Abstract:
An apparatus and method for vibrationally isolating two or more interconnected or mechanically cooperating imaging subsystems. A first of the subsystems can be an optics subsystem that includes optical components and other structural or mounting hardware for the optical components. A second of the subsystems can include, for example, an x-ray source, the object to be studied, and/or a detector. The apparatus includes at least two interconnected or mechanically coupled vibration isolation platforms. A component of the first of the subsystems is placed or mounted on one of the vibration isolation platforms and a component of the second of the subsystems is placed or mounted on the other of the vibration isolation platforms.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application, Ser. No. 61/065,916, filed on 15 Feb. 2008. The co-pending Provisional Patent Application is hereby incorporated by reference herein in its entirety and is made a part hereof, including but not limited to those portions which specifically appear hereinafter. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to an apparatus and method for isolating vibrations that affect subsystems within optical measurement and/or imaging systems or equipment. 
         [0004]    2. Discussion of Related Art 
         [0005]    The apparatus and method of this invention can be used with and generally relates to but is not limited to Diffraction Enhanced Imaging (DEI) systems, for example those taught by Chapman et al., U.S. Pat. No. 5,987,095 and Chapman et al., U.S. Pat. No. 6,577,708 and Wernick et al., U.S. Pat. No. 7,076,205. The apparatus and method of this invention can also be used, for example, to practice the crystal and imaging technology taught by Zhong et al., U.S. Pat. No. 6,038,285. 
         [0006]    DEI is a radiographic technique that derives contrast from an object&#39;s x-ray absorption, refraction and ultra-small-angle scattering properties. DEI can be used to detect, analyze, combine and visualize the refraction, absorption and scattering effects upon an image of an object. DEI is particularly useful for relatively thick and thus highly absorbing materials. Compared to the absorption contrast of conventional radiography, the additional contrast mechanisms, refraction and scatter, of DEI allow visualization of more features of the object. 
         [0007]    DEI can use highly collimated x-rays prepared by x-ray diffraction from perfect single-crystal silicon. These collimated x-rays are of single x-ray energy, practically monochromatic, and are used as the beam to image an object. The collimated x-rays are prepared by two silicon crystals of a monochromator. Once this beam passes through the object, another crystal of the same orientation and using the same reflection is introduced. This crystal is commonly called an analyzer. If this analyzer crystal is rotated about an axis, the crystal will rotate through a Bragg condition for diffraction and the diffracted intensity will trace out a profile that is called a rocking curve. At least two images are obtained by a detector at different angled positions, for example, one at each of the low and high angle sides of the rocking curve, of the crystal analyzer. The images are mathematically combined to obtain images, such as a refraction angle image. 
         [0008]    The width of the rocking curve profile is typically a few microradians wide, for example 3.6 microradians within a full width of half maximum (FWHM) at 18 keV using a silicon (3, 3, 3) reflection. As with other radiographic imaging techniques, it is desirable to reduce or eliminate vibration throughout the system. Vibrations can be reduced by positioning the optics components or optical elements on a rigid vibration isolation platform, such as a single platform vibration isolation system that is commercially available from Kinetic Systems, Inc. (Boston, Mass.). Such vibration isolation systems may not be sufficient to hold or maintain a relative position of the imaging crystals, in order to obtain a successful overall performance for the entire machine or the entire system. There is an ongoing need for vibration-reducing optical tables to support imaging systems such as a DEI system. 
       SUMMARY OF THE INVENTION 
       [0009]    One object of this invention is to provide an apparatus and method of use for mechanically isolating, particularly isolating vibrations within, two or more interconnected or mechanically cooperating subsystems. 
         [0010]    A first of the subsystems can be an optics subsystem that includes optical components and other structural or mounting hardware for the optical components. A second of the subsystems can include, for example, an x-ray source, the object to be studied, and/or a detector. In order to obtain successful results when using the entire system, during the method steps of this invention or during the experiments, both the first subsystem and the second subsystem should be stable, at least within themselves or each subsystem. Vibrations or other undesired forces caused by outside or external sources can be eliminated or minimized at least to the extent of not affecting performance of the subsystems. Instabilities or undesired vibrations or forces within any one or more of the subsystems can degrade the overall machine performance. 
         [0011]    In certain embodiments of this invention, in the second subsystem, the components or elements, for example in a DEI machine or other optics system, an x-ray source, a sample holder, and/or a detector are kept or maintained at a precise spatial relationship or three-dimensional position with respect to each other. In order to maintain the precise spatial relationship or position with respect to each other, the components should be essentially free from and not moved by instabilities and/or vibrations induced from inside of or within each subsystem and/or from a surrounding environment or an outside vibration or instability. Thus, in certain embodiments of this invention, the components of each subsystem are placed or mounted on a separate, independent or individual vibration isolation platform, such as a rigid platform or mounting structure. 
         [0012]    In some embodiments of this invention, both the x-ray source and/or the detector themselves can produce vibrations and instabilities, for example due to water cooling and other similar system functions. Even though the second subsystem may be rigid enough to provide a solid base to assure precise relative spatial relationship between the components of each subsystem, the vibrations created by the second subsystem components should also be prevented from propagating through the remainder of the system. If vibrations or instabilities are allowed to propagate to the first subsystem with the optics elements, then the source and/or the detector induced vibrations can significantly degrade or reduce the overall machine performance. 
         [0013]    In certain embodiments of this invention, to prevent undesired vibrations and/or instabilities, the second subsystem is mechanically decoupled from or independent with respect to the first subsystem, and also does not receive vibrations and/or instabilities of the surrounding environment or the outside world that would affect the performance of the overall system. In some embodiments, the second subsystem, for example as applied to DEI, is inherently bigger in size than the first subsystem and the source can be at one end of the machine or system and the detector can be at the opposite end or relatively far away from the detector. Also, the sample holder can be part of the second subsystem and positioned between the optics components. Thus, a known single platform optical table, such as those that are commercially available, cannot be used to hold the second subsystem, for example in a DEI system. 
         [0014]    In certain embodiments of this invention, a vibration isolation system comprises at least two interconnected, intertwined and/or mechanically coupled vibration isolation platforms. In each of the subsystems, the unintended interconnected or inter-component motions or vibrations should be significantly reduced while the collective motions or group motions of all of the subsystems can be tolerated to a much higher degree. Thus, with certain embodiments of this invention, the components and subsystems can move simultaneously, such as together as a whole or entire system because such entire movements, vibrations and/or instabilities of all of the subsystems will not noticeably degrade the overall system performance, as long as the components preserve or maintain their spatial relationships or three-dimensional positions within a subsystem. 
         [0015]    In some embodiments, this invention comprises at least two independent vibration isolation tables or platforms working or cooperating together as an integrated or a structurally connected system. In some embodiments, an inner subsystem is within an area defined by a corresponding outer subsystem. The inner subsystem, for example, can comprise a conventional optical table. The outer subsystem, for example, can comprise a rigid bracket or other suitable structural member, completely surrounding the inner table or platform along or about a periphery of the inner vibration isolation table. At some point along and at equal distances from opposing edges there can be a rigid sample support bracket, which is part of the outer vibration isolation table. The position of the bracket can be selected to place or position the sample in the pathway of the x-ray beam and between two of the optical components. 
         [0016]    The general object of the invention can be attained, at least in part, through a vibration isolation apparatus for optical measuring or imaging systems. The apparatus includes a first vibration isolation platform and a second isolation platform. The second isolation platform is mechanically disconnected or decoupled from the first vibration isolation platform. By supporting the first subsystem discussed above with the first vibration isolation platform and the second subsystem discussed above with the second vibration isolation platform, each of the two subsystems can be further isolated from any vibrations caused by the other. 
         [0017]    Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a partial sectional front view of a vibration isolation apparatus according to one embodiment of this invention. 
           [0019]      FIG. 2  is a sectional perspective view of the apparatus of  FIG. 1 . 
           [0020]      FIG. 3  is a top view of the apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    In one embodiment of this invention an apparatus is provided for mechanically isolating, particularly isolating vibrations within, two interconnected or mechanically cooperating subsystems. An exemplary first of the cooperating subsystems can be an optics subsystem wherein the optics components are maintained at a very precise spatial relationship or fixed position with respect to each other. Thus, the optical components should be essentially free from vibrations and other instabilities or external forces, for example inter-component instabilities caused by other machine components or external vibrations from a surrounding environment or the outside world. 
         [0022]      FIGS. 1-3  illustrate a vibration isolation apparatus  10  for use with optical measuring or imaging systems, such as the DEI systems discussed in Chapman et al., U.S. Pat. No. 5,987,095, Chapman et al., U.S. Pat. No. 6,577,708, and Zhong et al., U.S. Pat. No. 6,038,285, the teachings and disclosure of each of are incorporated into this specification by reference to such United States Patents. The vibration isolation apparatus  10  includes a support structure  12  supporting two interconnected or mechanically coupled vibration isolation platforms. The two vibration isolation platforms  14 ,  16  are kept or maintained mechanically disconnected or decoupled from each other and are also kept or maintained interconnected, intertwined or mechanically cooperating with each other through the independent connection of each platform  14 ,  16  to the support structure  12 . 
         [0023]    The two vibration isolation platforms  14 ,  16  can be made from materials currently used in commercial optical tables. For example, one or both of the vibration isolation platforms  14 ,  16  can be or include an optical breadboard, such as a hexagon cell steel honeycomb core structure below a top plate. The honeycomb structure can be used to impart high stiffness and a structurally efficient light weight, ultimately resulting in a significantly high natural frequency and less vibration than other materials such as solid granite or cast iron structures. On top of the honeycomb structure is, for example, a ferromagnetic stainless steel plate. Other materials for encasing the honeycomb structure (e.g., for a top, bottom layer and/or sides) include carbon steel; a high shear modulus, corrosion-resisting, plated steel; and/or an epoxy or other polymer. As shown in  FIGS. 1-2 , the second platform  16  is formed of a single layer steel plate. One or more of the isolation platforms  14 ,  16  can include a grid of threaded mounting holes (e.g., ¼ inch or M6 threaded holes) which allow the components to be bolted down to the platform so they cannot move even a few nanometers. 
         [0024]    The support structure  12  can be similarly formed from known materials. Desirably the support structure  12  is formed from a rigid material such as steel. The support structure  12  is shown as a dedicated worktable support having legs  44  in the embodiment of  FIGS. 1-2 , but the invention is not so limited. The support structure can alternatively be an existing or dual-use table. The support structure can also be formed as a planar support structure that allows the apparatus of this invention to be formed as, for example, a leg-less breadboard for placement on an existing surface. The isolation platforms can be fixed to the support structure or removable, and/or the support structure can be designed to be further attachable to another structure (e.g., a floor or table). 
         [0025]    The second vibration isolation platform  16  is held adjacent to and vibrationally isolated from the first vibration isolation platform  14 . The second vibration isolation platform  16  is desirably held adjacent to at least a first end of the first vibration isolation platform  14 . In one embodiment of this invention, as shown in  FIGS. 1-3 , the second vibration isolation platform  16  extends around and/or above a peripheral edge  18  of the first vibration isolation platform  14 . The second vibration isolation platform  16  can have an inner edge portion that overlaps, is aligned with, or is laterally spaced apart from a portion of inner isolation platform. In  FIGS. 1-3 , the inner edge portion  20  of the second vibration isolation platform  16  is generally aligned with, but not overlapping, and above, e.g., spaced apart in a vertical direction from, the peripheral edge  18 . 
         [0026]    In the embodiment shown in  FIGS. 1-3 , the first vibration isolation platform  14  is formed as an inner platform to which components of a first subsystem are secured, and the second vibration isolation platform  16  is formed as an outer platform to which components of a second subsystem are secured. The size, shape, and/or configuration of the vibration isolation platforms can vary depending on need, which can be dependent on the type and number of components needed to be secured to or by the apparatus. For example, instead of extending around the inner platform, the outer platform can alternatively be formed as two separate platforms or platform portions disposed at the opposing ends of the inner platform. 
         [0027]    In the embodiment of the invention shown in  FIGS. 1-3 , the second isolation platform  16  includes a first platform portion  22  adjacent to a first end  24  of the first vibration isolation platform  14  and a second platform portion  26  adjacent to a second end  28  of the first vibration isolation platform  14  that is opposite of the first end  24 . The second isolation platform  16  includes at least one side portion  25  that extend along a side edge of the inner platform  14  to connect the first platform portion  22  with the second platform portion  26 . The vibration isolation apparatus  10  includes an optional sample support  30  extending from one side portion  25 , and optionally between two side portions  25 , of the second isolation platform  16 . The sample support  30  extends over the first isolation platform  14 . 
         [0028]    In certain embodiments of this invention, the inner platform and/or the outer platform is independently actively supported by suitable mechanical, electrical, magnetic and/or any other suitable element that provides vibration isolation support. For example, the cut-away view of  FIGS. 1-2  illustrate a system according to one embodiment of this invention, in which first vibration dampening elements  40  are disposed between the support structure  12  and the first vibration isolation platform  14  and/or second vibration dampening elements  42  are disposed between the support structure  12  and the second isolation platform  16 . 
         [0029]    The vibration dampening elements  40 ,  42  are not intended to be limited to any particular dampening mechanism. In the embodiment shown in  FIGS. 1-2 , vibration dampening elements  40 ,  42  are shown as independent vibration eliminating cylinders, such as electrically, pneumatically or hydraulically operated cylinders. Each of these vibration eliminating cylinders is positioned near and mechanically coupled or operatively connected to each corresponding vibration isolation platform. In the particular embodiment of apparatus  10 , one of the first vibration dampening elements  40  is disposed on each leg  44  of support structure  12  and between the corresponding leg  44  and a corner of the first vibration isolation platform  14 . Each of the second vibration dampening elements  42  is connected to one of the legs  44  of support structure  12  by a bracket  46 . In this arrangement, each subsystem corresponding with each vibration isolation platform is supported by a separate and independent vibration dampening mechanism, and moves completely independently from the other subsystem. 
         [0030]      FIGS. 1-3  also illustrate the use of the apparatus  10  for supporting and mechanically and vibrationally isolating two interconnected or mechanically cooperating optical measuring or imaging subsystems. A first of the subsystems includes as optical components monochromator crystals  50  and analyzer crystal  52 . A second of the subsystems includes a radiation source  56  and a detector  58 . Each of the optical components is secured to the first vibration isolation platform  14 . The second isolation platform  16  extends around the inner platform  14 , thereby providing the first platform portion  22  for the radiation source  56  and the second platform portion  26  for the detector  58 . The sample support  30  is formed as a part of the second vibration isolation platform  16 , and thus the sample  60  thereon is considered part of the second subsystem. 
         [0031]    By placing the optical components  50 ,  52  on the inner platform  14  between the radiation source  56  and the detector  58  of the outer platform  16 , the two subsystems are vibrationally isolated from each other. In this component arrangement, vibrations or other undesired forces caused by outside or external sources can be eliminated or minimized at least to the extent of not affecting performance of the subsystems. In addition, instabilities or undesired vibrations or forces within any one or more of the subsystems can also be eliminated or minimized at least to the extent of not affecting performance of the subsystems. Thus, the invention provides a vibration isolation apparatus for use in interconnecting or mechanically coupling, while at the same time vibrationally isolating, components of optical measuring or imaging systems. 
         [0032]    The invention illustratively disclosed herein suitably may be practiced in the absence of any element, part, step, component, or ingredient which is not specifically disclosed herein. 
         [0033]    While in the foregoing detailed description this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.