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System and method of planar positioningRelated Patent Categories: Geometrical Instruments, Gauge, Collocating, AlignmentSystem and method of planar positioning description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060156569, System and method of planar positioning. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application is a continuation and claims the benefit of priority from copending U.S. Non-Provisional application Ser. No. 10/801,925, filed Mar. 15, 2004, which is incorporated herein by reference, in its entirety and for all purposes. U.S. application Ser. No. 10/801,925 benefits from the priority of now-expired U.S. Provisional Application Ser. No. 60/454,559, filed Mar. 14, 2003, entitled "METHOD OF PLANAR POSITIONING," the disclosure of which is also hereby incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] Aspects of the present invention relate generally to the field of accurately placing one surface with respect to another, and more particularly to a system and method of determining angular deviation from parallel between two surfaces and correcting such deviation. BACKGROUND OF THE INVENTION [0003] In probe card metrology applications, it is often necessary or desirable to know the distance between a flat surface (a "primary" or "principal" surface) and another surface to which a probe card is attached ("reference" surface). A common approach employed by many systems is illustrated in FIG. 1. Specifically, FIG. 1 is a simplified diagram illustrating three views of the structural components employed in a typical probe card metrology system. Platforms A and B are connected or rigidly affixed by three or more legs or vertical structural members; the platforms and the legs form a metrology frame to which other components of the metrology system may be attached during use. A z-stage, such as the exemplary wedge driven z-stage, for example, is attached to platform A. The primary surface is typically attached to the top of this stage, while a reference ring or other structural reference component is attached to the bottom side of platform B. Where a ring is used, the top surface of the reference ring is typically designated as the reference plane, and ordinarily supports a probe card to be analyzed. Through linear horizontal translation of wedge C, wedge D may be driven vertically, thereby translating the primary surface relative to the reference surface. In that regard, a linear scale or encoder (labeled "linear encoder" in FIG. 1) may measure displacement of wedge D relative to platform A. [0004] The lower travel limit of the z-stage may be measured (relative to the reference surface) using a depth indicator, for example, as illustrated in FIG. 2. Specifically, FIG. 2 is a simplified diagram illustrating three views of the structural components employed in a probe card metrology system adapted for use with a depth indicator. Such a depth indicator is typically set in a flat bar spanning the reference ring. By first zeroing or calibrating the depth indicator flush with the flat bar, absolute depth of the primary surface can be measured. Similarly, relocating the depth indicator and taking measurements at three points on the primary surface may allow parallelism to be determined. Any non-parallelism may be removed, for example, by adjusting the pitch, roll, or both, of either the z-stage base, platform A, platform B, or some combination thereof. In the embodiment illustrated in FIGS. 1 and 2, the linear encoder is attached between wedge D and platform A; as noted briefly above, this linear encoder may measure displacement of the wedge relative to the platform. Since the starting height is known from the depth indicator measurements, such measurement of the displacement may allow the final height to be determined. [0005] The Abbe principle dictates, however, that displacement at points away from the linear encoder can only be inferred. Any compression or deflection of components above the linear encoder (such as platform B), for example, is not measured, nor is any deflection or deformation of the reference or primary surfaces, such as due to forces exerted by probes during overtravel. Additionally, current technology can provide no information regarding parallelism degradation. Since only one linear encoder is provided, angular displacement cannot be measured absent complicated and time-consuming relocation of the depth indicator and recalibration. Any dimensional changes to the stiffness loop due to temperature or strain, for example, are typically not considered, and can influence measurement results. [0006] In other words, a displacement of 10 .mu.m as measured by the linear encoder in a conventional system does not guarantee uniform, one-dimensional translation of the principal plane relative to the probe card of that 10 .mu.m distance. In that regard, measurement accuracy is a function of the rigidity of the structural components of the system, the trueness of stage travel, the stability of the metrology frame, and other factors which are not taken into account by conventional metrology methods and technologies. SUMMARY [0007] Aspects of the present invention overcome the foregoing and other shortcomings of conventional technology, providing a system and method of controlling the relationship between two surfaces and correcting any deviation from the desired or ideal relationship. Exemplary systems and methods may generally comprise a plurality of linear actuators which may be driven in unison or independently. [0008] In accordance with one embodiment, for example, a method of controlling the relationship between a primary surface and a reference surface in a probe card analysis system may comprise: defining the reference surface at a selected point on a metrology frame; attaching a plurality of linear actuators to the metrology frame; coupling a platform supporting the primary surface to each of the plurality of linear actuators; and controlling the relationship between the primary surface and the reference surface utilizing the plurality of linear actuators. In some exemplary embodiments, the coupling comprises utilizing a flexural assembly between the platform and each of the plurality of linear actuators. [0009] For linear motion, the controlling comprises driving each of the plurality of linear actuators in unison; for pitch and roll control, for example, the controlling comprises driving one of the plurality of linear actuators independently. In that regard, methods are set forth herein wherein the controlling comprises dynamically controlling an angular orientation between the primary surface and the reference surface, and wherein the controlling comprises dynamically compensating for changes in shape of structural elements of the metrology system, such as a probe card analysis system, for example. In accordance with the present disclosure, the controlling generally comprises determining a distance between the primary surface and the reference surface at one or more selected locations on the platform supporting the primary surface; such determining may comprise utilizing a linear encoder at the one or more selected locations, and the controlling may additionally comprise feeding distance information back to the plurality of linear actuators. [0010] In accordance with another exemplary embodiment, a metrology system may comprise: a metrology frame having one or more vertical structural members; a plurality of linear actuators attached to the frame; and a platform supporting a primary surface; wherein the platform is coupled to each of the plurality of linear actuators. As with the method noted above, one system may comprise a respective flexural assembly attached to each of the plurality of linear actuators and coupling a respective linear actuator to the platform. In particular, each respective flexural assembly may be operative to minimize lateral cross-coupling between the plurality of linear actuators. [0011] A metrology system as set forth in detail below may further comprise a respective linear encoder associated with each of the plurality of linear actuators. Each respective linear encoder is generally operative to acquire distance information representing a distance between the primary surface and a reference surface. The plurality of linear actuators may be driven in unison responsive to the distance information; alternatively, one of the plurality of linear actuators may be driven independently responsive to the distance information. [0012] In one embodiment, each of the plurality of linear actuators is attached to a respective one of the one or more vertical structural members of the frame. [0013] The foregoing and other aspects of the disclosed embodiments will be more fully understood through examination of the following detailed description thereof in conjunction with the drawing figures. BRIEF DESCRIPTION OF THE DRAWINGS [0014] FIG. 1 is a simplified diagram illustrating three views of the structural components employed in a typical probe card metrology system. [0015] FIG. 2 is a simplified diagram illustrating three views of the structural components employed in a probe card metrology system adapted for use with a depth indicator. [0016] FIG. 3 is a simplified diagram illustrating three views of one embodiment of a metrology system constructed and operative in accordance with the present disclosure. [0017] FIG. 4 is a simplified diagram illustrating two views of a flexural assembly constructed and operative in accordance with the present disclosure. DETAILED DESCRIPTION [0018] As set forth in more detail below, a metrology system and method are disclosed which enable the coplanarity of the primary surface and the reference surface to be controlled by a plurality of actuators; in some instances, flexural assemblies supporting the reference surface (i.e., coupling the reference surface and the actuators) may minimize lateral cross-coupling between the plurality of actuators. In particular, the actuators may be used dynamically to compensate for changes (e.g., in shape or orientation) of the reference surface or of the metrology frame due to environmental changes such as temperature; compensation in this context may include compensating for relative pitch, roll, or both between the reference surface and the primary surface. It will be appreciated that a system and method configured and operative in accordance with the present disclosure enable the actuators to stabilize the positioning of the primary surface relative to the reference surface even under dynamic loading conditions. Continue reading about System and method of planar positioning... Full patent description for System and method of planar positioning Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this System and method of planar positioning patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like System and method of planar positioning or other areas of interest. ### Previous Patent Application: Generation of guidance line or lines Next Patent Application: Credit card-shaped tire tread gauge Industry Class: Geometrical instruments ### FreshPatents.com Support Thank you for viewing the System and method of planar positioning patent info. 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