Full-field deflectometry for detection of mid-spatial frequency errors of high-precision mirrors (Conference Presentation)

Optifab 2019 ◽  
2019 ◽  
Author(s):  
Philippe Antoine ◽  
Luc Boussemaere ◽  
Arno Bouwens ◽  
Vincent Moreau ◽  
Benoit Borguet ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
High Precision ◽  
Full Field

Spatial Frequency and Selective Attention to Spatial Location

Perception ◽  
1987 ◽  
Vol 16 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Gordon L Shulman ◽  
James Wilson
Keyword(s):  
Visual Field ◽  
Selective Attention ◽  
Spatial Frequency ◽  
Spatial Attention ◽  
Spatial Location ◽  
Peripheral Visual Field ◽  
Low Frequencies ◽  
Full Field ◽  
High Frequencies ◽  
Probe Technique

The effect of spatial attention on the detectability of gratings of different spatial frequency was measured using a probe technique. Three experiments are reported in which the detectability of full-field probe gratings was measured while subjects analyzed stimuli presented in either the central or the peripheral visual field. Selective attention to peripheral stimuli produced a facilitation at low frequencies and a decrement at high frequencies. These effects disappeared under forced-choice presentation.

Full-field deflectometry for optical characterization of high-precision mirrors

2019 ◽  
Author(s):  
Philippe Antoine ◽  
Luc Boussemaere ◽  
Arno Bouwens ◽  
Vincent Moreau ◽  
Benoït Borguet ◽  
...  
Keyword(s):  
High Precision ◽  
Optical Characterization ◽  
Full Field

scholarly journals Temporal and spatial tuning of dorsal lateral geniculate nucleus neurons in unanesthetized rats

2016 ◽  
Vol 115 (5) ◽  
pp. 2658-2671 ◽  
Author(s):  
Balaji Sriram ◽  
Philip M. Meier ◽  
Pamela Reinagel
Keyword(s):  
Spatial Frequency ◽  
High Frequency ◽  
Visual Stimulation ◽  
Temporal Frequency ◽  
Single Units ◽  
Dorsal Lateral Geniculate Nucleus ◽  
Visual Response ◽  
Visual Responses ◽  
Temporal Modulation ◽  
Full Field

Visual response properties of neurons in the dorsolateral geniculate nucleus (dLGN) have been well described in several species, but not in rats. Analysis of responses from the unanesthetized rat dLGN will be needed to develop quantitative models that account for visual behavior of rats. We recorded visual responses from 130 single units in the dLGN of 7 unanesthetized rats. We report the response amplitudes, temporal frequency, and spatial frequency sensitivities in this population of cells. In response to 2-Hz visual stimulation, dLGN cells fired 15.9 ± 11.4 spikes/s (mean ± SD) modulated by 10.7 ± 8.4 spikes/s about the mean. The optimal temporal frequency for full-field stimulation ranged from 5.8 to 19.6 Hz across cells. The temporal high-frequency cutoff ranged from 11.7 to 33.6 Hz. Some cells responded best to low temporal frequency stimulation (low pass), and others were strictly bandpass; most cells fell between these extremes. At 2- to 4-Hz temporal modulation, the spatial frequency of drifting grating that drove cells best ranged from 0.008 to 0.18 cycles per degree (cpd) across cells. The high-frequency cutoff ranged from 0.01 to 1.07 cpd across cells. The majority of cells were driven best by the lowest spatial frequency tested, but many were partially or strictly bandpass. We conclude that single units in the rat dLGN can respond vigorously to temporal modulation up to at least 30 Hz and spatial detail up to 1 cpd. Tuning properties were heterogeneous, but each fell along a continuum; we found no obvious clustering into discrete cell types along these dimensions.

High-Precision Transmission-Wavefront-Processing Technology of Large Aperture Ti∶sapphire Crystal at Full Spatial Frequency

2019 ◽  
Vol 46 (9) ◽  
pp. 0903002
Author(s):  
金寿平 shouping Jin ◽  
付跃刚 Yuegang Fu ◽  
金钰皓 Yuhao Jin ◽  
郝志旭 Zhixu Hao
Keyword(s):  
Spatial Frequency ◽  
High Precision ◽  
Processing Technology ◽  
Sapphire Crystal ◽  
Large Aperture

High dose sildenafil citrate induced persistent binocular anomalopia: A case report

2019 ◽  
Author(s):  
Ying Huang ◽  
Changbiao Xu ◽  
Qianqian Zhu ◽  
Yikui Zhang ◽  
Bing Lin
Keyword(s):  
Side Effects ◽  
Spatial Frequency ◽  
Outer Layer ◽  
Sildenafil Citrate ◽  
Recommended Dose ◽  
High Dose ◽  
Full Field ◽  
Visual Symptoms ◽  
Ocular Side ◽  
Interdigitation Zone

Abstract Background: When taking the recommended dose of sildenafil citrate for male erectile dysfunction (ED) and pulmonary hypertension (PAH), the incidence of ocular side effects, including a sense of blue-tinted vision and changes in brightness perception in the form of increased sensitivity to light, was 0.1–11%, and the visual symptoms were almost transient. Only a few cases reported the large dose of sildenafil citrate. The visual symptoms of these cases were all reversible. Up to now, no case was reported that the visual symptoms was irreversible, except this one. Case Presentation: A 39-year-old man was sent to emergency department for taking over dosage of 800mg sildenafil citrate (trade name Viagra) to commit suicide. Visual symptoms appeared 4 hours later, including photophobia, blue halo in center field and gray stripes over red background. Sildenafil citrate toxicity caused the damage to outer layer of retina, including of myoid zone, ellipsoidal zone and interdigitation zone on OCT. Pattern visual evoked potential (P-VEP) demonstrated that the amplitudes of bilateral 1 degree spatial frequency P100 was declined mildly, and full-field electroretinogram (ERG) showed slightly-reduced amplitudes of dark-adapted ERG b-wave in both eyes. The patient was diagnosed as bilateral drug toxic retinopathy and ametropia. He was treated with compound anisodine hydrobromide. At 3-week follow-up, myoid zone, ellipsoidal zone and interdigitation zone of macular was improved on OCT, the amplitude of bilateral 1 degree spatial frequency P100 and dark-adapted ERG b-wave was improved slightly, but still remained abnormal. However, the visual symptoms did not improve any more over more than 1 year. Conclusions: High dose of sildenafil may lead to irreversible death of the photoreceptor cells and permanent visual impairment. The ocular side effects of recommended dose and potential visual risks of drug overdose should be paid more attention. Keywords: Sildenafil citrate, high dose, anomalopia, persistent, outer layer of retina.

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

Automatic measurement of SAED patterns from asbestos minerals

1988 ◽  
Vol 46 ◽  
pp. 846-847
Author(s):  
J. C. Russ ◽  
T. Taguchi ◽  
P. M. Peters ◽  
E. Chatfield ◽  
J. C. Russ ◽  
...  
Keyword(s):  
Diffraction Pattern ◽  
High Precision ◽  
Diffraction Data ◽  
Automatic Measurement ◽  
Automatic Method ◽  
Important Method ◽  
X Ray ◽  
Integrated Intensity ◽  
Asbestiform Minerals ◽  
True Center

Conventional SAD patterns as obtained in the TEM present difficulties for identification of materials such as asbestiform minerals, although diffraction data is considered to be an important method for making this purpose. The preferred orientation of the fibers and the spotty patterns that are obtained do not readily lend themselves to measurement of the integrated intensity values for each d-spacing, and even the d-spacings may be hard to determine precisely because the true center location for the broken rings requires estimation. We have implemented an automatic method for diffraction pattern measurement to overcome these problems. It automatically locates the center of patterns with high precision, measures the radius of each ring of spots in the pattern, and integrates the density of spots in that ring. The resulting spectrum of intensity vs. radius is then used just as a conventional X-ray diffractometer scan would be, to locate peaks and produce a list of d,I values suitable for search/match comparison to known or expected phases.

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