The invention concerns a vacuum-coating system for coating lenses.
It is known to produce lenses using a casting process in which a monomer is poured into a cavity bounded by two mold shells and a seal and cured, for example, by UV radiation. During curing, the monomer is polymerized and the lens is formed. The seal is then removed and the lens is separated from the two mold shells. Such manufacturing processes are known for example from EP 15202 and WO 02/087861. Also known is the production of lenses by grinding from a blank. The lens can then be provided with optical layers in immersion baths or in a vacuum coating system, e.g. with anti-reflective layers, a scratch protection layer, etc.
Such a lens is a semi-finished product from which later, for example, a lens is cut out and fitted into a frame by an optician. Such lenses are also called ophthalmic lenses.
The invention is based on the object to provide a vacuum coating system for the coating of lenses, which produces layers with a homogeneous refractive index and a uniform thickness.
The above mentioned object is solved according to the invention by the features of claim 1. Advantageous embodiments result from the dependent claims.
The invention concerns a vacuum-coating system for the simultaneous coating of several lenses. The vacuum-coating system comprising a vacuum chamber, in which a number N of lens holders and an equal number N of electrodes are arranged so that a separate electrode is assigned to each lens. The lens and the electrode are located opposite each other. According to the invention, the surface of the electrode facing the lens is a curved surface. The curved surface comprises an inner area and an outer area, which can be adjacent or separated from each other by intermediate areas. The curvature of the surface in the outer area is at least equal, but preferably greater than in the inner area.
The surface of the electrode(s) may have an inner area and a plurality of circular rings adjacent thereto which extend concentrically to an axis of symmetry of the electrode, wherein a curvature of the surface of the electrode(s) increases in discrete steps or continuously from the centre outwards from circular ring to circular ring, wherein the outermost circular ring may but need not extend to the edge of the electrode.
Preferably, the distance between the electrode and the oppositely located lens can be adjusted.
The vacuum-coating system can be in particular a PECVD or PACVD system.
In this context, a distinction is made between two types of lenses, namely minus lenses and plus lenses. The minus lens is a lens that is thinnest in the middle and whose thickness increases continuously towards the edge. The plus lens is a lens that is thickest in the middle and whose thickness continuously decreases towards the edge.
The parts of the vacuum-coating system required for understanding the invention are explained in more detail below by means of exemplary embodiments and the drawing. For reasons of clarity of the drawings, the figures are not drawn to scale.
The first aspect of the invention concerns the curvature of the electrodes. This is explained using
The electrode 10 has a concave surface 13, the concave surface 13 can but does not have to extend to the edge of the electrode 10. The convex surface 4 of the lenses 11 and 12 faces the concave surface 13 of the electrode 10. The lens 11 is a minus lens. The lens 12 is a plus lens.
The formation of the electrodes 1 and 10 with curved surfaces 6 or 13, respectively, in which the curvature in an outer area 8 of the surface 6 or 13, respectively, is greater than in an inner area 9 of the surface 6 or 13, results in the distance between the electrode and the opposite lens being greater where the lens is thin and smaller where the lens is thick. In addition, the distance between the electrode and the opposite lens is adjustable. This makes it possible to set an optimum distance D for each lens. The optimum distance D for each lens is determined once in advance experimentally or using a computer program programmed for this purpose.
With only two different types of electrodes, namely electrodes 1 with a same convex surface 6 and electrodes 10 with a same concave surface 13, a large number of lenses of different geometry and thickness can be coated with layers with desired optical properties if the convex surface 6 or the concave surface 13 has a curved surface design that takes into account the variety of different lens geometries. The formation of the surface of the electrodes with a predetermined, optimised course of curvature and the individually optimisable adjustment of the distance between the lens and the electrode lead to the result that the refractive index and the thickness of the applied layer(s) seen both with the individual lenses and across all lenses which are coated in the same process in the vacuum chamber have a greater homogeneity and uniformity than could be achieved without this specific formation of the surface 6 or 13 of the electrodes 1 or 10 and without the adjustability of said distance.
It should be noted that the lenses produced are semi-finished products and that an optical element, such as a spectacle lens, for example, is cut out of the lens during further processing. For this reason, an area adjacent to the edge of the electrodes 1, 10 does not have to meet the above conditions, as the opposite lying area of the lens becomes waste anyway. This means that the mentioned outer area 8 of the surface 6 or 13 of the electrode 1 or 10 can extend to the edge of the electrode 1 or 10, but does not have to.
The threads of the recesses 15 of the electrode holder 14 are advantageously designed with markings so that the electrodes 16 can be set to certain rotational positions. Each rotational position corresponds to a different height of the electrode 16. A rotation of the electrode 16 from one rotating position to the next causes a predetermined change of the height and thus of the distance between the electrode 16 and the lens 19 held by the associated lens holder 17. With this construction, the distance between electrode 16 and lens 19 can be set with high accuracy, whereby the distance to be set or the rotational position to be set for each lens results from the corresponding lens recipe. The lenses 19 are placed in the lens holders 17 by a robot or the operator and the height of each electrode 16 is adjusted by the robot or the operator according to the corresponding lens recipe. Then the lens holder receptacle 18 is placed on the electrode holder 14 and the whole brought into the vacuum-coating system's vacuum chamber for coating.
The three lenses 19 shown in
Possible vacuum coating processes are CVD (chemical vapor deposition) processes, in particular PECVD (plasma-enhanced chemical vapor deposition) processes and PACVD (plasma-assisted chemical vapor deposition) processes. This list is not exhaustive.
The inner wall of the vacuum chamber is electrically conductive and usually electrically earthed. It thus represents a counter electrode which is electrically insulated from the electrode holder 14 and the electrodes.
While embodiments of this invention have been shown and described, it would be apparent to those skilled in the art that more modifications than mentioned above are possible without departing from the inventive concept. The invention, therefore, is only restricted by the appended claims.
Number | Date | Country | Kind |
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01896/15 | Dec 2015 | CH | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2016/081787 | 12/19/2016 | WO | 00 |