scholarly journals Geometric model of image formation in Scheimpflug cameras

2016 ◽  
Author(s):  
Indranil Sinharoy ◽  
Prasanna Rangarajan ◽  
Marc P. Christensen
Keyword(s):  
Pupil Diameter ◽  
Geometric Model ◽  
Image Formation ◽  
Imaging Systems ◽  
Depth Of Field ◽  
Entrance Pupil ◽  
Scheimpflug Imaging ◽  
The Relationship ◽  
Special Case ◽  
Entrance Pupil Diameter

We present a geometric model of image formation in Scheimpflug cameras that is most general. Scheimpflug imaging is commonly used is scientific and medical imaging either to increase the depth of field of the imager or to focus on tilted object surfaces. Existing Scheimpflug imaging models do not take into account the effect of pupil magnification (i.e. the ratio of the exit pupil diameter to the entrance pupil diameter), which we have found to affect the type of distortions experienced by the image-field upon lens rotations. In this work, we have also derived the relationship between the object, lens and sensor planes in Scheimpflug configuration, which is very similar in form with the standard Gaussian imaging equation, but applicable for imaging systems in which the lens plane and the sensor plane are arbitrarily oriented with respect to each other. Since the conventional rigid camera, in which the sensor and lens planes are constrained to be parallel to each other, is a special case of the Scheimpflug camera, our model also applies to imaging with conventional cameras.

scholarly journals Geometric model of image formation in Scheimpflug cameras

2016 ◽  
Author(s):  
Indranil Sinharoy ◽  
Prasanna Rangarajan ◽  
Marc P. Christensen
Keyword(s):  
Pupil Diameter ◽  
Geometric Model ◽  
Image Formation ◽  
Imaging Systems ◽  
Depth Of Field ◽  
Entrance Pupil ◽  
Scheimpflug Imaging ◽  
The Relationship ◽  
Special Case ◽  
Entrance Pupil Diameter

We present a geometric model of image formation in Scheimpflug cameras that is most general. Scheimpflug imaging is commonly used is scientific and medical imaging either to increase the depth of field of the imager or to focus on tilted object surfaces. Existing Scheimpflug imaging models do not take into account the effect of pupil magnification (i.e. the ratio of the exit pupil diameter to the entrance pupil diameter), which we have found to affect the type of distortions experienced by the image-field upon lens rotations. In this work, we have also derived the relationship between the object, lens and sensor planes in Scheimpflug configuration, which is very similar in form with the standard Gaussian imaging equation, but applicable for imaging systems in which the lens plane and the sensor plane are arbitrarily oriented with respect to each other. Since the conventional rigid camera, in which the sensor and lens planes are constrained to be parallel to each other, is a special case of the Scheimpflug camera, our model also applies to imaging with conventional cameras.

scholarly journals Catadioptric Optical System Design of 15-Magnitude Star Sensor with Large Entrance Pupil Diameter

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5501
Author(s):  
Yang Bai ◽  
Jianlin Li ◽  
Rongwei Zha ◽  
Ying Wang ◽  
Guangzhi Lei
Keyword(s):  
Optical System ◽  
Attitude Control ◽  
Pupil Diameter ◽  
Focal Length ◽  
Field Of View ◽  
Star Sensor ◽  
Spherical Lens ◽  
Entrance Pupil ◽  
Secondary Mirror ◽  
Entrance Pupil Diameter

The optical system is one of the core components for star sensors, whose imaging quality directly influences the performance of star sensors for star detection, thereby determining the attitude control accuracy of spacecrafts. Here, we report a new type of optical system with a catadioptric structure and a large entrance pupil diameter for a 15-magnitude star sensor. It consists of an improved Cassegrain system (R-C system), an aperture correction spherical lens group and a field of view correction spherical lens group. By embedding the secondary mirror of the R-C system into the output surface of the negative spherical lens of the aperture correction spherical lens group, the blocking of incident light is eliminated from the secondary mirror holder. After the structure optimization, the catadioptric optical system (COS) had a spectral range of 450 nm–950 nm, an entrance pupil diameter of 250 mm, a half-diagonal field of view of 1.4° and a focal length of 390 mm. By using theoretical calculations and experimental measurements, it was verified that the COS, with the ability to correct astigmatism, lateral color and distortion, can fulfill the detection of 15-magnitude dark stars.

scholarly journals Diversification of Regional Marketing Cooperatives

1977 ◽  
Vol 9 (1) ◽  
pp. 191-195 ◽  
Author(s):  
Thomas L. Sporleder ◽  
Robert A. Skinner
Keyword(s):  
Conventional Wisdom ◽  
The Relationship ◽  
Marketing Cooperatives ◽  
Special Case

Several definitions of diversification exist. Typically, the concept is dynamic and refers to the relationship among various activities or enterprises in which the firm is engaged. As new activities are acquired by a firm from some existing base of activities, complementarity of the newly acquired activity relative to the existing base is subjectively determined. Judgment is rendered on whether the result represents diversification or conglomeration.Conventional wisdom has not succinctly differentiated between diversification and conglomeration. Some writers have considered conglomeration a special case of diversification [2, 7]. For purposes of this paper, this taxonomic argument need not be settled.

TORUS KNOTS EMBODYING CURVATURE AND TORSION IN AN OTHERWISE FEATURELESS CONTINUUM

2011 ◽  
Vol 20 (12) ◽  
pp. 1723-1739 ◽  
Author(s):  
J. S. AVRIN
Keyword(s):  
Elementary Particle ◽  
General Relativity ◽  
Geometric Model ◽  
The Other ◽  
Particle Model ◽  
Torus Knots ◽  
Torus Knot ◽  
The Subject ◽  
Curvature And Torsion ◽  
The Relationship

The subject is a localized disturbance in the form of a torus knot of an otherwise featureless continuum. The knot's topologically quantized, self-sustaining nature emerges in an elementary, straightforward way on the basis of a simple geometric model, one that constrains the differential geometric basis it otherwise shares with General Relativity (GR). Two approaches are employed to generate the knot's solitonic nature, one emphasizing basic differential geometry and the other based on a Lagrangian. The relationship to GR is also examined, especially in terms of the formulation of an energy density for the Lagrangian. The emergent knot formalism is used to derive estimates of some measurable quantities for a certain elementary particle model documented in previous publications. Also emerging is the compatibility of the torus knot formalism and, by extension, that of the cited particle model, with general relativity as well as with the Dirac theoretic notion of antiparticles.

scholarly journals An evolutionary process without variation and selection

2021 ◽  
Vol 18 (180) ◽  
pp. 20210334
Author(s):  
Liane Gabora ◽  
Mike Steel
Keyword(s):  
Germ Cells ◽  
Cultural Evolution ◽  
Self Assembly ◽  
Early Life ◽  
Evolutionary Process ◽  
Adaptive Change ◽  
Assembly Code ◽  
The Relationship ◽  
Special Case ◽  
Variation And Selection

Natural selection successfully explains how organisms accumulate adaptive change despite that traits acquired over a lifetime are eliminated at the end of each generation. However, in some domains that exhibit cumulative, adaptive change—e.g. cultural evolution, and earliest life—acquired traits are retained; these domains do not face the problem that Darwin’s theory was designed to solve. Lack of transmission of acquired traits occurs when germ cells are protected from environmental change, due to a self-assembly code used in two distinct ways: (i) actively interpreted during development to generate a soma, and (ii) passively copied without interpretation during reproduction to generate germ cells. Early life and cultural evolution appear not to involve a self-assembly code used in these two ways. We suggest that cumulative, adaptive change in these domains is due to a lower-fidelity evolutionary process, and model it using reflexively autocatalytic and foodset-generated networks. We refer to this more primitive evolutionary process as self–other reorganization (SOR) because it involves internal self-organizing and self-maintaining processes within entities, as well as interaction between entities. SOR encompasses learning but in general operates across groups. We discuss the relationship between SOR and Lamarckism, and illustrate a special case of SOR without variation.

scholarly journals Anterior-Segment Swept-Source Ocular Coherence Tomography and Scheimpflug Imaging Agreement for Keratometry and Pupil Measurements in Healthy Eyes

2021 ◽  
Vol 10 (24) ◽  
pp. 5789
Author(s):  
Francisco Pérez-Bartolomé ◽  
Carlos Rocha-De-Lossada ◽  
José-María Sánchez-González ◽  
Silvia Feu-Basilio ◽  
Josep Torras-Sanvicens ◽  
...  
Keyword(s):  
Pupil Diameter ◽  
Anterior Segment ◽  
Swept Source ◽  
Ocular Coherence Tomography ◽  
Scheimpflug Imaging ◽  
Angle Kappa ◽  
Student’S T ◽  
Thickness Measurements ◽  
Healthy Eyes ◽  
Student’S T Test

This study examines agreement between the devices Anterion® and Pentacam HR® used for corneal and pupil measurements in healthy eyes. The parameters compared between the two devices were: anterior Km (D), anterior K2 (D), anterior K1 (D), anterior K1 axis (°), anterior astigmatism (D), anterior K max (D), posterior Km (D), posterior K2 (D), posterior K1 (D), posterior K1 axis (°), posterior astigmatism (D), CCT (µm), thinnest point thickness (µm), thinnest point X-coordinate (mm), thinnest point Y-coordinate (mm), pupil diameter (mm), pupil center-corneal vertex distance (mm) (angle kappa), pupil centroid angle (°), pupil centroid X-coordinate (mm), and pupil centroid Y-coordinate (mm). The Student’s t test for independent samples identified significant differences (p < 0.005) between devices for the measurements anterior and posterior flat K axis, posterior flat K, steep K, and mean K. For these last three measurements, although significant, none of the differences were clinically relevant. Corneal power and thickness measurements except Kf axis showed excellent agreement between Anterion and Pentacam. In a clinical setting we would not recommend the interchangeable use of Pentacam and Anterion for measurement of pupil parameters.

The Improvement and Quantitative Assessment of B-Mode Images Produced by an Annular Array/Cone Hybrid

1983 ◽  
Vol 5 (3) ◽  
pp. 195-213 ◽  
Author(s):  
M. S. Patterson ◽  
F. S. Foster
Keyword(s):  
Quantitative Assessment ◽  
Breast Tissue ◽  
Imaging Systems ◽  
Depth Of Field ◽  
Scattering Medium ◽  
Human Breast ◽  
Human Breast Tissue ◽  
New Approach ◽  
Annular Array

Hybrid ultrasound imaging systems, which combine spherical focusing on transmit with axicon focusing on receive, provide excellent resolution over a useful depth of field. This paper presents a new hybrid design with improved sensitivity, in which the axicon focusing is achieved by two conical mirrors and a PZT 5A disk cut into 8 sectors. We have investigated two methods of processing the signals from the 8 sectors. In the first, phase insensitive sector addition (PISA), the B-scan is formed from the sum of the 8 demodulated signals. In the second, multiplicative processing (MP), the 8 rf waveforms are multiplied and the resultant is demodulated to form the image. Both techniques result in smoothed speckle but degraded lateral resolution. As well, MP decreases the off-axis sensitivity of the system and artifacts characteristic of axicon focusing. Quantitative assessment of the effects of PISA and MP was performed using a new approach called contrast-to-speckle ratio (CSR). The CSR data, which is a measure of the image contrast of cylindrical voids in a random scattering medium relative to contrast fluctuations due to speckle, shows the superiority of PISA and MP. This conclusion is supported by images of in vitro human breast tissue.

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