Projection system for projecting a lissajous pattern and microscanner with coupled oscillators

Abstract

A projection system for projecting Lissajous figures onto an observation field is disclosed, comprising a miniature scanner. The miniature scanner includes: a deflection unit having a deflection element for deflecting an incident electromagnetic beam; a support structure; and a spring device by which the deflection element is suspended from the support structure without universal joints, such that the deflection element can simultaneously undergo a first rotational oscillation about a first vibration axis and a second rotational oscillation about a second vibration axis orthogonal to the first vibration axis relative to the support structure, thereby inducing a nonlinear Lissajous projection in the observation field by deflecting the electromagnetic beam incident on the deflection element during the simultaneous oscillation. The miniature scanner also includes a control device for manipulating a drive mechanism for driving the deflection unit, such that the corresponding driving effect for at least one oscillation of the deflection element can be individually set. The spring device is also designed to modulate amplitude-dependent mutual coupling between the oscillations. The control device is also configured to manipulate the drive device according to at least one detected state variable of the first rotational oscillation, so as to generate a driving effect on the second rotational oscillation by influencing at least one state variable of the second rotational oscillation, the driving effect offsetting the gap between the corresponding instantaneous oscillation frequencies of the first and second rotational oscillations that is below a predetermined minimum frequency.

Description

Technical Field

[0001] The present invention relates to a projection system for projecting Lisajous figures onto an observation field, and a miniature scanner for such a projection system. Background Technology

[0002] A micro-scanner, specifically referred to in technical terms as a "MEMS scanner," "MEMS mirror," or "micromirror," or in English as a "micro-scanner," "micro-scanning mirror," or "MEMS mirror," is a microelectromechanical system (MEMS), or more precisely, a micro-optical-electromechanical system (MOEMS) of the type of micromirror actuator used for the dynamic modulation of electromagnetic radiation, particularly visible light. Depending on the structure, the modulation motion of a single mirror can be translational or rotational about at least one axis. The first case achieves a phase-shifting effect, and the second case achieves deflection of the incident electromagnetic radiation. Another consideration is the micro-scanner, where the modulation motion of a single mirror is rotational. Compared to the modulation of incident light through the coordinated action of multiple mirrors in a mirror array, modulation in a micro-scanner is achieved through a single mirror.

[0003] Miniature scanners can be specifically used to deflect electromagnetic radiation in order to modulate the incident electromagnetic beam relative to its deflection direction by means of a deflecting element ("mirror"). This can be particularly used to induce a Lissajous projection of the beam in an observation field. For example, it can be used to perform imaging sensing tasks or to realize display functions. Furthermore, such miniature scanners can also be used to advantageously illuminate materials and thus enable material processing. Other possible applications are in the use of electromagnetic radiation for lighting or illuminating certain open or enclosed spaces or areas, such as in environments using headlights.

[0004] Whether in the case of imaging sensors or display functions, beam deflection systems, especially miniature scanners, are used to deflect electromagnetic radiation from any other electromagnetic beam source, such as shock beams or shaped beams, in at least two dimensions (e.g., horizontal and vertical), thereby scanning or illuminating the surface of an object within the observation field.

[0005] A deflection device for a projection system that projects a Lissajous figure onto an observation field is known from patent document EP2514211B1. This device is designed to deflect a beam around at least one first deflection axis and one second deflection axis to produce a Lissajous figure. The deflection device has a deflection unit for generating vibrations (Schwingungen) around the deflection axes and a control device for generating control signals for the deflection unit at first and second control frequencies, the first and second control frequencies corresponding to the resonant frequencies of the deflection unit. The quality factor of the deflection unit is greater than 3000. The control device includes a first adjustment circuit designed to adjust the first and / or second control frequencies according to the measured phase of the vibration of the deflection unit, such that the maximum amplitude of the vibration is maintained within the resonant range of the deflection unit, wherein the control frequencies do not have a fixed integer ratio. The control device also includes a second adjustment circuit designed to influence the resonant frequencies of the first and / or second deflection axes according to the linear density of the Lissajous figure predetermined by the control frequencies, such that the linear density is within a predetermined tolerance range. The two deflection axes are decoupled by a universal joint, so that the related vibrations around the two axes are completely decoupled from each other and also occur completely independently of each other, with the aim of keeping each of the two axes in resonance.

[0006] According to patent document EP2514211B1, the deflection device is applicable to the following relationship: f 1R ≠ f 2R , (1) Among them, f 1R f represents the resonant frequency of the first axis. 2R This represents the resonant frequency of the second axis. For the mechanical torques T1 or T2 generated by the deflection springs of the first or second axis respectively, the following relationship applies: T1 = k1 θ1 and T2 = k2 θ2, (2) Where θ1 and θ2 represent the mechanical amplitudes (deflection angles) of the mirror on the first and second axes, respectively; k1 and k2 represent the spring constants of the springs on the first and second axes, respectively. Due to the decoupling of the vibration axes, in this gimbal-based miniature scanner, it is particularly easy to achieve at least approximately rectangular illumination of the observation field using Lissajous figures.

[0007] However, besides these gimbal-based micro-scanners with fully decoupled axes, there are other types of gimbal-less micro-scanners (so-called "gimbal-less mirrors" or "gimbal-less" micro-scanners or mirrors) that achieve two or more vibration axes without using the gimbal suspension of a mirror, and where non-negligible, particularly strong, coupling can occur between the individual vibration axes. The strength of this coupling can depend particularly on the amplitude.

[0008] An example of a type of micro-scanner is mentioned herein, which is constructed with a deflection unit having a mirror plate suspended from a surrounding frame by three rotationally symmetrically arranged spring elements, thereby obtaining a biaxial micro-scanner. Figure 3 A variant of this type of miniature scanner is shown, referred to as the "MiniFaros" mirror, and particularly in Hofmann et al.'s resonant biaxial 7-mm MEMS mirror for omnidirectional scanning ( Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning It is described in J. Micro / Nanolith. MEMS MOEMS, 3-11 Jan-Mar 2014 / Vol. 13(1).

[0009] Due to the coupling between the vibration axes and the corresponding oscillations of the mirrors around each of these axes, gimballess mirrors tend to cause the resonant frequencies about different vibration axes to rapidly approach each other during the oscillation process. This results in essentially only elliptical (and therefore linear, non-planar) Lissajous illumination of the observation field. This makes such at least approximately planar, and especially at least approximately rectangular, illumination of the observation field particularly difficult, or even impossible. Summary of the Invention

[0010] The object of this invention is to provide an improved, jointless miniature scanner with coupled vibration axes and a projection system equipped with the miniature scanner, which makes it possible to provide planar Lissajous illumination of an observation field. In particular, it is desirable to provide the possibility of achieving at least approximately rectangular illumination by such a miniature scanner.

[0011] The object of this invention is achieved according to the teachings of the independent claims. Various embodiments and extensions of the invention are given in the dependent claims.

[0012] A first aspect of the invention relates to a miniature scanner for a projection system used to project Lissajous figures onto an observation field. The miniature scanner includes a deflection unit having (i) a deflection element for deflecting an incident electromagnetic beam, particularly by reflection; (ii) a support structure; and (iii) a spring device. The spring device may have one or more spring elements. The deflection element is gimballess suspended from the support structure by the spring device, such that the deflection element can simultaneously undergo a first rotational oscillation about a first vibration axis and a second rotational oscillation about a second vibration axis orthogonal to the first vibration axis, thereby inducing a nonlinear Lissajous projection in the observation field by deflecting the electromagnetic beam incident on the deflection element during the simultaneous oscillation.

[0013] The miniature scanner also has a control device configured to manipulate the drive mechanism for driving the deflection unit such that the corresponding, particularly resonant, driving effect of at least one oscillation of the deflection element can be individually set.

[0014] The spring mechanism was further designed to modulate the amplitude-dependent mutual coupling between oscillations.

[0015] The control device is also configured to manipulate the drive device according to at least one detected state variable of the first rotational oscillation, so as to generate a driving effect on the second rotational oscillation by influencing at least one state variable of the second rotational oscillation, such that the driving effect cancels out the gap between the corresponding instantaneous vibration frequencies of the first and second rotational oscillations that is below a predetermined minimum frequency interval.

[0016] In the context of this invention, "Lisajous projection" should be specifically understood as a scanning of the observation field by means of electromagnetic radiation, which is caused by deflecting the radiation to at least two mutually orthogonal harmonic vibrations (oscillations) of a deflecting element in the observation field.

[0017] The "nonlinear Lissajous projection" in the context of this invention should be understood as a special case of Lissajous projection, or in other words, the illumination of the observation field by electromagnetic radiation caused by the vibrations of at least two mutually orthogonal, non-strictly harmonic vibration axes around their respective deflecting elements that deflect the radiation into the observation field. Specifically, at least a first vibration of the first vibration axis can be modulated, in terms of its amplitude, according to the instantaneous amplitude of the vibration of at least one other vibration axis, such that at least this first vibration does not exhibit linear oscillations, i.e., it does not obey Hooke's law, which has a spring constant independent of amplitude.

[0018] In this invention, "axis" or the synonym "vibration axis" should be understood as the axis of rotation (rotation axis) of rotational motion. It is a straight line that defines or describes rotation or turning.

[0019] In the context of this invention, "driving device" should be understood as a device comprising one or more actuators for driving a deflection unit, i.e., causing the deflection element to rotate and oscillate simultaneously relative to a support structure and relative to at least a first vibration axis, a second vibration axis, and possibly a third vibration axis.

[0020] The terms “comprising,” “including,” “involving,” “having,” “with,” “having,” or any other variations thereof, as may be used herein, are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a series of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent in the method or apparatus.

[0021] Furthermore, unless explicitly stated otherwise, "or" refers to an inclusive "or," not a non-inclusive "or." For example, one of the conditions A or B is satisfied is: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0022] The term “a” or “one” as used herein is defined as “one or more”. The terms “another” and “another” and any other variations thereof should be understood as “at least another one”.

[0023] The term “multiple” as used in this document should be understood as “two or more”.

[0024] With the aid of the aforementioned micro-scanner, one or more of the following advantages can be achieved, and thus the aforementioned objectives can be accomplished:

[0025] Due to the special manipulation of the drive mechanism in the aforementioned micro-scanner, despite the coupling between various oscillations or vibration axes, it is still possible to maintain a minimum frequency interval between the corresponding vibration frequencies of each oscillation, especially the resonant frequencies, so that these frequencies for different axes do not synchronize. This ultimately results in an elliptical Lissajous figure. This, in turn, enables constant, planar, and especially at least substantially rectangular illumination of the observation field within the projection range, particularly even without a gimbal. Furthermore, with this micro-scanner, Lissajous excitation of the deflection element (mirror) can be achieved even when the resonant frequencies of different axes are very close, even in the presence of many gimbal-less objects, which would be impossible without the aforementioned type of control.

[0026] Since gimballess mirrors typically have a smaller structure than gimbal-based mirrors of the same size, similar projection results can also reduce the required installation space.

[0027] Since at least one oscillator (corresponding to oscillation around a certain vibration axis) has nonlinear characteristics, that is, it does not conform to Hooke's law with a spring constant independent of amplitude over its entire amplitude range, a generally wider tuning range (frequency bandwidth) can be achieved, especially in the case of high quality, particularly compared to gimbal-based mirrors.

[0028] This miniature scanner also offers the possibility of maintaining a defined frequency ratio over a wide temperature range, as temperature-dependent fluctuations in oscillator characteristics can be compensated for by maintaining a minimum frequency interval between the frequencies of different oscillation axes. Without a gimbal mirror, temperature-dependent fluctuations in oscillator characteristics typically occur at the same intensity, direction, and timing for both oscillator axes; conversely, in a card-suspended mirror, these fluctuations typically occur sequentially and in different forms.

[0029] Even for strongly coupled axes and therefore highly nonlinear micro-scanners, the aforementioned control can typically enable oscillation at different resonant frequencies for different axes in at least two dimensions.

[0030] Preferred embodiments of the micro scanner according to the first aspect are described below. Unless explicitly excluded or technically impractical, these embodiments may be combined with each other and with other aspects of the invention as further described herein.

[0031] According to some embodiments, the control device is further configured to additionally manipulate the drive device based on at least one detected state variable of the second rotational oscillation, so as to generate a driving effect on the first rotational oscillation by influencing at least one state variable of the first rotational oscillation, which cancels out the lower than predetermined minimum frequency interval between the corresponding instantaneous oscillation frequencies of the first and second rotational oscillations. While the basic form of the aforementioned micro-scanner also specifically allows for "primary-secondary" operation, i.e., only one oscillation (secondary oscillation) is affected by the state variable of at least one detected other oscillation (primary oscillation), in the embodiments mentioned herein, both the first and second rotational oscillations can be affected by the state variable of at least one corresponding other oscillation, particularly in an equal manner. This allows for a greater variety of control options and enables particularly effective, especially fast, automatic, dynamic control of the oscillations involved, while avoiding frequency synchronization with the amplitude-related operating frequencies, particularly the resonant frequencies.

[0032] According to some alternative embodiments, the control device is configured to manipulate the drive device independently of the state variables of the second rotational oscillation, so as to generate a driving effect on the first rotational oscillation under the influence of at least one state variable of the first rotational oscillation. Therefore, these embodiments particularly achieve the aforementioned "master-slave" operation. Since only one oscillation (specifically the second rotational oscillation) must be controlled by the control device according to at least one state variable of the other (first) oscillation, the control device can be implemented particularly simply here.

[0033] According to some implementations, at least one state variable of each corresponding oscillation is determined by its amplitude, frequency, or phase, or by at least one of these variables. In particular, at least one of the detected state variables can be determined by the amplitude of the oscillation. This is particularly advantageous because, in the case of nonlinear oscillations, the spring stiffness k(θ) and therefore the frequency f(θ) relative to the axis are functions of the amplitude θ of that axis, and thus the modulation of the corresponding other oscillation according to the detected amplitude θ of that axis can instantaneously, and particularly dynamically, ensure a minimum frequency interval.

[0034] According to some implementations, the control device is configured to, in a regulating sense, manipulate the drive device based on at least one repeatedly, particularly continuously, monitored regulating variable to produce a corresponding driving effect on at least one oscillation thereby driven, the regulating variable being a state variable of the corresponding other oscillation or determined by it. With this regulation, dynamic manipulation of the drive device can be achieved particularly effectively and optimally, with the aim of ensuring minimal frequency intervals, and in particular, responding to unforeseen disturbances, which typically cannot be achieved with simple control without feedback. Furthermore, this provides the possibility of targeted compensation for amplitude-related variations in the spring stiffness of the spring device about at least one axis, particularly periodic variations, especially for nonlinear coupling effects that may cause distortion, such as the potential contraction of a planar region of the observation field illuminated by a micro-scanner. Alternatively, such nonlinear coupling effects can be amplified or modulated, particularly depending on the application, to achieve a specific shape of the illuminated planar region, particularly deviating from an elliptical or rectangular shape. For headlight applications, this can be particularly useful for the static or dynamic shaping of the illumination area (with a flat cross-section) generated by a headlight system based on this micro-scanner. Examples of such applications include anti-glare high beams for motor vehicles, where the headlight's light cone is dynamically shaped in such a way that road users in traffic areas at risk of blindness (while simultaneously in the observation field) are automatically hidden outside the high beam distribution.

[0035] According to some implementations, the detection of the control variable, particularly if the control variable used to drive the correspondingly driven oscillation is determined to be the frequency or phase of the corresponding other oscillation, or determined according to at least one of these state variables, can always occur at the same amplitude of the corresponding other oscillation, for example, always at the zero intersection of the amplitude curves of the oscillation. In this way, particularly robust regulation against disturbances can be achieved, and since the measurement conditions regarding amplitude are always the same, the regulation typically has very low measurement error.

[0036] According to some embodiments, the control device can also be configured such that both the first and second rotational oscillations can be performed in an adjustable sense based on at least one repeatedly, particularly continuously, detected adjustment variable, which is a state variable of the corresponding other oscillation or is determined by it. Here, these corresponding adjustments for the first and second rotational oscillations are designed to be dynamically configured with respect to the slope and adjustment speed of the corresponding other adjustment. This tuning is advantageous because it allows the shaft to start oscillating at approximately the same speed, and thereby allows the original resonant frequency of the shaft to change at approximately the same speed, particularly towards higher frequencies when the spring stiffness increases with the amplitude ("spring stiffening"). Due to this near-synchronous frequency change, the minimum frequency interval between the changed frequencies can be ensured particularly simply and reliably. Therefore, by adjusting the circuit in this way, it is possible to avoid adjusting one circuit much faster than the other, and thus avoid the risk of undesirable overlap of the resonant range, especially the resonant frequency of the oscillation, so as not to undesirably fall below the minimum frequency interval, and thus only linear, especially elliptical Lissajous projections appear, rather than planar, especially rectangular illumination as desired by the task.

[0037] According to some implementations, the control device is configured to manipulate the drive device based on at least one detected state variable of a corresponding other oscillation, in the sense of feedback-free control, to produce a corresponding driving effect on the oscillation thereby driven. This allows for pure "control" (open-loop control) in the technical sense. Compared to the aforementioned regulation, this open-loop control can advantageously be implemented with lower execution costs. However, it is also particularly possible to combine this open-loop control with at least one of the aforementioned closed-loop controls. Specifically, one oscillation can be regulated while another oscillation is controlled.

[0038] According to some of these control-based implementations, the control device is configured to manipulate the drive device to produce a corresponding driving effect on the corresponding oscillations driven by it, such that the drive device causes the amplitude or frequency of these oscillations to increase alternately and gradually with respect to the first and second rotational oscillations. For example, the oscillation initiation of a micro-scanner, more precisely its deflection element, can be performed by first increasing the frequency f1 of the first rotational oscillation, i.e., increasing it by a defined frequency step, then increasing the frequency f2 of the first rotational oscillation, then increasing f1 again, then increasing f2 again, and so on, until the desired driving frequency is reached. In this way, even using only control, the oscillation initiation of the micro-scanner can be achieved without undesirable overlap in the resonant range, particularly the resonant frequencies of the oscillations, and thus maintaining a minimum frequency interval. As a result, a purely elliptical Lissajous projection can be avoided, rather than illumination based on the planar, particularly rectangular, illumination desired by the task. The order of increase can be retrievably stored in memory, and is determined particularly based on a previous calibration process. In addition to or instead of calibration, this will also allow the oscillation to be configured by the prescribed and stored desired order of increase.

[0039] According to some embodiments, the control device is also configured to manipulate the drive device (i.e., control or adjust the drive device) such that the corresponding frequency of at least one oscillation, particularly an oscillation primarily driven by the manipulation, remains within a predetermined resonant range defined around the current resonant frequency of the oscillation. Here, the resonant frequency is typically defined by the frequency f at which the maximum amplitude occurs. R The resonant frequency f is given. R The resonant range can be defined specifically by the frequency value f of the resonant frequency. R The value f R ± 70%, preferred f R ± 40%, more preferably f R ± 20%, or even better f R Determined by ± 10%. (The percentage here is relative to f) R (value). This has the following particular advantage: within the resonance range, especially at the value f, the maximum amplitude of the illumination area of ​​the observation field can be achieved, and thus the maximum expansion can be realized, which is especially relevant to large-area illumination.

[0040] According to some implementations, the minimum frequency interval is set as a constant parameter. This makes implementation particularly simple, because once the parameter is determined, there is no longer a need to consider any related terms used to determine it, and in particular, it is no longer determined dynamically.

[0041] However, according to some alternative implementations, the minimum frequency interval is set as a variable parameter, which depends on the corresponding current amplitude of the first or second rotational oscillation, or the corresponding current amplitude of both oscillations. This allows for better adaptation to different system states. In particular, it enables more precise monitoring of the micro-scanner's oscillation startup, and effectively avoids undesirable overlap of resonant ranges for different axes when the frequency changes of the axes occur at a progressively faster rate than with increasing startup.

[0042] According to some alternative embodiments, the spring device is designed such that the strength of the amplitude-related mutual coupling between the first and second rotational oscillations increases steadily with the increase of the amplitude of at least one of the two oscillations. This can be achieved, in particular, by designing the spring device as a whole, or, if necessary, its individual springs, such that the spring stiffness k of the spring device or its respective spring increases with the increase of the amplitude, i.e. k = k(θ), for θ a > θ b ,k(θ a ) > k(θ b (3)

[0043] This is also known as "elastic reinforcement" or "stress reinforcement." In this way, the following advantages can be achieved in particular: through this targeted reinforcement, the frequency bandwidth or width of resonance can be increased in a desired manner. The more pronounced this effect, the more suitable a dual-axis microscanner with dual-axis "elastic reinforcement" behavior is for unregulated and very easy-to-execute open-loop operation (pure control). If only one oscillator exhibits this significant elastic reinforcement while the second does not, it may be necessary to provide at least one oscillator with regulation, as the bandwidth may be insufficient to achieve stable open-loop control. This state is less advantageous than having two oscillator suspensions exhibiting significant elastic reinforcement. If the suspensions are designed so that the oscillator with the higher resonant frequency exhibits "elastic reinforcement" and the others exhibit "elastic de-reinforcement," then whether it is pure control, regulation, or a combination thereof, it can be ensured that the oscillators do not approach each other and synchronize. If the suspension of the oscillator with the lower resonant frequency is designed to have "elastic reinforcement" behavior while the suspension of the oscillator with the higher resonant frequency is designed to have "elastic de-reinforcement" behavior, then the increase in amplitude can only be achieved through the proximity of the oscillation frequencies. This situation is generally preferred to be avoided because it results in very few usable properties. If both oscillators exhibit "elastic decay" behavior (which is relatively difficult to achieve in design and therefore rarely occurs), advantageous and simple execution can be achieved based on pure control with correspondingly stronger performance, since the frequency bandwidth of the respective resonant frequencies allows for sufficient stability of the state. According to the invention, the control must still be designed to maintain the desired frequency interval. This state can then be stably maintained again by appropriate adjustment circuitry.

[0044] According to some embodiments, the microscanner is designed as a biaxial microscanner, wherein the deflection unit has a deflection element suspended from a frame by three rotationally symmetrically arranged spring elements, which acts as a support and surrounds the deflection element. Here, the microscanner may specifically include a deflection unit of the "MiniFaros mirror" type. Microscanners according to these embodiments typically have very strong coupling between oscillations on different axes, and therefore strong nonlinear resonances. This, in turn, allows for a large tuning range, i.e., a large bandwidth (e.g., about 200 Hz in some MiniFaros mirror variants), within which the deflection element can resonate (resonance range).

[0045] According to some alternative embodiments, the microscanner is designed as a biaxial, gimbal-less microscanner, wherein: (i) the deflection unit has deflection elements that are securely suspended on opposite sides by bending springs from a rigid frame serving as a support, particularly a chip frame made of semiconductor material; and (ii) each bending spring has two arcuate segments that are connected to each other at their end faces and extend apart from each other in other respects, and extend around the deflection element, wherein the segment of each bending spring adjacent to the deflection element is connected to the deflection element, and the segment of each bending spring adjacent to the frame is connected to the frame. The deflection elements and bending springs, and optionally the frame, can be specifically constructed as a single piece, i.e., made from a single substrate. In such a microscanner, the corresponding spring stiffness with respect to each axis depends both on the instantaneous amplitude of the deflection element relative to itself and on the instantaneous amplitude of the deflection element relative to the other axis. Thus, during operation of the microscanner, the first rotational oscillation periodically modulates the second rotational oscillation, and vice versa. Furthermore, these two oscillations continuously exchange vibrational energy and simultaneously store it temporarily. Using such a mirror, planar illumination of the observation field, having a deformed, particularly contracted, rectangular shape, can be achieved, where mutual modulation can be compensated by appropriate manipulation of the drive mechanism, and at least approximately rectangular planar illumination can also be achieved.

[0046] According to some embodiments, the control device is configured to individually adjust at least one corresponding state variable of the first rotating oscillation, the second rotating oscillation, or each of the two oscillations to a target value (Sollwert) within the range of manipulating the drive device to drive the deflection unit in the sense of amplitude matching, frequency matching, or phase matching. In particular, phase matching, especially phase adjustment, is very suitable for achieving manipulated partial or complete compensation for the mutual modulation of different oscillations, and is also suitable for maintaining the resonant operation of the microscanner.

[0047] According to some embodiments, the deflecting element is suspended from the support structure in a jointless manner by a spring device, enabling it to simultaneously and additionally perform a third rotational oscillation about a third vibration axis orthogonal to the first and second vibration axes, respectively, so as to induce a nonlinear Lissajous projection in the observation field by deflecting the electromagnetic beam incident on the deflecting element during these three simultaneous oscillations. Here, the spring device is also configured to mediate the amplitude-related mutual coupling between the third rotational oscillation and the first or second rotational oscillation, or between the latter two. Therefore, using the third vibration axis, or the third rotational oscillation, it is possible to perform even more complex projection images, in which the intensity or phase of the deflected beam can be modulated (additionally) by motion about the third vibration axis, for example, through a corresponding non-uniform design of the reflectivity of the reflecting surface or the structure.

[0048] According to some embodiments, the control device is further configured to manipulate the drive device based on at least one detected state variable of the first or second rotational oscillation, so as to generate a driving effect on the third rotational oscillation by influencing at least one state variable of the third rotational oscillation. This effect cancels out the gap between the corresponding instantaneous oscillation frequencies of the first and second rotational oscillations that is below a predetermined minimum frequency interval, and also cancels out the gap between the corresponding instantaneous oscillation frequencies of the first and second rotational oscillations and the third rotational oscillation that is below a predetermined minimum frequency interval. This allows the frequency decoupling of different axes to also be extended to the third axis, and thus compensates for or avoids undesirable imaging interference that may occur during projection through this coupling.

[0049] In some embodiments, the microscanner further includes a casing through which at least the deflection element and the spring assembly are hermetically sealed, enabling the deflection element for performing oscillations within the casing to vibrately suspend from the spring assembly. Here, the casing has a casing section (Kapselabschnitt) bridging the deflection element, through which the beam to be deflected can irradiate the spatial region enclosed by the casing, and exit again from that spatial region after being deflected at the deflection element. The casing or casing section may be specifically composed of or contain a glass material that is at least mostly, preferably almost entirely, transparent to the electromagnetic beam within the spectral range relevant to the use of the microscanner.

[0050] Using such a enclosure can reduce pressure, particularly in the hermetically sealed encapsulated space, and especially by evacuating that space, in order to reduce or even largely eliminate gas friction losses, particularly air friction losses, or other interferences to the oscillation of the deflection element. This is particularly advantageous when using a miniature scanner in a Lissajous display application, where the deflection element and its spring suspension operate under reduced pressure, particularly in a vacuum, rather than in ambient air. This effectively avoids friction losses due to air damping, resulting in the miniature scanner being able to achieve, for example, vibration amplitudes up to 100 times higher than in atmospheric pressure. Accordingly, the optical resolution achievable in one or each of the first and second vibration axes can also be increased accordingly, for example, up to 100 times.

[0051] In some of these embodiments, the enclosure section has a dome-shaped, planar, or U-shaped cross-section. The dome shape is particularly advantageous because the incident and emitted electromagnetic beams, especially laser beams, are almost not deflected by the wiring. Regarding the reflection of the incident beam on the dome-shaped enclosure section, it typically occurs in a direction different from the direction of the emitted beam reflected from the deflecting element, thus effectively preventing unwanted beam interaction or superposition. On the other hand, planar and U-shaped cross-sections are characterized by their particularly simple fabrication and handling during the manufacturing process of the micro-scanner. The U-shaped cross-section also offers the advantage of avoiding or reducing the number or thickness of any intermediate layers (partitions) that might be needed in the enclosure substructure to form a sufficiently large space for the movement of the deflecting element.

[0052] The second aspect of the invention relates to a projection system for projecting Lisajous figures onto an observation field, wherein the projection system includes a microscanner according to the first aspect of the invention, particularly a microscanner according to one of the embodiments and variations described herein.

[0053] According to some implementations, the projection system may specifically include a beam source for generating an electromagnetic beam to be deflected (and thus “incident”) by a micro-scanner.

[0054] According to some embodiments, the control device can be further configured to provide at least one modulation signal to the beam source based on the modulated incident electromagnetic beam. This modulation may specifically relate to its temporal or local intensity profile. However, depending on the type of beam source, other types of modulation may also be considered, particularly modulation of the wavelength (e.g., color) or wavelength distribution of the beam emitted by the beam source. When projecting an image, modulation is performed accordingly based on the instantaneous deflection direction, thereby generating corresponding pixels on the projection surface through modulation, each pixel having a corresponding pixel value of the corresponding pixel in the image to be displayed.

[0055] The features and advantages described in the first aspect of the invention also apply to the projection system described in the second aspect of the invention. Attached Figure Description

[0056] Other advantages, features, and possible applications of the present invention will be given in the following detailed description taken in conjunction with the accompanying drawings. Wherein:

[0057] Figure 1 An exemplary structure of a micro scanner according to some embodiments of the present invention is illustrated schematically;

[0058] Figure 2 The schematic diagram illustrates an exemplary structure of a projection system for projecting Lisajous figures onto an observation field according to some embodiments of the present invention;

[0059] Figure 3 The schematic diagram shows a top view of a deflection unit with a gimbal-less MiniFaros mirror, which can be used in applications according to... Figure 1 In the miniature scanner;

[0060] Figure 4 It shows according to Figure 3 An exemplary frequency response of a knuckleless MiniFaros mirror;

[0061] Figure 5 The schematic diagram shows a top view of a deflection unit in another exemplary gimbal-less variant (“KOLA”) using an arc-shaped bending spring as the spring mechanism, which can be used in accordance with... Figure 1 In the miniature scanner;

[0062] Figure 6 It is shown that in having according to Figure 5 An exemplary image of a cross-section of a planar irradiation region in the case of a miniature scanner with a deflection unit, the planar irradiation region being uncompensated and shrinking and deformed relative to a rectangle;

[0063] Figure 7 A frequency response diagram is shown to illustrate an example of maintaining the required minimum frequency interval during the start-up of the microscanner according to the invention, in order to avoid self-synchronization as the amplitude increases and thus result in rigid phase and frequency coupling.

[0064] Figure 8 (A) illustrates some embodiments of the present invention, according to Figure 1 A block diagram of an exemplary combination of control / regulation (one axis open loop, the other axis closed loop) of a micro scanner;

[0065] Figure 8 (B) shows that when according to Figure 8 (A) Exemplary frequency curves of two oscillations when the micro scanner starts oscillating;

[0066] Figure 9 An embodiment of the present invention is shown, according to Figure 1 A block diagram of an exemplary dual-adjustment (both axes are closed loop) micro-scanner, but in which signal-based feedback between the two adjustments occurs only unidirectionally; and

[0067] Figure 10 An embodiment of the present invention is shown. Figure 1The block diagram shows an exemplary dual-adjustment (both axes are closed loops) of a micro-scanner, wherein signal-based bidirectional feedback occurs between the two adjustments.

[0068] In the accompanying drawings, the same or corresponding elements of the invention are always referred to by the same reference numerals. Detailed Implementation

[0069] Figure 1 An exemplary embodiment of a microscanner 100 according to an exemplary embodiment of the present invention is schematically shown in a cross-sectional view, having a drive device 105 for driving the microscanner 100.

[0070] The micro-scanner 100 has a piezoelectric actuator 105 as a driving device, which also forms a base plate on which a stacked multilayer structure formed by different substrates stacked on top of each other is arranged, which together form the deflection unit 101 of the micro-scanner. The core of this multilayer structure is formed by a first substrate 120 (chip) made of semiconductor material, which is structured into different, interconnected sub-regions. These sub-regions include a frame sub-region 125, a mirror region ("mirror") 130 used as a deflection element, and a plurality of spring elements 135 that connect the mirror region 130 to the frame sub-regions respectively and form connecting webs.

[0071] The mirror region 130 is movably mounted in the frame sub-region 125 via a torsionible spring element 135, meaning that the mirror region 130 can perform two-dimensional, particularly biaxial, vibrational motion relative to the frame sub-region 125. Therefore, the connecting web 135 represents the spring suspension of the mirror region 130. These connecting webs, or spring elements 135, together form the spring device of the deflection unit 101. This spring device is designed here to mediate the amplitude-dependent mutual coupling between oscillations to a single vibration axis. This results in a nonlinear spring characteristic of the spring device as a whole.

[0072] The mirror region 130 has a metal coating 140 on one of its main surfaces, such that the metal layer 140 forms a mirror-like reflective surface for deflecting incident electromagnetic beams, particularly laser beams, in the visible or infrared range of the electromagnetic spectrum. The mirror region 130 and its coating 140 thus form the deflection element of the deflection unit 101.

[0073] Specifically, the metal layer 140 may comprise 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, etc. In particular, additional dielectric layers may be used above or below the metal layer to improve the coating quality or protect the metal layer from corrosion. In other cases, the mirror layer (Spiegelschicht) may be formed entirely of stacked dielectric layers to achieve particularly high reflectivity for a specific wavelength range. The aforementioned materials can possess both high long-term durability and good mirror performance. The shape of the mirrored reflective surface 140 may be circular, particularly as... Figure 3 and Figure 5 As shown, this should not be construed as limiting. Rectangular or other polygonal shapes may also be considered. References will be made below. Figure 3 and Figure 5 This section will describe in detail various exemplary embodiments of such a deflection element, or in particular various exemplary embodiments of the first substrate 120.

[0074] The deflection unit 101 may also optionally include a second substrate 145 made of glass material. This second glass substrate has a dome shape and is hermetically connected to the frame sub-region 125 of the first substrate 120 via a substrate bonding material 150 (e.g., glass-friction materials) to form a first (in) cavity 175 on either side surrounding the mirror region 130 above it. Figure 1 The "above" sub-region 175a.

[0075] On the side of the first substrate 120 opposite to the second substrate 145, there is a third substrate 110 serving as a base plate in the multilayer structure 101, and another fourth substrate 115 designed as an abstandshalter or (equivalently) spacerschicht between the first substrate and the third substrate. The third and fourth substrates may each be made of semiconductor material.

[0076] The fourth substrate 115 is structured to have a cavity disposed below the mirror region 130, such that the cavity, together with its bottom side boundary provided by the base plate 110, forms the second (in) cavity 175. Figure 1 (a) Subregion 175b, “below”.

[0077] Each adjacent individual substrate is hermetically connected to each other, for example, by substrate bonding material 150 or 155, such that when the second substrate 145 is used, the cavity 175 is formed hermetically. Preferably, this cavity is emptied so that a residual gas pressure is present therein, preferably significantly lower than normal conditions (101.325 kPa = 1013.25 mbar), preferably lower than 10 kPa / 10+1 kPa (10 -1 mbar), especially preferred at 10 mbar -1 kPa (10) -3 (mbar). Typically, the first to fourth substrates 110, 115, 120, and 145 each have the same basic shape, particularly a rectangular shape, but other shapes are also possible.

[0078] The piezoelectric actuator 105 is configured to generate and transmit vibrational motion during its electrical manipulation to the deflection unit 101, particularly to its mirror region 130. In one variation, this vibrational motion is multidimensional, allowing multiple oscillations to be excited simultaneously for different orthogonal vibration axes when the vibrational frequency (frequency) enters the resonant range of the corresponding oscillation. Alternatively, the drive device, particularly the piezoelectric actuator 105 in this example, can be configured such that each oscillation can be individually and specifically activated via a corresponding specific motion component, particularly by tilting the actuator about an axis extending parallel to the corresponding vibration axis.

[0079] Through these and other means, mirror region 130 and its mirror surface 140 can be excited to perform vibrational motion, particularly resonant or forced multidimensional vibrational motion, such as biaxial Lissajous motion relative to frame sub-region 125. Hereinafter, the uniaxial vibrational component about a corresponding vibration axis will be referred to as an oscillation. In these oscillations, mirror region 130 can be moved out of the plane of the first substrate 120 by tilting (rotating) about the corresponding vibration axis, and thereby sinking into sub-regions 175a and 175b of cavity 175 on both sides. Since cavity 175 is emptied, the residual friction in the gas is very low, thus only small, particularly negligible, damping occurs.

[0080] Furthermore, the micro-scanner 100 includes a capacitive position determination device. This device comprises two electrodes, between which a capacitance measurement is performed to determine the corresponding current amplitude position, and in particular the orientation, of the mirror region 130. The first of these two electrodes is formed by a metallic mirror 140, thus performing a dual function (deflection of incident electromagnetic radiation; electrode). The second of these two electrodes is constructed as a corresponding metallic coating 180 within the cavity region 175, inside the base plate 110. In this example, the bottom electrode 180 is designed as a multi-part structured metallic layer. The shape of the bottom electrode 180 substantially corresponds, in type and preferably approximately in size, to the shape of the mirror region 130 or its reflective layer or mirror surface 140 when placed parallel to it in its non-deflection idle state.

[0081] The bottom electrode 180 is electrically contacted via one or more so-called through-holes, which are filled with highly conductive material (conductivity > 10). 6 A connection channel, typically metallic, made of S / m material, extends from the bottom electrode 180 through the base plate 110 to a corresponding connection pad 190 on the piezoelectric actuator 105. The mirror electrode 140 is electrically connected via a redistribution layer to a connection pad 165 on the first substrate 120, located outside the dome formed by the second (glass) substrate, and from there to another connection pad 170 on the piezoelectric actuator 105 via a bonding wire 160. Thus, the mirror electrode 140 is electrically contacted entirely via the connection pad 170. As a result, capacitance measurements for determining the position of the mirror region 130 can be performed between the connection pads 190 and 170.

[0082] The micro-scanner 100 also includes a control device 195, which is specifically configured to control the piezoelectric actuator 105 to drive the deflection unit by means of a corresponding electrical control signal 198 (in the sense of control or regulation), such that at least one oscillation with respect to the deflection elements 130, 140 can be individually set with a corresponding, particularly resonant, driving effect. Specifically, the control device is configured, and in particular programmed, to control the piezoelectric actuator 105 according to at least one detected state variable of an oscillation about the first vibration axis A1 (“first rotational oscillation”), so as to induce a driving effect for an oscillation about a second vibration axis A2 orthogonal to the first vibration axis (“second rotational oscillation”) by influencing at least one state variable of the second rotational oscillation, which cancels out the instantaneous oscillation frequency f of the first rotational oscillation. 1,i The instantaneous oscillation frequency f of the second rotational oscillation 2,i The interval between them is lower than the predetermined minimum frequency interval f THFurthermore, the control device 195 is configured to receive a measurement signal 199 from the deflection unit based on the aforementioned capacitance measurement, specifically a measurement signal indicating the instantaneous position of the deflection unit with respect to axes A1 and A2. In particular, the amplitude, frequency, and phase of each oscillation are considered as state variables.

[0083] Alternatively, the control device 195 can be configured to control in the opposite direction, i.e., to manipulate the piezoelectric actuator 105 according to at least one detected state variable of the second rotational oscillation, so as to induce a driving effect on the first rotational oscillation by influencing at least one state variable of the first rotational oscillation, which cancels out the instantaneous oscillation frequency f of the first rotational oscillation. 1,i The instantaneous oscillation frequency f of the second rotational oscillation 2,i The intervals between them are below a predetermined minimum frequency. The control and regulation of the oscillations, which can be performed by means of the control device 195 in this invention, will be described in detail below, particularly with reference to... Figures 7 to 10 .

[0084] Figure 2 An exemplary structure of a projection system 200 for projecting Lisajous figures onto an observation field 220 is schematically shown. For this purpose, in particular, a system based on... Figure 1 A miniature scanner 100. Using a laser 210, which serves as a source of electromagnetic beams, particularly visible light, an incident light beam L1 is generated on a mirrored surface 140 that acts as a reflector and guided onto the reflector 140 so that it is reflected there and projected as a deflected beam onto an observation field 220, thus illuminating it at least partially. The observation field can be defined by the projection surface, such as a smooth surface, like a projection screen, or a floor or road surface. Besides... Figure 2 In addition to the simplest case of pure reflection shown, one or more other optical elements, in particular in the form of mirrors or optical lenses, may be provided in addition to the deflecting element or mirror 130 / 140 to define the projection.

[0085] Figure 3 A schematic top view of a deflection unit 300 with a gimbal-less MiniFaros mirror is shown, which can be particularly used in... Figure 1 The miniature scanner 100 shown is or Figure 2 In the projection system 200 shown. Figure 4 The frequency response of the deflection element with respect to the amplitude of the vibration axis during the excitation process is shown.

[0086] In this embodiment, the micro-scanner can be specifically designed as a dual-axis micro-scanner 300. Its deflection unit 101 here has deflection elements 130, 140 configured as mirror plates. The deflection element is suspended from a frame sub-region 125 surrounding it, which serves as a support structure, by means of three rotationally symmetrically arranged spring elements 135, which together form a spring device. This suspension is configured such that the deflection elements 130, 140 (mirrors) are elastically suspended from the frame sub-region 125 without gimbals, such that a first rotational oscillation about a first vibration axis A1 and a second rotational oscillation about a second vibration axis A2 orthogonal to the first vibration axis can be performed simultaneously with respect to the frame sub-region, so as to form a nonlinear Lissajous projection in the observation field 220 by deflecting the electromagnetic beam L1 incident on the deflection element during the simultaneous oscillation. The process of the two mutually orthogonal vibration axes A1 and A2 depends on the excitation process due to the rotational symmetry about the three suspensions, which are spaced 120 degrees apart along the circumference of the mirror.

[0087] Due to this special configuration of the spring mechanism, the oscillations around the two axes A1 and A2 are strongly coupled, making them no longer independent. In fact, unlike harmonic oscillators, in this case, the effective spring stiffnesses k1 and k2 are respectively the actual mechanical amplitude (deflection) θ. 1,i (t) and θ 2,i (t) is a time function with respect to the two vibration axes A1 and A2: k1 = k1(θ 1,i (t), θ 2,i (t)) and k2 = k2(θ) 1,i (t), θ 2,i (t)) (3)

[0088] In the MiniFaros mirror type, the coupling or interaction between the two oscillations is usually very clearly visible. Both oscillation axes are defined by all three springs 135. This means that, compared to a mirror with a universal joint, all three springs 135 are also contained in both axes A1 and A2. In the latter, each oscillation axis has its own pair of torsional suspensions.

[0089] If the MiniFaros mirror is driven in a conventional manner, i.e., driven by internal or external forces without the special control according to the invention, it initially begins to rotate linearly on one axis A1 or A2. If the frequency f is subsequently increased and approaches the resonant frequency of the second axis, more and more vibrational energy migrates from the first rotational oscillation around axis A1 to the second rotational oscillation around axis A2, and the mirror 130 / 140 no longer oscillates merely linearly but elliptically. The diameter of this ellipse becomes increasingly larger, and the ellipse itself becomes increasingly rounded. This means that the applied vibrational energy is increasingly transferred from one axis to the other due to the strong interaction between the two axes.

[0090] Here, the second axis itself is synchronized with respect to its phase position because there is no phase relationship between the axes at this time, but rather an ellipse or circle, which is equivalent to the synchronized phase position of the two axes A1 and A2, even though the energy is provided by only one axis.

[0091] An interesting and important feature of the strongly interactive axis is the nonlinear operation of the spring suspension 135. This causes significant nonlinear resonances, which in the case of the MiniFaros mirror is the so-called "stress reinforcement" or "elastic reinforcement," with a "tilted tip" pointing towards higher frequencies, such as... Figure 4 The frequency response is shown as, for example, with respect to the vibration amplitude of shaft A1.

[0092] In equation (3) above, the spring stiffnesses k1 and k2 increase as a function of the first amplitude θ1 and the second amplitude θ2, respectively. As a result, the micro-scanner 100 can only move from a low frequency to a high frequency at resonance to achieve the maximum amplitude at the resonance point. Furthermore, it must start from the lower of the two resonant frequencies to fully excite the oscillations about both axes A1 and A2. If it starts from the higher of the two resonant frequencies, the vibration remains uniaxial.

[0093] Figure 4 The corresponding frequency response of drive unit 105 at three different operating voltages of 40V, 80V, and 120V is shown, where, with other operating modes being equal, higher operating voltages correspond to larger maximum amplitudes. It can be clearly seen that when oscillation begins at an increasing frequency curve (“upward”), the resulting sharp amplitude curve produces only a single, significant maximum value, representing the synchronous shaft (f). 1,i ≈ f 2,i or f 1R ≈ f 2R ≈ f R ).

[0094] When oscillation begins with an increased amplitude, the resonance curve for higher frequencies widens significantly, rather than exhibiting a nearly vertical, narrow resonance peak. The greater the amplitude, the greater the suspension stiffness; that is, the more the spring stiffness k increases, and the higher the resonant frequency f... R It becomes larger. This results in a wider bandwidth (frequency tuning range).

[0095] Conversely, if the oscillation is initiated at a lower excitation frequency ("downward"), a significantly different frequency response will occur, maintaining the resonant frequencies f of the two axes A1 and A2 separately. 1R and f 2R There will be a single, and not very prominent, maximum value.

[0096] Nonlinear 2D microscanners without gimbal suspension always have very strong coupling. This strong nonlinear resonance results in a larger tuning range, i.e., a large bandwidth in which the microscanner can resonate. For example, for a MiniFaros mirror, this could be 200 Hz according to an embodiment, which is very high compared to the typical bandwidth of less than 1 Hz for high-quality gimbal scanners.

[0097] Such a nonlinearly coupled 2D mirror is no longer a combination of two harmonic oscillators because, according to equation (3), there is no longer a spring force based on the “spring constant” that increases linearly with amplitude, i.e., no harmonic behavior. Instead, it is a strong nonlinear spring force that depends on amplitude and can be described as a so-called “Duffing-Oszillator”.

[0098] It should be noted that although the resulting Lissajous images may have circular / elliptical trajectories, the MiniFaros mirrors typically do not have the same, but rather two different resonant frequencies, which can be about 100 Hz apart in the ground state (low amplitude). However, since the axes begin to oscillate at very low resonant frequencies, the oscillator tends to detune to too high frequencies, such that the frequencies of the two axes become increasingly correlated until they eventually overlap (f...). 1R ≈ f 2R And until energy exchange is fully permitted. Therefore, except for replacing the desired plane illumination with elliptical, especially circular, line imaging, the deflection unit 300 is not practically suitable for plane illumination of the observation field by means of Lisajous projection.

[0099] On the other hand, if the control device according to the invention is a drive device for controlling the micro-scanner 100, planar, and in particular at least approximately rectangular, illumination can be achieved by adjusting the resonant amplitude. Even when oscillating at an increased frequency, the maximum frequencies of the two oscillations or axes can be maintained because the frequency distance between these frequencies can always be adjusted so that it does not fall below a predetermined minimum frequency interval f. TH This results in lighting that is not elliptical.

[0100] Figure 5 The schematic diagram shows a top view of a deflection unit 500 according to another embodiment of the deflection unit 101, particularly the substrate 120, which has a gimbal-less mirror (referred to herein as type "KOLA"). This embodiment can also be used particularly for... Figure 1 The miniature scanner 100 shown Figure 2 The projection system 200 shown.

[0101] The KOLA micro scanner is a biaxial, jointless micro scanner in which the deflection unit 500 includes deflection elements (mirrors) 130, 140, which are suspended by rigidly clamped bending springs 135a, 135b from a (rigid) frame sub-region 125 serving as a support, specifically from two opposing sides of the chip. Each of the bending springs 135a, 135b has two arcuate segments that are connected to each other at their end faces and otherwise extend side-by-side and spaced apart from each other, extending around the deflection elements 130, 140. The corresponding portion of each bending spring adjacent to the deflection elements 130, 140 is connected here to the deflection elements 130, 140 via an inner connecting web 136a or 136b. The corresponding portion of each bending spring 135a, 135b adjacent to the frame sub-region 125 is connected to the frame sub-region 125 via an outer connecting web 137a or 137b.

[0102] The lengths of the bending springs 135a and 135b can be specifically designed so that they extend as long and wide as possible along the outer contour of the deflecting element, more precisely, preferably departing from the vibrating rotation axis A1 (approximately a quarter circle on each side) and then returning to the axis A1 when viewed vertically. This orientation of the bending springs allows the deflecting elements 130 and 140 to move on two mutually orthogonal vibrating axes A1 and A2, their respective supports defined by the structure of the spring device with the suspension.

[0103] These two axes, or the associated oscillations, exhibit strong coupling when the amplitude of the oscillations is very large, and thus show obvious interaction. In particular, each amplitude of the deflection elements 130 and 140 around the first axis A1 immediately leads to the strengthening of the entire bending spring 135a or 125b, but this affects the two oscillation axes A1 and A2. As a result, the associated spring constant, or the spring function k1 related to the amplitude, is periodically detuned not only with respect to the oscillations of the first axis A1, but also periodically detuned with respect to the associated spring function k2 of the second axis A2 perpendicular to the first axis, and vice versa. Therefore, according to equation (3), both spring functions are time-dependent functions.

[0104] The result of this periodic reinforcement is that the corresponding resonant frequencies f of the two oscillations are... 1R and f 2R The vibration periodically shifts to axes A1 and A2. This means that the periodic vibration of the first axis A1 causes the resonant frequency f of the second axis A2 to change. 2R Detuning causes the oscillation of the second axis A2 to periodically reduce the resonant frequency f of the first axis A1. 1R Detuning. Furthermore, these two axes A1 and A2 permanently transmit vibrational energy, exchanging and storing it with each other.

[0105] This results in modulated mirror vibration amplitudes θ1(t) and θ2(t) in the KOLA microscanner. Therefore, without the control according to the invention, the scanning pattern thus generated in the observation field 220 during projection does not have a perfectly rectangular shape in cross-section, but rather exhibits significant contraction, particularly along one axis. This in Figure 6 It is shown schematically in the middle.

[0106] On the other hand, if the control device according to the invention is used to control the drive mechanism of the micro-scanner 100, planar, and in particular at least approximately rectangular, illumination can be achieved through amplitude tuning. When oscillating at an increased frequency, the maximum frequencies of the two oscillations, or axes, can also be maintained, because these frequencies are always relative to their frequency distance f. 1,i -f 2,i or |f 1,i -f 2,i They are set so that they will not fall below a predetermined minimum frequency interval f. TH .

[0107] Figure 7 A frequency response diagram is shown to illustrate an example of maintaining the required minimum frequency interval during the start-up of the microscanner according to the invention to avoid self-synchronization and thus rigid phase and frequency coupling as the amplitude increases.

[0108] Here, the three curves at the bottom show the actual frequency response of the amplitude of the vibration of the deflection element (about either of the two axes) at different consecutive time points t1, t2, and t3 during the start-up process. Figure 7 The top curve, shown by the dashed line, represents the state when the amplitude of an oscillator with a very low resonant frequency further oscillates to a resonance on one axis superimposed on the resonance on another axis (with a higher resonant frequency). In this state, the first rotating oscillator attempts to synchronize with the second rotating oscillator. This "symbiosis" (Zusammenwachsen) can only be prevented when the two resonators maintain their separation by synchronizing their oscillations and thus exhibiting stress reinforcement in the same direction. f1(f 1R (abbreviation) represents the instantaneous (amplitude-dependent) resonant frequency of the first vibration axis A1, f2 (f 2R The abbreviation ( ) correspondingly represents the corresponding instantaneous (amplitude-dependent) resonant frequency of the second vibration axis A2. When using the micro-scanner according to the invention, on the one hand, strong coupling occurs between different oscillating or related vibration axes A1 and A2 due to the use of the gimballess deflection unit. On the other hand, the synchronization of these oscillating or short vibration axes is actively canceled by the control unit 195 to maintain a minimum frequency interval f. TH And thus prevent the two resonant frequencies f1 and f2 (or f 1R and f 2R The convergence of these ellipses is known as "Zusammenlaufen". As a result, the resulting Lissajous figures do not simply represent ellipses, such as f1 = f2 (or f...). 1R = f 2R Instead of the case of ), by appropriately selecting the excitation of the driving unit 105, it is possible to generate illumination areas of different shapes, planar, and even rectangular shapes in the observation field 220.

[0109] Figure 8 (A) shows the following based on Figure 1 A block diagram of an exemplary embodiment 800 of a micro scanner having combined control / regulation (one axis open loop, the other axis closed loop).

[0110] The control device 195 has a control unit 196 (open-loop) for a first rotational oscillation about a first axis A1, and an adjustment unit 197 (closed-loop) for a second rotational oscillation about a second axis A2. The controller 196 provides a first control signal in the form of a time-dependent voltage V1(t) for controlling the piezoelectric actuator 105 regarding the first rotational oscillation. On the other hand, the adjuster 197 provides a second control signal (more precisely, an adjustment parameter signal) in the form of a time-dependent voltage V2(t) for controlling the piezoelectric actuator 105 regarding the second rotational oscillation. These two voltages V1(t) and V2(t) correspond to... Figure 1 or Figure 2 The control signal or adjustment parameter signal 199. Due to this manipulation, the piezoelectric actuator 105 performs motion on the first and second vibration shafts A1 and A2, and hereby applies corresponding mechanical forces F1(t) and F2(t) due to its mechanical coupling to the deflection unit 101 to drive the first and second rotational oscillations, in particular each resonance, i.e., according to their respective instantaneous resonant frequencies f. 1R or f 2R Since the deflection unit 101 is a type without a universal joint, there is a non-negligible coefficient between the two vibration axes A1 and A2, which depends on the actual amplitude θ. 1,i (t) and θ 2,i (t) and therefore also time-dependent mechanical coupling, namely the mechanical coupling K1(θ) with respect to the first rotational oscillation. 1,i (t); θ 2,i (t)) and the mechanical coupling K2(θ) with respect to the second rotational oscillation. 1,i (t); θ 2,i (t)).

[0111] The control unit 196 has a control manager 196a for the first rotational oscillation, which can access a lookup table 196d that stores a time-based target value curve θ representing the amplitude of the first rotational oscillation during the initiation of the micro-scanner 800. 1,s The control data is V1(t). Based on this control data, the control manager 196a generates a time-dependent voltage V1(t) for controlling the piezoelectric actuator 105 with respect to the first rotational oscillation, and outputs it to the piezoelectric actuator 105 to manipulate it.

[0112] When the control of the first rotational oscillation is a feedback-free (open-loop) control, the adjustment of the second rotational oscillation has a feedback loop (closed-loop). Through this feedback loop, the bottom electrode 180 of the deflection unit 101 detects and adjusts the instantaneous actual amplitude θ. 1,i (t) and θ 2,i The instantaneous positions of the deflection elements (mirrors) 130 and 140 obtained by (t) are fed back to the adjustment unit 197 as input signals. The feedback amplitude θ 1,i (t) is here fed to the control manager 197a of the adjustment unit 197, which takes into account the (optionally time-related) minimum frequency interval f. TH Determine the target value θ of the amplitude of the second rotational oscillation under the given conditions. 2,s (t). Since this amplitude is interdependent with the frequency of the second rotational oscillation, such as Figure 7 As shown in the example, the target value of the instantaneous frequency of the second rotational oscillation is also determined.

[0113] The target value θ 2,s (t) is fed to a differential detector (Differentzdetektor) 197b for the second rotational oscillation, which can be specifically configured to detect the target value θ. 2,s (t) and the actual value θ of the amplitude of the second rotating oscillation fed back. 2,i The phase difference Δ between (t) 2(t), and generates a phase-synchronized adjustment parameter signal V2(t) through a downstream connected regulator or loop filter, and outputs it to the piezoelectric actuator 105. Alternatively or additionally, amplitude adjustment or direct frequency adjustment can also be provided in a similar manner.

[0114] Figure 8 (B) shows that, according to Figure 8 (A) Exemplary frequency curves of two oscillations when the miniature scanner starts oscillating. According to this example, if the controlled first rotational oscillation is achieved by making its actual frequency f... 1,i If the operation is carried out using a stepped curve represented by a continuous characteristic curve, then the adjustment of the second rotational oscillation can be designed to use a stepped curve represented by a dashed characteristic curve, where the minimum frequency interval f is always maintained. TH Therefore, the oscillation of the micro-scanner here is about two oscillation times occurring alternately. In the second rotational oscillation (which occurs via coupling K2(θ)... 1,i (t); θ 2,i (t) (associated with the first rotational oscillation) When using adjustment, it is possible to maintain the minimum frequency spacing f TH Simultaneously, it achieves dual-axis oscillation.

[0115] Figure 9 In another embodiment 900 of the invention, according to Figure 1 A block diagram of an exemplary dual-adjustment (both axes are closed loop) micro-scanner is shown, but signal-based feedback between the two adjusters occurs only in one direction.

[0116] The Mini Scanner 900 is based on Figure 8 (A) A miniature scanner 800, in which adjustment, particularly phase adjustment, is provided instead of control for the first rotational oscillation. Accordingly, the control unit is replaced by the adjustment unit 196, which also measures the actual amplitude θ of the first rotational oscillation at the deflection element. 1,i (t) and feeds it back to the adjustment unit 196 so that an adjustment loop is also obtained for the first rotational oscillation.

[0117] As a result, each of the two oscillations now has its own regulation, with the regulation of the first rotational oscillation acting as the master regulation, in which case it does not consider the regulation of the second rotational oscillation and therefore does not receive the actual amplitude θ of the second rotational oscillation fed back. 2,i (t). On the other hand, the regulation of the second rotational oscillation acts as a slave regulation, the target value of which is determined by the actual amplitude θ of the first rotational oscillation fed back. 1,i (t) and the minimum frequency interval f used as another input parameter TH Therefore, ensuring the maintenance of the minimum frequency interval depends on the adjustment of the second rotational oscillation, while each of the two adjustments additionally ensures that the corresponding drive signals V1(t) and V2(t) act in phase with the actual progress of their respective oscillations, and thus support the corresponding resonant operation of the deflection unit 101.

[0118] Figure 10 An embodiment 1000 according to the present invention is shown. Figure 1 The block diagram shows an exemplary dual-adjustment (both axes are closed loops) block diagram of a micro-scanner, in which bidirectional signal coupling of the adjustment exists.

[0119] The Mini Scanner 1000 is based on Figure 9 The miniature scanner 900, in which the modulation of the first rotational oscillation is now additionally used to receive the actual amplitude θ of the second rotational oscillation. 2,i Feedback of (t) and minimum frequency interval f TH As the input signal, this results in a symmetrical structure in which the modulation of the first rotational oscillation is influenced by the second rotational oscillation, and vice versa. Therefore, ensuring the maintenance of a minimum frequency interval depends on the modulation of the two oscillations, while each of these modulations additionally ensures that the corresponding drive signals V1(t) and V2(t) act in phase with the actual progress of their respective oscillations, and thus supports the corresponding resonant operation of the deflection unit 101.

[0120] Here, each of these adjustments for the first and second rotational oscillations is dynamically configured, or designed to be dynamically configurable, with respect to its respective slope and control speed, according to the slope and control speed of the corresponding other adjustment. This tuning is advantageous because it allows the shaft to start oscillating at approximately the same rapid rate, and thus enables the original resonant frequency of the shaft to shift at approximately the same rapid rate, particularly towards higher frequencies as the spring stiffness increases with the amplitude.

[0121] To reduce or ideally eliminate the risk of regulation instability from the outset, the maximum rate at which the frequency or amplitude can be changed can be limited in the regulation circuit, and if possible, also limited within the calibration framework generated by the calibration process. Since the frequency is typically very high, such as several kilohertz, highly controlled protective actions can also be performed for this purpose within a very short time.

[0122] While at least one exemplary embodiment has been described, it should be noted that numerous variations thereof may exist. It should also be noted that the described exemplary embodiments are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the apparatus and methods described herein. Rather, the foregoing description will provide guidance to those skilled in the art in implementing at least one exemplary embodiment, wherein it should be understood that various changes may be made to the operation and arrangement of the elements described in the exemplary embodiments without departing from the subject matter defined in the appended claims and their legal equivalents. List of reference numerals 100 Miniature Scanners 101 deflection unit 105 Drive devices, especially piezoelectric actuators 110 Third substrate, base plate 115 Fourth substrate, spacer 120 First substrate 125 Frame Sub-region 130 Mirror Area 135 Spring Element 135a, b Bending springs 136a, b Internal connecting web 137a, b External connecting web 140 Metal mirror coating, mirror electrode 145 Second substrate, dome-shaped 150 Substrate bonding materials 155 Another substrate bonding material 160 joint line 165 Connection pads on the first substrate 120 are used to connect the top electrode 140 The connecting pads on piezoelectric actuator 105 are used to connect the upper electrode 140. 175a Upper region of cavity 175 175b Lower region of cavity 175 180 Structured, possibly multipart bottom electrode 185 Through-hole with solder bumps for contacting piezoelectric actuators. The connection pads on piezoelectric actuator 105 (190) are used to connect the bottom electrode. 195 Control device 196 Control unit or regulating unit for the first rotational oscillation 196a Control Manager for First Rotational Oscillation 196b Differential detector for first rotational oscillation 196c is used as a regulator or loop filter for the first rotating oscillation (in a phase adjustment circuit). 196d lookup table 197 Adjustment unit for the second rotational oscillation 197a Control Manager for Second Rotational Oscillation 197b Differential detector for second rotational oscillation 197c is used as a regulator or loop filter for the second rotating oscillation (in a phase adjustment circuit). 198. Measurement signals and position measurements fed back to the control circuit. 199 Control signal or adjustment parameter signal 200 projection system 210 Light sources, especially lasers 220 Observation field, especially the projected surface 300 deflection unit with a gimbal-less MiniFaros mirror Frequency response of a 400° MiniFaros mirror without gimbal 500 Deflection unit with KOLA mirror without gimbal 600 condensed and deformed planar irradiation area 700 Frequency Response 800 Block diagram of hybrid control (open loop) / regulation (closed loop) 900 Block diagram of unidirectional coupled dual-axis control (closed loop) 1000 Block diagram of bidirectional coupling regulation (closed loop) A1 First Vibration Axis A2 Second Vibration Shaft F1 and F2 are the shaft-specific driving forces from the drive unit to the deflection element. K1 (...) is mechanically coupled to the first axis. K2 (...) is mechanically coupled to the second axis. L1 Incident beam The beam of light reflected from L2 on the mirror V1 and V2 are control voltages used to operate the drive unit. f frequency f1 Target frequency of the first rotational oscillation f2 Target frequency of the second rotating oscillation Δf frequency difference f TH Minimum frequency interval θ1, i The actual amplitude of the first rotational oscillation of the first vibration axis A1 θ1, s The target amplitude of the first rotational oscillation of the first vibration axis A1 θ2, i The actual amplitude of the second rotational oscillation of the first vibration axis A2 θ2, s The target amplitude of the second rotational oscillation of the first vibration axis A2 Δθ amplitude difference Phase Δ Phase difference t represents time.

Claims

1. A miniature scanner (100) for a projection system (200) for projecting Lisajous figures onto an observation field, wherein the miniature scanner (100) comprises: The deflection unit (101) has: a deflection element (130, 140) for deflecting an incident electromagnetic beam (L1); a support structure (125); and a spring device (135; 135a, b), wherein the deflection element (130, 140) is suspended from the support structure (125) without a gimbal by the spring device (135; 135a, b), such that the deflection element can simultaneously perform a first rotational oscillation about a first vibration axis (A1) and a second rotational oscillation about a second vibration axis (A2) orthogonal to the first vibration axis relative to the support structure (125), so as to induce a nonlinear Lissajous projection in the observation field (220) by deflecting the electromagnetic beam (L1) incident on the deflection element (130, 140) during the simultaneous oscillation; as well as A control device (195) is configured to manipulate a drive device (105) for driving the deflection unit (101) such that the corresponding driving effect (F1; F2) of at least one oscillation of the deflection elements (130, 140) can be set individually. The spring devices (135; 135a, b) are further configured to modulate the amplitude-related mutual coupling (K1; K2) between the oscillations; and The control device (195) is configured to, based on at least one detected state variable (θ) of the first rotational oscillation... 1,i f 1,i , 1,i The drive device (105) is manipulated to influence at least one state variable (θ) of the second rotational oscillation. 2,i f 2,i , 2,i This produces a driving effect (F2) on the second rotational oscillation, such that the driving effect (F2) cancels out the corresponding instantaneous oscillation frequencies (f) of the first and second rotational oscillations. 1,i f 2,i The interval between ) is lower than the predetermined minimum frequency interval (f TH ).

2. The micro scanner (100) according to claim 1, wherein, The control device (195) is further configured to, based on at least one detected state variable (θ) of the second rotational oscillation... 2,i f 2,i , 2,i The drive device (105) is manipulated to influence at least one state variable (θ) of the first rotational oscillation. 1,i f 1,i , 1,i This generates a driving effect (F1) on the first rotational oscillation, which cancels out the corresponding instantaneous oscillation frequencies (f) of the first and second rotational oscillations. 1,i f 2,i The interval between ) is lower than the predetermined minimum frequency interval (f TH ).

3. The micro scanner (100) according to claim 1, wherein, The control device (195) is configured to operate independently of the state variable (θ) of the second rotational oscillation. 2,i f 2,i , 2,i The drive device (105) is manipulated to influence at least one state variable (θ) of the first rotational oscillation. 1,i f 1,i , 1,i This generates a driving effect on the first rotational oscillation.

4. The micro scanner (100) according to claim 3, wherein, At least one state variable of each oscillation is determined by its amplitude (θ). 1,i ;θ 2,i ), frequency (f) 1,i f 2,i ) or phase ( 1,i , 2,i It can be determined by ( ), or by at least one of these variables.

5. The micro scanner (100) according to any one of claims 1 to 4, wherein, The control device (195) is configured to, in a regulatory sense, perform manipulation of the drive device (105) based on at least one repeatedly detected regulation variable to generate a corresponding driving effect on at least one thereby driven oscillation, the regulation variable being the state variable (θ) of the corresponding other oscillation. 1,i f 1,i , 1,i ;θ 2,i f 2,i , 2,i (or determined based on it.) 6. The micro scanner (100) according to claim 5, wherein, If the adjustment variable used to drive the control of the oscillation being driven is defined as the frequency (f) of the corresponding other oscillation. 1,i ;f 2,i ) or phase ( 1,i ; 2,i ), or, based on the determination of at least one of these state variables, the detection of the regulating variable always occurs at the same amplitude (θ) of the corresponding other oscillation. 1,i ;θ 2,i ) place.

7. The micro scanner (100) according to claim 5, wherein, The control device (195) is configured to, in the sense of regulation, perform operations based on at least one repeatedly detected adjustment variable, whether it is the first rotational oscillation or the second rotational oscillation, the adjustment variable being the state variable (θ) of the corresponding other oscillation. 1,i ;θ 2,i Or determine it based on it; The corresponding adjustments for the first rotational oscillation and the second rotational oscillation are designed to be dynamically configured with respect to the slope and adjustment speed of the corresponding other adjustment.

8. The micro scanner (100) according to claim 6, wherein, The control device (195) is configured to, in the sense of regulation, perform operations based on at least one repeatedly detected adjustment variable, whether it is the first rotational oscillation or the second rotational oscillation, the adjustment variable being the state variable (θ) of the corresponding other oscillation. 1,i ;θ 2,i Or determine it based on it; The corresponding adjustments for the first rotational oscillation and the second rotational oscillation are designed to be dynamically configured with respect to the slope and adjustment speed of the corresponding other adjustment.

9. The micro scanner (100) according to any one of claims 1 to 4, wherein, The control device (195) is configured to, in the sense of no feedback control, based on at least one detected corresponding oscillating state variable (θ) of another oscillation. 1,i ;θ 2,i The drive device (105) is manipulated to generate a corresponding drive effect (F1, F2) on the oscillations thereby driven.

10. The micro scanner (100) according to claim 9, wherein, The control device (195) is configured to manipulate the drive device (105) to produce a corresponding driving effect on the corresponding oscillations driven thereby, such that the drive device (105) enables the amplitude (θ) of each of these oscillations to be adjusted. 1,i ;θ 2,i The frequency increases gradually with respect to the first and second rotational oscillations.

11. The micro scanner (100) according to any one of claims 1 to 4, wherein, The control device (195) is configured to manipulate the drive device (105) such that the corresponding frequency of at least one oscillation is maintained at a predetermined current resonant frequency (f) around the oscillation. 1R f 2R Within the resonant range defined by ).

12. The micro scanner (100) according to claim 11, wherein, The resonant range of the resonant frequency is defined by the frequency value f of the resonant frequency. R The value f R It is defined as ± 70%.

13. The micro scanner (100) according to claim 11, wherein, The resonant range of the resonant frequency is defined by the frequency value f of the resonant frequency. R The value f R It is defined as ± 40%.

14. The micro scanner (100) according to claim 11, wherein, The resonant range of the resonant frequency is defined by the frequency value f of the resonant frequency. R The value f R It is defined as ± 20%.

15. The micro scanner (100) according to claim 11, wherein, The resonant range of the resonant frequency is defined by the frequency value f of the resonant frequency. R The value f R It is defined as ± 10%.

16. The micro scanner (100) according to any one of claims 1 to 4, wherein, The minimum frequency interval (f) TH The parameter is set to a constant value.

17. The micro scanner (100) according to any one of claims 1 to 4, wherein, The minimum frequency interval is set as a variable parameter, which depends on the corresponding current amplitude (θ) of the first or second rotational oscillation. 1,i ;θ 2,i ) or the corresponding current amplitude (θ) of these two oscillations 1,i ;θ 2,i ).

18. The micro scanner (100) according to any one of claims 1 to 4, wherein, The spring device (135; 135a, b) is designed such that the strength of the amplitude-dependent mutual coupling (K1; K2) between the first rotational oscillation and the second rotational oscillation varies with the amplitude (θ) of at least one of the two oscillations. 1,i ;θ 2,i It increases steadily with the increase of ).

19. The micro scanner (100) according to any one of claims 1 to 4, wherein, The micro-scanner (100) is designed as a dual-axis micro-scanner, wherein the deflection unit (101) has deflection elements (130, 140) which are suspended from a frame (125) by three rotationally symmetrically arranged spring elements (135), which serve as a support and surround the deflection elements.

20. The micro scanner (100) according to any one of claims 1 to 4, wherein the micro scanner is designed as a biaxial, gimbal-free micro scanner (100), wherein: The deflection unit (101) has deflection elements (130, 140) which are securely suspended on opposite sides by bending springs (135a, 135b) from a frame (125) serving as a support; and Each of the bending springs (135a, 135b) has two arcuate segments that are connected to each other at their end faces and extend apart from each other in other respects, and extend around the deflection element (130, 140), wherein each bending spring (135a, 135b) has a segment adjacent to the deflection element (130, 140) connected to the deflection element (130, 140), and each bending spring (135a, 135b) has a segment adjacent to the frame (125) connected to the frame (125).

21. The micro scanner (100) according to any one of claims 1 to 4, wherein, The control device (195) is configured to individually adjust at least one corresponding state variable of the first rotational oscillation, the second rotational oscillation, or each of the two oscillations to a specific target value within the range of manipulating the drive device (105) to drive the deflection unit (101) in the sense of amplitude adaptation, frequency adaptation, or phase adaptation.

22. The micro scanner (100) according to any one of claims 1 to 4, wherein: The deflecting elements (130, 140) are suspended from the support structure (125) without universal joints by the spring devices (135; 135a, b), enabling them to simultaneously and additionally perform a third rotational oscillation relative to the support structure (125) about a third vibration axis orthogonal to the first and second vibration axes, respectively, so as to induce a nonlinear Lissajous projection in the observation field (220) by deflecting the electromagnetic beam (L1) incident on the deflecting elements (130, 140) during these three simultaneous oscillations, wherein the spring devices (135; 135a, b) are also designed to mediate the amplitude-related mutual coupling between the third rotational oscillation and the first or second rotational oscillation or both.

23. The micro scanner (100) according to claim 22, wherein, The control device (195) is further configured to, based on at least one detected state variable (θ) of the first or second rotational oscillation. 1,i ;θ 2,i The drive device (105) is manipulated to generate a driving effect on the third rotational oscillation by influencing at least one state variable of the third rotational oscillation, which on the one hand cancels out the corresponding instantaneous oscillation frequencies (f) of the first and second rotational oscillations. 1,i ;f 2,i The interval between ) is lower than the predetermined minimum frequency interval (f TH On the other hand, it also offsets the lower-than-predetermined minimum frequency interval between the corresponding instantaneous oscillation frequency of the third rotational oscillation.

24. The micro scanner (100) according to any one of claims 1 to 4 further includes a housing, wherein at least the deflection element (130, 140) and the spring device (135; 135a, b) are hermetically sealed through the housing such that the deflection element (130, 140) is vibratingly suspended on the spring device within the housing to achieve oscillation; The enclosure has an enclosure section (145) that bridges the deflection elements (130, 140), through which the beam to be deflected illuminates the spatial region enclosed by the enclosure, and after the beam has been deflected at the deflection elements (130, 140), it is emitted again from the spatial region.

25. The micro scanner (100) according to claim 24, wherein, The enclosure section (145) has a dome-shaped, planar, or U-shaped design with a rectangular cross-section.

26. A projection system (200) for projecting Lisajous figures onto an observation field (220), wherein, The projection system (200) includes a micro scanner (100) according to any one of claims 1-25.

27. The projection system (200) according to claim 26, wherein, The control device is also configured to provide at least one modulation signal to the beam source according to the modulated incident electromagnetic beam (L1).

Images