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AssigneeGeneral Phosphorix LLC
InventorsArkady Nikitin, Dmitriy Yeremin
Estimating the term…
A method of precision calibration of magnification of scanning microscopes with the use of a test diffraction grating includes positioning a test object on a stage of microscope so that strips of a test diffraction grating are perpendicular to a direction along which a calibration is performed, scanning of a selected portion of the test object along axes X and Y, measuring values of a signal S versus coordinates x and y in a plane of scanning and storing of the values S (x, y) in a digital form as a two-dimensional digital array, transforming the two-dimensional array of signals S(x, y) into a two-dimensional array S (u, v) by turning of the axes so that a direction of a new axis u is perpendicular to the strips of the grating and a direction of a new axis v coincides with the strips of the grating, line-by-line mathematical processing of the array S(u,v) for each line, converting of the one dimensional, complex function into a one-dimension spectrum of real values of a module, finding from the spectrum of the real values a greatest spectral maximum and determining its characteristic frequency as an abscissa of a point with the maximum value, calculating an average value of a pitch of the diffraction grating; performing the mathematical processing, the conversion, the determination and the calculation for subsequent lines with a new value of a coordinate v, statistically processing the thusly obtained values for all lines and determining an average value and a standard deviation over a whole frame, and determining a magnification Mu in accordance with the selected direction u.
A method of precision calibration of magnification of a scanning microscope with the use of a test object formed as a test diffraction grating, comprising the steps of positioning and orienting a test object on stage of microscope so that strips of a test diffraction grating are perpendicular to a direction along which a calibration is performed;
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Specially adapted for specific applications: scanning microscopes
Optical elements, systems or apparatus
Term ended 4 May 2021 (estimated)
The present invention relates to the methods of precision calibration of magnification of scanning microscopes with the use of a test diffraction grate.
Methods of precision calibration of a magnification of synthetic microscopes with the use of a test diffraction gratings are known. In the existing methods test object is positioned and oriented on a microscope table, and corresponding part of the test objects is scanned, with subsequent processing of the thusly obtained data. It is believed that the existing methods can be further improved.
Accordingly, it is an object of the present invention to provide a method of precision calibration of magnification of a scanning microscopes with the use of a test diffraction grating.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
FIG. 1 is a view showing an image of a test object with directions of scanning and a direction in which a multiplication of a microscope is to be determined;
FIG. 2 is a view additionally illustrating a second coordinate system, in which an obtained array of signals is to be converted;
In accordance with the present invention a method for precision calibration of a magnification of a scanning microscope is performed with a test diffraction grating. FIG. 1 shows a field of view 1 of a scanning microscope with a plurality of pixels 2 of a signal of scanning with an image of a diffraction grating which has strips 3. The directions of scanning are identified with X and Y and the scanning is performed in accordance with these two perpendicular axes. A magnification of calibration the scanning electron microscope is performed in direction lower u. As can be seen from this drawing, the test object is positioned and oriented on the microscope so that the strips of the test diffraction grate are perpendicular to the direction u of calibration.
A portion of the test object which is shown in FIG. 1 is then scanned, and a plurality of values of the signal S versus the coordinates in a plane of scanning are obtained. These values are identified as S(x, y) and they are stored in a digital form as a two-dimensional digital array, for example in a memory of a computer. The thusly obtained two dimensional array of signals S(x, y) is transformed into a two dimensional array S(u, v) by turning of the axes, so that a direction of a new axis u is perpendicular to the strips of the grating, and a direction of a new axis v corresponds to the direction of the strips of the grating, as shown in FIG. 2. Thereby a new array of the signal is obtained.
Then line-by-line mathematical processing of the array S(u,v) is performed for each line S(u) by calculating of a Fourier spectrum of the line SP(ω) in correspondence with the formula SP ( • ) = 1 2 - ∫ - ∞ ∞ S ( u ) · exp ( ⅈu ω ) ⅆ u ,