Actuator Sensor System and Fast Steering Mirror

Abstract

The actuator-sensor system for controlling the diversion or deflection of electromagnetic radiation in at least one axis (9) comprises an actuator (5) for mechanically moving a deflection element (10) and a measurement element (2) for sensing the position of the deflection element (10), characterized in that the measurement element (2) consists of a flat substrate (3) provided with at least one sensor element (4).Furthermore, the present invention relates to a high speed steering mirror.

Description

[Technical Field]

[0001] The present invention relates to an actuator-sensor system for controlling the redirection or deflection of electromagnetic radiation in at least one axis, comprising an actuator for mechanically moving a deflection element and a measurement element for sensing the position of the deflection element. Furthermore, the present invention relates to a fast steering mirror (FSM). [Background technology]

[0002] Actuator sensor systems are used in many applications where controlled movement must be performed. Ranging from single axis movement to two and multi-axis movement, there are many actuators that are controlled by sensors to produce controlled and coordinated movement in one or more directions or axes. The sensor signal serves as feedback regarding the current position of the actuator. This position is compared to a setpoint position in the controller and a control signal is generated based on this to control the actuator.

[0003] In most cases, two sensors per axis (sensor A-sensor B) in a differential configuration are used as position detection sensors. Sensors A and B face each other with a rotatable base plate between them, so that the sensitivity is approximately doubled using a substantially linear output signal. In this case, known sensors are inductive or eddy current sensors, capacitive sensors or optical sensors.

[0004] Conventional sensors typically have a bulky design, which is due to the sensor element itself, the housing, the connector (cable or plug), or a combination thereof. However, for technical and cost reasons, a compact design is often desirable. This is the case for applications in the aerospace industry, for example, where low weight or particularly compact designs are required. Since a single axis actuator sensor system (in a differential configuration) requires two sensors and a dual axis actuator sensor system requires four sensors, the size of the sensors has a decisive impact on the overall size of the actuator sensor system.

[0005] Differential configurations have a mechanical center point (zero point) and an electrical center point (zero point), depending on the design. The prior art is to match these two midpoints as precisely as possible through a mechanical adjustment process (by adjusting the individual sensors). This is time consuming to implement and even if successful leaves residual errors. Also, a mechanical base plate is required for at least one sensor, and typically both sensors, to allow adjustment and subsequent fixation of the sensor. Such devices are expensive and require a large amount of installation space. A separate electrical connector must also be made for each sensor. Calibration of the differential configuration of the sensor is only possible after adjustment and fixation.

[0006] In a differential configuration of sensors, it is advantageous in terms of linearity and temperature behavior if the two sensors of a sensor pair have as identical a behavior as possible relative to each other.

[0007] To this end, sensors based on wound coils (eg, induction or eddy current sensors) undergo a downstream matching process to identify sensors of the same type. Typically, this is done at two distances within the measurement range. However, this involves an additional step, which results in higher manufacturing costs, especially since sensors that do not find a "partner" will need to be measured again at the next match. Also, the matching process is not perfect because some deviation between the initial measured values of the two distances must be allowed so that a significant number of pairs can be found. Also, there is generally no matching regarding the temperature behavior of the individual sensors, as this would be too complicated and expensive.

[0008] Conductor connectors are required to connect the sensors to downstream evaluation circuits. Typically, this is accomplished using shielded coaxial cables or flexible printed circuit boards.

[0009] An additional manufacturing step is required to make each sensor accessible. This makes manufacturing more expensive and reduces reliability, especially since each additional connector is also a potential weak point (break or short). The problem is even worse when external influences, such as temperature fluctuations, shocks, vibrations, etc., are present.

[0010] Actuator sensor systems (so-called fast steering mirrors - FSMs) are becoming commonplace, where optical signals need to be redirected or deflected in a targeted manner. In addition to current actuator sensor systems, high speed steering mirrors also contain deflecting elements that can be used to redirect or deflect optical signals. In semiconductor manufacturing, for example, high speed steering mirrors guide the laser beam that singulates the dies on a wafer. Fast steering mirrors are also used in military applications for fast target tracking or as image stabilizers. High-speed steering mirrors are also often used in optical scanners (3D), 3D printing or large screen projection.

[0011] A fast steering mirror typically consists of a reflective surface (mirror), a movable element (about one or two axes) that also serves as a base for the mirror, a drive unit (electromagnet, actuator) that positions the mirror, and a sensor that records the current position of the mirror base and thus detects the reflective surface. The FSM is operated as a controlled system by comparing the current position to a desired setpoint position and transmitting corresponding control signals to the drive unit. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention is therefore based on the object of eliminating as far as possible the problems occurring in the prior art. Additionally, the actuator sensor system of the present invention and the fast steering mirror of the present invention should be different from competing products. [Means for solving the problem]

[0013] This object is achieved by the features of claim 1. According to this, the known actuator-sensor system is characterized in that the measuring element consists of a flat substrate which is provided with at least one sensor element.

[0014] With regard to the fast steering mirror according to the invention, this object is achieved by the features of independent claim 14, according to which the fast steering mirror comprises an actuator sensor system according to the invention.

[0015] According to the present invention, it is recognized that if the distributed sensors are replaced by a measuring element consisting of a flat substrate containing one or more sensor elements, the design of the actuator-sensor system can be significantly reduced and its manufacture and function can be significantly improved.

[0016] The measuring element is arranged in the actuator sensor system so as to be able to detect the position of the movable element. The movable element is moved, for example tilted about an axis, using one or more actuators. The base plate is connected to the movable element and includes a deflecting element suitable for deflecting optical signals (or, in general, electromagnetic radiation). The deflecting element may be an optical element, such as a mirror, a prism, a lens, a diffraction grating, or the like.

[0017] The bed is provided via a movable element such that movement can occur in one or more directions or about one or more axes. For example, line or point bearings can be used to tilt the movable element. Alternatively, fixed bearings can be used, for example in the form of bending elements.

[0018] It is particularly advantageous if the deflection element is arranged on the movable element (e.g. as a coating) or is designed as part of the movable element, and if the movable element has a waistline and the measuring element is arranged within this waistline. In the present invention, the term "waistline" refers to the radial constriction or taper of a movable element. Above and below the waistline, the movable element has a cross section that is larger than the waistline. The deflection element may be attached above the waistline. The magnet (or magnetic material) for the actuator can be attached below the waistline and is used to move the moving element. This results in the actuator sensor system having a very compact and flat design. Due to the arrangement of the measuring element within the waistline, the measuring element does not protrude radially or only protrudes slightly beyond the movable element. The flat design of the measuring element allows the height of the moving element, which comprises the waistline, to be kept very low.

[0019] It is particularly advantageous if the movable element is formed from two parts which are rigidly connected to each other. The upper portion can support a biasing element, and the lower portion can support one or more magnets (or magnetic material) for one or more actuators. The movable element is movably mounted via the bending element. The bending elements can be attached to either the top or bottom or a combination of both.

[0020] The moving elements may be formed from lathed parts which are easy to manufacture. In this case, the measuring element is advantageously designed as a ring-shaped substrate, which is inserted between the upper and lower parts of the movable element during assembly. The measuring element can be rigidly connected to the housing or to a support structure of the sensor element of the actuator. The sensor elements may be arranged on the measuring element such that one sensor element each is located above an actuator. Alternatively, on the other hand, the sensor element may be offset relative to the actuator by, for example, 45°. This reduces the influence of the actuator. On the other hand, a differential configuration with only three sensors at an angle of, for example, 120° is also conceivable. It is particularly advantageous if the moving element is made of metal. As a result, the measuring element is shielded from the actuator from below by its lower part, reducing the influence of the actuator's interference with the measuring element. Regardless of its exact design, the movable element preferably serves as a holder for the deflection element and can represent a target for the sensor element. It is also conceivable to mount the magnet of the actuator there.

[0021] The measuring element may be arranged so that the sensor element is located next to the actuator. This allows for a flat design. On the other hand, the measuring element may be arranged so that the sensor element is located in an air gap formed in the actuator between the actuator and the moving element, for example between a coil and a magnet (or magnetic material).

[0022] The measuring element is designed as a flat, planar substrate and may be made, for example, from ceramic or printed circuit board material. In its simplest form, the substrate is designed as a single layer, but may also consist of multiple layers.

[0023] The sensor element may be disposed on or within the substrate. For example, the sensor elements of a capacitive sensor may be disposed on the surface of a substrate by forming planar electrodes on the surface, as is well known. The sensor elements of an inductive or eddy current sensor may be arranged either as a single layer coil on the substrate or as a multi-layer coil within a layer of the substrate.

[0024] It is particularly advantageous if the substrate contains a plurality of sensor elements. Therefore, a differential configuration of the sensor can be achieved in a simple manner, for example by arranging two sensor elements next to each other (or opposite each other) on or in the substrate so that the measurement object is detected by both sensor elements. The differential configuration means that during movement one sensor element detects the approach of a measurement object and the other sensor element detects the distance to the measurement object. The difference between the two signals is often linear without the need for additional circuitry. This also eliminates interference that affects both sensor elements equally, such as temperature effects, electromagnetic interference, etc.

[0025] In another embodiment, multiple sensor elements may be used to simultaneously detect movement in multiple directions, for example tilt movement about two axes.

[0026] It is particularly advantageous if a differential configuration is selected for each direction of movement, with both sensor elements detecting one direction of movement independently of the other. Such an actuator-sensor system can, for example, move a mirror in two axes spaced at 90° angles, independently of each other, so as to deflect a light beam into any solid angle. The solid angle is defined by the tilt angle about each axis. For two-axis movement, four sensor elements are not absolutely required; three sensors arranged at approximately 120° to each other are sufficient. In this case, differential evaluation requires more complex, but well-known, mathematical calculations.

[0027] Ideally, the measuring element requires only one connector for contacting the sensor element. This may be a plug located on the substrate. The conductor tracks may be integrated into the substrate, resulting in a very thin electrical connector that can be freely installed where space is limited.

[0028] The electronic components for the electronic circuitry may already be disposed on the substrate. In the simplest case, a preamplifier can be implemented in the sensor element for early conditioning and amplification of the signal. As a result, there is little or no interference affecting the lines. It is also conceivable to house the entire evaluation electronics on the substrate. Furthermore, even the control electronics for the actuators can be integrated.

[0029] Additionally, one or more temperature sensors may be disposed on the substrate. In this way, temperature can be measured within the actuator sensor system and the effects of temperature on the sensor measurements can be compensated for, if necessary.

[0030] When the sensor elements are integrated into the substrate during the manufacturing process, the sensor elements are rigidly and precisely positioned relative to each other.

[0031] For example, if the sensor elements are fabricated from copper layers using conventional printed circuit board techniques, the geometric dimensions of the coils or electrodes will all be approximately the same due to the manufacturing process.

[0032] When manufacturing the ceramic substrate, the conductor paste used in the process of "printing" the conductor structures on the ceramic substrate is also the same for all sensors.

[0033] In both cases, all sensor elements on the substrate have undergone the same manufacturing steps, so the sensors behave approximately identically relative to each other. The electrical values (eg ohmic resistance, inductance, capacitance, impedance, etc.) and temperature behavior of the sensor elements are also substantially identical. In this way, subsequent matching or selection can be omitted entirely.

[0034] Now, there are various options for developing the invention. For this purpose, reference is made on the one hand to the claims dependent on claim 1 and on the other hand to the following description of an embodiment of the invention based on the drawings. The invention will be described with reference to the drawings, together with further developments thereof. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a schematic diagram of an embodiment of an FSM according to the present invention comprising a measurement element in the form of a flat substrate; [Figure 2] 1 is a schematic diagram of a measuring element in the form of a flat substrate having two sensor elements in the form of coils; [Figure 3] 1 is a schematic diagram of a measuring element in the form of a flat substrate with two sensor elements designed as electrodes of a capacitive sensor; [Figure 4] 1 is a schematic diagram of a measuring element having four sensor elements in the form of coils; [Figure 5] 1 is a schematic diagram of a measuring element having three sensor elements for detecting movement about two axes; [Figure 6] 1A and 1B are schematic diagrams of two embodiments of a measuring element each having four sensor elements in a differential configuration. [Figure 7] 1 is a schematic diagram of a measuring element having an additional temperature sensor in the form of a serpentine conductor loop; [Figure 8] 1 is a schematic diagram of a measuring element having electronic components in the form of an electronic circuit; [Figure 9] 1 is a schematic diagram of an embodiment of a fast steering mirror for deflecting an optical signal in two axes with a measuring element having four sensor elements. [Figure 10] 1 is a cross-sectional view of an embodiment of an actuator sensor system. [Figure 11] FIG. 11 is an exploded view of the actuator sensor system according to FIG. DETAILED DESCRIPTION OF THE INVENTION

[0036] FIG. 1 shows a fast steering mirror, or FSM for short, 1 , which is provided with a measurement element 2 in the form of a flat substrate 3 . The figure shows a differential configuration with two sensor elements 4, 4'. The fast steering mirror 1 comprises two actuators 5, 5' in the form of coils 6, 6' capable of moving a movable element 8 in an axis 9 via magnets 7, 7'. The deflection element 10, in this case in the form of a reflective coating, is attached to the movable element 8. The movable element 8 is movably mounted via a fixed bearing in the form of a bending beam 11.

[0037] FIG. 2 shows a measuring element 2 in the form of a flat substrate 3 carrying two sensor elements 4, 4' in the form of coils. The coils can be arranged either as a single layer coil on the substrate or as multiple layers within the layers of the substrate.

[0038] FIG. 3 shows a measuring element 2 in the form of a flat substrate 3 having two sensor elements 4, 4' formed as electrodes 12, 12' of a capacitive sensor.

[0039] FIG. 4 shows a measuring element 2 having a total of four sensor elements 4, 4', 4'', 4''' in the form of coils. The two sensor elements are arranged opposite each other so that movement can be measured about two axes (offset by 90° relative to each other). In the center of the measuring element there is a passage 13 through which a movable element can be placed centrally (not shown) which serves as a holder for the deflection element.

[0040] FIG. 5 shows a measuring element 2 having three sensor elements 4, 4', 4'' for detecting movements about two axes. The sensor elements are arranged at an angle of 120° to each other. To record movement in two axes, a mathematical function is required that does not consist solely of the difference between two sensor signals.

[0041] FIG. 6 shows two examples of measuring elements 2, 2', each of which has four sensor elements in a differential configuration and a central passage 13, 13'. The measuring elements 2, 2' have recesses 14, 14'. These serve to allow the actuator (coil or magnet) to be brought close to the movable element 8 in each case. This improves power flow and allows for a smaller design.

[0042] FIG. 7 shows a measuring element 2 with additional temperature sensors 15, 15', 15'', 15''' in the form of serpentine conductor loops. The ohmic resistance of the conductor loop can be used to measure the temperature.

[0043] FIG. 8 shows a measuring element 2 including an electronic component 16 in the form of an electronic circuit. This circuit can be used for signal processing or can already contain the entire evaluation circuit or can also contain the control electronics for the actuators. The circuitry is contacted via solder pads 17 . Alternatively, the conductors may already be integrated into the substrate (not shown).

[0044] Figure 9 shows a fast steering mirror 1 for redirecting optical signals in two axes, with a measuring element 2 having four sensor elements 4, 4' (only two are visible), a deflection element 10 as a flat mirror and four actuators 5, 5', 5'' (actuator 5''' is not visible as it is behind the three actuators). The two actuators cooperate to tilt a holder carrying a flat mirror about two axes. The measuring element has recesses 14, 14', 14'' (one not visible) through which the magnets 7, 7', 7'' (magnet 7''' is not visible as it is behind the three magnets) of the actuator are immersed in the coil.

[0045] 10 and 11 show different representations of the actuator sensor system. The movable element 8 has an upper part 18 and a lower part 19 . The upper and lower portions 18, 19 are rigidly connected to one another, for example by screwing, gluing or other suitable mechanical connection. The measuring element 2 is arranged at the waistline 20 of the movable element 8 and is connected to a housing 22 via a holding structure 21 . At the bottom 19 of the mobile element 8, the magnets 7, 7' of the actuators 5, 5' are arranged, with which the mobile element 8 can be tilted about an axis 9 (illustrated by the arrow 9). The tilting movement of the movable element 8 is effected via a fixed bearing 11 in the form of a bending beam. The sensor elements 4, 4' are arranged axially above the actuators 5, 5'. The lower part 19 of the movable element 8 shields the sensor elements 4, 4' from the actuators 5, 5'.

[0046] With regard to embodiments of the present invention, to avoid repetition, reference is made to the general part of this specification and the appended claims.

[0047] Finally, the embodiments of the present invention are provided merely to discuss the claimed features and are not intended to be limiting. [Explanation of symbols]

[0048] 1. High-speed steering mirror 2. Measurement elements 3. Flat substrate 4, 4', 4'', 4''' sensor element 5,5'···Actuator 6,6' coil 7,7',7'',7''' magnet 8. Moving elements 9 axes 10...Deflection element 11. Fixed support in the form of a curved beam 12,12'...electrode 13...Aisle section 14,14',14''...recess 15,15',15'',15'''' Temperature Sensor 16. Electronic Components 17. Soldering pad 18. Upper part (movable element) 19 Lower part (movable element) 20. Waistline 21...Holding structure part 22. Housing

Claims

1. 1. An actuator-sensor system for controlling redirection or deflection of electromagnetic radiation in at least one axis (9), comprising an actuator (5) for mechanically moving a deflection element (10) and a measurement element (2) for sensing the position of said deflection element (10), the deflection element (10) is arranged on or is provided as part of the movable element (8), The measuring element (2) is placed on the waistline (20) of the movable element (8), An actuator-sensor system, characterized in that the measuring element (2) consists of a flat substrate (3) provided with a sensor element (4).

2. 2. An actuator-sensor system according to claim 1, characterized in that the movable element (8) is made of two parts.

3. 3. An actuator-sensor system according to claim 1 or 2, characterized in that the substrate (3) comprises two or more sensor elements (4, 4') and is made of ceramic or printed circuit board material.

4. 4. An actuator-sensor system according to claim 3, characterized in that the substrate (3) is provided as a single layer or as a multi-layer consisting of two or more layers.

5. 5. An actuator-sensor system according to claim 1, wherein the sensor element (4) is provided either as a flat coil of an inductive or eddy current sensor or as an electrode of a capacitive sensor.

6. 6. The actuator-sensor system according to claim 1, wherein the sensor element (4) is formed on a surface of the substrate (3).

7. 7. An actuator sensor system according to claim 3, wherein at least two sensor elements (4, 4') are provided in a differential configuration or for recording at least two movements independently of each other.

8. The actuator sensor system according to any one of claims 1 to 7, characterized in that the substrate (3) is provided with electronic components or conductor connectors for controlling the sensor elements (4, 4', 4'', 4''').

9. the measuring element (2) comprises one connector for contacting the sensor element (4, 4', 4'', 4'''), 9. An actuator-sensor system according to claim 1, characterized in that the connector is a plug arranged on the substrate (3), or a soldering point (17) arranged on the substrate (3), or a conductor track integrated in the substrate (3).

10. 10. The actuator sensor system according to claim 1, wherein the measuring element (2) comprises four sensor elements (4, 4', 4'', 4''') rotated by 90° relative to each other.

11. Actuator sensor system according to any one of the preceding claims, characterized in that the measuring element (2) comprises an integrated temperature sensor (15).

12. A high speed steering mirror comprising an actuator sensor system according to any one of claims 1 to 11.

13. 13. The high-speed steering mirror according to claim 12, characterized in that the high-speed steering mirror comprises a deflecting element for redirecting or deflecting electromagnetic radiation, in particular optical signals, optical signals in the visible range, infrared signals, UV (ultraviolet) signals or EUV (extreme ultraviolet) range signals, images, laser beams, etc.

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