1. Peter J. De Groot

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    1. Mentioned In 26 Articles

    2. Interferometry employing refractive index dispersion broadening of interference signals

      Interferometry employing refractive index dispersion broadening of interference signals
      An interferometry system includes: a light source, defining a coherence length, an interferometer configured to combine measurement and reference beams to form an output beam, where the interferometer includes a dispersion imbalance between measurement and reference paths large enough to produce a coherence envelope for the system having a width more than twice the coherence length; a phase modulation device configured to introduce a variable phase between the measurement and ...
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    3. Low coherence interferometry with scan error correction

      Low coherence interferometry with scan error correction
      A system includes an interference microscope having one or more optical elements arranged to image a test object to an image plane by combining test light from the test object with reference light from a reference object to form an interference pattern at the image plane, wherein the test and reference light are derived from a common broadband light source. The system includes a scanning stage configured to scan an ...
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    4. Analyzing surface structure using scanning interferometry

      Analyzing surface structure using scanning interferometry
      A method includes comparing a scanning interferometry signal obtained for a location of a test object to each of multiple model signals corresponding to different model parameters for modeling the test object, wherein for each model signal the comparing includes calculating a correlation function between the scanning interferometry signal and the model signal to identify a surface-height offset between the scanning interferometry signal and the model signal and, based on ...
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    5. Interferometric analysis of under-resolved features

      Interferometric analysis of under-resolved features
      In certain aspects, disclosed methods include directing test light reflected from an object to form an image of the object on a detector, where the object includes a diffractive structure. The test light at the detector includes both specularly and non-specularly reflected light from the diffractive structure, and the diffractive structure is under-resolved in the image. The method further includes directing reference light to interfere with the test light at ...
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    6. Interferometer utilizing polarization scanning

      Interferometer utilizing polarization scanning
      In one aspect, the disclosure features methods that include using a microscope to direct light to a test object and to direct the light reflected from the test object to a detector, where the light includes components having orthogonal polarization states, varying an optical path length difference (OPD) between the components of the light, acquiring an interference signal from the detector while varying the OPD between the components, and determining ...
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    7. Interferometry for lateral metrology

      Interferometry for lateral metrology
      A method is disclosed which includes: using a scanning interferometry system, generating a sequence of phase-shifted interferometry images at different scan positions of an object comprising a buried surface, identifying a scan position corresponding to a position of best focus for the buried surface based on the sequence of phase-shifted interferometry images of the object, and generating a final image based on the phase-shifted interferometry images and the scan position ...
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    8. Multiple-angle multiple-wavelength interferometer using high-NA imaging and spectral analysis

      Multiple-angle multiple-wavelength interferometer using high-NA imaging and spectral analysis
      A method is disclosed including: generating a scanning interferometry signal at each of multiple wavelengths for each of at least one location on a test object; obtaining the scanning interferometry signals at each of the multiple wavelengths for each of at least one location on the test object; analyzing the scanning interferometry signals to determine information about the test object; and outputting the information about the test object. Each scanning ...
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    9. Interferometer system for monitoring an object

      Interferometer system for monitoring an object
      System for monitoring a position of one or more optical elements in a projection objective (PO) include a plurality of sensors each configured to receive input light and to form output light, each sensor including a first sensor optic and a second sensor optic, the first sensor optic of at least one of the sensors being affixed to a first PO optical element and the second sensor optic of the ...
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    10. Interferometry method and system including spectral decomposition

      In general, in one aspect, the disclosure features a method that includes directing measurement light to reflect from a measurement surface and combining the reflected measurement light with reference light, where the measurement light and reference light are derived from a common source, and there is a non-zero optical path length difference between the measurement light and reference light that is greater than a coherence length of the measurement light ...
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    11. Interferometer with multiple modes of operation for determining characteristics of an object surface

      Disclosed is a system including: (i) an interferometer configured to direct test electromagnetic radiation to a test surface and reference electromagnetic radiation to a reference surface and subsequently combine the electromagnetic radiation to form an interference pattern, the electromagnetic radiation being derived from a common source; (ii) a multi-element detector; and (iii) one or more optics configured to image the interference pattern onto the detector so that different elements of ...
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    12. Phase shifting interferometry with multiple accumulation

      An interferometer system is disclosed which is configured to combine measurement light with reference light to form an optical interference pattern, where the interferometer system includes a modulator configured to repetitively introduce a sequence of phase shifts between the measurement and reference light; and a camera system positioned to measure the optical interference pattern, where the camera system is configured to separately accumulate time-integrated images of the optical interference pattern ...
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    13. Compensation of systematic effects in low coherence interferometry

      In general, in one aspect, the invention features a method that includes transforming interferometry data acquired for a test sample using a low coherence imaging interferometry system to a frequency domain and, at a plurality of frequencies in the frequency domain, reducing contributions to the transformed interferometry data due to imperfections in the imaging interferometry system thereby producing compensated interferometry data. The errors are reduced based on variations between interferometry ...
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    14. Interferometer for determining characteristics of an object surface

      BACKGROUND The invention relates to interferometry.Interferometric techniques are commonly used to measure the profile of a surface of an object. To do so, an interferometer combines a measurement wavefront reflected from the surface of interest with a reference wavefront reflected from areference surface to produce an interferogram. Fringes in the interferogram are indicative of spatial variations between the surface of interest and the reference surface. A scanning interferometer scans ...
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    15. Interferometer for determining characteristics of an object surface, including processing and calibration

      BACKGROUND The invention relates to interferometry.Interferometric techniques are commonly used to measure the profile of a surface of an object. To do so, an interferometer combines a measurement wavefront reflected from the surface of interest with a reference wavefront reflected from areference surface to produce an interferogram. Fringes in the interferogram are indicative of spatial variations between the surface of interest and the reference surface.A scanning interferometer scans ...
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  2. About Peter J. De Groot

    Peter J. De Groot

    Peter J. de Groot is Director of R&D; at Zygo Corporation in Middlefield, Connecticut, USA.