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Vacuum chamber with recessed viewing tube and imaging device situated thereinVacuum chamber with recessed viewing tube and imaging device situated therein description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060193037, Vacuum chamber with recessed viewing tube and imaging device situated therein. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This document concerns an invention relating generally to vacuum chambers, and more specifically to vacuum chambers wherein items are to be subjected to testing, analysis, and/or imaging. BACKGROUND OF THE INVENTION [0002] When performing operations on objects situated within ultra-high vacuum chambers (UHV chambers), it is often useful to be able to obtain images of the shape and position of the objects. As an example, in the case of an atom probe microscope having a local extraction electrode situated within a UHV chamber, the specimen to be analyzed--which is often provided in the form of a sharp tip--is best analyzed if it is precisely aligned within the aperture of the local electrode (which is generally 1-1000 micrometers in diameter). It is additionally useful to be able to view the specimen's shape and status as experiments are performed. [0003] However, obtaining a suitable view of the specimen with an optical microscope, digital camera, and/or other imaging device can be difficult to achieve. The UHV chambers, which must necessarily have sturdy construction, are generally made of metal with one or more access ports provided over a small area of the chamber walls, with the specimens being centrally located within the chambers to allow greater room to operate on the specimens. The access ports provide limited ability to view the specimen and ascertain its position and status; their distance from the specimen is such that it is difficult to view details of the specimen (even if high-powered optics are used), and additionally they each provide a very limited cone of vision about the specimen (i.e., one may generally see only one primary face of the specimen and very limited views of the sides of the specimen located off of the primary face). It is therefore generally unsatisfactory to optically image a specimen from an access port, since it is extremely difficult to obtain a view of the specimen having resolution in the ideal range (from 10 micrometers down to the sub-micrometer level), and to obtain sufficient views from points orbiting the specimen that one may effectively obtain more than a two-dimensional view of the specimen. As a result, optical imaging devices are generally only employed to obtain very coarse information regarding the position and status of the specimen. [0004] Another approach, as illustrated in U.S. Pat. No. 5,940,175 to Sun, is to provide a windowed accessory vacuum chamber situated outside the main vacuum chamber, and to transport the specimen to be viewed to and from the accessory chamber (in which the specimen is viewed). The accessory chamber can be made shallow so that the window (and any imaging device situated outside the window) is situated close to the specimen. However, this approach does not address the need to closely view the specimen within the main vacuum chamber itself. A further disadvantage of this approach is that it can be difficult and expensive to provide efficient transport mechanisms for moving the specimen from one chamber to another. [0005] Owing to the foregoing problems, specimen position/status information within the vacuum chamber is often provided by use of indirect measurements. As an example, in the case of atom probe microscopes, measurements of transmitted or backscattered current (as discussed in U.S. Pat. No. 5,440,124 to Kelly et al.), or of the desorption rate of ions from the specimen (U.S. Pat. No. 5,061,850 to Kelly et al.), can indicate specimen location and orientation. However, these methods are only useful if the specimen is already aligned to some degree within the aperture of the microscope. Therefore, imaging is usually performed with use of scanning electron microscopes (SEMs) situated inside the chambers, since these can obtain submicron resolution of specimen position and status from relatively long working distances (i.e., with greater spacing between the SEM and the specimen). [0006] However, while this well-accepted arrangement provides good information, it too is less than ideal. Initially, it is expensive to provide and maintain a SEM. Additionally, in order to establish high vacuum within UHV chambers, the chambers must undergo a heating or "baking" process in order to drive off volatile molecules each time the chamber is opened to the atmosphere. SEMs have components that cannot withstand baking, and therefore portions of the SEMs must be removed prior to each bake cycle and then replaced after the bake cycle is complete. Since SEM components are sensitive and bulky, removal and replacement of SEM components is inconvenient and time-consuming. It would therefore be extremely useful to be able to obtain images of areas within the chambers which have suitable resolution and angular spread without having to resort to use of a SEM. SUMMARY OF THE INVENTION [0007] The invention involves a vacuum chamber which is intended to at least partially solve the aforementioned problems. To give the reader a basic understanding of some of the advantageous features of the invention, following is a brief summary of preferred versions of the vacuum chamber. As this is merely a summary, it should be understood that more details regarding the preferred versions may be found in the Detailed Description set forth elsewhere in this document. The claims set forth at the end of this document then define the various versions of the invention in which exclusive rights are secured. [0008] A vacuum chamber includes chamber walls separating a chamber interior and a chamber exterior, with one or more access ports defined in the chamber walls. A viewing tube having a flange removably affixed to an access port provides a passage extending into the chamber interior and terminating in an at least partially transparent window. The viewing tube may therefore be installed on a vacuum chamber port by removing any standard cap situated on the access port, and inserting and affixing the viewing tube in place of the cap. [0009] A positioner for imaging devices is then provided within the viewing tube, and is thus situated at least partially within the chamber interior with its imaging device(s) oriented towards the window of the viewing tube to allow imaging of areas within the vacuum chamber. A preferred version of the imaging device positioner includes an arcuate track which has a center of curvature situated within the vacuum chamber interior and which is fixed with respect to the access port, with a positioner carriage being movable along the track. The positioner carriage preferably bears wheels engaging opposing sides of the track, as well as a pinion which engages teeth on the track and which may therefore be actuated to drive the carriage along the track. A positioner subcarriage which bears an imaging device is then movably affixed to the positioner carriage, preferably so that it may be repositioned in a first plane oriented at least substantially perpendicular to the carriage plane and a second plane oriented at least substantially parallel to the carriage plane. The positioner subcarriage may be made repositionable with respect to the positioner carriage by extending one or more threaded members therebetween so that rotation of the threaded member(s) drives the positioner subcarriage with respect to the positioner carriage. [0010] With the viewing tube and imaging device positioner installed, a user may use the imaging device positioner to reorient an imaging device within the viewing tube (and thus within the vacuum chamber interior) to very precisely direct it towards an area of interest within the chamber. Since the imaging device may be situated within the chamber interior very close to the area of interest for imaging and may be repositioned therein, the imaging device may obtain views of the area of interest within a greater viewing cone (i.e., along lines of sight separated by greater angles) than the imaging device would otherwise be able to achieve were it situated outside the vacuum chamber. Additionally, since the viewing tube rests along the same line of sight that the imaging device would require were it situated outside the vacuum chamber, the viewing tube does not unnecessarily occupy or obstruct valuable space within the chamber interior (since such line of sight must necessarily remain unobstructed in any event if the imaging device is to view the area of interest). [0011] Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a perspective view of a vacuum chamber 100 (shown with its chamber walls 104 partially cut away) having a specimen-bearing positioning stage 106 therein, with the vacuum chamber 100 bearing versions of viewing tubes 200 and imaging device positioners 300 which exemplify the invention. [0013] FIG. 2 is a top perspective view of the imaging device positioner 300 of FIG. 1 shown with the viewing tube 200 and vacuum chamber 100 partially cut away. [0014] FIG. 3 is an elevational view of one end of the imaging device positioner 300 of FIGS. 1 and 2, shown with the flange 204 of the viewing tube 200 being visible. [0015] FIG. 4 is a bottom perspective view of the imaging device positioner 300 of FIG. 1 shown with the viewing tube 200 partially cut away. DETAILED DESCRIPTION OF PREFERRED VERSIONS OF THE INVENTION [0016] Referring to FIG. 1, an exemplary vacuum chamber 100 is provided with a number of standard access ports 102 situated on or outside the walls 104 of the vacuum chamber 100, i.e., the entryways of the access ports 102 are situated on or outside the general "envelope" that would be defined by the walls 104 of the vacuum chamber 100 if the access ports 102 were not present. Such standard access ports 102, which are usually clustered about an area of interest within the vacuum chamber 100 (here about a positioning stage 106), extend from the chamber walls 104 to terminate in flanges 108 having a number of attachment apertures 110 circumferentially spaced thereabout to allow attachment of structures to the flanges 108. As an example, a cryostat 112 is shown connected to the vacuum chamber 100 via an intermediate extension tube 114, with this extension tube 114 being affixed to one of the access ports 102. As another example, window-bearing caps 116, with cameras or other imaging devices 118 mounted thereon, may also be affixed to the access ports 102 (with two such caps 116 and imaging devices 118 being shown in FIG. 1). [0017] Such imaging devices 118 are situated distantly from the area of interest 106 of the vacuum chamber 100, and therefore have limited ability to view, magnify, and/or image any objects in the area of interest 106 unless expensive high-magnification optics are used. Additionally, since they have a somewhat limited view of the interior of the vacuum chamber 100, a common approach is to provide multiple imaging devices 118--as depicted in FIG. 1--each situated at a different one of the access ports 102 of the vacuum chamber 100, to allow different areas of the interior of the vacuum chamber 100 to be viewed at different angles. While this provides a simple means of viewing the area of interest 106 from different angles, it can lead to greater expense owing to the need for multiple imaging devices 118. Additionally, if an item of interest 106 is repositioned within the vacuum chamber 100, the user must generally undertake a time-consuming (and annoying) repositioning and refocusing of each one of the imaging devices 118 at the various access ports 102 in order to obtain properly centered and focused views. [0018] The vacuum chamber 100 is also illustrated with an exemplary version of the invention: an inwardly-extending viewing tube 200, and a imaging device positioner 300 mounted to position an imaging device within the viewing tube 200 for close-range imaging of objects within the interior of the vacuum chamber 100. Both the viewing tube 200 and the imaging device positioner 300 will now be discussed in turn in greater detail with reference to FIGS. 2-4. [0019] Looking initially to FIG. 2, the viewing tube 200 includes an elongated tube 202 extending into the interior of the vacuum chamber 100 between a terminal tube flange 204 and a terminal tube window 206 (with such structure also being illustrated in FIG. 4 with the vacuum chamber 100 removed). The tube flange 204 is a standard vacuum flange bearing a number of fastener apertures 208 allowing its fixture to a flange 108 bounding an access port 102 on the vacuum chamber 100, though the flange 204 may take a variety of other forms different from the one depicted in the drawings. Similarly, the viewing tube 200, while shown as including a number of segments (see particularly FIG. 4)--an initial large-diameter cylindrical segment 210, an intermediate frustoconical segment 212, and a final small-diameter segment 214--may be differently configured with less or more segments of varying sizes; for example, it could instead simply take the form of a cylindrical tube. However, the tube 200 is preferably necked down from the tube flange 204 to a smaller-diameter window 206 since a smaller-diameter window 206 may sustain a greater pressure difference between the interior of the chamber 100 and the external atmosphere, and may therefore maintain seal integrity for a longer period of time, at lower cost. The window 206 is preferably a flat glass having low reflection and refraction, and also having a circumferential flange 216 (FIG. 2) protruding from one of its faces wherein the end of the tube 200 may be embedded/fused. Since the area of the window 206 is relatively low, the air pressure on the outside of the window 206 exerts low force across the area of the window 206 when vacuum conditions are present within the chamber 100, and thus the fused region of the window 206 about the flange 216 need not be made so bulky (for sake of strength) that excessive space is consumed within the chamber 100. Non-fused designs (i.e., designs wherein the window 206 rests within a seal at the end of the tube 200) are also possible, with such designs preferably taking into account the fact that the window 206 will be pushed away from the end of the tube 200 by atmospheric pressure rather than into it, as will occur with designs for standard access port caps which bear windows (in other words, sealing arrangements are reversed from the standard arrangement). Continue reading about Vacuum chamber with recessed viewing tube and imaging device situated therein... Full patent description for Vacuum chamber with recessed viewing tube and imaging device situated therein Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Vacuum chamber with recessed viewing tube and imaging device situated therein patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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