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Focal Spot Size

About: Focal Spot Size is a research topic. Over the lifetime, 618 publications have been published within this topic receiving 10107 citations.


Papers
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Journal ArticleDOI
TL;DR: The diffraction barrier responsible for a finite focal spot size and limited resolution in far-field fluorescence microscopy has been fundamentally broken by quenching excited organic molecules at the rim of the focal spot through stimulated emission.
Abstract: The diffraction barrier responsible for a finite focal spot size and limited resolution in far-field fluorescence microscopy has been fundamentally broken. This is accomplished by quenching excited organic molecules at the rim of the focal spot through stimulated emission. Along the optic axis, the spot size was reduced by up to 6 times beyond the diffraction barrier. The simultaneous 2-fold improvement in the radial direction rendered a nearly spherical fluorescence spot with a diameter of 90–110 nm. The spot volume of down to 0.67 attoliters is 18 times smaller than that of confocal microscopy, thus making our results also relevant to three-dimensional photochemistry and single molecule spectroscopy. Images of live cells reveal greater details.

1,662 citations

Patent
06 May 2005
TL;DR: In this paper, the effect of the finite focal spot size of the X-ray source is mitigated by inverse filtering the aggregated detector image from the detector assembly, improving the quality of the resulting image.
Abstract: A radiographic imaging device includes an X-ray source having a finite focal spot characterized by a determined intensity distribution. The X-ray source emits a beam of X-ray radiation toward an object. A detector assembly receives at least part of the X-ray radiation after it passes through the object. The detector assembly produces a signal in response to the received radiation. An image processor constructs an image from the signal generated by the detector assembly using the determined intensity distribution of the X-ray source. By inverse filtering the aggregated detector image from the detector assembly, the effects of the finite focal spot size of the X-ray source are mitigated, improving the quality of the resulting image.

593 citations

Journal ArticleDOI
TL;DR: In this paper, a record peak intensity of 0.7×1022 W/cm2 was achieved by focusing a 45-TW laser beam with an f/0.6 off-axis paraboloid.
Abstract: We generated a record peak intensity of 0.7×1022 W/cm2 by focusing a 45-TW laser beam with an f/0.6 off-axis paraboloid. The aberrations of the paraboloid and the low-energy reference laser beam were measured and corrected, and a focal spot size of 0.8 µm was achieved. It is shown that the peak intensity can be increased to 1.0×1022 W/cm2 by correction of the wave front of a 45-TW beam relative to the reference beam. The phase and amplitude measurement provides for an efficient full characterization of the focal field.

350 citations

Journal ArticleDOI
TL;DR: A prototype system is constructed to assess MRI thermal monitoring and the localization of the heat zone in muscle and acquisitions are optimized for high temperature sensitive images that yield the thermal diffusivity, heat flow time constant and the focal spot size in muscle.
Abstract: Deep lying soft tissue tumors may be treated by a nonincisional surgical procedure executed inside an MR imaging system using a thermal effect delivered by a focused ultrasound transducer. A prototype system is constructed to assess MRI thermal monitoring and the localization of the heat zone in muscle. The temperature distribution of the focal spot is imaged with MRI while mechanically moving the transducer with an hydraulic 3-axis positioner. Acoustic power is applied with a spherical shell transducer using 1- to 10-s duration pulses at frequencies of 1.5 MHz to selectively coagulate tissue at 60-70 degrees C. The procedure is monitored with a series of fast second gradient echo, T1-weighted, temperature sensitive MR sequences. Acquisitions are optimized for high temperature sensitive images that yield the thermal diffusivity, heat flow time constant and the focal spot size in muscle. MR temperature maps of muscle provide localization and dosimetry both in the focal region and near field.

282 citations

Journal ArticleDOI
TL;DR: The intensity distributions near the focal point for radially polarized laser beams including higher-order transverse modes are calculated based on vector diffraction theory and can effectively reduce the focal spot size because of destructive interference between the inner and the outer rings with pi phase shift.
Abstract: The intensity distributions near the focal point for radially polarized laser beams including higher-order transverse modes are calculated based on vector diffraction theory. For higher-order radially polarized mode beams as well as a fundamental mode (R-TEM01*) beam, the strong longitudinal component forms a sharper spot at the focal point under a high-NA focusing condition. In particular, double-ring-shaped radially polarized mode (R-TEM11*) beams can effectively reduce the focal spot size because of destructive interference between the inner and the outer rings with π phase shift. Compared with an R-TEM01* beam focusing in a limit of NA=1, the full width at half-maximum values of the focal spot for an R-TEM11* beam are decreased by 13.6% for the longitudinal component and 25.8% for the total intensity.

215 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202119
202026
201925
201819
201721
201637