Patent Application
20090206229
1. Field of the Invention
This invention relates to an apparatus and method for isolating vibrations that affect subsystems within optical measurement and/or imaging systems or equipment.
2. Discussion of Related Art
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.
DEI is a radiographic technique that derives contrast from an object'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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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
In the embodiment shown in
In the embodiment of the invention shown in
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
The vibration dampening elements 40, 42 are not intended to be limited to any particular dampening mechanism. In the embodiment shown in
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.
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.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 61065916 | Feb 2008 | US |
