Low non-repeating runout rotary mount

Abstract

The rotation device (10) provides rotation of the position of interest about the axis of rotation and includes a first socket and a second socket, each having three contact points distributed about the axis of rotation. The contact points of each socket may be on a convex surface, and a spindle assembly (12) is held between the sockets facing each other along the axis of rotation. The spindle assembly (12) has a first convex surface centered about the axis of rotation that contacts the contact point of the first socket and a second convex surface that contacts the contact point of the second socket. The spindle assembly (12) also has a drive shaft (20) aligned with the axis of rotation. The linear stages (34, 36, 38) may be used to provide adjustment in one or more mutually perpendicular directions. Another embodiment uses a spindle (80) assembly (42) with two curved contact surfaces that are not aligned with the axis of rotation but contact respective curved surfaces adjacent the axis of rotation.

Description

Technical Field

[0001] The present invention generally relates to the field of precision rotating components, and more specifically to a rotatable sample support.

Background Art

[0002] Description of Related Art In various applications, there is a need to rotate components very precisely around a given axis while minimizing any displacement of the components both radially and axially with respect to the axis of rotation. Generally, motors and other drive mechanisms can provide rotation for mechanical operation, but provide rotation within a certain tolerance with respect to radial and axial displacement during rotation. That is, the component to be rotated stays approximately centered around the axis of rotation, but some degree of radial or axial deviation during rotation is considered acceptable and usually has an ignorable effect on the performance of the system. However, in a high-precision environment, such tolerances are considered unacceptable because they would fundamentally interfere with the operation of the system.

[0003] An example of a system where the rotation of components must be performed with minimal radial and axial deviations is the inspection of a sample using X-ray or electron diffraction. In such a system, a sample mounted on a goniometer is irradiated with an energy beam at a series of different rotation angles, allowing for three-dimensional characterization of the sample through the resulting diffraction image. However, due to the extremely small size of the sample, maintaining the sample within the beam path is particularly difficult. If a common center point of the sample is not maintained for different rotation angles of the goniometer, or if the object's features on the sample are not at the center of all rotations, the sample's features will move through a finite volume known as the "scatter sphere," which represents the smallest spherical range covering all possible positions of the infinitely small object at all possible rotation angles. Minimizing the scatter sphere necessitates minimizing the displacement of the sample due to the properties of the rotatable sample support, particularly the radial displacement relative to the direction of the irradiated energy beam. Some diffraction measurement systems require extremely high precision in the rotation of their samples, which may necessitate limiting unintended displacements that could move the target area of ​​the sample away from the beam path to the micron or submicron level. At such precision, even slight changes in the dimensions of the rotating components, or the presence of dust or even lubricant, can detrimentally increase the confusion sphere.

[0004] When evaluating such radial or axial displacements, recognition is given as to whether the displacement is repeatable or non-repeatable. Repeatable displacement, also known as repeating runout, is a manifestation of a persistent characteristic of the system that repeats with each rotation around the central axis. Such characteristics are therefore predictable and can be compensated for using high-precision linear stages, which achieve a more precise displacement scale than a rotating device. Non-repeatable displacement is a deviation that does not recur and therefore cannot be compensated for except in real-time correction. Both repeatable and non-repeatable displacements can occur in both the radial and axial directions relative to the axis of rotation. When operating high-precision rotating systems, minimizing any displacement is crucial for system performance. [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the present invention, a rotating device is provided that enables precise rotation of a target object around a rotation axis. [Means for solving the problem]

[0006] Summary of the Invention In a first embodiment of the present invention, the rotating device includes first and second sockets, between which a spindle assembly is positioned. Each socket has three contact points distributed around the axis of rotation, the three contact points of the first socket facing a first axial direction with respect to the axis of rotation, while the three contact points of the second socket facing a second axial direction opposite to the first axial direction with respect to the axis of rotation. The first socket has a first axial position on the axis of rotation, while the second socket has a second axial position on the axis of rotation, with the target position being between the first axial position and the second axial position.

[0007] The spindle assembly has a first convex surface centered around the axis of rotation and in contact with three contact points of the first socket. The spindle assembly also has a second convex surface centered around the axis of rotation and in contact with three contact points of the second socket, so that the spindle assembly is held between the first and second sockets. The drive shaft of the spindle assembly is aligned with the axis of rotation and extends away from the first and second convex surfaces of the spindle assembly to an axial position on the axis of rotation at the side of the first socket, away from the position of object. Thus, the drive shaft of the spindle assembly can be rotated to rotate the spindle assembly relative to the first and second sockets.

[0008] The three contact points of the first and second sockets may be located on the convex surfaces of their respective sockets, but it is also possible to use a substantially flat surface in a socket that provides three contact points. In an exemplary version of this embodiment, the first socket comprises a plurality of first socket balls, each providing one of the three convex surfaces of the first socket, and the first socket balls are held in the housing of the first socket by pressure fitting or the like. Similarly, the second socket may have a plurality of second socket balls, each providing one of the three convex surfaces of the second socket, and the second socket balls may be of the same size and material as the first socket balls. The material may be a hardened material such as ceramic that provides relatively low degrees of friction, wear, and deflection. Typically, the contacting materials will have a Mohs hardness of less than 9.0 and a surface finish of Ra 0.02 (micrometers) or higher.

[0009] In exemplary embodiments, the first and second convex surfaces of the spindle assembly may be formed by first and second spindle balls axially positioned on either side of the position of object, which may include a sample support for the sample to be analyzed. The first and second sockets may be mounted on a linear stage configured to allow adjustment of the position of the first and second sockets, and the spindle assembly, in a first adjustment direction. The linear stage may be one of several linear stages to which the first and second sockets are connected, allowing adjustment of the position of the first and second sockets and the spindle assembly in a plurality of mutually orthogonal directions. A chassis for the rotating device is also provided, which may include an elastic mechanism that biases the first and second sockets to press toward each other and allows slight changes in the relative axial position of the first and second sockets while the spindle is rotated. Rotation of the spindle assembly may be provided by a motor that rotates the drive shaft of the spindle assembly.

[0010] In another embodiment of the present invention, the spindle assembly may have two partially spherical contact surfaces, but the support structure with which they contact is located laterally to the axis of rotation rather than along the axis of rotation. The first support structure is located adjacent to a first axial position on the axis of rotation and has at least two contact points evenly distributed around a first radial direction perpendicular to the axis of rotation. The second support structure is located adjacent to a second axial position on the axis of rotation and has at least two contact points evenly distributed around a second radial direction perpendicular to the axis of rotation. The contact points on the first and second support structures may be located on curved surfaces that can take on different shapes. In one version of this embodiment, at least one of the first and second support structures may be a socket having three convex surfaces evenly distributed around a first radial direction, and the socket may use three socket balls, each providing one of the three convex surfaces. In another version of this embodiment, at least one of the first and second support structures may be two parallel rods, each of which provides one of two outwardly curved surfaces.

[0011] In this embodiment, the spindle assembly has first and second partially spherical surfaces, each being rotationally symmetrical about an axis of rotation. The first partially spherical surface contacts a contact point of a first support structure, and the second partially spherical surface contacts a contact point of a second support structure. The spindle assembly has a drive mechanism by which the spindle assembly can be rotated.

[0012] In this embodiment, a retaining mechanism is also provided for maintaining the first and second partially spherical surfaces of the spindle assembly in contact with the first and second support structures, respectively. The retaining mechanism may include a rotating bearing through which the spindle assembly passes axially and which is spring-loaded and can provide an elastic force that presses the spindle assembly toward the first and second support structures. When the first partially spherical surface is in contact with a support structure having two contact points, such as a pair of parallel rods, the movement of the first partially spherical surface is restricted by the action of the retaining mechanism in the radial direction perpendicular to the axis of rotation. When the first partially spherical surface is in contact with a support structure having three contact points, the movement of the first partially spherical surface is restricted by the action of the retaining mechanism in both the axial and radial directions.

[0013] As in other embodiments, the rotating device may include one or more linear stages to which sockets and support structures are attached. The linear stages are configured to allow adjustment of the positions of the first and second support structures and the spindle assembly in a first adjustment direction. Other linear stages may also be included that allow adjustment of the positions of the first and second support structures and the spindle assembly in other directions perpendicular to the first adjustment direction. A sample support for a sample to be analyzed by a diffractometer or other measuring instrument may be at the position of interest, and a motor may be used to rotate the spindle assembly.

[0014] The rotating device may also include a chassis to which the first and second support structures are mounted, the chassis including an elastic mechanism such as a leaf spring that bends to accommodate slight changes in the relative axial positions of the first and second sockets as the spindle assembly is rotated. In one version of this embodiment, the first and second partially spherical surfaces each have a convex portion on the side facing away from the position of object, and each of these convex portions contacts the respective rigid plane during rotation of the spindle assembly to restrict the axial movement of the spindle assembly. In this version, at least one of the rigid planes has an elastic connection to the chassis, the elastic connection allowing slight changes in the relative axial position of the rigid plane as the spindle assembly is rotated. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view of the rotating device according to the present invention. [Figure 2] This is a standalone perspective view of the spindle assembly of the rotating device shown in Figure 1, but in the opposite orientation compared to Figure 1. [Figure 3] This is a front view of one of the two three-sided sockets of the rotating device shown in Figure 1. [Figure 4] Figure 3 is a perspective view of the three-sided socket shown. [Figure 5] Figure 1 is a perspective view of the rotating device mounted on a chassis having three linear motion stages. [Figure 6] This is a perspective view of an alternative embodiment of the present invention, showing a spindle assembly having two partially spherical surfaces in spring-loaded contact with a trihedral socket and a pair of hardened support rods. [Figure 7] This is a perspective view of an alternative embodiment of the present invention, which uses a spindle assembly similar to the spindle assembly in Figure 6, but in which each of the partially spherical surfaces is in contact with a trihedral socket under spring load. [Figure 8]This is a perspective view of an alternative embodiment of the present invention, which has a spindle with partially spherical ends, each end located in contact with a hardened surface, and each end being supported by a pair of hardened support rods. [Figure 9] This is a perspective view of an alternative embodiment of a socket used in various embodiments of the present invention, in which the flat surface of the socket provides a contact point with the cooperating spindle. [Modes for carrying out the invention]

[0016] Detailed explanation A perspective view of the rotating device 10 according to the present invention is shown in Figure 1. The device is intended for use at low rotational speeds, including stop-start rotation, of a sample attached to an analysis system, and does not use rolling bearings or sleeve bearings, thus avoiding what may otherwise be a major source of non-repeated runout. Instead, a spindle assembly 12 with hardened balls 14 at both ends is mounted between two trihedral sockets 16, each socket containing three precision-machined contact balls 17 that establish three contact points between the socket 16 and the respective engaged spindle balls 14. A sample holder 18 is positioned in the central region of the spindle assembly 12, and a sample on the sample holder will be rotated along with the rotation of the spindle assembly. During rotation, the trihedral sockets 16 remain stationary, while the rotation of the spindle assembly is controlled by a drive shaft 20 that extends through the housing 22 of the proximal socket 16 and can be driven, for example, by a stepping motor or piezoelectric motor.

[0017] An exploded view of the spindle assembly 12 is shown in FIG. 2 (in an orientation opposite to that of FIG. 1). The components of the spindle assembly are aligned along the axis of rotation 24, and the distal end of the drive shaft 20 is fixed to the center point of the proximal one of the two balls 14 of the spindle assembly. In the embodiment shown, each ball 14 is firmly connected to a cylindrical flange 26, which in turn is firmly connected to the sample support 18 between the flanges 26. The balls 14 and the flanges 26 are also aligned, and in the exemplary embodiment, the drive shaft 20 is flexible enough that any slight misalignment will not be a problem, yet ensures that the entire spindle assembly rotates uniformly about the axis 24.

[0018] In this embodiment, each ball 14 is a perfect sphere, which makes it easier to manufacture and / or supply. Due to the adaptive forces of the precision manufacturing of such balls, the contact between the balls 14 of the spindle assembly and the balls 17 of the sockets 16 is less likely to cause axial runout during rotation, and any such axial runout tends to be repetitive runout, which is relatively easy to correct using a linear stage (further described below). Advantageous materials for the balls are ceramics, particularly silicon nitride, which is widely available in grades 3 and 5. Such materials exhibit particularly low friction and elasticity. Overall, the materials used for the spindle assembly and any support structures should have a low coefficient of thermal expansion to minimize sensitivity to temperature. In addition to silicon nitride ceramics, possible material choices could be Invar (registered trademark), although ceramics may be preferred if the invention is used in a system where the presence of metal would interfere with the operation of the system. However, those skilled in the art will recognize that, as an alternative to the balls 14, surfaces that are only partially spherical (in the vicinity of the contact points with their respective sockets) may be used, and that the balls 14 and their respective flanges could even be a single integral component as long as the device maintains three contact points between the partial spherical surfaces and the corresponding sockets.

[0019] A front view of one of the three-sided sockets along the axial direction is shown in FIG. 3. The socket housing 22 is generally annular, and three curved recesses 28 are arranged at equal intervals along its inner surface. These recesses respectively receive one of the three contact balls 17 of the socket. The outer surface 30 of the housing prevents the axial movement of the contact ball 17 when pressure is applied by the spindle assembly, and firm contact is maintained at the three contact points between the contact ball 17 and the adjacent spindle ball 14. In this embodiment, the press-fitting of the ball in the housing prevents the ball from moving when the spindle is rotated.

[0020] As shown in FIG. 3, the recess 28 of the housing has a nominal inner radius slightly smaller than the radius of the contact ball. When the ball 17 is pushed into the recess 28, the socket housing flexes, allowing the ball to be completely fixed within the recess. Thereafter, the elasticity of the socket housing 22 provides pressure on the outside of the ball, preventing the ball from moving relative to the housing 22. In another embodiment, the radius of the ball may be made to match the inner radius of the recess 28, and optionally, in any embodiment, an adhesive may be used to fix the ball to the socket housing 22. Also shown in FIG. 3 is a central hole 32 in the outer surface 30 that receives the drive shaft 20 of the spindle assembly 12 and is aligned with the axis of rotation 24. FIG. 4 shows a perspective view of the housing 22, which shows the relative thickness of the housing in the axial direction, and this relative thickness must be sufficient to accommodate the contact ball 17.

[0021] Figure 5 shows a rotating device 10 mounted on a chassis 35, having three linear stages 34, 36, and 38 that are movable in three mutually orthogonal directions, respectively. In the embodiment shown in Figure 5, the linear stage 34 may be adjusted along a rotation axis defined here as the “y-direction”, and the linear stage 36 may be adjusted along an axis perpendicular to the y-direction, defined here as the “x-direction”. The third linear stage 38 may move the device in the “z-direction”, which is perpendicular to the x-direction and y-direction and, in this embodiment, the direction of the illumination beam (indicated by arrow 37), such as the X-ray or electron beam of the diffractometer. In such an embodiment, the system is not as sensitive to errors in the z-direction, especially when the beam is collimated. For this reason, if compensation for the direction of the beam 37 is not considered necessary, another embodiment of the system may have only the linear stages 34, 36.

[0022] The linear stages 34, 36, and 38 help compensate for repetitive runouts that may occur despite tight system tolerances and can also be used for sample positioning. Repetitive runout errors are the displacements that occur with each rotation of the spindle and are therefore predictable. While radial runout is the primary error of concern, axial runout errors can also occur. Due to the predictability of repetitive runout errors, the linear stages 34, 36, and 38 can be controlled using software or hardware routines that adjust their linear positions in the x, y, or z directions based on the spindle rotation angle by an amount equal to and opposite to the predicted error. It is also possible to use the linear stages 34, 36, and 38 to compensate for non-repetitive runout errors, but because they are less predictable, the stage control must respond to means of detecting deviations in the sample holder's position. For example, when used in a diffractometer, detected errors in the diffraction pattern caused by movement along the Z-axis can be compensated using the linear stage 38. Depending on the application, both coarse and fine linear motion stages can be used for any of the three orthogonal directions, allowing for more accurate compensation of runout errors.

[0023] Figure 5 also illustrates the use of spring loads in the system in the axial direction. In this embodiment, the two trihedral sockets 22a and 22b are identical, and when assembled, each socket is fixed to the chassis support beneath it. However, the support beneath socket 22b consists of two parts interconnected by a leaf spring 39, which is deflected axially toward the interior of the assembly, causing socket 22b to exert a force relative to the spindle in the direction of socket 22a. Thus, the leaf spring 39 provides preload to the spindle / socket assembly while maintaining sufficient flexibility to compensate for axial displacements that may be caused by thermal expansion / contraction or axial runout.

[0024] Rotating systems often use lubricants to reduce friction, but in systems requiring submicron precision, lubricants can be a source of non-repeated runout errors. Therefore, in this embodiment, lubricants are preferably avoided. However, low rotational speed systems are less susceptible to the effects of heat buildup due to friction, and since the present invention relies not only on precise point contact between rotating components but also on hardened balls as contact surfaces, excessive friction and the resulting heat buildup are avoided. The absence of lubricants also allows the device to operate in a high vacuum environment. With selected materials, the device can be operated in a range from below zero degrees Celsius to several hundred degrees Celsius. Runout compensation tables or algorithms used to compensate for runout errors in the system may also include compensation for system errors caused by temperature changes.

[0025] In the embodiment shown, Grade 5 silicon nitride balls with a diameter of 12.7 mm were used with a spindle assembly having a total length of 3.8 cm, measured from the outside of one ball to the outside of the other. The balls at both ends of the spindle assembly were the same size as the balls of the trihedral socket, although the diameter of the spindle balls or socket balls may be modified to suit a particular application. The length of the spindle may also be adapted to the application, but generally, a longer spindle will reduce runout error.

[0026] Another embodiment of the present invention is shown in Figure 6. In this embodiment, the rotating device 40 uses a spindle assembly 42 having two rounded portions 44, 46 centered around a rotation axis 48. The rounded portions are partially spherical, and each contacts an underlying support structure. In particular, the rounded portion 44 rests on a trihedral socket 50, which in turn is mounted on a chassis 52. The trihedral socket 50 may have the same structure as the trihedral socket shown in Figures 3 and 4, but does not intersect the rotation axis 48. Rather, the three balls of the trihedral socket are located on one side of the rotation axis 48, providing low-friction support to the spindle. The rounded portion 44 contacts each of the balls of the trihedral socket 50 simultaneously and is positioned in the space formed between them. This positioning of the rounded portion 44 axially constrains the spindle assembly 42 and simultaneously allows for low-friction rotation.

[0027] The axial position of the spindle assembly 42 is constrained by the contact between the rounded portion 44 and the trihedral socket 50, so it is only necessary to constrain the rounded portion 46 radially. Therefore, this embodiment uses a pair of parallel rods 54 that contact the rounded portion 46 simultaneously. In this embodiment, the rods are cylindrical, but those skilled in the art will understand that the rods 54 do not need to be perfectly cylindrical if the surface that contacts the rounded portion 46 is curved and contact between each rod 54 and the rounded portion 46 is limited to one point. The socket 50 and the pair of rods 54 are placed adjacent to the axis of rotation 48, but their respective contact points are evenly distributed around the radial direction perpendicular to the axis of rotation. The three contact points of the socket 50 are evenly distributed around the radial direction 51, and the two contact points of the pair of rods 54 are evenly distributed around the radial direction 53.

[0028] To maintain contact between the spindle assembly 42 and the trihedral socket 50 and cylindrical rod 54, a spring-loaded rotary bearing 56 is provided to restrict the radial movement of the spindle assembly 42. A bracket 58 fits onto the bearing 56 and is secured by two springs 60 connected to the chassis 52. The springs 60 are under tension and press the bearing, and by extension the spindle assembly 42, toward the chassis 52, thus maintaining contact between the rounded portion 44 and the trihedral socket 50, and between the rounded portion 46 and the pair of rods 54. The bearing has sufficient radial flexibility so as to have little to no effect on the radial runout of the spindle assembly 42, which is in firm contact with the trihedral socket 50 and rod 54.

[0029] The embodiment shown in Figure 7 uses a spindle assembly 42 that is essentially identical to the spindle assembly in Figure 6, but it is shown in a different orientation than that in Figure 6. Similarly, the bearing 56, bracket 58, and spring 60 are identical, but the chassis and support of the device are different. In Figure 7, the partially spherical portions 44, 46 of the spindle assembly 42 each rest on sockets similar to the socket 50 in Figure 6. Since each of these three-sided sockets restricts axial movement, the system also uses axial spring loads to accommodate any slight axial fluctuations during rotation. Socket 50a is fixed to the chassis 70 of the device, while socket 50b is not fixed and is instead connected to two leaf springs 72a, 72b, each leaf spring being independently fixed to the chassis 70.

[0030] In the embodiment shown in Figure 7, the leaf springs 72a and 72b are fixed on the opposite side of the socket 50b in a position that holds the socket elevated above the surface of the chassis 70. That is, the socket 50b is suspended above the chassis 70 by the springs 72a and 72b and is therefore free to move axially as defined by the spindle assembly 42. The flexibility of the leaf springs 72a and 72b is selected relative to the tension of the spring 60 (which maintains contact between the spindle assembly and the socket), and the relative axial displacement of the spindle assembly parts 44 and 46 during rotation will result in the bending of the leaf springs 72a and 72b before any interruption of contact between the spindle parts 44 and 46 and their respective sockets 50a and 50b can occur. Thus, the suspension of the socket 50b by the leaf springs 72a and 72b eliminates the risk of radial displacement of one of the partially spherical parts, which may occur otherwise, and allows any slight axial error in the spindle assembly to be absorbed by the support device.

[0031] Another alternative embodiment of the present invention is shown in Figure 8. In this version of the present invention, the spindle 80 has two partially spherical portions 82a and 82b and is supported by two pairs of cylindrical rods 84a, 84b, similar to the cylindrical rod 54 in the embodiment of Figure 6. However, in Figure 8, it is not just one of the partially spherical portions 82a, 82b of the spindle 80, but both of them, that are supported by the cylindrical support. As in the embodiments of Figures 6 and 7, a spring-loaded rotating bearing 86 is provided to prevent radial movement of the spindle 80. A bracket 88 fits onto the bearing 86 and is secured by two springs 90 connected to the chassis of the device. The springs 90 are under tension and press the bearing, and by extension the spindle 80, toward the chassis, and thus maintain contact between the rounded portions 82a, 82b and the rod pairs 84a, 84b.

[0032] Since the rods of rod pair 84a, 84b are aligned parallel to the axis of rotation, they prevent radial movement of the spindle assembly, but do not provide such restriction in the axial direction. Thus, the rounded portions 82a, 82b present at each axial end of the spindle assembly 80 are in contact with each hardened stopper 92a, 92b, which provides a hard, flat, low-friction surface against which the corresponding portion of the rounded portion 82a, 82b of the spindle assembly is pressed. Since the contact surfaces of the hardened stoppers 92a, 92b are flat, there is a single point of contact between each rounded portion 82a, 82b and its respective stopper 92a, 92b. Thus, the hardened stoppers axially restrain the spindle 80 when it is rotated.

[0033] In the embodiment shown in Figure 8, the hardened stopper 92b is firmly attached to the side wall 94b of the chassis of the rotating device. However, at the opposite end, the side wall 94a is not fixedly attached to the chassis, but rather connected to the chassis via a leaf spring 96. The leaf spring 96 is axially flexible, and any slight change in the effective length of the spindle assembly 80 will be absorbed by the bending of the spring 96. Since the spindle assembly terminates at rounded ends 82a, 82b that press against the hardened stoppers 92a, 92b, in this embodiment there is no drive shaft extending axially beyond the spindle 80. Therefore, the drive motor 98 is positioned between the rounded ends 82a, 82b and used to rotate the spindle as needed.

[0034] In each embodiment described above, the socket or cylindrical rod that contacts the spherical or partially spherical surface of the spindle assembly is curved outward, and the contact is made between opposing curved surfaces. However, it is also possible that the contact is between a curved surface and a flat surface, in which case the contact is also a single point and therefore would have relatively low friction. For example, the trihedral socket used in any of the embodiments described above could be replaced by the socket 100 shown in Figure 9, which would still provide contact at three contact points between the spindle and the socket.

[0035] While the sockets of the embodiments described above use a convex surface to contact the spindle at a specific point, the socket 100 of Figure 9 has a flat surface that engages with one of the curved surfaces of the spindle according to the present invention. These flat surfaces may be a single piece of a larger socket component or even a flat piece of a socket having a single, single structure, but the socket of Figure 9 uses an insert 102 that is firmly fixed to the support portion of the socket. The use of such an insert simplifies the preparation of the surface of the insert that contacts the curved surface of the spindle, as the surface of the insert must be as flat and smooth as possible to minimize friction during the rotation of the spindle. Hard materials similar to those described above may be used for the flat surface.

[0036] In the shown embodiment, the insert 102 is positioned at a relative angular position of 120° around the outer circumference of the socket, but other relative positions of the surface may be used as long as the surface constrains the radial movement of the spindle as the spindle rotates. Similarly, the pitch of the surface is selected to provide sufficient limitation of such radial movement by the spindle, but those skilled in the art will recognize that such design details may be selected depending on the specific application and the respective contact forces between the spindle assembly and the surface. It is also possible to use three or more surfaces, but additional surfaces would usually increase the positional instability between the spindle assembly and the socket. The surfaces do not need to be perfectly flat as long as each surface has a single contact point with the spindle.

Claims

1. A rotating device for precise rotation around the axis of rotation of an object having a predetermined axial position on the axis of rotation, wherein the rotating device is A first socket having three contact points distributed around the rotation axis and facing in a first axial direction with respect to the rotation axis, wherein the first socket has a first axial position on the rotation axis, A second socket having three contact points distributed around the rotation axis and facing a second axial direction opposite to the first axial direction with respect to the rotation axis, wherein the second socket has a position in the second axial direction on the rotation axis, and the position of the object is located between the position in the first axial direction and the position in the second axial direction, A rotating device comprising: a spindle assembly having a first convex surface centered around the rotation axis and in contact with the three contact points of the first socket; and a second convex surface centered around the rotation axis and in contact with the three contact points of the second socket, wherein the spindle assembly is held between the first and the second sockets, and the spindle assembly further has a drive shaft extending away from the first and second convex surfaces of the spindle assembly, the spindle assembly being rotated via the drive shaft.

2. A rotating device according to claim 1, characterized in that the three contact points of the first socket are arranged on three substantially flat regions that contact the first convex surface of the spindle assembly.

3. A rotating device according to claim 1, characterized in that the three contact points of the first socket are arranged on three convex surfaces that contact the first convex surface of the spindle assembly.

4. A rotating device according to claim 1 or 3, wherein at least one of the first socket and the second socket comprises three socket balls, each socket ball providing one of the three contact points of the first socket.

5. A rotating device according to claim 4, characterized in that the three socket balls are held in a housing of at least one of the first socket and the second socket.

6. A rotating device according to claim 5, characterized in that the three socket balls are held in the housing of at least one of the first socket and the second socket by pressure fitting.

7. A rotating device according to claim 1, characterized in that the first and second convex surfaces of the spindle assembly are formed by first and second spindle balls arranged axially on both sides of the position of the target.

8. A rotating device according to claim 1, wherein the position of the object is equipped with a sample support for a sample to be analyzed in the measuring instrument.

9. A rotating device according to claim 1, further comprising a linear motion stage to which the first socket and the second socket are attached, wherein the linear motion stage is configured to allow adjustment of the positions of the first and second sockets and the spindle assembly in the adjustment direction.

10. A rotating device according to claim 1, further comprising a chassis to which the first socket and the second socket are mounted, wherein the chassis includes an elastic mechanism that biases the first and second sockets to press toward each other, and that allows for changes in the relative axial position of the first and second sockets while the spindle assembly is rotated.

11. A rotating device for precise rotation around the axis of rotation of an object having a predetermined axial position on the axis of rotation, wherein the rotating device is A first support structure is positioned adjacent to a first axial position on the rotation axis, evenly distributed around a first radial direction perpendicular to the rotation axis, and having at least two contact points. A second support structure is positioned adjacent to a second axial position on the rotation axis and has at least two contact points evenly distributed around a second radial direction perpendicular to the rotation axis, wherein the position of the object is located between the first axial position and the second axial position of the second support structure, A spindle assembly having a first partial spherical surface that is rotationally symmetric about the axis of rotation and contacts the contact point of the first support structure, and a second partial spherical surface that is rotationally symmetric about the axis of rotation and contacts the contact point of the second support structure, A rotating device comprising a holding mechanism that maintains the first and second partial spherical surfaces of the spindle assembly in contact with the first and second support structures, respectively.

12. A rotating device according to claim 11, wherein the first support structure comprises two surfaces that contact the first partial spherical surface of the spindle assembly at the two contact points of the first support structure, and the two surfaces prevent the first partial spherical surface of the spindle assembly from moving radially perpendicular to the axis of rotation by the action of the holding mechanism.

13. A rotating device according to claim 11 or 12, wherein at least one of the first and second support structures comprises a socket having three convex surfaces evenly distributed around the radial direction of the first, and each of the convex surfaces provides one of the contact points of the support structure.

14. The rotating device according to claim 13, wherein the socket comprises three socket balls, and each of the socket balls provides one of the three convex surfaces of the socket.

15. A rotating device according to claim 13, further comprising a chassis to which the first and second support structures are mounted, wherein the chassis includes an elastic mechanism that allows for slight changes in the relative axial positions of the first and second support structures when the spindle assembly is rotated.

16. A rotating device according to claim 11, wherein at least one of the first and second support structures includes two parallel rods, each of which provides one of the two contact points of the support structure.

17. The rotating device according to claim 11, wherein the holding mechanism comprises a rotating bearing through which the spindle assembly passes along the axial direction.

18. The rotating device according to claim 11, wherein the holding mechanism is spring-loaded and provides an elastic force that presses the spindle assembly toward the first and second support structures.

19. A rotating device according to claim 11, wherein the first and second partial spherical surfaces of the spindle assembly each have a convex portion on the side facing away from the position of the object, and each of the convex portions contacts the respective rigid planes of a hardened stopper during rotation of the spindle assembly to restrict the axial movement of the spindle assembly.

20. A rotating device according to claim 19, further comprising the first and second support structures and a chassis to which the rigid planes are attached, wherein at least one of the rigid planes has an elastic connection to the chassis that allows for a slight change in the relative axial position of the rigid plane when the spindle assembly is rotated.

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