682 results on '"Gaussian optics"'
Search Results
2. Barrett Formulas: Strategies to Improve IOL Power Prediction
- Author
-
Barrett, Graham D., Singh, Arun D., Series Editor, Aramberri, Jaime, editor, Hoffer, Kenneth J., editor, Olsen, Thomas, editor, Savini, Giacomo, editor, and Shammas, H. John, editor
- Published
- 2024
- Full Text
- View/download PDF
3. Gaussian Optics : Basic Optics
- Author
-
Colliac, Jean-Philippe, Singh, Arun D., Series Editor, Aramberri, Jaime, editor, Hoffer, Kenneth J., editor, Olsen, Thomas, editor, Savini, Giacomo, editor, and Shammas, H. John, editor
- Published
- 2024
- Full Text
- View/download PDF
4. Optical Imaging
- Author
-
Merlitz, Holger and Merlitz, Holger
- Published
- 2023
- Full Text
- View/download PDF
5. OKULIX ray-tracing software versus third generation formulas: compatibility or superiority?
- Author
-
Karim M. Nabil
- Subjects
gaussian optics ,intraocular lens calculation ,okulix ray-tracing software ,third-generation formulas ,Ophthalmology ,RE1-994 - Abstract
Purpose The aim of this retrospective study was to compare the accuracy of intraocular lens (IOL) power calculation using the OKULIX ray-tracing software compared with third generation IOL power calculation formulas. Patients and methods The study included 80 consecutive eyes of 80 patients (26 males and 54 females, with a mean age of 58.8±15.1 years), for whom phacoemulsification and IOL implantation was performed following biometry using the OKULIX ray-tracing software and third-generation IOL power calculation formulas for IOL power calculation. Accuracy of IOL power calculation was investigated by subtracting the attempted and achieved spherical equivalent 1 month postoperatively and was recorded as the mean absolute error. Results OKULIX ray-tracing software calculated IOL power was 17.1±8.5 diopters (D), which was statistically significantly different from Sanders, Retzlaff, Kraff (SRK)-T, Hoffer Q, SRK II, and Holladay formulas (16.7±8.3, 16.6±8.7, 16.8±8, and 16.7±8.5 D, respectively, P
- Published
- 2022
- Full Text
- View/download PDF
6. The Castrop formula for calculation of toric intraocular lenses.
- Author
-
Langenbucher, Achim, Szentmáry, Nóra, Cayless, Alan, Weisensee, Johannes, Wendelstein, Jascha, and Hoffmann, Peter
- Subjects
- *
INTRAOCULAR lenses , *CORNEA , *ASTIGMATISM - Abstract
Purpose: To explain the concept behind the Castrop toric lens (tIOL) power calculation formula and demonstrate its application in clinical examples. Methods: The Castrop vergence formula is based on a pseudophakic model eye with four refractive surfaces and three formula constants. All four surfaces (spectacle correction, corneal front and back surface, and toric lens implant) are expressed as spherocylindrical vergences. With tomographic data for the corneal front and back surface, these data are considered to define the thick lens model for the cornea exactly. With front surface data only, the back surface is defined from the front surface and a fixed ratio of radii and corneal thickness as preset. Spectacle correction can be predicted with an inverse calculation. Results: Three clinical examples are presented to show the applicability of this calculation concept. In the 1st example, we derived the tIOL power for a spherocylindrical target refraction and corneal tomography data of corneal front and back surface. In the 2nd example, we calculated the tIOL power with keratometric data from corneal front surface measurements, and considered a surgically induced astigmatism and a correction for the corneal back surface astigmatism. In the 3rd example, we predicted the spherocylindrical power of spectacle refraction after implantation of any toric lens with an inverse calculation. Conclusions: The Castrop formula for toric lenses is a generalization of the Castrop formula based on spherocylindrical vergences. The application in clinical studies is needed to prove the potential of this new concept. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
7. Optimal collection of radiation emitted by a trapped atomic ensemble.
- Author
-
Kurkó, Árpád, Domokos, Peter, Vukics, András, Bækkegaard, Thomas, Zinner, Nikolaj Thomas, Fortágh, József, and Petrosyan, David
- Subjects
RADIATION ,PHOTON emission ,OPTICS ,GAUSSIAN distribution ,PHOTONS - Abstract
Trapped atomic ensembles are convenient systems for quantum information storage in the long-lived sublevels of the electronic ground state and its conversion to propagating optical photons via stimulated Raman processes. Here we investigate a phase-matched emission of photons from a coherently prepared atomic ensemble. We consider an ensemble of cold atoms in an elongated harmonic trap with normal density distribution, and determine the parameters of paraxial optics to match the mode geometry of the emitted radiation and optimally collect it into an optical waveguide. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
8. Human eye ocular component analysis for refractive state and refractive surgery
- Author
-
Chao-Kai Chang, Jui-Teng Lin, and Yong Zhang
- Subjects
1080 ,Gaussian optics ,human eye ocular components ,refractive errors ,vision correction laser in situ keratomileusis ,corneal collagen crosslinking ,Ophthalmology ,RE1-994 - Abstract
AIM: To analyze the clinical factors influencing the human vision corrections via the changing of ocular components of human eye in various applications; and to analyze refractive state via a new effective axial length. METHODS: An effective eye model was introduced by the ocular components of human eye including refractive indexes, surface radius (r1, r2, R1, R2) and thickness (t, T) of the cornea and lens, the anterior chamber depth (S1) and the vitreous length (S2). Gaussian optics was used to calculate the change rate of refractive error per unit amount of ocular components of a human eye (the rate function M). A new criterion of myopia was presented via an effective axial length. RESULTS: For typical corneal and lens power of 42 and 21.9 diopters, the rate function Mj (j=1 to 6) were calculated for a 1% change of r1, r2, R1, R2, t, T (in diopters) M1=+0.485, M2=-0.063, M3=+0.053, M4=+0.091, M5=+0.012, and M6=-0.021 diopters. For 1.0 mm increase of S1 and S2, the rate functions were M7=+1.35, and M8=-2.67 diopter/mm, respectively. These rate functions were used to analyze the clinical outcomes in various applications including laser in situ keratomileusis surgery, corneal cross linking procedure, femtosecond laser surgery and scleral ablation for accommodation. CONCLUSION: Using Gaussian optics, analytic formulas are presented for the change of refractive power due to various ocular parameter changes. These formulas provide useful clinical guidance in refractive surgery and other related procedures.
- Published
- 2017
- Full Text
- View/download PDF
9. Spatiotemporal coupling of attosecond pulses.
- Author
-
Wikmark, Hampus, Chen Guo, Vogelsang, Jan, Smorenburg, Peter W., Coudert-Alteirac, Hélène, Lahl, Jan, Peschel, Jasper, Rudawski, Piotr, Dacasa, Hugo, Carlström, Stefanos, Maclot, Sylvain, Gaarde, Mette B., Johnsson, Per, Arnold, Cord L., and L'Huillier, Anne
- Subjects
- *
SPATIOTEMPORAL processes , *ATTOSECOND pulses , *FEMTOSECOND lasers , *LASER pulses , *LASERS , *LASER beams - Abstract
The shortest light pulses produced to date are of the order of a few tens of attoseconds, with central frequencies in the extreme UV range and bandwidths exceeding tens of electronvolts. They are often produced as a train of pulses separated by half the driving laser period, leading in the frequency domain to a spectrum of high, odd-order harmonics. As light pulses become shorter and more spectrally wide, the widely used approximation consisting of writing the optical waveform as a product of temporal and spatial amplitudes does not apply anymore. Here, we investigate the interplay of temporal and spatial properties of attosecond pulses. We show that the divergence and focus position of the generated harmonics often strongly depend on their frequency, leading to strong chromatic aberrations of the broadband attosecond pulses. Our argument uses a simple analytical model based on Gaussian optics, numerical propagation calculations, and experimental harmonic divergence measurements. This effect needs to be considered for future applications requiring highquality focusing while retaining the broadband/ultrashort characteristics of the radiation. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
10. Equivalence theory for cross-format photographic image quality comparisons.
- Author
-
Rowlands, D. Andrew
- Subjects
- *
IMAGING systems , *DIGITAL image processing - Abstract
Equivalence theory is commonly used by photographers in order to obtain equivalent photographs from cameras based on different sensor formats. A complete mathematical proof of equivalence theory that is valid for compound photographic lenses with any chosen pupil magnification is presented. An expression for a correction to the conventional equivalence formulae is derived, which is proven to be formally required whenever focus is set closer than infinity, although numerically significant only for macro photography. Additionally, this paper argues that equivalence theory should be used in practice to appropriately perform cross-format image quality comparisons and demonstrates how various common metrics should be evaluated. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
11. Optimization of an Offset Receiver Optics for Radio Telescopes.
- Author
-
Yeap, Kim and Tham, Choy
- Subjects
- *
ANTENNAS (Electronics) , *RADIO telescopes , *CASSEGRAINIAN telescopes , *RADIO astronomy , *RECEIVING antennas , *PHYSICAL optics - Abstract
The latest generation of Cassegrain radio astronomy antennas is designed for multiple frequency bands with receivers for individual bands offset from the antenna axis. The offset feed arrangement typically has two focusing elements in the form of ellipsoidal mirrors in the optical path between the feed horn and the antenna focus. This arrangement aligns the beam from the offset feed horn to illuminate the subreflector. The additional focusing elements increase the number of design variables, namely the distances between the horn aperture and the first mirror and that between the two mirrors, and their focal lengths. There are a huge number of possible combinations of these four variables in which the optics system can take on. The design aim is to seek the combination that will give the optimum antenna efficiency, not only at the centre frequency of the particular band but also across its bandwidth. To pick the optimum combination of the variables, it requires working through, by computational mean, a continuum range of variable values at different frequencies which will fit the optics system within the allocated physical space. Physical optics (PO) is a common technique used in optics design. However, due to the repeated iteration of the huge number of computation involved, the use of PO is not feasible. We present a procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance. The best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper. The optimization procedure uses the beam's edge taper at the subreflector as the iteration target. The band 6 receiver optics design for the Atacama Large Millimetre Array (ALMA) antenna is used to illustrate the optimization procedure. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
12. Yves Le Grand on matrices in optics with application to vision: Translation and critical analysis
- Author
-
William Frith Harris
- Subjects
Le Grand ,Gaussian optics ,linear optics ,dioptric power matrix ,ray transference ,condition for clear retinal images ,condition for undistorted images ,astigmatism ,Ophthalmology ,RE1-994 - Abstract
An appendix to Le Grand’s 1945 book, Optique Physiologique: Tome Premier: La Dioptrique de l’Œil et Sa Correction, briefly dealt with the application of matrices in optics. However the appendix was omitted from the well-known English translation, Physiological Optics, which appeared in 1980. Consequently the material is all but forgotten. This is unfortunate in view of the importance of the dioptric power matrix and the ray transference which entered the optometric literature many years later. Motivated by the perception that there has not been enough care in optometry to attribute concepts appropriately this paper attempts a careful analysis of Le Grand’s thinking as reflected in his appendix. A translation into English is provided in the appendix to this paper. The paper opens with a summary of the basics of Gaussian and linear optics sufficient for the interpretation of Le Grand’s appendix which follows. The paper looks more particularly at what Le Grand says in relation to the transference and the dioptric power matrix though many other issues are also touched on including the conditions under which distant objects will map to clear images on the retina and, more particularly, to clear images that are undistorted. Detailed annotations of Le Grand’s translated appendix are provided. (S Afr Optom 2013 72(4) 145-166)
- Published
- 2013
- Full Text
- View/download PDF
13. The Castrop formula for calculation of toric intraocular lenses
- Author
-
Jascha Wendelstein, Johannes Weisensee, Achim Langenbucher, Nóra Szentmáry, Alan Cayless, and Peter Hoffmann
- Subjects
Surface (mathematics) ,Physics::Medical Physics ,Astigmatism ,Vergence calculation ,Refraction, Ocular ,Cataract ,law.invention ,Cornea ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,0302 clinical medicine ,Optics ,law ,medicine ,Castrop formula ,Humans ,Physics ,Lenses, Intraocular ,Phacoemulsification ,Gaussian optics ,business.industry ,Toric intraocular lenses ,medicine.disease ,Refraction ,Sensory Systems ,Toric lens ,Vergence (optics) ,Lens (optics) ,Ophthalmology ,medicine.anatomical_structure ,Eyeglasses ,030221 ophthalmology & optometry ,business ,030217 neurology & neurosurgery ,Prediction of postoperative refraction - Abstract
Purpose To explain the concept behind the Castrop toric lens (tIOL) power calculation formula and demonstrate its application in clinical examples. Methods The Castrop vergence formula is based on a pseudophakic model eye with four refractive surfaces and three formula constants. All four surfaces (spectacle correction, corneal front and back surface, and toric lens implant) are expressed as spherocylindrical vergences. With tomographic data for the corneal front and back surface, these data are considered to define the thick lens model for the cornea exactly. With front surface data only, the back surface is defined from the front surface and a fixed ratio of radii and corneal thickness as preset. Spectacle correction can be predicted with an inverse calculation. Results Three clinical examples are presented to show the applicability of this calculation concept. In the 1st example, we derived the tIOL power for a spherocylindrical target refraction and corneal tomography data of corneal front and back surface. In the 2nd example, we calculated the tIOL power with keratometric data from corneal front surface measurements, and considered a surgically induced astigmatism and a correction for the corneal back surface astigmatism. In the 3rd example, we predicted the spherocylindrical power of spectacle refraction after implantation of any toric lens with an inverse calculation. Conclusions The Castrop formula for toric lenses is a generalization of the Castrop formula based on spherocylindrical vergences. The application in clinical studies is needed to prove the potential of this new concept.
- Published
- 2022
- Full Text
- View/download PDF
14. Measurement range expansion of single-beam Laser Doppler velocimeter based on a focusing transmitter.
- Author
-
Chen, Lanjian, Zhou, Jian, Nie, Xiaoming, and Jin, Shilong
- Subjects
- *
LASER Doppler velocimeter , *OPTICAL transmitters , *GAUSSIAN beams , *TRANSMITTERS (Communication) , *VELOCITY measurements - Abstract
The own velocity of a ground vehicle with high precision provided by the single-beam Laser Doppler velocimeters (LDV) promotes the localization accuracy of vehicles efficiently. However, the present LDVs are unable to be mounted on air vehicles for the velocity measurement of vehicles so far because of the restricted working distance. In order to expand the measuring range, a mid-distance LDV is designed in this paper. An optical focusing transmitter that transforms the Gaussian beam waist to the pre-set distance with an appropriate radius is constructed through theoretical simulations. Further experiments show that the mid-distance velocimeter can measure the velocity of moving objects within 50 m and the signal quality of measurement holds at a high level. This improved single-beam LDV with a longer working distance has great potential in acquiring the high-precision velocity of low-altitude air vehicles and many other remote velocity measurement applications. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
15. Structural optics design of the zoom system based on particle swarm optimization.
- Author
-
Li, Hao, Wang, Dong, Chen, Guanghui, Zhao, Qian, and Piao, Yan
- Subjects
- *
PARTICLE swarm optimization , *SYSTEMS design , *STRUCTURAL design , *DIGITAL cameras - Abstract
Selection of initial structural parameters is an essential step for the zoom system design. In this paper, a new method based on Gaussian optics and Particle Swarm Optimization (PSO) algorithm is proposed to design initial structural parameters of the zoom system, and an optical automatic optimization design is carried out based on the initial structural parameters. Firstly, displacement parameters of the zoom group and the compensation group of the zoom system are derived based on Gaussian optics. Secondly, constraints of the zoom system are established using the PSO algorithm, and a fitness function is designed. Then, the initial structure parameters of the zoom system are optimized. Finally, uniform and monotonic movement of the cam curve is achieved in an example of a 6 × zoom system. The results indicate that our proposed methods improve the efficiency and accuracy of the zoom system design, which has guiding significance for the design of multi-group moving zoom system with high zoom ratio and other engineering applications. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
16. Gaussian optics and transfer matrices
- Author
-
Hermann Wollnik
- Subjects
Physics ,symbols.namesake ,Transfer (group theory) ,Gaussian function ,symbols ,Statistical physics ,Gaussian optics - Published
- 2022
17. Volumetric calibration for scheimpflug light-field PIV
- Author
-
Zhou Zhao and Shengxian Shi
- Subjects
Fluid Flow and Transfer Processes ,Pixel ,business.industry ,Computer science ,Scheimpflug principle ,Computational Mechanics ,General Physics and Astronomy ,computer.software_genre ,Particle image velocimetry ,Mechanics of Materials ,Voxel ,Feature (computer vision) ,Calibration ,Computer vision ,Artificial intelligence ,business ,computer ,Light field ,Gaussian optics - Abstract
This work presents a volumetric calibration method for Scheimpflug plenoptic camera in particle image velocimetry. To establish a prerequisite foundation for the Scheimpflug light-field PIV, the proposed technique makes use of the unique point-like pattern and plenoptic disc feature of particle light-field images to accurately determine affected pixels for a spatial voxel in a measurement volume. With Gaussian optics, an ideal projection model of the Scheimpflug plenoptic camera is derived to provide a basis for the calibration method. By taking lens defects, optical window’s imperfection, inaccurate tilted-angle and other practical application difficulties into account, the calibration method can establish the mapping relationship between a spatial voxel and its affected pixels correctly. The volumetric calibration method was validated by a classic vortex-ring PIV measurement where the correspondence between a voxel and its affected pixels was accurately determined and the volumetric velocity field was successfully acquired.
- Published
- 2021
18. General approach to the sensitivity of the optics of an eye to change in elementary parameters with application to the Gaussian optics of a reduced eye
- Author
-
W. F. Harris
- Subjects
sensitivity ,error ,transference ,derivative ,Gaussian optics ,reduced eye ,Ophthalmology ,RE1-994 - Abstract
Optical properties of the eye, including the refractive compensation, for example, may change if there are changes in any of the components that make up the eye. The sensitivity to such changes isquantified via the derivative. This paper employs the reduced eye and Gaussian optics to illustrate a general method for the analysis of sensitivity in eyes. The method requires a clear statement of the dependent variable as a function of independent variables. A symbolism is offered that makes the function unambiguous. Sensitivities are determined for the fundamental optical properties,the transference and the corneal-plane refractivecompensation of a reduced eye to change in corneal power, curvature and radius of curvature and to change in axial length and index of refraction. Emsley’s reduced eye is examined in particular. Its corneal-plane refractive compensation has a sensitivity of 135 −135 D to change in refractive index, 1 − 2.7 D/mm to change in length and 135 −1/3 to change in corneal curvature when the other two independent variables are held fixed. The method has the potential to develop guidelines that are useful clini- cally.
- Published
- 2009
- Full Text
- View/download PDF
19. Sensitivity of the corneal-plane refractive compensation to change in power and axial position of an intraocular lens
- Author
-
W. F. Harris
- Subjects
intraocular lens ,sensitivity ,axial displacement ,Gaussian optics ,refraction ,refractive compensation ,Gullstrand’s simplified eye. ,Ophthalmology ,RE1-994 - Abstract
If an intraocular lens is displaced or if its power is changed what are the consequences for the refractive compensation of the eye? Gaussian optics is used to obtain explicit formulae for the sensitivityof the corneal-plane refractive compensation (also called the refraction, refractive state, etc) to change in power and axial displacement of a thin intraocular lens implanted in a simple eye. In particular, for a pseudophakic Gullstrand simplified eye with intraocular lens placed 5 mm behind the cornea the sensitivity to errors in the power of the intraocular lens is about 71 . 0 − 71 for an intraocular lens of power for an intraocular lens of power 20 D, that is, the refractive compensation decreases by about 0.71 dioptres per dioptre increase in the power of the intraocular lens. More generally the sensitivity is approximately ( ) m 0037 . 0 63 . 0 F − − 0.63 ( 003 . 0 63 . 0 − − (0.0037m)F where FI is the power of the intraocular lens. Also for Gullstrand’s simplified eye the sensitivity of refractive compensation to axial displacement of the intraocular lens is approximately linear in FI about (64D) FI, in fact. That is, for each dioptre of the power of the intraocular lens the refractive compensation increases by about 0.064 dioptres per millimetre of axial displacement towards the retina.
- Published
- 2009
- Full Text
- View/download PDF
20. A new approach for tolerance sensitivity reduction in lens optimization by controlling the first order derivatives of real ray height on pupil
- Author
-
Qi Huang, Yimou Luo, and Xiaotong Li
- Subjects
Surface (mathematics) ,Computer science ,Image quality ,business.industry ,Displacement (vector) ,Image (mathematics) ,law.invention ,Lens (optics) ,Optics ,law ,Sensitivity (control systems) ,Reduction (mathematics) ,business ,Gaussian optics - Abstract
During the production of a new designed lens system, overweighted assembling and manufacturing errors can cause the degradation of the performance of the whole system. Therefore, optimizations to improve the assembling and manufacturing tolerances sensitivity are greatly required in lens design industry. Following the principle of Gaussian optics, there are some practical implications of the first order derivatives which are of great significance to analyse the sensitivity of a lens system with its structural parameters changing. It is demonstrated that manufacturing errors, such as tilting, decentering and so on, induce the real rays' height shifting on each surface of an imaging system, which subsequently induces the decline of image quality. Thus, we proposed a scheme to use the first order derivatives of the height of a real ray on the image surface in a lens system versus that on the pupil surface, which indicate the height variations of the real ray on the image surface of the lens system caused by the displacement of its corresponding height on the pupil surface, as a merit function to improve the tolerance sensitivity of the whole system. A test program using the ZPL language in Opticstudio has preliminarily confirmed the effectiveness of our proposed methods. And as it is aimed at controlling the real rays of a lens system to reduce its sensitivity according to assembling and manufacturing errors, our scheme is theoretically able to appropriate to all lens design systems.
- Published
- 2021
21. Einfaches Verfahren zur Abschätzung des postoperativen Abbildungsmaßstabs und der Aniseikonie bei der Kataraktoperation
- Author
-
Peter Hoffmann, Jascha Wendelstein, Achim Langenbucher, and Nóra Szentmáry
- Subjects
Biometry ,Computer science ,medicine.medical_treatment ,Magnification ,Intraocular lens ,Cataract Extraction ,Refraction, Ocular ,Originalien ,Retinal image size ,Cataract ,law.invention ,Optics ,law ,Linsenberechnung ,medicine ,Aniseikonia ,Humans ,Lenses, Intraocular ,business.industry ,Abbildungsmaßstab ,Retinale Bildgröße ,Cataract surgery ,Aniseikonie ,Lens power calculation ,Refraction ,Lens (optics) ,Vergence (optics) ,Ophthalmology ,Ocular magnification ,business ,Biometrie ,Gaussian optics - Abstract
Aniseikonia as one of the major risk factors for asthenopic problems is mostly overlooked in modern cataract surgery. The purpose of this study was to develop a simple calculation scheme for clinicians to predict the object to image magnification in a pseudophakic eye with biometric data.The calculation scheme for object to image magnification in the pseudophakic eye is based on a vergence calculation of the lens power with theoretical optical formulae. From the biometric data, which are typically derived from both eyes during lens power calculation, the vergences in front of and behind the 3 or 4 refractive surfaces of the pseudophakic eye model are used to predict the magnification for objects at infinity or objects located at a finite measurement distance (e.g. 5 m).With a formula-based lens power calculation a pseudophakic eye model is set up with 3 or 4 refractive surfaces (postoperative spectacle refraction; thick cornea described by anterior surface or thick cornea characterized by anterior and posterior surfaces; intraocular lens). The vergence in front of and behind each refractive surface is derived by means of linear Gaussian optics. The quotient of the product of all vergences in front of the surfaces and the product of all vergences behind the respective surfaces describes the object to image magnification of the eye. A comparison of the object to image magnification of both eyes yields the retinal image size disparity or aniseikonia. This calculation strategy is shown in a step-by-step approach exemplarily for the Haigis and Hoffer‑Q formulae (3 surfaces) and the Castrop formula (4 surfaces).If during planning and lens power calculation biometry is performed for both eyes, ocular magnification of both eyes can be easily derived with this calculation scheme and aniseikonia can be extracted from a comparison of magnification of both eyes. Such a simple prediction should be established as a standard for precataract biometry and lens power calculation for early detection and avoidance of asthenopic complaints after cataract surgery.HINTERGRUND UND ZIELSETZUNG: Die Aniseikonie als mögliche Ursache asthenopischer Beschwerden tritt bei der modernen Kataraktchirurgie oft in den Hintergrund. Ziel der vorliegenden Arbeit ist es, dem Kliniker ein einfaches Berechnungsmodell an die Hand zu geben, mit dem der Abbildungsmaßstab des pseudophaken Auges abgeschätzt werden kann.Das Berechnungsschema für den Abbildungsmaßstab des pseudophaken Auges bezieht sich auf die formelbasierte (vergenzbasierte) Berechnung der Intraokularlinse mit theoretisch-optischen Formeln. Aus den biometrischen Größen, die in der Regel für beide Augen bei der Linsenberechnung vorliegen, kann aus den Vergenzen vor und hinter den 3 oder 4 refraktiven Grenzflächen im pseudophaken Augenmodell der Abbildungsmaßstab für Objekte im Unendlichen oder in einer endlichen Messdistanz ermittelt werden.Bei der formelbasierten Berechnung wird ein pseudophakes Augenmodell mit 3 bzw. 4 refraktiven Grenzflächen (postoperative Brillenrefraktion; dünne Hornhaut, beschrieben durch die Vorderfläche, bzw. dicke Hornhaut, beschrieben durch die Vorder- und Rückfläche; Intraokularlinse) definiert und mit den Methoden der linearen Optik die Vergenz vor und hinter jeder Grenzfläche bestimmt. Der Quotient aus dem Produkt der Vergenzen vor den Grenzflächen und dem Produkt der Vergenzen unmittelbar hinter den Grenzflächen beschreibt direkt den Abbildungsmaßstab des Auges. Aus dem Vergleich des Abbildungsmaßstabs beider Augen kann unmittelbar der retinale Bildgrößenunterschied ermittelt werden. Exemplarisch wird dies anhand der Haigis- und Hoffer-Q-Formel (3 Flächen) und der Castrop-Formel (4 Flächen) gezeigt.Wird bei der Planung der Kataraktoperation die Biometrie und Linsenberechnung an beiden Augen durchgeführt, so kann mit einfachen Mitteln der Abbildungsmaßstab bei beiden Augen und aus dem Vergleich beider Augen die Aniseikonie des pseudophaken Patienten ermittelt werden. Eine derartige Abschätzung sollte fester Bestandteil der Linsenberechnung werden, um mögliche asthenopische Beschwerden nach der Kataraktoperation früh zu erkennen.
- Published
- 2021
- Full Text
- View/download PDF
22. Optimal collection of radiation emitted by a trapped atomic ensemble
- Author
-
T. Bækkegaard, András Vukics, David Petrosyan, Árpád Kurkó, Peter Domokos, József Fortágh, and Nikolaj T. Zinner
- Subjects
Photon ,FOS: Physical sciences ,Physics::Optics ,Radiation ,01 natural sciences ,010305 fluids & plasmas ,quant-ph ,0103 physical sciences ,Cold atoms ,quantum optics ,Physics::Atomic Physics ,Electrical and Electronic Engineering ,Quantum information ,010306 general physics ,Condensed Matter::Quantum Gases ,Physics ,Quantum Physics ,Paraxial approximation ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Control and Systems Engineering ,Single-photon source ,Atomic physics ,Quantum Physics (quant-ph) ,Ground state ,Microwave ,Gaussian optics - Abstract
Trapped atomic ensembles are convenient systems for quantum information storage in the long-lived sublevels of the electronic ground state and its conversion to propagating optical photons via stimulated Raman processes. Here we investigate a phase-matched emission of photons from a coherently prepared atomic ensemble. We consider an ensemble of cold atoms in an elongated harmonic trap with normal density distribution, and determine the parameters of paraxial optics to match the mode geometry of the emitted radiation and optimally collect it into an optical waveguide.
- Published
- 2021
23. A two-layer Shack-Hartmann wavefront sensor model of the human and mouse retinas
- Author
-
Vyas Akondi and Alfredo Dubra
- Subjects
Physics ,genetic structures ,business.industry ,Centroid ,Coma (optics) ,Wavefront sensor ,Lenslet ,eye diseases ,Spherical aberration ,Optics ,Fresnel number ,sense organs ,business ,Shack–Hartmann wavefront sensor ,Gaussian optics - Abstract
In the ophthalmic Shack-Hartmann wavefront sensor beacon light originates from various depths within the retina. We model the retina of the human and mouse eyes as formed by two backscattering planes, showing that the use of lenslets with low Fresnel number and/or too small search boxes in the centroiding algorithm will produce artifactual aberrations. We evaluate the impact of these errors for four common beacon illumination strategies: full circular, annular, small circular on-axis and small circular off-axis. We find that artifactual aberrations are larger for annular and off-axis beacon illumination, dominated by defocus plus spherical aberration and defocus plus coma, respectively. These artifactual aberrations can be almost completely eliminated by selecting the minimum centroid search box size based on a simple Gaussian optics model and ocular biometry, provided the lenslet Fresnel number is sufficiently large to introduce minimal cross-talk between images of adjacent lenslets.
- Published
- 2021
24. Considerations of a thick lens formula for intraocular lens power calculation.
- Author
-
Langenbucher A, Hoffmann P, Cayless A, Gatinel D, Debellemanière G, Wendelstein J, and Szentmáry N
- Abstract
Background: In recent years, some lens manufacturers have committed to providing lens shape data for some of their lens models. The purpose of this study is to present a strategy for prediction of intraocular lens power and residual refraction based on a pseudophakic model eye containing 5 refractive surfaces and to show its applicability using worked examples., Methods: A pseudophakic model eye with a thin spectacle correction, a thick cornea (radius of curvatures for both surfaces and central thickness) and a thick IOL (either radius of curvatures RLa and RLp for front and back surface or equivalent power PL and Coddington factor CL; and either central thickness LT or edge thickness and optic diameter) was set up. Calculations were performed based on linear Gaussian optics (vergence formulae). Formulae were provided to derive the lens power/shape and the residual equivalent spectacle refraction SEQ. From the lens shape the location of the haptic plane HP, the image sided principal plane of the lens HL, and the ocular magnification OM were extracted., Results: The calculation of a thick intraocular lens and the prediction of residual refraction is presented with reference to 3 working examples: A) lens varied in PL and shifted with its haptic plane keeping the CL constant, B) lens varied in CL and shifted with its haptic plane keeping PL constant, and C) CL and PL of the lens varied keeping its haptic plane position in the eye constant. For each combination of parameters (PL, CL, or haptic plane shift) the parameters influencing SEQ, OM and HL-HP were analysed., Conclusion: Some modern optical biometers currently on the market provide the radii of curvature of both corneal surface and all relevant distances in the eye. With additional data on the lens shape, it would be possible to improve lens power calculations by switching from thin to thick lens models for the cornea and for the lens. This would overcome one of the major drawbacks of current lens power calculation methods., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier GmbH.)
- Published
- 2022
- Full Text
- View/download PDF
25. Prediction model for best focus, power, and spherical aberration of the cornea: Raytracing on a large dataset of OCT data
- Author
-
Rupert Menapace, Johannes Weisensee, Jascha Wendelstein, Nóra Szentmáry, Achim Langenbucher, Peter Hoffmann, and Alan Cayless
- Subjects
law.invention ,Root mean square ,Cornea ,law ,Medicine and Health Sciences ,Mathematics ,Multidisciplinary ,Eye Lens ,Physics ,Paraxial approximation ,Ophthalmic Procedures ,Cataract Surgery ,Prognosis ,Optical Lenses ,Spherical aberration ,medicine.anatomical_structure ,Optical Equipment ,Physical Sciences ,Focal Planes ,Engineering and Technology ,Medicine ,Anatomy ,Gaussian optics ,Research Article ,Optimization ,Aperture ,Ocular Anatomy ,Science ,Geometry ,Equipment ,Surgical and Invasive Medical Procedures ,Cataract Extraction ,Refraction, Ocular ,Models, Biological ,Cataract ,Optics ,Ocular System ,medicine ,Humans ,Retrospective Studies ,Keratometer ,business.industry ,Biology and Life Sciences ,Radii ,Eyes ,business ,Focus (optics) ,Head - Abstract
Purpose To analyse corneal power based on a large optical coherence tomography dataset using raytracing, and to evaluate corneal power with respect to the corneal front apex plane for different definitions of best focus. Methods A large OCT dataset (10,218 eyes of 8,430 patients) from the Casia 2 (Tomey, Japan) was post-processed in MATLAB (MathWorks, USA). Using radius of curvature, corneal front and back surface asphericity, central corneal thickness, and pupil size (aperture) a bundle of rays was traced through the cornea. Various best focus definitions were tested: a) minimum wavefront error, b) root mean squared ray scatter, c) mean absolute ray scatter, and d) total spot diameter. All 4 target optimisation criteria were tested with each best focus plane. With the best-fit keratometer index the difference of corneal power and keratometric power was evaluated using a multivariate linear model. Results The mean corneal powers for a/b/c/d were 43.02±1.61/42.92±1.58/42.91±1.58/42.94±1.59 dpt respectively. The root mean squared deviations of corneal power from keratometric power (nK = 1.3317/1.3309/1.3308/1.3311 for a/b/c/d) were 0.308/0.185/0.171/0.209 dpt. With the multivariate linear model the respective RMS error was reduced to 0.110/0.052/0.043/0.065 dpt (R² = 0.872/0.921/0.935/0.904). Conclusions Raytracing improves on linear Gaussian optics by considering the asphericity of both refracting surfaces and using Snell’s law of refraction in preference to paraxial simplifications. However, there is no unique definition of best focus, and therefore the calculated corneal power varies depending on the definition of best focus. The multivariate linear model enabled more precise estimation of corneal power compared to the simple keratometer equation.
- Published
- 2021
26. Hopkins procedure for tunable magnification: surgical spectacles
- Author
-
Cristina M. Gómez-Sarabia and Jorge Ojeda-Castaneda
- Subjects
Optics and Photonics ,Computer science ,Normal Distribution ,Magnification ,01 natural sciences ,Models, Biological ,law.invention ,Compensation (engineering) ,010309 optics ,Optics ,law ,0103 physical sciences ,Humans ,Computer Simulation ,Electrical and Electronic Engineering ,Zoom ,Engineering (miscellaneous) ,business.industry ,Equipment Design ,Models, Theoretical ,Image Enhancement ,Atomic and Molecular Physics, and Optics ,Lens (optics) ,Eyeglasses ,Virtual image ,business ,Refractive index ,Gaussian optics - Abstract
We analyze the use of two varifocal lenses, with fixed interlens separation, for achieving tunable magnification at a specific throw. Our discussion extends the Hopkins procedure circumscribed to the determination of fixed optical powers in a multilens system. We illustrate our results by presenting the Gaussian optics design of surgical spectacles, which have tunable magnification while generating virtual images with zero throw. We also report novel formulas describing this type of two-lens zoom system, which works without any mechanical compensation.
- Published
- 2020
27. Incoherent detection sensor design approach using Gaussian optics
- Author
-
Jason Mudge
- Subjects
Computer science ,business.industry ,Ranging ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Photon counting ,law.invention ,010309 optics ,Optics ,law ,Robustness (computer science) ,0103 physical sciences ,Electronic engineering ,Electrical and Electronic Engineering ,Radar ,business ,Engineering (miscellaneous) ,Gaussian optics - Abstract
An incoherent optical detection sensor (often referred to as energy or direct detection sensor) used for remote detection and ranging purposes is a useful tool. While the accuracy and robustness of an incoherent sensor relative to a coherent sensor may be lacking particularly in cluttered environments, it has a place in the world due to its simplicity and performance. With this, a best design approach is sought to meet requirements in a stochastic fashion. In developing the design approach, motivations are borrowed from decades of research in radar systems. This article provides a sensor- or top-level design approach for an incoherent optical detection sensor based mainly on paths developed in radar.
- Published
- 2020
28. Find preliminary solution of zoom objective lens using gaussian optics and third-order aberration theory
- Author
-
史光辉 Shi Guang-hui
- Subjects
Physics ,Lens (optics) ,Third order ,Optics ,law ,business.industry ,Zoom ,business ,Atomic and Molecular Physics, and Optics ,Gaussian optics ,law.invention - Published
- 2018
29. Vision though afocal instruments: generalized magnification and eye-instrument interaction
- Author
-
William F. Harris and Tanya Evans
- Subjects
Physics ,Afocal photography ,business.industry ,05 social sciences ,Magnification ,050105 experimental psychology ,Atomic and Molecular Physics, and Optics ,law.invention ,Telescope ,03 medical and health sciences ,0302 clinical medicine ,Optics ,law ,030221 ophthalmology & optometry ,0501 psychology and cognitive sciences ,business ,Gaussian optics - Abstract
In Gaussian optics all observers experience the same magnification, the instrument’s angular magnification, when viewing distant objects though a telescope or other afocal instruments. However, ana...
- Published
- 2017
30. A Planar Lens Antenna With Circular Edge Inspired by Gaussian Optics.
- Author
-
Mirkamali, Ali, Laurin, Jean-Jacques, Siaka, Francis, and Deban, Ramin
- Subjects
- *
LENSES , *GAUSSIAN beams , *DIELECTRICS , *OPTICAL reflectors , *RAY tracing , *FINITE element method , *SIMULATION methods & models , *PARALLEL-plate waveguides - Abstract
A novel two-dimensional fan-beam lens is presented. The principle of operation of the lens is based on Gaussian optics. The focal point of the circular interface between the dielectric and air is coincident with a focal point of a hyperbolic reflector, while the feeding source is located in the other focal point. The ray tracing method along with physical optics and full wave finite element method (Ansys HFSS) are used to simulate the structure and study the effect of the feed blockage. The two-dimensional lens is implemented in a parallel-plates waveguide and a technique for matching the feeding structure is proposed. Measurement results are presented and confirm the predicted performance. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
31. Optics Design and Verification for the APEX Swedish Heterodyne Facility Instrument (SHeFI).
- Author
-
Nyström, Olle, Lapkin, Igor, Desmaris, Vincent, Dochev, Dimitar, Ferm, Sven-Erik, Fredrixon, Mathias, Henke, Douglas, Meledin, Denis, Monje, Raquel, Strandberg, Magnus, Sundin, Erik, Vassilev, Vessen, and Belitsky, Victor
- Subjects
- *
OPTICS , *TELESCOPE design & construction , *IMAGING systems , *ANTENNAS (Electronics) , *ATMOSPHERIC transparency - Abstract
In this paper, we present the design and verification of the optics of the Swedish Heterodyne Facility Instrument (SHeFI) receiver installed in the Atacama Pathfinder EXperiment (APEX) telescope during spring 2008. SHeFI is located in the Nasmyth instrumentation Cabin A (NCA). The receiver has been designed to have 6 frequency channels, of which four receiver channels have been built, and characterized: 211-275 GHz (Band 1), 275-370 GHz (Band 2), 385-500 GHz (Band 3), and 1250-1390 GHz (Band T2). Bands 1, 2, and T2 are installed at the telescope and are currently in operation. The optical design is driven by the requirement of frequency independent illumination of the secondary with -12 dB edge taper for each frequency channel and the limitation (beam clearance through the Nasmyth tube and the elevation encoder) imposed by the receiver position in the NCA. This paper describes the design approach, optimization, and verification of the optical system, coupling each individual receiving beam to the common optics of the telescope. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
32. Optimization of an Offset Receiver Optics for Radio Telescopes
- Author
-
Yeap, Kim Ho and Tham, Choy Yoong
- Published
- 2017
- Full Text
- View/download PDF
33. A simple method to design astigmatic off-axis mirrors
- Author
-
Wagner-Gentner, A., Graf, U.U., Philipp, M., and Rabanus, D.
- Subjects
- *
GAUSSIAN beams , *DISTRIBUTION (Probability theory) , *GAUSSIAN processes , *OPTICS - Abstract
Abstract: In Gaussian Optics, beams with a circular cross section can easily be matched by using off-axis mirrors. Since the E-field distribution of a Gaussian beam mode is entirely independent in the two directions perpendicular to its axis of propagation, it is also possible to employ the formalism for asymmetric beams. Conventional off-axis mirrors, however, are not suitable to properly match these elliptical beams. In this case, astigmatic optics are required. This paper presents a method of designing astigmatic off-axis mirrors for Gaussian beam modes starting from a conventional off-axis mirror. A numerical simulation and an application for KOSMA’s 1.9THz local oscillator for the GREAT instrument on SOFIA gives evidence supporting the theory. [Copyright &y& Elsevier]
- Published
- 2007
- Full Text
- View/download PDF
34. Optimization of an Offset Receiver Optics for Radio Telescopes
- Author
-
Choy Yoong Tham and Kim Ho Yeap
- Subjects
Radiation ,Cassegrain antenna ,business.industry ,Computer science ,Cassegrain reflector ,020206 networking & telecommunications ,Active optics ,02 engineering and technology ,Feed horn ,Condensed Matter Physics ,Physical optics ,01 natural sciences ,Antenna efficiency ,Optics ,Optical path ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,business ,010303 astronomy & astrophysics ,Instrumentation ,Gaussian optics - Abstract
The latest generation of Cassegrain radio astronomy antennas is designed for multiple frequency bands with receivers for individual bands offset from the antenna axis. The offset feed arrangement typically has two focusing elements in the form of ellipsoidal mirrors in the optical path between the feed horn and the antenna focus. This arrangement aligns the beam from the offset feed horn to illuminate the subreflector. The additional focusing elements increase the number of design variables, namely the distances between the horn aperture and the first mirror and that between the two mirrors, and their focal lengths. There are a huge number of possible combinations of these four variables in which the optics system can take on. The design aim is to seek the combination that will give the optimum antenna efficiency, not only at the centre frequency of the particular band but also across its bandwidth. To pick the optimum combination of the variables, it requires working through, by computational mean, a continuum range of variable values at different frequencies which will fit the optics system within the allocated physical space. Physical optics (PO) is a common technique used in optics design. However, due to the repeated iteration of the huge number of computation involved, the use of PO is not feasible. We present a procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance. The best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper. The optimization procedure uses the beam’s edge taper at the subreflector as the iteration target. The band 6 receiver optics design for the Atacama Large Millimetre Array (ALMA) antenna is used to illustrate the optimization procedure.
- Published
- 2017
35. Cardinal and anti‐cardinal points, equalities and chromatic dependence
- Author
-
Tanya Evans and William F. Harris
- Subjects
Light ,Contact Lenses ,Gaussian ,Mathematics::General Topology ,Refraction, Ocular ,01 natural sciences ,Reduced eye ,010309 optics ,03 medical and health sciences ,symbols.namesake ,0302 clinical medicine ,0103 physical sciences ,Humans ,Chromatic scale ,Mathematics ,computer.programming_language ,Discrete mathematics ,Pascal (programming language) ,Models, Theoretical ,Refractive Errors ,Sensory Systems ,Refractometry ,Mathematics::Logic ,Ophthalmology ,Eyeglasses ,Cardinal point ,030221 ophthalmology & optometry ,symbols ,Ray tracing (graphics) ,computer ,Optometry ,Cardinal direction ,Gaussian optics - Abstract
PURPOSE Cardinal points are used for ray tracing through Gaussian systems. Anti-principal and anti-nodal points (which we shall refer to as the anti-cardinal points), along with the six familiar cardinal points, belong to a much larger set of special points. The purpose of this paper is to obtain a set of relationships and resulting equalities among the cardinal and anti-cardinal points and to illustrate them using Pascal's ring. METHODS The methodology used relies on Gaussian optics and the transference T. We make use of two equations, obtained via the transference, which give the locations of the six cardinal and four anti-cardinal points with respect to the system. We obtain equalities among the cardinal and anti-cardinal points. We utilise Pascal's ring to illustrate which points depend on frequency and their displacement with change in frequency. RESULTS Pascal described a memory schema in the shape of a hexagon for remembering equalities among the points and illustrating shifts in these points when an aspect of the system changes. We modify and extend Pascal's ring to include the anti-cardinal points. We make use of Pascal's ring extended to illustrate which points are dependent on the frequency of light and the direction of shift of the equalities with change in frequency. For the reduced eye the principal and nodal points are independent of frequency, but the focal points and the anti-cardinal points depend on frequency. For Le Grand's four-surface model eye all six cardinal and four anti-cardinal points depend on frequency. This has implications for definitions, particularly of chromatic aberrations of the eye, that make use of cardinal points and that themselves depend on frequency. CONCLUSIONS Pascal's ring and Pascal's ring extended are novel memory schema for remembering the equalities among the cardinal and anti-cardinal points. The rings are useful for illustrating changes among the equalities and direction of shift of points when an aspect of a system changes. Care should be taken when defining concepts that rely on cardinal points that depend on frequency.
- Published
- 2017
36. Quantitative analysis of eyes and other optical systems in linear optics
- Author
-
William F. Harris, Radboud D. van Gool, and Tanya Evans
- Subjects
Optics and Photonics ,02 engineering and technology ,Eye ,Space (mathematics) ,03 medical and health sciences ,Imaging, Three-Dimensional ,0302 clinical medicine ,0202 electrical engineering, electronic engineering, information engineering ,Humans ,Point (geometry) ,Mathematics ,Basis (linear algebra) ,Mathematical analysis ,020206 networking & telecommunications ,Models, Theoretical ,Refractive Errors ,Sensory Systems ,Symplectic matrix ,Ophthalmology ,Eyeglasses ,Character (mathematics) ,030221 ophthalmology & optometry ,Subspace topology ,Optometry ,Vector space ,Gaussian optics - Abstract
PURPOSE To show that 14-dimensional spaces of augmented point P and angle Q characteristics, matrices obtained from the ray transference, are suitable for quantitative analysis although only the latter define an inner-product space and only on it can one define distances and angles. The paper examines the nature of the spaces and their relationships to other spaces including symmetric dioptric power space. METHODS The paper makes use of linear optics, a three-dimensional generalization of Gaussian optics. Symmetric 2 × 2 dioptric power matrices F define a three-dimensional inner-product space which provides a sound basis for quantitative analysis (calculation of changes, arithmetic means, etc.) of refractive errors and thin systems. For general systems the optical character is defined by the dimensionally-heterogeneous 4 × 4 symplectic matrix S, the transference, or if explicit allowance is made for heterocentricity, the 5 × 5 augmented symplectic matrix T. Ordinary quantitative analysis cannot be performed on them because matrices of neither of these types constitute vector spaces. Suitable transformations have been proposed but because the transforms are dimensionally heterogeneous the spaces are not naturally inner-product spaces. RESULTS The paper obtains 14-dimensional spaces of augmented point P and angle Q characteristics. The 14-dimensional space defined by the augmented angle characteristics Q is dimensionally homogenous and an inner-product space. A 10-dimensional subspace of the space of augmented point characteristics P is also an inner-product space. CONCLUSIONS The spaces are suitable for quantitative analysis of the optical character of eyes and many other systems. Distances and angles can be defined in the inner-product spaces. The optical systems may have multiple separated astigmatic and decentred refracting elements.
- Published
- 2017
37. Ultrafast time-resolved spectroscopy of a fs-laser-induced plasma inside glass using a super-continuum probe beam
- Author
-
Denise M. Krol, Jonathan J. Witcher, and Javier Hernandez-Rueda
- Subjects
010302 applied physics ,Materials science ,business.industry ,Physics::Optics ,02 engineering and technology ,General Chemistry ,Plasma ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,law.invention ,Optics ,law ,0103 physical sciences ,Chromatic aberration ,Femtosecond ,General Materials Science ,Time-resolved spectroscopy ,Photonics ,0210 nano-technology ,business ,Ultrashort pulse ,Gaussian optics - Abstract
The light–energy coupling during femtosecond laser processing of glass is mediated by non-linear ionization mechanisms through the formation of an electron plasma. Its transient optical properties provide information about the density, temperature and scattering rate of the excited electrons. In turn, these properties strongly condition the features and size of the permanent optical modification near the focal volume that are desirable to fabricate photonic devices, such as optical waveguides inside transparent materials. Here, we report on the spectral response of a fs-laser-induced electron plasma inside fused silica by measuring its transient transmission using a broadband probe. We model the interaction of the probe beam with the plasma by combining Drude–Sommerfeld model with Gaussian optics. In this manner, we take into account both the laser–plasma interaction and the influence of the chromatic aberration inherent to a broadband-based system. We find good agreement between experiments at several processing energies and simulations and provide an estimate of the dielectric function of the excited material.
- Published
- 2019
38. Correlation analysis and multiple regression formulas of refractive errors and ocular components
- Author
-
Jui-Teng Lin, Chao-Kai Chang, and Yong Zhang
- Subjects
Refractive error ,genetic structures ,Physics::Optics ,law.invention ,03 medical and health sciences ,symbols.namesake ,0302 clinical medicine ,lcsh:Ophthalmology ,law ,refractive errors ,Cornea ,Linear regression ,medicine ,business.industry ,Brief Report ,Mathematical analysis ,medicine.disease ,eye diseases ,Pearson product-moment correlation coefficient ,Regression ,Lens (optics) ,Ophthalmology ,medicine.anatomical_structure ,lcsh:RE1-994 ,regression formulas ,correlation ,Vitreous chamber ,030221 ophthalmology & optometry ,symbols ,sense organs ,business ,human eye ocular components ,Gaussian optics - Abstract
The multiple regression formulas and correlation of ocular components with refractive errors are presented by Gaussian optics. The refractive error changing rate for the cornea and lens power, the axial length, anterior chamber depth (ACD) and vitreous chamber depth (VCD) are calculated, including nonlinear terms for more accurate rate functions than the linear theory. Our theory, consistent with the empirical data, shows that the Pearson correlation coefficients for spherical equivalent (SE) and ocular components are highest for SE with axial length, ACD and VCD and weakest for corneal power, lens power and lens thickness. Moreover, our regression formulas show the asymmetric feature of the correlation that the axial length, ACD and VCD are more strongly correlated (with higher negative regression constants) with refractive errors in eyes with hyperopia than in eyes with myopia, particularly for severe hyperopia.
- Published
- 2019
39. High resolution volumetric dual-camera light-field PIV
- Author
-
Tze How New, Julio Soria, Shengxian Shi, Junfei Ding, Di Mei, and School of Mechanical and Aerospace Engineering
- Subjects
Fluid Flow and Transfer Processes ,Physics ,Algebraic Reconstruction Technique ,Aperture ,business.industry ,Computational Mechanics ,General Physics and Astronomy ,Reconstruction algorithm ,Velocity Measurement ,Viewing angle ,Cameras ,01 natural sciences ,010305 fluids & plasmas ,010309 optics ,Optics ,Particle image velocimetry ,Mechanics of Materials ,0103 physical sciences ,Mechanical engineering [Engineering] ,business ,Image resolution ,Light field ,Gaussian optics - Abstract
Light-field particle image velocimetry (LF-PIV) was recently introduced to measure three-dimensional, three-component velocity field with just a single light-field camera. One of the major challenges lies in the small viewing aperture affecting the depth resolution of such a single-camera based LF-PIV approach. In the present study, we show that this limitation may be mitigated by a dual light-field camera framework, one which includes a novel volumetric calibration model derived from Gaussian optics, a particle intensity reconstruction algorithm based on the multiplicative algebraic reconstruction technique and a post-processing technique for the reconstructed particle intensity field. The proposed approach was firstly validated with synthetic light-field particle images as well as experimental light-field images of five tiny glass beads imitating tracer particles. Secondly, parametric studies were conducted to analyze the influence of the viewing angle and seeding particle density on the reconstruction quality and spatial resolution. In particular, synthetic light-field particle images of a direct numerical simulation jet data set were utilized to compare the performance of single- and dual-camera LF-PIV techniques. Finally, experimental volumetric flow field results of a circular vortex-ring were also measured by single- and dual-camera LF-PIV techniques and compared. It is determined here that an additional light-field camera can mitigate the elongation effects of reconstructed particles and improve the measurement resolution in the depth direction. The authors acknowledge the financial support provided by the National Natural Science Foundation of China (Grant no. 11772197) for the present study. The support of Australian Research Council (ARC) through Discovery and LIEF Grant is also greatly acknowledged.
- Published
- 2019
40. Volumetric calibration enhancements for single-camera light-field PIV
- Author
-
Shengxian Shi, Hanmo Zhang, Junfei Ding, You Liu, Tze How New, and School of Mechanical and Aerospace Engineering
- Subjects
Fluid Flow and Transfer Processes ,Physics ,LF-PIV ,business.industry ,Computational Mechanics ,General Physics and Astronomy ,Iterative reconstruction ,01 natural sciences ,Ray ,010305 fluids & plasmas ,010309 optics ,Cardinal point ,Optics ,Particle image velocimetry ,Mechanics of Materials ,0103 physical sciences ,Mechanical engineering [Engineering] ,Calibration ,Image sensor ,business ,MLA ,Light field ,Gaussian optics - Abstract
This work presents a volumetric calibration method for single-camera light-field particle image velocimetry (light-field PIV or LF-PIV). The proposed technique makes use of the unique point-like feature of particle light-field images to accurately determine affected pixels for a spatial voxel over a relative large measurement volume. A calibration model is derived based on Gaussian optics, which relates a spatial point light source with its confusion circle produced on microlens array (MLA), and optical distortions are accounted for by introducing five calibration parameters. By taking lens defects and misalignment between MLA and image sensor into account, the calibration method can calculate weighting coefficient for particle image reconstruction more accurately than the theoretical ray-tracing method, especially for regions further away from focal plane where light ray deflections are significant due to optical distortions. The volumetric calibration method was validated by simulation tests using synthetic light-field images, and has been successfully applied to a classic vortex-ring LF-PIV measurement, where the measurable range in depth direction was successfully extended and the quality of reconstructed volumetric velocity field was greatly improved. MOE (Min. of Education, S’pore) Accepted version
- Published
- 2019
41. Simulation, fabrication and morphological characterization of a PDMS microlens for light collimation on optrodes
- Author
-
Tao Dong, João Freitas, José Higino Correia, João Ribeiro, Sara Pimenta, Zhaochu Yang, and Universidade do Minho
- Subjects
PDMS/PDMS demolding ,Photolithography ,Engenharia e Tecnologia::Engenharia Médica ,Saúde de qualidade ,Materials science ,02 engineering and technology ,SEM tools ,01 natural sciences ,Collimated light ,law.invention ,010309 optics ,chemistry.chemical_compound ,PDMS ,law ,0103 physical sciences ,Surface roughness ,Focal length ,Light collimation ,Electrical and Electronic Engineering ,Microlens ,Gaussian optics ,Science & Technology ,Polydimethylsiloxane ,business.industry ,AFM/SEM tools ,Engenharia Médica [Engenharia e Tecnologia] ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Numerical aperture ,Thermal reflow ,chemistry ,Optoelectronics ,AFM ,0210 nano-technology ,business ,PDMS demolding ,Microfabrication - Abstract
Optrodes are neural probes for delivering light at neurons, at least with an irradiance of 1 mW/mm2. MicroLED (microlight-emitting diode) optrodes with a microlens to collimate the light can improve the irradiance without increasing the microLED power consumption, minimizing the brain overheating. This paper presents FEM (finite element method) simulations of a PDMS (polydimethylsiloxane) microlens capable of collimating the light from a microLED, ensuring an average irradiance of 310 mW/mm2. Based on the simulated microlens, a microlens array was fabricated, using microfabrication processes. One of the PDMS microlens from the fabricated array was experimentally characterized, using AFM (atomic force microscopy) and SEM (scanning electron microscopy). The average surface roughness, base diameter and height of the microlens is 2.3 nm, 80 μm and 55 μm, respectively. It was also possible to determine the microlens focal length (96 μm), numerical aperture (0.42), f-number (1.2) and depth of focus (2.66 μm), using Gaussian optics. The fabrication process was validated, even using PDMS/PDMS demolding without surface treatment of the negative mold., This work is supported by FCT: OpticalBrain, PTDC/CTM-REF/28406/2017 operation code NORTE-01-0145-FEDER- 028406; OCT-RAMAN, PTDC/FIS- OTI/28296/2017 operation code NORTE-01-0145-FEDER-028296; CMEMS-UMinho strategic project UIDB/04436/2020; project of Infrastructures Micro&NanoFabs@PTNORTE- 01-0145-FEDER-022090, PORNorte, Portugal 2020 by FEDER funds through the COMPETE 2020 Programa Operacional Competitividade e Internacionalização (POCI). The work is also supported by RFF Forskningsfond Oslofjordfondet (Project No. 285575 and 296654), National Natural Science Foundation of China (Project No. 61950410621, 61531008 and 11702045). The support from Chongqing Research Program of Basic Research and Frontier Technology (Project No. cstc2016jcyjA0292, cstc2019jcyj-msxmX0776, cstc2017jcyjAX0191, cstc2017jcyjA1842 and cstc2018jcyjA4046), and Chongqing Education Commission – Science and Technology Research Program (Proj. nos. KJZD-K201800802, KJZD-K201900802) are also acknowledged.
- Published
- 2021
42. Depth compensation based fractal analysis of human microvasculature
- Author
-
Shi Weisong, Zhang Lanlan, Wanrong Gao, and Zhang Yue
- Subjects
Physics ,medicine.diagnostic_test ,business.industry ,Attenuation ,02 engineering and technology ,Blood flow ,021001 nanoscience & nanotechnology ,01 natural sciences ,Fractal analysis ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Compensation (engineering) ,010309 optics ,Light intensity ,Fractal ,Optics ,Optical coherence tomography ,0103 physical sciences ,medicine ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Gaussian optics ,Biomedical engineering - Abstract
Quantifying the microcirculation system is helpful for a more accurate diagnosis of blood flow related diseases. In this work, we report a depth-resolved fractal parameter analysis of human microvasculature obtained with a swept-source optical coherence tomography (SS-OCT) system after depth compensation. In our analysis, the characteristics of Gaussian optics and the attenuation of light intensity with the propagation distance into the tissue were taken into account. To obtain accurate depth-resolved fractal parameter of microvasculature in human skin, a swept-source optical coherence tomography (SS-OCT) system was built. First, three-dimension blood flow datasets were acquired. Then the signals from multiple depth layers of human skin were compensated based on our model, and depth-resolved fractal parameters were extracted finally. The en-face images of the microvasculature of different areas were presented. To the best of our knowledge, for the first time, it was found that the characteristic change of the fractal parameters of the microvasculature of in vivo human skin may be missed due to the light attenuation and the features of Gaussian optics. The depth-resolved fractal analysis of human microvasculature after depth-dependent compensation of imaging signals allows more accurate blood flow related diagnose diseases or monitoring renormalization of the microvasculature after treatment.
- Published
- 2020
43. Appendix Introduction to Gaussian Optics
- Author
-
Ronald B. Lockwood, Thomas W. Cooley, and Dimitris G. Manolakis
- Subjects
Physics ,Optics ,business.industry ,business ,Gaussian optics - Published
- 2016
44. On the formal analysis of Gaussian optical systems in HOL
- Author
-
Umair Siddique and Sofiène Tahar
- Subjects
Pure mathematics ,Geometrical optics ,Gaussian ,Optical communication ,HOL ,0102 computer and information sciences ,01 natural sciences ,Theoretical Computer Science ,law.invention ,010309 optics ,Telescope ,symbols.namesake ,Automated theorem proving ,Pathfinder ,010201 computation theory & mathematics ,law ,0103 physical sciences ,Electronic engineering ,symbols ,Software ,Mathematics ,Gaussian optics - Abstract
Optics technology is being increasingly used in mainstream industrial and research domains such as terrestrial telescopes, biomedical imaging and optical communication. One of the most widely used modeling approaches for such systems is Gaussian optics, which describes light as a beam. In this paper, we propose to use higher-order-logic theorem proving for the analysis of Gaussian optical systems. In particular, we present the formalization of Gaussian beams and verify the corresponding properties such as beam transformation, beam waist radius and location. Consequently, we build formal reasoning support for the analysis of quasi-optical systems. In order to demonstrate the effectiveness of our approach, we present a case study about the receiver module of a real-world Atacama Pathfinder Experiment (APEX) telescope.
- Published
- 2016
45. Passage from scalar to vector optics and the Mukunda-Simon-Sudarshan theory for paraxial systems
- Author
-
Sameen Ahmed Khan
- Subjects
Physics ,Foldy–Wouthuysen transformation ,business.industry ,Paraxial approximation ,Scalar (mathematics) ,Physics::Optics ,Polarization (waves) ,Physical optics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,symbols.namesake ,Optics ,Maxwell's equations ,Dirac electron ,0103 physical sciences ,symbols ,010306 general physics ,business ,Gaussian optics - Abstract
The way to generalize scalar to wave optics, thus including polarization in the treatment consistent with the Maxwell equations was shown by Mukunda, Simon and Sudarshan for paraxial systems, based on a group theoretical analysis. Here, the Mukunda–Simon–Sudarshan (MSS) theory for the passage from scalar to vector optics is derived by casting the basic formalism in a framework very similar to the Dirac electron theory. The resulting formalism is suitable for extending the MSS-theory beyond the paraxial approximation.
- Published
- 2016
46. Gaussian Optics Analysis for Human Eyes with Application for Vision Corrections
- Author
-
Jui-Teng Lin
- Subjects
medicine.anatomical_structure ,business.industry ,Computer science ,Immunology ,medicine ,Human eye ,Computer vision ,Artificial intelligence ,business ,Gaussian optics - Published
- 2016
47. A New Approach for the Calculation of Total Corneal Astigmatism Considering the Magnitude and Orientation of Posterior Corneal Astigmatism and Thickness
- Author
-
Universidad de Alicante. Departamento de Óptica, Farmacología y Anatomía, Piñero, David P., Caballero, María T., Nicolás Albujer, Juan Miguel, Fez Saiz, Dolores de, Camps, Vicente J., Universidad de Alicante. Departamento de Óptica, Farmacología y Anatomía, Piñero, David P., Caballero, María T., Nicolás Albujer, Juan Miguel, Fez Saiz, Dolores de, and Camps, Vicente J.
- Abstract
Purpose: To evaluate a new method of calculation of total corneal astigmatism based on Gaussian optics and the power design of a spherocylindrical lens (C) in the healthy eye and to compare it with keratometric (K) and power vector (PV) methods. Methods: A total of 92 healthy eyes of 92 patients (age, 17–65 years) were enrolled. Corneal astigmatism was calculated in all cases using K, PV, and our new approach C that considers the contribution of corneal thickness. An evaluation of the interchangeability of our new approach with the other 2 methods was performed using Bland–Altman analysis. Results: Statistically significant differences between methods were found in the magnitude of astigmatism (P < 0.001), with the highest values provided by K. These differences in the magnitude of astigmatism were clinically relevant when K and C were compared [limits of agreement (LoA), −0.40 to 0.62 D), but not for the comparison between PV and C (LoA, −0.03 to 0.01 D). Differences in the axis of astigmatism between methods did not reach statistical significance (P = 0.408). However, they were clinically relevant when comparing K and C (LoA, −5.48 to 15.68 degrees) but not for the comparison between PV and C (LoA, −1.68 to 1.42 degrees). Conclusions: The use of our new approach for the calculation of total corneal astigmatism provides astigmatic results comparable to the PV method, which suggests that the effect of pachymetry on total corneal astigmatism is minimal in healthy eyes.
- Published
- 2018
48. Paraxial properties of two-element zoom systems for Gaussian beam transformation
- Author
-
Pavel Novák and Antonin Miks
- Subjects
Physics ,Zoom lens ,Geometrical optics ,business.industry ,Gaussian ,Paraxial approximation ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Physics::Optics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Computer Science::Robotics ,symbols.namesake ,Transformation (function) ,Optics ,symbols ,Physics::Accelerator Physics ,Electrical and Electronic Engineering ,Zoom ,business ,Gaussian optics ,Gaussian beam - Abstract
This work deals with a problem of paraxial analysis of optical systems for transformation of Gaussian beams. General equations describing the paraxial parameters of a two-element zoom system for transformation of a Gaussian beam are derived. It is shown that such a zoom lens has different kinematics with respect to classical zoom system designed for homocentric beams, which depends on the parameters of the transformed Gaussian beam.
- Published
- 2015
49. Launching of the new world of geometrical optics
- Author
-
Pramode Ranjan Bhattacharjee
- Subjects
Physics ,Geometrical optics ,business.industry ,Physics::Optics ,Refraction ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Optical phenomena ,Optics ,Classical mechanics ,Electrical and Electronic Engineering ,business ,Reflection (computer graphics) ,Gaussian optics - Abstract
This paper reports on the discovery of the most unambiguous generalized vectorial laws of reflection and refraction along with the launching of a new world of geometrical optics with a lot of novel interesting physical insights to optical phenomena.
- Published
- 2015
50. Prediction of Electromagnetic Wave Propagation in Space Environments Based on Geometrical Optics
- Author
-
Yong Bae Park and Changseong Kim
- Subjects
Physics ,Geometrical optics ,business.industry ,Wave propagation ,020208 electrical & electronic engineering ,020206 networking & telecommunications ,02 engineering and technology ,Space (mathematics) ,Physical optics ,Optics ,Classical mechanics ,0202 electrical engineering, electronic engineering, information engineering ,business ,Space environment ,Gaussian optics - Published
- 2017
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.