Vacuum chamber with recessed viewing tube and imaging device situated therein
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 extends from the chamber exterior into the chamber interior and terminates in a window. 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. The positioner preferably allows translation and/or rotation of an imaging device within the viewing tube within two perpendicular planes oriented along the axis of the viewing tube, thereby allowing the imaging device to view an area of interest from more angles oriented about the area of interest than would otherwise be possible if the imaging device was situated outside the vacuum chamber.
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 INVENTIONWhen 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.
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.
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.
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).
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 INVENTIONThe 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.
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.
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.
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).
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
Referring to
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
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
Looking initially to
Referring then particularly to
Referring particularly to
Also referring to
The positioner subcarriage 310, to which the camera 304 is firmly affixed (as previously noted), is then made adjustable in certain directions with respect to the positioner carriage 308. Initially, a coplanar pan knob 336 is provided which allows the positioner subcarriage 310 to be adjusted in a plane parallel to the carriage plane (i.e., the plane in which the positioner carriage 308 travels upon rotation of the eucentric pan knob 332) and along a direction oriented generally tangentially to the arc of travel defined by the rack 312. As best seen in
A spacing pan knob 342 is also provided to allow the positioner subcarriage 310 to be adjustably spaced with respect to the positioner carriage 308. Looking to
In the foregoing arrangement, mounting of the threaded rod 338 of the coplanar pan knob 336 within the slot (not shown) in the mounting plate 340 allows the spacing pan knob 342 to adjust the spacing of the positioner subcarriage 310 without interference. Similarly, since the threaded rod 344 of the spacing pan knob 342 extends through slot 346 (
Thus, to summarize the foregoing: the eucentric pan knob 332 of the imaging device positioner 300 allows the camera 304 and microscope 302 to be resituated along different lines of sight directed towards a point within the vacuum chamber 100, while the coplanar pan knob 336 and spacing pan knob 342 allow the location of the point to be adjusted. When combined with the viewing tube 200—which effectively extends the microscope 302 and camera 304 within the interior of the vacuum chamber 100—a user may very precisely direct the microscope 302 and camera 304 to a point of interest within the vacuum chamber 100 for viewing and/or imaging. (Note that throughout this document, when it is stated that the viewing tube 200, microscope 302, camera 304, and/or other imaging device is situated inside or within the interior of the vacuum chamber 100, this is meant in the sense that they are within the envelope generally defined by the vacuum chamber walls 104, but they are not within the vacuum itself, much in the same sense that one might say their hand is within their jacket when inserted into a jacket pocket. In other words, this language refers to the imaging device being within, but separated from, the interior of the vacuum chamber 100.)
Since the microscope 302 is effectively situated within the vacuum chamber 100 when it extends within the viewing tube 200 (and is thus difficult to reach), it is also useful to provide some means for allowing remote focusing of the microscope 302 while it extends within the viewing tube 200. An exemplary arrangement for providing remote focusing will now be described with particular reference to
Initially, the remote focusing means 400 includes an adjustment base 402 affixed to the camera 304. As previously noted, the camera 304 preferably bears threaded attachment holes (not shown) to allow its attachment to a tripod or the like, and such attachment holes (if provided) may be used to effect such attachment. The adjustment base 402 bears a pair of eyes 404 extending from threaded rods 406 (
It can also be useful to provide some means for illuminating the area viewed by the microscope 302 and camera 304 within the vacuum chamber 100. Looking to
Thus, to summarize, when it is desirable to obtain a particularly close view of an area within a standard vacuum chamber 100, its access port caps 116 may be removed from one or more of its access ports 102 and viewing tubes 200 may be inserted and installed in their place, with the viewing tubes 200 being oriented towards the area(s) of interest. Imaging device positioners 300 may then be installed at these viewing tubes 200 to precisely direct imaging devices towards the area(s) of interest, allowing users to image the area(s) of interest more closely, accurately, and easily than in the conventional arrangement where imaging devices are situated outside the vacuum chamber 100.
Note that an exemplary preferred version of the invention was described above and shown in the drawings merely to illustrate possible features of the invention. The invention can adopt forms having widely different configurations and components than those discussed above, and modifications which are not excluded from the invention by the claims set forth below are also considered to be within the scope of the invention. Following is an exemplary list of some potential modifications.
First, it is emphasized that the viewing tube 200 and/or imaging device positioner 300 may be used with vacuum chambers having a wide variety of configurations other than the one depicted (for example, having fewer or greater access ports 102 having different sizes and configurations). It should similarly be appreciated that the viewing tube 200 might in some instances be used without the imaging device positioner 300, and conversely the imaging device positioner 300 might be used without the viewing tube 200. As an example, in some instances it might be useful to simply closely monitor the interior of the vacuum chamber 100 without the need to image a precise area therein, in which case an imaging device could simply be situated within the viewing tube 200 without any means for reorienting its line of sight. As another example, if it is not necessary to view a certain area within the vacuum chamber 100 with high resolution, the imaging device positioner 300 may be adapted for use with a standard vacuum chamber viewport—one having a window situated outside the vacuum chamber 100—so that the imaging device positioner 300 may adjustably reposition an imaging device situated entirely outside the vacuum chamber 100.
Second, while the imaging device used within the viewing tube 200 was depicted as including a conventional microscope 302 and camera 304, it should be understood that the invention may use fewer, greater, or other imaging devices. For example, only a microscope 302 or a camera 304 might be used, or an imaging device for detecting electromagnetic spectra outside the visible range (e.g., infrared, ultraviolet, or X-ray spectra) might be used.
Third, keeping in mind that the imaging device positioner 300 may be used to focus an imaging device on areas as small as the millimeter (or even sub-millimeter) scale, it is useful to introduce means for reducing backlash so that the imaged area does not shift or “jump” as a user adjusts one or more of the eucentric pan knob 332, coplanar pan knob 336, and/or spacing pan knob 342. As one example, to better eliminate backlash between the carriage pinion 330 and the toothed face 318 of the engagement bar 316 of the rack 312, it is useful to make at least some of the wheels 326 eccentric, or to otherwise introduce friction between the rack 312 and carriage 308.
Fourth, it is noted that numerous alterations can be made to the preferred version of the imaging device positioner 300 described above without departing from the spirit and scope of the invention. As one example, the linear actuation effected by the coplanar pan knob 336 and its threaded rod 338, and the spacing pan knob 342 and its threaded rod 344, may be effected by other forms of linear actuators (e.g., electromagnetic positioning stages). As another example, the springs 348 and 350 need not take the form of helical springs, and may instead take the form of leaf springs, springs made of strips, blocks, or other structures made of elastomeric or other resiliently flexible materials, or other forms. As still another example, the positioner carriage 308 need not be carried on the rack 312 by V-wheels 326, and instead bearings or other structure on the carriage 308 might ride on the rack 312. Alternatively, the rack 312 might be rigidly affixed to the carriage 308, and the bearing structure carrying the rack 312 might instead be provided on the mounting arms 314 or otherwise be mounted in fixed position with respect to the viewing tube 200.
In summary, the invention is not intended to be limited to the preferred versions of the invention described above, but rather is intended to be limited only by the claims set out below. Thus, the invention encompasses all different versions that fall literally or equivalently within the scope of these claims.
Claims
1. A vacuum chamber comprising:
- a. chamber walls surrounding a chamber interior;
- b. a port defined in the chamber walls, the port opening between the chamber interior and a chamber exterior;
- c. a rigid viewing tube: i. extending from the port into the chamber interior, and ii. being closed by a window situated within the chamber interior at a fixed distance from the port, the window being at least partially transparent, whereby the viewing tube forms a passage extending from the exterior of the vacuum chamber toward the chamber interior and terminating in the window, the passage being substantially unobstructed between the port and window whereby an imaging device may be inserted into the passage and moved axially along the passage and also laterally therein with respect to the window.
2. The vacuum chamber of claim 1 further comprising:
- a. a track fixed with respect to the port;
- b. a positioner carriage movable along the track;
- c. a positioner subcarriage movably affixed to the positioner carriage; and
- d. an imaging device on the positioner subcarriage, the imaging device being at least partially situated within the viewing tube and the chamber interior.
3. The vacuum chamber of claim 2 wherein the track is arcuate, with a center of curvature situated within the chamber interior.
4. The vacuum chamber of claim 1 further comprising:
- a. an imaging device; and
- b. an imaging device positioner movably mounting the imaging device at least partially within the viewing tube and the chamber interior,
- wherein the imaging device is movable axially into the passage of the viewing tube and also laterally therein.
5. The vacuum chamber of claim 4 wherein the imaging device positioner includes:
- a. an arcuate track fixed with respect to the port;
- b. a positioner carriage movable along the track; and
- c. a positioner subcarriage whereupon the imaging device is situated, the positioner subcarriage being movably affixed to the positioner carriage.
6. The vacuum chamber of claim 5 wherein the arcuate track has a center of curvature situated within the chamber interior.
7. The vacuum chamber of claim 5 wherein the positioner carriage includes wheels engaging opposing sides of the track.
8. The vacuum chamber of claim 7 wherein the positioner carriage further includes a pinion engaging the track.
9. The vacuum chamber of claim 5 wherein one or more springs are interposed between the positioner carriage and positioner subcarriage, and wherein the springs bias the positioner carriage and positioner subcarriage apart.
10. The vacuum chamber of claim 9 further comprising one or more threaded members extending between the positioner carriage and positioner subcarriage, wherein rotation of the threaded members repositions the positioner subcarriage with respect to the positioner carriage.
11. The vacuum chamber of claim 5 wherein:
- a. the positioner carriage moves along the track in a carriage plane;
- b. the positioner subcarriage is movable with respect to the positioner carriage: i. in a first plane oriented at least substantially perpendicular to the carriage plane; and ii. in a second plane oriented at least substantially parallel to the carriage plane.
12. The vacuum chamber of claim 5 wherein:
- a. the positioner carriage moves along the track in a carriage plane, and
- b. a first threaded member extends between the positioner subcarriage and the positioner carriage, and rotation of the first threaded member moves the positioner subcarriage relative to the positioner carriage in a direction at least substantially perpendicular to the carriage plane.
13. The vacuum chamber of claim 12 further comprising a second threaded member extending between the positioner subcarriage and the positioner carriage, wherein rotation of the second threaded member moves the positioner subcarriage relative to the positioner carriage in a direction at least substantially parallel to the carriage plane.
14. The vacuum chamber of claim 5 further comprising:
- a. one or more springs interposed between the positioner carriage and positioner subcarriage, wherein the springs bias the positioner carriage and positioner subcarriage apart; and
- b. one or more threaded members extending between the positioner carriage and positioner subcarriage, wherein rotation of the threaded members repositions the positioner subcarriage with respect to the positioner carriage.
15. The vacuum chamber of claim 1 wherein the viewing tube includes a flange removably affixed to the port with the viewing tube extending from the flange into the chamber interior, whereby the viewing tube may be removed from the port by removing the flange from the port.
16. The vacuum chamber of claim 1 wherein the viewing tube includes:
- a. an interior end situated within the chamber interior, wherein the window is situated at or immediately adjacent to the interior end; and
- b. an exterior end opposite the interior end and situated outside the chamber interior, the exterior end bearing an outwardly-extending flange removably affixed to the port, whereby the viewing tube may be removed from the port.
17. The vacuum chamber of claim 1 wherein the entirety of the viewing tube extends into the chamber interior between:
- a. a circumferential flange affixed to the port, and
- b. the window.
18. The vacuum chamber of claim 1 wherein the viewing tube decreases in diameter between the port and the window.
19. The vacuum chamber of claim 1 further comprising a microscope situated within the chamber interior and spaced from the viewing tube.
20. The vacuum chamber of claim 19 wherein the microscope is an atom probe microscope.
21. A vacuum chamber comprising:
- a. chamber walls surrounding a chamber interior;
- b. a port defined in the chamber walls, the port opening between the chamber interior and a chamber exterior;
- c. a viewing tube: i. having viewing tube walls rigidly extending from the port into the chamber interior, thereby defining an open passage extending from the exterior of the vacuum chamber toward the chamber interior, and ii. the viewing tube walls terminating in an at least partially transparent window situated within the chamber interior at a fixed distance from the port; and
- d. an atom probe microscope spaced from the viewing tube within the chamber interior.
22. The vacuum chamber of claim 21 further comprising an imaging device movably situated within the passage between the viewing tube walls.
23. A vacuum chamber comprising:
- a. chamber walls surrounding a chamber interior, the chamber walls having a port defined therein which opens between the chamber interior and a chamber exterior;
- b. a viewing tube having a length extending between a terminal flange and an opposing terminal window, the flange being mounted on the chamber walls about the port with: (1) the length of the viewing tube extending into the chamber interior, and (2) the window being fixed within the chamber interior spaced from the port, with the length of the viewing tube defining an open passage from the chamber exterior into the chamber interior to terminate at the window; and
- c. an atom probe microscope spaced from the viewing tube within the chamber interior.
24. The vacuum chamber of claim 23 further comprising an imaging device situated within the passage between the viewing tube walls.
25. The vacuum chamber of claim 24 wherein the imaging device is movable within the passage with respect to a central axis defined along the length of the passage.
Type: Application
Filed: Apr 15, 2004
Publication Date: Aug 31, 2006
Inventor: David Strait (Madison, WI)
Application Number: 10/552,397
International Classification: G02B 21/26 (20060101);