 Color video and audio recording and/or reproducing apparatus |
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| Optical information recording method |
| A first object of this invention is to provide a method of realizing a high erasability when a ... |
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| Multi-channel echo canceler and method using convolution of two training signals |
| OF THE DRAWINGS In the preferred embodiments, the present invention provides, among other things, ... |
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| Shared memory multiprocessor performing cache coherency |
| In the case of constructing a switch type SMP and further dividing the interior of the SMP into ... |
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| Apparatus and methods for modulation and demodulation of data |
| The present invention seeks to provide improved methods and apparatus for modulating and ... |
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| Method for transmitting multimedia packet data using a contention-resolution process |
| The present invention is based on a technique wherein packets received at a receiving port of a ... |
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| Insulated gate field-effect transistor read-only memory array |
| Applicant has discovered that the phenomenon of hot electron trapping may be utilized to fabricate ... |
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| Non-volatile semiconductor memory device |
| The present invention is conceived for solving the above-described problems and an object thereof ... |
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| Wide band constant duty cycle pulse train processing circuit |
| In FIG. 1, a binary signal train is shown, which has three equal values, namely binary "0", ... |
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Surface profile and material mapper using a driver to displace the sample in X-Y-Z directions
| Details |
Inventors: Davis, Christopher C.; Mazzoni, David L.; Cho, Kyman;
Assignee: University of Maryland, College Park (College Park, MD)
Primary Examiner: Turner; Samuel A.
Assistant Examiner: Kim; Robert
Attorney, Agent or Firm: Sears; Christopher N.
The invention uses a heterodyne interferometer with coherent detection that uses a vibrating sample that can be used as a non-contact and non-destructive surface profiler and mapping apparatus where detailed profiles of the local slope and/or roughness of the vibrating sample are obtained in three dimensions. The invention can operate in either a heterodyne or homodyne regime with a probe that uses either i) focused optics, ii) a single mode optical fiber with an integral GRIN lens at its far end for focusing onto the sample or iii) a single-mode optical fiber with a taper at the end. Additionally, the heterodyne interferometry technique can be used for imaging birefringent objects such as semiconductor diagnostics of GaAs, InGaAs, InGaAsP, and other II-VI of III-V binary, ternary, and quaternary materials for analysis and diagnostics by using the birefringent properties of the object, and monitoring the electrical activity of biological cellular tissue. |
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DETAILED DESCRIPTION The present invention provides a versatile and high resolution microscopy technique that uses a heterodyne interferometer as discussed in Cho et al.
article in Optics Letters, entitled "Hybrid Fiber-optic Sensor Using True Heterodyne Measurement Techniques", Vol.
16, p.
614-16, April 1991.
By using direct phase locked loop RF demodulation, a more narrow bandwidth of the measurement gives almost two orders of magnitude improvement in average depth resolution compared to that achieved by See et.
al.
by applying a small amplitude lateral vibration to the object under test, (typically a few nm at 1 KHz) that allows determination of the local slope of its surface which is a scanning coherent slope microscopy (SCSM) technique.
Light from a single-frequency laser, for example, a He-Ne, diode-pumped Nd:YAG, or semiconductor laser, is divided into two parts at a beam splitter.
One of the resulting beams serves as a local oscillator (the homodyne version of the invention) or may be frequency shifted by an acoustic-optic modulator in the heterodyne version of the invention.
The beam can be directed at the surface to be probed either i) through a free space assembly of focusing optics, or ii) down a single-mode optical fiber with an integral GRIN lens at its far end for focusing onto the object being examined, or iii) down a single-mode fiber with a taper at its far end that allows evanescent, near-field probing of the object being examined with sub-diffraction-limited resolution.
Resolutions on the order of 1 nanometer (nm) with visible or near-infrared laser sources.
To reduce loss, the tapered fiber is over coated with metal except for a small (1-10 nm) opening at the tip of the taper.
The position of the probe above the surface is servo-controlled based on signal amplitude and phase to carry out ultra-high resolution microscopy of an object.
Either the probe is scanned over the surface in a raster scan, or the object is raster scanned under the probe.
In addition, the surface being scanned is vibrated with a small amplitude (1-10 nm) in a direction either perpendicular, or lateral, to the direction of the laser light being directed at the surface
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