Ophthalmic diffractive multi-focal lens and method for manufacturing ophthalmic diffractive multi-focal lens

Abstract

Provided is an ophthalmic diffractive multi-focal lens with a diffractive structure including a phase profile in which a plurality of blaze shaped zones are set in a concentric circle form, wherein: at least one of the zones serves as an adjustment zone wherein an inclination direction in the phase profile is reversed with respect to that of other zones; and a light intensity level giving a peak or focal point at a position away from three focal points in a light intensity distribution of transmitted light in an optical axis direction is kept low in comparison with a phase profile without the adjustment zone.

Claims

1. An ophthalmic diffractive multi-focal lens comprising a diffractive structure including a phase profile having a plurality of blaze shaped zones being set in a concentric circle form, the diffractive structure generating at least three focal points in an optical axis direction, wherein at least one of the zones serves as an adjustment zone for which an inclination direction in the phase profile is reversed with respect to that of other zones, a light intensity level giving a peak at a position away from the three focal points in a light intensity distribution of transmitted light in the optical axis direction is kept low in comparison with a phase profile without the adjustment zone, and an inclination angle of the adjustment zone in the phase profile specified by a following equation is not greater than 20 radians/mm.sup.2:
inclination angle=(absolute value of phase constant×2×π)/zone area (unit: radians/mm.sup.2).

2. The ophthalmic diffractive multi-focal lens according to claim 1, wherein in the phase profile, a phase shift of the adjustment zone is set within a range of −π to +π radians with respect to a reference line of a phase (an r axis of ϕ=0 in an r−ϕ coordinate system of a phase function ϕ(r)) in the phase profile.

3. The ophthalmic diffractive multi-focal lens according to claim 1, wherein in the phase profile, the adjustment zone is set such that the adjustment zone intersects a reference line of a phase (an r axis of ϕ=0 in an r−ϕ coordinate system of a phase function ϕ(r)) in the phase profile.

4. An ophthalmic diffractive multi-focal lens comprising a diffractive structure including a phase profile having a plurality of blaze shaped zones being set in a concentric circle form, the diffractive structure generating at least three focal points in an optical axis direction, wherein at least one of the zones serves as an adjustment zone for which an inclination direction in the phase profile is reversed with respect to that of other zones, a light intensity level giving a peak at a position away from the three focal points in a light intensity distribution of transmitted light in the optical axis direction is kept low in comparison with a phase profile without the adjustment zone, and, the peak in the light intensity distribution of the transmitted light in the optical axis direction that is kept low in comparison with the phase profile without the adjustment zone is a peak that exists within a range of ±5 diopters with respect to a focal point position of at least one of the three focal points in optical characteristics given by the phase profile without the adjustment zone, and is a peak that has a peak level which is not less than one-third of that of at least one of the three focal points.

5. An ophthalmic diffractive multi-focal lens comprising a diffractive structure including a phase profile having a plurality of blaze shaped zones being set in a concentric circle form, the diffractive structure generating at least three focal points in an optical axis direction, wherein at least one of the zones serves as an adjustment zone for which an inclination direction in the phase profile is reversed with respect to that of other zones, a light intensity level giving a peak at a position away from the three focal points in a light intensity distribution of transmitted light in the optical axis direction is kept low in comparison with a phase profile without the adjustment zone, and, a peak level of the peak in the light intensity distribution of the transmitted light in the optical axis direction that is kept low in comparison with the phase profile without the adjustment zone is not greater than 50% of all peak levels of the three focal points.

6. The ophthalmic diffractive multi-focal lens according to claim 1, wherein the phase profile has a periodic structure of zone groups repeated in a radial direction, the zone groups comprising a certain number of the zones, and the zones that correspond in at least two of the zone groups each serve as the adjustment zone.

7. The ophthalmic diffractive multi-focal lens according to claim 1, wherein the phase profile set in the concentric circle form is set based on a Fresnel pitch.

8. An ophthalmic diffractive multi-focal lens comprising a diffractive structure including a phase profile having a plurality of blaze shaped zones being set in a concentric circle form, the diffractive structure generating at least three focal points in an optical axis direction, wherein at least one of the zones serves as an adjustment zone for which an inclination direction in the phase profile is reversed with respect to that of other zones, a light intensity level giving a peak at a position away from the three focal points in a light intensity distribution of transmitted light in the optical axis direction is kept low in comparison with a phase profile without the adjustment zone, and the phase profile to which the plurality of blaze shaped zones generating at least three focal points in the optical axis direction are set in the concentric circle form using the diffractive structure serves as an adjusted profile, the adjusted profile being dividable into starting profiles that are a plurality of phase profiles configured to be overlapped each other, and the adjusted profile being a composite profile generated by the phase profiles being overlapped, and at least one of the zones of the composite profile serves as the adjustment zone for which an inclination direction has a different blaze shape from an overlapping of the starting profiles.

9. The ophthalmic diffractive multi-focal lens according to claim 1, wherein the blaze shaped phase profile is expressed by Equation 1: $\begin{array}{cc}\varphi \left(r\right)=\frac{{\varphi }_i-{\varphi }_{i-1}}{r_i-r_{i-1}}\times r+\frac{{\varphi }_{i-1}\times r_i-\varphi \times r_{i-1}}{r_i-r_{i-1}}+\tau & \left[\mathrm{Equation}1\right]\end{array}$ r: Radial distance from the lens center r.sub.i-1: Inner diameter (radius) of the ith zone r.sub.i: Outer diameter (radius) of the ith zone ϕ.sub.i-1: Phase at the inner diameter (radius) position of the ith zone ϕ.sub.i: Phase at the outer diameter (radius) position of the ith zone τ: Phase shift.

10. The ophthalmic diffractive multi-focal lens according to claim 1, wherein a reduction ratio in a light intensity level due to the adjustment zone for a light intensity peak that is fourth highest in the light intensity level after the three focal points is greater than reduction ratios in light intensity levels due to the adjustment zone for light intensity peaks of the three focal points.

11. A method for manufacturing an ophthalmic diffractive multi-focal lens capable of generating at least three focal points in an optical axis direction using a diffractive structure comprising a plurality of zones in a concentric circle form, the method comprising: setting a phase profile including the zones having a blaze shape inclining in a same direction, the phase profile generating the at least three focal points; and reducing a light intensity level giving a peak at a position away from the three focal points in a light intensity distribution of transmitted light in the optical axis direction by setting an adjustment zone for which an inclination direction of at least one of the zones of the phase profile is reversed with respect to that of other zones, wherein an inclination angle of the adjustment zone in the phase profile specified by a following equation is not greater than 20 radians/mm.sup.2:
inclination angle=(absolute value of phase constant×2×π)/zone area (unit: radians/mm.sup.2).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph of a phase function in the r−ϕ coordinate system with the phase ϕ of a phase modulation structure provided in the diffractive lens expressed as the relationship with the lens radial direction position r.

(2) FIGS. 2A-2D are graphs each showing an example of a blaze as a mode of the phase function in the diffractive lens.

(3) FIG. 3 is a drawing for explaining a mode of the blaze given by the phase shift τ.

(4) FIG. 4 is a drawing for explaining a structure for which, as one example of a blaze of a diffraction grating, a phase profile of a lens having a standard profile can be grasped as an overlapping of two zone sequences (1) and (2).

(5) FIG. 5 is a drawing showing a phase profile which is a standard profile contrasted with the diffractive multi-focal ophthalmic lens according to the present invention.

(6) FIG. 6 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of the ophthalmic lens having the standard profile shown in FIG. 5.

(7) FIG. 7 is a drawing showing a phase profile which is a present invention profile of the diffractive multi-focal ophthalmic lens as Example 1 of the present invention.

(8) FIG. 8 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of an ophthalmic lens having the phase profile shown in FIG. 7 as Example 1 of the present invention.

(9) FIG. 9 is a drawing showing a phase profile which is a present invention profile of the diffractive multi-focal ophthalmic lens as Example 2 of the present invention.

(10) FIG. 10 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of an ophthalmic lens having the phase profile shown in FIG. 9 as Example 2 of the present invention.

(11) FIG. 11 is a drawing showing a phase profile which is a present invention profile of the diffractive multi-focal ophthalmic lens as Example 3 of the present invention.

(12) FIG. 12 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of an ophthalmic lens having the phase profile shown in FIG. 11 as Example 3 of the present invention.

(13) FIG. 13 is a drawing showing a phase profile which is a present invention profile of the diffractive multi-focal ophthalmic lens as Example 4 of the present invention.

(14) FIG. 14 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of an ophthalmic lens having the phase profile shown in FIG. 13 as Example 4 of the present invention.

(15) FIG. 15 is a drawing showing a phase profile which is a present invention profile of the diffractive multi-focal ophthalmic lens as Example 5 of the present invention.

(16) FIG. 16 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of an ophthalmic lens having the phase profile shown in FIG. 15 as Example 5 of the present invention.

(17) FIG. 17 is a drawing showing a phase profile which is a present invention profile of the diffractive multi-focal ophthalmic lens as Example 6 of the present invention.

(18) FIG. 18 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of an ophthalmic lens having the phase profile shown in FIG. 17 as Example 6 of the present invention.

(19) FIG. 19 is a drawing showing a phase profile which is a present invention profile of the diffractive multi-focal ophthalmic lens as Example 7 of the present invention.

(20) FIG. 20 is a drawing showing an intensity distribution on the optical axis which is an optical characteristic of an ophthalmic lens having the phase profile shown in FIG. 19 as Example 7 of the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

(21) Following, the present invention will be more specifically clarified by describing embodiments for carrying out the invention. First, methods and conditions, etc., for calculation simulation used by the following examples are explained.

(22) Simulation of the Intensity Distribution on the Optical Axis

(23) With simulation of the intensity distribution on the optical axis, for the calculation software, an item was used that can calculate amplitude distribution and intensity distribution from each zone based on a diffraction integral equation derived from a theory known in the field called the scalar diffraction theory. Using this calculation software, we calculated the intensity distribution on the optical axis. A far point light source was set up as light source for calculation, and the calculation was performed on the assumption that parallel light beams in the same phase enter into the lens. Also, in the calculation, it was assumed that the media on the object and image sides are vacuum and the lens is an ideal lens having no aberration (light beams passing through the lens form an image at the same focal point regardless of the emitting position of the light). Further, the calculation was performed based on the assumption that the wavelength equals 546 nm and the refractive power of the lens for the 0th order diffracted light (basic refractive power) equals 7 D.

(24) Also, in the examples below, unless otherwise specified, calculation was performed with the blaze as a linear function, and expressed by the function determined by Equation 7 below.

(25) $\begin{array}{cc}\varphi \left(r\right)=\frac{{\varphi }_i^{\prime }-{\varphi }_{i-1}^{\prime }}{r_i-r_{i-1}}\times r+\frac{{\varphi }_{i-1}^{\prime }\times r_i-{\varphi }_i^{\prime }\times r_{i-1}}{r_i-r_{i-1}}& \mathrm{Equation}7\end{array}$
r: Radial distance from the lens center
r.sub.i-1: Inner diameter (radius) of the ith zone
r.sub.1: Outer diameter (radius) of the ith zone
ϕ.sub.i-1′: Phase at the inner diameter (radius) position of the ith zone
ϕ.sub.i′: Phase at the outer diameter (radius) position of the ith zone

(26) The intensity distribution on the optical axis was such that the distance on the optical axis from the lens position as the base point to the image plane was converted to diopters, the focal point position of the 0th order diffracted light was standardized as 0 D, and the intensity was plotted on that standardized scale. The lens aperture range for which the calculation simulation was performed, unless otherwise specified, was the region up to the zone number described in each example.

(27) During explaining specific examples of the present invention obtained based on the method and conditions of the calculation simulation as described above based on examples, first, an outline is given of the structure and characteristics of the diffractive lens based on the present invention.

(28) In Table 1 and FIG. 5, an example is shown of the standard profile which is the base of the diffractive structure of the present invention. The standard profile has a zone structure in which zone radii determined based on the Fresnel pitch equation of Equation 8 are arranged in a concentric circle form with the design wavelength being 546 nm and the addition power being P=4 D, and has a structure in which the blaze shape is determined by the phase constants and the phase shifts shown in Table 1.

(29) $\begin{array}{cc}{r}_i=\sqrt{\frac{2i\lambda }{P}}& \mathrm{Equation}8\end{array}$
r.sub.1: The ith zone radius of a certain zone sequence
i: Natural number
P: Addition power based on 1st order diffracted light of the zone sequence
λ: Design wavelength

(30) TABLE-US-00001 TABLE 1 Zone radius r.sub.i Phase Phase shift τ Zone No. i (mm) constant h (radians) 1 0.5225 0.60 −0.47 2 0.7389 0.63 0.44 3 0.9050 0.25 0 4 1.0450 0.58 −0.69 5 1.1683 0.61 0.60 6 1.2798 0.25 0 7 1.3824 0.59 −0.66 8 1.4778 0.61 0.61 9 1.5675 0.25 0 10 1.6523 0.59 −0.65 11 1.7329 0.60 0.61 12 1.8100 0.25 0 13 1.8839 0.60 −0.64 14 1.9550 0.60 0.62

(31) FIG. 6 shows the intensity distribution on the optical axis of this standard profile. With this standard profile, Peak 1 is generated at the 0 D position based on the 0th order diffracted light, Peak 2 at approximately the 1.33 D position, Peak 3 at approximately the 2.67 D position, and Peak 4 at the 4 D position, thereby generating four peaks in total for forming main focal points.

(32) When this lens is applied as an intraocular lens, for example, the intraocular lens is configured such that the 0 D peak acts as a focal point for far vision, the 1.33 D peak can be used as a focal point for which objects of approximately 1.5 to 2 m in front can be seen, the 2.67 D peak can be used as a focal point for which objects of approximately 50 to 60 cm in front can be seen, and also, the 4 D peak can be used as a focal point for which objects of approximately 35 to 40 cm in front can be seen. Such intraocular lens is useful as a multi-focal intraocular lens with which objects can be seen in a wide range from the near region for reading to the far region.

(33) The far region is a basic and important region when people see the objects. The near region is an important region in everyday life beginning with reading, viewing a mobile tablet, sewing, cooking, and so forth. Besides, in recent years, there are increasing opportunities to view a personal computer screen, and visibility for objects in a region of 50 to 60 cm in front becomes more important. Greater importance is being placed on ensuring visions for these regions as well as enhancing the quality of vision.

(34) Turning to the ophthalmic lens comprising the standard profile as well, it is necessary to suitably modulate the peak intensities of these regions, namely, Peaks 1, 2, 3, and 4 in FIG. 6 and make the ophthalmic lens suitable for intended uses by patients and users. Also, in some instances, in order to suppress halo which tends to be a problem during far vision such as night driving and enhance the quality of vision at Peak 1 giving a focal point for far vision, it is necessary to suppress or substantially eliminate the level of Peak 2 or the like which is relatively less important for the users.

(35) Each of examples of the present invention described below is an exemplary mode of the ophthalmic diffractive multi-focal lens of novel structure in which the diffractive lens, which gives at least three focal point peaks in light of such background or circumstances, is able to reduce the peak intensity at the position away from the three focal points depending on the regions for viewing objects, and more preferably, is able to increase at least one of the three peak intensities.

Example 1

(36) In Example 1, among the four focal point peaks given by the standard profile, the amount of light distributed to Peak 2 is reduced. Besides, the light energy peaks of the focal point positions other than Peak 2 are increased.

(37) In Example 1, the zone radius is set equal to that of the standard profile, and the phase constants and the phase shifts shown in Table 2 are newly set. Specifically, the zones of zone numbers 3, 6, 9, and 12 are the adjustment zones with the phase constant and the phase shift set to zero. Details of the phase profile of Example 1 are shown in FIG. 7 and Table 2.

(38) TABLE-US-00002 TABLE 2 Phase Phase shift τ Zone No. i constant h (radians) 1 0.58 −0.37 2 0.60 0.32 3 0 0 4 0.57 −0.40 5 0.59 0.35 6 0 0 7 0.58 −0.38 8 0.59 0.35 9 0 0 10 0.58 −0.38 11 0.59 0.36 12 0 0 13 0.58 −0.37 14 0.59 0.36

(39) The zones of zone numbers 3, 6, 9, and 12 that serve as the adjustment zones have the inclination angle of 0, which is one mode in which the inclination direction is reversed with respect to the blaze of the standard profile of FIG. 5. In the present embodiment in particular, the phase is set on the reference surface.

(40) The intensity distribution on the optical axis of Example 1 is shown in FIG. 8. Additionally, for each peak, the intensity before and after arranging the adjustment zone as well as the intensity change ratio are shown in Table 3.

(41) TABLE-US-00003 TABLE 3 Peak intensity change of Example 1 before and after adjustment Peak 1 2 3 4 Peak Before 4.28 1.99 2.72 3.84 intensity adjustment (×10.sup.11) After 5.72 0.48 2.78 3.29 adjustment Intensity change 34 −76 2 −14 ratio (%)

(42) With the lens including the adjustment zone of Example 1, we can see that, in comparison with the lens of the standard profile without the adjustment zone, the intensity of Peak 2 is considerably reduced, and the peak is substantially eliminated by being reduced to as far as a noise-like level. Moreover, in the present example, we can see that the reduced amount of the light energy of Peak 2 is mainly distributed to Peak 1 for far vision, increasing its intensity. The lens after the adjustment is able to provide an ophthalmic lens with more enhanced far vision.

Example 2

(43) In Example 2, the zones of zone numbers 9 and 12 of Example 1 are set with the phase constants and the phase shifts shown in Table 4. The phase profile including such adjustment zone is shown in FIG. 9. With the phase constants of the 9th and 12th zones kept zero, the peak point positions of the adjacent outer zones are set to be aligned therewith.

(44) TABLE-US-00004 TABLE 4 Phase Phase shift τ Zone No. i constant h (radians) 1 0.58 −0.37 2 0.60 0.32 3 0 0 4 0.57 −0.40 5 0.59 0.35 6 0 0 7 0.58 −0.38 8 0.59 0.35 9 0 1.45 10 0.58 −0.38 11 0.59 0.36 12 0 1.45 13 0.58 −0.37 14 0.59 0.36

(45) The intensity distribution on the optical axis of Example 2 is shown in FIG. 10. The peak intensity before and after adjustment as well as the intensity change ratio are shown in Table 5. The intensity of Peak 2 is considerably reduced, and the reduced amount of its intensity is distributed to Peak 3 as the increased amount of its intensity. Thus, such ophthalmic lens is a lens which is advantageous for personal computer work or the like.

(46) TABLE-US-00005 TABLE 5 Peak intensity change of Example 2 before and after adjustment Peak 1 2 3 4 Peak Before 4.28 1.99 2.72 3.84 intensity adjustment (×10.sup.11) After 4.12 0.61 3.63 3.28 adjustment Intensity change −4 −70 34 −15 ratio (%)

Example 3

(47) In Example 3, the phase constants and the phase shifts of the zones of zone numbers 3 and 6 of Example 1 are set with the values shown in Table 6. Specifically, the inclinations of the 3rd and 6th zones are set to zero, thereby serving as the adjustment zones so as to be aligned with the valleys of the adjacent inner zones. Details of the phase profile of Example 3 are shown in FIG. 11.

(48) TABLE-US-00006 TABLE 6 Phase Phase shift τ Zone No. i constant h (radians) 1 0.58 −0.37 2 0.60 0.32 3 0 −1.57 4 0.57 −0.40 5 0.59 0.35 6 0 −1.50 7 0.58 −0.38 8 0.59 0.35 9 0 0 10 0.58 −0.38 11 0.59 0.36 12 0 0 13 0.58 −0.37 14 0.59 0.36

(49) The intensity distribution on the optical axis of Example 3 is shown in FIG. 12. The peak intensity before and after adjustment as well as the intensity change ratio are shown in Table 7. The intensity of Peak 2 is considerably reduced, and the reduced amount of its intensity is distributed to Peak 3 as the increased amount of its intensity. Thus, such ophthalmic lens is a lens which is advantageous for personal computer work or the like.

(50) TABLE-US-00007 TABLE 7 Peak intensity change of Example 3 before and after adjustment Peak 1 2 3 4 Peak Before 4.28 1.99 2.72 3.84 intensity adjustment (×10.sup.11) After 4.45 0.34 3.49 3.28 adjustment Intensity change 4 −83 28 −15 ratio (%)

Example 4

(51) In Example 4, the phase constants and the phase shifts of the zones of zone numbers 3, 6, 9, and 12 of Example 1 are set with the values shown in Table 8. Specifically, the inclinations of the 3rd, 6th, 9th, and 12th zones that are made horizontal in Example 1 are slightly reversed with respect to the inclinations of other zones.

(52) TABLE-US-00008 TABLE 8 Phase Phase shift τ Zone No. i constant h (radians) 1 0.58 −0.37 2 0.60 0.32 3 −0.05 0 4 0.57 −0.40 5 0.59 0.35 6 −0.05 0 7 0.58 −0.38 8 0.59 0.35 9 −0.05 0 10 0.58 −0.38 11 0.59 0.36 12 −0.05 0 13 0.58 −0.37 14 0.59 0.36

(53) Details of the phase profile of Example 4 are shown in FIG. 13. The intensity distribution on the optical axis of Example 4 is shown in FIG. 14, while the peak intensity before and after adjustment as well as the intensity change ratio are shown in Table 9. The intensity of Peak 2 is considerably reduced, and the reduced amount of its intensity is distributed to Peak 1 and Peak 3 as the increased amount of their intensities. Thus, such ophthalmic lens is a lens which provides more enhanced far vision, and is advantageous for personal computer work or the like as well.

(54) TABLE-US-00009 TABLE 9 Peak intensity change of Example 4 before and after adjustment Peak 1 2 3 4 Peak Before 4.28 1.99 2.72 3.84 intensity adjustment (×10.sup.11) After 5.70 0.41 3.03 3.11 adjustment Intensity change 33 −80 11 −19 ratio (%)

Example 5

(55) In Example 5, the inclinations of the adjustment zones of zone numbers 3, 6, 9, and 12 of Example 4, for which the inclinations are reversed, are made larger. Details of the phase profile of Example 5 are shown in FIG. 15 and Table 10.

(56) TABLE-US-00010 TABLE 10 Phase Phase shift τ Zone No. i constant h (radians) 1 0.58 −0.37 2 0.60 0.32 3 −0.2 0 4 0.57 −0.40 5 0.59 0.35 6 −0.2 0 7 0.58 −0.38 8 0.59 0.35 9 −0.2 0 10 0.58 −0.38 11 0.59 0.36 12 −0.2 0 13 0.58 −0.37 14 0.59 0.36

(57) Besides, the intensity distribution on the optical axis is shown in FIG. 16, while the peak intensity before and after adjustment as well as the intensity change ratio are shown in Table 11.

(58) TABLE-US-00011 TABLE 11 Peak intensity change of Example 5 before and after adjustment Peak 1 2 3 4 Peak Before 4.28 1.99 2.72 3.84 intensity adjustment (×10.sup.11) After 5.40 0.20 3.80 2.71 adjustment Intensity change 26 −90 40 −29 ratio (%)

(59) As will be understood from the intensity distribution on the optical axis of FIG. 16, in the present example, the intensity of Peak 2 is considerably reduced, and the reduced amount of its intensity is distributed to Peak 3 and Peak 1 as the increased amount of their intensities. Thus, the lens of Example 5 is a lens which provides enhanced quality of vision during personal computer work as well as enhanced far vision.

Example 6

(60) In Example 6, the inclinations of the zones which serve as the adjustment zone in Example 5 are kept unchanged, while their phase shifts are modulated so as to be aligned with the valleys of the adjacent inner zones. Details of such phase profile are shown in FIG. 17 and Table 12.

(61) TABLE-US-00012 TABLE 12 Phase Phase shift τ Zone No. i constant h (radians) 1 0.58 −0.37 2 0.60 0.32 3 −0.2 −0.94 4 0.57 −0.40 5 0.59 0.35 6 −0.2 −0.88 7 0.58 −0.38 8 0.59 0.35 9 −0.2 −0.86 10 0.58 −0.38 11 0.59 0.36 12 −0.2 −0.85 13 0.58 −0.37 14 0.59 0.36

(62) Besides, the intensity distribution on the optical axis is shown in FIG. 18, while the peak intensity before and after adjustment as well as the intensity change ratio are shown in Table 13.

(63) TABLE-US-00013 TABLE 13 Peak intensity change of Example 6 before and after adjustment Peak 1 2 3 4 Peak Before 4.28 1.99 2.72 3.84 intensity adjustment (×10.sup.11) After 4.76 0.31 3.97 2.87 adjustment Intensity change 11 −84 46 −25 ratio (%)

(64) As will be understood from the intensity distribution on the optical axis of FIG. 18, in the present example, the intensity of Peak 2 is considerably reduced, and the reduced amount of its intensity is distributed to Peak 3 and Peak 1 as the increased amount of their intensities. Thus, the lens of Example 6 is a lens which provides enhanced quality of vision during personal computer work as well as enhanced far vision.

Example 7

(65) Example 7 has a structure in which the ends of the blaze of the zones of zone numbers 3, 6, 9, and 12 that serve as the adjustment zones are arranged so as to be aligned with the valley of the adjacent inner zone and the peak point of the adjacent outer zone. Details of such phase profile are shown in FIG. 19 and Table 14.

(66) TABLE-US-00014 TABLE 14 Phase Phase shift τ Zone No. i constant h (radians) 1 0.58 −0.37 2 0.60 0.32 3 −0.47 −0.08 4 0.57 −0.40 5 0.59 0.35 6 −0.47 −0.03 7 0.58 −0.38 8 0.59 0.35 9 −0.47 −0.02 10 0.58 −0.38 11 0.59 0.36 12 −0.47 −0.02 13 0.58 −0.37 14 0.59 0.36

(67) Besides, the intensity distribution on the optical axis is shown in FIG. 20, while the peak intensity before and after adjustment as well as the intensity change ratio are shown in Table 15.

(68) TABLE-US-00015 TABLE 15 Peak intensity change of Example 7 before and after adjustment Peak 1 2 3 4 Peak Before 4.28 1.99 2.72 3.84 intensity adjustment (×10.sup.11) After 4.19 0.04 5.00 2.48 adjustment Intensity change −2 −98 84 −35 ratio (%)

(69) As will be understood from the intensity distribution on the optical axis of FIG. 20, in the present example, the intensity of Peak 2 is considerably reduced, and the reduced amount of its intensity is mainly distributed to Peak 3 as the increased amount of its intensity. Thus, the lens of Example 7 is an ophthalmic lens which provides enhanced quality of vision during personal computer work.

(70) Meanwhile, the preceding Example 1 or the like can also be grasped as the diffractive multi-focal lens by itself that has the present invention profile comprising a specific phase profile described in FIG. 7 or the like without taking the standard profile into consideration. Specifically, in the lens of Example 1, the phase profile has a structure of zone groups α repeated in the radial direction, the zone groups α comprising a certain number (three) of the zone sequences (i), (ii), and (iii). The first zone, which is positioned at the center portion including the optical axis, is grasped as an irregular zone that does not belong to any zone sequence. A plurality of zone groups α1 to α4 that are repeated in the radial direction are set with the radial pitch such that the areas of annular regions around the optical axis of the lens center projected on the reference surface (depicted by the line of phase 0 in FIG. 5) are equal to each other.

(71) Here, the zone sequence (ii) has a gentle and non-blaze shape in which the phase constant is set to 0 so that the blaze substantially does not exist and extends roughly parallel to the reference surface, and can be grasped as a connection zone that connects the phase planes of the adjacent blaze shaped zones of the zone sequences (i) and (iii) on both sides. Therefore, with the other examples as well, the zones corresponding to the zone sequence (ii) of Example 1 each can be grasped as a connection zone having a gentle and non-blaze shape with its inclination angle of the blaze shaped phase profile made smaller than that of the zones belonging to other zone sequences in the same zone group.

(72) Besides, the blaze shaped zones belonging to the other zone sequences (i) and (iii) include a peak point having a plus-side phase peak at the inner radial end of the inclination region as well as a valley bottom point having a minus-side phase peak at the outer radial end thereof. In contrast to this mode, the connection zone is set with a characteristic phase profile for which none of a peak point at the inner radial end and a valley bottom point at the outer radial end is included.

(73) Moreover, in the case of having the phase profile in which the zone groups comprising a plurality of zone sequences are repeated as described above, it is also possible to determine which zone sequence is targeted to be the connection zone by, for example, performing simulation with respect to various types of modes in consideration of the required optical characteristics or the like. It is realistically possible to perform simulation by varying the zone sequence to which the connection zone is set, or by varying the inclination angle of the phase profile of the connection zone and examine the characteristic tendency so as to set the optical characteristics.

(74) Meanwhile, with the present invention profile, it is important that the sign of the inclination of the blaze of the specific zone (adjustment zone) is reversed (including the inclination is 0) with respect to the blaze of the corresponding zone of the standard profile or the blaze of the zone of the other zone sequences. Thus, the specific shape of the inclined portion that is the blaze trajectory is not limited, and for example, in addition to a straight line, a parabolic shape, and furthermore, a shape expressed by a trigonometric function such as a Sine function, or a trajectory of combination of these and the like can also be the target of implementation. Besides, even if the blaze of the standard profile has a curved shape, the blaze having a straight line shape with reversed inclination in the present invention profile may be adopted. Moreover, in the case in which a connection zone is formed in the blaze of a specific zone sequence, it is not necessary to form the connection zone to all the zone groups belonging to such zone sequence, but is acceptable that only the blaze of such zone sequence existing in a specific zone group serves as the connection zone or the adjustment zone.

(75) From the examples described above, we can see that by adopting the phase profile to which the adjustment zone or the connection zone is set according to the present invention, in the diffractive multi-focal ophthalmic lens, it is possible to adjust the optical characteristics. Besides, we can see that in order to enhance the light energy level at a specific focal point position, the enhancement can also be realized by the light energy level at another focal point position being kept low. Also, according to the preceding examples, with respect to the focal point position aimed at enhancing the light energy level, it is conceivable that reducing the light energy level of the adjacent focal point position is effective. Additionally, it would also be understood that the present invention can preferably be applied in order to reduce the light energy level of the focal point existing at the position sandwiched between the required focal points, thereby making it possible to tune the optical characteristics while avoiding an adverse effect on the focal point at the position adjacent to the focal point for which the light energy level is reduced.

(76) Furthermore, no particular limitation is imposed as to which zone is adopted as the adjustment zone or the connection zone, and this can be selected by performing simulation as described above. However, as one selection criterion, it is conceivable to adopt the zone by excluding the zone with the maximum zone pitch in a single zone group. Specifically, in general, the image-formation characteristics of the focal point image plane of the 0th order diffracted light among the lights made incident on a lens and emitted is described by Fourier transform of the pupil function representing the lens characteristics. For the phase function configuring the pupil function as well, it is also possible to grasp the image-formation characteristics from the Fourier transform analogy. For example, a sawtooth form periodic function can be considered to provide the point spread function including a peak distribution similar to the Fourier transform spectrum for the sawtooth function with respect to the image-formation characteristics of the focal point image plane, and it can also be considered that weak peaks generated at the positions away from the image plane center cause halo or the like. On the other hand, an item for which the inclination of the blaze of a specific zone in the sawtooth form is reversed gives a pseudo triangular shape between adjacent zones, and is similar to the trigonometric function shape as the Fourier spectral component. Thus, the Fourier transform spectrum has a structure mainly comprising a low-frequency spectrum, and provides the point spread function for which the noise peaks do not expand to outer peripheral region. Accordingly, from the analogy of Fourier transform for the sawtooth function, for a blaze of which a zone period is short, in other words, the blaze of the region with a narrow zone pitch, a weak peak noise is likely to be generated up to the outer peripheral part with the point spread function. Thus, it is also conceivable that such zone can be a preferred target zone for being adopted as the adjustment zone or the connection zone.

(77) Also, considering ease of production of the diffractive lens or considering the effect on the basic optical characteristics of the diffractive lens, among a plurality of zone sequences, the zone sequence excluding the zone sequence with the maximum phase amplitude is preferably adopted as the adjustment zone or the connection zone. Incidentally, in the preceding examples, among a plurality of zone sequences, the zone sequence (ii) with the minimum phase amplitude is adopted as the adjustment zone or the connection zone.

(78) Moreover, it would also be acceptable to set the inclination angle of the zone defined by the following equation with an absolute value that is smaller than those of other zones in the adjustment zone or the connection zone. As shown in the preceding examples in particular, the inclination angle is preferably set within the range of 0 to 20 radians/mm.sup.2. Specifically, Example 1 adopts the adjustment zone or the connection zone having the inclination angle of 0 radians/mm.sup.2, while Example 7 adopts the adjustment zone or the connection zone having the inclination angle of 3.44 radians/mm.sup.2.
Inclination angle=(absolute value of phase constant×2×π)/zone area (unit: radians/mm.sup.2)

(79) Besides, it is preferable to set the phase shift of the adjustment zone or the connection zone in the present invention within the range of −π to +π radians with respect to the reference line of the phase, as described in Examples 1 to 7. For example, the phase shift can be set within the range of −1 to +1 radians as shown in Examples 1, 4, and 5, and can be set with the reversed inclination that intersects the reference line as shown in Examples 4, 5, and 7. Furthermore, in the case of adopting the mode wherein the phase constant h is 0 as well, it would be acceptable to set the phase profile so as to be aligned with the reference line as described in Example 1, or otherwise, to set the phase profile so as to match the valley bottom point or the peak point that are positioned at the inner radial end or the outer radial end of such zone as described in Examples 2 and 3. Moreover, as shown in Examples 1 to 5, it would also be possible to form the adjustment zone or the connection zone with the zone profile that connects the stepped parts, which are positioned at the inner and outer radial ends and are orthogonal to the reference line, at the mid-positions of the height. However, it would also be acceptable to adopt the zone profile that extends from the valley bottom point or the peak point at one of the inner and outer radial ends as shown in Example 6, or to adopt the zone profile that directly connects the valley bottom point positioned at one of the inner and outer radial ends and the peak point positioned at the other as shown in Example 7.

(80) Whereas Examples 1 to 7 described above are each grasped as including the zone groups comprising three zone sequences, they can also be grasped as an item such that by the zone profile of one zone sequence (ii) having a reversed inclination, such zone is substantially eliminated. From such point of view, the phase profile described in each example can be interpreted as an item such that the zone groups comprising two zone sequences exist repeatedly in the radial direction. When objectively grasping by seeing the phase profile of Example 1 and 4 for example, it can be understood that the zone groups comprising two zone sequences arranged so as to be mutually adjacent in the radial direction are connected to each other by the connection zone having a non-blaze shape.

(81) Incidentally, in Examples 1 to 7, when the zone groups α1, α2, and α3 comprising the zone sequences (i), (ii), and (iii) are grasped, the areas of the regions of the zone groups are equal as shown in Table 16. However, the present invention does not absolutely require that the areas of the zone groups α1, α2, and α3 be equal as described.

(82) TABLE-US-00016 TABLE 16 Zone Area of radius zone r.sub.i Zone group Zone No. i (mm) group (mm.sup.2) 1 0.5225 2 0.7389 α1 2.57 3 0.9050 4 1.0450 5 1.1683 α2 2.57 6 1.2798 7 1.3824 8 1.4778 α3 2.57 9 1.5675 10 1.6523 11 1.7329 α4 2.57 12 1.8100 13 1.8839

(83) Furthermore, with the preceding examples, the entire surface of the lens substantially constitutes the optical part. However, as with a contact lens, it is also possible to suitably provide a peripheral part that does not impart an optical effect on the eye optical system, etc. in the lens outer peripheral part. Also, in the optical part as well, a diffraction grating can be provided partially only in prescribed regions in the radial direction. For example, it is also possible to provide a refractive lens at the radially inner side of the optical part, while providing a diffraction grating at the radially outer side thereof to obtain a diffractive lens, etc.

(84) It is also possible to apply the present invention to at least a portion of the region of which the diffraction grating is set in the diffractive multi-focal ophthalmic lens. For example, in a diffractive lens for which the diffractive structure is set to the entire area of the optical part, it would also be acceptable to limitedly set the adjustment zone or the connection zone according to the present invention only to the radially inner region, only to the radially outer region, or only to the region of radially middle portion. While in the present examples, the standard profile with the addition power being P=4 D is targeted, such addition power can desirably be modulated. Thus, the adjustment zone or the connection zone similar to those of the preceding examples can be set to the standard profile with the modulated addition power as well, thereby exhibiting similar effect of the invention.

(85) Yet furthermore, the phase function given by the present invention is realized by setting as a diffraction grating in the ophthalmic lens. Here, for the optical material of the ophthalmic lens for realizing the diffraction grating, it is possible to use various materials known from the past according to the desired ophthalmic lens such as contact lens, IOL, ICL, and eyeglass lenses. Also, the diffraction grating that gives the blaze shaped phase function set based on the present invention can be realized by adjusting and setting the light transmission speed in each site of the lens, for example. However, for practical use, it is preferable to realize this diffraction grating by providing a relief structure that reflects the optical path length correlating to the phase in the lens surface, for example. Alternatively, with a laminated structure lens comprising materials of different light transmission speeds (refractive index), it is also possible to set a relief structure for the boundary surface of the materials, thereby making the lens surface be smooth, or be a refracting surface, etc. (see Japanese Unexamined Patent Publication No. JP-A-2001-042112). The relief structure of the lens surface or inner surface can be formed, based on a known manufacturing method of a contact lens, IOL, ICL, etc., through a known technique of implementing chemical or mechanical surface processing such as etching, lathe turning on the optical material, for example.

(86) Moreover, whereas the adjustment zone or the connection zone according to the present invention can be set, as a specific zone profile, with the modes such as shown in FIG. 2 including a linear function expressed by preceding Equation 6, for example, such specific modes should be recognized as merely design modes. That is, the designed zone profile is provided on the optical surface of the lens by the chemical or mechanical processing technology as described above so as to obtain the ophthalmic diffractive multi-focal lens of structure according to the present invention. However, it should be understood that because of reasons of accuracy during such processing, or because of reasons of measurement accuracy if the obtained optical surface of the lens is measured, it is difficult to specifically grasp the profile of exact design. For example, it is conceivable that clear edges are difficult to be confirmed at the radially both ends of each zone, or that the radially both ends of the adjustment zone or the connection zone in particular are grasped as a mode that has no clear edge and connects to the adjacent zone with a smooth curved shape. Therefore, the actual product should be recognized as including the fact that the theoretical or design zone profile is different from the geometric shape grasped in the actual lens. Besides, even with such a case in which clear edges do not exist at the both ends of the zone profile, the technical effect of the present invention can be exhibited, thereby being included within the technical scope of the present invention.

(87) The ophthalmic lens provided with the diffraction grating imparted with the phase profile according to the present invention is adaptable to any ophthalmic lens regardless of specific types. That is, as long as the environmental condition in which the lens is used is taken into consideration, the contact lens or IOL can be understood without distinguishing each other. Besides, an ICL and eyeglass lenses can also be grasped as the examples of the present invention. Specifically, as the ophthalmic lens to which the present invention is applied, any of a contact lens, eyeglasses, an intraocular lens, etc., can be a specific subject, and also a cornea insertion lens for correcting visual power implanted intrastromally in the cornea, or an artificial cornea, etc. can be the subject. Besides, for contact lenses, it is possible to suitably apply the present invention to a hard, oxygen-permeable hard contact lens, a hydrogel or non-hydrogel soft contact lens, and also an oxygen-permeable hydrogel or non-hydrogel soft contact lens containing a silicone component, etc. Also, for intraocular lenses, it is possible to suitably apply the present invention to any intraocular lens, such as a hard intraocular lens, a soft intraocular lens that can be folded and inserted intraocularly.

(88) Here, the present inventor performed simulations in which the present invention is applied to a contact lens and an intraocular lens, in addition to the eyeglasses, and confirmed that the present invention was adaptable thereto. According to the simulations, it was possible to obtain effects similar to those of the embodiments described above. It was also confirmed that, for example, when the present invention was applied to a contact lens or an intraocular lens, by suppressing the light energy level on a specific optical axis, an effect of suppressing halo and blurred vision was achieved. If needed, such confirmation tests are easy for those skilled in the art to repeat under the conditions noted hereafter.

(89) Evaluation of Halo or the Like

(90) Evaluation of halo or the like can be performed by simulation of the point spread function. As a specific example, it can be evaluated by the diffraction profile of the present invention being provided as a relief structure on the front surface of each lens noted hereafter, the lens being inserted into the eye of a person, or a worn state being constructed by simulation, and the point spread function being calculated to check the image formed on the retina in that eye optical system. In simulation, it is possible to use VirtualLab (product name) made by LightTrans GmbH. Considering the optical system of the human eye, it is desirable that the incident light set to the simulation of the point spread function be such that, the same as with simulation of intensity distribution on the optical axis, the wavelength is 546 nm, and the light source is a point light source at an infinite distance.

(91) Simulation as an Intraocular Lens

(92) It is possible to perform simulation with respect to an implementation mode in an intraocular lens by arranging the eye optical system in sequence of the cornea, aqueous humor, iris, intraocular lens, vitreous body, and retina, and determining the refractive index and shape based on human eye data. Specifically, it is preferable to determine the refractive power of the intraocular lens and the pupil diameter as noted below.

(93) Intraocular lens 0th order diffracted light refractive power (diopter): around 20 D

(94) Pupil diameter: around 3 to 5 mm in diameter

(95) Simulation as a Contact Lens

(96) It is possible to perform simulation with respect to an implementation mode in a contact lens by arranging the eye optical system in sequence of the contact lens, cornea, aqueous humor, iris, crystalline lens, vitreous body, and retina, and determining the refractive index and shape based on human eye data. Specifically, it is preferable to determine the refractive power of the contact lens and the pupil diameter as noted below.

(97) Contact lens 0th order diffracted light refractive power (diopter): around 0 D

(98) Pupil diameter: around 3 to 5 mm in diameter

(99) The present invention is adaptable to an ophthalmic diffractive multi-focal lens giving three or more focal points. However, as will also be apparent from the preceding fifteenth mode of the present invention, it is also acceptable to provide the present invention as an ophthalmic diffractive multi-focal lens including optical characteristics such that, for example, the light energy level of one focal point among three focal points generated in the optical axis direction is reduced so that substantially two focal points are set.

(100) In addition, though not listed as individual examples, the present invention can be implemented in modes for which various changes, modifications, and improvements, etc. are made based on the knowledge of those skilled in the art, and it goes without saying that such an implementation mode is included in the scope of the present invention as long as it does not stray from the spirit of the present invention.