US 3720849 A
The application deals with a magnetic-kinematic precision stage system. The essence is, that stages with linear or angular movement are composed of at least two plates, which move with respect to each others on ball joints. The two plates are held together with retaining magnets. This solution garanties the complete elimination of the backlash. The plates may move very freely, practically without force, with respect to each other. Because practically there is no force, as consequent there is very low friction, and thus adjustement with the greatest precision is possible.
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Description (OCR text may contain errors)
ilnited States Patent 1191 Eardocz M IMarch 13, 1973 15 1 MAGNETlC-KINEMATHC PRECISION 3,611,577 10/1911 $111111 ..310 111 x STAGES 3,608,409 9/1971 Schmidt ..310 s.7 x 3,941,331 4/1969 Kesling ..248/206 A X  lnventor: Arpad Bardocz, Rumannstrasse 57, 2,731,879 1/1956 conorerm 248/206AX 8 Munich 23, Germany  Filed: June 7, 1971 Primary Examiner-J. V. Truhe Assistant Examiner-B. A. Reynolds [211 App! 150372 Attorney-Edwin Greigg  Foreign Application Priority Data  ABSTRACT June 16, 1970 Germany ..P 20 29 715.8 The application deals with a magnetic-kinematic precision stage system. The essence is, that stages with  11.8. C1 ..310/8, 248/206 A, 3 10/83 linear or angular movement are composed of at least  Int. Cl. ..H0lv 7/00 two plates, which move with respect to each others on 1 Field of Search ball joints. The two plates are held together with 335/29 243/206 retaining magnets. This solution garanties the 21 1 complete elimination of the backlash. The plates may move very freely, practically without force, with 1 References C'ted respect to each other. Because practically there is no UNITED STATES PATENTS force, as consequent there is very low f nctron, and
thus ad ustement with the greatest precision IS possi- 2,850,943 9/1958 Grineff ..248/206 A X ble. 2,568,575 9/1951 Wickman ..335/285 X 2,952,185 9/1960 Palmer et aL... ..248/206 A X 10 Claims, 15 Drawing Figures PATENIEDMARI 31915 sum 2 0F 3 Fig.3a
MAGNETIC-KINEMATIC PRECIISION STAGES The magnetic-kinematic precision stages of this invention permit linear and angular motions with a precision hardly possible in previously-existing devices. In addition to their application in microscopy, semiconductor technology, and other branches of industry, such stages have a special significance in the fields of modern optics, laser technology, holography, and inter ferometry, to name just a few examples. These technologies require mechanical stages adjustable with a precision and reproducibility that has been previously seldom required.
The systems described here are based on completely new construction principles, and permit a greater precision of motion along or around the x, y, and z axes. The basic system is comprised of two plates which rotate or move laterally with respect to each other on ball joints, and which are held together by retaining magnets.
This solution guaranties that all motions are without backlash. Since the magnetic force offers no resistance to a motion perpendicular to the force direction, the plates may move very freely with respect to each other, and thus may be adjusted with the greatest precision. The adjustments are made with either ordinary screws or micrometer screws, which are bound to a rigid base. The screw spindle works against a movable part which is held to the spindle by a retaining magnet. The screw or micrometer head can be replaced by a piezoelectric coupling.
The significance of this invention may be best appreciated by considering the requirements demanded of similar devices and the extent to which this invention satisfies these requirements.
In any precision adjustment which requires an exactness of 0.001 mm or better, there are three construction problems which affect the reproducibility of the adjustment. They are: l) backlash between the components; (2) backlash in the adjustment control; and (3) securing a uniform motion.
Freedom from backlash: With present-day technology, a device whose freedom from backlash makes possible a reproducibility on the order of 0.00l mm can be achieved only by using a spring action. The spring action can be achieved either by the use of springs or by a spring construction in the contact guides. Both solutions make the motion more difficult, since such slides can be moved only by applying a force.
Backlash: ln every mechanical stage, it is necessary to have a retaining force tending to hold the slide in its original position. In order to eliminate backlash, all present-day stages use springs to provide the retaining force. The use of springs, however, means the application of force, and indeed, the force changes over the pathlength of the slide.
Uniform motion: Experience shows that a uniform motion re, a jerk-free motion can be achieved only when the motion is force-free and without friction. Wherever a force is applied, there is also friction, and thus a non-uniform motion. It is clear that it is ad vantageous for the motion to result from the smallest possible forces. With present-day technology, this is the case for the magnetic-kinematic solution of this invention.
It should be explicitly stated that piezoelectric ceramic materials have great significance in achieving motions of the highest fineness. Piezoelectric transducers are by their nature not suitable for transmitting large forces. Thus the magnetic-kinematic devices of this invention are extremely well suited for operation with piezoelectric transducers.
The invention will be better understood, and further objects and advantages will become more apparent, from a reading of the following specification taken in conjunction with the drawing, wherein:
FIG. la is a front elevation of one embodiment of the invention;
FIG. 1b is a plan view of FIG. 1a;
FIG. 2a is a front elevation of a second embodiment of the invention;
FIG. 2b is a plan view of FIG. 2a;
FIG. 3a is a front elevation of another embodiment;
FIG. 3b is a plan view of FIG. 3a;
FIG. 4 is an exploded perspective view of elements shown in FIGS. 3a and 3b;
FIG. 5 is a schematic plan view showing one position of the micrometer screw for adjustment on the x-axis;
FIG. 6 is a schematic plan view of another position of said micrometer screw;
FIG. 7 is a schematic plan view of another position of said micrometer screw;
FIG. 8a is a front elevation of another embodiment of the invention;
FIG. 8b is a side elevation of FIG. 8a;
FIG. 8c is a schematic view showing the various adjustments which can be made by the device of FIGS. 8a and 8b;
FIG. 9a is a front elevation of another embodiment of the invention; and
FIG. 9b is a plan view of FIG. 9a.
FIG. (la) and (lb) show a linear translating stage. The two opposing parts of this linear magnetic-kinematic translating stage roll on balls confined in linear grooves, the individual parts being held together by magnetic forces. FIG. (la) and (lb) show the application of a magnetic-kinematic system in an optical device. As shown there, the two-piece linearly-translating member (V) and (Z) are mounted onto an optical bench rider (R). The upper part of the translating member is a slide which rests upon balls and is movable in the plane of the FIG. (lb). The two parts of the translating member are held together magnetically as shown by arrows m.a. indicating the magnetic attraction. A Knob (T), covered on the side with plastic, provides a coarse adjustment of the slide. The fine motion is made with a micrometer screw (M). The micrometer screw is attached to the lower part of the translating member (V) and holds the slide with a magnet (N). A device translatable in two perpendicular directions (x and y direction) is possible by combining two of the translating devices shown in FIG. Ia and lb.
Magnetic-kinematic movements are also very well suited for producing angular rotations. FIG. 2a and 2b show a device in which a precision adjustment around the z-axis (the vertical axis) is possible. The example is taken from an optical device. The rider column (S) is fastened to a disc (U) which rotates with respect to a lower part (R). The disc rests upon balls confined in matching circular grooves milled into the two parts, and the parts are held together magnetically as indicated by arrows m.a. The lower part rests upon an optical bench rider (R) and may be fastened to it with magnets. The disc, and hence also the column, may be rotated through a full 360. The micrometer screw (M) acts against a protrusion (G) from the rotating disc and is fastened to it by a coupling magnet. The protrusion may be set at any desired position along the edge of the disc.
If a circular groove is milled onto the optical rider (R), the rotating disc may be set directly on the optical rider.
The x and y translation and the rotation about the z axis, as shown in FIGS. 11: and lb, and 2a and 2b, can be built together into a single unit, as shown in FIG. 3a and 3b. For better understanding, this figure is shown in an exploded view in FIG. 4.
The placement of adjustment screws or micrometer heads in the magnetic-kinematic system represents a special problem. Basically, it is often necessary to restrict the dimension of the device along the direction of the motion (x-axis). The problem does not generally occur in the y-direction. When the problem occurs, the micrometer head should be placed either over or next to the slide. FIGS. 5, 6, and 7 show various possibilities for locating the adjustment device on the x-direction slide.
FIG. 5 shows a device in which the adjustment screw or micrometer head is located as an extension of the slide.
FIG. 6 shows a device in which the adjustment screw or micrometer head is located on top of the slide.
FIG. 7 shows a device in which the adjustment screw or micrometer head is located to the side of the slide.
Magnetic-kinematic adjustments are especially significant for precision vertical motions. Vertical adjustments in precision translating devices present an especially difficult problem. The difficulty lies in balancing out the weight of the object being supported. The principle of this invention solves this problem also, in that it completely removes the effect of the weight.
FIG. 8a, 8b and 8c show the elegant and complete solution for the precision vertical translating stage. The device is coupled with double linear translation motions in the vertical plane, and the entire device is mounted on an optical bench rider (R). The component' to be moved in the vertical direction for example, a lens or mirror (0) hangs from a column (P1). The column has straight guide grooves on both sides, corresponding on one side to guide grooves in the mirror holder (0) and on the other side to guide grooves in a counterweight (P3). The mirror holder and counterweight are suspended from the ends of a metal band (Ml), which hangs over a ball-bearing roller (K) mounted at the top of the column. The mirror can be rotated a full 360 about either the y (horizontal) axis or the z (vertical) axis. The rotational action about the y (horizontal) and z (vertical) axis is made with the help of magnetic-kinematic rotation stages (U P2) and (V) the magnetic attraction between these stages being indicated by arrows m.a. For clarity, the adjusting screws or micrometer heads are not shown in the figure. The coarse vertical adjustment of the optical component is to be made by hand, and the fine adjustment by an ordinary screw or by a micrometer screw. Since the screw must be attached at various heights, it is attached magnetically.
FIG. 9a and 9b show how elegantly the magnetickinematic principle can be applied to a piezoelectrically-controlled translation. Again, an optical example is given. It should be mentioned that in all presently available piezoelectric optical mounts, the piezoelectric transducer is rigidly mounted at one of its ends and supports the optical component at the other end. If the transducer is arranged horizontally, this means a mechanical load on the transducer column, so that the column has a tendency to bend. Such a system becomes complicated when the beam must pass through the system. In this case the transducer is built as a largediameter ring.
The linear translation stage (T1, T2, M) of FIG. 1 is again shown in FIG. 9a and 9b. One end of the piezoelectric transducer (P) is attached to the fixed part (T1) of the translation stage. The upper slide (T2) carries a stub (Z1); against which the translating force of the piezoelectric transducer acts. The end of the piezoelectric transducer which pushes against the stub is provided with a retaining magnet, in order to ensure a contact without mechanical backlash. It is seen from FIG. 9a and 9b that the only mechanical load on the piezoelectric column is a push or pull along its axis, and that the dimensions of this column are completely independent of the optical components. The points labeled x and y are the electrical terminals for the voltage across the piezoelectric transducers.
It is obvious that this principle can also be applied to rotating stages.
1. In an apparatus for precision adjustment comprising a first member, a second member juxtaposed to said first member, antifriction means separating said members, magnetic means urging said members towards each other and means acting between said members to move one member relative to another, said means being magnetically attached to at least one of said members.
2. An apparatus as claimed in claim 1 in which the means acting between said members comprises a micro-moving means and an end of said micromoving means is magnetically attached to said one member.
3. An apparatus as claimed in claim 1 in which there is a base member and said first member is adjustable with respect to the base member by a coarse adjustment means.
4. An apparatus as claimed in claim 2 in which the second member is rotatable with respect to the first member about a vertical axis and said end of the micromoving means acts against a radially extending shoulder on said second member.
5. An apparatus as claimed in claim 2 in which a third member is juxtaposed to said second member with anti-friction means separating said second and third members and magnetic means urging said second and third members together, said third member being rotatable with respect to said second member about a vertical axis, and second micromoving means acting between said second and third members, an end of said second micromoving means acting against a radially extending shoulder on said third member.
6. An apparatus as claimed in claim 5 in which a standard is supported on said third member, a fourth member is supported for vertical adjustment on said standard and a fifth member is juxtaposed to said fourth member for rotational movement with respect thereto, said fifth member being separated from said fourth member by antifriction means and being urged towards said fourth member by magnetic means, and micromoving means acting between said fourth and fifth members.
7. An apparatus as claimed in claim 6 in which said fifth member supports an optical device for rotation about a vertical axis and said fourth member, fifth member and optical device are counterbalanced by a weight supported by flexible means.
8. An apparatus as claimed in claim 7 in which said first member is juxtaposed to a slide member, said first member and slide member being magnetically urged towards each other, micromoving means acting between said slide member and said first member to cause relativ'e movement between them, said slide member being adapted to be adjustably mounted on a track member, the first, second and third members being horizontally positioned plate members vertically stacked on top of said slide member, the first and second members being adjustable by said micromoving means in a direction at right angles to the direction in which the micromoving means adjusts the first member with respect to the slide member.
9. An apparatus as claimed in claim 2 in which said micromoving means is a piezoelectric device.
110. An apparatus as claimed in claim 9 in which there is a base member supporting said first and second members and a micrometer screw acts between said base member and said first member to cause relative movement between them.