Patent Number: 
Section: description

The invention and the various features and advantageous details thereof are explained more fully with reference to the nonlimiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well known components and processing techniques are omitted so as not to unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, additions and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this detailed description. Within this application several publications are referenced by superscript Arabic numerals. Full citations for these, and other, publications may be found at the end of the specification immediately preceding the claims after the section heading References. The disclosures of all these publications in their entireties are hereby expressly incorporated by reference herein for the purpose of indicating the background of the invention and illustrating the state of the art. The below-referenced U.S. Patents disclose embodiments that were satisfactory for the purposes for which they are intended. The entire contents of U.S. Pat. Nos. 4,775,790 and 4,748,132 are hereby expressly incorporated by reference herein for all purposes. The context of the invention can include increased magnification and/or demagnification capabilities for electron holograms. This can include the initial demagnification of the object image as it passes through the first set of magnification electron lenses. The context of the invention can also include increasing the compatibility of a increased number of specimens. This can allow the viewing of a greater variety of electron holograms. The context of the invention can also include a different apparatus design. This apparatus can include a set of electron lenses to change an electron object image size, the set of electron lenses adapted to be located between an object and an electron biprism. Although the invention can be embodied in a dedicated electron holography microscope, the invention is not limited to this context. An electron microscope that includes the invention could be configured to operate with the invention in a passive state, for non-holographic uses, thereby providing a non-dedicated electron holography microscope Referring to FIG. 3A, an embodiment of an electron holography apparatus is shown, where an object image from a sample 305 is magnified by xe2x80x9clens set Bxe2x80x9d, 310, having two lenses after the objective lens 300 and before the hologram is created by the biprism 320. These two lenses in xe2x80x9clens set Bxe2x80x9d, 310, are the primary lenses used to change the magnification of the object. The resulting interference patterns formed by the biprism 320 are magnified by the following set of two lenses, xe2x80x9clens set Axe2x80x9d, 330, which are dedicated to imaging the interference fringes, onto the image plane 370. FIG. 3B shows another embodiment of the invention. After the image from the sample 305 is formed behind the objective lens 300, it is magnified by two lens sets, 340 and 360, with three lenses in each of the lens sets 340 and 360 to perform the required magnification. The distance between xe2x80x9clens set Bxe2x80x9d, 340, and the biprism 350 in FIG. 3B are different from the distance in FIG. 3A, as is the distance between the biprism 350 and xe2x80x9clens set Axe2x80x9d, 360. The lenses, in this case, could be of smaller aperture and higher coil density than the lens setup shown in FIG. 3A. This illustrates the fact that the number of lenses in each stage is variable. The quantity of lenses that can be implemented at this stage are not constrained to the numbers shown in these figures. Three lenses above the biprism (including the objective lens) would give an improved magnification range, however to get to a broad applicability, 4 lenses or more are necessary to provide the magnification range that standard microscopes provide (as the last three lenses provide a magnification of possibly 20,000 times, the upper lens system needs to cover a range from {fraction (1/20)} to 100 times magnification). When astigmatic or elliptic illumination is used, possible rotation of the main axis of the ellipse with respect to the biprism must be compensated. In addition, the condenser system may be adjusted such that the shape of the elliptical illumination in the plane where the interference fringes are generated (i.e., between lens set A and B) remains reasonably constant. In addition, the condenser lens system may be modified to incorporate stigmators sufficiently strong to provide a highly astigmatic illumination throughout most or all of the magnification range of the total system. The condenser lens can also be adjusted to ensure that the illumination in the plane where the interference fringes are generated remains reasonably constant. An alternative version of the invention is by moving the biprism in the condenser lens area above the specimen and by possible modification of the condenser lens system, it would be possible to provide a system that allows the use of differential phase contrast over a large range of magnification. This alternative, however, should not be in competition with the system with lens set A and B, as differential phase contrast presently has a limited applicability. The invention can also be included in a kit. The kit can include some, or all, of the components that compose the invention. The kit can be an in-the-field retrofit kit to improve existing systems that are capable of incorporating the invention. The kit can include software, firmware and/or hardware for carrying out the invention. The kit can also contain instructions for practicing the invention. Unless otherwise specified, the components, software, firmware, hardware and/or instructions of the kit can be the same as those used in the invention. The terms a or an, as used herein, are defined as one or more than one. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. The term program or phrase computer program, as used herein, is defined as a sequence of instructions designed for execution on a computer system. A program, or computer program, may include a subroutine, a function, a procedure, an object method, an object implementation, an executable application, an applet, a servlet, a source code, an object code, a shared library/dynamic load library and/or other sequence of instructions designed for execution on a computer system. Specific embodiments of the invention will now be further described by the following, nonlimiting examples which will serve to illustrate in some detail various features. The following examples are included to facilitate an understanding of ways in which the invention may be practiced. It should be appreciated that the examples which follow represent embodiments discovered to function well in the practice of the invention, and thus can be considered to constitute preferred modes for the practice of the invention. However, it should be appreciated that many changes can be made in the exemplary embodiments which are disclosed while still obtaining like or similar result without departing from the spirit and scope of the invention. Accordingly, the examples should not be construed as limiting the scope of the invention. FIG. 4 shows an embodiment of the invention. It illustrates how a magnified image and interference pattern can be formed with this invention. An electron beam 400 passes through the condenser lenses 200 which adjusts the intensity and illumination area of the beam as is required. The electron beam 400 strikes the object to be imaged 107, and the resulting object beam is focused by the objective lens 410. The objective lens is a critical lens because any aberrations that it may form will be further magnified by the lenses that follow it. For this reason, a narrow-gap objective lens, due to its smaller aberration coefficients. However, in order to minimize magnetic fields and provide space for tilting the sample with large angles a wide gap objective lens is desirable. To reduce the increase in aberrations associated with the wide gap, a spherical aberration corrector is recommended to be coupled with the objective lens. It will help to maintain lateral resolution capabilities while providing more space in the specimen area. After the beam exits the objective lens 410, it passes through the three lenses, 421, 422, and 423, in lens set B 420. As the object beam exits lens set B 420, the object image is de-magnified. Demagnification of the image at this point is important, in some cases, to compensate the (almost) fixed magnification factor given by the lens set dedicated to image the interference fringes. The object beam passes through the biprism 440, where the object and incident beams overlap to create an interference pattern. The interference pattern and the image then pass through the three lenses, 431, 432, and 433, in lens set A 430, for magnification before shining onto the image plane 370. FIG. 5 shows another embodiment of the invention. An electron beam 400 passes through the condenser lenses 200 where its intensity and field of view is adjusted, shines on the object 107, and the resulting image beam is focused by the objective lens 410. All of the specifics discussed in Example 1 regarding the condenser and objective lens still apply in this example. Before the beam converges, it enters the 3 lenses 511, 512, 513 of lens set B 510. As the objective beam exits lens set B 510, the object image is magnified. In addition to its main magnification function, lens set B 510 should be able to control and adjust for the object image rotation with respect to the final image. Object rotation is a function of the magnification change and needs to be compensated for. After exiting lens set B 510, the object beam 400 passes through the biprism 520, where the object and incident beams overlap to create an interference pattern. The interference pattern and the image then pass through the three lenses, 431, 432, 433, in lens set A 430 for magnification before shining onto the image plane 370. After the image and interference beams have passed through the last lens 433, the final image will be larger than the final image in Example 1. The number of lenses in lens sets A 430 and B 510 are variable and are not limited to the quantities shown in the figures. The desired magnification of the object can only be obtained by using the lens set between the object and the biprism, while compensating the magnification factor as given by the lens set between the biprism and a final image plane. This can lead to a required magnification factor  less than 1 for the lens set between the object and the biprism. Given that the lenses are electron lenses, the amount of current running through the lenses determine the focal point and magnification of each lens. The changing of the current when holding the focal point of the lenses constant will change the orientation of the image relative to the final image, as stated in U.S. Pat. No. 4,775,790. Not all of the lenses in a lens set have to be used to cause a change of focal point or magnification of a lens set, or to rotate an electron object image. As the magnification settings of the lenses in lens sets A 430 is predetermined by optimizing the interference fringes, only the lens set B 510 can provide for the required magnification range. A change in magnification in lens set B 510 will change the size of the object in the interference pattern, while a change to lens set A 430 will decrease or increase the field of view but only slightly change the overall magnification of the object. This allows for a greater variation of objects that will be compatible with the rather limited interference pattern of electron holograms. A practical application of the invention that has value within the technological arts is to facilitate the determination of morphologic structures for nano- and sub-nano technology. While instruments like the scanning electron microscope (SEM) provide a surface display down to the nanometer level, the technique of holography allows to understand the internal structures as well, as the technique is used in transmission. For example, this technique allows to detect voids and characterize them as such. Also, the technique is very sensitive to small changes in materials caused for example by doping of silicon. This is of great value for the semiconductor industry, as there is presently no other technique that allows to determine doping profiles from a volume area instead of a surface. The biology/medical area would greatly benefit from this invention for at least two reasons: the holographic reconstruction method eliminates the large background contributions from inelastically scattered electrons detrimental to the image quality. In general this invention provides an ideal transfer function for imaging, i.e., the xe2x80x9clarge area contrastxe2x80x9d, ideal for biological materials. In fact, this invention is appropriate in all areas where phase contrast imaging is necessary. There are virtually innumerable uses for the invention, all of which need not be detailed here. A transmitting electron holography microscope and associate methods, representing an embodiment of the invention, can be cost effective and advantageous for at least the following reasons. The invention increases the range of magnification available for electron holography. The invention also increases the compatibility of a greater number of specimens with the field of electron holography. The invention improves quality and/or reduces costs compared to previous approaches. All the disclosed embodiments of the invention disclosed herein can be made and used without undue experimentation in light of the disclosure. Although the best mode of carrying out the invention contemplated by the inventor is disclosed, practice of the invention is not limited thereto. Accordingly, it will be appreciated by those skilled in the art that the invention may be practiced otherwise than as specifically described herein. Further, the individual components need not be formed in the disclosed shapes, or combined in the disclosed configurations, but could be provided in virtually any shapes, and/or combined in virtually any configuration. Further, variation may be made in the steps or in the sequence of steps composing methods described herein. Further, although the lens set described herein can be a separate module, it will be manifest that the lens set may be integrated into the system with which it is associated. Furthermore, all the disclosed elements and features of each disclosed embodiment can be combined with, or substituted for, the disclosed elements and features of every other disclosed embodiment except where such elements or features are mutually exclusive. It will be manifest that various substitutions, modifications, additions and/or rearrangements of the features of the invention may be made without deviating from the spirit and/or scope of the underlying inventive concept. It is deemed that the spirit and/or scope of the underlying inventive concept as defined by the appended claims and their equivalents cover all such substitutions, modifications, additions and/or rearrangements. The appended claims are not to be interpreted as including means-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) xe2x80x9cmeans forxe2x80x9d and/or xe2x80x9cstep for.xe2x80x9d Subgeneric embodiments of the invention are delineated by the appended independent claims and their equivalents. Specific embodiments of the invention are differentiated by the appended dependent claims and their equivalents. 1. http://www.bnl.gov/term/images/Slide2.JPG, Brookhaven National Laboratory, Aug. 21, 2001. 2. http://www.oml.gov/ORNLReview/rev28-4/text/electron.htm, Oak Ridge National Laboratory Review, Volume 28, Number 4, 1995. 3. Introduction to Electron Holography, Eds. E. Voelkl et al., Kluwer Academic/Plenum Publishers, 1999. 4. The Electrical Engineering Handbook, CRC Press, (Richard C. Dorf et al. eds.), 1993. 5. U.S. Pat. No. 4,775,790, Transmission Electron Microscope, 1988. 6. U.S. Pat. No. 4,748,132, Micro Fabrication Process for Semiconductor Structure Using Coherent Electron Beams, 1988.