Fabrication of optical articles

Abstract

An eyeglass lens blank is fabricated in a system comprising a rotatable mould 120 surrounding a cavity having a diameter of at least 50 mm, an electric motor configured to rotate the mould at less tha

Description

CROSS-REFERENCE TO OTHER PUBLICATION This application claims priority from UK patent application no. GB2401153.8 filed on January 29, 2024, the teachings of which are incorporated herein by reference. FIELD OF THE INVENTION The present invention relates to methods, apparatus and systems for fabricating optical articles, and particularly to optical articles formed from radiation-polymerizable compositions. BACKGROUND Eyeglass lenses are currently produced in a variety of different processes. A common method for producing an eyeglass lens in an optical laboratory involves first selecting a clear lens blank, which is obtainable commercially in a variety of diopters. The lens blanks are outsourced from large producers who produce them using molding and / or machining. Even a small laboratory must track and maintain inventories of a very large number of differently powered lens blanks. When tints and other coatings are involved, the number of different blanks increases even further. The work of the laboratory may involve measuring or scanning a selected eyeglass frame and trimming or edging the lens blank to fit the frame. Some methods include selecting and then machining a semi-finished or finished lens blank with a given base power, i.e., the curvature of a first surface, to produce a lens with the final diopter. At present, there is no known practical approach that gives the optical laboratory more control over the production of the lenses, e.g., production of the lens blanks themselves. A practical approach is needed that would reduce the need to manage large, expensive inventories of diopter-specific lens blanks and that would allow the optical laboratory to control all or a large part of lens production while producing precise lenses in an expedited and less expensive manner. SUMMARY A method is disclosed, according to embodiments, for fabricating an eyeglass lens blank. The method comprises: (a) introducing a radiation-curable composition into a mold surrounding a cavity having a diameter of at least 50 mm, a floor portion of the mold being shaped for forming thereupon a first surface of the optical article; (b) rotating the mold, at a speed of at least 30 rpm or at least 50 rpm, and not more than 120 rpm, about a center of rotation thereof to cause a portion of the radiation-curable composition to displace so as to change a contour of an upper surface of the curable composition to a concave paraboloid shape; and (c) subjecting the curable composition to the curing radiation to solidify the composition. According to embodiments, a system for use in fabricating an eyeglass lens blank from a radiation-polymerizable composition comprises: (a) a rotatable mold surrounding a cavity having a diameter of at least 50 mm, the mold comprising a floor portion arranged for forming thereupon a first surface of the eyeglass lens blank and a peripheral wall portion having a minimum height at least 1 mm above a highest point of the floor portion; (b) an electric motor operative to rotate the mold at a constant speed between 50 and 120 revolutions per minute; and (c) a source of polymerizing radiation arrangeable to irradiate at least a portion of the polymerizable composition with said polymerizing radiation, wherein in a first operating mode of the system, when the mold is rotated at a speed between 50 and 120 revolutions per minute while a radiation-polymerizable composition having a viscosity between 20 and 500 cP at ambient temperature is resident in said cavity, the radiation-polymerizable composition having a volume of between 0.25 and 0.35 cc per cm2 of cavity area, the rotating is effective to change a contour of an upper surface of the polymerizable composition to form a concave paraboloid shape. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described further, by way of example, with reference to the accompanying drawings, in which the dimensions of components and features shown in the figures are chosen for convenience and clarity of presentation and not necessarily to scale. In the drawings: Fig. 1 is a schematic perspective view showing a powered, rotatable mold according to embodiments of the invention. Fig. 2 schematically shows a cross-section of the mold of Fig. 1, according to embodiments of the invention. Fig. 3A shows a perspective view of an exemplary optical article according to embodiments of the invention. Fig. 3B shows a schematic section contour of the optical article of Fig. 3A, according to embodiments of the invention. Fig. 4A shows a perspective view of an exemplary floor portion of a mold, according to embodiments of the invention. Fig. 4B shows a schematic section contour of the floor portion of Fig. 4A, according to embodiments of the invention. Figs. 5A, 5B, 5C, 5D and 5E show respective schematic section contours of floor portions of a mold, according to embodiments of the invention. Fig. 6 is a schematic illustration of a removable element governing a peripheral contour of the optical article, according to embodiments of the invention. Fig. 7A is a schematic illustration of a mold with the removable element of Fig. 6 installed therewithin, according to embodiments of the invention. Fig. 7B shows a cross section of a detail of Fig. 7A. Fig. 8 shows a block diagram of some elements of an apparatus for use in fabricating an optical article from a radiation-polymerizable composition, according to embodiments of the invention. Fig. 9 is a schematic illustration of using a source of curing radiation to irradiate an upper surface of a curable composition in a mold, according to embodiments of the invention. Fig. 10 is a schematic illustration of using a source of curing radiation to irradiate at least a lower surface of a curable composition in a mold, according to embodiments of the invention. Figs. 11A and 1 IB are schematic illustrations of masking the curable radiation directed at an upper surface of a curable composition in a mold, according to embodiments of the invention. Fig. 12 is a schematic illustration of using directable radiation to irradiate an upper surface of a curable composition in a mold, according to embodiments of the invention. Fig. 13 is a schematic illustration of a fluid conveyance delivering a curable composition from a storage vessel to a mold, according to embodiments of the invention. Fig. 14 shows a block diagram of some elements of a system for use in fabricating an optical article from a radiation-polymerizable composition, according to embodiments of the invention. Fig. 15 shows a block diagram showing some elements of the control system of the system of Fig. 14, according to embodiments of the invention. Figs. 16A, 16B and 16C show respective examples of a user interface of the system of Fig. 14, according to embodiments of the invention. Fig. 17 is a schematic illustration of a tabletop implementation of a system for use in fabricating an optical article from a radiation-polymerizable composition, according to embodiments of the invention. Figs. 18A, 18B, 18C, 18D, 18E, 18F, 18G, 18H, 181, 18J, 18K, 18L, and 19 show flowcharts of methods and method steps for fabricating an optical article, according to embodiments of the invention. DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Throughout the drawings, like-referenced characters are generally used to designate like elements. Embodiments of the invention relate to fabricating of optical articles in a rotating mold. In some implementations, the optical articles comprise eyeglass lens blanks of any variety, i.e., finished, semi-finished or unfinished, and single-vision or multifocal (or progressive). In various implementations, the optical articles can include lenses, including, without limitation, corrective lenses such as eyeglass lenses, including tinted or photochromatic lenses for eyeglasses and sunglasses. In other implementations, the optical articles can comprise elements of optical instruments, such as, and not exhaustively: telescopes, microscopes, binoculars, laser emitters, optical scopes for weapons, and flashlights. As used herein, the term ‘eyeglass lens blank’ includes any eyeglass lens bank, i.e., finished, semi-finished or unfinished, and single-vision or multifocal (or progressive), unless otherwise specified. As the term is used herein, an eyeglass lens blank differs from an eyeglass lens at least in that the eyeglass lens is formed, cut or trimmed to the shape of an eyeglass lens, including in some implementations from an eyeglass lens blank. In contrast, the eyeglass lens blank is generally not shaped like the final eyeglass lens, but rather is round or any other suitable convex shape, and large enough to trim or cut therefrom an eyeglass lens. Eyeglass lens blanks can be of any necessary diameter e.g., 50 mm, 65 mm, 80 mm, or any other diameter to suit different sizes and contours of eyeglass lenses. In the embodiments, the optical articles are at least partly formed in a cavity of the rotating mold from a radiation-polymerizable composition that can be in a liquid phase, or alternatively semi-liquid or semi-solid. In some embodiments, the composition is radiation-curable but not necessarily polymerizable; nonetheless the terms are used interchangeably in the present disclosure and in the appended claims, and both can be understood to mean radiation-polymerized or otherwise radiation-cured. In an illustrative example, a polymeric dispersion such as an aqueous polyurethane dispersion can be radiation cured but does not undergo further polymerization. Examples of suitable radiation-polymerizable compositions include, without limitation, Crystal Coat® UV CS-950, or Crystal Coat® UV CS-NT5, both available commercially from SDC Technologies, Inc., of Irvine, California, USA; PPG H-GARD® 2000, available commercially from PPG Industries, Inc., of Pittsburgh, Pennsylvania, USA; IOC-135, available commercially from Inkron of Espoo, Finland; and the PixClear family of products, available commercially from Pixelligent Technologies LLC of Baltimore, Maryland, USA. The curable composition can be introduced into a cavity of the mold through an appropriate conveyance that includes, in some embodiments, some form of measuring or metering of the quantity of the composition. In some implementations, an exact (with minimal tolerance), pre-determined quantity of the composition is introduced into the mold, and in some implementations, excess material is removed through a drain in the mold or in a downstream process. The mold can be part of an apparatus that also includes a source of polymerizing radiation capable of solidifying the specific composition. An example of a polymerizing or curing radiation includes electromagnetic radiation in the ultraviolet spectrum, and especially in the upper end of the EV-A range, e.g., 390-400nm, or 395-405nm, or 395-400nm. In some implementations, a polymerizing wavelength or range of wavelengths depends on the formulation of the specific radiation-polymerizable composition. In some implementations, the wavelength is user- or software-selectable based on the specific composition used, and in some implementations different UV-radiation emitters, e.g., different lamps, are used in conjunction with different compositions requiring different wavelengths. The curable composition is rotated at a selected rotation speed that to produce a contour forming a concave paraboloid shape on an upper surface of the composition. The term ‘paraboloid’ is used herein to mean a three-dimensional shape having two or more nonparallel two-dimensional parabolic cross sections; the shape can be of a mass, e.g., a solid or a rotated non-solid, and / or the surface of the solid or a rotated non-solid mass. The terms ‘parabola’ and ‘parabolic’ are also used herein in the same sense as paraboloid, and no distinction between the two terms is made, as the term parabolic is often applied to paraboloid shapes in the vernacular. The paraboloid shapes referred to herein can be circular paraboloids, elliptical paraboloids, or any other paraboloid shapes meeting the above definition. In some embodiments, the rotation speed is selected at least in part of the basis of the desired paraboloid shape and / or total diopter (of the finished product). The rotation speed can also be selected at least in part on the basis of material composition, quantity , refractive index, and / or viscosity. In some implementations, the contour having the paraboloid (or parabolic) shape extends to the entire upper surface of the composition. In some implementations, the paraboloid contour extends only to a portion of the upper surface. In some embodiments, the curing can cause slight shrinkage of the composition and / or distortion of the pre-curing concave parabolic shape. For example the height of the cured composition above the mold floor can be reduced by up to 1%, or up to 2%, or up to 3%, or up to 4%, or up to 5%, or up to 10%, or by even more. In another example the final diopter of the cured composition can change by up to 0.05 diopter, or up to 0.1 diopter, or up to 0.15 diopter, or up to 0.2 diopter, or up to 0.25 diopter, or up to 0.3 diopter, or up to 0.35 diopter, or up to 0.4 diopter, or up to 0.45 diopter, or up to 0.5 diopter, or by even more, or less if limited by industiy standards. In some embodiments, the shrinkage or distortion is predictable and repeatable for a given material, material quantity and rotation speed, such that a final article can be still produced with great precision. In some embodiments, slight deviations in material composition and / or quantity, rotation speed and / or duration, or any other factor or combination of factors can cause the paraboloid contour to deviate from a ‘perfect’ paraboloid shape. For example, the height of the cured composition above the mold floor can be increased or reduced (or both at different locations) by up to 1%, or up to 2%, or up to 3%, or up to 4%, or up to 5%, or up to 10%. Any of the foregoing shrinkages, distortions or deviations are not substantial, and any resulting contour can still be considered to be ‘paraboloid’ in accordance with any of the embodiments disclosed herein. The floor of the mold has a shape selected for defining the shape of one of the two major surfaces of the optical article. For example, if the floor of the mode is planar, the optical article is fabricated with a planar major surface. If the floor of the mode, or at least a portion of the floor, has a concave spherical curvature, the optical article is fabricated with a corresponding convex spherical curvature. The floor portion can be shaped to accommodate, inter alia, a large variety of types of corrective lenses, including not only single-focus lenses but also progressive lenses, multifocal lenses, bifocal lenses, and including not only spherical lenses but also aspheric lenses. The mold is arranged to be rotated, e.g., by a low-speed electric motor. ‘Low speed’ in this context means under 200 revolutions per minute (rpm), e.g., 10-200 rpm, or 50-120 rpm, or 50-100 rpm, or 70-100 rpm, or 70-120 rpm, or any other suitable range below 200 rpm as will be further discussed hereinbelow. All ranges expressed in this disclosure are inclusive. Alternatively a higher speed motor, i.e., above 200 rpm, can be used in combination with gearing that keeps the rotating speed of the mold between 10 and 200 rpm, including, without limitation, within any of the ranges noted above. In some embodiments, a higher-speed motor can be employed to provide a higher rotation speed during a pre-production phase including, e.g., mixing or sonication of the polymerizable composition, and / or during a post-production phase that can include, e.g., spin coating. In some designs, the higher-speed motor is capable of sufficiently precise low-speed operation without a reduction gear, and in other designs a gearing arrangement is employed to deliver a low speed suitable for forming the optical article in the mold. Alternatively, other means of rotation such as magnetic induction can be employed to enable selectable-speed rotation across larger ranges. The rotating of the mold and of the radiation-polymerizable composition therewithin, when carried out at an appropriate speed of rotation, is effective to cause an upper surface of the composition to take on a concave paraboloid shape. After solidification of the composition, e.g., by polymerization, the parabolic shape formed by the rotating characterizes at least a portion of the second of the two major surfaces of the optical article. The speed of rotation may be selected on the basis of one or more parameters such as the quantity of material in the mold and the parabolic curvature desired. Other parameters affecting selection of the rotation speed directly or indirectly can include the prescription, e.g., diopter(s) and the refractive index of the radiation-polymerizable composition. In the case of optical lenses, a total power or diopter is derived from the combined curvatures of the two major surfaces. Thus, for a given final diopter, the shape of the parabola formed on the upper surface in the mold takes into account the shape of the floor on the bottom of the mold. The base curvature selected for the floor of the mold is another parameter that can affect the rotation speed. In various designs, the floor of the mold can be removable and replaceable, e.g., non-destructively removable and available for reuse or repeated reuse. In other designs, the floor of the mold can be permanently installed in the mold as a permanent component, or formed integrally with the mold. In some designs, a user selects a mold for use in a forming a particular optical article because of the floor portion matching a desired base curvature, and in other designs the user need only select a removable / reusable floor element for use, e.g., a non-destructively separable floor element, again based on matching a desired base curvature. The rotating of the mold can begin before, during or after the introduction of the composition into the mold. A determination of when the composition is introduced into the mold can depend, for example, on the dimensions of the mold, the viscosity of the composition, the throughput of the apparatus, and so on. The curing by exposure of the composition, or at least a portion of the composition, to the curing radiation can begin as soon as the parabolic shape formed on the upper surface reaches a steady state, e.g., at a constant speed of rotation. The duration of the rotation before beginning the curing step can be calculated in advance, or based on empirical history, e.g., for similar quantities of composition, for similar compositions, and / or for similar desired curvature. Additionally or alternatively, the shape can be observed by an optical sensor or other sensor which then triggers initiation of the irradiation. In some implementations, production of the optical article requires preliminary process steps, including, for example and without limitation: mixing of multiple components of the polymerizable composition, and / or sonication for mixing and / or de-aeration (i.e., bubble removal). In some implementations, fabrication of the final optical article requires further processing, including, for example and not exhaustively: machining, edging, cutting, stamping, polishing, grinding, and / or buffing, of one of the two major surfaces and / or of the edge of the article. In some implementations, the optical article leaves the mold in a finished condition, such that the fabrication, not including optional coating or printing, etc., is completed in the mold. In such implementations, it can be desirable to employ a mold having a shape corresponding to the desired contour of a finished optical article. Thus, the mold can be selected for use on the basis of its contour matching that of the final article to be molded. In some embodiments, the mold is designed to have foimed therein an eyeglass lens blank. In some embodiments, a removable mold insert corresponding to the contour of the article is employed, such that the same mold can be used for different products such as different eyeglass lenses. The removable mold insert can be held in inventory until needed, and optionally returned to inventor}' after use. Additionally or alternatively, the removable mold insert can be fabricated as a preliminary process step in the overall process of fabricating the optical article. For example, a 3D printer can be used to produce the removable mold insert, which is then inserted into the mold for fabricating the optical article. A system for producing optical articles according to embodiments can be modular or scalable to include multiple molds and / or multiple sources of polymerizing radiation, e.g., multiple apparatuses as the term is used herein. For example, an apparatus in a retail location may include a pair of molds in order to allow parallel production of both lenses of a pair of eyeglasses, or parallel production of two different eyeglass lens blanks for use in producing the final eyeglass lenses. In another implementation, a large array of molds can be arranged for supplier-scale production of lenses or other optical articles. Other elements including, for example, radiation sources, fluid conveyances and storage vessels, can be provided in whatever quantities are appropriate relative to the throughput of the molds. An apparatus according to embodiments can be part of a system that includes additional elements related to the fabrication of the optical articles such as coating and printing stations, as well as a control system that includes, inter alia, a user interface. The user interface can include one or more interface elements such as, and not exhaustively, a screen with a graphical user interface, a microphone, a barcode scanner or other visual sensor (e.g., for determining the power of an existing lens and / or the exact lens volume of a selected eyeglass frame). The control system can be programmed to calculate process parameters based on user inputs and other inputs, and to regulate the operation of any of the system elements, such that any fabrication system as disclosed herein can be mechanized, semi-automated, or fully automated. Referring now to the figures and in particular to Figs. 1 and 2, an apparatus 200 for use in fabricating an optical article 100 from a radiation-curable composition 15 comprises a rotatable mold 120. The mold 120 surrounds and / or encompasses a cavity 121 having a suitable diameter, for example (but not exhaustively), 50 mm, 65 mm or 80 mm. The rotation of the mold is necessary and effective to form the desired concave paraboloid shape on an upper surface of the radiation-curable composition 15 in the mold 120. According to embodiments, the mold 120 is configured, when electrically activated, to rotate at a selected or selectable speed so as to generate a centrifugal force that in combination with a gravitational force changes a contour of a second surface of the polymerizable composition 15 received in the mold 120 to a concave parabolic shape. In an example, in a first operating mode of the apparatus, when the mold 120 is rotated at a speed between 10 and 200 revolutions per minute while a radiati on-polymerizable composition having a viscosity between 20 and 500 cP at ambient temperature is resident therewithin, the rotating is effective to change a contour of a second surface of the polymerizable composition 15 to form a concave paraboloid shape. The expressions ‘rotatable’ and ‘arranged to be rotated’ mean, inter alia, that the mold 120 is connected mechanically, either directly or indirectly such as by a gearing arrangement, to a motor 110 (not shown) that is configured for, e.g., designed for and capable of rotation, and that the rotation of the motor 110 causes rotation of the mold 120 at a suitable rotation speed according to embodiments. The term ‘motor’ is used herein to include any means for converting electrical energy to kinetic energy of rotation, including, for purposes of illustration, magnetic induction. In some embodiments, the mold 120 comprises or is mechanically connected to a rotor element such that the mold 120 is part of an integral motor-mold assembly, and in other embodiments, the motor 110 is a separate element of the apparatus 200. The mold 120 can include a power connection 215 for powering a motor 110 (not shown). The mold 120 is arranged to be rotated at a selected speed that is appropriate to the process of producing optical elements 100 with a desired set of physical and optical parameters. In embodiments, an appropriate speed of rotation is a speed less than 200 revolutions per minute (rpm), for example (and not exhaustively) between 10 and 200 rpm, or between 10 and 150 rpm, or between 10 and 100 rpm, or between 30 and 200 rpm, or between 30 and 120 rpm, or between 30 and 100 rpm, or between 50 and 200 rpm, or between 50 and 150 rpm, or between 50 and 130 rpm, or between 50 and 120 rpm, or between 50 and 100 rpm, or between 70 and 200 rpm, or between 70 and 150 rpm, or between 70 and 130 rpm, or between 70 and 120 rpm, or between 70 and 100 rpm, or in any other range under 200 rpm. In embodiments, an internal volume of the mold 120 is defined, inter alia, by the shape of the floor 130 and the height of the surrounding rim, or wall 124. The shape of the upward-facing surface of the floor 130 is imparted during production of the optical article 100 to a lower surface of the optical article 100, e.g. , surface 82 of Fig. 3B. Thus, a curvature of the floor portion 130 of the mold defines a corresponding curvature of one of the two major surfaces of the optical article 100. For example, if the upward-facing surface of the floor portion 130 is concave, then the corresponding major surface of the optical article 100 is convex. The cross-sectional view of Fig. 2 shows a non-limiting example of a floor portion 130 having a concave, spherical curvature. An optical article 100 formed using this exemplary floor portion 130 has a major surface characterized by a convex, spherical curvature. In some embodiments, a floor portion is removable, i.e., non-destructively removable, from a mold, and optionally reusable with or without further treatment. This type of floor portion 130 allows for selection of an appropriate floor portion 130 on the basis of the design of a specific optical article. In some embodiments, a floor portion 130 is permanently affixed to the mold, i.e., is not removable without damaging the floor portion or the mold, and in some embodiments, the floor portion is an integral element of a mold or even integrally formed with the mold, e.g., formed together with the peripheral wall 124 of the mold 120. The latter two types of floor portion allow for selection of an appropriate mold 120 on the basis of the design of a specific optical article 100. In the non-limiting example of Figs. 1 and 2, the floor portion 130 is secured within the mold 120 by a mechanical arrangement to illustrate a specific design option out of many possible designs for retaining and / or affixing a floor portion 130 in a mold 120 according to the embodiments. In some embodiments, the floor portion 130, or at least an upper surface thereof, is treated to enable effective removal of the optical article 100 from the mold 120. The treatment can be pre-production and / or permanent, e.g., by providing the upper surface of the floor portion 130 with an optical-grade hard coating. Additionally or alternatively, the treatment can be performed before each use, e.g., before introduction of a polymerizable composition into the mold, and the treatment can include a material with lubricant or non-stick properties. The floor portion 130 can be fabricated, for example, from a glass or plastic; a transparent floor portion can be desirable in implementations in which irradiation of the polymerizable composition through the floor 130 (e.g., from below) is part of the curing process. The wall 124 of the mold, according to embodiments, can serve multiple functions including, without limitation, keeping the curable composition 15 inside the mold, especially during rotation, and to deliver an edge on the periphery of the optical article 100 in accordance with a designed or desired contour. In embodiments, suitable selection of a quantity of the composition 15 is one that avoids undesirable edge effects such as having a surrounding ring formed in the optical article 100, where such a ring would have to be removed post-curing. Suitable selection of the material of the mold wall 124 is one that promotes effective removal of the optical article 100 after curing. An illustrative and non-limiting example of suitable material for a mold wall 124 is a polyurethane coated with a polytetrafluoroethylene. As shown in Fig. 1, the mold 120 is arranged to be rotated about a center of rotation 128. In many implementations, i.e., for many types and forms of optical articles 100, the center of rotation 128 corresponds to an optical axis of the optical article 100. A center of rotation 128 need not be in the center of the mold; in embodiments, forming an optical article 100 having an off-center optical axis is accomplished by rotating the mold 120 asymmetrically about an off-center center of rotation 128 and not necessarily about its own center. Fig. 3A shows a perspective view of an optical article 100 produced from a radiation-curable composition 15 in a mold 120 such as that of Figs. 1 and 2, and Fig. 3B shows a section contour of the same optical article 100. In the non-limiting example of Figs. 3A and 3B, the optical article 100 is a single-focus positive-meniscus lens blank having a first major surface 82 (the lower surface in Fig. 3B) characterized by a spherical curvature, and a second major surface 81 (the upper surface) characterized by a parabolic curvature. According to embodiments, the rotating of the mold 120 with the curable composition 15 resident therein causes a portion of the curable composition 15 to displace, e.g., as a result of so-called centrifugal forces. The displacing of the portion of the composition 15 includes displacing radially outward away from the center of rotation 128 towards the outer perimeter. After a period of rotating, e.g. rotating at a constant speed, at least a portion of the upper surface of the composition 15 takes on a concave parabolic shape. At the constant speed of rotation, the parabolic shape reaches a steady state, such that in situ curing of the composition 15 during continued rotation of the mold 120 is effective to preserve the parabolic contour in the solidified composition 15 that forms the optical article 100. Figs. 4A and 4B provide a more detailed look at an exemplary floor portion 130 of a mold 120, and in particular a floor portion 130 capable of being used in producing the exemplary optical article 100 of Figs. 3A and 3B. The upper surface 131 of the floor portion 130 is precisely shaped for forming thereupon the spherical curvature of the bottom surface 81 of the optical article 100. The spherical curvature can be used, for example, for producing negative-meniscus and / or positivemeniscus lenses. Figures 5A-E show additional examples of floor portions 130 for producing respective optical articles 100. The floor portion 130 of Fig. 5A comprises an upper surface 131 with a planar shape, i.e., zero curvature, for producing an optical article 100 such as, for example, a planoconcave lens. Fig. 5B shows a floor portion 130 comprising a concave upper surface 131 for producing an optical article 100 such as, for example, a double-concave (or bi-concave) lens. Fig. 5C shows a floor portion 130 comprising an upper surface 131 characterized by an aspheric curvature, for producing an optical article 100 such as, for example, an aspheric lens. Figs. 5D and 5E illustrates examples of floor portions 130 comprising respective upper surfaces 131 having multiple curvatures or facets for producing optical articles 100 such as, for example, bifocal lenses. In other examples (not shown) floor portions comprise upper surfaces characterized by multiple curvatures allowing the production of multifocal and progressive lenses. The interior volume of the mold 120 of Figs. 1 and 2 was shown to have a circular footprint. It can be desirable at times to produce optical articles with different peripheral contours. For example, eyeglass lenses often have non-circular shapes. According to embodiments, non-circular optical lenses can be made by the rotational molding and curing techniques disclosed herein in any one of the following ways, and not exhaustively: molding the optical article to the desired contour; edging, cutting or trimming the optical article, after curing, to a desired contour; and selective irradiation of the polymerizable composition. Fig. 6 shows a non-limiting example of a mold contour insert 140 shaped to govern the peripheral contour of the optical article 100. The contour insert 140 comprises a wall 144 surrounding a volume (bounded from below by the upper surface 131 of the floor portion 130) in which the optical article 100 is molded by rotation of the mold 120 and exposed to polymerizing radiation. Like the wall 124 of the mold 120, selection of a suitable material of the insert wall 144 such as, for example, a polyurethane coated with a polytetrafluoroethylene can enable effective removal of the optical article 100 after curing. Furthermore, while the respective walls 124, 144 of the mold 120 and the contour insert 140 appear in the figures to be straight vertical walls, this is an artifact of producing the drawings, and the walls 124,144 can be contoured, i.e., transversely contoured, to form the desired edge profile of the final optical lens without further processing. In some embodiments, either of both of the mode wall 124 and the contour insert wall 144 have a height of at least 2 mm, or at least 3 mm, or at least 4 mm, or at least 5 mm, or at least 6 mm, or at least 7 mm, or at least 8 mm, or at least 9 mm, or at least 10 mm, or even more. Figs. 7A and 7B show the contour insert 140 of Fig. 6 resident in a mold 120 according to embodiments. As can be seen in the cross-section view of Fig. 7B, it can be desirable for the lower surface of the contour insert 140 to conform to the contour of the upper surface 131 of the floor portion 130. In some designs, a gap between a contour insert 140 and the upper surface 131 of a floor portion 130 is eliminated by the use of an appropriately shaped gasket (not shown). In embodiments, a contour insert 140 is user- or software-selected on the basis of user inputs establishing various parameters of the optical article 100. In some embodiments, the contour insert 140 is produced as part of a fabrication process, for example using additive manufacturing (3D printing) and then inserted into the mold 120. In some embodiments, the contour insert 140 is integrally formed with a mold 120, or the mold 120 is formed to have the shape of a contour insert so as to obviate the need for a contour insert; in such embodiments, the final mold 120, incorporating the shape associated in Figs. 6 and 7 A including the shape of the molding volume surrounded by the contour insert, can be produced as part of a fabrication process, for example using 3D printing. We now refer to Fig. 8, in which a block diagram shows components of an apparatus 200 for fabricating an optical article 100 from a radiation-polymerizable composition 15 according to embodiments. The solid lines in Fig. 8 (and in Fig. 14) represent elements or components that are present in every implementation of the embodiments, while the dashed lines represent elements or components that may be absent in some implementations. As previously discussed with reference to Figs. 1 and 2, the apparatus 200 comprises a powered, e.g., electrically powered, rotatable mold 120 shaped, i.e., having a volume appropriately sized and shaped to receive a quantity of the radiation-polymerizable composition 15. In embodiments, the mold 120 includes and, when operational, has inserted or installed therein a floor portion 130 shaped to impart a curvature to a first major surface (e.g., a bottom surface 82 as molded) of the optical article 100 formed upon the floor portion 130. In embodiments, the floor portion 130 can be non-destructively removable, non-removable or permanently affixed to the mold 120, or integrally formed with the mold 120, e.g., formed with the wall 124 of the mold 120. In some embodiments, the quantity of the polymerizable composition 15 is selected in accordance with physical parameters of the specific optical article 100 being formed in the mold 120, for example any of volume, weight, specific density, or any other parameter necessary to set the quantity of material. In some embodiments, the quantity is selected in accordance with the optical properties of the specific optical article 100 being formed in the mold 120, for example the diopter and / or refractive index of the optical article 100, and / or base curvature of the floor portion 130 that gets transferred to the first surface of the optical article 100. In some embodiments, the quantity of the polymerizable composition 15 supplied to the mold 120 is greater than that needed for the specific optical article 100, and the excess is drained from the mold and / or trimmed from the cured optical article 100. In either of these cases, the mold 120 is large enough to receive the delivered quantity. In some embodiments, the apparatus 200 includes a contour insert 140 such as that shown in Figs. 6 and 7A; in some embodiments, the molding volume of the contour insert 140 is integrated in the design. In some embodiments, the contour insert 140 and / or the mold 120 can be produced locally by a 3D printer. In some embodiments, the apparatus 200 comprises a motor 110. The motor can be disposed, for example in the housing 115 shown in Fig. 1. In some embodiments, other rotation means are used to rotate the mold 120, such as, for example, magnetic induction. The motor 110 - or alternative rotation means such as magnetic induction - is configured or configurable to cause rotation of the mold 120 at a constant speed less than 200 revolutions per minute in any of the speed ranges disclosed hereinabove. In some embodiments, the rotation speed of the motor is user- or software- selectable in increments of no more than 10 revolutions per minute. As shown in block diagram of Fig, 8, the apparatus 200 additionally comprises a source 250 of polymerizing radiation 25. Referring now to Fig. 9, the radiation source 250 is represented graphically by a UV flashlight, but the radiation source 250 can take on any form suitable for emitting polymerizing radiation 25 according to embodiments, and can include more than one emitter. To be operational, the radiation source 250 is configured to produce radiation 25 at least at a wavelength effective to solidify the specific radiation-polymerizable composition 15. In some embodiments, the wavelength is selectable by a user and / or by control system software. The radiation source 250 is arranged, as shown in the non-limiting example of Fig. 9, to irradiate at least a portion of the upper surface of the polymerizable composition 15 - in the mold 120 - with the polymerizing radiation 25. Additionally or alternatively, the radiation source 250 can include more than radiation source, such as the emitters 250 beneath and / or on the sides of the mold 120 in the non-limiting example of Fig. 10, which shows a detail of a cross section of the mold 120 of Fig. 9. In some embodiments, irradiating the curable composition 15 from more than one angle can shorten the time needed to solidify the composition 15. It can be desirable, including for this purpose, to employ a floor portion 130 that is transparent at least to the polymerizing wavelength of the emitters 250. In some embodiments, irradiating the polymerizable composition 15 can include selectively subjecting a first portion of an upper surface of the composition to the polymerizing radiation 25, while not subjecting a second portion of the upper surface. In a first example of selective irradiation, the radiation source 250 is masked in order to limit the radiation to that part of the composition that ultimately becomes the optical article 100. The masking at least partly prevents the polymerizing radiation from reaching that part of the composition 15 not intended to be in the final optical article 15. This approach is an alternative or an enhancement to edging or trimming the cured composition or to employing a contour insert 140. Fig. 11A schematically illustrates the use of an eyeglass-lens shaped mask 255 placed at or near the radiation source 250 in order to cure only an eyeglass-lens shaped portion of the composition 15 in the mold 120. Fig. 1 IB schematically illustrates the use of an eyeglass-lens shaped mask 255 placed at or near (or even within) the cavity of the mold 120 in order to cure only an eyeglass-lens shaped portion of the composition 15 in the mold 120. In other examples, eyeglass-lens shaped mask 255 can be anywhere between the radiation source 250 and the upper surface of the mold 120. Alternatively, the mask 255 can be placed on or over the mold 120, or anywhere between the radiation source 250 and the top of the mold 120 (or the top surface of the composition 15 in the mold 120) In a second example of selective radiation, a directable radiation emitter 250 is employed so as to irradiate the desired portion, e.g., only the desired portion or substantially only the desired portion. A laser emitter 270 tuned to emit light at the polymerizing wavelength(s), as shown schematically in Fig. 12, is a suitable directable radiation emitter. Other suitable directable radiation emitters include adjustable arrays of small emitters or emitters with electronically or mechanically narrowed beams. In some embodiments, an apparatus 200 additionally comprises a vessel 21 for storing a supply of a radiation-curable composition 15, as shown in block diagram of Fig. 8. The vessel 21 is arranged, e.g., appropriately sized and disposed in at least switchable fluid communication with the mold 120 to enable timely delivery of the composition 15 to the mold 120, e.g., through a fluid conveyance 35 arranged to mediate between the vessel 21 and the mold 120. The vessel 21 and fluid conveyance 35 are represented graphically in a non-limiting example of apparatus components in Fig. 13 as a simple container with a spigot. In other examples, vessels 21, fluid conveyances 35 can be more sophisticated and / or more industrialized while performing the same functions as the examples illustrated in Fig. 13. In yet another example, the vessel 21 can be a simple bottle and the corresponding fluid conveyance 37 can be a simple nozzle. In some embodiments, the fluid conveyance 35 includes a metering or measuring device 37 for metering or measuring the quantity of the composition 15 delivered to the mold 120 for each optical article 100. In some embodiments, the fluid conveyance 35 can be designed, built, and / or adjusted to supply the desired quantity without metering, for example, and without limitation, by regulating the duration of the supplying or by regulating an electrical parameter associated with the supplying. The size and quantity of the vessel(s) 21, the type and size of the fluid conveyance 35 as well as the type of metering device 37 are configurable to meet the requirements of the apparatus according to specific implementations. We refer again to Fig. 8. In some embodiments, two or more components of the polymerizable composition 15 are mixed externally to the mold 120 and prior to the introducing of the composition 15 into the mold 120. In a non-limiting example, one of the components is a colorant. In such embodiments, an external mixer 111 can comprise, without limitation, a static mixer, a mixing tube or a mixing container, and can be provided as part of the apparatus 200. In some embodiments, prefabrication mixing is carried out in the mold 120. In some embodiments, regardless of whether or where the mixing is carried out, a sonication probe 112 or equivalent de-aeration device is provided as part of the apparatus 200 for de-aeration, i.e., bubble-removing, of the composition 15. In some embodiments, regardless of where the mixing is carried out, a heater 113 is provided as part of the apparatus 200 for heating the mixer 111 or mold 120, e.g., for reducing the viscosity of the composition 15 for more effective or efficient mixing. In some embodiments, the apparatus 200 includes arrangements (not shown) for flowing an inert gas, e.g., Nz, to reduce the oxygen exposure of the composition 15. In some embodiments, the rotating and / or the curing are performed in an at least partly oxy gen-depleted atmosphere. We now refer to Fig. 14, which shows a block diagram of a system 500 for fabricating an optical article 100. The system 500 comprises at least a molding assembly 220 and electronic circuitry 150. The molding assembly' comprises a mold, e.g., the rotatable mold 120 of Figs. 1 and 2 surrounding a cavity 121 with a minimum diameter of 50 mm, for producing the optical article 100 from a radiation-polymerizable composition 15. The producing of the optical article in the mold 120 includes forming a parabolic shape on a surface of the radiation-polymerizable composition 15 by rotating the mold 120, e.g., at a constant speed slower than 200 rpm. The molding assembly 220 additionally comprises an emitter 250 of polymerizing radiation 25. The emitter 250 is arranged to solidify at least a portion of the polymerizable composition 15 by irradiation. In some embodiments, the system comprises a material supply assembly 230 that comprises one or more vessels 21 storing the radiation-polymerizable composition 15, and a conveyance 35 mediating between the vessel 21 and the mold 120, for supplying the radiation-polymerizable composition 15 to the mold 120. In embodiments, the electronic circuitry 150 comprises a control system 60 configured, e.g., programmed, to regulate operation of the molding assembly 220 in response to inputs, and a user interface 60. In some embodiments, the regulation includes operation of a material supply assembly 230. Some or all of the inputs are received through the user interface 60. Each input defines one or more parameters related to the shape of the optical article 100 and / or the composition of the optical article 100 and / or operation of the molding assembly 220 or material supply assembly 230. As shown in the block diagram of Fig. 15, an exemplary control system 50 comprises computing equipment and ancillary equipment configured for monitoring, controlling, regulating and / or actuating one or more components or sub-systems of the system 500. Depending on location customization, the control system can include any or all of (and not exhaustively): one or more computer processors 55, computer-readable storage media 58, 59, and a communications module 57. The computer-readable program storage media 58, 59 can include transient and / or transient storage, and can include one or more storage units, all in accordance with desired functionality and design choices. Some or all of the computer-readable program storage media 58, 59 can be cloud-based. In embodiments, the program storage 58 can be used for storing program instructions in firmware and / or software, for execution by the one or more processors 55: operating data and / or maintenance data relating to components of the system 500 and / or optical 100 articles produced any one or more of its sub-systems and their components can be stored in the data storage module 59. The communications module 57 can be configured to establish communications links with external computers, e.g., for software and firmware updates, database access, etc., and to interact with users via the user interface 60. In some embodiments, not all of the illustrated components of the control system 50 are provided. In some embodiments, not all of the communications arrangements are provided. In embodiments, the electronic circuitry 150 comprises a user interface 60 configured to receive user inputs and to provide, e.g., display and / or store, information about the fabrication of optical articles 100 using the system 500. As discussed hereinabove, a user interface 60 can include a screen, e.g., a touchscreen. In some embodiments, the user interface 60, or at least the screen portion of the user interface 60, is realized in a computer program or an app for a mobile device. In some embodiments, the user interface 60 includes a communications-enabled handheld device designed to run software or preloaded-software of tire interface. Sample screenshots of an exemplary user interface 60 are shown schematically in Figs. 16A, 16B and 16C. The three illustrations are non-limiting examples of types of information exchanged through the user interface. In other examples, more technical and detailed data is input, displayed and / or adjusted, while in yet other examples, fewer options are provided the user and more decisions may be made by software of the control system 50, e.g., using machine learning and artificial intelligence. Fig. 16A shows a screen displaying buttons that allow data entry of input parameters and / or for receiving image scans, barcode scans, and other major inputs. Fig. 16B shows another screen displaying buttons that offers the user an opportunity to check and / or adjust process parameters, including parameters based on inputs received via the screen shown in Fig. 16A. Fig. 16C shows a panel with status indicators showing the progress of the process of fabricating the optical article 100. Referring again to the block diagram of Fig. 14, the system 500 can include, according to some embodiments, one or more additional components. A first example of an additional component is a 3D printer 205 for fabricating, e.g., a contour insert 140 or a mold 120 having a molding volume shaped to form a final optical article 100, e.g., a mold 120 comprising an integral contour insert 140. A second example of an additional component is a fluid bath 208 for cleaning, e.g., chemical cleaning or ultrasonic cleaning of the optical article 100 formed in the mold 120. The fluid bath 208 can be accompanied by a drying station (not shown). A third example of an additional component is a spin coater 209 for coating the optical article 100 formed in the mold 120. The optical article 100 can be coated with one or more coatings, including, for example (and not exhaustively), a functional coating including a colorant, a protective hard coat, an anti-reflective or antiglare coating, and / or a superhydrophobic or antifog coating. A fourth example of an additional component is a printer 210 for adding, e.g., a tint layer or a photochromatic layer to a major surface of the optical article 100. The printer 210 is adapted to employ any appropriate technology for depositing a colorant directly or indirectly on a surface of the optical article 100 after being formed in the mold 120. A fifth example of an additional component is a quality control (QC) station 206 for final measurements and, if needed, adjustments, e.g., buffing or polishing. A sixth example of an additional component is a scanner (not shown) for measuring a shape or an internal space of an eyeglass frame, or a lensometer for assessing an existing, either or both deployed in communication with the control system 50 for transferring information needed for fabricating a new lens. Reference is made to Fig. 17, a photo-realistic rendering of a non-limiting example of a single-mold system 500 designed for tabletop operation. In some other examples, tabletop systems 500 are configured differently, with fewer or more optional components, and / or with more than one mold, and / or with more or less mechanization or automation. In some other examples, systems 500 can be wall-mounted or assembled on a floor. In some other examples, systems 500 can be scaled up to include multiple molds and components and reach industrial scale. The system 500 of Fig. 17 comprises at least the following elements (clockwise from the lower left side): a powered, rotatable mold 120 directly powered by a motor 110; a multi-purpose arm 45 that combines the functions of the polymerizing radiation emitter 250, a portion of the fluid conveyance 35 that supplies the polymerizable composition 15 (not shown) to the mold 120, a metering device 37 for metering defined quantities of the composition 15 for each optical article 100 to be formed in the mold 120, and a robotic or teleoperated suction grasper for handling and moving the formed, cured optical article 100, a printer 210 for depositing a colorant on a surface of the optical article 100; a user interface screen 60 in electronic communication with a control system 50 (not shown); a QC station 206; cartridges 21 storing multiple polymerizable compositions 15, alongside cartridges 22 storing multiple colorants for pre-mixing in the compositions 15 and / or for printing on the optical articles 100; and a fluid bath 208 for post-curing cleaning or treating of the optical article 100 after curing in the mold 120. An optional dryer is not shown. Discussion of a first method Referring now to Fig. 18A, a method is disclosed for fabricating an optical article 100. According to the method, the optical article 100 comprises first and second major surfaces 82, 81 respectively characterized at least in part by first and second curvatures. In some embodiments, the optical article 100 comprises an eyeglass lens blank. In some embodiments, the lens blank is a singlevision lens blank (with or without cylinder correction for astigmatism). In some embodiments, tire lens blank is a finished lens blank. In some embodiments, the optical article 100 comprises a corrective eyeglass lens. As illustrated by the flow chart in Fig. 18A, the method comprises at least the three steps S101, S102 and S103. Step S101 includes introducing a quantity of a radiation-polymerizable composition 15 into a mold 120, such as, for example, any of the molds 120 shown in Figs. 1, 2, 7A or 9. A floor portion 130 of the mold 120 is shaped for forming thereupon a surface 82 characterized at least in part by the first curvature. The mold 120 surrounds a cavity 121 having a diameter of at least 50 mm. In some embodiments, the minimum quantity of the composition 15 is 6 cc. In some embodiments, the quantity of the composition 15 is at most 15 cc. In some embodiments, the quantity of the composition 15 is within a range of 6 to 12 cc. In some embodiments, the quantity of the composition 15 is between 0.25 and 0.35 cc of composition per cm2 of cavity area, Step S102 includes rotating the mold 120 about a center of rotation 128 to cause a portion of the polymerizable composition 15 to displace, e.g., at least radially outward from the center of rotation 128. The displacing is effective to change a contour of an upper surface of the polymerizable composition 15 to a concave parabolic shape characterized at least in part by the second curvature. In embodiments, the rotating is at a speed of between 10 and 200 rpm. In some embodiments, the rotating is within any of the narrower ranges discussed hereinabove. Step S103 includes subjecting the polymerizable composition 15 to polymerizing radiation 25 so as to solidify the composition 15. In some embodiments, subjecting the polymerizable composition 15 to the polymerizing radiation 25 includes subjecting substantially all of the upper surface to the polymerizing radiation 25. Substantially as used herein means at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 99%. In some embodiments, subjecting the polymerizable composition 15 to the polymerizing radiation 25 includes selectively subjecting a first portion of the upper surface to the polymerizing radiation 25, and not subjecting a second portion of the upper surface to the polymerizing radiation 25. In some embodiments, ‘selectively subjecting’ includes masking the polymerizing radiation 25 from reaching the second portion, e.g., by installing a mask 255 to block the second portion of the radiation 25. In some embodiments, ‘selectively subjecting’ includes using a directable source of radiation, e.g., a laser emitter 270, to emit the polymerizing radiation 25 so as to irradiate only the first portion. In some embodiments, subjecting the polymerizable composition 15 to the polymerizing radiation 25 includes subjecting at least a portion of a lower surface of the polymerizable composition 15 to the polymerizing radiation 25. In some embodiments, at least a portion of the subjecting of the polymerizable composition 15 to the polymerizing radiation 25 is carried out during the rotating. In some embodiments, all of the subjecting of the polymerizable composition 15 to the polymerizing radiation 25 is earned out during the rotating. In some embodiments, the solidified composition 15 has a minimum thickness of at least 1 mm. In some embodiments, the solidified composition 15 has an average thickness of at least 2 mm. In some embodiments, the method can additionally comprise Step S104, illustrated by the flow chart in Fig. 18B. Step S104 includes selecting a floor portion 130 based on a parameter of the optical article 100. The parameter can include, without limitation, a type of lens such as, e.g., a bifocal or multifocal lens; a desired diopter; a shape, e.g., spherical vs. aspheric, or a material. In some embodiments, the method can additionally comprise Step S105, illustrated by tire flow chart in in Fig. 18C. Step S105 includes selecting a mold 120 on tire basis of a shape of its floor portion 130, the selecting being based on a parameter of the optical article 100 such as, without limitation, a type of lens such as, e.g., a bifocal or multifocal lens; a desired diopter; a shape, e.g., spherical vs. aspheric, or a material. In Step S105, as opposed to Step S014, the entire mold 120 can be chosen based on the floor portion 130 rather than just the floor portion 130 being chosen; Thus, Step S015 is more likely to be carried out as part of the method in implementations where the floor portion 130 is built in, permanently affixed to, or integrally formed with, the mold 120. In some embodiments, the method can additionally comprise Step S106, as illustrated by the flow chart in in Fig. 18D. Step S106 includes installing, in the mold 120, a non-destructively removable element, i.e., contour insert 140, governing a peripheral contour of the optical article 100. In some embodiments in which Step S106 is carried out, the method can additionally comprise Step S107, illustrated by the flow chart in in Fig. 18E. Step S107 includes selecting the removable element 140 governing the peripheral contour of the optical article 100, based on a parameter of the optical article 100. The parameter can include, without limitation, a shape, thickness or material of the optical article 100, or a model of a lens eyeglass frame. In some embodiments in which Step S106 is carried out, the method can additionally comprise Step S108, illustrated by the flow chart in in Fig. 18F. Step S108 includes fabricating the removable element 140 governing the peripheral contour of the optical article 100, e.g., by 3D printer 205. In some embodiments, the method can additionally comprise Step S109, illustrated by the flow chart in Fig. 18G. Step S109 includes carrying out at least one of: machining, grinding, stamping, buffing and polishing an edge of the solidified composition 15. In some embodiments, carrying out Step S109 completes the fabrication of the optical article 100. In some embodiments, the method can additionally comprise Step SI 10, illustrated by the flow chart in Fig. 18H. Step SI 10 includes carrying out at least one of machining, grinding, buffing and polishing a major surface 82,81 of the solidified composition 15. In some embodiments, carrying out Step S110 completes the fabrication of the optical article 100. In some embodiments, the method can additionally comprise Step Sill, illustrated by the flow chart in Fig. 181. Step Sill includes at least one of coating, printing, and depositing on at least one of the first and second major surfaces 82, 81. The printing or depositing can be carried out using, for example, printer 210. In some embodiments, the method can additionally comprise Step SI 12, illustrated by the flow chart in Fig. 18J. Step SI 12 includes curing the solidified composition 15. In some embodiments, carrying out Step SI 12 completes the fabrication of the optical article 100. The coating can be carried out using, for example, spin coater 209. The further curing can be carried out, for example, by an additional polymerizing-radiation emitter arranged away from the mold 120. In another example, the further curing of Step SI 12 includes thermal curing or hybrid thermal-radiation curing. In some embodiments, carrying out Step S03 (specifically, subjecting the polymerizable composition 15 to the polymerizing radiation 25) completes the fabrication of the optical article 100, in which case Steps S109, S110, Sill and S112 are not carried out. In some embodiments, the method can additionally comprise Step SI 13, illustrated by the flow chart in Fig. 18K. Step SI 13 includes installing the optical article 100 in an eyeglass frame. In some embodiments, the method can additionally comprise Step SI 14, illustrated by the flow chart in Fig. 18L. Step SI 14 includes adding a colorant to the radiation-polymerizable composition 15. In some embodiments, the colorant is added to and / or mixed with the composition 15 in the mold 120. In some embodiments, the colorant is added and / or mixed during the rotating. In some embodiments, the composition 15 comprises a colorant when it is introduced into the mold 120 in Step SOI. The colorant can be added to the composition before carrying out Step SOI, e.g., using a mixer 111. In some embodiments, the colorant of Step S113 comprises a photochromatic dye. In some embodiments, an automated fabrication system 500 comprises a powered rotatable mold 120, a source 250 of polymerizing radiation 25, and a control system 50 is programmed to carry out Steps S101, S102 and S103. Discussion of a second method Referring now to Fig. 19, a method is disclosed for fabricating an optical article 100. In some embodiments, the optical article 100 comprises a corrective eyeglass lens. In some embodiments, the optical article 100 comprises a progressive lens. In some embodiments, the optical article 100 comprises a multifocal lens. In some embodiments, the optical article 100 comprises a bifocal lens. In some embodiments, the optical article 100 comprises a colorant. As illustrated by the flow chart in Fig. 19, the method comprises at least the three steps S201, S202 and S203. Step S201 includes introducing a radiation-curable composition 15 into a mold 120 surrounding a cavity 121 having a diameter of at least 50 mm. According to the method, a floor portion 130 of the mold 120 shaped for forming thereupon a first surface 82 of the optical article 100. In some embodiments, the first surface 82 is characterized at least in part by a spherical curvature. In some embodiments, the first surface 82 is characterized at least in part by an aspheric curvature. In some embodiments, the first surface 82 is characterized at least in part by a zero curvature. In some embodiments, the first surface 82 is characterized by multiple different curvatures. In some embodiments, the first surface 82 is characterized by including one or more facets. Step S202 includes rotating the mold 120 about a center of rotation 128 to cause a portion of the radiation-curable composition 15 to displace to change a contour of an upper surface of the curable composition 15 to a concave parabolic shape. In some embodiments, the second surface 81 of the optical article 100 is characterized by a concave parabolic curvature. Step S203 includes subjecting the curable composition 15 to the curing radiation 25 to solidify the composition 15. In some embodiments, solidifying the composition 15 is effective to preserve the concave parabolic shape. Any of the methods and / or method steps disclosed herein can be carried out in any combination and in any order deemed useful for fabricating optical articles 100. In some embodiments, a fabrication system 500 comprising a powered rotatable mold 120 surrounding a cavity 121 having a diameter of at least 50 mm and a source 250 of polymerizing radiation 25 is configured to perform any of the methods and / or method steps disclosed herein to fabricate optical articles 100. A method is disclosed, according to embodiments, for fabricating an optical article comprising first and second major surfaces respectively characterized at least in part by first and second curvatures. The method comprises: (a) introducing a quantity of a radiation-polymerizable composition into a mold, a floor portion of the mold being shaped for forming thereupon a surface characterized at least in part by the first curvature; (b) rotating the mold to cause a portion of the radiation-curable composition to displace so as to change a contour of an upper surface of the curable composition to a concave parabolic shape characterized at least in part by the second curvature; and (c) subjecting the polymerizable composition to the polymerizing radiation to solidify the composition. According to embodiments, an apparatus for use in fabricating an optical article from a radiation-polymerizable composition comprises: (a) a powered rotatable mold shaped to receive a quantity of the radiation-polymerizable composition, the mold comprising a floor portion arranged for forming thereupon a first surface of the optical article and a peripheral wall portion having a minimum height at least 1 mm above a highest point of the floor portion; and (b) a source of polymerizing radiation arrangeable to irradiate at least a portion of the polymerizable composition with said polymerizing radiation so as to solidify the polymerizable composition. In a first operating mode of the apparatus, when the mold is rotated at a speed between 10 and 200 revolutions per minute while a radiation-polymerizable composition having a viscosity between 20 and 200 cP at ambient temperature is resident therewithin, the rotating is effective to change a contour of a second surface of the polymerizable composition to form a concave parabolic shape. According to embodiments, an apparatus for fabricating an optical article from a radiation-polymerizable composition comprises: (a) a mold shaped to receive a quantity of the radiation-polymerizable composition, the mold comprising a floor portion arranged for forming thereupon a first surface of the optical article, and configured, when electrically activated, to rotate at a selectable speed so as to generate a centrifugal force that in combination with a gravitational force changes a contour of a second surface of the polymerizable composition received in the mold to a concave parabolic shape; and (b) a source of polymerizing radiation aligned with the mold to irradiate, when activated, at least a portion of the polymerizable composition with said polymerizing radiation to solidify said portion A method is disclosed, according to embodiments, for fabricating an optical article. The method comprises: (a) introducing a radiation-curable composition into a mold, a floor portion of the mold being shaped for forming thereupon a first surface of the optical article; (b) rotating the mold about a center of rotation to cause a portion of the radiation-curable composition to displace to change a contour of an upper surface of the curable composition to a concave parabolic shape; and (c) subjecting the curable composition to the curing radiation to solidify the composition. According to embodiments, a system for fabricating an optical article comprises: (a) a molding assembly comprising (i) a rotatable mold adapted to produce therewithin the optical article from a radiation-polymerizable composition, wherein the producing includes forming a parabolic shape on a surface of the radiation-polymerizable composition by rotating the mold, and (ii) a source of polymerizing radiation arranged to solidify at least a portion of the polymerizable composition by irradiation thereof; (b) a material supply assembly comprising one or more vessels storing the radiation-polymerizable composition, and a conveyance for supplying therethrough, to the rotatable mold, a quantity of said radiation-polymerizable composition; and (c) electronic circuitry configured to regulate operation of the molding assembly and the material supply assembly in response to inputs received through a user interface, the inputs defining one or more shape and / or compositional parameters of the optical article. Inventive Concepts The present disclosure includes, inter alia, the following Inventive Concepts, numbered 1-181 for convenient reference. Inventive Concept 1: A method of fabricating an optical article comprising first and second major surfaces respectively characterized at least in part by first and second curvatures, the method comprising: (a) introducing a quantity of a radiation-polymerizable composition into a mold, a floor portion of the mold being shaped for forming thereupon a surface characterized at least in part by the first curvature; (b) rotating the mold to cause a portion of the radiation-curable composition to displace so as to change a contour of an upper surface of the curable composition to a concave parabolic shape characterized at least in part by the second curvature; and (c) subjecting the polymerizable composition to the polymerizing radiation to solidify the composition. Inventive Concept 2: The method of Inventive Concept 1, wherein the solidifying is effective to preserve the concave parabolic shape. Inventive Concept 3: The method of either one of Inventive Concepts 1 or 2, wherein the optical article comprises a lens. Inventive Concept 3 a: Inventive Concept 3: The method of either one of Inventive Concepts 1 or 2, wherein the optical article comprises an eyeglass lens blank. Inventive Concept 4: The method of any one of Inventive Concepts 1 to 3, wherein the optical article comprises a corrective eyeglass lens. Inventive Concept 5: The method of any one of Inventive Concepts 1 to 4, additionally comprising: selecting a floor portion based on a parameter of the optical article. Inventive Concept 6: The method of any one of Inventive Concepts 1 to 4, additionally comprising: selecting a mold on the basis of a shape of the floor portion, the selecting being based on a parameter of the optical article. Inventive Concept 7: The method of any one of Inventive Concepts 1 to 6, wherein the subjecting of the polymerizable composition to tire polymerizing radiation includes subjecting substantially all of said upper surface to the polymerizing radiation. Inventive Concept 8: The method of any one of Inventive Concepts 1 to 6, wherein the subjecting of the polymerizable composition to the polymerizing radiation includes selectively subjecting a first portion of said upper surface to the polymerizing radiation, and not subjecting a second portion of said upper surface. Inventive Concept 9: The method of Inventive Concept 8, wherein the selectively subjecting includes masking the polymerizing radiation from reaching said second portion. Inventive Concept 10: The method of Inventive Concept 8, wherein the selectively subjecting includes using a directable source of radiation to emit the polymerizing radiation. Inventive Concept 11: The method of any one of the preceding Inventive Concepts, wherein the subjecting of the polymerizable composition to the polymerizing radiation includes subjecting at least a portion of a lower surface of the polymerizable composition to the polymerizing radiation. Inventive Concept 12: The method of any one of the preceding Inventive Concepts, additionally comprising: installing, in the mold, a non-destructively removable element governing a peripheral contour of the optical article. Inventive Concept 13: The method of Inventive Concept 12, additionally comprising: selecting the removable element governing the peripheral contour of the optical article based on a parameter of the optical article. Inventive Concept 14: The method of Inventive Concept 12, additionally comprising: fabricating the removable element governing the peripheral contour of the optical article. Inventive Concept 15: The method of any one of the preceding Inventive Concepts, additionally comprising at least one of machining, grinding, stamping, buffing and polishing an edge of the solidified composition. Inventive Concept 16: The method of any one of the preceding Inventive Concepts, additionally comprising at least one of machining, grinding, buffing and polishing a major surface of the solidified composition. Inventive Concept 17: The method of any one of the preceding Inventive Concepts, additionally comprising at least one of coating, printing, depositing, on at least one of the first and second major surfaces. Inventive Concept 18: The method of any one of the preceding Inventive Concepts, additionally comprising: further curing the solidified composition. Inventive Concept 19: The method of any one of the preceding Inventive Concepts, wherein the subjecting of the polymerizable composition to the polymerizing radiation completes the fabrication of the optical article. Inventive Concept 20: The method of any one of the preceding Inventive Concepts, additionally comprising: installing the optical article in an eyeglass frame. Inventive Concept 21: The method of any one of the preceding Inventive Concepts, wherein the rotating is at a speed of less than 500 revolutions per minute. Inventive Concept 21 A: The method of Inventive Concept 21, wherein the speed is at most 300 RPM. Inventive Concept 21B: The method of Inventive Concept 21, wherein the speed is at most 250 RPM. Inventive Concept 21C: The method of Inventive Concept 21, wherein the speed is at most 200 RPM. Inventive Concept 2ID: The method of Inventive Concept 21, wherein the speed is at most 180 RPM. Inventive Concept 2IE: The method of Inventive Concept 21, wherein tire speed is at most 160 RPM. Inventive Concept 21F: The method of Inventive Concept 21, wherein the speed is at most 150 RPM. Inventive Concept 21G: The method of Inventive Concept 21, wherein the speed is at most 140 RPM. Inventive Concept 21H: The method of Inventive Concept 21, wherein the speed is at most 130 RPM. Inventive Concept 211: The method of Inventive Concept 21, wherein the speed is at most 120 RPM. Inventive Concept 21 J: The method of Inventive Concept 21, wherein the speed is at most 110 RPM. Inventive Concept 21K: The method of any one of Inventive Concepts 21 to 21J, wherein the speed is at least 10 RPM. Inventive Concept 21L: The method of Inventive Concept 21K, wherein the speed is at least 20 RPM. Inventive Concept 2IM: The method of Inventive Concept 2IK, wherein the speed is at least 25 RPM. Inventive Concept 21N: The method of Inventive Concept 21K, wherein the speed is at least 30 RPM. Inventive Concept 210: The method of Inventive Concept 21K, wherein the speed is at least 40 RPM. Inventive Concept 2IP: The method of Inventive Concept 2IK, wherein the speed is at least 50 RPM. Inventive Concept 2 IQ: The method of Inventive Concept 2 IK, wherein the speed is at least 60 RPM. Inventive Concept 21R: The method of Inventive Concept 21K, wherein the speed is at least 70 RPM. Inventive Concept 22: The method of any one of the preceding Inventive Concepts, wherein the rotating is at a speed of between 10 and 300 revolutions per minute. Inventive Concept 23: The method of any one of the preceding Inventive Concepts, wherein the rotating is at a speed of between 40 and 100 revolutions per minute. Inventive Concept 24: The method of any one of the preceding Inventive Concepts, additionally comprising: adding a colorant to the radiation-polymerizable composition. Inventive Concept 25: The method of Inventive Concept 24, wherein the colorant is added in the mold. Inventive Concept 26: The method of Inventive Concept 23, wherein the colorant is added during the rotating. Inventive Concept 27: The method of any one of Inventive Concepts 1 to 23, wherein the composition comprises a colorant. Inventive Concept 28: The method of any one of Inventive Concepts 24 to 27, wherein the colorant comprises a photochromatic dye. Inventive Concept 29: The method of any one of the preceding Inventive Concepts, wherein at least a portion of the subjecting of the polymerizable composition to the polymerizing radiation is carried out during the rotating. Inventive Concept 30: The method of any one of the preceding Inventive Concepts, wherein a second surface of the optical article is characterized by a concave parabolic curvature. Inventive Concept 31: The method of any one of the preceding Inventive Concepts, wherein the optical article comprises a progressive lens. Inventive Concept 32: The method of any one of the preceding Inventive Concepts, wherein the optical article comprises a multifocal lens. Inventive Concept 33: The method of any one of the preceding Inventive Concepts, wherein the optical article comprises a bifocal lens. Inventive Concept 34: The method of any one of the preceding Inventive Concepts, wherein the first surface is characterized at least in pail by a spherical curvature. Inventive Concept 35: The method of any one of the preceding Inventive Concepts, wherein the first surface is characterized at least in part by an aspheric curvature. Inventive Concept 36: The method of any one of the preceding Inventive Concepts, wherein the first surface is characterized at least in part by a zero curvature. Inventive Concept 37: The method of any one of the preceding Inventive Concepts, wherein the first surface is characterized by multiple different curvatures. Inventive Concept 38: The method of any one of the preceding Inventive Concepts, wherein the first surface is characterized by including one or more facets. Inventive Concept 39: The method of any one of the preceding Inventive Concepts, wherein the optical article comprises a colorant. Inventive Concept 40: An apparatus for use in carrying out the method of any one of the preceding Inventive Concepts, the apparatus comprising a powered rotatable mold and a source of polymerizing radiation arranged to subject the polymerizable composition to the polymerizing radiation. Inventive Concept 41: A fabrication system configured to perform the method of any one of Inventive Concepts 1 to 39, the fabrication system comprising a powered rotatable mold and a source of polymerizing radiation. Inventive Concept 42: An automated fabrication system comprising a powered rotatable mold, a source of polymerizing radiation, and a control system programmed to carry out the introducing, rotating and subjecting of any one of Inventive Concepts 1 to 39. Inventive Concept 43: An optical article fabricated using any one of the methods of Inventive Concepts 1 to 39. Inventive Concept 44: An apparatus for use in fabricating an optical article from a radiation-polymerizable composition, the apparatus comprising: (a) a powered rotatable mold shaped to receive a quantity of the radiation-polymerizable composition, the mold comprising a floor portion arranged for forming thereupon a first surface of the optical article and a peripheral wall portion having a minimum height at least 1 mm above a highest point of the floor portion; and (b) a source of polymerizing radiation arrangeable to irradiate at least a portion of the polymerizable composition with said polymerizing radiation so as to solidify the polymerizable composition, wherein in a first operating mode of the apparatus, when the mold is rotated at a speed between 10 and 200 revolutions per minute while a radiation-polymerizable composition having a viscosity between 20 and 200 cP at ambient temperature is resident therewithin, the rotating is effective to change a contour of a second surface of the polymerizable composition to form a concave parabolic shape. Inventive Concept 45: The apparatus of Inventive Concept 44, additionally comprising a vessel arranged to store a supply of the radiation-polymerizable composition; Inventive Concept 46: The apparatus of either one of Inventive Concepts 44 or 45, additionally comprising a fluid conveyance for supplying therethrough, to the rotatable mold, a quantity of said radiation-polymerizable composition. Inventive Concept 47: The apparatus of Inventive Concept 46, wherein the fluid conveyance includes a metering or measuring device for metering or measuring the quantity of said radiation-polymerizable composition. Inventive Concept 48: The apparatus of any one of Inventive Concepts 44 to 47, wherein the mold includes a non-destructively removable element comprising said floor portion. Inventive Concept 49: The apparatus of any one of Inventive Concepts 44 to 47, wherein the floor portion is permanently affixed to the mold. Inventive Concept 50: The apparatus of any one of Inventive Concepts 40 to 47, wherein the floor portion is integrally formed with the mold. Inventive Concept 51: The apparatus of any one of Inventive Concepts 44 to 50, wherein a minimum height of the wall portion of the mold is at least 2 mm above the highest point of the floor portion. Inventive Concept 52: The apparatus of any one of Inventive Concepts 44 to 51, wherein the mold comprises a non-destructively removable element governing a peripheral contour of the optical article. Inventive Concept 53: The apparatus of Inventive Concept 52, wherein a minimum height of the removable element governing the peripheral contour is at least 2 mm above a highest point of the floor portion. Inventive Concept 54: The apparatus of any one of Inventive Concepts 44 to 53, comprising a motor configured to rotate the mold at a constant speed less than 500 revolutions per minute. Inventive Concept 55: The apparatus of any one of Inventive Concepts 44 to 53, comprising a motor configured to rotate the mold at a constant speed between 10 and 300 revolutions per minute. Inventive Concept 56: The apparatus of any one of Inventive Concepts 54 or 55, wherein the speed is selectable in increments of no more than 10 revolutions per minute. Inventive Concept 57: The apparatus of any one of Inventive Concepts 44 to 56, wherein the source of polymerizing radiation is wavelength-selectable. Inventive Concept 58: The apparatus of any one of Inventive Concepts 44 to 57, wherein the source of polymerizing radiation is directable. Inventive Concept 59: The apparatus of any one of Inventive Concepts 44 to 57, wherein the source of polymerizing radiation comprises an adjustable or replaceable mask. Inventive Concept 60: The apparatus of any one of Inventive Concepts 44 to 59, wherein the source of polymerizing radiation is arranged to irradiate a portion of the polymerizable composition that is not on the upper surface. Inventive Concept 61: A method of fabricating an optical article, the method comprising: (a) introducing a radiation-curable composition into a mold, a floor portion of the mold being shaped for forming thereupon a first surface of the optical article: (b) rotating the mold about a center of rotation thereof to cause a portion of the radiation-curable composition to displace so as to change a contour of an upper surface of the curable composition to a concave parabolic shape; and (c) subjecting the curable composition to the curing radiation to solidify the composition. Inventive Concept 62: The method of Inventive Concept 61, wherein the solidifying is effective to preserve the concave parabolic shape. Inventive Concept 63: The method of Inventive Concept 61, wherein a second surface of the optical article is characterized by a concave parabolic curvature. Inventive Concept 64: The method of any one of Inventive Concepts 61 to 63, wherein the optical article comprises a corrective eyeglass lens. Inventive Concept 65: The method of Inventive Concept 64, wherein the optical article comprises a progressive lens. Inventive Concept 66: The method of Inventive Concept 64, wherein the optical article comprises a multifocal lens. Inventive Concept 67: The method of Inventive Concept 64, wherein the optical article comprises a bifocal lens. Inventive Concept 68: The method of any one of Inventive Concepts 61 to 67, wherein the first surface is characterized at least in part by a spherical curvature. Inventive Concept 69: The method of any one of Inventive Concepts 61 to 67, wherein the first surface is characterized at least in part by an aspheric curvature. Inventive Concept 70: The method of any one of Inventive Concepts 61 to 67, wherein the first surface is characterized at least in part by a zero curvature. Inventive Concept 71: The method of any one of Inventive Concepts 61 to 67, wherein the first surface is characterized by multiple different curvatures. Inventive Concept 72: The method of any one of Inventive Concepts 61 to 67, wherein the first surface is characterized by including one or more facets. Inventive Concept 73: The method of any one of Inventive Concepts 61 to 72, wherein the optical article comprises a colorant. Inventive Concept 74: The method of any one of Inventive Concepts 61 to 73, wherein the solidifying is effective to preserve the concave parabolic shape. Inventive Concept 75: The method of any one of Inventive Concepts 61 to 74, wherein the optical article comprises a lens. Inventive Concept 76: The method of any one of Inventive Concepts 61 to 75, additionally comprising: selecting a floor portion based on a parameter of the optical article. Inventive Concept 77: The method of any one of Inventive Concepts 61 to 75, additionally comprising: selecting a mold on the basis of a shape of the floor portion, the selecting being based on a parameter of the optical article. Inventive Concept 78: The method of any one of Inventive Concepts 61 to 77, wherein the subjecting of the polymerizable composition to the polymerizing radiation includes subjecting substantially all of said upper surface to the polymerizing radiation. Inventive Concept 79: The method of any one of Inventive Concepts 61 to 77, wherein the subjecting of the polymerizable composition to the polymerizing radiation includes selectively subjecting a first portion of said upper surface to the polymerizing radiation, and not subjecting a second portion of said upper surface. Inventive Concept 80: The method of Inventive Concept 79, wherein the selectively subjecting includes masking the polymerizing radiation from reaching said second portion. Inventive Concept 81: The method of Inventive Concept 79, wherein the selectively subjecting includes using a directable source of radiation to emit the polymerizing radiation. Inventive Concept 82: The method of any one of Inventive Concepts 61 to 81, wherein the subjecting of the polymerizable composition to the polymerizing radiation includes subjecting at least a portion of a lower surface of the polymerizable composition to the polymerizing radiation. Inventive Concept 83: The method of any one of Inventive Concepts 61 to 81, additionally comprising: installing, in the mold, a non-destmctively removable element governing a peripheral contour of the optical article. Inventive Concept 84: The method of Inventive Concept 83, additionally comprising: selecting the removable element governing the peripheral contour of the optical article based on a parameter of the optical article. Inventive Concept 85: The method of Inventive Concept 83, additionally comprising: fabricating the removable element governing the peripheral contour of the optical article. Inventive Concept 86: The method of any one of Inventive Concepts 61 to 85, additionally comprising at least one of machining, grinding, stamping, buffing and polishing an edge of the solidified composition. Inventive Concept 87: The method of any one of Inventive Concepts 61 to 86, additionally comprising at least one of machining, grinding, buffing and polishing a major surface of the solidified composition. Inventive Concept 88: The method of any one of Inventive Concepts 61 to 87, additionally comprising at least one of coating, printing, depositing, on at least one of the first and second major surfaces. Inventive Concept 89: The method of any one of Inventive Concepts 61 to 88, additionally comprising: further curing the solidified composition. Inventive Concept 90: The method of any one of Inventive Concepts 61 to 89, wherein the subjecting of the polymerizable composition to the polymerizing radiation completes the fabrication of the optical article. Inventive Concept 91: The method of any one of Inventive Concepts 61 to 90, additionally comprising: installing the optical article in an eyeglass frame. Inventive Concept 92: The method of any one of Inventive Concepts 61 to 91, wherein the rotating is at a speed of less than 500 revolutions per minute. Inventive Concept 93: The method of any one of Inventive Concepts 61 to 92, wherein the rotating is at a speed of between 10 and 300 revolutions per minute. Inventive Concept 94: The method of any one of Inventive Concepts 61 to 93, wherein the rotating is at a speed of between 40 and 100 revolutions per minute. Inventive Concept 95: The method of any one of Inventive Concepts 61 to 94, additionally comprising: adding a colorant to the radiation-polymerizable composition. Inventive Concept 96: The method of Inventive Concept 95, wherein the colorant is added in the mold. Inventive Concept 97: The method of Inventive Concept 95, wherein the colorant is added during the rotating. Inventive Concept 98: The method of any one of Inventive Concepts 61 to 94, wherein the composition comprises a colorant. Inventive Concept 99: The method of any one of Inventive Concepts 95 to 98, wherein the colorant comprises a photochromatic dye. Inventive Concept 100: The method of any one of Inventive Concepts 61 to 99, wherein at least a portion of the subjecting of the polymerizable composition to the polymerizing radiation is carried out during the rotating. Inventive Concept 101: The method of any one of Inventive Concepts 61 to 100, wherein the solidifying is effective to preserve the concave parabolic shape. Inventive Concept 102: The method of any one of Inventive Concepts 61 to 101, wherein a second surface of the optical article is characterized by a concave parabolic curvature. Inventive Concept 103: The method of any one of Inventive Concepts 61 to 102, wherein the optical article comprises a corrective eyeglass lens. Inventive Concept 104: The method of any one of Inventive Concepts 61 to 103, wherein the optical article comprises a progressive lens. Inventive Concept 105: The method of any one of Inventive Concepts 61 to 103, wherein the optical article comprises a multifocal lens. Inventive Concept 106: The method of any one of Inventive Concepts 61 to 103, wherein the optical article comprises a bifocal lens. Inventive Concept 107: The method of any one of Inventive Concepts 61 to 106, wherein tire first surface is characterized at least in part by a spherical curvature. Inventive Concept 108: The method of any one of Inventive Concepts 61 to 106, wherein the first surface is characterized at least in part by an aspheric curvature. Inventive Concept 109: The method of any one of Inventive Concepts 61 to 106, wherein the first surface is characterized at least in part by a zero curvature. Inventive Concept 110: The method of any one of Inventive Concepts 61 to 109, wherein the first surface is characterized by multiple different curvatures. Inventive Concept 111: The method of any one of Inventive Concepts 61 to 110, wherein the first surface is characterized by including one or more facets. Inventive Concept 112: The method of any one of Inventive Concepts 61 to 111, wherein the optical article comprises a colorant. Inventive Concept 113. A system for fabricating an optical article, the system comprising: (a) a molding assembly comprising (i) a rotatable mold adapted to produce therewithin the optical article from a radiation-polymerizable composition, wherein the producing includes forming a parabolic shape on a surface of the radiation-polymerizable composition by rotating the mold, and (ii) a source of polymerizing radiation arranged to solidify at least a portion of the polymerizable composition by irradiation thereof; and (b) electronic circuitry configured to regulate operation of the molding assembly in response to inputs received through a user interface, the inputs defining one or more shape and / or compositional parameters of the optical article. Inventive Concept 114: The system of Inventive Concept 113, additionally comprising a material supply assembly comprising one or more vessels storing the radiation-polymerizable composition, and a conveyance for supplying therethrough, to the rotatable mold, a quantity of said radiation-polymerizable composition. Inventive Concept 115: The system of Inventive Concept 114, wherein the electronic circuitry is additionally configured to regulate operation of the material supply assembly. Inventive Concept 116: The system of any one of Inventive Concepts 113 to 115, wherein the user interface includes an interactive input device. Inventive Concept 117: The system of any one of Inventive Concepts 113 to 116, wherein the electronic circuitiy is in communication with a product database. Inventive Concept 118: The system of any one of Inventive Concepts 113 to 117, wherein the electronic circuitry is configured to determine an operating parameter based at least in part on one or more of said inputs. Inventive Concept 119: The system of Inventive Concept 118, wherein the operating parameter includes a rotation speed of the mold. Inventive Concept 120: The system of Inventive Concept 118, wherein the operating parameter includes the quantity of said radiation-polymerizable composition. Inventive Concept 121: The system of Inventive Concept 118, wherein the operating parameter includes a rotation time for forming the parabolic shape. Inventive Concept 122: The system of Inventive Concept 121, wherein the electronic circuitiy is programmed to initiate the irradiating of the polymerizable composition with the polymerizing radiation after the rotation time. Inventive Concept 123: The system of Inventive Concept 121, wherein the electronic circuitry is programmed to initiate the irradiating of the polymerizable composition with the polymerizing radiation in response to an input from a sensor. Inventive Concept 124: The system of Inventive Concept 123, additionally comprising a visual sensor arranged to monitor a level of the radiation-polymerizable composition. Inventive Concept 125: The system of any one of Inventive Concepts 118 to 124, wherein the one or more inputs include prescription data for the optical article. Inventive Concept 126: The system of any one of Inventive Concepts 118 to 124, wherein the one or more inputs include a refractive index of the radiation-polymerizable composition. Inventive Concept 127: The system of any one of Inventive Concepts 118 to 124, wherein the one or more inputs include a color. Inventive Concept 128: The system of any one of Inventive Concepts 118 to 124, wherein the one or more inputs include a shape of the optical article. Inventive Concept 129: The system of any one of Inventive Concepts 118 to 124, wherein the one or more inputs include a model designation of a lens and / or of an eyeglass frame. Inventive Concept 130: The system of any one of Inventive Concepts 113 to 129, additionally comprising a fluid bath for post-processing. Inventive Concept 131: The system of any one of Inventive Concepts 113 to 130, additionally comprising a printing system for postprocessing. Inventive Concept 131 A: The system of any one of Inventive Concepts 113 to 131, additionally comprising a 3D printer for fabricating tire removable element governing a peripheral contour of the optical article. Inventive Concept 132: The system of any one of Inventive Concepts 113 to 131 A, additionally comprising any of the structural features of Inventive Concepts 1 to 112. Inventive Concept 133. An apparatus for fabricating an optical article from a radiation-polymerizable composition, the apparatus comprising: (a) a mold shaped to receive a quantity of the radiation-polymerizable composition, the mold comprising a floor portion arranged for forming thereupon a first surface of the optical article, and configured, when electrically activated, to rotate at a selectable speed so as to generate a centrifugal force that in combination with a gravitational force changes a contour of a second surface of the polymerizable composition received in the mold to a concave parabolic shape; and (b) a source of polymerizing radiation aligned with the mold to irradiate, when activated, at least a portion of the polymerizable composition with said polymerizing radiation to solidify said portion. Inventive Concept 134: The apparatus of Inventive Concept 133, additionally comprising a vessel arranged to store a supply of the radiation-polymerizable composition; Inventive Concept 135: The apparatus of either one of Inventive Concepts 133 or 134, additionally comprising a fluid conveyance for supplying therethrough, to the rotatable mold, a quantity of said radiation-polymerizable composition. Inventive Concept 136: The apparatus of Inventive Concept 135, wherein the fluid conveyance includes a metering or measuring device for metering or measuring the quantity of said radiation-polymerizable composition. Inventive Concept 137: The apparatus of any one of Inventive Concepts 133 to 136, wherein the mold includes a non-destructively removable element comprising said floor portion. Inventive Concept 138: The apparatus of any one of Inventive Concepts 133 to 136, wherein the floor portion is permanently affixed to the mold. Inventive Concept 139: The apparatus of any one of Inventive Concepts 133 to 136, wherein the floor portion is integrally formed with the mold. Inventive Concept 140: The apparatus of any one of Inventive Concepts 133 to 139, wherein a minimum height of a wall portion of the mold is at least 2 mm above the highest point of the floor portion. Inventive Concept 141: The apparatus of any one of Inventive Concepts 133 to 140, wherein the mold comprises a non-destructively removable element governing a peripheral contour of the optical article. Inventive Concept 142: The apparatus of Inventive Concept 141, wherein a minimum height of the removable element governing the peripheral contour is at least 2 mm above a highest point of the floor portion. Inventive Concept 143: The apparatus of any one of Inventive Concepts 133 to 142, comprising a motor configured to rotate the mold at a constant speed less than 500 revolutions per minute. Inventive Concept 144: The apparatus of any one of Inventive Concepts 133 to 142, comprising a motor configured to rotate the mold at a constant speed between 10 and 300 revolutions per minute. Inventive Concept 145: The apparatus of any one of Inventive Concepts 143 or 144, wherein the speed is selectable in increments of no more than 10 revolutions per minute. Inventive Concept 146: The apparatus of any one of Inventive Concepts 133 to 145, wherein the source of polymerizing radiation is wavelength-selectable. Inventive Concept 147: The apparatus of any one of Inventive Concepts 133 to 146, wherein the source of polymerizing radiation is directable. Inventive Concept 148: The apparatus of any one of Inventive Concepts 133 to 147, wherein the source of polymerizing radiation comprises an adjustable or replaceable mask. Inventive Concept 148A: The apparatus of any one of Inventive Concepts 133 to 148, wherein the source of polymerizing radiation is arranged to irradiate a portion of the polymerizable composition that is not on the upper surface. Inventive Concept 149: The apparatus of any one of Inventive Concepts 133 to 148A, additionally comprising any of the structural features of Inventive Concepts 1 to 132. Inventive Concept 150. An optical article comprising a first major surface characterized at least in part by a convex spherical curvature and a second major surface characterized at least in part by a concave parabolic curvature. Inventive Concept 151. An optical article comprising a first major surface characterized at least in part by an aspheric curvature and a second major surface characterized at least in part by a concave parabolic curvature. Inventive Concept 152. An optical article comprising a first major surface characterized at least in part by a zero curvature and a second major surface characterized at least in part by a concave parabolic curvature. Inventive Concept 153: An optical article comprising a first major surface characterized at least in part by a multiple different curvatures and a second major surface characterized at least in part by a concave parabolic curvature. Inventive Concept 154: An optical article comprising a first major surface characterized at least in part by a concave spherical curvature and a second major surface characterized at least in part by a concave parabolic curvature. Inventive Concept 155: The optical article of any one of Inventive Concepts 150 to 151, wherein the second surface comprises a parabolic vertex of the parabolic curvature. Inventive Concept 156: The optical article of Inventive Concept 156, wherein an optical axis thereof passes through the parabolic vertex. Inventive Concept 156A: The optical article of either one of Inventive Concepts 155 or 156, wherein the parabolic vertex is not located at a centroid of the optical article. Inventive Concept 157: The optical article of any one of Inventive Concepts 150 to 156A, produced according to a method according to any one of the above-provided Inventive Concepts. Inventive Concept 158: A method of fabricating an eyeglass lens blank, the method comprising: (a) introducing a radiation-curable composition into a mold surrounding a cavity having a diameter of at least 50 mm, a floor portion of the mold being shaped for forming thereupon a first surface of the eyeglass lens; (b) rotating the mold, at a speed of at least 30 rpm and not more than 120 rpm, about a center of rotation thereof to cause a portion of the radiation-curable composition to displace so as to change a contour of an upper surface of the curable composition to a concave paraboloid shape; and (c) subjecting the curable composition to the curing radiation to solidify the composition. Inventive Concept 159: The method of Inventive Concept 158, wherein the solidified composition has a minimum thickness of at least 1 mm. Inventive Concept 160: The method of either one of Inventive Concepts 158 or 159, wherein the solidified composition has an average thickness of at least 2 mm. Inventive Concept 161: The method of any one of Inventive Concepts 158 to 160, wherein the introduced quantity has a volume of at least 6 cc. Inventive Concept 161A: The method of any one of Inventive Concepts 158 to 160, wherein the introduced quantity has a volume of at most 15 cc. Inventive Concept 161B: The method of Inventive Concept 161 A, wherein the introduced quantity has a volume of at most 12 cc. Inventive Concept 162: The method of any one of Inventive Concepts 158 to 161A, wherein the eyeglass lens blank comprises a single-vision lens blank. Inventive Concept 163: The method of any one of Inventive Concepts 158 to 162, wherein the eyeglass lens blank comprises a finished lens blank. Inventive Concept 164: The method of claim of any one of Inventive Concepts 158 to 163, additionally comprising: selecting the floor portion based on at least one of a diopter and a refractive index of the eyeglass lens blank, and installing the floor portion in the mold. Inventive Concept 165: The method of any one of Inventive Concepts 158 to 164, wherein the floor portion is non-destructively separable from the mold. Inventive Concept 166: The method of any one of Inventive Concepts 158 to 163, additionally comprising: selecting the mold based on at least one of a diopter and a refractive index of the eyeglass lens blank. Inventive Concept 167: The method of any one of Inventive Concepts 158 to 166, wherein the subjecting of the polymerizable composition to the polymerizing radiation includes subjecting at least a portion of a lower surface of the polymerizable composition to the polymerizing radiation. Inventive Concept 168: The method of any one of Inventive Concepts 158 to 167, wherein at least a portion of the subjecting of the polymerizable composition to the polymerizing radiation is carried out during the rotating. Inventive Concept 168a: The method of any one of Inventive Concepts 158 to 168, comprising any method step of any one of the above-provided Inventive Concepts. Inventive Concept 169: An apparatus for use in carrying out the method of any one of Inventive Concepts 158 to 168, the apparatus comprising a powered rotatable mold surrounding a cavity having a diameter of at least 50 mm, and a source of polymerizing radiation arranged to subject the polymerizable composition to the polymerizing radiation. Inventive Concept 170: The apparatus of Inventive Concept 169, comprising a motor operative to rotate the mold at a constant speed between 30 and 120 revolutions per minute. Inventive Concept 171: A fabrication system comprising a powered rotatable mold surrounding a cavity having a diameter of at least 50 mm, a source of polymerizing radiation, and a control system programmed to carry out the introducing, rotating and subjecting of any one of Inventive Concepts 158 to 168. Inventive Concept 172: An eyeglass lens blank fabricated using any one of the methods of Inventive Concepts 158 to 168. Inventive Concept 173: A system for use in fabricating an eyeglass lens blank from a radiation-polymerizable composition, the system comprising: (a) a rotatable mold surrounding a cavity having a diameter of at least 50 mm, the mold comprising a floor portion arranged for forming thereupon a first surface of the eyeglass lens blank and a peripheral wall portion having a minimum height at least 1 mm above a highest point of the floor portion; (b) an electric motor operative to rotate the mold at a constant speed between 30 and 120 revolutions per minute; and (c) a source of polymerizing radiation arrangeable to irradiate at least a portion of the polymerizable composition with said polymerizing radiation, wherein in a first operating mode of the system, when the mold is rotated at a speed between 30 and 120 revolutions per minute while a radiation-polymerizable composition having a viscosity between 20 and 2000 cP at ambient temperature is resident in said cavity, the radiation-polymerizable composition having a volume of between 0.25 and 0.35 cc per cm2 of cavity area, the rotating is effective to change a contour of an upper surface of the polymerizable composition to form a concave paraboloid shape. Inventive Concept 174: The system of Inventive Concept 173, additionally comprising electronic circuitry configured to regulate operation of at least one of the powered rotatable mold and the source of the polymerizing radiation in response to inputs received through a user interface, the inputs defining one or more shape and / or compositional parameters of the eyeglass lens blank. Inventive Concept 175: The system of Inventive Concept 174, wherein the electronic circuitry is configured to determine an operating parameter based at least in part on one or more of said inputs. Inventive Concept 176: The system of Inventive Concept 175, wherein the operating parameter includes at least one of: a rotation speed of the mold, the quantity of said radiation-polymerizable composition, and a rotation time for forming the paraboloid shape. Inventive Concept 177: The system of either one of Inventive Concept 175or 176, wherein the one or more inputs include at least one of: a diopter of the eyeglass lens blank, a refractive index of the radiation-polymerizable composition, and a diameter of the cavity of the mold. Inventive Concept 178: The system of any one of Inventive Concepts 174 to 177, wherein the electronic circuitry is programmed to initiate the irradiating of the polymerizable composition with the polymerizing radiation after a predetermined rotation time. Inventive Concept 179: The system of any one of Inventive Concepts 174 to 178, wherein the electronic circuitry is programmed to initiate the irradiating of the polymerizable composition with the polymerizing radiation in response to an input from a sensor. Inventive Concept 180: The system of any one of Inventive Concepts 173 to 179, additionally comprising a material supply assembly comprising one or more vessels storing the radiation-polymerizable composition, and a conveyance for supplying therethrough, to the rotatable mold, a quantity of said radiation-polymerizable composition. Inventive Concept 181: The system of any one of Inventive Concepts 173 5 to 180, additionally comprising any of the structural features of the above-provided Inventive Concepts. The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of 10 the invention. Some embodiments of the present invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments will occur to persons skilled in the art to which the invention pertains.

Claims

1. A method of fabricating an eyeglass lens blank, the method comprising:a. introducing a radiation-curable composition into a mold surrounding a cavity having a diameter of at least 50 mm, a floor portion of the mold being shaped for forming thereupon a first surface of the eyeglass lens;b. rotating the mold, at a speed of at least 30 rpm and not more than 120 rpm, about a center of rotation thereof to cause a portion of the radiation-curable composition to displace so as to change a contour of an upper surface of the curable composition to a concave paraboloid shape; andc. subjecting the curable composition to the curing radiation to solidify the composition.

2. The method of claim 1, wherein the solidified composition has a minimum thickness of at least 1 mm.

3. The method of either one of claims 1 or 2, wherein the solidified composition has an average thickness of at least 2 mm.

4. The method of any one of the preceding claims, wherein the introduced quantity has a volume of at least 6 cc.

5. The method of any one of the preceding claims, wherein the eyeglass lens blank comprises a single-vision lens blank.

6. The method of any one of the preceding claims, wherein the eyeglass lens blank comprises a finished lens blank.

7. The method of claim of any one of the preceding claims, additionally comprising: selecting the floor portion based on at least one of a diopter and a refractive index of the eyeglass lens blank, and installing the floor portion in the mold.

8. The method of any one of the preceding claims, wherein the floor portion is non-destructively separable from the mold.

9. The method of any one of claims 1 to 6, additionally comprising: selecting the mold based on at least one of a diopter and a refractive index of the eyeglass lens blank.

10. The method of any one of the preceding claims, wherein the subjecting of the polymerizable composition to the polymerizing radiation includes subjecting at least a portion of a lower surface of the polymerizable composition to the polymerizing radiation.

11. The method of any one of the preceding claims, wherein at least a portion of the subjecting of the polymerizable composition to the polymerizing radiation is carried out during the rotating.

12. An apparatus for use in carrying out the method of any one of the preceding claims, the apparatus comprising a powered rotatable mold surrounding a cavity having a diameter of at least 50 mm, and a source of polymerizing radiation arranged to subject the polymerizable composition to the polymerizing radiation.

13. The apparatus of claim 12, comprising a motor operative to rotate the mold at a constant speed between 30 and 120 revolutions per minute.

14. A fabrication system comprising a powered rotatable mold surrounding a cavity having a diameter of at least 50 mm, a source of polymerizing radiation, and a control system programmed to carry out the introducing, rotating and subjecting of any one of claims 1 to 11.

15. An eyeglass lens blank fabricated using any one of the methods of claims 1 to 11.

16. A system for use in fabricating an eyeglass lens blank from a radiation-polymerizable composition, the system comprising:a. a rotatable mold surrounding a cavity having a diameter of at least 50 mm, the mold comprising a floor portion arranged for forming thereupon a first surface of the eyeglass lens blank and a peripheral wall portion having a minimum height at least 1 mm above a highest point of the floor portion;b. an electric motor operative to rotate the mold at a constant speed between 30 and 120 revolutions per minute; andc. a source of polymerizing radiation arrangeable to irradiate at least a portion of the polymerizable composition with said polymerizing radiation,wherein in a first operating mode of the system, when the mold is rotated at a speed between 30 and 120 revolutions per minute while a radiation-polymerizable composition having a viscosity between 20 and 2000 cP at ambient temperature is resident in said cavity', the radiation-polymerizable composition having a volume of between 0.25 and 0.35 cc per cm2 of cavity area, the rotating is effective to change a contour of an upper surface of the polymerizable composition to form a concave paraboloid shape.

17. The system of claim 16, additionally comprising electronic circuitry configured to regulate operation of at least one of the powered rotatable mold and the source of the polymerizing radiation in response to inputs received through a user interface, the inputs defining one or more shape and / or compositional parameters of the eyeglass lens blank.

18. The system of claim 17, wherein the electronic circuitry is configured to determine an operating parameter based at least in part on one or more of said inputs.

19. The system of claim 18, wherein the operating parameter includes at least one of: a rotation speed of the mold, the quantity of said radiation-polymerizable composition, and a rotation time for forming the paraboloid shape.

20. The system of either one of claims 18 or 19, wherein the one or more inputs include at least one of: a diopter of the eyeglass lens blank, a refractive index of the radiation-polymerizable composition, and a diameter of the cavity of the mold.

21. The system of any one of claims 17 to 20, wherein the electronic circuitry is programmed to initiate the irradiating of the polymerizable composition with the polymerizing radiation after a predetermined rotation time.

22. The system of any one of claims 17 to 21, wherein the electronic circuitry is programmed to initiate the irradiating of the polymerizable composition with the polymerizing radiation in response to an input from a sensor.

23. The system of any one of claims 16 to 22, additionally comprising a material supply assembly comprising one or more vessels storing the radiation-polymerizable composition, and a conveyance for supplying therethrough, to the rotatable mold, a quantity' of said radiation-polymerizable composition.36

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