Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/024—Methods of designing ophthalmic lenses
  • G02C7/028—Special mathematical design techniques
• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/04—Contact lenses for the eyes
  • G02C7/041—Contact lenses for the eyes bifocal; multifocal
  • G02C7/042—Simultaneous type
• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/04—Contact lenses for the eyes
  • G02C7/041—Contact lenses for the eyes bifocal; multifocal
  • G02C7/044—Annular configuration, e.g. pupil tuned

Definitions

• the present invention relates to and has industrial utility with respect to contact lenses.
• Image coding allows for an enhanced or increased depth of focus (and/or depth of field) for a digital imaging system that includes an imaging lens (e.g., a commercial camera lens) and a computer image processor.
• the technique requires placing an optically non-rotationally symmetric cubic phase plate (or functional equivalent) having a phase in the form of ⁇ x 3 + ⁇ y 3 at or near the aperture stop of the imaging lens.
• the phase plate alters the energy density distribution from what it normally would be for a nominally well-corrected imaging lens.
• the cubic phase plate introduces a known, quantifiable degree of aberration into the image.
• the corresponding Point Spread Function (PSF) associated with the intentionally introduced phase aberration has the property that it remains largely unchanged over a greatly extended depth of field as compared to the imaging lens without the phase plate.
• PSF Point Spread Function
• FIG 1 is a schematic diagram of a lens 10 of a human eye ("eye lens") showing light rays 11, a focus F and depth of field (DOF) surround the focus.
• a conventional eye lens has a single focus F that can be shifted via muscular action of the eye.
• a contact lens is a single lens element that is placed in contact with the eye and over the eye lens (10) to correct vision problems, such as deteriorated accommodation (e.g., presbyopia).
• FIG. 2 is a schematic diagram of an eye lens 10 in combination with a conventional bi-focal contact lens 12. As indicated by light rays 13 (dashed) and 14 (solid), the bi-focal contact lens 12 has a near focus position F N and a far (infinite) focus position F ⁇ , each with a corresponding DOF.
• An example of such a bi-focal contact lens is disclosed in U.S. Patent No. 6,244,709, which patent is incorporated herein by reference.
• a bifocal contact lens is used to enhance near vision and far vision, but typically does not have an effect on intermediate-range vision.
• contact lens designs such as that disclosed in U.S. Patent No. 6,357,876 (the '876 patent), which patent is incorporated herein by reference, that are multi-focal and designed to enhance vision over the near, intermediate and far vision ranges through the use of a number of annular regions having optical power corresponding to focusing at the near, intermediate and far vision regions.
• a design still has distinct near and far DOF ranges.
• the amount of noise at each imaging distance is relatively large. For example, for a tri-focal lens, two-thirds of the light at each imaging distance is out of focus, which introduces substantial image noise relative to the one-third of light that is actually in focus.
• U.S. Patent No. 6,536,898 discloses a contact lens that utilizes a surface having a single phase encoded thereon.
• the phase provides an extended depth of focus (EDF) by providing a coded image onto the retina.
• EDF extended depth of focus
• the human brain then decodes this coded image, resulting in an in-focus image over an increase depth of focus.
• FIG. 3 is a schematic diagram of an eye 10 in combination with a contact lens 16 according to the '898 patent.
• Light rays 17 depicting the performance of the contact lens are also shown.
• contact lens 16 forms a relatively "fuzzy" but acceptable focus (and thus a relatively fuzzy but acceptable image) over a relatively large DOF, as illustrated by curved light rays 17.
• the human brain then processes the fuzzy image formed on the retina to compensate for the image coding effects, resulting in an in-focus image over a relatively large intermediate-range DOF (i.e., an EDF).
• an EDF intermediate-range DOF
• the contact lens of the '898 patent increases the DOF over that of a conventional contact lens, it utilizes a single phase to benefit the intermediate-range DOF. This is problematic because usually the near-visual (reading) range and the far- visual (infinite) focal distances are where the best imaging performance is often desired. Further, the single phase of the '898 patent contact lens requires a relatively high phase profile, which adds to the SNR.
• a first aspect of the invention is a contact lens that includes two or more zones, wherein adjacent zones have different optical power (which may include zero optical power).
• the one or more zones have corresponding one or more optical phases adapted to improve a depth of field as compared to the contact lens without the one or more corresponding phases.
• the contact lens may have a total of five multi-focal zones each having the same optimized phase, a total of four multi- focal zones each having different optimized phases, a total of five multi-focal zones wherein less than all of the zones has an optimized phase, etc.
• a second aspect of the invention is the above-described contact lens wherein one of the zones is a central zone and the other zones are concentric about the central zone.
• a third aspect of the invention is a contact lens that has multiple zones each having optical power.
• the lens also has one or more phases formed on corresponding one or more of the multiple zones.
• the one or more phases each has an associated Point Spread Function (PSF) that is substantially invariant over a relatively large depth of focus (DOF) as compared to an aberration-free PSF.
• PSF Point Spread Function
• a fourth aspect of the invention is a method of forming a multi-phase contact lens.
• the method includes forming two or more zones, wherein adjacent zones have different optical power.
• the method also includes adding to at least one of the zones a corresponding phase that improves a depth of field as compared to the contact lens without the phase.
• FIG 1 is a prior art schematic diagram of eye lens (10) showing the focus (F) and depth of field (DOF) surround the focus;
• FIG. 2 is a prior art schematic diagram of an eye lens (10) in combination with a conventional bi-focal contact lens (12), wherein the bi-focal contact lens has a near focus position (F N ) and a far (infinite) focus position (F ⁇ ,) each with a corresponding DOF;
• FIG. 3 is a schematic diagram of an eye (10) in combination with a contact lens (14) according to the '898 patent, illustrating the extended DOF in the intermediate focus range;
• FIG. 4 is a plan view of an example embodiment of a multi-phase contact lens according to the present invention.
• FIG. 5A is a plan view of an example embodiment of a prior art bi-focal contact lens having five multi-focal zones;
• FIG. 5B is a plan view of an example embodiment of a multi-phase contact lens formed from the prior art bi-focal lens of FIG. 5A by adding a polynomial phase to each of the multi-focal zones;
• FIG. 6 shows simulated retinal images of an extended object "F" formed by the example embodiment of the conventional five zone bi-focal contact lens of FIG. 5A for object distances of infinity (602), 4000mm (604), 1500mm (606) and 500mm (608), respectively;
• FIGS. 7A-7D show the corresponding tangential and sagittal geometric line spread functions corresponding to the simulated images 602, 604, 606 and 608 of FIG. 6
• FIG. 8 is a flow diagram of an example embodiment of a method of designing the multi-phase lens of the present invention.
• FIG. 9 shows simulated retinal images of an extended object "F" formed by the example embodiment of the multi-phase contact lens of FIG. 5B for object distances of infinity (902), 4000mm (904), 1500mm (906) and 500mm (908), respectively;
• FIGS. 10A-10D show the corresponding tangential and sagittal geometric line spread functions corresponding to the simulated images 902, 904, 906 and 908 of FIG. 9; and
• FIG. 11 is a plot of the DOF in meters (logarithmic scale) for a single-phase single-focus contact lens of the '898 patent, the conventional bi-focal contact lens (50) of FIG. 5A and for the multi-phase bi-focal lens (100) of FIG. 5B, illustrating the improved DOF for the near-vision and far-vision regions for the multi-phase bifocal lens as compared to prior art contact lenses.
• FIG. 4 is a plan view of an example embodiment of the multi-phase contact lens 20 of the present invention.
• Contact lens 20 includes two or more zones Z (e.g., Z1, Z2 and Z3, as in FIG. 4).
• adjacent zones have different optical power (optionally including no optical power).
• one or more of the zones Z has a phase P (e.g., P1 , P2, P3, as in FIG. 4).
• the particular phase P is selected according to the criteria for image-coding, which is that the point-spread function associated with the phase not change substantially over a relatively large range of defocus.
• the phase is described by the polynomial ⁇ x 3 + ⁇ y 3 and is referred to herein as a "polynomial phase.” While higher-order polynomial phases can also be used, the inventors have found that optimization of imaging using higher-order phases does not significantly improve the imaging associated with a third-order polynomial phase.
• the axes of the phase are rotated relative to each other in the different zones to optimize resolution in favored directions.
• one of the zones Z is an on-axis, i.e., is a central zone (e.g., such as circular zone Z1) while the other zones surround the central zone.
• one of the zones is a central circular zone and the other zones are annular zones that are concentric about the circular zone, as is shown in FIG. 4.
• the zones Z have periodic alternating optical power.
• central zone Z1 has near- vision power
• first surrounding zone Z2 has far-vision power
• the next surrounding zone Z3 has near-vision power
• the phase P also periodically alternates, e.g., there is a first polynomial phase associated with the near-vision power zones and a second phase associated with far-vision power zones.
• the zones have both periodically alternating power and periodically alternating phase P.
• phase profile of the contact lens can be less than that associated with a contact lens having a single phase that extends over the entire lens. Also, the smaller phase profile results in a reduced SNR and thus better imaging performance.
• the zones Z in contact lens 20 have a typical multi-focal (e.g., bi-focal, tri-focal, etc.) refractive profile, and a phase is added to one or more of the refractive zones of the otherwise typical bifocal lens.
• a phase is added to each zone and is optimized for that zone, so that the phases differ between zones. This embodiment results in improved imaging performance of the visual ranges of the conventional multi-focal lens.
• some of the phases P for different zones Z are the same, so long as there are at least two different phases in the multi-phase contact lens.
• the phase added to each zone is the same.
• phase when “a phase” is added to one or more of the zones, it is not necessary that the same phase be added to each zone. Thus, as in the example embodiments above, it can be that some but not all of the phases added to some of the zones are the same, while in other cases each added phase is different from the others.
• the design of the multi-phase contact lens of the present invention starts with a conventional contact lens, such as a multi-focal contact lens having zero phase in each zone.
• the imaging quality of this conventional contact lens is then evaluated.
• one or more phases is/are added to one or more of the zones.
• the phase or phases is/are then varied until the lens is optimized.
• the number of phases added depends on how much optimization is desired or required. The more phases that are added, the greater the number of design degrees of freedom and thus the better the chances of achieving a higher degree of imaging performance. It should be noted that the phase added to the one or more zones is/are weak enough that any chromatic aberration introduced by the added phase is not significant.
• FIG. 5A is a schematic diagram of an example conventional five zone (Z1- Z5) bifocal contact lens 50.
• Contact lens 50 also has zones Z6 and Z7 surrounding zones Z1-Z5. Zones Z1-Z5 are called the multi-focal zones, while zone 6 is called the lenticular zone and zone 7 is called the peripheral zone.
• Contact lens 50 is referred to as a five-zone because of the number of multi-focal zones.
• contact lens 50 is assumed to have a power of -2 diopters for the far-vision zones and -0.5 diopters for near-vision (i.e., reading- distance) zones, which are typical powers for such a lens.
• zones Z1-Z5 are assumed to have respective diameters of 2.0mm, 3.3mm, 4.5mm, 5.25 mm and 8mm.
• zone 6 is assumed to have a radius of about 11.2mm and zone 7 is assumed to have a diameter of about 14.2mm.
• zones Z1-Z5 are assumed to have far- vision, near-vision, far-vision, near-vision and far-vision power, respectively.
• the center thickness of contact lens 50 is assumed to be about 0.1mm, and the saggital depth is assumed to be about 3.6mm.
• the imaging performance of the above-described contact lens 50 was simulated using the letter F as a test object.
• the imaging performance of the corresponding multi-phase contact lens of the present invention was compared to that of conventional contact lens 50, as well as to that of a single-phase contact lens. Imaging performance was modeled using ZEMAX lens design software, available from ZEMAX Development Corporation, San Diego, CA. However, because of the unique design of the multiphase contact lens of the present invention, the macro language of the software needed to be modified to handle the multiple phase zones. These modifications are described below and are indicated in the design with the term "USERSURF".
• MTF modulation transfer function
• point-spread function point-spread function
• the line spread function with a 20% threshold was found to most closely represent the actual imaging performance.
• visual assessment of a simulated extended image e.g., the letter "F” was the best image evaluation criteria even though it is somewhat subjective.
• FIG. 6 shows simulated images 602, 604, 606 and 608 formed by the five zone bi-focal contact lens 50 for extended object "F" for infinity, 4000mm, 1500mm and 500mm, respectively.
• FIGS. 7A-7D show the corresponding tangential and sagittal geometric line spread functions corresponding to images 602, 604, 606 and 608, respectively, from contact lens 50. Note in FIGS. 7A-7D the noise thresholds NT caused by the out-of-focus bifocal zones.
• FIG. 8 is a flow diagram 800 of an example embodiment of a method of designing the multi-phase lens of the present invention.
• the pseudo-code of the flow diagram was developed by the inventors so that the ZEMAX lens design computer program (software) could handle the multiple phase zones in the design process.
• the use of the multiple phase components provides additional degrees of freedom to balance and optimize the lens for a given user's preference.
• the method begins with a conventional multi-focal contact lens design.
• the baseline performance of the peak resolution vs. depth of field for the conventional lens is established.
• the optimization criteria and signal v. noise operands are established. For example, as discussed above, the tangential and sagittal line spread functions with a 20% threshold is used.
• a visual assessment of a simulated extended image such as the letter "F" is used.
• a phase (e.g., a polynomial phase) is added to one or more zones of the conventional multi-focal lens.
• the amount of phase added is relatively weak and is selected as a starting point for subsequent optimization.
• the lens performance is evaluated. If the performance is "NOT OK," then the method returns to 808, where the phase for the one or more zones is adjusted and/or phase is added to zones that initially did not have phase added in the previous iteration. The performance is again evaluated in 810, and the method iterates between 808 and 810 until the selected optimization criteria established in 806 is met. One the optimization criteria are met, the lens is deemed "OK" and the method terminates in 812.
• Example multi-phase lenses e.g., a polynomial phase
• Table 1 lists the design parameters for a multi-phase contact lens based on an optimization of the five-zone bi-focal contact lens 50 using the same optimized polynomial phase for zones Z2, Z3 and Z4 as defined in the customized "USERSURF" lens macro program code. All length measurements are in millimeters (mm).
• Table 2 lists design parameters for a multi-phase contact lens based on an optimization of the five-zone bi-focal contact lens 50 that allowed for a different optimized polynomial phase in each zone. All length measurements are in millimeters (mm), and “S” represents "surface”. BK7 glass was used for modeling purposes, though the invention applies to all optical media suitable for contact lenses.
• the multi-phase lens of the present invention is formed by a standard contact lens molding process, wherein the mold includes the designed phase P for each zone Z.
• the lens can also be formed using direct means, such as by a computer-controlled lathe, by diamond turning, or by other precision polishing means.
• Two example tools suitable for fabricating the multiphase contact lens of the present invention are the NANOFORM 600 from Precitech, Keene, NH, and the Magnetorheological Finishing (MRF) machine from QED, Inc., Rochester, NY.
• FIG. 9 show simulated images of the object "F" formed by multi-phase contact lens 100 of FIG. 5B for infinity (902), 4000mm (904), 1500mm (906) and 500mm (908), respectively.
• FIGS. 10A-10D show the corresponding tangential and sagittal geometric line spread functions corresponding to the images 902, 904, 906 and 908 for multi-phase contact lens 100 of FIG. 5B. Again, note in FIGS. 10A-10D the noise thresholds NT caused by the out-of-focus bifocal zones.
• FIG. 11 plots the DOF estimates for a single-phase, single-focus contact lens of the '898 patent, the conventional bi-focal contact lens 50, and multi-phase contact lens 100 based the above-described imaging simulation performed over a large DOF range. It is important to note the logarithmic scale of the horizontal DOF axis. Both the line-spread function figure of merit and visual assessment of the modeled image were used to determine the points at which a "just noticeable" drop in visual acuity occurred.
• the near-focus DOF for the multi-phase contact lens 100 is roughly double that the conventional bi-focal contact lens 50.
• the near end of the far-vision DOF is significantly extended toward the near- vision DOF.
• the significant increase in DOF in the near-vision and far-vision ranges is paid for by a very small reduction in the peak visual acuity which would be barely if at all noticeable.
• the plot of FIG. 11 compares a conventional bifocal contact lens 50 to the modified multi-phase bifocal contact lens 100. So, as expected, there is a mid-range-vision gap in the DOF coverage.
• the multiphase contact lens of the present invention includes embodiments that fill the mid- range gap by not limiting the refractive power of the zones to bi-focal.
• zones Z are multi-focal, such as tri-focal with near-vision, intermediate-vision and far-vision zones, such as disclosed in the '876 patent.
• the distinct DOF ranges associated with the multi-focal zones are then extended by adding one or more phases to one or more of the zones to extend each of the DOF ranges so that they approach or overlap one another.
• FIG. 11 includes the DOF range for an optimized single-polynomial-phase, single-focus contact lens based on the '898 patent.
• the optimization of such a lens results in improvement of the mid-vision range without improving the near or far vision ranges.
• the multi-phase contact lens of the present invention is capable of covering a larger range of DOF, and in particular can cover the near and far visual ranges more effectively than an optimized single-phase, single-focus contact lens according to the '898 patent.

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• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Mathematical Physics (AREA)
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• 2004
  • 2004-06-15 EP EP04755326A patent/EP1639399A2/de not_active Withdrawn
  • 2004-06-15 JP JP2006517294A patent/JP2007524110A/ja active Pending
  • 2004-06-15 WO PCT/US2004/019083 patent/WO2004113994A2/en not_active Application Discontinuation

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