WO1996017265A1

WO1996017265A1 - Optical lens assembly

Info

Publication number: WO1996017265A1
Application number: PCT/US1995/015188
Authority: WO
Inventors: Xiaohui Ning; Christie J. Shackelford
Original assignee: Aotec, Inc.
Priority date: 1994-11-28
Filing date: 1995-11-21
Publication date: 1996-06-06
Also published as: AU4242896A

Abstract

Lenses having diffractive features and optical systems employing such lenses are presented. In a first embodiment, an optical lens assembly comprises a housing (12), a lens (14) mounted therein, an open end, and a sized aperture (22) in the other end. The lens is bi-convex aspheric with diffractive features on both surfaces (28), (30), and performs the function otherwise requiring a plurality of lenses. The aperture accomplishes vignetting and defines the bundle size of light received by the lens. In a second embodiment, an optical assembly comprises a housing having two lenses mounted therein, and an aperture stop. Light entering the first lens passes through the aperture stop, enters the second lens and is focused by the second lens. The first lens comprises a convex spheric surface and an opposing concave aspheric surface. The second lens comprises a convex aspheric surface having diffractive features and an opposing convex aspheric surface. The invention is well suited for use with CCD cameras and other applications.

Description

OPTICAL LENS ASSEMBLY

Background of the Invention:

The present invention relates to lenses. More specifically, the present invention relates to lenses having diffractive features and optical systems employing such lenses. Optical systems employing diffractive features drastically simplify the system design, which reduces the number of components and/or improves the performance.

However, use of optical components having diffractive features in optical systems has not been widespread, primarily due to the cost of mass-producing the diffractive components.

Summary of the Invention: The above-discussed and other problems and deficiencies of the prior art are overcome or alleviated by the lenses having diffractive features of the present invention. In accordance with a first embodiment the present invention, an optical lens assembly comprises a housing having a lens mounted therein. The housing has a cylindrical (or other suitable shape depending on the application) body having one end thereof closed except for a sized aperture. The other end of the housing is open. The lens is a bi-convex aspheric lens having diffractive features on both surfaces thereof. The diffractive features are an important feature of the present invention as the lens accomplishes optical characteristics which have typically been accomplished by a plurality of lenses. The aperture is important since by its dimensions it not only defines the bundle size of light received by the lens, but also accomplishes vignetting. The accomplishment of both defining the bundle size and vignetting by the aperture is important.

In accordance with a second embodiment the present invention, an optical lens assembly comprises a housing having two lenses mounted therein. The housing has a generally cylindrical body comprising a first portion, a second inwardly tapered portion and a third portion. The housing further comprises opposing ends. The inner surface of the housing includes a series of steps and an aperture stop. Light entering the first lens, passes through the aperture stop, enters the second lens and is focused by the second lens. The first lens comprises a convex spheric surface and an opposing concave aspheric surface. The second lens comprises a convex aspheric surface having diffractive features thereon and an opposing convex aspheric surface. The present invention is particularly well suited for use with CCDs as well as other applications.

The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.

Brief Description of the Drawings:

Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:

FIGURE 1 is a cross section side elevation view of an optical lens assembly in accordance with a first embodiment of the present invention; FIGURE 2 is a partial diagrammatic side elevation view of light passing through the optical assembly of FIGURE 1;

FIGURE 3 are focus spot diagrams for the lens of the optical assembly of FIGURE 1 ; FIGURE 4 are field curvature/distortion plots for the lens at the optical assembly of FIGURE 1.

FIGURE 5 is a cross section side elevation view of an optical lens assembly in accordance with a second embodiment of the present invention; FIGURE 6 is a partial diagrammatic side elevation view of light passing through the optical assembly of FIGURE 5;

FIGURE 7 is a diagrammatic view of a charge coupled device camera optical system employing an optical lens assembly in accordance with the present invention;

FIGURE 8 is a diagrammatic view of an optical system comprising a fiber optic cable and associated interfacing optics employing an optical lens assembly in accordance with the present invention;

FIGURE 9 is a diagrammatic view of an optical storage system employing an optical lens assembly in accordance with the present invention;

FIGURE 10 is a diagrammatic view of a cathode ray tube device employing an optical lens assembly in accordance with the present invention;

FIGURE 11 is a diagrammatic view of a head mounted optical system employing an optical lens assembly in accordance with the present invention;

FIGURE 12 is a diagrammatic view of a camera employing an optical lens assembly in accordance with the present invention; FIGURE 13 is a diagrammatic view of a scanner system employing an optical lens assembly in accordance with the present invention;

FIGURE 14 is a diagrammatic view of an optical viewing device employing an optical lens assembly in accordance with the present invention;

FIGURE 15 is a diagrammatic view of an eye wear device employing an optical lens assembly in accordance with the present invention; and

FIGURE 16 is a diagrammatic view of a laser eye wear protection device employing an optical lens assembly in accordance with the present invention. Description of the Preferred Embodiment:

Referring to FIGURE 1 , an optical lens assembly in accordance with a first embodiment of the present invention is shown generally at 10. Assembly 10 comprises a housing 12 having a lens 14 mounted therein. Housing 12 has a cylindrical body portion 16 and opposing ends 18 and 20. End 18 is closed except for a sized aperture

22. Aperture 22 is an important feature of the present invention. Aperture 22 has an inside diameter and a width, which are described hereinafter. End 20 is open and includes a channel 24 extending inwardly therefrom, defining a retaining surface 26. Housing 12 is preferably comprised of an opaque plastic material. Lens 14 is a bi-convex aspheric lens having diffractive features on surfaces 28 and 30 of lens 14. Lens 14 further includes a peripheral flange 32. The diffractive features are an important feature of the present invention as lens 14 accomplishes optical characteristics which have typically been accomplished by a plurality of lenses. At least one of surfaces 28 and 30 includes an optical film coating 33 (e.g., alternating layers of low and high index of refraction material) for achieving a specific spectral response.

Lens 14 is mounted in housing 12, whereby flange 32 is disposed adjacent surface 26. A ring gasket 34 is disposed on the opposing side (i.e., opposite surface 26) of flange 32. Gasket 34 is preferably comprised of a suitable rubber material. A threaded coupling ring 36 having an annular protrusion 38 is snap fit into a groove 40 within housing 12 near end 20. Coupling ring 36 includes threads 42 for rotary coupling with another device. When inserted, ring 36 loads gasket 34 against flange 32 and thereby surface 26 to secure lens 14 within housing 12.

The distance from surface 26 to end 18 is important as this defines the distance from aperture 22 to lens 14. As mentioned briefly above, aperture 22 is important since by its dimensions, it not only defines the bundle size of light received by lens 14, but also accomplishes vignetting. Referring to FIGURE 2, by way of example, lines 48 illustrate light entering aperture 22 and focused by lens 14 at a plane 46. The ray path area exiting lens 14 is identified by lines 48 and 50 (FIGURE 1). Accordingly, when assembly 10 is used with, for example, a charge coupled device (CCD). the input plane of the CCD would be positioned at plane 46. Assembly 10 is particularly well suited for use with CCDs as well as other applications.

Lens 14 is defined by the following SAG height function for diffractive/aspheric surfaces:

AG(r) : = floor

where, r is the radial distance from the center of the lens (i.e., the optical axis of lens 14),

R is the radius of the curvature at the center of the lens, k is the conic constant,

C, is the first diffractive coefficient, n, is the index of refraction of the medium before surface 28, n₂ is the index of refraction of the medium after surface 30, and λ is the design wavelength.

It will be noted that the "floor" is a discontinuous function which returns the integer value of the argument which is nearest to zero, whereby this part of the function adds or subtracts integer multiples of λ/(n, - n₂) to form the diffractive grooves.

In accordance with a present example, the following constants for the above SAG height function were used.

Surface 28 Surface 30

R 5.63559 -4.67146

K -1.5152 -3.5829 c- -2.0710E-3 -3.297E-3

«1 1.00000 1.49358 ⁿ2 1.49358 1.00000 λ 550E-6 550E-6 In this example an acrylic with an index of refraction of 1.493 at 550nm was used. The lens achieves the following theoretical performance when used with a 1/3" format charge coupled device (CCD) sensor:

Parameter

Total Field of View (FOV) 53 deg

Effective Focal Length 6.0mm

Relative Aperture F/2

Vignetting 25% at the edge of the fi<

On-axis spot size (polychromatic using 9.0 microns photopic response weighting)

Off-axis spot size (polychromatic using 68 microns photopic response weighting) -

On-axis limiting resolution (polychromatic 65

30% MTF)

Off-axis limiting resolution (30% 25 polychromatic MTF)

On-axis polychromatic MTF @ 50 lp/mm 0.556

Off-axis polychromatic MTF @ 30 lp/mm 0.234

Maximum Geometric Distortion (Barrel) 7.4%

Further, surface 28 has 96 steps, and surface 30 has 152 steps. The spacing between these steps vary from 17 microns (at the edge of surface 30) to 515 microns (at the center of surface 28). The step height is approximately 1 micron (λ/(n-l)). The deliberate vignetting is achieved by choosing an appropriate thickness for aperture 22. The lens is well-corrected for both lateral and longitudinal chromatic aberrations. This is readily appreciated with reference to the focus spot diagrams shown in FIGURE 3 and the field curvature/distortion plots shown in FIGURE 4. The above is only exemplary, the lens could be comprised of other designs that incorporate refraction and diffraction in a single lens on at least one surface thereof.

Referring to FIGURE 5, an optical lens assembly in accordance with a second embodiment of the present invention is shown generally at 52. Assembly 52 comprises a housing 54 having lenses 56 and 58 mounted therein. Housing 54 has a generally cylindrical body comprising a first portion 60, a second inwardly tapered portion 62 and a third portion 64 having a smaller diameter than portion 60. Housing 54 further comprises opposing ends 64 and 66, with the outer surface of portion 64 including threads 68 at end 66 for rotary attachment to another device. The inner surface of housing 54 includes a step 70 for receiving lens 56 near end 64 and a step 72 for receiving lens 58 near end 66. The inner surface of housing 54 between lenses 56 and 58 (i.e., steps 70 and 72) comprises a series of steps 74 which reduce in steps the inner diameter of housing 54 and thereby the pathway of light exiting lens 56. In other words, an aperture stop 76 is defined. The inner surface of housing 54 is tapered outwardly at 78 from stop 76 to step 72 (i.e., lens 58). Housing 54 is preferably comprised of an opaque plastic material (e.g., a black acrylic). Referring to FIGURE 6, by way of example, lines 79 illustrate light entering lens 56, passing through stop 76, entering lens 58 and focused by lens 58 at a plane 81. Accordingly, when assembly 52 is used with, for example, a charge coupled device (CCD) such would be positioned at plane 81. Assembly 52 is also particularly well suited for use with CCDs as well as other applications.

Lens 56 comprises a convex spheric surface 80 and an opposing concave aspheric surface 82. Lens 56 further includes a peripheral flange 84. Lens 56 is mounted in housing 54, whereby flange 84 is disposed adjacent step 70. Lens 58 comprises a convex aspheric surface 86 having diffractive features thereon and an opposing convex aspheric surface 88. Lens 58 further includes a peripheral flange 90. Lens 58 is mounted in housing 54. whereby flange 90 is disposed adjacent step 72. At least one of surfaces 86 and 88 includes an optical film coating 91 (e.g.. alternating layers of low and high index of refraction material) for achieving a specific spectral response. Surface 86 is defined by the following SAG height function for the diffractive/aspheric surface:

__ R C . * r

AG(r) : = floor ⁿ i ^{" n}2 ⁿ i ^{_ n}2

1 - ( 1 + K ) ' — R ²

where, r is the radial distance from the center of the lens (i.e.. the optical axis of lens 58),

C, is the first diffractive coefficient, n, is the index of refraction of the medium before surface 86, n₂ is the index of refraction of the medium after surface 88, and λ is the design wavelength.

It will again be noted the "floor" is a discontinuous function which returns the integer value of the argument which is nearest to zero, whereby this part of the function adds or subtracts integer multiples of λ/(n, - n₂) to form the diffractive grooves.

In accordance with a present example the following constants for the above SAG height function were used.

Surface 86

R 7.155

K -4.109

C, -5.6463E-3 n, 1.00000 ⁿ2 1.5274 λ 550E-6

Surface 88 has a radius of 5.730 and a conic constant of -1.799. In this example an acrylic with an index of refraction of 1.493 at 550nm was used. The lens achieves the following theoretical performance when used with a 1/3" format charge coupled device (CCD) sensor:

Parameter

Total Field of View (FOV) 76.6 deg

Effective Focal Length 3.8mm

Relative Aperture F/2

Vignetting 25% at the edge of the field

On-axis spot size (polychromatic using 8.1 microns photopic response weighting)

Off-axis spot size (polychromatic using 25 microns photopic response weighting)

On-axis limiting resolution (polychromatic 125

30% MTF)

Off-axis limiting resolution (30% 45 polychromatic MTF)

On-axis polychromatic MTF @ 50 lp/mm 0.845

Off-axis polychromatic MTF @ 30 lp/mm 0.472

Maximum Geometric Distortion (Barrel) 1.63%

Surface 86 has 194 steps. The spacing between the steps at surface 86 vary from 13 microns to 364 microns. The step height is approximately 1 micron (λ/(n-l)).

By way of example, applications particularly well suited for the assemblies of the present invention include, but are not limited to the following: black/white or color CCD camera optics 100 (FIGURE 7); fiber optics 102 including associated interfacing optics for coupling, launching and detection (FIGURE 8); optical storage 104 including video, audio and data; more particularly in the read-out head 106 thereof (FIGURE 9); head mounted optics 1 14 such as virtual reality optics, projection optics, viewing optics and heads-up display (FIGURE 11 ); camera optics 1 16 such as cameras, camcorders and VCR cameras, more particularly in the active and viewing optics thereof (FIGURE 12); scanners 118 such as scanning optics, light pens such as used with computers, imaging optics, and lens arrays (FIGURE 13); eye pieces for optical devices such as night vision scopes, binoculars, telescopes and riflescopes, collectively, viewing device

120 (FIGURE 14); ophthalmic lenses such as progressive power with diffractive optics and bifocals, collectively, eye wear 122 (FIGURE 15); and laser eye protection 124 such as concentrator and dispersive optics (FIGURE 16). It will be appreciated that several of the above systems do not include the housing, but only the lens having diffractive features, e.g., eye wear.

The above is only exemplary, the lens could be comprised of other designs that incorporate refraction and diffraction in a single lens on at least one surface thereof.

While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.

What is claimed is:

Claims

CLAIM 1. An optical assembly comprising: a housing having an aperture at one end thereof for receiving light into said housing, said aperture defining both light bundle size and vignetting; and a lens having a plurality of diffractive features on at least one surface thereof, said lens disposed within said housing, said lens for focusing light received from said aperture.

CLAIM 2. The optical assembly of claim 1 wherein said lens is comprised of an optical grade plastic.

CLAIM 3. The optical assembly of claim 2 wherein said plastic comprises an acrylic.

CLAIM 4. The optical assembly of claim 1 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 5. The optical assembly of claim 1 wherein said diffractive features comprise diffractive features suitable for imaging.

CLAIM 6. The optical assembly of claim 1 wherein said lens further includes at least one surface thereof having a refractive feature.

CLAIM 7. The optical assembly of claim 1 wherein said lens comprising features defined by the following algorithm:

__

C , * r ²

AG(r) : R floor n , - n₂ ⁿ ι ^{_ n}2

1 + ( 1 ₊ K ) * -L- R ²

where, r is the radial distance from a center of said lens,

R is the radius of the curvature at the center of said lens, k is a conic constant,

C, is a first diffractive coefficient, n, is an index of refraction of a medium before one surface at said lens, n_: is the index of refraction of a medium after another surface of said lens, and λ is the design wavelength.

CLAIM 8. The optical assembly of claim 1 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 9. The optical assembly of claim 1 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 10. The optical assembly of claim 1 wherein said housing is comprised of an opaque material.

CLAIM 11. The optical assembly of claim 1 wherein said at least one surface of said lens includes an optical film coating thereon.

CLAIM 12. An optical assembly comprising: a housing having an aperture stop defined therein for defining light bundle size; a first lens disposed at one end of said housing for receiving light into said housing and projecting light through said aperture stop; and a second lens having a plurality of diffractive features on one surface thereof, said lens disposed within said housing, said lens for focusing light received from said aperture stop.

CLAIM 13. The optical assembly of claim 12 wherein said first and second lenses are comprised of an optical grade plastic.

CLAIM 14. The optical assembly of claim 13 wherein said plastic comprises an acrylic.

CLAIM 15. The optical assembly of claim 12 wherein said diffractive features comprises diffractive features suitable for imaging.

CLAIM 16. The optical assembly of claim 12 wherein said second lens further includes at least one surface thereof having a refractive feature.

CLAIM 17. The optical assembly of claim 12 wherein said second lens comprises features defined by the following algorithm:

R C . T

AG(r) : floor n , - n₂ n , n.

1 - O ₊ K )

R

where, r is the radial distance from a center of said second lens,

R is the radius of the curvature at the center of said second lens, k is a conic constant,

C, is a first diffractive coefficient, n, is an index of refraction of a medium before one surface at said second lens, n₂ is the index of refraction of a medium after another surface of said second lens, and λ is the design wavelength.

CLAIM 18. The optical assembly of claim 12 wherein said second lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 19. The optical assembly of claim 12 wherein said first lens comprises a convex spheric surface and an opposing concave aspheric surface.

CLAIM 20. The optical assembly of claim 12 wherein said second lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 21. The optical assembly of claim 12 wherein said housing is comprised of an opaque material.

CLAIM 22. The optical assembly of claim 12 wherein said at least one surface of said second lens includes an optical film coating thereon.

CLAIM 23. A charge coupled device camera optical system having optics for focusing an image onto the charge coupled device, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features suitable for imaging in at least one surface thereof.

CLAIM 24. The system of claim 23 wherein said lens is comprised of an optical grade plastic.

CLAIM 25. The system of claim 24 wherein said plastic comprises an acrylic.

CLAIM 26. The system of claim 23 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 27. The system of claim 23 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 28. The system of claim 23 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 29. An optical system comprising a fiber optic cable and associated interfacing optics, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 30. The system of claim 29 wherein said lens is comprised of an optical grade plastic.

CLAIM 31. The system of claim 30 wherein said plastic comprises an acrylic.

CLAIM 32. The system of claim 29 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 33. The system of claim 29 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 34. The system of claim 29 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 35. An optical storage system including a read-out head having optics, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 36. The system of claim 35 wherein said lens is comprised of an optical grade plastic.

CLAIM 37. The system of claim 36 wherein said plastic comprises an acrylic.

CLAIM 38. The system of claim 35 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 39. The system of claim 35 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 40. The system of claim 35 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features. -17-

CLAIM 41. A cathode ray tube device having projection optics, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features suitable for imaging in at least one surface thereof.

CLAIM 42. The device of claim 41 wherein said lens is comprised of an optical grade plastic.

CLAIM 43. The device of claim 42 wherein said plastic comprises an acrylic.

CLAIM 44. The device of claim 41 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 45. The device of claim 41 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 46. The device of claim 41 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 47. A head mounted optical system having optics, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 48. The system of claim 47 wherein said lens is comprised of an optical grade plastic.

CLAIM 49. The system of claim 48 wherein said plastic comprises an acrylic.

CLAIM 50. The system of claim 47 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 51. The system of claim 47 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 52. The system of claim 47 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 53. A camera having optics, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 54. The camera of claim 53 wherein said lens is comprised of an optical grade plastic.

CLAIM 55. The camera of claim 54 wherein said plastic comprises an acrylic.

CLAIM 56. The camera of claim 53 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 57. The camera of claim 53 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 58. The camera of claim 53 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 59. A scanner system having optics, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 60. The system of claim 59 wherein said lens is comprised of an optical grade plastic.

CLAIM 61. The system of claim 60 wherein said plastic comprises an acrylic.

CLAIM 62. The system of claim 59 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 63. The system of claim 59 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 64. The system of claim 59 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 65. An optical viewing device having eye piece optics, wherein the improvement comprises: said optics including a lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 66. The device of claim 65 wherein said lens is comprised of an optical grade plastic.

CLAIM 67. The device of claim 66 wherein said plastic comprises an acrylic.

CLAIM 68. The device of claim 65 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 69. The device of claim 65 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 70. The device of claim 65 wherein said lens comprises a molded lens and said diffractive features comprise molded diffractive features.

CLAIM 71. An eye wear device having at least one ophthalmic lens, wherein the improvement comprises: said ophthalmic lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 72. The device of claim 71 wherein said lens is comprised of an optical grade plastic.

CLAIM 73. The device of claim 72 wherein said plastic comprises an acrylic.

CLAIM 74. The device of claim 71 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 75. The device of claim 71 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 76. The device of claim 71 wherein each of said lenses comprises a molded lens with said diffractive features comprising molded diffractive features.

CLAIM 77. A laser eye wear protection device having at least one lens, wherein the improvement comprises: said lens having a plurality of diffractive features in at least one surface thereof.

CLAIM 78. The device of claim 77 wherein said lens is comprised of an optical grade plastic.

CLAIM 79. The device of claim 78 wherein said plastic comprises an acrylic.

CLAIM 80. The device of claim 77 wherein said at least one surface comprises two opposing surfaces of said lens.

CLAIM 81. The device of claim 77 wherein said lens is bi-convex aspheric with said diffractive features in at least one surface thereof.

CLAIM 82. The device of claim 77 wherein said lens comprises a molded lens with said diffractive features comprising molded diffractive features.