scholarly journals Concept of an In-Plane Displacement Sensor Based on Grating Interferometry with a Stepwise Change of Sensitivity

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4894
Author(s):  
Leszek Sałbut ◽  
Sergiusz Łuczak
Keyword(s):  
Spatial Frequency ◽  
Relevant Literature ◽  
High Spatial Frequency ◽  
High Sensitivity ◽  
Measurement Range ◽  
Displacement Sensor ◽  
Special Method ◽  
Stepwise Change ◽  
Low Sensitivity ◽  
Plane Displacement

Grating Interferometry, known in the relevant literature as the High Sensitivity Moiré Interferometry, is a method for in-plane displacement and strain measurement. The sensitivity of this method depends on the spatial frequency of the diffraction grating attached to the object under test. For typical specimen grating, with high spatial frequency of 1200 lines per mm, the basic sensitivity is 0.417 µm per fringe. A concept of in-plane displacement sensor based on Grating Interferometry with a stepwise change in sensitivity is presented. It is realized by using the specimen grating with lower spatial frequency. In this case, the grating has more higher diffraction orders and by selecting them appropriately, the sensitivity (chosen from 1.25 μm, 0.625 μm, or 0.417 μm) and the resulting measurement range (chosen from about 600 μm, 300 μm, or 200 μm) can be adjusted to the requirements of a given experiment. A special method of filtration is required in this case. Achromatic configuration with illumination grating was chosen due to its low sensitivity to vibration.

scholarly journals Second harmonic generation correlation spectroscopy for characterizing translationally diffusing protein nanocrystals

2016 ◽  
Vol 72 (7) ◽  
pp. 849-859
Author(s):  
Ximeng Y. Dow ◽  
Christopher M. Dettmar ◽  
Emma L. DeWalt ◽  
Justin A. Newman ◽  
Alexander R. Dow ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Unit Volume ◽  
Second Harmonic ◽  
Incident Beam ◽  
High Sensitivity ◽  
Correlation Spectroscopy ◽  
Optical Process ◽  
Active Nanoparticles ◽  
Low Sensitivity

Second harmonic generation correlation spectroscopy (SHG-CS) is demonstrated as a new approach to protein nanocrystal characterization. A novel line-scanning approach was performed to enable autocorrelation analysis without sample damage from the intense incident beam. An analytical model for autocorrelation was developed, which includes a correction for the optical scattering forces arising when focusing intense, infrared beams. SHG-CS was applied to the analysis of BaTiO3nanoparticles ranging from 200 to ∼500 nm and of photosystem I nanocrystals. A size distribution was recovered for each sample and compared with the size histogram measured by scanning electron microscopy (SEM). Good agreement was observed between the two independent measurements. The intrinsic selectivity of the second-order nonlinear optical process provides SHG-CS with the ability to distinguish well ordered nanocrystals from conglomerates and amorphous aggregates. Combining the recovered distribution of particle diameters with the histogram of measured SHG intensities provides the inherent hyperpolarizability per unit volume of the SHG-active nanoparticles. Simulations suggest that the SHG activity per unit volume is likely to exhibit relatively low sensitivity to the subtle distortions within the lattice that contribute to resolution loss in X-ray diffraction, but high sensitivity to the presence of multi-domain crystals.

VEP and PERG acuity in anesthetized young adult rhesus monkeys

1999 ◽  
Vol 16 (4) ◽  
pp. 607-617 ◽  
Author(s):  
JAMES N. VER HOEVE ◽  
YURI P. DANILOV ◽  
CHARLENE B.Y. KIM ◽  
PETER D. SPEAR
Keyword(s):  
Young Adult ◽  
Spatial Frequency ◽  
Rhesus Monkeys ◽  
Dose Range ◽  
High Spatial Frequency ◽  
Sine Wave ◽  
Frequency Method ◽  
Behavioral Studies ◽  
S Period ◽  
Highly Correlated

This study used the swept spatial-frequency method to compare retinal and cortical acuity in anesthetized young adult rhesus monkeys. Visual evoked potentials (VEPs) and pattern electroretinographic responses (PERGs) were recorded from 25 monkeys (age range: 4–12 years) anesthetized with a continuous infusion of propofol. The stimuli were temporally countermodulated sine-wave gratings that increased in spatial frequency within a 10.24-s period. All animals were refracted using acuity estimated from the zero micro-volt intercept of the linear regression of evoked potential amplitude on spatial frequency. Average sweep acuities were 23.7 cycles/deg ± 1.5 S.E.M. and 23.1 cycles/deg ± 1.8 S.E.M. for the PERG and VEP, respectively. VEP and PERG acuities were within the range expected based on acuities estimated from behavioral studies in macaques. PERG and VEP acuities were highly correlated (r = 0.90) and equally sensitive to spherical blur. On a subset of animals, test–retest reliability of animals, and interocular correlations, were high (r = 0.87 and r = 0.83, respectively). Increasing propofol dosage 8-fold did not degrade PERG or VEP acuity. This study demonstrates that high spatial-frequency acuities can be rapidly obtained from young adult rhesus monkeys under a wide dose range of propofol anesthesia using the swept spatial-frequency method.

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