagnetic beam, a support structure and a spring device, with which the deflection element is suspended in a gimbal-less manner on the support structure such that it can simultaneously perform a first rotational oscillation about a first oscillation axis and a second rotational oscillation about a second oscillation axis orthogonal thereto, with respect to the support structure, and cause a nonlinear Lissajous projection in the observation field by deflecting the electromagnetic beam incident on the deflection element during the simultaneous oscillation. The microscanner also has a control device configured to actuate the drive device for driving the deflection unit such that a respective, particularly resonant, drive effect for at least one of the oscillations of the deflection element is individually settable. Furthermore, the spring device is designed to mediate an amplitude-dependent mutual coupling between the oscillations. The control device is also configured to actuate the drive device as a function of the at least one detected state variable of the first vibration to induce a drive effect on the second vibration by affecting at least one state variable of the second vibration, which counteracts falling below a predetermined minimum frequency distance between the instantaneous vibration frequencies of the first and second vibrations, respectively.

Description

[Technical Field]

[0001] The present invention relates to a projection system for projecting a Lissajous figure onto an observation field, and to a microscanner for such a projection system. [Background technology]

[0002] In the case of microscanners, these are also referred to in technical terms as "MEMS scanners," "MEMS mirrors," or "micromirrors," and in English as "microscanners," "microscanning mirrors," or "MEMS mirrors." They are microelectromechanical systems (MEMS), more precisely, micro-optoelectromechanical systems (MOEMS), from the class of micromirror actuators for the dynamic modulation of electromagnetic radiation, especially visible light. Depending on the design, the modulation movement of a single mirror can be translational or rotational around at least one axis. In the first case, a phase shift effect is achieved, and in the second, a deflection of the incident electromagnetic radiation is achieved. Below, we consider microscanners in which the modulation movement of a single mirror is rotational. In the case of microscanners, modulation is generated via a single mirror, in contrast to mirror arrays, in which the modulation of the incident light is achieved via the interaction of multiple mirrors.

[0003] Microscanners are used, in particular, to deflect electromagnetic radiation, modulating the incident electromagnetic beam with respect to its deflection direction using deflection elements ("mirrors"). In particular, this can be used to generate a Lissajous projection of the beam within a field of view. For example, imaging sensory tasks can be solved or display functions can be implemented. In addition, such microscanners can also be used advantageously to irradiate and process materials. Other possible applications lie in the field of illuminating or lighting open or closed spaces or spatial regions using electromagnetic radiation, for example in the context of headlight applications.

[0004] In both the case of an imaging sensor and in the case of a display function, beam deflection systems, in particular microscanners, are used to deflect electromagnetic radiation, such as a laser beam or a shaped beam from another electromagnetic radiation source, at least in two dimensions, for example horizontally and vertically, to scan or illuminate an object surface within the observation field.

[0005] A deflection device for a projection system for projecting a Lissajous figure onto an observation field is known from European Patent No. EP 2514211 B1, which is designed to deflect a light beam around at least one first and second deflection axis to generate the Lissajous figure. The deflection device includes a deflection unit for generating oscillations around the deflection axis and an activation device for generating activation signals for the deflection unit at first and second activation frequencies corresponding to the resonant frequencies of the deflection unit. The deflection unit has a quality factor of more than 3,000. The activation device includes a first control loop designed to control the first and / or second activation frequencies depending on a measured phase position of the oscillations of the deflection unit so that the maximum amplitude of the oscillations remains within the resonant range of the deflection unit, and the activation frequencies do not have a fixed integer ratio. The activation device further comprises a second control loop, which is designed to influence the resonant frequency of the first and / or second deflection axes depending on the line density of the Lissajous figure predetermined by the activation frequency, so that the line density is within a predetermined tolerance. The two deflection axes are decoupled using Cardan suspensions (gimbals), so that the relative vibrations about the two axes are completely decoupled from each other and are phase-controlled completely independently of each other, aiming to keep each of the two axes in resonance.

[0006] For the deflection device from EP 2514211 B1 the following relationship applies: f 1R ≠f 2R , (1) where f 1R denotes the resonance frequency of the first axis, and f2R denotes the resonant frequency of the second axis. For the mechanical torque T1 or T2 generated by the curved spring of the first or second axis, respectively, the following formula applies: T1=k1*θ1 and T2=k2*θ2(2) where θ1 and θ2 denote the respective mechanical amplitudes (deflection angles) of the mirror in the first and second axes, respectively, and k1 and k2 denote the respective spring constants of the springs in the first and second axes, respectively. Due to the decoupling of the oscillation axes, it is particularly easy to achieve at least approximately rectangular illumination of the observation field with a Lissajous figure using such a gimbal-based microscanner.

[0007] However, in addition to gimbal-based microscanners with completely decoupled axes, microscanners without gimbals (so-called "gimbal-less mirrors" or "gimballess" microscanners or mirrors) are also known, which implement two or more oscillation axes without a Cardan suspension of the mirror, and in which non-negligible, particularly strong, coupling between the individual oscillation axes can occur. The strength of such coupling may depend, inter alia, on the amplitude.

[0008] A microscanner type is mentioned here by way of example, which has a deflection unit with a mirror plate suspended on a surrounding frame by means of three rotationally symmetrically arranged spring elements, resulting in a biaxial microscanner. A variation of this type of microscanner, illustrated in Figure 3, is known under the name "MiniFaros" mirror and is described in particular in Hofmann et al., "Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning," J. Micro / Nanolith. MEMS MOEMS, 3-11 Jan-Mar 2014 / Vol. 13(1)."

[0009] Due to coupling between the vibration axes and the associated respective vibrations of the mirror about each one of these vibration axes, gimbal-less mirrors tend to have resonant frequencies for the various vibration axes quickly approach one another as they vibrate, resulting in only essentially elliptical (and therefore linear, non-planar) Lissajous illumination of the observation field. In particular, at least approximately planar, and especially at least approximately rectangular, illumination of the observation field is therefore made more difficult or even impossible. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent No. 2514211B1 [Non-patent literature]

[0011] [Non-Patent Document 1] Hofmann et al., Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning, J. Micro / Nanolith. MEMS MOEMS, 3-11 Jan-Mar 2014 / Vol. 13(1) Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention aims to provide an improved gimbal-less microscanner with coupled oscillation axes, and a projection system equipped therewith, which can be used to achieve planar Lissajous illumination of an observation field. In particular, it is desirable to create the possibility of achieving at least approximately rectangular illumination with such a microscanner. [Means for solving the problem]

[0013] This object is achieved according to the teaching of the independent claims. Various embodiments and refinements of the invention are the subject of the dependent claims.

[0014] A first aspect of the present invention relates to a microscanner for a projection system that projects a Lissajous figure onto an observation field. The microscanner includes: (i) a deflection element for deflecting an incident electromagnetic beam, particularly by reflection; (ii) a support structure; and (iii) a deflection unit having a spring device. The spring device may include one or more spring elements. The deflection element is suspended in a gimbal-less manner by the spring device on the support structure so as to simultaneously perform a first rotational oscillation about a first oscillation axis and a second rotational oscillation about a second oscillation axis orthogonal to the first oscillation axis with respect to the support structure, and deflects the electromagnetic beam incident on the deflection element during the simultaneous oscillation, thereby generating a nonlinear Lissajous projection within the observation field.

[0015] The microscanner also comprises a control device configured to operate the drive devices for driving the deflection units such that the respective, particularly resonant, drive effects for at least one of the vibrations of the deflection elements are individually settable.

[0016] Furthermore, the spring device is designed to mediate amplitude-dependent mutual coupling between the vibrations.

[0017] The control device is also configured to actuate the drive device as a function of the at least one detected state variable of the first vibration to induce a drive effect on the second vibration by affecting at least one state variable of the second vibration, whereby the drive effect counteracts falling below a predetermined minimum frequency distance between the instantaneous vibration frequencies of the first vibration and the second vibration, respectively.

[0018] "Lissajous projection" in the sense of the present invention is to be understood in particular as scanning of an observation field with the aid of electromagnetic radiation, which is caused by at least two mutually orthogonal harmonic oscillations of a deflection element that deflects the radiation into the observation field.

[0019] "Nonlinear Lissajous projection" in the sense of the present invention should be understood as a special case of Lissajous projection, which is the scanning or illumination of an observation field with the aid of electromagnetic radiation, caused by at least two mutually orthogonal, not strictly harmonic, oscillations about associated oscillation axes of a deflection element that deflects the radiation into the observation field. In particular, the amplitude of at least a first of these oscillations may be modulated with respect to the first oscillation axis as a function of the instantaneous amplitude of the oscillation with respect to at least one other oscillation axis, such that the at least first oscillation does not represent a linear oscillation, i.e. does not obey Hooke's law with an amplitude-independent oscillation spring constant.

[0020] An "axis" or synonymous "axis of oscillation" in the sense of the present invention is to be understood as the axis of rotation (axis of rotation) of a rotary motion. This is a straight line that defines or describes a rotation or turn.

[0021] A "drive device" in the sense of the present invention should be understood as a device comprising one or more actuators for driving the deflection unit, i.e. for simultaneous rotational oscillation of the deflection element relative to the support structure and relative to at least a first and a second, possibly a third, oscillation axis.

[0022] As sometimes used herein, the words "comprise," "include," "involve," "includes," "have," "having," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method or device that comprises or includes a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such method or device.

[0023] Furthermore, unless otherwise specified, "or" means inclusive, not exclusive or. For example, condition A or B is satisfied by one of the following conditions: 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).

[0024] As used herein, the words "a" or "an" are defined as meaning "a / one or more" in the English original and "one or more" in the Japanese original. The phrases "another" and "further" and any other variations thereof should be understood to mean "at least one other."

[0025] The word "plurality" as used herein should be understood to mean "two or more."

[0026] In particular, one or more of the following advantages may be achieved with the aid of the microscanner described above, so that the above-mentioned objectives may be achieved:

[0027] Due to the special operation of the drive devices in the microscanner described above, it may be possible to achieve that, despite the existing coupling between the various vibrations or vibration axes, the vibration frequencies, in particular the resonant frequencies, of the individual vibrations maintain a minimum frequency distance from each other, so that there is no frequency synchronization of these frequencies for the different axes, which would ultimately result in an elliptical Lissajous figure, if any. This then allows for a constant, planar, and in particular one, essentially rectangular, illumination of the observation field within the projection framework, especially in the case of gimbal-less mirrors. Among other things, Lissajous-like excitation of the deflection elements (mirrors) can be achieved by the microscanner, even with many gimbal-less mirrors, even when the resonant frequencies of the different axes are close together, a situation that would not be possible without the above-mentioned type of control.

[0028] Since a gimbal-less mirror of the same mirror size generally has a smaller structural form than a gimbal-based mirror, a reduction in the required installation space can also be achieved with comparable projection results.

[0029] Since at least one of the oscillators (corresponding to oscillations about a particular oscillation axis) has nonlinear properties, i.e. does not comply with Hooke's law with an amplitude-independent spring constant throughout its amplitude range, a generally wider tuning range (frequency bandwidth) can be achieved, especially with a particularly high quality, especially in connection with gimbal-based mirrors.

[0030] Microscanners also open up the possibility of maintaining a defined frequency ratio over a wide temperature range, since temperature-related variations in the oscillator characteristics can also be compensated for with respect to maintaining a minimum frequency distance between the frequencies of the various oscillation axes. In the case of gimbal-less mirrors, the temperature-related variations in the oscillator characteristics typically occur simultaneously, in the same direction, and with equal strength for both oscillator axes, in contrast to gimbaled mirrors, which typically occur sequentially but to different degrees.

[0031] Even in the case of microscanners that have strongly coupled axes and are therefore clearly nonlinear, the above control can generally allow them to vibrate at different resonant frequencies for various axes, at least in two dimensions.

[0032] Preferred embodiments of the microscanner according to the first aspect are described below, which in each case can be combined as desired with each other and with other further described aspects of the invention, unless expressly excluded or technically impossible.

[0033] According to some embodiments, the control device is further configured to actuate the drive device as a function of at least one detected state variable of the second vibration to induce a drive effect on the first vibration by influencing at least one state variable of the first vibration, which counteracts a predetermined minimum frequency distance between the instantaneous vibration frequencies of the first and second vibrations. While the above-described basic form of the microscanner also allows for "primary-secondary" operation, in particular in the sense that only one of the vibrations (the secondary vibration) is affected as a function of at least one detected state variable of the other vibration (the primary vibration), in the described embodiment, both the first and second vibrations are affected, in particular equally, each as a function of at least one detected state variable of the respective other vibration. In this way, among other things, more diverse control options can be implemented, and particularly effective, particularly fast, automatic dynamic control of the vibrations involved can be achieved while avoiding frequency synchronization of amplitude-dependent operating frequencies, in particular resonant frequencies.

[0034] In contrast to this, according to some alternative embodiments, the control device is configured to actuate the drive device independently of the state variable of the second vibration to induce a drive effect on the first vibration while influencing at least one state variable of the first vibration. These embodiments therefore enable, in particular, the above-mentioned "master-slave" operation. A particularly simple implementation of the control device may be enabled here, since only one of the vibrations (in particular the second vibration) has to be controlled by the control device as a function of at least one state variable of the other (first) vibration.

[0035] According to some embodiments, each at least one state variable of each vibration is determined by its amplitude, frequency or phase, or as a function of at least one of these variables. In particular, at least one of the detected state variables can be determined by the amplitude of the vibration. This is particularly advantageous in that in the case of nonlinear vibrations, the spring stiffness k(θ) and therefore the frequency f(θ) for one axis are each a function of the amplitude θ for this axis, and therefore modulation of each other vibration as a function of the detected amplitude θ for this axis allows a minimum frequency distance to be ensured immediately, in particular in a dynamic manner.

[0036] According to some embodiments, the control device is configured to execute actuation of the drive device to induce a respective drive effect on at least one vibration driven thereby in the sense of closed-loop control as a function of the detected controlled variable, which is a state variable of each of the other vibrations or is defined as a function thereof, at least once repeatedly, particularly continuously. With the aid of such closed-loop control, dynamic actuation of the drive device can be achieved in a particularly efficient and optimized manner, aiming to ensure minimum frequency distances, and in particular, to react to unforeseen disturbances, which in principle would not be possible to the same extent with simple control without feedback. This also opens up the possibility of targeted compensation of nonlinear coupling effects, such as periodic variations in the amplitude-dependent spring stiffness of the spring device about at least one axis, which may otherwise cause distortions, in particular narrowing of the planar area of ​​the observation field illuminated by the microscanner. However, on the other hand, such nonlinear coupling effects can be amplified or deliberately modulated, depending on the application, to achieve a specific shape of the illuminated planar area, in particular a shape that deviates from an ellipse or rectangle. In headlight applications, this can be used in particular for static or dynamic shaping of the (flat cross-section) illumination area generated by the headlight system based on the microscanner. Consider here, for example, glare-free high beams for automobiles, where the light cone of the headlight is dynamically shaped in such a way that road users in the traffic area (and at the same time the field of view) who are at risk of being dazzled are automatically hidden from the high beam distribution.

[0037] According to some embodiments, the detection of the controlled variable can always be performed at the same amplitude of each other vibration, for example at the zero crossing of the vibration amplitude profile, in particular when the controlled variable for the drive control of each drive vibration is defined as the frequency or phase of each other vibration or as a function of at least one of these state variables. In this way, a closed-loop control that is particularly robust with respect to disturbances can be achieved, which typically has a lower measurement error due to measurement conditions that are always the same with respect to amplitude.

[0038] According to some embodiments, the control device may further be configured to execute both the first and second vibrations in the sense of a closed-loop control as a function of at least one iterative, in particular continuous, detected controlled variable, which is a state variable of, or is defined as a function of, the respective other vibrations, in which case these respective closed-loop controls of the first and second vibrations each include their respective rate of change and the control speed of each other closed loop control rate of change and is designed to be dynamically configurable as a function of the control speed. This tuning is advantageous in that it allows the axle to vibrate at approximately the same speed, and therefore the original resonance frequency of the axle to be shifted at approximately the same speed, towards higher frequencies, especially when the spring stiffness increases with increasing amplitude (English: "spring stiffening"). Due to the approximate synchronization of the frequency shifts, the minimum frequency distance for the difference between the shifting frequencies can be ensured in a particularly simple and reliable manner. Such a coordinated configuration of the control loops therefore makes it possible, in particular, to avoid the risk of one of the control loops controlling significantly faster than the other, and therefore of undesirable overlap of the resonance ranges, especially the resonance frequencies of the vibrations, so that the minimum frequency distance is not reached in an undesirable way, which results in only linear, especially elliptical, Lissajous projections depending on the object, instead of the desired planar, especially rectangular, illumination.

[0039] According to some embodiments, the control device is configured to operate the drive device to induce a respective drive effect on each vibration driven thereby in the sense of closed-loop control as a function of at least one detected state variable of each other vibration. Thus, in the sense of control technique, pure "control" of the drive device ("open-loop control") can be used here. Such open-loop control can advantageously be implemented with less implementation effort compared to the above-mentioned regulation. However, it can also be envisaged, in particular, to combine such open-loop control with at least one of the above-mentioned closed-loop controls. In particular, it is also possible for one vibration to have open-loop control and another vibration to have closed-loop control.

[0040] According to some of these control-based embodiments, the control device is configured to control the drive device to induce respective drive effects on the respective vibrations driven thereby, so that the drive device achieves a step-by-step increase in the amplitude or frequency of each of the first and second vibrations, alternating with each other. For example, the microscanner, or more precisely its deflection element, can be vibrated such that first the frequency f1 of the first vibration is incremented (i.e., increased by a defined frequency step), then the frequency f2 of the first vibration is incremented, then f1 is incremented again, then f2 is incremented again, and so on, until the desired drive frequency is reached. In this way, the vibration of the microscanner can also be achieved using a simple open-loop control, in which case there is no undesirable overlap of the resonance ranges, particularly the resonance frequencies of the oscillations, and therefore a minimum frequency distance is maintained, thereby avoiding a purely elliptical Lissajous projection instead of the desired planar, particularly rectangular, illumination of the object. The sequence of increments may, in particular, be irretrievably stored in a memory and, in particular, determined based on a previous calibration process. In addition to or alternatively to calibration, this allows the oscillations to be configured by defining and storing a desired sequence of increments.

[0041] According to some embodiments, the control device is also configured to actuate (i.e., control or regulate) the drive device so that the respective frequency of at least one of the vibrations, in particular the vibration that is primarily driven by this actuation, is within a predetermined limited resonance range surrounding the current resonance frequency of this vibration. Typically, the resonance frequency is the frequency f at which the maximum amplitude occurs. R The resonant frequency f is given by R The limits of the resonance range for R The value of f R ±70%, preferably f R ±40%, more preferably fR ±20%, more preferably f R ±10% (where the percentage is in each case the value f R This has the particular advantage that the maximum amplitude and therefore the greatest possible expansion of the illuminated area of ​​the observation field can be achieved within the resonance range, in particular at values ​​of f which are particularly relevant for large-area illumination.

[0042] According to some embodiments, the minimum frequency distance is fixed as a constant dimension, in particular this allows for a simple implementation, since once this variable is defined, no dependencies of any kind need to be taken into account for determining this variable, in particular not dynamically.

[0043] On the other hand, according to some alternative embodiments, the minimum frequency distance is current The amplitude, or amplitude of each of these two oscillations current The amplitude of the vibration is defined as a variable dimension that depends on the amplitude. In this way, better adaptability to different system conditions is possible. In particular, the vibration of the microscanner can be more precisely controlled in this way, and undesirable overlap of the resonance ranges on different axes can be effectively avoided when the frequency changes of these axes do not proceed at the same rate with vibration increase.

[0044] According to some alternative embodiments, the spring device is designed such that the strength of the amplitude-dependent mutual coupling between the first and second vibrations increases continuously with increasing amplitude of at least one of these two vibrations. This can be achieved in particular in that the spring device as a whole, or possibly its individual springs, are designed such that their respective spring stiffness k increases with increasing amplitude, i.e.: k=k(θ), where θ a >θ b For k(θ a )>k(θ b ) (3)

[0045] This is also known as "spring stiffening" or "stress stiffening." In this way, the following advantages, among others, can be provided: The frequency bandwidth or width of the resonance can be increased in a desired manner through this intentionally induced stiffening. The more pronounced this effect, the more suitable such a two-axis microscanner with a two-axis "spring stiffening" behavior is for unregulated open-loop operation (simply open-loop control), which is very easy to implement. If only one vibration exhibits this pronounced spring stiffening and the second vibration does not, it may be necessary to provide at least one vibration with closed-loop control, since the bandwidth may then in some cases not be sufficient for stable open-loop control. This situation is less advantageous than having two oscillator suspensions that exhibit pronounced spring stiffening. If the suspensions are designed so that the vibration with the higher resonant frequency exhibits "spring stiffening" and the other exhibits "spring lowering" behavior, it can be ensured that the vibrations do not approach each other and become synchronized, resulting in pure open-loop control, closed-loop control, or a combination thereof. If the suspension of the oscillator with the lower resonant frequency is designed with a "spring-stiffening" behavior and the suspension of the oscillator with the higher resonant frequency is designed with a "spring-lowering" behavior, an increase in amplitude can only be achieved by bringing the oscillation frequencies closer together. In principle, it is desirable to avoid this case, since it involves few usable characteristics. If both oscillators exhibit "spring-lowering" behavior, which is relatively difficult to achieve from a design point of view and therefore rarely occurs, an advantageously simple implementation based on pure open-loop control can be achieved with a correspondingly powerful formula, since the frequency bandwidth of the respective resonances allows for sufficient stability of the state. According to the present invention, the controller must still be designed so that the desired frequency distance is maintained. This state can then be stabilized again by an appropriate control loop.

[0046] According to some embodiments, the microscanner is designed as a two-axis microscanner, and the deflection unit comprises a deflection element suspended on a surrounding frame that acts as a support frame using three rotationally symmetrically arranged spring elements. In this case, the microscanner can in particular comprise a "MiniFaros" type deflection unit. Microscanners according to these embodiments typically have very strong coupling between the vibrations of the various axes and therefore strong nonlinear resonances. This then allows for a wide tuning range, i.e., a large bandwidth (e.g., about 200 Hz in some MiniFaros variants) (resonance range), over which the deflection element can oscillate resonantly.

[0047] According to some alternative embodiments, the microscanner is designed as a two-axis gimbal-less microscanner, in which (i) the deflection unit includes a deflection element that is firmly clamped and suspended on two opposite sides by flexible springs on a rigid frame used as a support frame, in particular a chip frame made of semiconductor material, and (ii) the flexible springs each have two arcuate sections that are connected to each other at their end faces and otherwise extend spaced apart from each other and around the deflection element, with the respective section of each flexible spring adjacent to the deflection element connected to the deflection element, and the respective section of each flexible spring adjacent to the frame connected to the frame. The deflection elements and the flexible springs, and optionally the frame, may be particularly integrally formed, i.e., manufactured from a single substrate. In such a microscanner, the stiffness of each spring for each axis depends on both the instantaneous amplitude of the deflection element for itself and the instantaneous amplitude of the deflection element for the other axis. Thus, during operation of the microscanner, the first vibration periodically modulates the second vibration, and vice versa. In addition, the two vibrations continuously exchange vibrational energy, temporarily storing energy in between. With such a mirror, planar illumination of an observation field, particularly having a deformed, particularly narrowed rectangular shape, may be achieved, and by appropriately operating the drive device to compensate for intermodulation, planar illumination of at least approximately rectangular shape may also be achieved.

[0048] According to some embodiments, the control device is configured to set the first vibration, the second vibration or at least one corresponding state variable of each of these two vibrations individually to a specific setpoint value in the context of actuating the drive device to drive the deflection unit in the sense of amplitude adjustment, frequency adjustment or phase adjustment. In particular, phase adjustment, in particular phase regulation, is suitable for causing operation-based, partial or complete compensation of intermodulation of the various vibrations and for maintaining resonant operation of the microscanner.

[0049] According to some embodiments, the deflection element is suspended in a gimbal-less manner on the support structure by means of a spring device that can simultaneously perform an additional third rotational oscillation relative to the support structure about a third oscillation axis, which is in each case orthogonal to the first and second oscillation axes, to generate a nonlinear Lissajous projection in the observation field by deflecting the electromagnetic beam incident on the deflection element during three simultaneous oscillations. The spring device is also designed to mediate amplitude-dependent mutual coupling between the third oscillation and the first oscillation and / or the second oscillation. Thus, using the third oscillation axis or the third oscillation, even more complex projection images can be formed, in particular, in which, for example, the intensity or phase of the deflected radiation can be (additionally) modulated by movement around the third oscillation axis, for example, by a corresponding non-uniform design of the reflectivity of the reflective surface or the structure.

[0050] According to some embodiments, the control device is further configured to actuate the drive device as a function of at least one detected state variable of the first or second vibration to induce a drive effect on the third vibration by influencing at least one state variable of the third vibration, which counteracts falling below a predetermined minimum frequency distance between the respective instantaneous vibration frequencies of the first and second vibrations on the one hand, or the third vibration on the other hand. Thus, the frequency decoupling of the various axes is extended to the third axis as well, and such coupling can therefore be used to compensate for or avoid undesired imaging disturbances that would otherwise occur during projection.

[0051] In some embodiments, the microscanner further comprises an encapsulation body by means of which at least the deflection element and the spring device are hermetically encapsulated, whereby the deflection element in the encapsulation body can perform oscillations and is oscillatably suspended on the spring device. The encapsulation body has an encapsulation section bridging the deflection element, through which the radiation to be deflected can be emitted into the spatial region encapsulated by the encapsulation body and emitted again therefrom after being deflected at the deflection element. The encapsulation body or capsule section can in particular be made of a glass material or one that is at least mainly, preferably mostly, transparent to electromagnetic radiation in the spectral range relevant to the use of the microscanner.

[0052] The use of such an encapsulation allows, in particular, a reduction in the pressure in the sealed, encapsulated spatial region, in order to reduce or even substantially eliminate gas friction losses, in particular air friction losses, or other disturbances to the vibration of the deflecting element, and in particular to evacuate this spatial region. This is particularly advantageous when using a microscanner for Lissajous display applications, when the deflecting element and its spring suspension do not operate in ambient air, but in reduced pressure, in particular in a vacuum, since friction losses due to air damping are in this way very efficiently avoided, with the result that the microscanner can achieve vibration amplitudes, for example, up to 100 times higher than in air at atmospheric pressure. The achievable optical resolution can therefore also be correspondingly increased, for example by up to 100 times, in one or each of the first and second vibration axes.

[0053] In some of these embodiments, the capsule section has a dome-shaped (cupola-shaped), flat, or right-angled U-shaped cross section. The dome-shaped cross section has the particular advantage that the incident and outgoing electromagnetic beams, especially laser beams, are hardly deflected by the wiring. To the extent that the incident beam is reflected on the dome-shaped capsule section, this usually occurs in a direction different from the direction of the outgoing beam reflected by the deflection element, thus effectively avoiding undesired interactions or beam overlap. On the other hand, the flat and right-angled U-shaped cross section are distinguished in each case by particularly simple production and handling during the manufacture of the microscanner. The right-angled U-shaped cross section can also offer the advantage that any intermediate layers (spacer layers) that would otherwise be required in the encapsulation substructure to form a spatial region enclosed by the encapsulation large enough for the deflection element to move can be avoided or reduced in number or thickness.

[0054] A second aspect of the invention relates to a projection system for projecting a Lissajous figure onto an observation field, the projection system including a microscanner according to the first aspect of the invention, in particular according to one of the embodiments and variants thereof described herein.

[0055] According to some embodiments, the projection system may comprise, inter alia, a radiation source for generating an electromagnetic beam that is to be deflected by (and thus "incident on") the microscanner.

[0056] According to some embodiments, the control device is further configured to supply at least one modulation signal to the radiation source, so that the incident electromagnetic beam can be modulated accordingly. The modulation may in particular relate to its temporal or spatial intensity profile. However, depending on the type of radiation source, other types of modulation are also conceivable, in particular modulation of the wavelength (e.g. color) or wavelength distribution of the radiation emitted by the radiation source. When an image is projected, the modulation is performed accordingly depending on the instantaneous deflection direction, whereby corresponding pixels are generated on the projection surface with the associated pixel values ​​of the corresponding pixels of the image to be displayed by the modulation.

[0057] The features and advantages described in relation to the first aspect of the invention correspondingly apply to the above-described projection system according to the second aspect of the invention.

[0058] Further advantages, features and possible applications of the present invention will result from the following more detailed description in conjunction with the drawings.

[0059] The figure is explained below. [Brief explanation of the drawings]

[0060] [Figure 1] 1 is a schematic diagram illustrating an exemplary structure of a microscanner according to some embodiments of the present invention. [Figure 2] 1 is a schematic diagram illustrating an exemplary configuration of a projection system for projecting a Lissajous figure onto an observation field according to some embodiments of the present invention. [Figure 3] 2 is a schematic top view of a deflection unit with a gimbal-less MiniFaros mirror that can be used in particular in the microscanner from FIG. 1; FIG. [Figure 4] FIG. 4 illustrates an exemplary frequency response of the gimbal-less MiniFaros mirror from FIG. 3. [Figure 5]2 is a schematic top view of an exemplary further gimbal-less mirror variation ("KOLA") deflection unit using an arched flexible spring as the spring device, which may be used in particular in the microscanner from FIG. 1; [Figure 6] 6 shows an exemplary recording of a cross section of an uncompensated planar illumination area constricted and deformed with respect to a rectangle in a microscanner with a deflection unit according to FIG. 5; [Figure 7] FIG. 10 is a frequency response diagram illustrating an example of maintaining the required minimum frequency distance during oscillation of a microscanner according to the present invention to avoid self-synchronization as the amplitude increases, thereby causing rigid phase and frequency coupling. [Figure 8(A)] FIG. 2 is a block diagram of an exemplary combined open-loop / closed-loop control (open loop for one axis, closed loop for the other axis) of the microscanner of FIG. 1, according to some embodiments of the present invention. [Figure 8(B)] 8(B) shows exemplary frequency curves for two vibrations as the microscanner from FIG. 8(A) vibrates. [Figure 9] FIG. 2 is a block diagram of an exemplary dual closed-loop control (closed loops for both axes) of the microscanner from FIG. 1, however, signal-based feedback between the two closed-loop controls is only unidirectional, in accordance with an embodiment of the present invention. [Figure 10] FIG. 2 is a block diagram of an exemplary dual closed-loop control (closed loop for both axes) of the microscanner from FIG. 1, in which signal-based bidirectional feedback is provided between the two closed-loop controls, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0061] Throughout the drawings, the same reference characters are used for the same or corresponding elements of the invention.

[0062] FIG. 1 illustrates, in a cross-sectional side view, an exemplary embodiment 100 of a microscanner according to an exemplary embodiment of the present invention having a drive device 105 for driving the microscanner 100 .

[0063] The microscanner 100 includes a piezoelectric actuator 105 as a driving device, which at the same time forms a base plate on which a laminated multilayer structure made of various substrates stacked one on top of the other is arranged, which as a whole forms the deflection unit 101 of the microscanner. The core of this multilayer structure is formed by a first substrate 120 (chip) made of semiconductor material, which is structured into different coherent parts. These parts include a frame part 125, a mirror part ("mirror") 130 used as a deflection element, and a number of spring elements 135 formed as connecting webs, which each connect the mirror part 130 to the frame part.

[0064] The mirror portion 130 is movably mounted within the frame portion 125 via spring elements 135 that can twist so that the mirror portion 130 can perform a two-dimensional, in particular biaxial, oscillatory movement relative to the frame portion 125. The connecting webs 135 thus represent the spring suspension of the mirror portion 130. The connecting webs or spring elements 135 together form the spring device of the deflection unit 101. This spring device is designed to mediate amplitude-dependent mutual coupling between the oscillations on the individual oscillation axes. This results in a non-linear spring characteristic of the spring device as a whole.

[0065] The mirror portion 130 is provided with a metal coating 140 on one of its major surfaces, whereby this metal layer 140 forms a mirrored reflective surface for deflecting incident electromagnetic radiation, in particular, for example, a laser beam in the visible or infrared region of the electromagnetic spectrum. The mirror portion 130 with the coating 140 thus forms the deflecting element of the deflection unit 101.

[0066] The metal layer 140 can include one or more of the following materials: Al, Ti / Au, Ti / Pt / Au, Ta / Pt / Au, Cr / Au, Ta / Au, Ti / Ag, Ta / Ag, Ta / Pt / Ag, Ti / Pt / Ag, Ti / TiW / Au, Ti / W / Au, Ti / W / Ag, Ti / TiW / Ag, among others. In particular, additional dielectric layers can be used above or below the metal layer to improve layer quality or to protect the metal layer from corrosion. In other cases, the mirror layer can be entirely formed from a dielectric layer stack in this way to achieve particularly high reflectivity for a specific wavelength range. The above-mentioned materials can have both high long-term durability and good mirror properties. The shape of the mirrored reflective surface 140 can be circular, particularly as shown in FIGS. 3 and 5, but this is not to be understood as a limitation. In particular, rectangular or other polygonal shapes are also contemplated. Various exemplary implementations of such deflection elements or in particular the first substrate 120 are described in detail below with reference to FIGS.

[0067] Furthermore, the deflection unit 101 optionally comprises a second substrate 145 made of a glass material. The second glass substrate has a cupola shape and is hermetically connected to the frame portion 125 of the first substrate 120 by means of a substrate bonding material 150, for example a glass frit material, to form a first ("upper" in FIG. 1 ) portion 175a of a cavity 175 that has a cupola shape and surrounds the mirror portion 130 on both sides.

[0068] On the side of the first substrate 120 opposite the second substrate 145 in the multilayer substrate 101, a third substrate 110 is arranged, which is a further, fourth substrate 115 designed as a spacer or (equivalent to) spacer layer, used as a base plate between the first and third substrates. The third and fourth substrates may each be made, in particular, of a semiconductor material.

[0069] The fourth substrate 115 is structured to include a cavity that is arranged below the mirror portion 130 so as to form, together with its bottom boundary provided by the base plate 110, a second ("lower" in FIG. 1(a)) portion 175b of the cavity 175.

[0070] Each adjacent individual substrate is connected to one another in a sealed manner, for example again using substrate bonding material 150 or 155, and cavity 175 is designed to be sealed as a whole when second substrate 145 is used. This is preferably evacuated so that there is a residual gas pressure therein, which is preferably significantly below normal conditions (101.325 kPa = 1013.25 mbar), which is preferably 10 kPa / 10 +1 kPa (10 -1 mbar), particularly preferably less than 10 -1 kPa (10 -3 Typically, the first to fourth substrates 110, 115, 120, 145 each have the same basic shape, particularly a rectangular shape, although other shapes are possible.

[0071] The piezoelectric actuator 105 is configured to generate and transmit an oscillatory motion to the deflection unit 101, in particular the mirror portion 130, when electrically actuated. In a variation of this, the oscillatory motion may be multidimensional, with multiple vibrations excited simultaneously about different orthogonal vibration axes when the vibration frequency falls within the resonant range of the respective vibrations. Alternatively, the drive device, in particular the piezoelectric actuator 105 in this example, may be configured such that each of the vibrations is intentionally excitable separately via a corresponding special motion component, in particular via tilting of the actuator about an axis extending parallel to the corresponding vibration axis.

[0072] In this and other ways, the mirror portion 130 can be excited by its mirror surface 140 to perform an oscillatory motion, in particular a resonant motion or a forced multidimensional oscillatory motion, such as a biaxial Lissajous motion with respect to the frame portion 125. Hereinafter, each uniaxial oscillation component around a corresponding one of the oscillation axes will be referred to as an oscillation. In these oscillations, the mirror portion 130 can move out of the plane of the first substrate 120 by tilting (rotating) around the respective axis of oscillation, thereby penetrating the portions 175a and 175b of the cavity 175 on either side. Due to the evacuation of the cavity 175, the remaining friction in the gas is very small, and therefore only slight, in particular negligibly small, damping occurs.

[0073] Additionally, microscanner 100 includes a capacitive positioning device. This positioning device is configured to position the mirror portions 130 of each of the mirror portions 130. current The device comprises two electrodes on which capacitance measurements are performed with the aim of determining the amplitude position, and in particular the orientation. The first of the two electrodes is formed by a metallic mirror surface 140, which is therefore intended to perform a dual function (deflection of incident electromagnetic radiation, electrode). The second of the two electrodes is embodied on the inside of the bottom plate 110, within the cavity region 175, as a corresponding metal coating 180 on the bottom plate 110. In the present example, this bottom electrode 180 is designed as a multi-part metal layer. The shape of this bottom electrode 180 essentially corresponds in type and preferably at least approximately in size to the shape of the mirror part 130, or of its reflective layer or mirror surface 140, lying parallel to it in the undeflected idle state.

[0074] The bottom electrode 180 is connected to one or more so-called vias, i.e., highly electrically conductive (conductivity >10 Ω), that extend from the bottom electrode 180 through the bottom plate 110 to corresponding connection pads 190 on the piezoelectric actuator 105. 6The mirror electrodes 140 are then electrically connected via connection tunnels (S / m) typically filled with a metallic material. The mirror electrodes 140 are then electrically connected via a redistribution layer to connection pads 165 arranged on the first substrate 120 outside the cupola formed by the second (glass) substrate, and from there electrically connected by means of bonding wires 160 to further connection pads 170 on the piezoelectric actuator 105. The mirror electrodes 140 are thus electrically contacted globally via the connection pads 170. As a result, capacitance measurements used to determine the position of the mirror portion 130 can be performed between the connection pads 190 and 170.

[0075] The microscanner 100 also comprises a control device 195, which is configured in particular to control (in the sense of controlling or regulating) the piezoelectric actuator 105 for driving the deflection unit by means of a corresponding electrical control signal 198 such that a respective, in particular resonant, driving effect for at least one of the vibrations of the deflection elements 130, 140 is individually settable. In particular, the control device is configured and in particular programmed to control the piezoelectric actuator 105 as a function of at least one detected state variable of the vibration along a first vibration axis A1 (the "first vibration"), thereby inducing a driving effect of a vibration about a second vibration axis A2 (the "second vibration") orthogonal to the first vibration axis by influencing at least one state variable of the second vibration, which in turn induces an instantaneous vibration frequency f of the first vibration. 1,i and the instantaneous vibration frequency of the second vibration, f 2,i A predetermined minimum frequency distance f between TH In addition, the control device 195 is configured to receive measurement signals 199 from the deflection units based on the above-mentioned capacitance measurements, in particular measurement signals indicating the instantaneous position of the deflection units with respect to the axes A1 and A2. In particular, the amplitude, frequency and phase of the respective vibrations are considered here as state variables.

[0076] Optionally, the control device 195 may be configured to perform an additional control in the opposite direction, i.e., to actuate the piezoelectric actuator 105 as a function of at least one detected state variable of the second vibration, inducing a driving effect of the first vibration by influencing at least one state variable of the first vibration, which may be the instantaneous vibration frequency f of the first vibration. 1,i and the instantaneous vibration frequency of the second vibration, f 2,i and below a predetermined minimum frequency distance between the frequency of the vibration and the frequency of the vibration. Details of open-loop and closed-loop control of vibration that can be performed in this situation using control device 195 are described below, with particular reference to Figures 7 to 10.

[0077] FIG. 2 shows a schematic diagram of an exemplary structure of a projection system 200 for projecting a Lissajous figure onto an observation field 220. In particular, the microscanner 100 from FIG. 1 can be used for this purpose. Using a laser 210 used as an electromagnetic radiation source, in particular a source of visible light, an incident light beam L1 is generated on a mirrored surface 140 used as a reflective surface, which is directed onto the reflective surface 140 and reflected there, where it is imaged as a detected beam L2 onto the observation field 220, illuminating it at least in sections. The observation field can be defined by a projection surface, for example, a projection screen or a smooth surface such as a floor or road surface. In addition to the simplest case of pure reflection shown in FIG. 2, in addition to the deflection elements or mirrors 130 / 140, one or more further optical elements, in particular in the form of mirrors or optical lenses, can be provided to define the image.

[0078] Figure 3 shows a schematic top view of a deflection unit 300 with a gimbal-less MiniFaros mirror, which may be used in particular in the microscanner 100 from Figure 1 or in the projection system 200 from Figure 2. Figure 4 shows the associated frequency response of the deflection element amplitude after excitation about the oscillation axis of interest.

[0079] In this particular embodiment, the microscanner can be specifically designed as a two-axis microscanner 300. Its deflection unit 101 includes deflection elements 130, 140, here designed as mirror plates. These are suspended from the surrounding frame section 125 of the substrate 120 and are supported by three rotationally symmetrically arranged spring elements 135, which together form a spring device. The suspensions are suspended in a gimbal-less manner on the frame section 125 so that the deflection elements 130, 140 (mirrors) can simultaneously perform a first rotational oscillation about a first oscillation axis A1 and a second rotational oscillation about a second oscillation axis A2 orthogonal to the first oscillation axis A1 and orthogonal to the first oscillation axis A2. During the simultaneous oscillations, the deflection elements deflect an electromagnetic beam L1 incident on the deflection elements, thereby generating a nonlinear Lissajous projection in the observation field 220. The course of the two mutually orthogonal oscillation axes A1 and A2 depends on the course of excitation due to the rotational symmetry of the three suspensions, each spaced 120 degrees apart along the mirror circumference.

[0080] Due to the special configuration of the spring device, the vibrations about the two axes A1 and A2 are now strongly coupled and therefore no longer independent. Indeed, in this case, unlike a harmonic oscillator, the effective spring stiffnesses k1 and k2 are proportional to the actual mechanical amplitudes (deflections) θ about the two vibration axes A1 and A2, respectively. 1,i (t) and θ 2,i is a time-dependent function of (t) as follows: k1=k1(θ 1,i (t),θ 2,i (t)) and k2 = k2(θ 1,i (t),θ 2,i (t)) (3)

[0081] In the case of the MiniFaros mirror type, the coupling or interaction between the two vibrations is usually very clearly visible. Both vibration axes are defined by all three springs 135. This means that all three springs 135 are involved in both the A1 and A2 axes, in contrast to a gimbaled mirror, in which each vibration axis has its own pair of torsion suspensions.

[0082] When a MiniFaros mirror is driven conventionally, i.e., by internal or external forces without the special control of the present invention, it first begins to oscillate linearly about axis A1 or A2. Then, as frequency f increases and approaches the resonant frequency of the second axis, the vibrational energy increasingly shifts from the first vibration about axis A1 to the second vibration about axis A2, and mirror 130 / 140 no longer oscillates solely linearly but oscillates elliptically. This ellipse gradually increases in diameter, while simultaneously becoming increasingly circular. This means that the vibrational energy provided by the strong interaction between the two axes is increasingly transferred from one axis to the other.

[0083] The second axis will self-synchronize in terms of phase position because then whatever the phase relationship between the axes there will be no vibration, there will be an ellipse or a circle, which is equivalent to a synchronized phase position of the two axes A1 and A2, but the energy was supplied through only one axis.

[0084] An interesting and important feature of strongly interacting axes is the nonlinearly behaving spring suspension 135. This results in pronounced nonlinear resonances, which in the case of the MiniFaros mirror are so-called "stress stiffening" or "spring stiffening" problems with a "sloping pointed cap" towards higher frequencies, as shown for example in Figure 4 as the frequency response of the vibration amplitude for axis A1.

[0085] The spring stiffnesses k1 and k2 according to equation (3) above now increase as a function of the first amplitude θ1 and as a function of the second amplitude θ2, as the respective amplitudes increase. The result, therefore, is that the microscanner 100 can now only be resonated from a lower frequency to a higher frequency to achieve the maximum amplitude, which occurs at resonance. Additionally, one must start from the lower of the two resonant frequencies to excite vibrations about both axes A1 and A2. If one starts from the higher of the two resonant frequencies, the vibration remains uniaxial.

[0086] 4 shows a family of corresponding frequency responses for three different actuation voltages at levels of 40V, 80V, and 120V for the drive device 105, with higher actuation voltages corresponding to larger maximum amplitudes in otherwise identical operating modes. When oscillating at higher frequency curves ("up"), the peak-shaped amplitude curves described above result in a greater amplitude of the synchronized axis (f 1,i ~~f 2,i or f 1R ~~f 2R ~~f R ), which clearly leads to only one significant maximum.

[0087] Instead of a nearly vertical and narrow resonance peak, there is a clear broadening of the resonance curve towards higher frequencies during vibration as the vibration amplitude increases. The higher the vibration amplitude, the stiffer the suspension, i.e. the larger the spring stiffness k, and the higher the resonance frequency f R changes more strongly, which increases the bandwidth (frequency tuning range).

[0088] If instead the vibration were performed at a lower (“down”) excitation frequency, a significantly different frequency response would result, with the resonant frequency f of the two axes A1 and A2 now remaining separated. 1R and f 2R A separate, less pronounced maximum for .times. ...

[0089] Nonlinear 2D microscanners without gimbals almost always have very strong coupling. Strong nonlinear resonances result in a large tuning range, i.e., a wide bandwidth over which the microscanner can resonate. Depending on the embodiment, this can be 200 Hz for a MiniFaros mirror, which is very high, for example, relative to the sub-1 Hz bandwidths that are typical for high-quality gimbal scanners.

[0090] These nonlinearly coupled 2D mirrors are no longer a combination of two harmonic oscillators, since there is no longer a spring force that increases linearly with amplitude based on the "spring constant" according to equation (3), i.e., there is no harmonic behavior. Rather, it is a spring force that has a strong nonlinear dependence on amplitude, and can be described as a so-called "Duffing oscillator."

[0091] Note that MiniFaros mirrors do not usually have the same resonant frequency, even though the resulting Lissajous figure may be a circular path / elliptical shape, but may have two different resonant frequencies, which may be about 100 Hz apart in the ground state (low vibration amplitude). However, when the axis with the lower resonant frequency vibrates, the oscillator will damp towards the higher frequency, so that the frequencies of the two axes eventually overlap (f 1R ~~f 2R ), making the energy exchange completely possible. Therefore, the deflection unit 300 is not easily suited in practice to planar illumination of the field of view by using Lissajous projections that go beyond the imaging of ellipses, especially circular lines, instead of the desired planar illumination.

[0092] On the other hand, when the control device according to the invention is used to control the drive device of the microscanner 100, wide, in particular also at least approximately rectangular, illuminations can be achieved by tuning the amplitude. The frequency maxima for the two oscillations or axes can be maintained even when oscillating at high frequencies, provided that these frequencies are separated by a predetermined minimum frequency distance f.TH , which would result in illumination that deviates from the elliptical shape.

[0093] 5 is a schematic top view of deflection unit 101, in particular deflection unit 500 with a gimbal-less mirror (here designated as type "KOLA") according to another embodiment of substrate 120. This embodiment may again be used in particular in microscanner 100 from FIG. 1 or projection system 200 from FIG. 2.

[0094] The KOLA microscanner is a two-axis gimbal-less microscanner. The deflection unit 500 includes deflection elements (mirrors) 130, 140, suspended on two opposite sides by flexible springs 135a, 135b firmly clamped onto a (rigid) frame section 125, specifically the tip. The flexible springs 135a, 135b each have two arcuate sections that are connected to each other at their ends and otherwise extend adjacent and spaced apart from each other, extending around the deflection elements 130, 140. The respective sections of each flexible spring adjacent to the deflection elements 130, 140 are connected to the deflection elements 130, 140 by inner connecting webs 136a, 136b. The respective sections of each flexible spring 135a, 135b adjacent to the frame section 125 are connected to the frame section 125 by outer connecting webs 137a, 137b.

[0095] The length of the flexible springs 135a, 135b may be designed to extend as far and wide as possible along the outer contour of the biasing element, preferably perpendicularly away from the oscillation axis A1 of rotation (approximately a quarter circle to each side) and then back again to this axis A1. This course of the flexible springs allows the biasing elements 130, 140 to be movable in both mutually orthogonal oscillation axes A1 and A2, the respective bearings of which are defined by the structure of the suspension spring device described.

[0096] The two axes or associated vibrations exhibit strong coupling and thus significant interaction when the vibration amplitude is very large. In particular, each vibration amplitude of the deflection element 130, 140 about the first axis A1 immediately results in a stiffening of the entire flexible spring 135a or 125b, which affects both vibration axes A1 and A2. As a result, not only is the associated spring constant or amplitude-dependent spring function k1 periodically detuned for the vibration of the first axis A1, but simultaneously the associated spring function k2 for the second axis A2 perpendicular thereto is also detuned, and vice versa. Therefore, both spring functions are time-dependent functions according to Equation (3).

[0097] This periodic stiffening results in the resonant frequencies f 1R and f 2R is periodically shifted to the axes A1 and A2. This means that the vibration of the first axis A1 is periodically shifted to the resonant frequency f 2R is periodically detuned, and the vibration of the second axis A2 is conversely detuned to the resonance frequency f of the first axis A1. 1R In addition, the two axes A1 and A2 permanently transmit, exchange and store vibration energy with each other.

[0098] In the KOLA microscanner, this results in modulated mirror vibration amplitudes θ(t) and θ(t). If no controller according to the invention is used, the resulting scan pattern here upon projection into the observation field 220 will therefore not have a perfectly rectangular cross-section, but rather will exhibit a clear constriction, particularly in one axis. This is illustrated diagrammatically in FIG. 6.

[0099] On the other hand, if the control device according to the invention is used to control the drive device of the microscanner 100, wide, in particular also of at least approximately rectangular shape, illumination can be achieved by tuning the amplitude. Then, the frequency maximum for the two oscillations or axes can also be maintained when oscillating at high frequencies, since these frequencies are separated by their frequency distance f1,i -f 2,i or |f 1,i -f 2,i |, which are always set with respect to a given minimum frequency distance f TH Because it does not fall below .

[0100] FIG. 7 is a frequency response diagram illustrating an example of maintaining the required minimum frequency distance during oscillation of a microscanner according to the present invention to avoid self-synchronization as the amplitude increases, thereby causing rigid phase and frequency coupling.

[0101] The three lower curve profiles show the actual frequency response of the vibration amplitude of the deflecting element (for either one of the two axes) at different successive times t1, t2, and t3 of the vibration process. The top curve, shown as a dashed line in Figure 7, represents the situation when the amplitude of the oscillator with the lower resonant frequency becomes large enough that the resonance of one axis is superimposed on the resonance of the other axis (with the higher resonant frequency). In this situation, the first oscillator attempts to synchronize with the second oscillator. This "merging" can only be prevented if the two resonators maintain their separation by both vibrating simultaneously and thereby exhibiting stress stiffening in the same direction. f1(f 1R ) specifies the instantaneous (amplitude dependent) resonant frequency for the first vibration axis A1, and therefore f2 (f 2R ) specify the respective instantaneous (amplitude-dependent) resonant frequencies for the second oscillation axis A2. When using the microscanner according to the invention, on the one hand, a strong coupling between the various oscillation or associated oscillation axes A1 and A2 occurs due to the gimbal-less deflection unit used. However, on the other hand, the control unit 195 determines the minimum frequency distance f TH maintains two resonant frequencies f1 and f2 (or f 1R and f 2R ) to prevent the fusion of these oscillations or short oscillation axes. As a result, the resulting Lissajous figure also 1R =f2R ), rather than representing a simple ellipse, by appropriate selection of excitation by the drive unit 105, differently shaped, planar, and even in particular rectangular, illumination areas can be induced in the observation field 220.

[0102] FIG. 8(A) shows a block diagram of an exemplary embodiment 800 of the microscanner from FIG. 1 with combined open-loop / closed-loop control (open-loop for one axis and closed-loop for the other axis).

[0103] The control device 195 has, on the one hand, an open-loop control unit 196 (open loop) for a first oscillation about a first axis A1, and, on the other hand, a closed-loop control unit 197 (closed loop) for a second oscillation about a second axis A2. The open-loop controller 196 provides a first actuation signal in the form of a time-dependent voltage V1(t) to control the piezoelectric actuator 105 for the first oscillation. In contrast, the closed-loop controller 197 provides a second actuation signal (more precisely, a controlled variable signal) in the form of a time-dependent voltage V2(t) to control the piezoelectric actuator 105 for the second oscillation. The two voltages V1(t) and V2(t) correspond to the control signals or controlled variable signals 199 from FIG. 1 or 2. Due to this actuation, the piezoelectric actuator 105 performs a movement acting on the first and second vibration axes A1 and A2 and, by means of its mechanical coupling to the deflection unit 101, applies corresponding mechanical forces F1(t) and F2(t), causing the first and second vibrations, respectively, to resonate in particular, i.e., to have respective instantaneous resonant frequencies f 1R or f 2R Since the deflection unit 101 is a gimbal-less type, there is a non-negligible mechanical coupling K1 (θ 1,i (t);θ 2,i (t)) and K2(θ 1,i (t);θ 2,i (t)), which each have an actual amplitude θ 1,i (t) and θ 2,iIt depends on (t) and is therefore time dependent.

[0104] The control unit 196 includes a controller 196a for the first vibration, which controls a time set point curve θ of the amplitude of the first vibration during vibration of the microscanner 800. 1,s The controller 196a can access a lookup table 196d that stores control data representing the time-dependent voltage V1(t) for controlling the piezoelectric actuator 105 with respect to the first vibration, and outputs the voltage V1(t) to the piezoelectric actuator 105 to operate it.

[0105] While the above-described control of the first oscillation is an open-loop control, the control of the second oscillation is a closed-loop control, using which the instantaneous actual amplitude θ 1,i (t) and θ 2,i The instantaneous position of the deflecting elements (mirrors) 130, 140, given by (t), is fed back as an input signal to the control unit 197. The returned amplitude θ 1,i (t) is sent to the control controller 197a of the control unit 197, which determines the optionally time-dependent minimum frequency distance f TH Considering this, the target value θ for the amplitude of the second vibration 2,s Since the amplitude is interdependent on the frequency of the second vibration, as shown using the example of Figure 7, the instantaneous frequency set point for the second vibration is also determined.

[0106] Set point θ 2,s (t) is sent to a differential detector 197b for the second oscillation, which, in particular, detects the set point θ 2,s (t) and the returned actual value of the amplitude of the second oscillation θ 2,i (t) and the phase difference

number

[0107] 8(B) shows an example frequency curve for two oscillations of the microscanner from FIG. 8(A). This example shows that the first controlled oscillation has its actual frequency f 1,i If is implemented to follow a stepwise course as shown by the continuous characteristic curve, closed-loop control for the second vibration is performed with a minimum frequency distance f TH The vibration of the microscanner can be designed to follow a stepwise course as shown by the dashed characteristic curve, where the coupling K2(θ 1,i (t);θ 2,i By using closed-loop control of the second vibration, which is dependent on the first vibration via (t), the minimum frequency distance f TH Biaxial vibration can be achieved while maintaining

[0108] FIG. 9 is a block diagram of an exemplary dual closed-loop control (closed loops for both axes) of the microscanner from FIG. 1 in accordance with a further embodiment 900 of the present invention; however, the signal-based feedback between the two closed-loop controls is only unidirectional.

[0109] This microscanner scanner 900 is based on the microscanner scanner 800 from Figure 8(A) in that instead of open-loop control for the first oscillation, closed-loop control, in particular closed-loop phase control, is also provided therein. The open-loop control unit is therefore replaced by a closed-loop control unit 196, which controls the actual amplitude θ of the first oscillation. 1,i (t) is also measured at the deflection element and fed back to the closed loop control unit 196, further closing the control loop for the first oscillation.

[0110] As a result, there is now a separate closed-loop control for each of the two vibrations, and the closed-loop control for the first vibration does not take into account the closed-loop control of the second vibration, and therefore the returned actual amplitude θ of the second vibration. 2,i In contrast, the closed-loop control for the second vibration acts as a slave closed-loop control, and its setpoint determination depends on the returned actual amplitude θ of the first vibration. 1,i (t) and the minimum frequency difference f TH Ensuring that a minimum frequency distance is maintained therefore depends on the closed-loop control of the second oscillation, but each of the two closed-loop controls also ensures that the respective drive signals V1(t) and V2(t) each act in phase with the actual course of the respective oscillation and thus support the corresponding resonant operation of the deflection unit 101.

[0111] FIG. 10 is a block diagram of an exemplary dual closed-loop control (closed loop for both axes) of the microscanner from FIG. 1 in accordance with yet another embodiment of the present invention 1000, but with signal-based bidirectional feedback between the two closed-loop controls.

[0112] The microscanner 1000 has a closed loop control for the first oscillation and also controls the actual amplitude θ of the second oscillation. 2,i (t) and the minimum frequency distance f TH as an input signal. This results in a symmetrical structure in which the closed-loop control for the first vibration is influenced by the second vibration and vice versa. Ensuring that a minimum frequency distance is maintained therefore relies on the closed-loop control for both vibrations, but each of the two closed-loop controls also ensures that the respective drive signals V1(t) and V2(t) each act in phase with the actual course of the respective vibration, thus supporting the corresponding resonant operation of the deflection unit 101.

[0113] In this case, the respective closed loop controls for the first and second vibrations are each rate of change and the control speed of each other closed loop control rate of change and is designed to be dynamically configured or configurable as a function of the control speed. This tuning is advantageous in that it allows the axle to vibrate at approximately the same speed and therefore the original resonant frequency of the axle to be shifted towards higher frequencies at approximately the same speed, especially as spring stiffness increases with increasing amplitude.

[0114] To reduce or ideally completely eliminate the risk of control instability from the start, the maximum rate at which frequency or amplitude in particular can be changed can be limited within the control loop, possibly even as part of the calibration that results from the calibration process. Since frequencies are typically very high, e.g., several kilohertz, very well-controlled and safe procedures can be performed for this purpose within very short periods of time.

[0115] While at least one exemplary embodiment has been described above, it should be noted that numerous variations exist. It should also be noted that the exemplary embodiments described represent non-limiting examples only and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description provides guidance to those skilled in the art for implementing at least one exemplary embodiment, and it should be apparent that various changes in the operation and arrangement of elements described in the exemplary embodiments may be made without departing from the scope of the subject matter defined in the appended claims and their legal equivalents. [Explanation of symbols]

[0116] 100 Micro Scanner 101 Deflection Unit 105 Actuation devices, especially piezoelectric actuators 110 Third substrate, bottom plate 115 fourth substrate, spacer layer 120 first substrate 125 Frame part 130 Mirror part 135 Spring Elements 135a,b Flexible spring 136a,b Inner connecting web 137a,b Outer connecting web 140 Metal mirror coating, mirror electrode 145 Second substrate, cupola shape 150 Substrate bonding materials 155 Further Substrate Bonding Materials 160 bond wire 165 connection pads on the first substrate 120 for connecting the upper electrode (top electrode) 140 170 Connection pad on piezoelectric actuator 105 for connecting upper electrode 140 175a Upper region of cavity 175 175b Lower region of cavity 175 180 Structured, possibly multi-part bottom electrode 185 vias with solder bumps for contacting the piezoelectric actuator 190 connection pad on piezoelectric actuator 105 for connecting bottom electrode 195 Control Devices 196 Open loop control unit or closed loop control unit for first vibration 196a First vibration controller 196b Differential detector for first vibration 196c First, a closed loop controller or loop filter (in a phase-locked loop) for the first oscillation 196d Lookup Table 197 Closed Loop Control Unit for Second Vibration 197a Second vibration controller 197b Differential detector for second vibration 197c Closed-loop controller or loop filter for second oscillation (in a phase-locked loop) 198 Measurement signals for feedback in control loops and position measurement 199 Control Signal or Controlled Variable Signal 200 Projection System 210 Light sources, especially lasers 220 Observation field, especially projection surface 300 Deflection unit with gimbal-less MiniFaros mirror 400 Frequency response of the gimbal-less MiniFaros mirror 500 Deflection unit with gimbal-less KOLA mirror 600 Narrowed and deformed planar illumination area 700 Frequency Response 800 Block diagram of mixed open-loop control (open loop) / closed-loop control (closed loop) 900 Block diagram of one-way coupling two-axis control (closed loop) 1000 Block diagram of two-way coupling control (closed loop) A1 First vibration axis A2 Second vibration axis Axis-specific driving forces from F1 and F2 drive devices to the deflection elements K1(...) Machine axis coupled to the first axis K2(...) Machine axis to be coupled to the second axis L1 incident light beam Light beam reflected at mirror L2 V1, V2 Control voltage for operating the drive device f frequency f1 First vibration setpoint frequency f2 Second vibration setpoint frequency Δf Frequency difference f TH Minimum Frequency Distance θ 1,i Actual amplitude of the first vibration on the first vibration axis A1 θ 1,s Setpoint amplitude of the first vibration on the first vibration axis A1 θ2,i Actual amplitude of the second vibration on the first vibration axis A2 θ 2,s Setpoint amplitude of the second vibration on the first vibration axis A2 Δθ Amplitude difference

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Claims

1. A microscanner (100) for a projection system (200) for projecting a Lissajous figure onto an observation field, the microscanner (100) comprising: The incident electromagnetic beam (L １ a deflection unit (101) having deflection elements (130, 140) for deflecting a first axis of vibration (A) with respect to the support structure (125) in a gimbal-less manner by using the spring devices (135, 135a, 135b) on the support structure (125). １ ) and a second axis of vibration (A ２ ) and a second rotational oscillation about the deflection element (130, 140) to deflect the electromagnetic beam (L) incident on the deflection element (130, 140) during the simultaneous oscillation. １ a deflection unit (101) suspended so as to be able to deflect the beam (102) and thereby induce a nonlinear Lissajous projection in the observation field (220); a respective driving effect (F) for at least one of the first and second rotational oscillations of the deflection element (130, 140) １ , F ２ a control device (195) configured to operate a driving device (105) for driving the deflection unit (101) such that the respective deflection angles (f) and (g) are individually configurable; Equipped with The spring devices (135, 135a, 135b) provide an amplitude dependent mutual coupling (K １ , K. ２ ) further engineered to mediate The control device (195) also controls at least one detected state variable of the first rotational oscillation. [Equation 1] to operate the drive device (105) as a function of at least one state variable of the second rotational oscillation. [Equation 2] a driving effect (F) as a function of at least one detected state variable on the second rotational vibration by influencing ２ ), thereby inducing the driving effect (F ２ ) is the instantaneous vibration frequency (f １，ｉ , f ２，ｉ ) between the predetermined minimum frequency distance (f ＴＨ ) below the microscanner (100).

2. The control device (195) controls at least one detected state variable of the second rotational oscillation. [Equation 3] to operate the drive device (105) as a function of at least one state variable of the first rotational oscillation. [Equation 4] The driving effect (F １ ), which is configured to induce the instantaneous vibration frequency (f １，ｉ , f ２，ｉ ) a predetermined minimum frequency distance (f ＴＨ 2. The microscanner (100) of claim 1, wherein the microscanner (100) counteracts a drop below 0.05 mm.

3. The control device (195) controls the state variable of the second rotational vibration. [Equation 5] and actuating the drive device (105) independently of the at least one state variable of the first rotational oscillation. [Equation 6] 2. The microscanner (100) of claim 1, configured to induce a driving effect in the first rotational oscillation by affecting a

4. Each of the at least one state variables of each vibration has its amplitude (θ １，ｉ ;θ ２，ｉ ), frequency (f １，ｉ , f ２，ｉ ), or phase [Equation 7] 2. The microscanner (100) of claim 1, wherein the temperature is determined by, or as a function of at least one of these variables.

5. The control device (195) operates the drive device (105) to control the state variables of each other vibration. [Equation 8] 2. The microscanner (100) of claim 1, configured to induce each of said driving effects on at least one vibration driven thereby in a closed-loop control sense as a function of at least one repeatedly detected controlled variable that is, or is defined as a function thereof.

6. The controlled variables for the drive control of each driven rotational vibration are the frequency (f １，ｉ ;f ２，ｉ ) or phase [Equation 9] or as a function of at least one of these state variables, the detection of this controlled variable is performed by detecting the same amplitude (θ １，ｉ ;θ ２，ｉ 6. The microscanner (100) of claim 5, wherein the scanning is always performed in a scanning mode.

7. The control device (195) controls the state variables (θ １，ｉ ;θ ２，ｉ ), configured to implement both the first rotational oscillation and the second rotational oscillation in a closed-loop control sense as a function of at least one repeatedly sensed controlled variable which is, or is defined as, a function of 6. The microscanner (100) of claim 5, wherein each of said closed loop controls for said first and second rotational oscillations is designed to be dynamically configurable with respect to the rate of change and control speed of each closed loop control as a function of the rate of change and control speed of each other closed loop control.

8. The control device (195) controls the at least one detected state variable (θ １，ｉ ;θ ２，ｉ ) for each of the vibrations driven thereby in an open-loop control sense as a function of the respective driving effect (F １ , F ２ 2. The microscanner (100) of claim 1, configured to actuate the drive device (105) to induce a

9. The control device (195) controls the amplitude (θ) of the alternating oscillations of the drive device (105) for the first rotational oscillation and the second rotational oscillation. １，ｉ ;θ ２，ｉ 9. The microscanner (100) of claim 8, configured to control the driving device (105) to induce a respective driving effect on each of the vibrations driven thereby to achieve a step-by-step increase in frequency, respectively.

10. The control device (195) controls the frequency of at least one of the vibrations to be equal to or greater than the current resonant frequency (f １Ｒ , f ２Ｒ 2. The microscanner (100) of claim 1, further configured to operate the drive device (105) so as to maintain the drive device (105) within a predetermined limited resonance range surrounding the microscanner (100).

11. The limit of the resonance range for the resonance frequency is the frequency value f Ｒ The value of f Ｒ The microscanner (100) of claim 10, wherein the microscanner (100) is defined by ±70%.

12. The minimum frequency distance (f ＴＨ 2. The microscanner (100) of claim 1, wherein the first and second electrodes are fixed to a constant size.

13. The minimum frequency distance (f ＴＨ (t)) is the current amplitude (θ １，ｉ ;θ ２，ｉ ) respectively, or the current amplitudes of these two oscillations (θ １，ｉ ;θ ２，ｉ 2. The microscanner (100) of claim 1, wherein the dimensions are defined as variable dimensions that depend on each other.

14. The spring devices (135, 135a, 135b) adjust the amplitude dependent mutual coupling (K １ , K. ２ ) is greater than the amplitude (θ １，ｉ ;θ ２，ｉ 2. The microscanner (100) of claim 1, wherein the microscanner (100) is designed to increase steadily with increasing .mu.m.

15. 2. The microscanner (100) of claim 1, wherein the microscanner (100) is designed as a two-axis microscanner, and the deflection unit (101) comprises deflection elements (130, 140) suspended on a frame (125) that uses three rotationally symmetrically arranged spring elements (135) as a support frame and surrounds it.

16. Designed as a two-axis gimbal-less microscanner (100), said deflection unit (101) comprises deflection elements (130, 140) suspended, in each case firmly clamped on two opposite sides by means of flexible springs (135a, 135b), on a frame (125) used as a support frame, 2. The microscanner (100) of claim 1, wherein the flexible springs (135a, 135b) each have two curved sections that are connected to each other at their end faces and otherwise extend adjacent to each other at a distance from each other and that extend around the deflection element (130, 140), the section of each flexible spring (135a, 135b) adjacent to the deflection element (130, 140) being connected to the deflection element (130, 140), and the section of each flexible spring (135a, 135b) adjacent to the frame (125) being connected to the frame (125).

17. 2. The microscanner (100) of claim 1, wherein the control device (195) is configured to set the first rotational oscillation, the second rotational oscillation, or at least one corresponding state variable of each of these two oscillations individually to a specific set point value in a situation where the control device (195) operates the drive device (105) to drive the deflection unit (101) in an amplitude adjustment, frequency adjustment, or phase adjustment sense.

18. The deflection elements (130, 140) are suspended in a gimbal-less manner on the support structure (125) by means of the spring devices (135, 135a, 135b) so as to be able to simultaneously additionally perform a third rotational oscillation with respect to the support structure (125) about a third axis, which is orthogonal in each case to the first and second axes, whereby the deflection elements (130, 140) are able to deflect an electromagnetic beam (L) incident on the deflection elements (130, 140) during the simultaneous oscillation of the first, second and third rotational oscillations. １ 2. The microscanner (100) of claim 1, wherein the spring devices (135, 135a, 135b) are further designed to mediate amplitude-dependent mutual coupling between the third rotational oscillation and the first rotational oscillation, the second rotational oscillation, or both, thereby generating a nonlinear Lissajous projection in the observation field (220).

19. The control device (195) controls at least one detected state variable (θ １，ｉ ;θ ２，ｉ ) to induce a driving effect on the third rotational vibration by influencing at least one state variable of the third rotational vibration, which is a function of the instantaneous vibration frequency (f １，ｉ ;f ２，ｉ ) a predetermined minimum frequency distance (f ＴＨ 20. The microscanner (100) of claim 18, wherein the microscanner (100) is adapted to counteract the above-mentioned.

20. further comprising an encapsulation body by means of which at least the biasing elements (130, 140) and the spring devices (135, 135a, 135b) are hermetically encapsulated, whereby the biasing elements (130, 140) within the encapsulation body can perform oscillations and are suspended so as to be able to oscillate on the spring devices; 2. The microscanner (100) of claim 1, wherein the encapsulation body has an encapsulation section (145) bridging the deflection elements (130, 140), through which the radiation to be deflected can be emitted into the spatial region encapsulated by the encapsulation body and re-emitted therefrom after being deflected at the deflection elements (130, 140).

21. 21. The microscanner (100) of claim 20, wherein the encapsulation section (145) has a dome-shaped, planar, or right-angled U-shaped cross-section.

22. A projection system (200) for projecting a Lissajous figure onto an observation field (220), said projection system (200) comprising a microscanner (100) according to any one of claims 1 to 21.

23. The control device is further configured to provide at least one modulation signal to the radiation source, and in response to the signal, modulate the incident electromagnetic beam (L １ 23. The projection system (200) of claim 22, wherein the light source (100) is modulated.

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