Measuring device and tilting mirror unit with such a measuring device

Abstract

The invention relates to a measuring device (1) with a stationary light source (2), a stationary receiver (3), a positionally or orientationally variable optical element (4), and a measuring object (5) having at least one degree of freedom, wherein the optical element is directly or indirectly connected to the measuring object and moves with it, and wherein the light source is arranged between the measuring object and the optical element and emits light in the direction towards the optical element and the receiver, and wherein, due to a movement of the measuring object and the analogous movement of the optical element, the amount of light passing through or being transmitted by the optical element and striking the receiver varies, so that a characteristic light intensity distribution results on the receiver depending on the position or orientation of the measuring object, and the receiver is configured toto generate at least two electrical signals from the light intensity distribution, with the help of which the position or the location of the object being measured can be measured.

Description

Background of the invention

[0001] The invention relates to a measuring device and a tilting mirror unit with such a measuring device.

[0002] In the applicant's existing measuring devices for detecting the tilt angle of a measured object, the measurement is often carried out using light beams from a light source that are emitted towards the measured object and reflected off a surface of the object, before falling onto a sensor. In applications that allow only very limited space for the measuring device (i.e., in cases of limited installation space), this results in a relatively small and, in certain cases, insufficient measuring range with regard to the tilt angle of the measured object.

[0003] German patent DE 10 2011 004 477 A1 describes a scanning mirror device that uses a non-contact optical sensing module to measure the rotational position of a microsystem scanning mirror. This eliminates inaccuracies of existing technologies, as it enables precise and continuous angle measurement without interrupting the scanning process. Object of the invention

[0004] It is an object of the invention to provide a measuring device which, with limited installation space or low space requirements, allows the highly accurate, reliable and efficient determination of a position or orientation of a measured object in at least one degree of freedom over a comparatively large measuring range. Inventive solution

[0005] The above problem can be solved, for example, with a measuring device comprising a light source, a receiver, an optical element, and a measurement object. While the light source and the receiver are fixed in position, the optical element is arranged to be movable and is directly or indirectly connected to the measurement object, which has at least one degree of freedom of movement, such that the optical element moves with the measurement object or follows its movement in an analogous manner. The light source emits light, either directly or indirectly by deflection or reflection, in the direction of the optical element.The receiver, and due to movement of the object being measured and the resulting analogous movement of the optical element, the amount of light passing through or being transmitted by the optical element and striking the receiver varies, so that a characteristic light intensity distribution results on the receiver depending on the position or orientation of the object being measured. The receiver is configured to generate at least two optical or electrical signals from the light intensity distribution, with which the position or orientation of the object being measured can be determined. With the measuring device according to the invention, it is possible in a comparatively simple manner to double the measuring range without increasing the installation space, given a specific size of the receiver, and this without utilizing the reflection of the light source from the object being measured.

[0006] According to a preferred embodiment, the object being measured has two translational degrees of freedom, two rotational degrees of freedom, or one translational and one rotational degree of freedom. Providing the appropriate degrees of freedom allows for targeted adaptation of the measuring device to the specific application. Alternatively, the measuring device can be designed such that the object being measured has only one degree of freedom, or it can have additional degrees of freedom, thus exceeding two in total. If the additional degrees of freedom are also to be measured, several such measuring devices must be connected to the object being measured, according to this embodiment.

[0007] According to another embodiment, the light source comprises an LED, a laser, or a fluorescent or phosphorescent element. These light source types are simple and readily available in a wide variety of forms. LEDs are particularly energy-efficient. When using a fluorescent or phosphorescent light source, the low coherence of the emitted light offers the advantage of avoiding diffraction effects, which can potentially impair the detection of shifts in the light intensity distribution at the receiver and / or reduce the linearity of the measuring device. Furthermore, LEDs and lasers are particularly suitable for applications requiring ambient light suppression through power modulation while simultaneously demanding fast response times or high detection bandwidths.

[0008] According to another embodiment, the light source emits collimated, focused, or divergent light, allowing it to be adapted to the specific application. If high sensitivity and a small measuring range are required, a focused light source is typically used, which is imaged through the optical element onto the receiver to achieve maximum change in the spatial distribution of light intensity on the sensor element. Such a configuration can result in increased nonlinearity of the measuring device, since light sources typically exhibit an angle-dependent, nonlinear emission characteristic.If, however, the application requires low nonlinearity of the measurement signals, a collimated or divergent light source can be used. This, combined with a suitable choice of optical element and sensor, allows the central and relatively constant portion of the emitted light intensity to be imaged, masked, or shaded onto the sensor element depending on its position. The choice of beam shaping is therefore always influenced by specific requirements and optimized for the particular application.

[0009] According to another embodiment, the optical element has diffractive or refractive properties. This allows the change in the light intensity distribution on the receiver due to the movement of the object being measured to be amplified or attenuated, thus increasing or decreasing the sensitivity of the measuring device to achieve optimal adaptation of the measuring device to the respective application. The light intensity can be adjusted, for example, by refractive optics (lenses) or diffractive optics (e.g., optical gratings, holographic gratings), with diffractive optics offering greater flexibility in beam shaping. However, diffractive beam shaping can have the disadvantage that, due to the nature of these optics, it leads to an increase in short-wavelength, local nonlinearity, which may then need to be compensated for by additional optical elements, such as diffusers.

[0010] According to another embodiment, the optical element comprises an aperture. In this case, the movement of the optical element together with the object being measured leads to a selective shading of the receiver. This position- or orientation-dependent selective shading of the receiver results in a shift or change in the light intensity distribution on the receiver, thus enabling the position or orientation of the optical element and therefore of the object being measured to be determined.

[0011] According to another embodiment, the receiver comprises lateral-effect diodes, quadrant photodiodes, or CCD or CMOS matrix sensors. Lateral-effect diodes and matrix sensors have the advantage that the intensity distribution of the light does not restrict the basic function, as long as the shape of the intensity distribution is preserved. Furthermore, larger measurement ranges can be achieved with these sensors for a given sensor size compared to quadrant diodes. The latter must receive a portion of the light intensity distribution in each quadrant to function correctly and be evaluated accurately. The advantage of quadrant diodes is their significantly larger signal bandwidth compared to lateral-effect diodes and matrix sensors.

[0012] According to another embodiment, the receiver has quadrant photodiodes with at least two photodiodes. If the quadrant photodiodes have three photodiodes, it is advantageous not to arrange them along a line. By determining the center of mass of the incident light, two linearly independent signals can be generated, which allow a measurement of the position of the incident light, imaged by the optical element moving with the object being measured, within the plane of the sensor, thus enabling a measurement of the object's position in two degrees of freedom.

[0013] According to another embodiment, the receiver has at least two optical fibers. If the receiver has three optical fibers, it is advantageous not to arrange them in a straight line and to connect each to a photoreceiver. The optical operating principle is the same as described above. The advantage is that optical fibers, compared to electronic components such as photodiodes, can be used in a wider range of environmental parameters. This can include environments with high temperatures or aggressive media.

[0014] According to another embodiment, the optical element is arranged between the light source and the receiver.

[0015] The invention further relates to a tilting mirror unit with at least one measuring device described above, wherein the object being measured comprises a mirror movable by at least one rotational degree of freedom and is driven by at least one drive unit. Here, either the mirror itself forms the object being measured, or the mirror is part of the object being measured and preferably arranged on it. The at least one drive unit acts directly or indirectly on the object being measured.

[0016] According to one embodiment, the drive unit of the tilting mirror unit has an electromagnetic drive, preferably formed by a coil and a permanent magnet. Such electromagnetic drives are also known as moving-coil drives. These have the property of generating a force when current flows through the coil, which can be used to move objects relative to each other. At the same time, these drives allow for a much larger range of motion compared to piezoelectric drives.

[0017] According to another embodiment, the drive unit of the tilting mirror unit has an electromechanical drive, preferably formed by a piezo actuator. This embodiment is particularly advantageous when very small ranges of motion with the highest precision are required. Furthermore, piezo actuators have the property of only requiring power when their position changes. In the static state, only a constant voltage is needed to define and maintain the position. It is also conceivable to use piezo actuators that are only partially polarized, so that by applying appropriate voltage pulses, slight reorientations of domains result, with corresponding remanent stretching or contraction of the piezo actuator. Thus, no energy input is required to maintain the position obtained and defined by the remanent stretching or contraction of the piezo actuator.

[0018] According to a further embodiment of the tilting mirror unit, it comprises at least one pair of drive units, wherein the at least one pair of drive units is configured to drive the object being measured in an antagonistic manner. Due to the antagonistic interaction of the two drive units of a corresponding drive unit pair, in which preferably one drive unit pushes against the object being measured and the other drive unit pulls on the object being measured, finely tuned control over movements or positions of the object being measured is possible. Since the drive units operate in opposite directions, they can make precise adjustments to achieve and maintain a desired position or movement.If, in addition, the center of gravity of the entire moving mass is brought into alignment with the axis of the tilting mirror unit's bearing, and the antagonistically acting drive units are simultaneously arranged so that they generate only tangential forces around the bearing axis, the bearing forces can theoretically be reduced to zero. This has a positive effect on their service life and minimizes undesirable resonances for dynamic applications. Furthermore, antagonistically acting drive units offer the advantage of redundancy, as the failure of one drive unit can be partially compensated for by the other. This increases the reliability of the tilting mirror unit. Moreover, in the case of electromagnetic drives, the antagonistic interaction of the drive units can lead to an increase in the overall drive's motor constant, resulting in more efficient energy use for a given dynamic range.Finally, a tilting mirror unit with antagonistically interacting drive units can dynamically respond to external influences by quickly adjusting the forces between the drive units.

[0019] According to a further embodiment, the tilting mirror unit has a device for acquiring and processing measurement or operating data relevant to the condition of the tilting mirror unit. This device is designed to continuously acquire and process the measurement or operating data during the operating time of the tilting mirror unit or its components or elements, and optionally to link this data together so that a picture of the tilting mirror unit's condition can be derived. In this way, an impending failure of components or elements of the tilting mirror unit can be detected during operation, ideally remotely, so that countermeasures can be taken at an early stage.

[0020] The term “essentially” in relation to a feature or value is understood herein to mean in particular that the feature contains a deviation of up to 20% and specifically up to 10% from the feature or its geometric property or value.

[0021] The term "one-piece" in relation to a part or component means that the part or component is manufactured as a single piece. The part or component may be made up of several pieces or parts that are connected, coupled, or joined together. The term "manufactured from a single piece" in this context means that the part or component is manufactured from a single, original workpiece.

[0022] The term "electromechanical" here refers to the property of an element or the material of that element, whereby it undergoes a mechanical deformation, such as a change in length, when subjected to an electrical voltage or current. In particular, an electromechanical material is understood to be a piezoelectric or an electrostrictive material.

[0023] Unless otherwise stated, the logical connective “or” in relation to two alternatives A and B is to be understood as a non-exclusive disjunction, i.e. A or B or both.

[0024] When the terms "at least" or "at least" are used herein with reference to the number of a feature, element, or part of the electromechanical spindle drive (hereinafter referred to as the initial feature), then—unless explicitly stated otherwise—the further features directly or indirectly related thereto (hereinafter referred to as reference features) shall be understood as follows: if the minimum number of the respective initial feature is present, the reference features apply to this minimum number; and if the number of the initial feature exceeds the minimum number, the reference features apply either only to the minimum number of the initial feature, or only to a portion of the number of the initial feature exceeding the minimum number, or to the entire number of the initial feature exceeding the minimum number, and thus to the entire number of the initial feature.For example, if a minimum number of two is mentioned with regard to a characteristic A (initial characteristic), then the further characteristics (reference characteristics) relating directly or indirectly to characteristic A either apply exactly to the minimum number of two, or - in the case of the existence of a number exceeding the minimum number of two with regard to characteristic A, for example four - the reference characteristics apply either only to the minimum number of two, or to a part or to the entirety of the number of characteristics A exceeding the minimum number of two.

[0025] The features described above and other features of the embodiments according to the invention are explained in the description of the figures and the claims. The individual features can be implemented either separately or in combination as embodiments of the invention. Furthermore, they can describe advantageous embodiments that are independently patentable and whose protection may be claimed only during or after the filing of the application. Brief description of the characters

[0026] The foregoing, as well as further advantageous features of the invention, are illustrated in the following detailed description of exemplary embodiments of the invention with reference to the accompanying schematic drawings. It shows / show Fig. 1: Schematic representation of an embodiment of a measuring device according to the invention Fig. 2: Schematic representation of an embodiment of a tilting mirror unit according to the invention Fig. 3a-3c: different schematic representations of a further embodiment of a tilting mirror unit according to the invention Detailed description of embodiments according to the invention

[0027] In the exemplary embodiments or variants described below, functionally or structurally similar elements are, as far as possible, provided with the same or similar reference numerals. Therefore, to understand the features of the individual elements of a particular exemplary embodiment, reference should be made to the description of other exemplary embodiments or to the general description of the invention.

[0028] Fig. Figure 1 shows a possible embodiment of a measuring device 1 according to the invention in a schematic representation. This device comprises a stationary, i.e., fixedly and immovably arranged, light source 2 in the form of an LED and a receiver or sensor 3 in the form of a quadrant photodiode for the diverging light rays emitted directly from the light source 2 towards the receiver 3. An optical element 4 in the form of a shutter with an aperture 42 is arranged between the light source 2 and the receiver 3, and spaced apart from each of them. The optical element 4 is rigidly connected to a measuring object 5 via a connecting device 6, and spaced apart from it. The light source 2 is arranged between the measuring object 5 and the optical element 4, and is spaced apart from both the measuring object 5 and the optical element 4.

[0029] In this embodiment, the measuring object 5 is arranged so that it can be moved along two mutually perpendicular translation axes. The translation directions along one of the translation axes are in Fig. 1 is marked with a corresponding arrow, while the translation directions along the other translation axis are directed into or out of the plane of the leaf.

[0030] The measuring device 1 according to Fig. Optical element 4 is configured to determine the position of the object 5 with respect to the respective translation axis. Due to the fixed or rigid connection of optical element 4 to the object 5, optical element 4 performs movements analogous to the movements of the object 5. Thus, optical element 4 is movable relative to the stationary components light source 2 and receiver 3. This results in the aperture 42 of optical element 4 being moved or shifted analogously to the movement of the object 5 relative to the light source 2 or receiver 3. Consequently, depending on the position of optical element 4 or its aperture 42, a corresponding shading of the receiver 3 occurs, i.e., relative to the... Fig. In the basic or neutral position of the optical element 4 shown in Figure 1, correspondingly fewer light rays emitted by the light source 2 reach the receiver 3, or a changed light intensity distribution on the receiver 3 results. At least two electrical signals can be generated from the light intensity distribution, with the help of which the position of the object being measured along the two translation axes can be measured.

[0031] Fig. Figure 2 shows a tilting mirror unit 10 with a measuring device 1 according to Fig. 1. In the following, only the differences between the tilting mirror unit 10 and the measuring device 1 will be discussed.

[0032] The object being measured 5 has a mirror element 52 on its surface facing away from the light source 2, which is fixedly arranged on the object being measured. A total of four drive units 7, each in the form of a voice coil drive, are attached to the opposite surface of the object being measured 5, of which in Fig. 2, however, only three are recognizable. The drive units 7 are arranged along two intersecting axes to enable tilting movements of the measured object around two rotational or tilting axes that are also perpendicular to each other. The corresponding tilting movements are shown in Fig. 2 characterized by arrows.

[0033] The foregoing description of exemplary embodiments is to be understood as illustrative. The disclosure thereby enables the person skilled in the art, on the one hand, to understand the present invention and its associated advantages, and, on the other hand, also includes, in the understanding of the person skilled in the art, obvious modifications and alterations of the described structures and methods. Therefore, all such modifications and alterations, insofar as they fall within the scope of the invention as defined in the appended claims, as well as equivalents, are to be covered by the protection of the claims.

[0034] Fig. Figure 3 shows in illustrations a) to c) a tilting mirror unit 10, which has a total of three measuring devices 1, which are provided on three side regions of the object 5 that are arranged at essentially 120° intervals with respect to a circumference, as is best illustrated in Fig. 3a), which shows a top view of the tilting mirror unit. The tilting mirror unit 10 has a total of three degrees of freedom, namely two rotational degrees of freedom and one translational degree of freedom, whereby the translational degree of freedom describes movements of the measured object into or out of the plane of the drawing with respect to Fig. 3a) is permitted, while the two rotational degrees of freedom allow rotational or tilting movements of the measured object around two rotational axes lying in the plane of the drawing, but not shown. For the sake of clarity, the following were used in the Fig. 3a) to c) the drive units for generating the movements of the tilting mirror unit around or along the aforementioned three degrees of freedom have been omitted.

[0035] As shown in the section view along section BB in Fig. As can be seen in section 3c), each of the three measuring devices includes a receiver in the form of a four-quadrant electrode, although it is also conceivable to use a two-quadrant electrode for the receiver. Fig. 3b) and Fig. 3c) further indicates that the optical element 4 - in contrast to the embodiments according to Fig. 1 and Fig. 2 - is formed integrally or in one piece with the object being measured 5, whereby it is also conceivable to form the optical element 4 separately and to arrange or attach it to the object being measured 5. This differs equally from the embodiment according to the Fig. 1 and Fig. 2 is the orientation of the measuring device 1 or its components: while in the embodiments according to Fig. 1 and Fig. 2 the components light source 2, optical element 4 and receiver 3 are arranged above or below each other in a perpendicular orientation, these are in the embodiment according to Fig. 3 arranged side by side or one behind the other in a horizontal orientation.

[0036] Other embodiments of the tilting mirror unit are also conceivable, such as those that have two or more than three measuring devices, depending on the application and corresponding requirements. Reference symbol list 1 measuring device 2 light sources 3 recipients 4 optical element 5. Measuring object 6 Connecting device 7 Drive unit 10 Tilting mirror unit 21 Light beam (of light source 2) 42 Aperture (of optical element 4) 52 Mirror element (of the measuring object 5)

Claims

Measuring device (1), comprising: a stationary light source (2); a stationary receiver (3); a positionally or directionally variable optical element (4);and a measuring object (5) having at least one degree of freedom of movement, wherein the optical element is directly or indirectly connected to and moves with the measuring object, and wherein the light source is arranged between the measuring object and the optical element and emits light directly or indirectly towards the optical element and the receiver, and, due to a movement of the measuring object and the analogous movement of the optical element, the amount of light passing through or being transmitted by the optical element and striking the receiver varies, so that, depending on the position or orientation of the measuring object, a characteristic light intensity distribution results on the receiver, and the receiver is configured to generate at least two electrical signals from the light intensity distribution, with the aid of which the position or orientation of the measuring object can be measured. Measuring device according to claim 1, characterized in that the object being measured has two translational degrees of freedom or two rotational degrees of freedom or one translational and one rotational degree of freedom. Measuring device according to claim 1 or 2, characterized in that the light source comprises an LED or a laser or a fluorescent or a phosphorescent element. Measuring device according to claim 3, characterized in that the light source is configured to emit collimated or focused or divergent light. Measuring device according to one of the preceding claims, characterized in that the optical element has diffractive or refractive properties. Measuring device according to claim 5, characterized in that the optical element comprises an aperture. Measuring device according to one of the preceding claims, characterized in that the receiver comprises lateral effect diodes or quadrant photodiodes or CCD or CMOS matrix sensors. Measuring device according to claim 7, characterized in that the receiver has quadrant photodiodes with at least two photodiodes. Measuring device according to one of claims 1 to 6, characterized in that the receiver has at least two optical fibers, each of which is connected to a photoreceiver. Tilting mirror unit (10) with at least one measuring device according to one of the preceding claims, wherein the object being measured comprises a mirror (52) movable by at least one rotational degree of freedom and is driven by at least one drive unit (7). Tilting mirror unit according to claim 10, characterized in that the drive unit has an electromagnetic drive, preferably formed by a coil and a permanent magnet. Tilting mirror unit according to claim 10, characterized in that the drive unit has an electromechanical drive, preferably formed by a piezo actuator. Tilting mirror unit according to one of the preceding claims 10 to 12, characterized in that it comprises at least one pair of drive units, and the at least one pair of drive units is configured to drive the measuring object in an antagonistic manner. Tilting mirror unit according to one of the preceding claims 10 to 13, wherein this unit has a device for acquiring and processing measurement or operating data relevant to the state of the tilting mirror unit, which is designed to acquire and process the measurement or operating data during the operating time of the tilting mirror unit and optionally to link them together, so that a picture of the state of the tilting mirror unit can be derived from it.

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