The invention relates to a movement platform for rotating a carrier.
Known movement platforms for rotating a carrier about at least two axes, such as known from, for instance, EP 1 111 692, utilize three or four supporting means and a spherical carrier. Here, the carrier rests on the supporting means through gravity, so that for many uses, such a system is insufficiently stable, in particular when the carrier is very light. With small external vibrations, the spherical carrier can easily move.
It is known from, for instance, U.S. Pat. No. 5,872,417 to utilize movement platforms where the carrier is supported at the underside by supporting means while at the top side, compression means press against the supporting means. With this known form, only a small surface is left clear between the supporting and compression means, so that this known form is not particularly suited to allow the passage of an electromagnetic beam.
One object of the invention is to enable highly accurate rotation and displacement of the carrier. Preferably, this is possible with an accuracy of less than 1 nanometer.
Another object of the invention is to allow movement, rotation and/or removal of the carrier within a very compact area.
At least a number of these and other objects are achieved with a movement platform provided with a carrier and at least three spaced apart clamping means, wherein the clamping means each clamp the carrier at a contact point at least one globular contact surface of the carrier, while at least two clamping means are each provided with at least one displacement element for displacing at least one contact point relative to said contact surface and/or at least one clamping means such that the carrier can rotate about at least two imaginary axes. Here, the normal forces applied by the clamping means to the carrier are in approximately parallel planes, which parallel planes are approximately perpendicular to the tangential plane at the globular contact surface at the respective contact point.
A movement platform according to the invention is suitable for, for instance, microscopy, in particular transmission electron microscopy, optics, lithography, robotics, micro assemblage et cetera. A carrier is, for instance, a stage, a holder or the like, in which for instance a specimen can be placed. The carrier can also be suitable for carrying a camera, lens, chip, sensor, mirror or the like, depending on the use of the movement platform.
Clamping means clamp the carrier approximately perpendicularly, that is to say, radially, to the contact surface which is globular at the location of a contact point. Contact surface is understood to include the surface of the carrier on which the clamping means engage. Here, the contact point is the point where the clamping means clamps the carrier. With a globular design of the carrier, it can relatively easily be rotated between clamping means.
For a proper understanding of the invention, a distinction is made in this description between globular and spherical. Herein, globular is understood to include convex, spherical or, for instance, bent in double curves, however also hollow or concave. Globular therefore includes a ball, round cone, torus-shape, in principle doubly curved surfaces which are at least partly elliptical or circular in three orthogonal directions. In this description, globular should be construed to have a meaning broader than spherical, while spherical is to be understood as having the shape of a completely round cone, or being entirely round in all orthogonal views, at least in as far as this concerns the at least one contact surface. Here, the (contact) surface of a torus is indeed globular but not spherical.
In an advantageous embodiment, a movement platform according to the invention can be designed to be very “flat”. Here, the clamping means for instance are positioned so as to be substantially permanent in one plane, so that a movement platform can advantageously be designed to be very compact. Here, the normal forces are in one plane and the normal forces intersect approximately in the center of the clamping means and/or the carrier in the plane, also with rotations of the carrier. Also, embodiments are possible where the clamping means are substantially in one plane only in one middle position, that is, a position in which the carrier is not rotated. However, for rotation of the carrier, at least one clamping means and at least one normal force move out of this plane.
In the movement platform according to the invention, the normal forces applied by the clamping means, by clamping the carrier, are approximately perpendicular to the tangential plane of the globular contact surface through the respective contact point.
Clamping means can have the form of, for instance, arms, needles, plates, rods, faces, cubes, et cetera. For use within a microscope, it is advantageous when the specimen can be rotated about at least two axes, perpendicular to each other and perpendicular to the main direction of the electromagnetic beam. The main direction of the electromagnetic beam is understood to mean the main direction of, for instance, the photons or electrons radiating through or along the specimen.
In addition to rotations, the invention is also suitable for translations, in particular along three axes. This is very favorable for, for instance, examination of the specimen in applications such as microscopy.
In a preferred embodiment, the invention has three clamping means, so that translation is possible along three axes, at right angles relative to each other, and rotation is possible about at least two axes at right angles relative to each other. More than three clamping means render the movement platform, in principle, overconstrained. A minimum of clamping means can for instance be desirable as the clamping means will then undergo less slip, which may be caused by imperfectly coordinated movements of the clamping means relative to each other upon a translation or rotation of the carrier.
For rotation and/or translation of the carrier, displacement elements are provided. They displace clamping means at least tangentially and radially (perpendicularly) relative to the globular contact surface at the respective contact point. Displacement elements comprise, for instance, pistons or piezo-elements, with which, in a movement platform according to the invention, a contact point can be displaced by a user with the aid of clamping means, with an accuracy of less than approximately 1 nanometer.
Another advantage of the invention is that the carrier can rotate, move and/or be held in position with great stability. This means, for instance, that the carrier vibrates relatively little, for instance due to influences from outside and/or irregularities in the displacement elements because of, for instance, noise in electric voltage. The stability is characterized in that, for instance, vibrations can be achieved of less than approximately 0.1 nanometer.
In a preferred embodiment according to the invention, the carrier comprises a recess. This serves as “inspection hole” in which or through which for instance a specimen is borne/held and can be examined. A recess could also be designed for including a lens, camera, chip, sensor, mirror or the like. With microscopes, for instance, it is advantageous when the recess is continuous, so that a beam of electromagnetic radiation (photons, electrons, ultraviolet radiation et cetera) falls through the recess on a projection surface (and through and along, for instance, a specimen). Thus, an image is created. In an advantageous manner, with the aid of a double conical shape, that is, an hourglass shape, the beam can proceed straight through the recess if the carrier is rotated from a middle position. For a maximum angular rotation of the carrier, the clamping means are, in a middle position, at approximately an equal distance from the recess.
In an advantageous embodiment, at least one clamping means is provided with resilient and/or hinging elements, with which overconstraint of the movement platform is removed as much as possible. In a preferred embodiment, one clamping means is provided with resilient and hinging elements and a second clamping means with hinging elements. Herewith, resistance the clamping elements may produce relative to each other, for instance in the case of not properly coordinated movements of the clamping means relative to each other, can be advantageously reduced. In addition, slip between clamping means and carrier is prevented. In general, due to these features, the stability and accuracy of the movement platform are further increased.
In a preferred embodiment, piezo elements are used as displacement elements. This technique is advantageous for a device according to the invention because it is, inter alia, energy-friendly, robust, it comprises no moving parts and is very precise.
An advantageous embodiment of the invention utilizes one or more linear piezomotors. This is a principle known to the skilled person, known for instance from “Constructieprincipes voor het nauwkeurig bewegen en positioneren” (Constructional principles for accurate movement and positioning) by M. P. Koster, 1996, published by University of Twente of Enschede, the Netherlands, which principles will only be described here insofar as relevant to a proper understanding of the invention. Other principles too, such as, for instance, an Impact Drive Motor, a travelling wave motor, a Sliding Friction Motor or other (piezo) motors are eminently usable in a device according to the invention. However, the linear piezo motor has appeared highly advantageous as component of an embodiment of the invention. Here, one clamping means preferably comprises two fingers, which, very closely together, engage the carrier. The two points of contact of these fingers with the carrier can therefore be considered as one contact point. Here, the contact point is approximately in the middle of the two points of contact. At that contact point, the two fingers are approximately perpendicular to the carrier. For rotating the carrier, the two fingers “walk” in place. “Walk” is at least understood to include that a first finger clamps and rotates the carrier while the other one allows the carrier to pass, for instance through release from the contact surface, or letting it slip. If the carrier is to be rotated further, a second finger of the same clamping means takes it over and rotates the carrier while the first finger “retracts” and moves along the second finger in the opposite direction. Hereafter, the first finger can take over again and rotate the carrier, with the second finger retracting and moving along the first finger in opposite direction. In principle, this cycle keeps repeating itself until the desired end position is achieved.
An advantage of such an embodiment is that the movement platform can be designed very compactly. The fact is that upon rotation, the carrier rotates approximately about its own axis while the compactly designable fingers also remain approximately in place. During use, the fingers can remain in one plane, so that the movement platform can be of very flat design. As a result of this too, a preferably substantially spherical carrier with, for instance, continuous recess can rotate through great angles.
In an advantageous embodiment, use is made of a “lame” walker whereby, with the aid of displacement means, from one clamping means only one finger is displaced and the other one is passive. “Passive” is understood to mean not provided with displacement elements. The advantage hereof is that in a condition of rest, the carrier can be clamped by the passive finger and that thus, a stable situation is achieved due to little influence of noise and/or vibrations in and from the displacement element.
A movement platform according to the invention is very suitable as movement platform for a microscope, in particular a transmission electron microscope. In order to examine the specimen within the very compact space in the microscope between pole shoes of a transmission electron microscope with very high stability, in a preferred embodiment, the clamping means are preferably attached to the lower pole shoe. By attaching the clamping means to the lower pole shoe, the carrier can be included in the clamping means in a relatively simple manner.
The invention also relates to a specimen carrier, which is eminently suitable to be taken up in a movement platform according to the invention.
In clarification of the invention, embodiments of the devices and a method according to the invention will be further elucidated with reference to the drawing. In the drawing:
In this description, identical or corresponding parts have identical or corresponding reference numerals. As exemplary embodiment is described, inter alia, a movement platform for a transmission electron microscope. However, the invention is suitable for several uses where a carrier is rotated. For instance, a movement platform according to the invention can be used in optics, in the field of technology of micro assemblage, with different types of microscopy, with robots, in particular micro or nano robots, in lithography, cameras, sensors et cetera.
An embodiment according to the invention, as shown in, for instance,
The spherical carrier 2 shown in
In
In another advantageous embodiment, clamping means 3 are designed as “walking fingers” 7, as is the case in
Both the plate-shaped and the finger-shaped clamping means 3 engage the carrier 2 at contact points 13. Upon rotations of the carrier 2, the contact surface 14 “rolls” over the clamping means 3, or at least one finger 7 thereof. If the end of a clamping means 3 and/or finger 7 which is to engage the contact surface 14 is, for instance, flat or elongated, a contact point 13 is displaced both along the contact surface 14 and along the clamping means 3 upon rotation of the carrier 2. For a proper understanding of the invention, with embodiments according to the invention having fingers 7, each pair of fingers 7 can be considered as one clamping means 3, and the respective contact point 13 lies between the points of contact of the finger 7 with the carrier 2. In a minimal case, only one contact point 13 will move relative to one contact surface 14 or one clamping means 3. This latter may be the case with a movement platform 1 with at least two clamping means 3 having, for instance, pointed fingers 7. It will be clear to the skilled person that several embodiments of the clamping means 3 are possible according to the invention, within the framework of the invention, also the clamping means 3 of one embodiment can mutually differ.
An advantage of a substantially spherical carrier 2 is that the continuations of the normal force vectors Fn intersect approximately in this center and the contact points 13 remain approximately in one plane B both in a middle position and after rotation of the carrier 2. Therefore, all frictional forces Fw remain substantially the same in magnitude and direction, and a relatively stable and highly compact movement platform 1 is obtained. Hence, the movement platform 1 can be designed to be very flat.
It will, for that matter, be clear to the skilled person that the schematic representations of the Figures shown merely serve as explanation. For the sake of simplification, in the cross-sections, each time, only two clamping means 3 are represented. However, in practice, movement platforms 1 according to the invention will preferably comprise at least three clamping means 3. The skilled person will have no difficulty in making this adjustment.
However, there are embodiments within the framework of the invention which (schematically) may indeed exhibit cross-sections as shown in
To have the fingers 7 move, displacement elements are provided which can move a finger 7. In a preferred embodiment according to the invention, these are provided in the form of piezo elements 4. However, the invention is not limited thereto, many types of displacement elements are possible, for instance pistons, pivot motors and the like. Piezo elements 4 offer the advantage that they can transmit very small movements in a controllable manner. As can be seen in
According to the walking principle, a movement of a finger 7 in radial direction by means of the piezo element 4a will at least contribute to a translation of the carrier 2, while a movement of a finger 7 in tangential direction, by means of piezo element 4b, will contribute to rotation of the carrier 2. In
In general, displacement elements can be susceptible to vibrations or uncontrolled variations. It is for instance difficult to prevent piezo elements 4 from experiencing voltage noise which will cause vibrations in the piezo elements 4. It may therefore be favorable to use as few displacement elements as possible. Considering the above, according to a preferred embodiment according to the invention, per clamping means 3, one “lame” finger 7c can be advantageously used, as shown in
Naturally, many other “walking” principles are conceivable within the framework of the invention. Also, many displacement means are known that can be used with a movement platform 1 according to the invention, such as for instance an Impact Drive Motor, a travelling wave motor, a Sliding Friction Motor et cetera. These examples of displacement elements relate to piezo elements 4. With other displacement elements, also a wide range of possibilities will present itself. These are also understood to fall within the framework of the invention.
When utilizing an embodiment according to the invention in an electron microscope, carrier 2 can be provided with a recess 9. The recess 9 enables the electron beam to fall in a main direction 11 through the carrier 2. Due to the presence of the specimen 10, the beam will be interrupted in the recess 9, or, at the issuing side of the carrier 2, the intensity of the beam will differ across the cross-section perpendicular to the main direction 11 (the projection). Through a subsequent capturing and processing of this difference in intensity, an image of the specimen 10 with a very high resolution can be obtained. It will be clear that the recess 9 can also be advantageous for other forms of electro magnetic radiation, for instance a light beam, ultraviolet radiation et cetera.
The carrier 2 must also allow the passage of the electro magnetic radiation with rotations in the main direction 11. As represented in
If a carrier 2 according to the invention is substantially spherical, as is the case in
In order to, nevertheless, reach greater angles of rotation, in a different embodiment according to the invention, the carrier 2 can be of torus-shaped design, as shown in, for instance,
With an embodiment according to the invention with torus-shaped carrier 2, as shown in, for instance,
It is self-evident that the plate-shaped clamping means 3 are also suitable for clamping the spherical carrier 2, while the contact points 13 are indeed approximately in one plane B and the normal forces Fn do intersect in the middle of the carrier 2.
If the clamping means 3 are not controlled exactly synchronously upon rotation of the carrier 2, slip may occur, which may lead to inaccuracies. In this manner, in particular an overconstrained system 1 may lead to inaccuracies. To avoid this, in a preferred embodiment of a movement platform 1 according to the invention, at least one clamping means 3a is arranged in a hinging and resilient manner.
Such an embodiment according to the invention is shown in
Another overconstraint can be removed by providing clamping means 3a with a resilient or compression element 6. The clamping means 3a with the resilient element gives way in the spring direction, while this clamping means 3a with resilient element 6 still applies sufficient clamping force Fn to the carrier 2. Using a resilient element 6, for instance a spring, a piston, an elastic element, et cetera, with a clamping means 3 removes resistance with translations in the spring direction, preferably approximately perpendicularly to the respective clamping means 3a. By removing the resistance, in an advantageous manner, slip will again be prevented to a large extent.
It will be clear to the skilled person that such hinging and resilient elements 5, 6 can also be used on other embodiments according to the invention, for instance with plate-shaped clamping means 3.
The movement platform 1 according to the invention enables rotation and translation about and along at least three axes in a highly advantageous manner. In applications for, for instance, electron microscopes, rotation about two mutually perpendicular axes is often sufficient, which axes are perpendicular to the main direction 11. Rotation perpendicular to a main direction 11 needs not be absolutely necessary because, to this end, other solutions may be available, such as, for instance, rotation of a projection image by means of software. Here, the projection image is the depiction of the specimen 10 obtained afterwards on, for instance, a computer. Here, it is favorable to use at least two hinging clamping means 3, with the aid of, for instance, the hinges 5A-C mentioned.
With the embodiment where the carrier 2 rotates only about the two axes perpendicular to the main direction 11, unintentional rotations of the carrier 2 about the main direction 11 can be formed as a result of specific orders of rotations about the two axes perpendicular to the main direction 11. Such unintentional rotations can be prevented by taking these into account in the algorithmics coordinating the rotations about the other two axes. An unintentional rotation about the main direction 11 can also be cancelled through a different control of the rotations about the other two axes.
With a transmission electron microscope, an embodiment of a movement platform 1 according to the invention is placed nearby the pole shoes 17 so that the electron beam falls stably along and/or through the carrier 2. Between the pole shoes 17a and 17b, the electron beam radiates in main direction 11. Between the upper and lower pole shoes 17 (as indicated in
In
Naturally, also the entire movement platform 1 can be removable from the microscope or, conversely, be fixedly provided. Also, separate parts of the movement platform 1, such as for instance the carrier 2 can be replaced within the framework of the invention.
It will be clear that several embodiments fall within the framework of the invention. It is for instance possible that a specimen 10 is positioned on or in the carrier 2 via another part, for instance a holder, or that the movement platform 1 is placed in a holder. Many intermediate parts are conceivable which may imply a modification but with which the inventive concept remains intact. Furthermore, the movement platform 1 can be placed at any angle relative to, for instance, a microscope or the earth. In a middle position, the movement platform 1 can for instance be askew, vertical, horizontal, et cetera. The carrier 2 may also stand still and the movement platform 1 may move, et cetera. As is represented in, for instance,
Number | Date | Country | Kind |
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05076866.2 | Aug 2005 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/NL2006/000417 | 8/11/2006 | WO | 00 | 6/17/2008 |