Spatial Resolution and Data Addressing of Frequency Domain Optical Storage Materials in the Near IR Regime

1992 ◽  
Vol 31 (Part 1, No. 2B) ◽  
pp. 693-698 ◽  
Author(s):  
R. Ao ◽  
S. Jahn ◽  
L. Kümmerl ◽  
R. Weiner ◽  
D. Haarer
Keyword(s):  
Frequency Domain ◽  
Spatial Resolution ◽  
Optical Storage ◽  
Storage Materials ◽  
Near Ir

Time-frequency domain optical storage in rare-earth-doped materials

1994 ◽  
Vol 6 (10) ◽  
pp. 791-793
Author(s):  
Ravinder Kachru ◽  
Yu Sheng Bai ◽  
Xiao-An Shen
Keyword(s):  
Rare Earth ◽  
Frequency Domain ◽  
Optical Storage ◽  
Time Frequency ◽  
Doped Materials ◽  
Rare Earth Doped

Spatial Resolution and Frequency Characteristics for Dose Modulation on the TrueBeam Medical Accelerator

2021 ◽  
Vol 91 (3) ◽  
pp. 17-26
Author(s):  
V. N. Vasiliev ◽  
A. Yu. Smyslov
Keyword(s):  
Power Spectrum ◽  
Frequency Domain ◽  
Spatial Resolution ◽  
Dose Response ◽  
Peak Width ◽  
Multi Leaf Collimator ◽  
Useful Signal ◽  
Significant Difference ◽  
Dose Modulation ◽  
Statistical Noise

Purpose: To study the spatial resolution achievable by dose modulation in a water phantom using a multi-leaf collimator, jaws and their combination. To estimate the power spectrum density of the useful signal (dose distribution) and statistical noise, evaluate the frequency interval containing the useful signal. Material and methods: Using the Gafchromic EBT2 radiochromic film, nested squares dose patterns formed in a water-equivalent phantom by 6 and 15 MV photon beams of the TrueBeam medical accelerator, jaws, a multi-leaf collimator, and a combination of these devices were measured. Dose response to step function (ESF) data was extracted from the penumbra and the linear photon source dose response function (LSF) was calculated. To move to frequency domain, fast Fourier transform was performed over the obtained datasets, as well as over individual LSF peaks, and then power spectra densities were calculated. The Nyquist frequency associated with data sampling was 1.42 mm-1, the Hann window was used to minimize leakage effect. Results: The shape of the obtained LSF peaks was approximated by a sum of two Gaussian distributions with the same center positions but different widths. The LSF peak width at half maximum (FWHM) was 1.7-3.9 mm depending on the modulation device. No significant difference was observed in the peak widths at energies of 6 and 15 MV. In most cases, the width of the peak along the X-axis was wider than along the Y-axis. The power spectrum of the useful signal had a maximum near zero frequency, a 50 % level was near 0.09 mm-1 and its high frequency limit was about 0.4 mm-1. Above this value, only the spectrum of statistical noise was recorded, uniformly distributed over frequency. Conclusion: The obtained values of the LSF peak width in the range 1.7-3.9 mm characterize the ability of dose modulation by the considered devices or their combination, which can be significant for treatment of small targets (less than 3-4 cm), where these limits of spatial resolution can be reached. The obtained relationships in frequency domain can be used for optimal removal of statistical noise using Wiener filters from profiles or two-dimensional dose distributions.

scholarly journals Enhancement of the Performance and Data Processing Rate of an Optical Frequency Domain Reflectometer Distributed Sensing System Using A Limited Swept Wavelength Range

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3480 ◽  
Author(s):  
Kunpeng Feng ◽  
Jiwen Cui ◽  
Yihua Jin ◽  
Xun Sun ◽  
Dong Jiang ◽  
...  
Keyword(s):  
Data Processing ◽  
Frequency Domain ◽  
Spatial Resolution ◽  
Wavelength Range ◽  
Distributed Sensing ◽  
Optical Frequency ◽  
Local Similarity ◽  
Processing Rate ◽  
Spectrum Range ◽  
Measurable Range

A novel optical frequency domain reflectometer (OFDR) processing algorithm is proposed to enhance the measurable range and data processing rate using a narrow swept spectrum range and reducing the time consuming of the process distributed sensing results. To reduce the swept wavelength range and simultaneously enhance strain measurable range, the local similarity characteristics of Rayleigh scattering fingerprint spectrum is discovered and a new similarity evaluation function based on least-square method is built to improve the data processing rate and sensing performance. By this method, the strain measurable range is raised to 3000 µε under a highest spatial resolution of 3 mm when the swept spectrum range is only 10 nm and the data processing rate is improved by at least 10 times. Experimental results indicate that a nonlinearity of less than 0.5%, a strain resolution of better than 10 µε, a repeatability at zero strain of below ±0.4 GHz and a full-scale accuracy is lower than 0.85 GHz under a highest spatial resolution of 3 mm can be achieved. Advantages of this method are fast processing rate, large strain measurable range, high SNR, and applicability with current OFDR systems.

A precision tester for studies of holographic optical storage materials and recording physics

1996 ◽  
Vol 35 (14) ◽  
pp. 2360 ◽  
Author(s):  
M.-P. Bernal ◽  
H. Coufal ◽  
R. K. Grygier ◽  
J. A. Hoffnagle ◽  
C. M. Jefferson ◽  
...  
Keyword(s):  
Optical Storage ◽  
Storage Materials
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