Parametric Study of Apertured Focused Gaussian Beams

Holmes, D. A.; Korka, J E; Avizonis, Petras V.

doi:10.1364/ao.11.000565

Cited by 78 publications

(12 citation statements)

References 6 publications

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“…However, when N is small the distribution of light on either side of the focus becomes asymmetrical. In particular, the peak of the axial intensity moves closer to the lens than is predicted by geometric optics (Holmes et al, 1972; Li and Wolf, 1981; Stavenga, 2003). At visible wavelengths N for the human eye is large, but that is not true in the infrared range.…”

Section: Adaptive Advantages Of a Fovea?mentioning

confidence: 87%

Adaptation of the central retina for high acuity vision: Cones, the fovea and the avascular zone

Provis

Dubis

Maddess

et al. 2013

Progress in Retinal and Eye Research

236

231

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Presence of a fovea centralis is directly linked to molecular specification of an avascular area in central retina, before the fovea (or `pit') begins to form. Modeling suggests that mechanical forces, generated within the eye, initiate formation of a pit within the avascular area, and its later remodeling in the postnatal period. Within the avascular area the retina is dominated by `midget' circuitry, in which signals are transferred from a single cone to a single bipolar cell, then a single ganglion cell. Thus in inner, central retina there are relatively few lateral connections between neurons. This renders the region adaptable to tangential forces, that translocate of ganglion cells laterally / centrifugally, to form the fovea. Optical coherence tomography enables live imaging of the retina, and shows that there is greater variation in the morphology of foveae in humans than previously thought. This variation is associated with differences in size of the avascular area and appears to be genetically based, but can be modified by environmental factors, including prematurity. Even when the fovea is absent (foveal hypoplasia), cones in central retina adopt an elongated and narrow morphology, enabling them to pack more densely to increase the sampling rate, and to act as more effective waveguides. Given these findings, what then is the adaptive advantage of a fovea? We suggest that the advantages of having a pit in central retina are relatively few, and minor, but together work to enhance acuity.

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Section: Adaptive Advantages Of a Fovea?mentioning

confidence: 87%

Adaptation of the central retina for high acuity vision: Cones, the fovea and the avascular zone

Provis

Dubis

Maddess

et al. 2013

Progress in Retinal and Eye Research

236

231

View full text Add to dashboard Cite

show abstract

“…On the other hand, it has been shown that when a plane wave is focused by a circular aperture lens with a very low Fresnel number, the position of the maximum intensity is not at the geometric focus of the lens, but at a point somewhat closer to the lens. This effect is commonly known as the focal shift [15][16][17][18][19] and has received a lot of attention [20,21]. Most of the investigations are confined to the vacuum or homogeneous media, while the case of inhomogeneous media attracts little interest.…”

Section: Introductionmentioning

confidence: 99%

Manipulating the focal shift in a medium with electromagnetically induced transparency

Wang

Cheng

Han

2008

Journal of Modern Optics

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By approximating the index distribution of a medium with electromagnetically induced transparency (EIT) as a gradient index (GRIN), propagation laws in the medium with EIT can be obtained. Transmission properties in an optical system with an EIT medium are analyzed. The results show that, unlike the case in the ordinary GRIN medium, the refractive index of EIT medium has the better controllability. Consequently, discussions are focused on how to conveniently manipulate the focal shift of the input in the EIT by means of controlling the index of the medium. Additionally, the speckle radius on the location of the actual focus can be diminished by adjusting some parameters in the EIT medium.

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“…The three-dimensional irradiance distribution in low-Fresnel-number focusing systems has been analytically evaluated [5,6], and experimental evidence of the presence of a focal shift has been reported elsewhere [7,8]. Much more previously it had been found that a very similar phenomenon also exists if the focused beam is an unapertured [9] or a truncated Gaussian laser beam [10], but only after Li and Wolf studies has been recognized that the relative focal shift can be expressed in terms of an effective Fresnel number [11,12].…”

Section: Introductionmentioning

confidence: 99%

Focal shift in optical waves with off-axis focus

Zapata–Rodríguez

Saavedra

Martı́nez-Corral

2003

Optics Communications

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We present a formulation for a suitable description of the focal shift in optical waves that have an off-axis focus. This shift that is primarily produced along the chief axis is given in terms of the focal distance and depends only on a parameter that is named as the generalized Fresnel number. Any non-uniform, either truncated and non-apertured optical beam with off-axis focus may be considered.

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Parametric Study of Apertured Focused Gaussian Beams

Cited by 78 publications

References 6 publications

Adaptation of the central retina for high acuity vision: Cones, the fovea and the avascular zone

Adaptation of the central retina for high acuity vision: Cones, the fovea and the avascular zone

Manipulating the focal shift in a medium with electromagnetically induced transparency

Focal shift in optical waves with off-axis focus

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