Abstract:
In one aspect, the invention is directed to a multifocal ophthalmic lens having a first region having first focal properties, and a second region having second focal properties and including a progressive region. The second region may further include, for example, a portion that is a reading region. The second region has two side edges and there are first and second transition regions between the first region and the side edges of the second region. The transition regions each have a width that is less than a selected width. This gives the lens designer more freedom to provide a wider second region without extending into lower left and lower right regions of the lens.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/537,669, filed Sep. 22, 2011, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     In some aspects, the present invention relates to multi-focal lenses and more particularly to progressive lenses. 
     BACKGROUND 
     Multi-focal lenses are well known. The lenses typically include upper regions designed to improve long-distance vision, and lower regions designed to improve intermediate and short distance vision. Such lenses typically have a significant amount of distortion associated with them, particularly in regions of the lens that can cause visual difficulties for the wearer. Additionally, such lenses typically have relatively small reading regions, rendering them difficult to use for reading. 
     It would be advantageous to provide a lens that at least somewhat addresses one or more of these problems. 
     Furthermore, it would be advantageous to be able to provide a lens that has at least somewhat less distortion but that is also tailored to permit the wearer to perform a particular task. 
     SUMMARY 
     In one aspect, the invention is directed to a multifocal ophthalmic lens having a first region having first focal properties, and a second region having second focal properties and including a progressive region. The second region may further include, for example, a portion that is a reading region. The second region has two side edges and there are first and second transition regions between the first region and the side edges of the second region. The transition regions each have a width that is less than a selected width. This gives the lens designer more freedom to provide a wider second region without extending into lower left and lower right regions of the lens. 
     Optionally, the lens may further include a third region having third focal properties and including a second progressive region. The third region includes a long-distance viewing portion having a third focal distance that is longer than the first focal distance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is made to the attached drawings, in which: 
         FIG. 1  is a perspective view of a multifocal ophthalmic lens in accordance with an embodiment of the present invention; 
         FIG. 2  is a magnified sectional view of a variant of the lens shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of a multifocal ophthalmic lens in accordance with another embodiment of the present invention; and 
         FIG. 4  is an elevation view of a multifocal ophthalmic lens in accordance with the prior art. 
     
    
    
     DETAILED DESCRIPTION 
     Reference is made to  FIG. 4 , which shows a lens  80  in accordance with the prior art. The lens  80  may be a progressive lens, such that it has a long-distance focus region  82 , and a second region  83 , which may include a progressive region and a short-distance focus region (for use when reading). In such a lens, the traditional approach to transitioning between the second region  83  and the long-distance region  82  has been to blend gradually. The transition regions that result from this design methodology can be seen as shaded areas  88  and  90  in  FIG. 4 . These transition regions  88  and  90  unfortunately are areas of distortion in the lens  80 , and it can be seen that these regions  88  and  90  occupy a significant region of the swept area of the lens  80 . In particular, a result of this design methodology, there is distortion in lower left and lower right regions of the lens  80 , which are shown at  92  and  94  respectively. The distortion in these regions  92  and  94  in particular can cause visual difficulty for the wearer of the lens  80 . For some wearers, this visual difficulty might cause discomfort and headaches. 
     Reference is first made to  FIG. 1 , which shows a multifocal lens  10  made in accordance with an embodiment of the present invention. The lens  10  is for use in eyewear, such as eyeglasses or monocles and the like, providing the wearer with improved vision at selected ranges of focal distance, with little distortion. 
     The lens  10  comprises a first region  12 , which has first focal properties and a second region  14  which has second focal properties. In the particular lens shown, the first focal properties are substantially constant throughout the first region. The first region  12  may, for example, be configured for focus at long-distance. 
     The second focal properties (i.e. the focal properties of the second region  14 ) may vary. More particularly, the second region  14  includes a portion that is a progressive region  14   a  and portion that is a short-distance focus region  14   b  (which may be referred to as a reading region  14   b ). The reading region  14   b  has an associated focal distance that is suitable for reading, such as, for example, approximately 12 inches, although other focal distances are alternatively possible. The progressive region  14   a  has associated therewith a focal distance that varies progressively between the focal distance of the reading region  14   b  and the focal distance of the first lens region  12 . It will be noted that there is no discontinuity in the lens  10  at the upper and lower limits of the progressive region; the lens surface at the upper end of the progressive region  14   a  transitions smoothly from the surface of the first region  12 , and the lens surface at the lower end of the progressive region  14   a  transitions smoothly to the surface of the reading region  14   b.    
     The progressive region  14   a  begins below the optical center  29 . The progressive region  14   a  may be relatively short, such that the progression is relatively fast from the focal distance of the first lens region  12  to the focal distance of the reading region  14   b , thereby providing a relatively tall reading region  14   b . Alternatively, the progressive region  14   a  may be more gradual (and therefore taller) thereby providing a reading region  14   a  that is relatively short. 
     The second lens region  14  has a first side edge  16   a  and a second side edge  16   b . The first and second side edges  16   a  and  16   b  may be curved, as shown in  FIG. 1 , or they may be generally straight, as shown in  FIG. 2 . It can be seen that the width of the second region  14  increases in the downward direction on the lens  10 . The lens  10  further includes a first transition region  22  between the first side edge  16   a  and the first lens region  12 , and a second transition region  24  between the second side edge  16   b  and the first lens region  12 . It can be seen that the transition regions  22  and  24  are generally parallel to the side edges  16   a  and  16   b . For example, as can be seen in  FIG. 1 , the transition regions  22  and  24  each have a roughly similar arcuate shape to that of the first and second side edges  16   a  and  16   b  respectively. Similarly, as shown in  FIG. 2 , the transition regions  22  and  24  have a generally straight shape that is similar to the generally straight shape of the first and second side edges  16   a  and  16   b  respectively. Additionally, the transition regions  22  and  24  may each have a selected width which may be less than a selected value, such as, for example, about 8 mm or in some embodiments less than about 7 mm, for a 70 mm diameter lens. In the embodiment shown in  FIG. 2 , the width is relatively constant along the transition regions  22  and  24  and is shown at W. In the embodiment shown in  FIG. 1 , the width of the bottom of the transition region  22  (shown at W 1 ) is larger than the width of the top of the transition region  22  (shown at W 2 ). In this embodiment, the width at all points along the transition region  22  or  24  may be less than the selected value. In such embodiments where the width varies, the transition regions  22  and  24  may have a width at their respective top ends that is less than a different selected value, such as, for example, 3 mm, or even less than 1 mm. Having a particularly narrow width at the upper end of the transition regions is valuable since in some lenses, the bottom portion of the lens (where the width W 2  in some instances is at its largest) might not be used in the final lens that ultimately is fitted into a wearer&#39;s eyeglass frames. 
     As a result of providing transition regions that are narrow, the reading region  14   b  of the lens  10  may be made relatively wide, while at the same time keeping these transition regions out of the lower left and lower right regions of the lens, shown at  26  and  28 , which, as noted above are regions of the lens  10  that are important to make distortion-free. As can be seen, the regions  26  and  28  in  FIGS. 1 and 2  are substantially entirely located within the first lens region  12 , and so there is no distortion in the regions  26  and  28 . 
     In total it will be noted that the transition regions  22  and  24 , which make up the total area of the lens  10  that may be considered to have astigmatic distortion, is less than about 25% of the swept area of the lens  10 . In some embodiments, they constitute less than about 10% of the swept area of the lens  10 . 
     The progressive region  14   a  and the area surrounding it (e.g. the upper ends of the transition regions  22  and  24 ) may have a relatively complex shape, and may be designed using a point cloud (shown at  34 ) instead of ‘building’ the complex shape by stitching together simple surfaces. It will be understood that it is possible to design the entirety of the lens  10  using a point cloud. 
     As shown in  FIGS. 1 and 2 , the second region  14  of the lens  10  may extend all the way down to the bottom of the lens  10 , such that the bottom edge of the second region  14  is a segment of the edge of the lens  10 . 
     Reference is made to  FIG. 3 , which shows a lens  100  in accordance with another embodiment of the present invention. The lens  100  is shown rotated somewhat. The optical center of the lens  100  is shown at  102 . The horizontal primary meridian is shown at  104 . The lens  100  has a first lens region  106  having first focal properties, a second lens region  108  having second focal properties and a third lens region  110  having third focal properties. The first lens region  106  may contain the optical center  102  of the lens  100 . The first lens region  106  may have substantially constant focal properties throughout, and may have a first focal distance that is selected to be suitable for a particular task. For example, the first lens region may be configured to permit the wearer to view a computer monitor, and may thus have a focal distance of less than, for example, about 30″. In another example, the focal distance may be selected to permit a musician to view sheet music while playing their instrument. The first lens region  106  preferably extends across the entire width of the lens  100 , as shown. 
     The second lens region  108  may be similar to the second lens region  14  in  FIG. 1  or  2  and may include a progressive region  108   a  and a reading region  108   b . The second lens region  108  has a first side edge  112   a  and a second side edge  112   b . First and second transition regions  114  and  116  transition between the side edges  112   a  and  112   b  and the first region  106 . The transition regions  114  and  116  may be similar to the transition regions  22  and  24  in  FIG. 1  or  2 , in that they may be generally parallel to the first and second side edges  112   c  and  112   d  respectively, and may each have a width that is less than a selected value. 
     Above the optical center  102  the third lens region  110  is provided. The third lens region  110  may includes a portion that is a progressive region  110   a  and a portion that is a long-distance viewing portion  110   b . The progressive region  110   a  has associated therewith a focal distance that varies progressively between the focal distance of the long-distance region  110   b  and the focal distance of the first lens region  110 . 
     The third lens region  110  has a first side edge  120   a  and a second side edge  120   b . Third and fourth transition regions  122  and  124  extend between the side edges  120   a  and  120   b  and the first region  106 . The transition regions  122  and  124  may be generally parallel to the first and second side edges  120   c  and  120   d  and may have a width that is less than a selected value (which may or may not be the same value as the widths of the transition regions  114  and  116 ). 
     It will be noted that the first region  106  generally surrounds the second region about a top edge and the side edges  112   a  and  112   b , and the third region about a bottom edge and the side edges  120   a  and  120   b . Thus, the first region is roughly H-shaped. 
     The lenses  10  and  100  may be manufactured by any suitable process and may be made from any suitable material. Furthermore, all the lens features (e.g. the features that form the various lens regions may be formed using the front surface of the lens  10  or  100  (i.e. the surface of the lens facing away from the wearer&#39;s eye), or using the back surface of the lens  10  or  100  (i.e. the surface of the lens facing the wearer&#39;s eye), or a combination of both. 
     The surfaces of the lens  10  or  100  may have any suitable surface shape. For example, the surfaces of the lens  10  or  100  may be generally spherical, or may be sphero-cylindrical, such that the radius of the lens  10  or  100  may remain substantially constant over a 360 degree angular sweep about the centre of the lens, or alternatively, the radius of the lens  10  or  100  may vary, such that the lens  10  or  100  may have a major axis and a minor axis. 
     While the above description constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.