BIFOCAL MULTIORDER DIFFRACTIVE
LENSES FOR VISION CORRECTION
This application is a divisional of U.S. patent application Ser. No. 10/462,294, filed Jun. 16, 2003 now U.S. Pat. No. 5 6,951,391.
FIELD OF THE INVENTION
The present invention related to multiorder diffractive io lenses for vision correction, and particularly to bifocal multiorder diffractive lenses for therapeutic vision correction at distance and near vision correction suitable for use with a variety of vision correction applications, such as intraocular implants (IOLs), contact lenses, or spectacle 15 (eyeglass) lenses.
BACKGROUND OF THE INVENTION
Multiorder diffractive (MOD) lenses are useful for bring- 20 ing a plurality of spectral components of different wavelengths to a common focus, and are described in U.S. Pat. No. 5,589,982, which is herein incorporated by reference. The MOD lens has a structure of multiple annular zones having step heights defining zone boundaries, which diffract 25 light of each of the wavelengths in a different diffractive order to a common focus. Such a MOD lens has not been applied to bifocal optics for vision correction.
Conventional bifocal optics for spectacles are provided by lenses having lower and upper regions of different refractive 30 power for near and distance (far) vision correction. For contact lenses and IOLs, multifocal refractive optics have been proposed with the anterior and/or posterior surfaces of a lens (or IOL optic) shaped to provide a central zone, annular near zones, and annular distance zones of different 35 refractive powers. Such bifocal refractive lenses do not utilize diffractive structures for near or distance vision correction. Examples of multifocal refractive lenses for contacts and IOLs are shown in U.S. Pat. Nos. 6,231,603, 5,805,260, 5,798,817, 5,715,031, 5,682,223, and U.S. Pub- 40 licationNo. U.S. 2003/0014107 Al. Other multifocal refractive lenses have other zones, such as pie, hyperbolic, or pin-wheel shaped near and distance zones, as shown in U.S. Pat. Nos. 5,512,220 and 5,507,979, or spiral shaped zones, as shown in U.S. Pat. Nos. 5,517,260 and 5,408,281. More- 45 over, refractive lenses are generally thicker than diffractive lens for equivalent optical power, and thickness reduction is often desirable in ophthalmic applications, such as contact lenses and IOLs.
Non-MOD diffractive optics for multifocal ophthalmic 50 applications exist having a lens with a surface providing a diffractive structure of concentric zones of different step heights for near and far vision correction, such as described, for example, in U.S. Pat. No. 5,699,142. Another multifocal diffractive lens, described in U.S. Pat. No. 5,748,282, has a 55 similar diffractive structure with a region having a reduced step height to reduce intensity of light from such region. A further multifocal diffractive lens is described in U.S. Pat. No. 5,116,111 also has a similar non-MOD diffractive structure in which the base power of lens may be provided by 60 refraction of the lens. The diffractive lenses of U.S. Pat. Nos. 5,699,142, 5,748,282, and 5,116,111 lack the ability of the MOD lens to focus light of different wavelengths to a common focus for either near or far vision correction by their reliance on non-MOD structures. Other non-MOD 65 optics may be segmented to provide multiple regions, but are not multifocal. For example, U.S. Pat. No. 5,071,207
describes a non-MOD diffractive lens having pie-shaped segments in which all the segments of the lens are limited to focusing light to a common focus. Thus, prior approaches to multifocal or bifocal optics have utilized refractive surfaces or non-MOD structures.
SUMMARY OF THE INVENTION
Accordingly, it is the principal object of the present invention to provide bifocal diffractive lenses utilizing multiorder diffractive (MOD) structures to provide vision correction at near and far distances.
Another object of the present invention is to provide bifocal multiorder diffractive lenses which may be adapted for use in a variety of vision correction applications, including contact lenses, intraocular implants (IOL), and spectacle lenses.
Still another object of the present invention is to provide bifocal multiorder diffractive lenses using MOD structures which may have refractive surfaces for additional power correction.
A further object of the present invention is to provide a bifocal multiorder diffractive lens for correction of vision in which the performance of the lens is tailored to the human perception of light under high (photopic) and low (scotopic) illumination.
Briefly described, the present invention embodies a lens body having one or more first regions having a first multiorder diffractive structure providing near vision correction, and one or more second regions having a second multiorder diffractive structure providing distance vision correction, in which the lens defines an aperture divided between the first and second regions. Such one or more first regions may represent one or more annular rings, or other portion of the lens, and the second region may occupy the portion of the lens aperture outside the first region, such as central region and one or more annular rings alternating with first region annular ring(s). The lens may be a single optical element having the first and second regions both located upon the same front or back surface of the lens, or the first region located upon one of the front or back surface and the second regions on the other surface. The lens may also be provided by multiple optical elements integrated into the lens body having front and back surfaces and one or more intermediate surfaces depending on the number of optical elements. The first and second regions are provided along the same or different intermediate surfaces of the lens to divide the lens aperture. One or both of the first and second multiorder diffractive structures may be optionally optimized for performance for photopic and scotopic vision.
In other embodiments, a bifocal multiorder diffractive lens is provided by a single or multiple element lens body having a multiorder diffractive structure for distance vision correction and one or more refractive regions to add power for near vision correction, or a single or multiple element lens body shaped for refractive power for distance vision correction and a multiorder diffractive structure to add power for near vision correction.
Each of the MOD structures of the lenses of the present invention directs different wavelengths of light to a single focus of an optical power for the desired vision correction. This MOD structure is characterized by multiple zones which define zone boundaries at which light incident on the diffractive structure experiences an optical phase shift, and diffracts light of each of the wavelengths in a different diffractive order, m, such that m is greater than or equal to 1, to the same focus. The zones may be radially spaced at r,