Microscanner having a projection system and coupled oscillator for projecting a lissajous figure - Patents.com

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 called in particular in technical terms "MEMS scanners", "MEMS mirrors" or "micromirrors" and in English in particular "microscanners", "microscanning mirrors" or "MEMS mirrors", from the class of micromirror actuators for the dynamic modulation of electromagnetic radiation, in particular visible light, Microelectromechanical Systems (MEMS), more precisely Micro-Optoelectromechanical Systems (MOEMS). Depending on the design, the modulation movement of a single mirror can be a translation or a rotation about at least one axis. In the first case, a phase shift effect is achieved, in the second case, a deflection of the incident electromagnetic radiation is achieved. In the following, microscanners are considered in which the modulation movement of a single mirror is a rotation. In the case of microscanners, the modulation is generated via a single mirror, in contrast to mirror arrays, where the modulation of the incident light is performed via the interaction of several mirrors.

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

[0004] Both in the case of imaging sensors and in the case of display functions, 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, e.g. horizontally and vertically, thereby scanning or illuminating 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 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. This deflection device comprises a deflection unit for generating an oscillation around the deflection axis and an activation device for generating an activation signal for the deflection unit at a first and a second activation frequency, which correspond to a resonance frequency of the deflection unit. The deflection unit has a quality factor of more than 3,000. The activation device comprises a first control loop, which is designed to control the first and / or second activation frequency depending on a measured phase position of the oscillation of the deflection unit such that the maximum amplitude of the oscillation remains within the resonance range of the deflection unit, the activation frequencies not having a fixed integer ratio. The activation device further comprises a second control loop, which is designed to influence the resonance frequency of the first and / or second deflection axis 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 a Cardan suspension (gimbals), so that the associated vibrations about the two axes are completely decoupled from each other and are phase controlled completely independently of each other with the aim of keeping each of the two axes in resonance.

[0006] For the deflection device from EP 2514211 B1 the following relations apply: f 1R ≠f 2R , (1) where f 1R is 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 a 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 such a type of microscanner, illustrated in FIG. 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 the 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 approximate one another as they oscillate, resulting in only essentially elliptical (and therefore linear, non-planar) Lissajous illumination of the viewing field. In particular, at least approximately planar, and especially at least approximately rectangular, illumination of the viewing field therefore becomes 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, using which planar Lissajous illumination of an observation field is possible. 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 subject matter of the dependent claims.

[0014] A first aspect of the invention relates to a microscanner for a projection system for projecting a Lissajous figure onto an observation field. The microscanner comprises a deflection unit having (i) a deflection element for deflecting an incident electromagnetic beam, in particular by means of reflection, (ii) a support structure, and (iii) a spring device. The spring device can comprise one or more spring elements. The deflection element is suspended in a gimbal-less manner by means of the spring device on the support structure such that the deflection element simultaneously performs 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 causes a nonlinear Lissajous projection in the observation field by deflecting an electromagnetic beam incident on the deflection element during the simultaneous oscillation.

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

[0016] Furthermore, the spring device is designed to mediate an 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 and second vibrations, respectively.

[0018] "Lissajous projection" in the sense of the present invention should in particular be understood as the 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 which deflects the radiation into the observation field.

[0019] A "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, which is 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 at least a first oscillation does not represent a linear oscillation, i.e. does not follow Hooke's law with an amplitude-independent oscillation spring constant.

[0020] An "axis" or the 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 "driving 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 vibration of the deflection element with respect to the support structure and with respect to at least a first and a second, possibly a third, vibration axis.

[0022] As sometimes used herein, the words "comprising," "including," "involving," "including," "having," "having," or any other variations 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 that are inherent to such method or device.

[0023] Further, 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] The words "a" or "an" as used herein are defined as meaning "a / one or more" in the English language and "one or more" in the Japanese language. The phrases "another" and "further" and any other variations thereof should be understood to mean "at least one other."

[0025] The term "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 achieved that, despite the existing coupling between the various vibrations or vibration axes, the respective vibration frequencies, in particular the resonant frequencies, of the individual vibrations maintain a minimum frequency distance from each other, with no frequency synchronization of these frequencies for the different axes, which, if any, would ultimately result in an elliptical Lissajous figure. This then allows a constant, planar, in particular one, at least essentially rectangular, illumination of the observation field within the framework of the projection, also in particular in the case of gimbal-less mirrors. Among other things, a Lissajous-like excitation of the deflection elements (mirrors) can be achieved by the microscanner, even with many gimbal-less mirrors, even in spite of this situation, when the resonant frequencies of the different axes are close together, which 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 feature than a gimbal-based mirror, a reduction in the required installation space may also be achieved with comparable projection results.

[0029] Since at least one of the oscillators (corresponding to vibration about a particular vibration axis) has non-linear characteristics, i.e. does not correspond to Hooke's Law with an amplitude independent spring constant over its entire amplitude range, a generally wider tuning range (frequency bandwidth) can be achieved, especially with high quality, especially in conjunction 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 and to different degrees.

[0031] Even in the case of microscanners that are strongly coupled axes and therefore explicitly nonlinear, the above-described control can generally enable them to vibrate at different resonant frequencies for the 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 the 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 falling below a predetermined minimum frequency distance between the instantaneous vibration frequencies of the first and second vibrations, respectively. Although the above-mentioned basic form of the microscanner also allows for a "primary-secondary" operation, 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 embodiments described here both the first and second vibrations are affected, in particular in an equal manner, 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 a particularly effective, particularly fast, automatic dynamic control of the vibrations involved can be achieved, while avoiding frequency synchronization of the amplitude-dependent operating frequency, in particular the resonant frequency.

[0034] In contrast to this, according to some alternative embodiments, the control device is configured to actuate the drive device independently of the state variables 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 thus 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 the modulation of each other vibration as a function of the detected amplitude θ of this axis allows the minimum frequency distance to be ensured instantly, in particular in a dynamic manner.

[0036] According to some embodiments, the control device is configured to execute the actuation of the drive device to induce at least one repetitive, in particular continuously, respective actuation 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 or is defined as a function of the state variable of each of the other vibrations. With the help of such closed-loop control, the dynamic actuation of the drive device is achieved in a particularly effective and optimized manner with the aim of ensuring a minimum frequency distance, and in particular also capable of reacting to unforeseen disturbances, which in principle could not be achieved to the same extent with a simple control without feedback. In addition to that, this opens up the possibility of targeted compensation of nonlinear coupling effects, which may otherwise also cause distortions, such as particularly periodic variations of the amplitude-dependent spring stiffness of the spring device with respect to at least one axis, in particular narrowing of the planar area of ​​the observation field illuminated by the microscanner. However, on the other hand, such nonlinear coupling effects may be amplified or deliberately modulated, in particular depending on the application, in order to achieve a particular shape of the illuminated planar area, in particular a shape deviating from an ellipse or a rectangle. In headlight applications, this can be used in particular for static or dynamic shaping of the (flat in cross section) illumination field generated by the headlight system on the basis of 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 within 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 a zero crossing of the amplitude profile of the vibration, 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 may 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 can further be configured to execute both the first and second vibrations in the sense of a closed-loop control, at least one iteration, in particular continuously, as a function of the detected controlled variables, which are state variables of the respective other vibrations or are defined as a function thereof. In this case, these respective closed-loop controls for the first and second vibrations are designed to be dynamically configurable, each in terms of its respective slope and control speed, as a function of the slope and control speed of the respective other closed-loop control. 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 towards higher frequencies at approximately the same speed, in particular when the spring stiffness increases with increasing amplitude (English: "spring stiffening"). Due to the approximate synchronization of the frequency shifts, a 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 that one of the control loops will control significantly faster than the other and thus there will be an undesirable overlap of the resonance ranges, in particular the resonance frequencies of the vibrations, so that the minimum frequency distance is not reached in an undesirable manner, as a result of which only a linear, in particular elliptical, Lissajous projection results depending on the object instead of the desired planar, in particular rectangular, illumination.

[0039] According to some embodiments, the control device is configured to actuate 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 a control technique, a pure "control" of the drive device ("open-loop control") may be used here. Such an open-loop control may advantageously be implemented with less implementation effort compared to the above-mentioned regulation. However, it may in particular also be envisaged to combine such an open-loop control with at least one of the above-mentioned closed-loop controls. In particular, it is also possible that one vibration has an open-loop control and another vibration has a closed-loop control.

[0040] According to some of these control-based embodiments, the control device is configured to control the drive device to induce a respective drive effect for each vibration driven thereby such that the drive device achieves a step-by-step increase in the amplitude or frequency of each of these alternating vibrations with respect to the first and second vibrations. 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 purely open-loop control, in which case there is no undesirable overlap of the resonance ranges, in particular the resonance frequencies of the oscillations, and thus a minimum frequency distance is maintained, so that a purely elliptical Lissajous projection can be avoided instead of the desired planar, in particular rectangular, illumination depending on the object. The sequence of increments may in particular be irretrievably stored in a memory and may in particular have been determined based on a preceding calibration process. In addition to, or as an alternative 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 such that the frequency of each of at least one of the vibrations, in particular the vibration that is primarily driven by said actuation, is within a predefined limited resonant range surrounding the current resonant frequency of said vibration. Typically, the resonant frequency is the frequency f at which the maximum amplitude occurs. R The resonant frequency f is given by R The limit of the resonance range for is, in particular, the frequency value of the resonance frequency f 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 a simple implementation, since once this variable is defined, no kind of dependency needs 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 defined as a variable dimension that depends on the current amplitude of the first or second vibration, respectively, or on the current amplitude of these two vibrations, respectively. In this way, better adaptability to different system conditions is enabled. In particular, the vibration of the microscanner can be controlled more precisely in this way, and also the undesirable overlap of the resonance ranges on different axes can be effectively avoided, when the frequency change of these axes does not proceed at the same speed with the 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 deliberately induced stiffening. The more pronounced this effect is, the more suitable such a biaxial microscanner with a biaxial "spring stiffening" behavior is for unregulated open-loop operation (simply open-loop control), which is very easy to implement. If only one vibration shows 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 possibly not be sufficient for stable open-loop control. This situation is less advantageous than having two oscillator suspensions that show pronounced spring stiffening. If the suspensions are designed such that the vibration with the higher resonant frequency shows "spring stiffening" and the other shows "spring lowering" behavior, it can be ensured that the vibrations do not approach each other and become synchronized with pure open-loop control or even closed-loop control or a combination thereof. If the suspension of the oscillator with the lower resonance frequency is designed with a "spring stiffening" behavior and the suspension with the higher resonance frequency is designed with a "spring lowering" behavior, then 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 a small number of usable properties. If both oscillators exhibit a "spring lowering" behavior, which is relatively difficult to achieve from a design point of view and therefore a rare case, then an advantageously simple implementation based on a pure open-loop control can be achieved, and by extension a correspondingly powerful formula, since the frequency bandwidth of the respective resonances allows sufficient stability of the state. According to the invention, the controller must still be designed in such a way that the desired frequency distance is maintained. This state can be kept stable again by an appropriate control loop.

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

[0047] According to some alternative embodiments, the microscanner is designed as a two-axis gimbal-less microscanner, in which (i) the deflection unit comprises a deflection element that is firmly clamped and suspended on two opposite sides by means of a flexible spring on a rigid frame used as a support frame, in particular a chip frame made of a semiconductor material, and (ii) the flexible springs each have two arched sections that are connected to each other at their end faces and otherwise extend spaced apart from each other and extend around the deflection element, with the respective section of each flexible spring adjacent to the deflection element being connected to the deflection element and the respective section of each flexible spring adjacent to the frame being connected to the frame. The deflection elements and the flexible springs, as well as optionally the frame, may in particular be integrally formed, i.e. manufactured from a single substrate. In such a microscanner, the respective spring stiffness for each of the axes depends both on the instantaneous amplitude of the deflection element with respect to itself and on the instantaneous amplitude of the deflection element with respect to 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 vibration energy, temporarily storing energy in between. With such a mirror, in particular a planar illumination of the observation field having a deformed, in particular a narrowed rectangular shape, may be achieved, and by appropriately operating the drive device to compensate for the intermodulation, also an at least approximately rectangular planar illumination may 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 set point value in the context of actuating the drive device for driving 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 an operational-based, partial or complete, compensation of intermodulation of the various vibrations and for maintaining a 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 using a spring device so that a third rotational oscillation can be simultaneously additionally performed with respect to the support structure about a third oscillation axis, orthogonal in each case 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 an amplitude-dependent mutual coupling between the third oscillation and the first oscillation or the second oscillation or both. Thus, using the third oscillation axis or the third oscillation, in particular even more complex projection images can be formed, in which for example the intensity or phase of the deflected radiation can be (additionally) modulated by a movement around the third oscillation axis, for example by a corresponding non-uniform design of the reflectivity or structure of the reflecting surface.

[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 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 also extended to the third axis, such that such coupling can be used to compensate or avoid undesired imaging disturbances that would otherwise occur during projection.

[0051] In some embodiments, the microscanner further comprises an encapsulation, by means of which at least the deflection element and the spring device are encapsulated in a hermetically sealed manner, whereby the deflection element in the encapsulation can perform oscillations and is suspended so as to be able to oscillate on the spring device. The encapsulation 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 and emitted again therefrom after being deflected at the deflection element. The encapsulation or capsule section can in particular comprise a glass material or one that is at least mainly, preferably largely, transparent to electromagnetic radiation in the spectral range relevant for the use of the microscanner.

[0052] The use of such an encapsulation makes it possible in particular to reduce the pressure in the sealed and encapsulated spatial region, in particular to evacuate the gas from this spatial region, in order to reduce or even substantially eliminate gas friction losses, in particular air friction losses, or other disturbances of the vibration of the deflection element. This is particularly advantageous when using the microscanner for Lissajous display applications, when the deflection element and its spring suspension do not operate in ambient air, but under reduced pressure, in particular in a vacuum, since friction losses due to air damping are avoided in this way very efficiently, so that the microscanner can achieve vibration amplitudes, for example up to 100 times higher, than in the case of 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), planar or right-angled U-shaped cross-section. The dome-shaped cross-section has the particular advantage that the incoming and outgoing electromagnetic beams, in particular the laser beams, are hardly deflected by the wiring. Insofar as the incoming beam is reflected on the dome-shaped capsule section, this usually occurs in a direction different from that of the outgoing beam reflected on the deflection element, and thus undesirable interactions or beam superpositions can be effectively avoided. On the other hand, the planar cross-section and the right-angled U-shaped cross-section are distinguished in each case by a particularly simple producibility and handling during the manufacture of the microscanner. The right-angled U-shaped cross-section can also provide the advantage that any intermediate layers (spacer layers) that would otherwise be required in the substructure of the encapsulation to form a spatial region enclosed by the encapsulation that is large enough for the movement of the deflection element 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 to be deflected (and thus "incident") by the microscanner.

[0056] According to some embodiments, the control device is further configured to provide at least one modulation signal to the radiation source, whereby 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 a 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 a corresponding pixel is generated on the projection surface with the associated pixel value of the corresponding pixel of the image to be displayed by the modulation.

[0057] The features and advantages explained 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 invention result from the following more detailed description in conjunction with the figures.

[0059] The figure is explained below. [Brief description 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. [Diagram 2] 1 is a schematic diagram illustrating an example configuration of a projection system for projecting a Lissajous figure onto an observation field according to some embodiments of the present invention. [Diagram 3] FIG. 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; [Figure 4] FIG. 4 illustrates an example frequency response of the gimbal-less MiniFaros mirror from FIG. 3. [Diagram 5]2 is a schematic top view of an exemplary further gimbal-less mirror variation ("KOLA") deflection unit using an arched flexible spring as a spring device, which may be used in particular in the microscanner from FIG. 1; FIG. [Figure 6] 6 shows an exemplary recording of a cross section of a non-compensated 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. 1 is a frequency response diagram illustrating an example of maintaining the required minimum frequency distance during vibration of a microscanner according to the present invention to avoid self-synchronization as the amplitude increases, thereby resulting in 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 in accordance with some embodiments of the present invention. [Figure 8(B)] FIG. 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 in accordance with an embodiment of the present invention; however, the signal-based feedback between the two closed-loop controls is only unidirectional. [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, but with signal-based bidirectional feedback between the two closed-loop controls, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0063] The microscanner 100 comprises 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 each connecting the mirror part 130 to the frame part and formed as a connecting web.

[0064] The mirror part 130 is movably mounted in the frame part 125 via spring elements 135 which can twist so that the mirror part 130 can perform a two-dimensional, in particular biaxial, oscillatory movement with respect to the frame part 125. The connecting webs 135 thus represent the spring suspension of the mirror part 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 an amplitude-dependent mutual coupling between the vibrations 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 main 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 may comprise one or more of the following materials, among others: 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. In particular, additional dielectric layers may be used above or below the metal layer to improve the quality of the layer or to protect the metal layer from corrosion. In other cases, the mirror layer may be entirely formed from a dielectric layer stack in this way to achieve a particularly high reflectivity for a particular wavelength range. The above-mentioned materials may have both high long-term durability and good mirror properties. The shape of the mirrored reflective surface 140 may be circular, in particular as shown in the cases of Figs. 3 and 5, but this is not to be understood as a limitation. In particular, rectangular or other polygonal shapes are also conceivable. Various exemplary implementations of such a deflection element 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 is hermetically connected to the frame portion 125 of the first substrate 120 by means of a substrate bonding material 150, e.g. a glass frit material, to form a first ("upper" in FIG. 1 ) portion 175a of a cavity 175 having a cupola shape and surrounding 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 used as a bottom plate between the first substrate and the third substrate, a further, fourth substrate 115, designed as a spacer or (equivalently) a spacer layer. The third and fourth substrates may each in particular be manufactured from 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 totally sealed when second substrate 145 is used. It 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 less than 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, in particular a rectangular shape, although other shapes are possible.

[0071] The piezoelectric actuator 105 is configured to generate and transmit a vibrational motion to the deflection unit 101, in particular the mirror portion 130, when electrically actuated. In a variation of this, the vibrational motion is multi-dimensional and multiple vibrations can be excited simultaneously about different orthogonal vibration axes when the vibration frequency (frequency) falls within the resonant range of the respective vibrations. Alternatively, the drive device, in particular the piezoelectric actuator 105 in this example, can be configured such that each of the vibrations is purposefully excitable separately via a corresponding special motion component, in particular the tilt 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 a vibrational motion, in particular a resonant motion or a forced multidimensional vibrational motion, such as a biaxial Lissajous motion with respect to the frame portion 125. In the following, each uniaxial vibration component around a corresponding one of the vibration axes is referred to as a vibration. In these vibrations, the mirror portion 130 can move out of the plane of the first substrate 120 by tilting (rotating) around the respective axis of vibration, thereby penetrating the portions 175a and 175b of the cavity 175 on both sides. Due to the evacuating of the cavity 175, the remaining friction in the gas is very small, and therefore only a slight, in particular negligibly small, damping occurs.

[0073] Furthermore, the microscanner 100 includes a capacitive positioning device. This positioning device includes two electrodes on which a capacitive measurement is performed with the aim of determining the current amplitude position, and in particular the orientation, of each of the mirror portions 130. The first of the two electrodes is formed by the metallic mirror surface 140, which is therefore intended to perform a dual function (deflection of the incident electromagnetic radiation, electrode). The second of the two electrodes is embodied on the inside of the bottom plate 110 in the cavity region 175 as a corresponding metal coating 180 of 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 portion 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., electrically highly conductive (conductivity >10), that extend from the bottom electrode 180 through the bottom plate 110 to a corresponding connection pad 190 on the piezoelectric actuator 105. 6The 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 entirely electrically contacted via the connection pads 170. As a result, a capacitance measurement 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 in particular configured to control (in the sense of control or regulation) 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 for a second vibration axis A2 orthogonal to the first vibration axis (the "second vibration") 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 f of the second vibration 2,i A given minimum frequency distance f between TH In addition, the control device 195 is configured to receive measurement signals 199 from the deflection unit based on the above-mentioned capacitance measurements, in particular measurement signals indicating the instantaneous position of the deflection unit 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 leads to an instantaneous vibration frequency f of the first vibration. 1,i and the instantaneous vibration frequency f of the second vibration 2,i Details of open-loop and closed-loop control of vibration that may 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 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. With the aid of a laser 210 used as a source of electromagnetic radiation, in particular of visible light, on a mirrored surface 140 used as a reflecting surface, a beam of incident light L1 is generated and directed onto the reflecting surface 140, where it is reflected and 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 by 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 element or mirror 130 / 140, one or more further optical elements can be provided for defining the image, in particular in the form of mirrors or optical lenses.

[0078] Fig. 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 Fig. 1 or in the projection system 200 from Fig. 2. Fig. 4 shows the associated frequency response of the amplitude of the deflection element after excitation about the oscillation axis for this purpose.

[0079] In this particular embodiment, the microscanner may be designed in particular as a two-axis microscanner 300. Its deflection unit 101 comprises deflection elements 130, 140, here designed as mirror plates, suspended from a frame section 125 of a substrate 120 surrounding it and used as a support structure with three rotationally symmetrically arranged spring elements 135, which together form a spring device. The suspension is suspended in a gimbal-less manner on the frame section 125 in such a way 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 thereto, deflecting an electromagnetic beam L1 incident on the deflection elements during the simultaneous oscillation, thereby generating a nonlinear Lissajous projection in the observation field 220. This course of the two mutually orthogonal oscillation axes A1 and A2 depends on the course of the excitation resulting from 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 respectively proportional to the actual mechanical amplitudes (deflections) θ 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 as opposed to a gimbaled mirror, in which each vibration axis has its own pair of torsion suspensions.

[0082] If the MiniFaros mirror is driven conventionally, i.e. without the special control according to the invention, by internal or external forces, it first starts to oscillate linearly in axis A1 or A2. If the frequency f is then increased and approaches the resonant frequency of the second axis, the vibration energy is increasingly transferred from the first vibration about axis A1 to the second vibration about axis A2, and the mirror 130 / 140 no longer oscillates only linearly, but oscillates elliptically. This ellipse gradually becomes larger in diameter and at the same time the ellipse becomes more and more circular. This means that due to the strong interaction between the two axes, the vibration energy provided is increasingly transferred from one axis to the other.

[0083] The second axis will self-synchronize with respect to 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 because energy was supplied through only one axis.

[0084] An interesting and important feature of the 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 the above formula (3) 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 is therefore that the microscanner 100 can now only be resonated from a lower frequency to a higher frequency to achieve the maximum amplitude that occurs at the resonance point. In addition, 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 vibrations remain 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 higher amplitude for the synchronous axis (f 1,i ~~f 2,i or f 1R ~~f 2R ~~f R ), which clearly results in only one significant maximum.

[0087] Instead of an almost 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 is, i.e. the larger the spring stiffness k is, and the higher the resonance frequency f R changes more strongly. This increases the bandwidth (frequency tuning range).

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

[0089] Nonlinear 2D microscanners without gimbals almost always have very strong coupling. Strong resonance of the nonlinearity results 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 the MiniFaros mirror, which is very high, for example, with respect to the sub-1 Hz bandwidth that is typical for high-quality gimbal scanners.

[0090] These nonlinearly coupled 2D mirrors are no longer a combination of two harmonic oscillators, since according to equation (3) there is no longer a spring force that grows linearly with amplitude based on the "spring constant", 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 identical resonant frequencies, even though the resulting Lissajous image may be a circular path / elliptical shape, but may have two different resonant frequencies, spaced about 100 Hz apart in the ground state (low vibration amplitude). However, when the axis with the lower resonant frequency is vibrated, the oscillator decays towards the higher frequency, so that the frequencies of the two axes eventually overlap (f 1R ~~f 2R ), making the energy exchange completely possible. The deflection unit 300 is therefore not easily suited in practice to planar illumination of the viewing field 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, 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 is possible 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 within a certain minimum frequency distance f.TH , which would result in illumination that deviates from the elliptical shape.

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

[0094] The KOLA microscanner is a two-axis gimbal-less microscanner, in which the deflection unit 500 comprises deflection elements (mirrors) 130, 140, which are suspended on each of two opposite sides by means of flexible springs 135a, 135b, which are clamped firmly on the (rigid) frame section 125, in particular on the tip. The flexible springs 135a, 135b each have two arcuate sections which are connected to each other at their ends and otherwise extend adjacent to each other at a distance and which extend 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 an inner connecting web 136a or 136b. The respective sections of each flexible spring 135a, 135b adjacent to the frame section 125 are connected to the frame section 125 by means of an outer connecting web 137a or 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 1 / 4 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 spring device with suspension described.

[0096] The two axes or associated vibrations show strong coupling when the vibration amplitude is very large, and therefore show a significant interaction. In particular, each vibration 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 also the associated spring function k2 for the second axis A2 perpendicular thereto, and vice versa. Both spring functions are therefore time-dependent functions according to equation (3).

[0097] As a result of this periodic stiffening, the resonant frequencies of the two vibrations, 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 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 θ1(t) and θ2(t). If no controller according to the invention is used, the resulting scan pattern here upon projection in the observation field 220 therefore does not have a perfectly rectangular shape in cross section, but rather exhibits a clear constriction, especially in one axis. This is illustrated diagrammatically in FIG.

[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 an approximately rectangular shape, illumination is possible by tuning the amplitude. The frequency maximum for the two oscillations or axes can then also be maintained when oscillating at high frequencies, since these frequencies are closer to the 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 this.

[0100] FIG. 7 is a frequency response diagram illustrating an example of maintaining the necessary minimum frequency distance during oscillation of a microscanner according to the present invention to avoid self-synchronization as the amplitude increases, thereby resulting in 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 in dashed lines in FIG. 7, represents the situation when the amplitude of the oscillator with the lower resonant frequency becomes large to such an extent 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 tries 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 , which stands for minimum frequency distance f , specifies the respective instantaneous (amplitude-dependent) resonant frequency for the second oscillation axis A2. When using the microscanner according to the invention, a strong coupling between the various oscillation or associated oscillation axes A1 and A2 occurs on the one hand 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 merging of these oscillations or the shorter oscillation axes. As a result, the resulting Lissajous figure also has a linear relationship with f1 = f2 (or f 1R =f2R ), rather than representing a simple ellipse, by appropriate selection of the excitation by the drive unit 105, illumination areas of different shapes, planar, and even in particular rectangular, 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 vibration about a first axis A1 and, on the other hand, a closed-loop control unit 197 (closed loop) for a second vibration 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 vibration. 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 vibration. The two voltages V1(t) and V2(t) correspond to the control signals or controlled variable signals 199 from FIG. 1 or FIG. 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 its mechanical coupling to the deflection unit 101, applies corresponding mechanical forces F1(t) and F2(t) which in turn cause the first and second vibrations, respectively, to be in particular resonant, i.e. at the respective instantaneous resonant frequencies f 1R or f 2R Since the deflection unit 101 is a gimbal-less type, 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 has 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 look-up table 196d that stores control data representing (t) that causes the controller 196a to generate and output a time-dependent voltage V1(t) to the piezoelectric actuator 105 to operate with respect to the first vibration.

[0105] While the above-mentioned control of the first vibration is an open-loop control, the control of the second vibration is a closed-loop control, using which the instantaneous actual amplitude θ 1,i (t) and θ 2,i The instantaneous position of the deflection 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 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 by way of example in FIG. 7, a set point for the instantaneous frequency for the second vibration is also determined.

[0106] Set point θ 2,s (t) is fed to a difference 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)

number

[0107] FIG. 8B shows an example frequency curve for two oscillations of the microscanner from FIG. 8A. This example shows that the first controlled oscillation has its actual frequency f 1,i If is implemented to follow a stepped 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 is thus alternated in time with respect to the two vibrations. The coupling K2 (θ 1,i (t);θ 2,i By using a 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 loop 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 FIG. 8(A) in that instead of an open-loop control for the first oscillation, a closed-loop control, in particular a closed-loop phase control, is also provided there. Thus, the open-loop control unit is 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 biasing 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 (t) of the first vibration. 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 for the second vibration, 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 and thus support the corresponding resonant action 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 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 the 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 aiding the corresponding resonant operation of the deflection unit 101.

[0113] In this case, these respective closed loop controls for the first and second vibrations are each designed to be dynamically configured or configurable in terms of its respective slope and control speed as a function of the slope and control speed of the respective other closed loop control. 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 becomes higher with increasing amplitude.

[0114] In order to reduce or ideally completely eliminate the risk of creating control instability from the start, the maximum speed at which especially the frequency or amplitude can be changed can be limited within the control loop, possibly even as part of the calibration resulting from the calibration process. Since the frequencies are usually 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] Although 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 are merely 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 provides those skilled in the art with guidance for implementing at least one exemplary embodiment, and it is 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 Actuating devices, especially piezoelectric actuators 110 Third board, 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 board, 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 the piezoelectric actuator 105 for connecting the 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 the piezoelectric actuator 105 for connecting the bottom electrode 195 Control Devices 196 Open loop or closed loop control unit for the 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 vibration 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 the 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 the 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 driving device f frequency f1 Set point frequency of the first vibration f2 Second vibration set point 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 Set point amplitude of the first vibration on the first vibration axis A1 θ 2,i The actual amplitude of the second vibration on the first vibration axis A2 θ 2,sSet point 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 at 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 ) or defined as a function thereof; and 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 encompassing a predetermined resonance range.

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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