WO2012072916A1

WO2012072916A1 - Progressive ophthalmic lens element

Info

Publication number: WO2012072916A1
Application number: PCT/FR2011/052728
Authority: WO
Inventors: Sylvain Chene
Original assignee: Essilor International (Compagnie Generale D'optique)
Priority date: 2010-11-29
Filing date: 2011-11-22
Publication date: 2012-06-07
Also published as: FR2968095A1; FR2968095B1

Abstract

The invention relates to a method for designing an ophthalmic lens element (1), which uses a first complex and continuous surface over the entire element, and another complex and continuous surface inside side-by-side portions (2). The two surfaces are combined within the ophthalmic lens element. Further, the portions of said other surface include a common strip, wherein the involuntary astigmatism of said other surface may be low. The ophthalmic lens element thus has overall reduced involuntary astigmatism without causing discomfort to a wearer of said dynamic vision element.

Description

PROGRESSIVE OPHTHALMIC GLASS ELEMENT

The present invention relates to a method of designing a progressive ophthalmic lens element, as well as the element itself.

Progressive ophthalmic lenses, or optical spectacle lenses, have been known for a long time and are adapted to correct the sight of presbyopic carriers. A progressive lens has optical power values that vary between different directions of vision of the wearer through this lens. Thus, the correction of the view of the wearer is adapted according to the distance of an object that is viewed in a given direction. But these variations in the optical power of a progressive lens inherently produce involuntary variations in astigmatism, more simply called involuntary astigmatism in the jargon of those skilled in the art. Although progressive lenses are designed so that this involuntary astigmatism has low values in a central strip of the lens, the unintentional astigmatism values that are higher in the side portions of the lens can provide visual discomfort to the wearer. In fact, the involuntary astigmatism of a progressive lens is all the more important as the addition value of the glass is high.

The document FR 2 908 191, which is also in the name of the Applicant of the present patent application, proposes to produce a progressive ophthalmic lens reproducing with successive lateral offsets, the same complex and continuous surface strip which is substantially vertical by relative to the position of use of the glass. In other words, the glass consists of a succession of identical vertical bands, which are each the central part of an initial progressive lens, in which the involuntary astigmatism is the weakest. The central band of the glass which is thus constituted thus produces the same variations in optical power as the initial glass, especially along the meridian line, so that the strip glass and the initial glass have identical addition values. In addition, the unintentional astigmatism of the strip glass is limited by construction to the astigmatism values of the initial glass in the central strip. It is recalled that the line meridian of a glass of glasses means the trace of the intersection of the axis of the eye of the wearer with the front of the glass, when the wearer looks in front of him objects that are closer and closer to decreasing heights .

But such progressive striped glass has the following disadvantages. On the one hand, the glass has discontinuities between two adjacent strips, along lines of separation which are oriented substantially vertically. These discontinuities, which may correspond to jumps of sagittal height ("sag height" in English) of one of the faces of the glass, are visible and incompatible with the aesthetic requirements of the ophthalmic field.

On the other hand, these discontinuities between adjacent bands also affect the local prism values of the ophthalmic lens. They then cause image jumps for the wearer, when the direction of gaze of it passes a strip of the glass to an adjacent band. These image jumps have amplitudes that depend on the size of the discontinuities between adjacent bands, itself dependent on the width of the bands and the value of addition. For common addition values, of the order of 3 diopters for example, and strips of 2 mm (mm) wide, these image jumps are unpleasant and inconvenient for the wearer.

Under these conditions, the present invention aims to provide new progressive ophthalmic lenses for which the above disadvantages are reduced. More particularly, the invention combines the following improvements in a progressive ophthalmic lens, with respect to a progressive lens of the same addition value as known from the prior art:

- involuntary astigmatism values that are low;

- an aesthetic appearance that is satisfactory, with little visible discontinuities; and

image hops perceived by the wearer which are reduced.

For this, the present invention proposes a design method a progressive ophthalmic lens element, which element has optical power variations in a surface that is optically useful, and these optical power variations being continuous along at least one segment of a meridian line of the element the method comprising the following steps:

IM distributing the continuous variations in optical power along the segment of the meridian line between first and second continuous and non-zero contributions to these optical power variations;

121 obtaining first and second continuous and complex surfaces, and dioptrically producing respectively the first and second contributions to optical power variations along the segment of the meridian line, with the first continuous and complex surface that extends over the entire useful surface of the element;

/ 3 / in the second continuous and complex surface, select a band containing the segment of the meridian line, and reproduce portions of this second continuous and complex surface which all contain the band with successive offsets in a direction transverse to the meridian line, so as to form a third surface comprising the offset reproductions of the portions of the second surface, the third surface extending over the entire useful surface of the element and producing the second contribution to the optical power variations along the segment the meridian line; and

Combining the first and third surfaces within the ophthalmic lens element, so that the first and second contributions to the optical power variations, respectively of the first and third surfaces, together produce the optical power variations of the optical element. along the segment of the meridian line.

The invention therefore makes a compromise between a progressive lens whose optical power varies continuously over the entire useful surface of the glass, and a striped glass which are reproduced with successive lateral offsets. For this, the variations in optical power of a glass according to the invention result from the combined effects of two surfaces: the first surface which is continuous and complex over the entire glass, and an additional surface formed of vertical portions which all contain a single band of another continuous and complex surface, called second surface. In the context of the present invention, the term "complex surface" designates a surface that is continuous within a considered area, that is to say without a step or hole, with in addition to variations in curvatures that are defined and continuous in every point of this extent.

The method of the invention may further be continued by performing the following step:

15 / making the progressive ophthalmic lens element in accordance with the first and third surfaces which are combined in step IAI.

According to a preferred embodiment of the invention, the segment of the meridian line can extend at least between a far vision point and a near vision point of the progressive ophthalmic lens element defining a value. of adding said element. The first and second contributions to the variations of optical power along the segment of the meridian line can then respectively correspond to two addition contributions, which are each non-zero. These addition contributions thus participate together in the addition value of the progressive ophthalmic lens element, after the first and third surfaces have been combined in step IAI.

In addition, the second continuous and complex surface may have a channel in which the involuntary astigmatism of this second surface is minimal, and the band which is selected in step 13 / in the second surface may be superimposed on this channel. Even more preferably, the meridian line of the ophthalmic lens element may also be superimposed on the channel of the second surface within one of the portions thereof within the third surface, when of the combination of the first and third surfaces in step IAI.

According to a particular application of the invention to the adaptation of a progression length of the ophthalmic lens element, a sphere variation in the channel of the second continuous and complex surface can be adapted so that the progression length of the element is different from that of the first continuous and complex surface . Different combinations of the first and third surfaces can alternatively be used in step 141. In particular, two of these possible combination modes are as follows:

- Affect the first and third surfaces respectively to dioptric interfaces of the ophthalmic lens element which are different, and which are traversed successively by the same light rays participating in a use of the element by a carrier; or

adding the respective sagittal heights of the first and third surfaces so as to produce a composite surface, and then assigning this composite surface to a dioptric interface of the ophthalmic lens element.

The invention furthermore proposes a progressive ophthalmic lens element having, in an optically useful surface of this element, optical power variations which are continuous within portions juxtaposed in a direction transverse to a meridian line of element, and optical power discontinuities between two adjacent portions. In this progressive ophthalmic lens element, the variations in optical power comprise a combination of the following two contributions: a first contribution which is equivalent to a dioptric effect of a first complex and continuous surface over the entire useful surface of the element of ophthalmic glass; and

a second contribution which is equivalent to a dioptric effect of a discontinuous surface, comprising portions of a second surface which is itself complex and continuous, with the same band of this second surface which is contained in all the portions; containing at least one segment of the meridian line of the element of ophthalmic lens, and the portions of the second surface being each offset in the transverse direction to cover together the entire useful surface of the ophthalmic lens element.

These two contributions are each non-zero.

Thus, a progressive ophthalmic lens element according to the invention can be distinguished from other progressive lenses by separating a continuous contribution and a discontinuous contribution in its variations in optical power and involuntary astigmatism. The discontinuous contribution is then identical inside bands that are offset laterally relative to each other in a transverse direction of the element. As before, the two contributions to the optical power variations may correspond to respective non-zero contributions to the addition value of the progressive ophthalmic lens element.

In particular, such a progressive ophthalmic glass element can be obtained according to a method which is in accordance with the invention, as described above.

Other features and advantages of the present invention will emerge in the following description of nonlimiting exemplary embodiments, with reference to the appended drawings, in which:

- Figures 1a and 1b are two profile views of spectacle lenses to which the invention can be applied;

FIGS. 2a to 2c are front views of spectacle lenses according to the invention;

FIG. 3 is a block diagram of the steps of a method according to the invention;

FIG. 4a is a diagram comparing prismatic deviations of three progressive ophthalmic lenses according to the invention, with prismatic deviations of two glasses known before the invention; and

FIG. 4b corresponds to FIG. 4a, for a derivative of the prismatic deviations. For the sake of clarity, the dimensions of the elements which are shown in FIGS. 1a, 1b and 2a to 2c do not correspond to real dimensions nor to actual dimension ratios. In addition, identical references which are indicated in different figures designate identical elements or which have identical functions.

A progressive ophthalmic lens element which is in accordance with the present invention may comprise an ophthalmic lens itself, an insert which is intended to be incorporated in an ophthalmic lens, or a tablet which is intended to be applied against an optical surface of an ophthalmic lens. an ophthalmic lens.

It is indeed known to make an ophthalmic lens in the form of two components: an insert which is first manufactured, and which is then introduced into an injection mold of a residual portion of the glass. For this, the insert must be made of a material (s) which retains their initial shape at the injection temperature of the residual portion of the glass. In particular, the insert may constitute a first face of the ophthalmic lens, and the residual portion a second face of the lens. When the invention is applied to the insert, it is progressive type by itself producing optical power variations according to the invention.

It is also known to add an optical power modification patch to a glass of ophthalmic spectacles, to adapt the optical characteristics of the glass to a particular use. The glass is then used in combination with the pellet which is fixed on it. For this, the pellet has a shape and a composition which are adapted to conform to the face of the glass on which it is fixed. When the invention is applied to such an optical power modification chip, the chip is of the progressive type by itself producing optical power variations in accordance with the invention.

The invention is now described in detail in the case where the progressive ophthalmic lens element is an ophthalmic lens as such, that is, it can be assembled in a pair of spectacles to correct the sight of a wearer of these glasses. According to FIG. 1a, such an ophthalmic lens 1 is composed of a portion of refractive medium which is between two external faces of the glass, referenced 10 and 1 1. The refractive medium may be any material used in the ophthalmic field, in particular an inorganic, organic or hybrid material. The outer face 10 is convex and the outer face 1 1 is concave, and they respectively constitute the anterior face and the posterior face of the lens 1. The faces 10 and 11 each constitute an interface between the refractive medium and the external ambient medium, which is most often air. Between the faces 10 and 11, the glass 1 is limited by a peripheral edge B, which can be circular with a diameter of 60 mm (millimeter) or 65 mm.

Figure 1b shows another possible constitution of the ophthalmic lens 1, which has two components 1a and 1b. The two glass components 1a and 1b are portions of two different refractive materials, which are in contact with each other along an intermediate interface, referenced 12. Those skilled in the art will understand that the The invention can be applied to an ophthalmic lens that has any number of intermediate interfaces, in addition to its external faces, depending on the number of different components that make up the glass. In the following, we will designate by interface of the glass any of the outer faces of the glass and such intermediate interfaces. All these interfaces have dioptric properties, and are traversed successively by the same light rays that participate in a use of the ophthalmic lens by a wearer.

In a nonlimiting manner, but to illustrate the invention by numerical values of optical characteristics, it will be considered in the remainder of the present description that the value of the pantoscopic angle may be equal to 12 ° (degree) of inclination of the glass. forward and down around a horizontal axis.

Ophthalmic glass is then characterized by an optical power distribution and an involuntary astigmatism distribution, which associate optical power values and involuntary astigmatism with each view direction of the wearer through the glass. A progressive lens as considered in the present invention is indicated by a mounting cross, which can be inscribed on the glass itself, or whose position can be identified precisely from a leaflet which is supplied with the glass. . This mounting cross determines the main viewing direction through the glass. This main direction is intended to correspond to the direction of horizontal gaze of the wearer, when the latter is sitting or standing. Any direction of vision through the glass is then defined by the line that passes through the center of rotation of the eye of the wearer equipped with the glass, and by a point on the anterior face of the glass. For this, it will be assumed in the following that the center of rotation of the eye is located behind the glass on the main viewing direction, at a reference distance equal to 27 mm (mm) behind the rear face of the glass. From there, any direction of vision through the lens can be identified by a pitch angle and an azimuth angle, which are measured respectively in a vertical plane and a horizontal plane from the main viewing direction to through the glass. Commonly, the angle of elevation, denoted a, is positively counted towards the bottom of the glass, and the azimuth angle, denoted β, is positively counted towards the nasal side of the glass.

A progressive ophthalmic lens has two different optical power values, respectively for a far vision direction and for a near vision direction. The direction of vision from a distance (respectively direction of near vision) passes through the center of rotation of the eye and a point of the anterior face of the glass which is called point of vision from a distance (or near) and noted VL (resp VP) in Figures 1a and 1b. The optical power value for near vision is greater than for far vision, and their difference is called addition. This addition is intended to compensate for a lack of accommodation of the eye of the wearer, when he successively looks at objects that are more and more close to him. The optical power value for the far vision direction is adapted for the wearer to clearly see an object that is more than two meters away from him. That for the direction of near vision can be adapted so that the wearer clearly sees an object that is located forty centimeters away from him. For example, the height angle can be -8 ° for the far vision direction, and + 23 ° for the near-vision direction.

A meridian line is further defined on the front side of the lens, which connects the points of intersection of the viewing directions through the lens as the wearer looks ahead at varying heights. This meridian line thus passes successively, from the top to the bottom of the glass, by the point of vision from afar, the mounting cross then the point of near vision. It is noted LM in Figures 2a to 2c. In general, the meridian line can be deflected horizontally in a lower part of the glass towards the nasal side. The variation in the optical power of the glass between the far and near vision directions, along the meridian line LM, is continuous for a progressive lens, but it can have a variation profile that varies from a progressive lens to another. In addition, the length along the meridian line, on which these variations are produced, is called the length of progression and may also vary.

Finally, a progressive type of ophthalmic lens is usually designed to have unintentional astigmatism values which are lowest in a central part of the glass comprising the meridian line. It is recalled that involuntary astigmatism is distinct from a prescribed value of astigmatism which is produced voluntarily and uniformly throughout the entire range of the glass, to compensate for a defect of astigmatism of the wearer's eye. The involuntary astigmatism of the glass, which is harmful to the wearer, is pushed back into the lateral parts of the glass, on each side of the meridian line. In this way, a central strip of glass that includes the meridian line provides the wearer a vision substantially free of involuntary astigmatism. This central band is commonly called progressive glass channel. It can be limited on each side by two iso-astigmatism curves corresponding to the value of involuntary astigmatism of 0.5 diopters, for example. In addition, the channel is laterally deflected in the lower part of the glass according to the meridian line.

Mapping of optical power and astigmatism of the same Progressive ophthalmic lens according to the invention have a common partitioned structure, consisting of portions that are substantially parallel to the meridian line. Variations in optical power and astigmatism are continuous within each portion, and have discontinuities between two adjacent portions. Figures 2a to 2c show several partitioned structures that are compatible with the invention.

Such a partitioned structure can be obtained as follows, with reference to FIG.

In a first step referenced S1a and S1b, two complex surfaces are selected. They are therefore continuous. The first of these two complex surfaces is large enough to cover the entire useful surface of the progressive lens to be manufactured. The other complex surface, called the second complex surface, contains at least one strip extending from the lower part of the peripheral edge B of the glass to be produced, to the upper part of this edge B.

Since the final progressive lens is sought to have low involuntary astigmatism values, the first surface preferably preferably itself has an involuntary astigmatism which is limited over the entire useful surface of the lens, and the second surface advantageously has an involuntary astigmatism that is low in the band considered. In fact, the first and second surfaces may each be a progressive surface with a respective channel in which the involuntary astigmatism is minimal. The strip in the second surface then contains a portion of the channel thereof (Figures 2a and 2b), or all (Figure 2c). Optionally, when the channel of the second surface is deflected, like a meridian line of progressive glass, the second surface band may have a shape that follows this deviation. The band which is selected in the second surface (step S2) can thus contain all the channel of this second surface. Thus, involuntary astigmatism has only low values in the second surface band.

A method of obtaining the second surface is now described by way of example. The first complex surface can be that of a first initial progressive ophthalmic lens with a single complex surface, this first progressive lens being characterized in particular by an addition value, a progression length and a progression profile along its meridian line. It is recalled that the progression length is the angular distance between two directions of gaze of the wearer passing through the meridian line, for which the optical power deviations are respectively 5% and 85% relative to the optical power value of the glass for the direction of vision from afar. The unique complex surface of the first initial lens also determines its design, that is, the distribution of optical power and unintentional astigmatism variations across the optically useful surface of the first lens. The second complex surface which is used in the invention can be deduced from a second initial progressive ophthalmic lens, the design of which is also produced by a single complex surface of this second lens. More particularly, the second surface may result from a difference in sagittal heights between the complex surfaces of the first and second progressive lenses. The ophthalmic glass element which is obtained using the invention may then have an addition value, and / or a progression length and / or a progression profile along its meridian line which is / are the of the second progressive progressive lens. In other words, the invention makes it possible to obtain from the complex surface of the first initial progressive lens a new progressive lens which has characteristics of the initial progressive second lens.

In particular, the two initial progressive ophthalmic lenses that are used to obtain the first and second surfaces implemented in the method of the invention may have respective designs that are identical but respective addition values that are different. The invention then makes it possible to obtain, from the surface of the first initial progressive lens, a new progressive ophthalmic lens element with a design substantially identical to that of the initial initial lens, but which possesses the addition of this first augmented lens. an addition increment equal to the difference between the addition values of the first and second initial glasses used. By successively taking second initial glasses which have increasing addition values with identical designs, the invention allows to obtain several addition values from the design of the first initial glass.

Conversely, the second surface can be constant corresponding to a determined addition increment, for example equal to 0.5 diopter, and the first initial glass can be varied while keeping a constant design to have first values of different additions, for example integers. The invention then makes it possible to complete the range of the initial initial glasses by additional progressive glasses which have intermediate addition values.

A third surface is then reconstructed from the second surface, by juxtaposing portions of the second surface each containing the selected band (step S3). The number of second surface portions and their shapes are selected so that the third surface covers the entire useful surface of the progressive glass to be produced, without interstice or superposition between neighboring portions. Figures 2a to 2c show such possible partitions of the glass, defined by the third surface. Optionally, some of the portions that are cut in the second surface around the channel thereof may be deformed and / or laterally deflected to coincide the respective edges of portions that are adjacent in the third surface. This may be the case for Figure 2b, to obtain portions that are curved differently by containing all the same second surface band.

In this way, the third surface has involuntary astigmatism values which are small within each portion, but which are discontinuous at the boundary between two adjacent portions.

The first and third surfaces are then combined within the progressive lens to be manufactured (step S4). Conveniently, the first and third surfaces are numerically defined in respective computer files, and the glass is digitally simulated from these files. The first and third surfaces are thus combined with an alignment of one with respect to the other. This alignment consists in selecting a rotation orientation of one of the surfaces relative to the other, as well as a shift in translation, parallel to the two surfaces. According to a first mode of combination of the first surface, which is complex and continuous, with the third surface, which is discontinuous, these two surfaces form two dioptric interfaces of the glass which are different. For example, the first surface may be assigned to the anterior outer face 10, and the third surface may be assigned to the posterior outer face 11 (Figure 1a), or vice versa. Alternatively, the third surface can be assigned to the intermediate interface 12, while the first surface can still be assigned to the outer front surface 10 (Figure 1b).

According to a second method of combining the first and third surfaces in the glass to be manufactured, these two surfaces are added to form a resulting composite surface. Such a surface addition operation is well known to those skilled in the art, so that it is now recalled only briefly. The first and third surfaces are each defined by their respective sagittal heights, with respect to a reference surface and a mesh that is established in this reference surface. For each node of the mesh, the sagittal height of the first surface is added to that of the third surface, for the same node of the mesh, and the result of the sum constitutes the sagittal height of the composite surface with respect to this node of the mesh. reference surface. Optionally, the addition of the sagittal heights can be performed with two linear combination coefficients, which are constant and assigned respectively to the first and third surfaces. The composite surface that is thus obtained can then form one of the dioptric interfaces of the glass.

Finally, the progressive lens can be manufactured (step S5) according to its numerical simulation, in particular by using one of the known methods for producing ophthalmic lenses. Among these methods, the following can in particular be used: direct machining, molding, hot embossing, embossing with UV irradiation, photolithography, direct laser lithography, etc. For these methods, the interface or the dioptric interfaces of the glass which are concerned by the invention are produced by varying the curvature along this interface or interfaces.

In alternative methods, the third surface can be formed by a variable refractive index layer, that is to say whose values of the refractive index may be different for separate points in the third surface. The variations in optical power and involuntary astigmatism of the dioptric interface are then made by variations in the refractive index of this layer which forms the dioptric interface. The layer then has, between two portions of the second surface which are adjacent within the third discontinuous surface, jumps in value of at least one parameter among the refractive index, and a derivative of order one or two of this refractive index, these derivatives being calculated with respect to at least one coordinate along an axis parallel to the layer. Such an embodiment is applicable when the first and third surfaces are assigned to dioptric glass interfaces which are distinct, but also when they are combined within the single composite surface. In the latter case, the third surface is formed by the dioptric interface of the glass which is constituted by the variable index layer, as a component of the composite surface. The adjustment of the refractive index of the layer can be carried out continuously along the interface concerned, or else by discrete values at the points of a sampling network which is defined on this interface. Methods for adjusting the refractive index of such a layer are known to those skilled in the art, so that they are not repeated here.

The optical characteristics of a progressive ophthalmic lens which has been obtained in one of the ways just described, result from the corresponding characteristics of the first complex and continuous surface on the one hand, and those of the third discontinuous surface. that is, the second complex surface and continues within portions thereof that have been selected. In particular, the variations in optical power and involuntary astigmatism of the glass result from the corresponding variations that are produced by the first surface and the third surface.

Since progressive glass is designed to produce a prescribed addition value, this addition value results from a first addition contribution that is produced by the first surface, and a second addition contribution that is produced by the third surface. Thus, the steps S1a and S2a comprise a distribution of the addition value of the glass to be made between the respective addition contributions of the first surface and the third surface.

In known manner, the first surface being complex and continuous over the entire useful surface of the glass, it has at certain points involuntary astigmatism values which are higher than the contribution of this first surface to the addition value. glass is important. The invention then makes it possible to select this first surface with an addition contribution which is lower than the addition value of the glass. Thus, the involuntary astigmatism that is produced by the first surface is less than that which would be produced if all the value of addition of the glass was produced by the first surface. The second surface is then selected to produce a complementary addition contribution, so that the two surfaces together produce, by their respective contributions, the addition value of the glass.

But the discontinuities of the optical characteristics of the glass, between adjacent portions in the third surface, have amplitudes all the more important that these portions are wider. The widths of the portions are measured along a transverse direction T of the progressive lens, that is to say in particular transversely with respect to its meridian line LM. In particular, the prismatic deviation of the glass has ruptures of slope which disturb the dynamic vision of the glass wearer. For this reason, it is preferable that the portions of the second continuous surface that are used to form the third discontinuous surface have widths that are smaller than a maximum value. On the other hand, widths of surface portions which are too small cause glass production difficulties, to achieve discontinuities that are precise and separate while being very close. Thus, it is advantageous that the second surface portions have widths that are between 2 mm (mm) and 15 mm, preferably between 4 and 10 mm, in the transverse direction T.

Optionally, the widths of the portions of the second continuous and complex surface may be adapted for the future carrier of the glass, according to its sensitivity to image jumps in dynamic vision. In other words, these portion widths can be selected so that image jumps between two adjacent portions in the third surface have magnitudes that are less than a determined image jump limit for the wearer.

For the same reason, the involuntary astigmatism of the third surface has boundary discontinuities between the second surface portions. To reduce the amplitudes of these discontinuities which could also cause discomfort for the dynamic vision of the wearer, the widths of the second surface portions, measured in the transverse direction T, can be selected so that each of these portions has at all points a Residual astigmatism that is less than or equal to 0.1 diopter.

When the first and third surfaces both contribute to the addition, i.e. their respective addition contributions are non-zero, the addition contribution of the third surface is preferably greater than or equal to 0.25 diopters, and less than or equal to 25% of the addition value of the ophthalmic lens element. Such an interval for the values of the addition contribution of the third surface, said second contribution in the general part of the description of the invention, contributes to ensuring that the involuntary astigmatism values of the third surface are low.

To illustrate the invention, five progressive ophthalmic lenses are now compared, whose addition values are identical, equal to 2.00 diopters, and the optical power values for the far vision direction are also identical, equal to 4 diopters. The five glasses have far and near vision points, as well as respective meridian lines, which are located in the same way with respect to the mounting cross. Three of these glasses were made in accordance with the invention, with the following first and second addition contributions, which are respectively produced by the first continuous surface and the third portioned area: first contribution second contribution

addition (diopter) addition (diopter)

Glass 1 1, 75 0.25

Glass 2 1, 50 0.50

Glass 3 1, 25 0.75

Table 1

The following two progressive ophthalmic lenses, known earlier, are given for comparison:

Table 2 The progressive lens 0 is of the type with a single progressive continuous surface. Its other dioptric interface (s) is (are) spherical (s) or toric (s). The glass 4 is made in accordance with the teaching of document FR 2 908 191, with a portioned surface which produces the entire addition of the glass, its other dioptric interface (s) being still spherical ( s) or toric (s). For the glasses 1 to 4, all the portions of the third surface have a common width of 2.5 mm.

The diagram of FIG. 4a reproduces the prismatic deviations of the glasses 0 to 4, for directions of vision through the glasses corresponding to the constant value of 35 ° for the angle of height a, and for angle values of azimuth β which are between -30 ° and + 30 °. For the sake of simplicity, the direction of vision closely through these glasses corresponds to a = + 35 ° and β = 0. The diagram of Figure 4b shows the variations of the derivatives of the prismatic deviations from the azimuth angle β, again for a = + 35 ° and for the five glasses 0 to 4. The discontinuities of the derivative of the prismatic deflection, which disturb the dynamic vision of the wearer, are the most important for the glass 4. Their amplitudes for the glasses 1 to 3 are much weaker, so that they become almost imperceptible to the wearer and do not cause him visual discomfort.

The following table gives the maximum values of unintentional astigmatism of glasses 0 to 4, measured inside a 40 mm disc in each lens, as well as the widths of near vision zones. The near vision zone width is defined for each lens as the difference between the values of the azimuth angle β for which the involuntary astigmatism is equal to 0.5 diopter, again for a = + 35 °.

Table 3

The width of the near vision zone of the lens 4 can not be determined because the involuntary astigmatism is less than 0.5 diopter over the entire width of the lens for the height of the near vision direction.

Thus, the glasses 1 to 3, according to the invention, generally have an involuntary astigmatism which is reduced and a near vision zone which is wider, compared with the glass 0. They constitute an advantageous compromise between the two glasses. 0 and 4 known before the present invention.

Compared to a realization of progressive lenses which is in accordance with the document FR 2 908 191, identical addition and identical maximum amplitude of the discontinuities of the prismatic deflection between two adjacent portions, the invention makes it possible to increase the width of the portions. The number of transitions between adjacent portions is then decreased, which reduces the inconvenience that these transitions could cause to the wearer. In addition, the invention improves the aesthetic appearance of the glasses, by reducing the number of visible boundaries between adjacent portions.

The complementary aspects which are mentioned now relate more particularly to the use of the invention for producing optical power modification pellets intended to be applied to base glasses.

It may be advantageous for these pellets to have a flat face. They can then be applied without being deformed on base glasses which also have a flat face. Most often, the flat surface of these basic glasses will be their anterior face. A single pellet can then be easily used with base glasses that have different optical power values for the far vision direction.

Sets of optical power modification pellets which are in accordance with the invention, with increasing addition values, can then be designed in different ways:

for a determined design of progressive surfaces, in particular for a determined profile of variation of the optical power along the meridian line, which is common to the progressive base glass and to the pellet. The use of such a pellet makes it possible to select a base glass with an addition value which is less than the value of addition prescribed for the wearer. The pellet is then selected to produce the addition complement between the value of the base glass and the prescribed value. The involuntary astigmatism of the entire base glass with the pellet is then less than that of a single base glass which would have the same progressive surface design and the addition value prescribed for the wearer;

a series of pellets indexed by the distance between the mounting cross and the near vision direction, in addition to the addition value of the pellets. Such pellets can then be associated with progressive base lenses that have different designs, depending on the length of progression of each design.

It is also possible to design pellets according to the invention which have a value of zero addition but nevertheless have variations in the optical power between the directions of vision from far and near. Such a pellet, when associated with a progressive base glass, can change the variation profile of the total optical power between the far and near vision directions. For example, they can increase or decrease the length of the segment of the meridian line in which the optical power varies from 5% to 95% of the prescribed addition value. Thus, a progressive, long-progressing lens can be converted into a progressive lens with a shorter progression length, having a maximum value of involuntary astigmatism, and values of astigmatism gradients which are lower than those of a lens progressive that would have the short progression length.

Finally, it is understood that the invention may be reproduced by introducing modifications with respect to the particular embodiments which have been described, while retaining at least some of the advantages mentioned. In particular, a uniform curvature and / or a toric component that are uniform can be added to the first surface and the third surface that are used in the invention. In addition, the second surface band which is common to the portions which constitute the third surface may not be parallel to the meridian line of the second surface or that of the ophthalmic glass element, and / or contain only one limited segment of these. In addition, the second surface portions which constitute the third surface may have respective widths in the transverse direction T of the ophthalmic glass element which vary between different portions for the same element. For example, the portions that are located on the sides of the element may be narrower than those that are closer to its center. At the same time, the width of each portion may vary along a direction that connects the top and bottom of the ophthalmic lens element.

Claims

1. A method of designing a progressive ophthalmic lens element (1), the element having optical power variations in an optically useful surface of said element, and said variations being continuous along at least one segment of a meridian line (LM) of the element, the method comprising the steps of:

IM distributing the continuous variations of optical power along the segment of the meridian line (LM) between first and second DC and non-zero contributions to said optical power variations;

121 obtaining first and second continuous and complex surfaces, and dioptrically producing respectively the first and second contributions to the optical power variations along the segment of the meridian line (LM), said first continuous and complex surface extending over any the effective area of the element;

/ 3 / in the second continuous and complex surface, select a band containing the segment of the meridian line (LM), and reproduce portions (2) of the second continuous and complex surface containing all of said band with successive offsets in one direction (T) transverse to the meridian line, so as to form a third surface comprising offset reproductions of the portions of the second surface, said third surface extending over the entire useful surface of the element (1) and producing the second contribution to optical power variations along the segment of the meridian line; and

Combining the first and third surfaces within the ophthalmic lens element (1), so that the first and second contributions to the optical power variations, respectively of the first and third surfaces, together produce the variations in the optical power of the element along the meridional line (LM) segment.

The method of claim 1, further comprising the step of:

15 / performing the progressive ophthalmic lens element (1) according to the first and third surfaces combined in step IAI.

The method of claim 1 or 2, wherein the segment of the meridian line (LM) extends at least between a far vision point (VL) and a near vision point (VP) of the element progressive ophthalmic lens (1) defining an addition value of said element, and wherein the first and second contributions to the optical power variations along said meridional line (LM) segment respectively correspond to two addition contributions, said two addition contributions being each non-zero and participating together in the addition value of the progressive ophthalmic lens element (1) after said first and third surfaces have been combined in step IAI.

A. Process according to claim 3, wherein the addition contribution produced by the third surface is greater than or equal to 0.25 diopters and less than or equal to 25% of the addition value of the ophthalmic glass element. .

A method according to any one of the preceding claims, wherein the second continuous and complex surface has a channel in which the involuntary astigmatism of said second surface is minimal, and wherein the band which is selected in step / 3 / is superimposed on this channel.

6. A method according to claim 5, wherein the meridian line (LM) of the ophthalmic glass element (1) is also superimposed on the channel of the second surface inside one of the portions (2) of said second surface within the third surface, when combining the first and third surfaces in step IAI.

The method according to claim 5 or 6, wherein a sphere variation in the channel of the second continuous and complex surface is adapted so that a progression length of the ophthalmic lens element is different from a length of progression of the first continuous and complex surface.

8. A method according to any one of claims 1 to 7, wherein step 141 is performed by assigning the first and third surfaces respectively to different dioptric interfaces of the ophthalmic glass element (1), traversed successively by same light rays that participate in a use of said ophthalmic lens element by a wearer.

The method of any one of claims 1 to 7, wherein step 141 is performed by summing respective sagittal heights of the first and third surfaces to produce a composite surface, and then assigning said composite surface to an interface diopter of the ophthalmic glass element.

10. A method according to any one of the preceding claims, wherein the ophthalmic glass element (1) is selected from the list comprising an ophthalmic lens, an insert for incorporation into an ophthalmic lens, and a patch intended to be applied against an optic face of an ophthalmic lens.

1 1. A method according to any one of the preceding claims, wherein widths of the portions (2) of the second continuous and complex surface reproduced in step 131, measured in the transverse direction (T), are selected so that each of said Portions of the second surface have residual astigmatism at all points less than or equal to 0.1 diopters.

12. Method according to any one of the preceding claims, wherein widths of the portions (2) of the second continuous and complex surface reproduced in step 131, measured in the transverse direction. (T), are selected so that image breaks between two adjacent portions in the third surface have magnitudes below a determined image jump limit for the wearer.

13. Progressive ophthalmic lens element (1) having, in an optically useful surface of the element, continuous optical power variations inside portions juxtaposed in a direction (T) transverse to a meridian line (LM) ) of said element, and optical power discontinuities between two adjacent portions, wherein the optical power variations comprise a combination of a first and a second non-zero each;

the first contribution being equivalent to a dioptric effect of a first complex and continuous surface over the entire useful surface of the ophthalmic lens element; and

the second contribution being equivalent to a dioptric effect of a discontinuous surface, comprising portions (2) of a second surface itself complex and continuous, with the same band of said second surface which is contained in all the portions, said a strip containing at least one segment of the meridian line (LM) of the ophthalmic lens element (1), and the portions of the second surface being each offset in the transverse direction (T) to cover together the entire useful surface of the ophthalmic glass element.

The progressive ophthalmic lens element (1) according to claim 13, wherein the segment of the meridian line (LM) contained in the band of the second surface extends at least between a far vision point (VL) and a near vision point (VP) of the progressive ophthalmic lens element defining an addition value of said element, and wherein the first contribution to the optical power variations of said element produces a first contribution to the value of addition of the element, and the second contribution to the optical power variations of said element produces a second contribution to the addition value of the element, said first and second addition contributions being each non-zero and participating together at an addition value of the ophthalmic lens element defined along the meridian line (LM).

The progressive ophthalmic lens element (1) according to claim 14, wherein the second contribution to the addition value of the ophthalmic lens element, produced by the discontinuous surface, is greater than or equal to 0.25 diopters, and less than or equal to 25% of the addition value of the ophthalmic lens element.

16. A progressive ophthalmic lens element (1) according to any one of claims 13 to 15, wherein the first continuous complex surface and the discontinuous surface respectively form two dioptric interfaces different from the ophthalmic glass element, crossed successively by same light rays that participate in a use of said ophthalmic lens element by a wearer.

The progressive ophthalmic lens element (1) according to any one of claims 13 to 15, comprising at least one dioptric interface formed by a composite surface, said composite surface corresponding to an addition of respective sagittal heights of the first complex surface and continuous and discontinuous surface.

18. Progressive ophthalmic lens element (1) according to any one of claims 13 to 17, forming an ophthalmic lens, an insert intended to be incorporated in an ophthalmic lens, or a pellet intended to be applied against an optical surface of an ophthalmic lens.

A progressive ophthalmic lens element (1) according to any of claims 13 to 18, wherein the second surface portions (2) have respective widths adapted so that each of said second surface portions has a total of point residual astigmatism less than or equal to 0.1 diopter.