Rotary adjuster for a structure, especially with an optical element

Abstract

Rotary adjuster (1) for a structure, in particular an optical element (3), preferably a grating and / or mirror with - at least one rotary table with at least one turntable - a drive connected to the rotary table, preferably comprising at least one motor and one gearbox and / or one motor-gearbox combination and one rotary mechanism where The rotary table includes an angle measuring system for determining the angular position directly on the turntable, wherein the angle measuring system is preferably an absolute measuring system.

Description

[0001] The invention relates to a rotary adjuster for a structure, in particular an optical structure, in particular comprising an optical element preferably in the form of a grating and / or a mirror.

[0002] In particular, the rotary adjusters according to the invention are suitable for use in spectrometers or spectrographs, preferably in spectrometers with one or more grating elements. Applications of the invention are also possible in the broader field of optical instruments, such as microscopes or devices for adjusting a mirror.

[0003] When used in an optical setup, such as a microscope or, in particular, a spectrometer, where high spectral resolution is required, precise positioning of the optical elements, such as the spectrometer's mirrors or gratings, is essential. For the accuracy of the spectral calibration of a spectrometer, for example, it is crucial that the rotation angle of the optical component, such as the optical grating, relative to the light incident on the component, preferably the grating, is set and maintained precisely and reproducibly.

[0004] In the prior art, rotary actuators are typically driven by a stepper motor via a worm gear and bellows. The rotation angle of the rotary table, which comprises a rotating disk and is driven by the rotary actuator, is indirectly specified by moving the stepper motor by a known number of microsteps. Thus, the rotation of the rotary table is indirectly controlled via the reduction mechanism of the rotary actuator. The microsteps are counted relative to a reference position attached to the rotary actuator, for example, via a mechanical limit switch or a photoelectric sensor. Generally, such simple setups for detecting the reference position suffer from poor resolution, which is further exacerbated in compact rotary tables with rotating disks, as small angular changes result in only minute movements of the rotary table and disks.For high resolutions in the arcsecond range, additional information must therefore either be provided by further sensors directly on the driving motor shaft, and thus before the mechanically reduced movement, or by extremely high-resolution and therefore more complex reference sensors. "Directly" in this case means that the other sensors are mounted directly on the motor's drive shaft and therefore detect the motor's unreduced movement. This complicates the indirect, precise control of the turntable's angular position that can be achieved. Furthermore, after commissioning the system, the reference position must first be reached, and the system initialized. System initialization is necessary after the spectrometer is switched on because a reference point is required to count the steps. The reference point is the position of the light barrier.Therefore, after each time the system is switched on, the position of the light barrier must be found as a reference position.

[0005] Despite reduction ratios of 100:1 to 500:1, and especially 100:1 to 1000:1, resulting in 1 to 5 million stepper motor microsteps per rotary table revolution, such rotary actuators, according to the state of the art (for example, the OWIS DV65-D37, the Micos ADT-65, or the Physik Instrumente DT-80), exhibit an accuracy of significantly less than one arcsecond. While it is possible to increase the mechanical preload of the components used in the reduction mechanism to minimize backlash, sufficient smoothness of movement must also be ensured to prevent potential step losses during the rotary actuator's operation.Overly stiff gearboxes require powerful, large motors, which in turn introduce significant heat and mechanical stress into the system during operation, causing drift and relaxation processes and also preventing a compact design. Therefore, adjusting the preload is difficult and time-consuming. Generally, with rotary adjusters, according to the state of the art, by always approaching the target position from the same direction, the residual angular error can be further minimized to a sinusoidal error of approximately 20-30 arcseconds, which is linked to the motor revolution. This is primarily due to the worm drive, which, according to the state of the art, always reaches the target position from the same direction to compensate for the remaining gear backlash in the rotary adjusters.According to the state of the art, to compensate for this mechanical error, it is necessary to measure this residual error during the calibration of the rotary actuator and to fit the measurement data with a mathematical model. This model is then used to approach the desired target position with higher accuracy. For a worm gear, a periodic error occurs with each motor revolution. In a model, a sine wave can be assumed for this error component, and the result of this calibration measurement can be fitted with a sine signal to subtract this systematic error.

[0006] A disadvantage of the rotary adjusters and the prior art method for their precise positioning was the relatively high adjustment and assembly effort required for the numerous and varied components. Since the angular position of the rotary adjuster is only indirectly specified via the microstep position of the stepper motor, mechanical play, in particular, negatively impacts the angular accuracy. Furthermore, despite the extensive adjustment and assembly work, the required accuracy was often not achieved, necessitating frequent recalibration.

[0007] US Patent 5,096,295 B1 discloses a scanning monochromator that uses a pulse-driven microstepping motor to drive a spectral dispersion element via a harmonic drive with a reduction gear. The motor is directly connected to the input of the reduction gear, and the output of the reduction gear drive directly drives the spectral dispersion element. According to US Patent 5,096,295 B1, selecting a motor with a high step count per revolution and a harmonic drive with a high reduction ratio provides a resolution of 5 million pulsed steps per single revolution of the output of the reduction gear drive. This translates into more than 600,000 incremental angular displacement steps over a usable 45° range of dispersion element rotation.

[0008] US 9,551,612 B2 describes a monochromator comprising a light source and a diffraction grating. By using a diffraction grating with many different dispersive surfaces, measurements can be taken with relatively high precision and quality over a broader spectral range. According to another aspect of US 9,551,612 B2, the processing circuit control operates a sample drive motor to vary the angle of incidence of the dispersed wavelengths onto a sample for evaluation.

[0009] Renishaw PIC, New Mills, Wolton-under Edge, Gloucestershire, UK, unveils a rotary table with Renishaw Resolute absolute rotary encoders that can be used in machine tools, allowing machine axes to be resumed after tool changes and setup for reduced production times.

[0010] Furthermore, Renishaw PIC reveals a high-precision RESA and REXA angle measurement system.

[0011] It is therefore an object of the invention to provide a rotary adjuster for a structure, in particular for optical elements or optical components, preferably gratings and / or mirrors, which avoids the high adjustment and assembly effort of rotary adjusters according to the prior art and makes it possible to directly measure the rotational position or angle of rotation or the position of the rotary adjuster in order to adjust the rotary adjuster with high accuracy and to hold the rotary adjuster at a predetermined rotational position.

[0012] According to the invention, this problem is solved by a rotary adjuster which has all the features of claim 1.

[0013] By directly measuring the angular position of the rotary table of the rotary adjuster, it is possible to optionally compensate for position deviations that occur successively, such as thermal drift or mechanical relaxation.

[0014] Another objective of the invention is to provide a rotary adjuster that is compact in design and characterized by small dimensions, low weight and at the same time high precision and positioning accuracy.

[0015] This further problem of the invention is solved by a rotary adjuster with dimensions of less than 140 mm x 125 mm x 60 mm (width, length, and height) for the rotary adjuster including drive, gearbox, and angle measuring system. This means that preferred rotary adjusters, which are used, for example, in spectrometers, fit into a cube W × L × H with dimensions of 140 mm (W) × 125 mm (L) × 60 mm (H) including the glass scale. The dimensions of the motor and gearbox are W × L × H = 61 × 61 × 46 mm. The angle measuring system, comprising a glass scale and a sensor head, is also included. This means, as previously stated, that the dimensions of an exemplary complete system with all components including the glass scale and the sensor head have dimensions of W × L × H : 140 × 123 × 57 mm, which fits into a cube of less than 140 mm × 125 mm × 60 mm as previously claimed.Such rotary adjusters have the advantage that they can be installed in spectrometer setups with a compact housing in a space-saving manner and are easy to mount.

[0016] Although compact rotary adjusters slightly larger than the preferred cube size of 140 mm × 125 mm × 60 mm are possible, it should be considered that if the dimensions are significantly larger than 140 mm × 125 mm × 60 mm, problems will arise due to thermal drift effects. Furthermore, the rotary adjusters will not heat up uniformly, leading to twisting and distortion.

[0017] The compact design and simple installation of the rotary adjuster allow for easy replacement during servicing. Furthermore, rotary adjusters with such small dimensions as described are characterized by their low weight.

[0018] The rotary adjuster according to the invention, in particular the optical element that is set up, such as a grating and / or a mirror, comprises at least one rotary table with at least one turntable and a drive connected to the rotary table, preferably with at least one motor and / or a motor-gearbox combination and a rotary mechanism, as well as an angle measuring system for determining the angular position.

[0019] In a preferred embodiment, the angle measuring system is an absolute measuring system.

[0020] In a particularly preferred embodiment of the system according to the invention, the angular position is detected directly on the rotary table of the rotary adjuster, i.e. after the mechanical reduction, and thus as close as possible to the optical component to be positioned, due to the angle measuring system arranged directly on the rotary table.

[0021] In principle, both incremental and absolute angle measuring systems are possible. According to the invention, the angle measuring system is preferably an absolute measuring system. With an absolute angle measuring system, it is possible to determine the rotational position of the rotary adjuster directly and absolutely at any time, i.e., without a prior reference run, and to adjust the rotary adjuster from the determined rotational position until the desired angle of rotation is reached. This offers particular advantages because the grid or mirror does not first need to be moved to a known reference position from which the position can then be determined incrementally. Furthermore, with an absolute measuring system, no incremental pulses can be lost due to interference, which makes the measurement considerably more robust and therefore more accurate.

[0022] The rotary adjuster is preferably positioned within the spectrometer, and therefore far away from any potentially heated sample. In a typical setup, the microscope is connected to the spectrometer via 2 to 3 m long fiber optic cables.

[0023] In a preferred embodiment, a control and / or regulating system or control and / or regulating device is provided to adjust the angle of rotation, which, after determining the rotational position, controls the rotary adjuster in such a way that the rotary adjuster, which is preferably motor-driven, is moved to the desired rotational position, i.e., the desired angle of rotation.

[0024] In particular, the control and / or regulating device is used to adjust the angle of rotation in such a way as to compensate for a mechanical inaccuracy of the rotary mechanism, for example an inaccuracy due to drift movement, mechanical stress reduction or relaxation processes.

[0025] It is particularly preferred if the rotation angle is adjusted, especially with the aid of the control and / or regulating device, such that an angular accuracy of better than one arcsecond, preferably better than half an arcsecond, is achieved. This is particularly advantageous because such accuracies are achieved simply by tracking and, unlike the prior art, no complex adjustment or application of nonlinear fit routines is required. Furthermore, the active tracking reduces, or preferably completely eliminates, the need for frequent and costly recalibrations to ensure long-term accuracy.

[0026] In another operating mode of the rotary adjuster, it is also possible to forgo automated active tracking in the event of deviations below a specified threshold and instead allow small position deviations below the threshold.

[0027] Position deviations are detected and recorded over time. These deviations are then taken into account for subsequent software corrections of the measured spectra. An advantage of this operating mode is that the measurement can be performed with the grating in its resting position, eliminating the need to supply power to the stepper motor for readjustment. Oscillations around the target position and the associated heat generation are thus avoided.

[0028] This operating mode offers particular advantages when the rotary adjuster needs to remain completely stationary during spectral acquisition. The measurement accuracy of the angle measurement is significantly better than the achievable positioning accuracy of the rotary adjuster, which is limited by the mechanically reduced minimum motor movement of the rotary adjuster.

[0029] The adjustment of the rotary actuator is preferably carried out using a stepper motor. It is particularly preferred that, in order to achieve low synchronization error and a compact design, the gearbox, especially the gearbox of the motor-gearbox combination, comprises a wave gear. A wave gear, or so-called "harmonic drive," is characterized by a high reduction ratio and zero backlash, and thus high positioning and repeatability accuracy.

[0030] Wave gears have three components: 1. an elliptical steel disc (so-called “wave generator”) in the center of the gearbox, wherein the gearbox has a central hub as well as a thin, elliptically deformable special ball bearing, 2. a flexspline, which is a deformable, cylindrical steel bushing with radially arranged teeth around the outside and 3. a Circular Spline which, as a rigid and cylindrical outer ring, surrounds both the wave generator and the flexspline and is equipped with internal teeth.

[0031] The external teeth of the flexspline have fewer teeth than the internal teeth of the circular spline. This difference often amounts to two teeth. Typically, the wave generator is used as the input element, coupled to the motor, and the flexspline as the output element of the mechanism. The elliptical wave generator, as the driven element, initiates the wave gear process and initially deforms the flexspline. This flexspline engages manually with the internally toothed circular spline located on the opposite side of the ellipse's major axis. The rotation of the wave generator shifts the major axis of the ellipse and thus also the tooth engagement area. Crucially, the flexspline has fewer teeth than the circular spline, which is essential for the design and function of the wave gear.With a difference of, for example, two teeth, a relative movement of one tooth occurs between the flex spline and the circular spline after half a rotation of the wave generator. After a full rotation, the difference is already two teeth. This results in a strong reduction gear ratio combined with high backlash and high torsional stiffness.

[0032] To determine the precise location of the rotating table with turntable, and thus the optical element mounted on the rotating table, in particular the grating and / or the mirror, the angular positioning system of the invention includes an angular measuring system, or more specifically, a graduated circle angular measuring system. This can be a magnetically, inductively, or, preferably, optically operating angular or graduated circle angular measuring system. The optical graduated circle angular measuring system is preferably designed in the form of a measuring tape, for example, made of steel with periodically applied measuring marks, which is mounted on a circumference, in particular, of the rotating table that carries the optical element, preferably the grating and / or the mirror. Optically operated systems are particularly preferred over magnetic systems because they are the most precise systems.Magnetically or inductively driven systems offer advantages regarding contamination, which is not a concern with optically driven systems. Preferably, the angle measuring system or pitch-circle angle measuring system, in the form of a linear length measuring tape, is adhered and / or pressed onto the edge of the rotary table. The length information can also be applied to the circumference of the rotary table using a lithographic process, or by etching, printing, or engraving. Due to the circular surface of the rotary table, applying length information to its circumference using a lithographic process can be more challenging. The position of the rotary table can be determined via the measuring tape adhered to its circumference using at least one sensor.Determining the position of the rotating belt using a measuring tape and a sensor is not limited to using exactly one sensor. Using more than one sensor is also possible.

[0033] Determining the rotation angle indirectly by measuring the length on the circumference of the rotating stage avoids very expensive angle measurements. Linear length measuring tapes are simpler to manufacture and therefore cheaper. Furthermore, the length measuring tapes level out the roughness on the circumference of the rotating stage. Eccentricities of the rotational movement or uncertainties in determining the diameter of the rotating stage are transferred to a gain error for small rotational movements, which can be determined by calibrating the spectrometer with known calibration wavelengths. The gain error can be easily calculated for small rotation angles of the gratings, as used in spectrometer applications. High reproducibility is necessary for such downstream calibration.Since the change in position on the circumference increases linearly with the diameter of the rotating table, the further the measuring tape is positioned from the center (the pivot point), the more accurately the angular resolution can be derived from the length measuring system. Therefore, applying the length markings to the circumference of the rotating table using a measuring tape is preferred. By applying the measuring tape, the ruler itself is adhered to the table, the markings are transferred from the ruler, and the ruler is used as a stencil mask.

[0034] Preferably, the sensor is an absolute sensor with which the markings placed on the linear measuring tape are detected and the position is thus determined.

[0035] In one embodiment of the invention, the absolute sensor is an optical sensor. Preferably, the optical sensor comprises a photoelectric sensor with which the markings on the measuring tape are detected, or, in particular, an extremely fast digital camera or digital line scan camera that continuously takes images of the measuring tape and the markings on it. The measuring tape bears unique markings, so that the position of the section of the measuring tape detected by the sensor head at the time of measurement is similar to viewing a meter stick or a macroscopic measuring tape. Preferably, the markings on the measuring tape are stored in digital form and, most preferably, as contrast stripes in the form of barcodes with a nominal division period of 20-30 µm.Through special coding, such as 8B / 10B, 64B / 66B, or 64B / 67 coding, it is ensured that a sufficient number of contrast bars, and thus signal changes, are always present in the sensor's viewing window. This allows the sensor, which detects not just individual lines but always a range of 20–100 contrast bars simultaneously, to always determine a valid position. The exact operating principle of such absolute sensors is described by the manufacturers of these sensors, for example, Renishaw (https: / / www.renishaw.de / de / funktionsweise-der-optischenmesssysteme-von-renishaw--36979), and will be fully incorporated into this application.

[0036] Another embodiment would be a two-track sensor. This means that the system includes two measurement standards: an incremental and an absolute standard. This simplifies the encoding but also makes it more complex in terms of hardware, since two tracks need to be read.

[0037] The absolute sensor determines the linear absolute position on the measuring tape with a resolution of less than 100 nm, and preferably less than 50 nm. An evaluation unit then calculates the angular position of the rotary adjuster from the determined absolute position and the diameter of the measuring scale. If the diameter of the rotary table is, for example, 100 mm and the measuring tape is mounted on its circumference, an angular resolution of less than 0.5 arcseconds is achieved, which is significantly better than one arcsecond. If the pivot point of the rotary table deviates only slightly from its center, the resulting measurement error of the sensor is periodic to the rotation of the rotary table. For small rotation angles, this error is proportional to the rotation and can be easily corrected with a spectral calibration using known gas spectral lines.The same applies to metal strips with markings that are not perfectly adhered, or metal strips with markings where the strip is adhered and the adhesive thickness varies.

[0038] Particularly high positioning accuracy and compactness are achieved when, as described above, the gearbox is designed as a wave gear, wherein the wave gear preferably comprises a flex spline and a circular spline and has a high reduction ratio of at least 80:1 and preferably at least 100:1.

[0039] In addition to the rotary adjuster, which according to the invention is characterized by particularly high accuracy, the invention also provides a device for Raman microscopy, in particular confocal Raman microscopy and / or fluorescence microscopy and / or spectroscopy, wherein the device comprises a rotary adjuster according to one of the previously described embodiments and an optical element arranged on the rotary adjuster, in particular a mirror and / or a grating.

[0040] With the aid of the rotary adjuster according to the invention, extremely precise angular positioning can be achieved, particularly in a spectrometer. Reproducibility in the range of significantly less than one arcsecond is achieved with the rotary adjusters according to the invention.

[0041] The advantages of using a rotary adjuster according to the invention in a spectrometer will be described below. For example, in a spectrometer with a focal length of 600 mm, the CCD camera used to record the spectra is also 600 mm away from the optical grating. Typically, in spectrometry, the gratings are used in reflection mode. An error in the angular positioning of the grating or mirror therefore has a twofold effect: on the angle of the incident light and the angle of the reflected light. In the embodiment described, an error of one arcsecond in the angular positioning of the grating at a distance of 600 mm on the CCD camera thus corresponds to a displacement of approximately 5.6 µm. The CCD cameras used in such spectrometers typically have pixel sizes in the range of 15–26 µm.To ensure that the error caused by angular positioning remains smaller than one CCD pixel, the angular positioning must be better than 3-5 arcseconds. Smaller CCD pixels are technically possible, but they collect too little light per unit of time and become too light-insensitive. However, the spectral resolution of spectrometers is usually not limited by the CCD pixel size. Typical spectral lines in a spectrometer are usually mapped onto several CCD pixels. By fitting spectral lines, for example using a Gaussian or Lorentzian function, and determining the spectral centroid, interpolation in the CCD sub-pixel range can be achieved. By fitting spectral lines, spectral resolutions of less than 1% of the typical CCD pixel dimensions, and even lower, are possible for the spectrometer.Angular positioning errors of the grating in the arcsecond range are therefore clearly visible and can significantly distort spectral measurements if left uncorrected. Reducing these angular position errors to the sub-arcsecond range is highly advantageous because only then can the resolution increase achieved through the fitting process be realized without being masked by errors. Fitting the spectral lines is necessary because otherwise the pixel size of the CCD camera limits the spectral resolution. At the same time, the CCD pixels must not become too small to overcome readout noise, resulting in an unacceptably high signal-to-noise ratio.

[0042] In addition to the rotary adjuster for different optical elements, the invention also claims an optical device, in particular a spectrometer with such a rotary adjuster, and a method for setting a rotation angle of a rotary adjuster with a rotating table, wherein the method uses an angle measuring system or pitch circle measuring system, one of which is arranged on the latter.

[0043] According to a preferred embodiment of the invention, the optical device, in particular the device for Raman, especially confocal Raman and / or fluorescence microscopy and / or spectroscopy, comprises at least one optical element and at least one rotary adjuster on which the optical element is arranged, in particular mounted. A particular technical advantage of the invention is that the design of the optical element is very compact; in a preferred embodiment, the length L and the width W of the rotary adjuster are less than L < 125 mm and W < 140 mm, respectively. Preferably, the height H of the rotary adjuster is less than 60 mm.

[0044] The invention will now be described by way of example and without limitation with reference to the enclosed drawings.

[0045] They show: Fig. 1: a rotary adjuster according to the invention for an optical element, in particular a grating for use in a spectrometer Fig. 2: Rotary adjuster according to the invention with attached pitch circle measuring tape, sensor, drive and evaluation devices Fig. 3: Schematic diagram of the assembly of a rotary adjuster according to the invention, consisting of a rotary adjuster, a pitch circle measuring tape, a sensor, and a motor with a directly mounted shaft drive. Fig. 4: Schematic diagram of a wave gear Fig. 5: Section of the markings (barcode made from contrast strips; the absolute position is stored in the barcode as a coarse position in coded form; the fine position is determined by interpolation of the lines) on a measuring tape according to the invention Fig. 6: Schematic diagram of the detector for reading the graduated circle measuring tape Fig. 7: Dimensions of the fully assembled rotary adjuster according to the invention, with length L, width B and height H Fig. 8: Calibration result achieved of a 600 mm spectrometer equipped with a rotary adjuster according to the invention: The graph shows the residual error after calibration in pixels (16µm) compared to the different positions of the CCD chip.

[0046] In Fig. Figure 1 shows the schematic setup of a spectrometer, for example a Raman spectrometer as known from WO 2018 / 158 136 A1 or WO 2011 / 131 311 A1, with a rotary adjuster 1 according to the invention and an optical element 3, for example a grating arranged on the rotary adjuster or a mirror. The disclosure content of WO 2018 / 158 136 A1 and WO 2011 / 131 311 A1 is fully incorporated into the present application. In a spectrometer, in particular a Raman spectrometer, an optical grating is illuminated by a light beam 5 from a light source through an entrance slit 2 or pinhole. The pinhole can preferably also be formed by the end of an optical fiber. Preferably, the coupled light is Raman-scattered light, i.e., essentially a light source that contains non-monochromatic light components in addition to the excitation wavelength.The light beam 5 strikes the optical element, e.g., a grating, arranged on a rotary actuator 1 and is deflected in direction 7, e.g., towards a camera 9. This deflection can occur through diffraction in the case of the grating and through reflection in the case of a mirror. The distance between the camera 9 and the optical element, e.g., the grating 3, on the rotary actuator is preferably between 300 mm and 600 mm. The grating arranged on the rotary actuator is preferably a grating spectral filter of a spectrometer. In a Raman spectrometer, the beam of Raman light is expanded by suitable optics. The expanded beam then strikes the grating spectral filter mounted on the rotary actuator. The grating spectral filter diffracts the light in different directions according to its wavelength, so that, for example, a location-dependent spectral signal can be recorded on a CCD chip.The CCD chip, for example, has 1024 channels, each capable of capturing light of different wavelengths. The rotary adjuster is designed to achieve a minimum error of better than 1 arcsecond, preferably better than half an arcsecond. This is accomplished by measuring the rotary adjuster's angle of rotation, evaluating it with a control unit, and adjusting the angular position with the control unit to compensate for any mechanical inaccuracies in the rotary mechanism and achieve an angular accuracy of better than 1 arcsecond, preferably better than half an arcsecond. This is a very high level of accuracy, as harmonic drive gears without any sensors or rotation settings typically only achieve an accuracy of 20 to 30 arcseconds.

[0047] In Fig. Figure 2 shows the complete system of a rotary adjuster according to one embodiment of the invention. The embodiment according to Fig. Figure 2 is a system with only one sensor. This single-sensor system is merely an example and is not limited to this one. Another embodiment of the invention may include multiple sensors, for example, two sensors arranged close to each other or to the measuring tape. Preferably, these two sensors may be arranged on opposite sides of the pivot point. The use of two sensors instead of one sensor increases the accuracy.

[0048] An optical element, e.g., a grating or grating spectral filter, is arranged on the rotary table 4 of the rotary adjuster. A graduated circle scale in the form of a measuring tape 11 with a printed marking (not shown) is applied to the edge of the rotary table of the rotary adjuster, e.g., by adhesive. The graduated circle scale contains coded length and / or angle information, which is evaluated by the sensor 10 and serves to detect the rotational position of the rotary adjuster in order to then adjust it by motor, depending on the detected rotational position, until the desired rotational angle is reached. Preferably, the length information is determined by a sensor, as this is simpler. A grating or grating spectral filter 3 is arranged on the rotary table of the rotary adjuster.

[0049] To sensing the rotational position achieved by the rotary adjuster, a sensor 10 records the absolute position of the rotary adjuster via the scale on the measuring tape. The position of the rotary adjuster is transmitted to a control unit 14. A digital microcontroller is the central component of the control unit 14. From the rotational position of the rotary adjuster, which was determined with the absolute angle measuring system, the rotary table 4 of the rotary adjuster 1 can be adjusted so that the desired angle of rotation is reached and maintained. The pitch circle angle measuring system is applied to the rotary table, e.g., by gluing, whereby a precise angular position can be determined with the angle measuring system. The control unit 14 allows the rotational angle to be adjusted via the motor 13 and the gearbox 12 of the rotary adjuster in such a way that any mechanical inaccuracies of the rotary mechanism are compensated for.The angles determined with the angle measuring system according to the invention exhibit an angular accuracy of 5 to 0.01 arcseconds, preferably 1 to 0.5 arcseconds. This accuracy can be achieved without complex adjustments or fitting routines. The angle measuring system according to the invention is an absolute measuring system, eliminating the need for previously required light barriers for reference positions and time-consuming reference runs to these reference positions for initialization after commissioning the system, as is necessary with incremental sensors. This results in a significant simplification of the system's design and operation. The increased robustness of such an absolute system is also advantageous, since individual measurement errors, for example caused by contamination or vibrations, cannot influence and thus distort subsequent measurements (e.g., by integrating previous measurement errors).

[0050] In Fig. Figure 3 shows the schematic assembly of the components of a rotary adjuster according to the invention. The rotary table 4 of the rotary adjuster is mounted directly onto the gear flange 111 of the shaft gear 12, with the gear also being mounted directly onto the motor flange, so that the motor and gear form a compact motor-gearbox combination and the motor shaft and gear shaft are directly connected to each other. The scale 11 of the angle-pitch circle measuring system is applied to the circumference of the rotary table 4 by gluing or pressing and is evaluated via the sensor 10.

[0051] Fig. Figure 4 shows a top view of the essential parts of a wave gear as used in the drive of the rotary adjuster 1. The wave gear, also known as a "harmonic drive", according to Fig. Section 4 comprises an elliptical disk 100 in the center of the gearbox, which has a central hub and a thin, elliptically deformable special ball bearing. Furthermore, the wave gear consists of a flexspline 110 with radially arranged teeth 112 around its outer surface and a circular spline 120 with internal teeth 122. The number of teeth is significant for the harmonic drive, with the external teeth of the flexspline 110 having fewer teeth than the internal teeth 122 of the circular spline 120. This results in the gear reduction of the gearbox. The elliptical “wave generator” 100, as the driven element, initiates the wave gear process and deforms the initiating flexspline 110. The flexspline is located in the opposite regions of the large elliptical axis and engages with the internally toothed circular spline 120 in opposite regions located at each end of the long elliptical axis.The rotation of the wave generator shifts the major axis of the ellipse and thus the tooth engagement area. Crucially, the flex spline always has fewer teeth than the circular spline. When the circular spline is fixed, the flex spline, acting as the output element, rotates in the opposite direction to the input.

[0052] A key advantage of the wave gear over conventional gearboxes is the high achievable reduction ratio and absolute backlash-free operation throughout its service life, as well as high torsional stiffness across the entire torque range. Furthermore, this gearbox type is characterized by its small size and low weight compared to conventional gearboxes. The high reduction ratio and backlash-free operation also ensure high positioning and repeatability accuracy. The compact design of the gearbox also allows for direct mounting directly onto the stepper motor flange, enabling a direct connection between the motor shaft and gearbox shaft.This results in very compact motor-gearbox combinations that can be easily interchanged if necessary and that do without additional axle couplings, such as a bellows often needed to compensate for axle misalignment, which further simplifies the overall design and avoids the mechanical backlash of the overall system, for example caused by possible torsion of long drive axles.

[0053] Fig. Figure 5 shows the markings, in particular the contrast stripes that form a barcode and contain the position or angle information in a coded manner.

[0054] In this embodiment, the single-track measuring tape has contrast stripes across its full width, based on a nominal pitch of 30 µm. The absence of multiple parallel tracks provides the system with significant immunity to yaw errors during sensor head alignment and greater lateral tolerance.

[0055] The barcodes are preferably generated by feedback shift registers, since these methods for generating the barcode are self-synchronizing and also ensure that signal changes occur sufficiently often in the bit sequences, thus giving the barcodes a sufficient density.

[0056] In Fig. Figure 6 schematically depicts the beam path of the optical graduated circle measuring system. To read the scale 11, a light source 202, for example an LED, briefly illuminates an area of ​​the scale 11 opposite the sensor 200 at the time of reading via the illumination beam path 204. A prism or mirror 205 serves to direct the beam path and ensures that the illumination and detection beam paths 203 illuminate and detect the same area on the scale. This allows a fast digital camera 201 to capture an image of the illuminated section of the scale via the detection beam path 203 through the sensor's exit window 206. This image covers an area of ​​40–100 barcode contrast stripes. Each contrast stripe is mapped onto several adjacent camera pixels, so that the position of each contrast stripe can be determined with sub-pixel resolution by interpolation.This image is digitized and evaluated using digital signal processing.

[0057] A first algorithm determines the number stored in the barcode in encoded form, and thus the approximate absolute position. Meanwhile, another routine calculates a precise, high-resolution position by interpolating the exact positions of the individual bars in the camera image. This precise position is then combined with the approximate position to determine an absolute position with very high resolution.

[0058] Fig. Figure 7 shows the compactness of a fully assembled rotary adjuster according to the invention. All components are located within a cube with length L, width B, and height H. As shown in Fig. As shown in Figure 7, the size of the fully assembled rotary adjuster can be very small. In a preferred embodiment, the length L of the rotary adjuster is less than 125 mm and / or the width W of the rotary adjuster is less than 140 mm and / or the height H is less than 60 mm. The values ​​for length, width, and height are only examples and are not limiting.

[0059] Fig. Figure 8 shows the residual error after calibration of a spectrometer equipped with a rotary adjuster according to the invention. To demonstrate the great potential of the rotary adjuster, a spectrometer with a long focal length (600 mm) was used, and a grating with very high dispersion (2400 g / mm) was integrated into the spectrometer. The long focal length amplifies the positional error of the rotary adjuster (here 12-fold). With gratings of high dispersion, a large angular range of the rotary adjuster (here 38°) must be used simultaneously to image the desired spectral range onto the CCD chip (here 1650 pixels of 16 µm).

[0060] For spectrometer calibration, light sources with known emission spectra are generally used. The emission lines of gas discharge lamps are particularly suitable because the lines have a very narrow spectral width and their wavelength is known to 0.0001 nm. For this calibration, the lines (404.6565 nm (301); 435.8335 nm (302); 546.0750 nm (303); 576.9610 nm (304); 696.5431 nm (305); 738.3980 nm (306)) of a mercury-argon gas discharge lamp were used.

[0061] During the acquisition of the calibration data, each spectral line is positioned by the rotary adjuster to different positions (here 15 positions) of the CCD chip and its exact position on the chip is measured.

[0062] The data obtained in this process (angle of the rotary adjuster, wavelength of the emission line, and position on the chip) can be fitted to a mathematical model that incorporates the optical and geometric properties of the spectrometer. The deviation from this mathematical model is the residual error, which is present in the Fig. 9 was plotted against the chip position.

[0063] Since the position determination of the spectral lines here only has an accuracy of about 1 / 10 pixel, the actual positioning error of the rotary adjuster should be even smaller.

[0064] The invention provides, for the first time, a rotary adjuster, particularly for use in spectrometers or microscopes, that requires no initial reference run and is characterized by high accuracy, small dimensions, and low weight. It is further distinguished by its ability to set and maintain very precise angular positions of an optical component, such as a grating. Moreover, it eliminates the need to locate a home position, for example, using multiple light barriers. In the prior art, after the spectrometer is activated, a reference run to locate the light barrier would have to be performed. The additional time required for this step is approximately 40 seconds. This is avoided in the system according to the invention.

[0065] Furthermore, according to the invention, a Raman microscope, in particular a confocal Raman and / or fluorescence microscope and / or spectrometer with a rotary adjuster according to the invention is also provided. A method for setting a rotation angle of the rotary adjuster is also disclosed.

[0066] The invention comprises aspects which are the subject of the following sentences, but are not claims according to J 15 / 88: Sentences 1. Rotary adjuster (1) for a structure, in particular an optical element (3), preferably a grating and / or mirror with - at least one rotary table with at least one turntable - a drive connected to the rotary table, preferably comprising at least one motor and one gearbox and / or one motor-gearbox combination and one rotary mechanism characterized by the fact that The rotary table includes an angle measuring system for determining the angular position directly on the turntable, wherein the angle measuring system is preferably an absolute measuring system. 2. Rotary adjuster (1) according to sentence 1, characterized in that a control and / or regulating device is provided. 3. Rotary adjuster (1) according to one of sentences 1 to 2, characterized in that the angle of rotation is adjusted from the determined angular position by means of the control and / or regulating device (14) in such a way that a mechanical inaccuracy of the rotary mechanism caused, for example, by drift movements, mechanical stress build-up or relaxation processes is compensated. 4. Rotary adjuster (1) according to one of sentences 1 to 3, characterized in that the angle of rotation is adjusted by means of the control and / or regulating device in such a way that an angular accuracy of better than 1 arcsecond, preferably better than half an arcsecond, is achieved. 5. Rotary adjuster (1) according to one of sentences 1 to 4, characterized in that the drive comprises a stepper motor. 6. Rotary adjuster (1) according to one of sentences 1 to 5, characterized in that the angle measuring system comprises a pitch circle angle measuring system. 7. Rotary adjuster (1) according to sentence 6, characterized in that the pitch circle angle measuring system comprises a measuring tape (20), preferably a measuring tape made of steel with periodically applied measuring marks, which is preferably applied, preferably glued and / or pressed onto an edge, in particular of the rotary table. 8. Rotary adjuster (1) according to one of sentences 1 to 7, characterized in that the angle measuring system comprises at least one sensor, preferably an absolute sensor, in particular an optical sensor, preferably a digital camera or digital line camera. 9. Rotary adjuster (1) according to one of sentences 1 to 8, characterized in that the transmission, in particular the motor-transmission combination, has a reduction ratio of at least 80:1 and preferably at least 100:1, particularly preferably 320:1. 10. Rotary adjuster (1) according to one of sentences 1 to 9, characterized in that the gearbox is mounted directly on the motor flange. 11. Rotary adjuster (1) according to one of sentences 1 to 10, characterized in that the gearbox and the motor shaft are mounted directly and parallel to the shaft. 12. Rotary adjuster (1) according to one of sentences 1 to 11, characterized in that the rotary table of the rotary adjuster is mounted directly on the gearbox. 13. Rotary adjuster (1) according to one of sentences 1 to 12, characterized in that the transmission, in particular the motor-transmission combination, is a wave transmission. 14. Rotary adjuster (1) according to sentence 13, characterized in that the wave gear comprises a flexspline (110) with toothing arranged radially around the outside and a circular spline (120) with internal toothing. 15. Rotary adjuster (1) according to sentence 13, characterized in that the external toothing of the Flexspline (110) has fewer teeth than the internal toothing of the Circular Spline (120). 16. Device for Raman, in particular confocal Raman and / or fluorescence microscopy and / or spectroscopy, comprising at least one optical element, in particular a grating and / or mirror, and at least one rotary adjuster (1), characterized in that the optical element is arranged on the rotary adjuster (1). 17. Device according to sentence 13, characterized in that the rotary adjuster (1) is a rotary adjuster according to one of sentences 1 to 12. 18. Device according to one of sentences 15 to 17, characterized by the fact that the device includes a housing that The rotary adjuster incorporates the optical element. 19. Device according to one of sentences 15 to 17, characterized by the fact that the rotary adjuster includes a rotating table and the dimensions of the rotary adjuster by a length, A width and a height are indicated. 20. Device according to sentence 19, characterized in that the length L and the width B of the rotary adjuster are less than L < 125 mm and B < 140 mm. 21. Device according to one of sentences 19 to 20, characterized in that the height is less than 60 mm. 22. Method for setting a rotation angle of a rotary adjuster with a rotary table and at least one measuring body or graduated circle measuring body attached thereto, which has coded length or angle information, comprising the following steps: - by means of a sensor (10) we determine the absolute rotational position of the rotary adjuster based on the coded length or angle information, - The absolute position is transmitted to a control unit. - Due to the absolute rotational position, the rotary adjuster is preferably readjusted by means of the control unit via motor and gearbox until the desired rotational angle is reached and mechanical inaccuracies of the rotary mechanism are compensated for. 23. Method according to sentence 22, characterized in that the angle of rotation is set with an angular accuracy better than 5 arcseconds, preferably better than 1 arcsecond, in particular preferably better than 0.5 arcseconds. Reference symbol list: 1 rotary adjuster 2 Entry gap or pinhole 3 Optical element (optical grating or mirror) 4 turntables 5.7 mm light beam 9 Camera 10 Sensor 11. Embodiment of measurement 12 gearboxes 13 Engine 14 Control and regulating device 15 Coded position information 100 Elliptical disks (driven by the motor) 110 Flexspline (gear output) 111 Gearbox flange (connected to Flexspline) 112 External toothing Flexspline 120 Circular Spline (gearbox housing) 121 Gearbox housing (connected to Circular Spline) 122 Internal toothing Circular Spline 130 Centric hub 200 Sensor 201 Camera 202 Light source 203 Detection beam path 204 Lighting beam path 205 prism or mirror 206 exit windows 301 Measured deviation of peak position at 404.6565nm 302 Measured deviation of peak position at 435.8335nm 303 Measured deviation of peak position at 546.0750nm 304 Measured deviation of the peak position at 576.9610nm 305 Measured deviation of peak position at 696.5431nm 306 Measured deviation of the peak position at 738.3980nm QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 5,096,295 B1

[0007] US 9,551,612 B2

[0008] WO 2018 / 158 136 A1

[0046] WO 20117131 311 A1

[0046] WO 2011 / 131311 A1

[0046] Cited non-patent literature

[0000] https: / / www.renishaw.de / de / funktionsweise-der-optischenmesssysteme-von-renishaw--36979

[0035]

Claims

[1] Rotary adjuster (1) for a structure, in particular an optical element (3), preferably comprising a grating and / or mirror - at least one rotary table with at least one turntable - a drive connected to the rotary table, preferably comprising at least one motor and one gearbox and / or one motor-gearbox combination and one rotary mechanism where the rotary table includes an angle measuring system, preferably directly on the rotary table (4), for determining the angular position. [2] Rotary adjuster according to claim 1, where The angle measuring system is preferably an absolute measuring system. [3] Rotary adjuster for a device or setup, in particular an optical element, where The angle measuring system is an indirect measuring system in which the angular position is determined by measuring a length on the circumference of the rotating table. [4] Rotary adjuster (1) according to one of claims 1 or 3, where a control and / or regulating device is provided. [5] Rotary adjuster (1) according to claim 4, where From the determined angular position, the rotation angle is adjusted using the control and / or regulating device (14) in such a way that a mechanical inaccuracy of the rotary mechanism caused, for example, by drift movements, mechanical stress build-up or relaxation processes is compensated. [6] Rotary adjuster (1) according to any one of claims 1 to 5, where The rotation angle is adjusted using the control and / or regulating device in such a way that an angular accuracy of better than 1 arcsecond, preferably better than half an arcsecond, is achieved. [7] Rotary adjuster (1) according to any one of claims 1 to 6, where The drive includes a stepper motor. [8] Rotary adjuster (1) according to any one of claims 1 to 7, where The angle measuring system includes a partial circle angle measuring system. [9] Rotary adjuster (1) according to claim 8, where The pitch circle angle measuring system preferably has periodic measuring marks with reflective properties different from those of the adjacent material surfaces and is preferably applied to the corners, in particular of the rotating table. [10] Rotary adjuster (1) according to any one of claims 1 to 8, where The material of the rotary table is preferably a metal, in particular steel, with preferably periodically applied markings, which are preferably glued and / or pressed and / or attached and / or etched onto the corners, in particular of the rotary table. [11] Rotary adjuster (1) according to any one of claims 1 to 9, where the rotary adjuster comprises a metal strip which has measuring marks and is preferably glued and / or pressed onto the circumference of the rotary table. [12] Rotary adjuster (1) according to any one of claims 1 to 11, where the angle measuring system comprises at least one sensor, preferably an absolute sensor, in particular an optical sensor, preferably a digital or digital line camera. [13] Rotary adjuster (1) according to any one of claims 1 to 12, where the transmission, in particular the motor-transmission combination, has a reduction ratio of at least 50 : 1, in particular 80 : 1, preferably at least 100 :

1. [14] Rotary adjuster (1) according to any one of claims 1 to 13, where the gearbox is attached directly to the engine flange. [15] Rotary adjuster (1) according to any one of claims 1 to 14, where the gearbox and the motor shaft are aligned directly on and parallel to the shaft. [16] Rotary adjuster (1) according to any one of claims 1 to 15, where The rotary table of the rotary adjuster is attached in direct contact with the gearbox. [17] Rotary adjuster (1) according to any one of claims 1 to 16, characterized by , that The transmission, especially the motor-transmission combination, is a wave gear. [18] Device for Raman, in particular confocal Raman and / or fluorescence microscopy and / or spectroscopy, comprising at least one optical element, in particular a grating and / or mirror, and a rotary adjuster (1), where the optical element is arranged on a rotary adjuster (1). [19] Device according to claim 18, where the rotary adjuster (1) is a rotary adjuster according to any one of claims 1 to 17. [20] Device according to any one of claims 18 to 19, where The device comprises a housing that accommodates the rotary adjuster (1) and the optical element. [21] Device according to any one of claims 18 to 20, where the rotary adjuster (1) comprises a rotary table and the dimensions of the rotary adjuster are characterized by a length L, a width W and a height H. [22] Device according to claim 21, where the length L and the width W of the rotary adjuster (1) is less than L< 125 mm, W < 140 mm. [23] Device according to one of claims 21 to 22, where the height H is less than 60 mm. [24] Method for setting a rotary table of a rotary adjuster (1) comprising a rotary table and at least one measuring scale or graduated circle scale mounted thereon, which has coded length or angle information, comprising the following steps: - a sensor (10) is used to determine the absolute rotational position of the rotary adjuster based on the coded length or angle information - The absolute rotational position is transmitted to the control unit. - Due to the absolute rotational position, the rotary adjuster is preferably adjusted using a control unit via a motor and a gearbox until the desired rotation angle is reached and mechanical inaccuracies of the rotation mechanism are compensated. [25] Method according to claim 24, where The rotation angle is set with an angular accuracy of better than 5 arcseconds, preferably better than 1 arcsecond, and particularly better than 0.5 arcseconds. [26] Method according to at least one of claims 24 to 25, where The angle measuring system is an indirect measuring system and the angular position of the rotating table is determined by measuring a length on the circumference of the rotating table.

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