Aspheric Lens Design Research Articles

Aspherical lens design using hybrid neural-genetic algorithm of contact lenses.

The design of complex contact lenses involves numerous uncertain variables. How to help an optical designer to first design the optimal contact lens to reduce discomfort when wearing a pair of glasses is an essential design concern. This study examined the impact of aberrations on contact lenses to optimize a contact lens design for myopic and astigmatic eyes. In general, two aspherical surfaces can be assembled in an optical system to reduce the overall volume size. However, this design reduces the spherical aberration (SA) values at wide contact radii. The proposed optimization algorithm with optical design can be corrected to improve the SA value and, thus, reduce coma aberration (TCO) values and enhance the modulation transfer function (MTF). This means integrating a modified genetic algorithm (GA) with a neural network (NN) to optimize multiple-quality characteristics, namely the SA, TCO, and MTF, of contact lenses. When the proposed optional weight NN-GA is implemented, the weight values of the fitness function can be varied to adjust system performance. The method simplifies the selection of parameters in the optimization of optical systems. Compared with the traditional CODE V built-in optimal scheme, the proposed scheme is more flexible and intuitive to improve SA, TCO, and MTF values by 50.03%, 45.78%, and 24.7%, respectively.

非球面鱼眼镜头设计及畸变校正算法研究

非球面鱼眼镜头设计及畸变校正算法研究

Aspherical lens design

Given a three-dimensional surface G, not necessarily rotationally symmetric, and away from a point source, we design a surface F such that the lens sandwiched between the two surfaces refracts radiation into a given direction or into a given point. The surface F satisfies a system of first-order partial differential equations that can be solved in terms of G and the refractive indices of the media involved.

Effect of a single-piece aspheric hydrophobic acrylic intraocular lens design on centration and rotation

To assess the rotation and centration stability of the new design features of a 1-piece aspheric hydrophobic acrylic intraocular lens (IOL). National Eye Hospital, Cairo, Egypt. Randomized clinical trial. Patients in this study had implantation of a 1-piece Tecnis 1 ZCB00 IOL or a 3-piece Sensar AR40e IOL. Decentration and rotation were recorded immediately postoperatively, and 2 to 3 days and 8 weeks postoperatively. This was done using 2 slitlamp eyepieces and referring to constant corneal landmarks (ie, the limbus and the phaco incision). Thirty-two 1-piece IOLs and 30 3-piece IOLs were implanted. Although the 1-piece IOLs moved toward the corneal center more than the 3-piece IOLs between 3 days and 8 weeks postoperatively (P=.054), the difference was not statistically significant between 0 day and 3 days or during the entire follow-up (P=.546 and P=.367, respectively). There were no statistically significant differences in the horizontal or vertical components of this movement between the 2 groups (P=.883 and P=.636, respectively). The mean rotation was 2.5 degrees ± 9.1 (SD) in the 1-piece IOL group and 0 ± 6.5 degrees in the 3-piece IOL group, with no statistically significant difference between the groups (P=.521). The new 1-piece design showed relatively good centration and stability in the horizontal, vertical, and rotational aspects.

Aberration correction of a single aspheric lens with particle swarm algorithm

In order to design a single aspheric lens to meet the requirements of spherical aberration, the particle swarm algorithm is applied to the aberration correction for a single aspheric lens. A mathematical model is constructed, and a program code is developed. Merit functions in an optical system are employed as fitness functions, which combined coefficients of a higher order polynomial equation, a reciprocal of radius of curvature, the conic constant, thicknesses among lens surfaces and refractive indices regarding an optical system. By using this function, the automatic correction of spherical aberration is carried out. The example for a single aspheric lens design using particle swarm algorithm shows that PSO as a tool of the spherical aberration correction for a single aspheric lens is simple and effective, and easy to find a series of good design results. The asphere's more complex surface profile can reduce or eliminate easily spherical aberration at different incidence heights at one time. The automatic design and analysis of a single aspheric lens using this method from the view of a particular optical design problem are presented.

Designing contact lenses for a wide field of view via ocular wavefront tomography

Purpose Correcting the off-axis wavefront aberration is potentially important for peripheral vision, for diagnostic imaging of the retina, and for influencing refractive development. A new technique called ocular wavefront tomography (OWT) was adapted to optimize the design of contact lenses to improve the eye's peripheral optical quality. Methods OWT is a technique for customizing a multi-surface model eye to mimic the off-axis wavefront aberrations for an individual eye. This technique was adapted for contact lens design by establishing clear design goals for the eye + contact lens system. To demonstrate the method we optimized the shape of an aspheric and bifocal contact lens to correct a wide angle model eye with −2D foveal myopia. Two strategies for correction reflected alternative design goals: 1) to fully correct central vision while also improving optical quality peripherally to enhance vision and retinal imaging, or 2) fully correct central vision while introducing a degree of peripheral myopia relative to central vision in order to slow myopia progression. Results The OWT technique successfully produced aspheric and bifocal contact lens designs over a wide field of view. In addition to correcting foveal vision, the optimized contact lens designs either 1) improved the retinal image quality across the visual field (< 45°) significantly to obtain a visual performance and retinal imaging benefit or 2) produced the desired level of myopia in the peripheral field to obtain a refractive development benefit. Conclusion The OWT technique is a validated tool to optimize contact lens design over a wide field.

Third-order design of aspheric spectacle lenses

The theory of third-order aberrations for a system of rotationally symmetric aspheric thin lenses and relations for calculation of the shape of rotationally symmetric aspheric spectacle lenses with zero astigmatism are described. A comparison of aspheric and spherical spectacle lens design is presented. Possible applications of aspheric lens surfaces are proposed including the design of a spectacle lens with two types of primary aberrations corrected, an anastigmatic spectacle lens with minimum weight and a spectacle lens with the desired aesthetic shape. Our work performs a complex analysis of the third-order design of spectacle lenses considering not only astigmatism but all types of primary aberrations and their combinations.

A Study on the Aspheric Lens Design and Manufacturing for Flow Visualization

A Study on the Aspheric Lens Design and Manufacturing for Flow Visualization

Aspherical refractive lenses for small-angle neutron scattering

Aspherical neutron lenses are discussed in detail as focusing elements for existing small-angle neutron scattering (SANS) diffractometers. The conceptual design can be obtained by analytical equations, while computer simulations provide the intensity distribution of the primary beam, which is strongly correlated with the instrumental resolution and the minimal momentum transferQ. For large illuminated sample/lens areas of 50 mm diameter the aspherical lens design is essential, while spherical lenses are limited toca20 mm diameter with a 60% spherical aberration for standard SANS experiments. Scattering experiments on different samples proved the applicability and revealed the resolution limits of the two lens types. From theoretical considerations it is proposed that lens cooling can be used to reduce the thermal diffuse scattering.

Effect of decentration and tilt on the image quality of aspheric intraocular lens designs in a model eye

To determine the impact of decentration and tilt on the imaging quality of aspheric intraocular lens (IOL) designs in a schematic model eye. Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany. A model eye was used to calculate the impact of misalignment on the imaging quality of 6 IOL designs. The crystalline lens in the model eye was replaced with IOL designs with 22.0 diopters nominal refractive power, and the anterior chamber depth (ACD) was set to the estimated ACD value provided by the manufacturer. The retinal position was optimized for the best image quality. The IOLs were decentered up to +/-1.0 mm and tilted up to +/-5 degrees relative to the line of sight. At each position, the modulation transfer function was recorded with 3.0 mm and 4.5 mm pupil diameters. The results between the IOL designs and those of the phakic model eye were then compared. Aberration-correcting IOLs were very sensitive to decentration and tilt. However, the impact of misalignment depended on IOL design. Aberration-free IOLs showed less sensitivity within a wide range of displacement but provided better results than the spherical IOL. Overall, modern aspheric IOLs provided better imaging quality than conventional spherical IOL designs. Aberration-free IOLs were less sensitive to decentration and tilt than aberration-correcting IOLs but provided better image quality than spherical IOLs. Aberration-correcting IOLs have the potential to provide diffraction-limited imaging quality when perfectly aligned.

Reshaping of a Divergent Elliptical Gaussian Laser Beam Into a Circular, Collimated, and Uniform Beam With Aspherical Lens Design

In this paper, we present a specific optical system of two aspherical lenses designed to circularize, collimate, and expand an edge-emitting semiconductor laser beam and transform its irradiance distribution from Gaussian to a uniform-square distribution for possible application in light detection and ranging sensors. It is verified that the diffraction effects are negligible so that geometrical ray optics is used to design this optical system. To accomplish the design, the source beam profile is decoupled into two independent beam profiles represented in two transverse directions. Analytical equations specific to this lens system are derived and MATLAB is used to solve these equations and simulate a design example. Results are presented for a specific example.

Optimizing distance image quality of an aspheric multifocal intraocular lens using a comprehensive statistical design approach

The AcrySof ReSTOR intraocular lens (IOL) is a multifocal lens with state-of-the-art apodized diffractive technology, and is indicated for visual correction of aphakia secondary to removal of cataractous lenses in adult patients with/without presbyopia, who desire near, intermediate, and distance vision with increased spectacle independence. The multifocal design results in some optical contrast reduction, which may be improved by reducing spherical aberration. A novel patent-pending approach was undertaken to investigate the optical performance of aspheric lens designs. Simulated eyes using human normal distributions were corrected with different lens designs in a Monte Carlo simulation that allowed for variability in multiple surgical parameters (e.g. positioning error, biometric variation). Monte Carlo optimized results indicated that a lens spherical aberration of -0.10 microm provided optimal distance image quality.

Optical and Visual Performance of Aspheric Soft Contact Lenses

This study was conducted to investigate whether aspheric design soft contact lenses reduce ocular aberrations and result in better visual acuity and subjective appreciation of clinical performance compared with spherical soft contact lenses. A unilateral, double-masked, randomized and controlled study was undertaken in which ocular aberrations and high and low contrast logMAR visual acuity were measured on myopic subjects who wore aspheric design (Biomedics 55 Evolution, CooperVision) and spherical design (Biomedics 55, CooperVision) soft contact lenses. Ten subjects who had about -2.00 D myopia wore -2.00 D lenses and 10 subjects who had about -5.00 D myopia wore -5.00 D lenses. Measurements were made under photopic and mesopic lighting conditions. Subjects were invited to grade comfort, vision in photopic and mesopic conditions, and overall impression with the two lens types on 100 unit visual analogue scales. There was no significant difference in high contrast or low contrast visual acuity between the two lens designs of either power under photopic or mesopic conditions. Both lens designs displayed lower levels of spherical aberration compared with the "no lens" condition under photopic and mesopic light levels (p < 0.0001); however, there were no differences in aberrations between aspheric and spherical lens designs. There were no statistically significant differences in subjective appreciation of clinical performance between lens designs or lens powers. At least with respect to the brand of lenses tested, the fitting of aspheric design soft contact lenses does not result in superior visual acuity, aberration control, or subjective appreciation compared with equivalent spherical design soft contact lenses.

Aspherical Lens Design by Using a Numerical Analysis

The surface profiles of four different spherical-aberration-free aspherical lenses are given as conic curves, namely a hyperbola and an ellipse. Historically known as Cartesian ovals, these lens profiles can be obtained from Fermat's principle. Alternatively, we have derived the surface profile from...

Optimising RGP lens fitting in normal eyes using 3D topographic data

Purpose: To analyse, retrospectively, the effect of fitting characteristics on comfort of wear and the role that 3D topographic data can play in attaining an optimal lens fit with rigid gas permeable (RGP) contact lenses in normal eyes. Methods: Included were 60 normal myopic eyes (1.00–5.00 D) with astigmatism limited to 2.00 D. Lenses were ordered empirically, based on traditional fitting rules. Results: The initial fit based on traditional computation was accepted in 40% of the eyes. To achieve an acceptable fit, 15% of the eyes needed an adaptation of the back optic zone radius, in 28% switching from a multicurve to an aspheric lens design was indicated and in 17% a non-rotational symmetric lens design was favoured. The reason for changing the lens parameters could in 88% be attributed to mid-peripheral differences between corneal shape as found with 3D corneal topography. Average comfort of wear improved statistically significantly ( χ 2, P<0.05) from 5.2 initially to 7.7 after 3 months in the group with optimal lens fits, while comfort slightly decreased (not significant) in the group with sub-optimal fits. Switching to a non-rotational symmetric lens design, when indicated, improved comfort significantly ( χ 2, P<0.05) from 5.0 to 7.3. Conclusion: In normal eyes, the measurement of corneal shape, especially in the mid-peripheral regions, is of importance to optimise RGP lens fit. Optimised lens fits increases comfort of wear.

Design of a plastic aspheric Fresnel lens with a spherical shape

A detailed description of the design of a plastic, aspheric Fresnel lens on a spherical surface is provided. The design technique is based on calculating solutions to Snell's law along the lens surface. These lenses were intended for the wavelength range of 8 to 12 mm. However, the method easily applies to lenses designed for other wave- lengths. The procedure used to manufacture the lenses is to construct a diamond-turned master surface, followed by injection molding with high- density polyethylene. © 1997 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(97)00404-2)

Low-cost fabrication of optical subassemblies

The optical subassembly is a major contributor to the cost of a fiberoptic computer data link. A technology for low-cost fabrication of optical subassemblies is described, with emphasis on a transmitter subassembly designed for fiber-channel standard operation (266 Mb/s for 2 km; 1063 Mb/s for 500 m). A factor of three cost reduction is achieved by limiting the parts count to only three: a laser or receiver chip packaged in a TO-can, a plastic housing, and a plastic aspheric lens; and by employment of a fast, automated active-alignment and subsequent fixing technique. Key enabling features include the use of precision injection molding of specially chosen plastics, an aspheric lens design which permits wide positional variations in the axial direction, and curing of a fast setting epoxy through the use of RF power. A tool was constructed which produced subassemblies at high yield having satisfactory performance.

Subjective and Objective Assessment of Soft Bifocal Contact Lens Performance

Subjective and objective techniques were used to assess the on-eye performance of soft bifocal contact lenses. In the subjective technique a young observer whose accommodation had been paralyzed with a cycloplegic agent was fitted with the contact lens type under investigation and aligned with a Maxwellian view Badal optometer using a bite-bar. Visual acuity was measured as a function of both target vergence (0.00 to -4.00 D) and pupil size (1 to 5 mm). Aspheric, concentric, and diffractive soft bifocal contact lens designs were investigated. Diffractive and concentric bifocal designs with +2.00 D near additions showed "twin peaks" of visual acuity with one peak at 0.00 D target vergence (equivalent to distance viewing) and the second at -2.00 D target vergence (equivalent to a target at 50 cm). Some aspheric designs produced a relatively constant visual acuity across this vergence range, whereas others gave poor acuity at near. Visual acuity with the Echelon diffractive lens was relatively unaffected by pupil size, confirming theoretical predictions. Visual acuity with concentric designs was also relatively free of pupil size effects. In the objective technique, the variation in surface power across the lens was assessed using video-keratography. This technique provided an elegant means of visualizing the power profile of the lens. The location of the zones of increased power and the magnitude of power variations allowed an accurate prediction of the visual performance measured subjectively. Temporal displacement of lenses may explain the occasions where visual performance did not vary with pupil size.

Performance of aspheric spectacle lenses

With improvements in spectacle lens technology, several aspheric lens designs have become available in the moderate power range for prescribing by ophthalmic practitioners. Their manufacturers claim that these lenses improve cosmetic appearance and are lighter than equivalent spherical lenses, without sacrificing visual performance attributes such as good off-axis visual acuity and low distortion. We have made measurements of aspheric lenses made by Rodenstock, Essilor, Sola and Hoya, and have compared them with spherical lenses which have minimal off-axis power errors (best form design). Our results generally support the claims. Cosmetic appearance is considerably better for aspheric than for spherical lenses. The reduction in weight for plastic aspheric lenses is 8–32 per cent for 60 mm diameter. The percentage reductions would be less for smaller lenses. Except for a few exceptions, off-axis power errors of aspheric lenses are similar to those of similar power spherical lenses. All the aspheric lenses have similar or less rotatory distortion than spherical lenses of similar power. (Clin Exp Optom 1992; 75: 6: 210–217)

Spectacle lens design: a review

This review considers the present state of the design of spectacle lenses with respect to minimizing the side effects that are associated with their wear. Topics include spherical lens design, aspheric lens design, progressive addition lenses, spectacle lens materials, assumptions of conventional lens design, and practical assessment of spectacle lens design. Future possibilities in the manufacture of spectacle lenses are discussed briefly.