Electron microscope with multi-focusing electron lens

Claim 2

In an electron microscope the combination comprising: an objective lens comprising two pole pieces spaced along a lens axis with a gap between the pole pieces sufficiently wide to permit manipulation of the specimen in the gap; means for exciting the objective lens in such a manner that at least two successive focii are simultaneously produced within the lens gap, the first of said focii being of high and the other focus being of lower resolution, said other focus being nearer the center of the lens gap than said first focus; and, means for selectively positioning a specimen selectively and one at a time at either said first focus and said other focus; whereby positioning of the specimen at the first focus will provide a high resolution while positioning the specimen at the other focus will provide a lower resolution but with ample space to enable the specimen to be fully manipulated.

Claim 3

The electron microscope of claim 1 wherein said means for exciting the objective lens includes at least one magnetizing coil associated with the pole pieces and positioned with respect to the pole pieces to excite the pole pieces.

Claim 4

The electron microscope of claim 1 wherein said means for selectively positioning a specimen comprises a specimen holder which may be positioned at the first focus position for operation with high resolution and may be positioned at other focii positions nearer the center of the lens gap for operation at reduced resolution but with sufficient room for full specimen manipulation.

Claim 5

An electron microscope having an electron beam generating means for developing an electron beam; an objective lens comprising two pole pieces spaced along a lens axis so as to define an axial lens gap; at least one magnetizing coil associated with said pOle pieces and positioned with respect to said pole pieces to excite said associated pole pieces; an outer housing surrounding and supporting said pole pieces and said magnetizing coils, said outer housing having an access opening therein for inserting an object to be imaged between said pole pieces, said magnetizing coils being adapted for connection to a source of energization whereby at least a portion of said electron beam may be deflected in a manner so that said portion of said beam intersects said lens axis at a plurality of points within the lens gap and thereby simultaneously defines at least two successive focii within the lens gap, the first of said focii being of high resolution and the other focus being of lower resolution, said other focus being nearer the center of the lens gap than said first focus; and adjustable support means extending through said access opening in said housing for positioning a said object selectively and one at a time of either of said focii, whereby positioning of the object at the first focus will provide a high resolution while positioning the object at the other focus will provide a lower resolution but with ample space to enable the specimen to be fully manipulated.

Claim 6

An electron microscope having an electron beam generating means for developing an electron beam; an objective lens comprising two pole pieces spaced along a lens axis so as to define an axial lens gap; at least one magnetizing coil associated with said pOle pieces and positioned with respect to said pole pieces to excite said associated pole pieces; an outer housing surrounding and supporting said pole pieces and said magnetizing coils, said outer housing having an access opening therein for inserting an object to be imaged between said pole pieces, said magnetizing coils being adapted for connection to a source of energization whereby at least a portion of said electron beam may be deflected in a manner so that said portion of said beam intersects said lens axis at a plurality of points within the lens gap and thereby simultaneously defines at least two successive focii within the lens gap, the first of said focii being of high resolution and the other focus being of lower resolution, said other focus being nearer the center of the lens gap than said first focus; and adjustable support means extending through said access opening in said housing for positioning a said object selectively and one at a time of either of said focii, whereby positioning of the object at the first focus will provide a high resolution while positioning the object at the other focus will provide a lower resolution but with ample space to enable the specimen to be fully manipulated.

Claim 7

An electron microscope having an electron beam generating means for developing an electron beam, an electron lens having two pole pieces spaced along a lens axis so as to define an axial lens gap, means for exciting said pole pieces to deflect said electron beam in a manner so that said electron beam intersects said lens axis at a plurality of points within the lens gap thereby simultaneously defining focii within the lens gap, the first of said focii being of high resolution for another focus being of lower resolution, said another focus being nearer the center of the lens gap than said first focus and adjustable support means for positioning a specimen selectively and one at a time at either of said focal points, whereby positioning of the specimen at the first focus will provide a high resolution while positioning the specimen at the other focus will provide a lower resolution but with ample space to enable the specimen to be fully manipulated.

Claim 8

An electron microscope having an electron beam generating means for developing an electron beam, an electron lens having two pole pieces spaced along a lens axis so as to define an axial lens gap, means for exciting said pole pieces to deflect said electron beam in a manner so that said electron beam intersects said lens axis at a plurality of points within the lens gap thereby simultaneously defining focii within the lens gap, the first of said focii being of high resolution for another focus being of lower resolution, said another focus being nearer the center of the lens gap than said first focus and adjustable support means for positioning a specimen selectively and one at a time at either of said focal points, whereby positioning of the specimen at the first focus will provide a high resolution while positioning the specimen at the other focus will provide a lower resolution but with ample space to enable the specimen to be fully manipulated.

Claim 9

An electron microscope comprising: a. structure defining an evacuatable microscope column having an elongated electron beam path; b. an electron source positioned at one end of said path for emitting a stream of electrons; c. an image-producing mechanism at the other end of said path for producing an image in response to electrons striking said mechanism; d. electron optical lens means along said path for controlling the flow of electrons in a beam, said lens means defining a lens gap along said path; e. said lens means being constructed to cause the flow of electrons along said path to simultaneously produce at least three successive focii within the lens gap where electrons cross over the axis of said path, the first of said focii being at higher resolution than the other focii, at least one of said other focii being nearer the center of the lens gap than said first focus; and f. a specimen stage connectable to said structure and adapted to position a specimen selectively and one at a time at a central one of said other focii in said gap for the conduction of studies at low resolution where substantial room for the specimen or its manipulation is required or at a focus nearer said electron source for higher resolution studies.

Claim 10

An electron microscope comprising: a. structure defining an evacuatable microscope column having an elongated electron beam path; b. an electron source positioned at one end of said path for emitting a stream of electrons; c. an image-producing mechanism at the other end of said path for producing an image in response to electrons striking said mechanism; d. electron optical lens means along said path for controlling the flow of electrons in a beam, said lens means defining a lens gap along said path; e. said lens means being constructed to cause the flow of electrons along said path to simultaneously produce at least three successive focii within the lens gap where electrons cross over the axis of said path, the first of said focii being at higher resolution than the other focii, at least one of said other focii being nearer the center of the lens gap than said first focus; and f. a specimen stage connectable to said structure and adapted to position a specimen selectively and one at a time at a central one of said other focii in said gap for the conduction of studies at low resolution where substantial room for the specimen or its manipulation is required or at a focus nearer said electron source for higher resolution studies.

Claim 13

A method of focusing an electron beam as defined in claim 7 including the additional step of positioning a said object to be imaged at another one of said plurality of focal points along said lens axis.

Claim 14

A method of focusing an electron beam as defined in claim 7 including the step of exciting said pole pieces with said coil means to deflect at least a portion of said electron beam in a manner so that said beam intersects said lens axis at at least three different points along said axis.

Claim 15

A method of focusing an electron beam as defined in claim 7 wherein said electron beam generating means is positioned substantially along said lens axis, and including the step of positioning said object to be imaged at a one of said plurality of focal points along said lens axis which is most distant from said electron beam generating means.