Inspection of ophthalmic lenses using absorption

Abstract

A method and system for inspecting ophthalmic lenses using absorption where an ophthalmic lens is illuminated with light comprising wavelengths that are substantially absorptive to said lens, the image subsequently detected being created using only light at said absorptive wavelengths. Variations in transmitted light intensity translate into thickness changes in the lens caused by cosmetic flaws. The invention is also directed to imaging lens assemblies employing highly positive-powered field flattening lens elements to image a curved object, such as an ophthalmic lens, onto a flat image plane.

What is claimed is:  
     
         1 . A method for inspecting an ophthalmic lens which comprises: 
 (a) illuminating an ophthalmic lens with light comprising a wavelength substantially absorptive to said lens;    (b) detecting an image of at least part of said ophthalmic lens only from light that is at said substantially absorptive wavelength which has been transmitted through said ophthalmic lens; and    (c) analyzing said image for changes in intensity of the light that is at said wavelength and that has been transmitted through said ophthalmic lens, said changes in intensity caused by changes in thickness of said ophthalmic lens.    
     
     
         2 . The method of  claim 1  wherein the changes in thickness of said ophthalmic lens are caused by cosmetic defects.  
     
     
         3 . The method of  claim 1  wherein the changes in thickness of said ophthalmic lens are designed into said lens.  
     
     
         4 . The method of  claim 3  wherein said changes in thickness designed into said lens are toric thin zones.  
     
     
         5 . The method of  claim 1  wherein said wavelength is at least 75% absorbed by said lens at the thickest part thereof.  
     
     
         6 . The method of  claim 5  wherein said wavelength is at least 85% absorbed by said lens at the thickest part thereof.  
     
     
         7 . The method of  claim 6  wherein said wavelength is at least 90% absorbed by said lens at the thickest part thereof.  
     
     
         8 . The method of  claim 7  wherein said wavelength is at least 95% absorbed by said lens at the thickest part thereof.  
     
     
         9 . The method of  claim 1  wherein said wavelength is up to about 400 nm.  
     
     
         10 . The method of  claim 9  wherein said wavelength is about 320 nm to about 355 nm.  
     
     
         11 . The method of  claim 1  wherein said wavelength is at least about 700 nm.  
     
     
         12 . The method of  claim 11  wherein said wavelength is about 700 nm to about 1000 nm.  
     
     
         13 . The method of  claim 1  wherein the light that illuminates said lens in step (a) consists essentially of said substantially absorptive wavelength.  
     
     
         14 . The method of  claim 13  wherein said light is obtained from a light source filtered to provide said substantially absorptive wavelength.  
     
     
         15 . The method of  claim 13  wherein said light is provided by a laser operating at said substantially absorptive wavelength.  
     
     
         16 . The method of  claim 1  wherein said ophthalmic lens is formed in a mold and the illuminating step (a) occurs while said lens is in at least part of said mold, said mold being substantially transparent to said wavelength.  
     
     
         17 . The method of  claim 1  wherein the illuminating step (a) occurs when said ophthalmic lens is in its final packaging.  
     
     
         18 . The method of  claim 1  wherein the ophthalmic lens has a convex surface and the light in step (a) illuminates the convex surface of said ophthalmic lens at an angle of incidence that is substantially normal to said convex surface.  
     
     
         19 . The method of  claim 1  wherein the ophthalmic lens has a concave surface and the light in step (a) illuminates the concave surface of said ophthalmic lens at an angle of incidence that is substantially normal to said concave surface.  
     
     
         20 . The method of  claim 1  wherein the ophthalmic lens has a concave surface and detecting step (b) employs an imaging lens assembly having a curved focal surface.  
     
     
         21 . The method of  claim 20  wherein said curved focal surface has a curvature substantially equal to the average curvature of the concave surface of the ophthalmic lens being illuminated.  
     
     
         22 . A method for inspecting an ophthalmic lens which comprises: 
 (a) providing light consisting essentially of one or more wavelengths up to about 400 nm;    (b) illuminating, with said light, an ophthalmic lens;    (c) detecting, with light that has been transmitted through said ophthalmic lens, an image of at least part of said ophthalmic lens; and    (d) analyzing said image for changes in intensity of the light that has been transmitted through said ophthalmic lens, said changes in intensity caused by changes in thickness of said ophthalmic lens.    
     
     
         23 . The method of  claim 22  wherein said changes in thickness are caused by cosmetic flaws.  
     
     
         24 . The method of  claim 22  wherein said changes in thickness are designed into said ophthalmic lens.  
     
     
         25 . The method of  claim 24  wherein said changes in thickness designed into the ophthalmic lens are toric thin zones.  
     
     
         26 . The method of  claim 22  wherein the light of step (a) is from a light source that has been filtered sufficient to provide light at said wavelength.  
     
     
         27 . The method of  claim 26  wherein said light is at a wavelength of about 280 nm to about 360 nm.  
     
     
         28 . A method for inspecting an ophthalmic lens which comprises: 
 (a) providing light from a laser operating at a wavelength up to about 400 nm;    (b) illuminating, with said light, an ophthalmic lens;    (c) detecting, with light that has been transmitted through said ophthalmic lens, an image of at least part of said lens; and    (d) analyzing said image for changes in intensity of the light that has been transmitted through said ophthalmic lens, said changes in intensity caused by changes in thickness of said ophthalmic lens.    
     
     
         29 . The method of  claim 28  wherein said changes in thickness are caused by cosmetic flaws.  
     
     
         30 . The method of  claim 28  wherein said changes in thickness are designed into said ophthalmic lens.  
     
     
         31 . The method of  claim 30  wherein said changes in thickness designed into said ophthalmic lens are toric thin zones.  
     
     
         32 . The method of  claim 28  wherein said wavelength is about 355 nm.  
     
     
         33 . The method of  claim 28  wherein said ophthalmic lens has a convex surface said convex surface being illuminated in illuminating step (b), said light in step (b) illuminating said convex surface at an angle of incidence that is substantially normal over the entirety of said convex surface.  
     
     
         34 . The method of  claim 28  wherein said ophthalmic lens has a concave surface, said concave surface being illuminated in illuminating step (b), said light in step (b) illuminating said concave surface at an angle of incidence that is substantially normal over the entirety of said concave surface.  
     
     
         35 . A system for inspecting an ophthalmic lens which comprises: 
 (a) an illumination subsystem to generate light and to direct said light through an ophthalmic lens at an inspection position, said light comprising a wavelength substantially absorptive to said ophthalmic lens;    (b) an imaging subsystem to detect an image of at least part of said ophthalmic lens from only light that is at said wavelength which has been transmitted through said ophthalmic lens; and    (c) an image processing subsystem to analyze said image for changes in intensity of the light that is at said wavelength and that has been transmitted through said ophthalmic lens, said changes in intensity caused by changes in thickness of said ophthalmic lens.    
     
     
         36 . The method of  claim 35  wherein the changes in thickness are caused by cosmetic flaws.  
     
     
         37 . The method of  claim 35  wherein the changes in thickness are designed into said ophthalmic lens.  
     
     
         38 . The method of  claim 37  wherein said changes in thickness designed into said lens are toric thin zones.  
     
     
         39 . The system of  claim 35  wherein said illumination subsystem (a) comprises a light source that is filtered to provide light consisting essentially of said wavelength prior to directing said light through said ophthalmic lens.  
     
     
         40 . The system of  claim 35  wherein said imaging subsystem (b) comprises a camera having a spectral response to said wavelength and an imaging lens assembly that transmits said wavelength.  
     
     
         41 . The system of  claim 35  further comprising a filtering subsystem located after said inspection position to filter light that has been directed through said ophthalmic lens to light consisting essentially of said wavelength.  
     
     
         42 . The system of  claim 35  wherein said illumination subsystem (a) comprises a laser light source providing a laser light beam at said wavelength.  
     
     
         43 . The system of  claim 42  wherein said illumination subsystem further comprises a beam expander component and an apodizing component located in the path of said laser light beam.  
     
     
         44 . The system of  claim 43  wherein said apodizer produces a bull's eye pattern from said laser light beam.  
     
     
         45 . The system of  claim 44  wherein said apodizer has a central area, a middle area, and a peripheral area, and wherein said middle area has an optical density to said laser light about 10 times greater than the optical density of said central area, and wherein said peripheral area has an optical density to said laser light about 10 times greater than that for the middle area.  
     
     
         46 . The system of  claim 45  wherein said apodizer further comprises an annular area interposed between said central area and said middle area, said annular area having an optical density about 10 times less that said central area.  
     
     
         47 . The system of  claim 44  wherein said apodizer is comprised of a diffractive holographic element.  
     
     
         48 . An apodizer comprising substantially concentric circles of differing optical densities, said apodizer having a central circular area, a first annular area surrounding and concentric with said central area, a second annular area surrounding and concentric with said first annular area, and an third annular area surrounding and concentric with said second annular area; the optical density of said first annular area being less than the optical density of said central circular area, the optical density of said second annular area being greater than the optical density of said central circular area, and the optical density of the third annular area being greater than the optical density of the second annular area.  
     
     
         49 . The apodizer of  claim 48  wherein said optical density of said second annular area is about 10 times greater than the optical density of said central circular area; said optical density of said third annular area is about 10 times greater that said second annular area, and the optical density of said first annular area is about 10 times less than the optical density of said central circular area.  
     
     
         50 . A lens assembly for imaging an object having a curved surface onto a flat imaging plane wherein said curved surface is curved concave toward said assembly, and said object is illuminated such that illuminating light is transmitted through said object to exit from said curved surface as divergent light, which comprises: 
 (a) a relay lens element to converge the divergent light exiting from said curved surface of said object; and    (b) a field flattening lens element having a positive power to focus light transmitted by said relay lens element onto said flat imaging plane.    
     
     
         51 . The lens assembly of  claim 50  wherein said field flattening lens element has a focal length of about 5 mm to about 100 mm.  
     
     
         52 . The lens assembly of  claim 51  wherein said focal length is about 10 mm to about 50 mm.  
     
     
         53 . The lens assembly of  claim 52  wherein said focal length is about 20 mm.  
     
     
         54 . The lens assembly of  claim 50  wherein said object having said curved surface is spherical or aspherical.  
     
     
         55 . The lens assembly of  claim 50  wherein said object having said curved surface is an ophthalmic lens.  
     
     
         56 . The lens assembly of  claim 50  further comprising an aperture stop interposed between said object and said relay lens element.  
     
     
         57 . A lens assembly for imaging an object having a curved surface onto a flat imaging plane wherein said curved surface is curved concave toward said lens assembly, and said object is illuminated such that illuminating light is transmitted through said object to exit from said curved surface as divergent light, which comprises: 
 (a) a first relay lens element to converge the divergent light exiting from said curved surface of said object;    (b) a field lens element having a field of view of said first relay lens element, said field lens element to collect light transmitted by said first relay lens element at the periphery of said field of view, and to focus light transmitted by said first relay lens element to form a first image of said object at a first image plane, light transmitted by said field lens element being divergent aft of said first image plane;    (c) a second relay lens element to partially collimate the divergent light aft of said first image plane; and    (d) a field flattening lens element that has a positive power to focus the partially collimated light transmitted by said second relay lens element onto said flat imaging plane.    
     
     
         58 . The lens assembly of  claim 57  wherein said first relay lens element comprises a first lens component upon which the divergent light exiting from said curved surface of said object is incident, said first lens component to converge said divergent incident light, and a second lens component having an aspherical surface, said second lens component to correct aberrations in light transmitted by said first lens component, said light transmitted by said first lens component being incident on said aspherical surface.  
     
     
         59 . The lens assembly of  claim 58  wherein said field lens element comprises first and second planoconvex lenses.  
     
     
         60 . The lens assembly of  claim 57  further comprising an optical filter interposed between said positively powered lens element and said flat imaging plane.  
     
     
         61 . The lens assembly of  claim 57  wherein said field flattening lens element is comprised of a first positively powered lens component forward of a second positively powered lens component, said second positively powered lens component being forward of said flat imaging plane and having a focal length of about 5 mm to about 100 mm.  
     
     
         62 . The lens assembly of  claim 61  wherein said second positively powered lens component has a focal length of about 10 mm to about 50 mm.  
     
     
         63 . The lens assembly of  claim 62  wherein said second positively powered lens component has a focal length of about 20 mm.  
     
     
         64 . The lens assembly of  claim 57  wherein said first relay lens element is at least 30 mm from said object.  
     
     
         65 . The lens assembly of  claim 57  wherein said object having said curved surface is spherical or aspherical.  
     
     
         66 . The lens assembly of  claim 57  wherein said object is an ophthalmic lens.  
     
     
         67 . A lens assembly for imaging an object having a curved surface onto a flat imaging plane wherein said curved surface is curved concave toward said assembly, and said object is illuminated, the illumination light being transmitted through said object and exiting from said curved surface as divergent light, which assembly comprises: 
 (a) a relay lens element interposed between first and second corrective lens elements, said relay lens element to converge the divergent light exiting said curved surface of said object;    (b) a field flattening lens element having a positive power to focus light transmitted by said relay lens onto said flat imaging plane.    
     
     
         68 . The lens assembly of  claim 67  wherein said first and second corrective lens elements have meniscus curved shapes which can be the same or different.  
     
     
         69 . The lens assembly of  claim 67  wherein said relay lens element is comprised of two or more lens components.  
     
     
         70 . The lens assembly of  claim 67  wherein said field flattening lens element is comprised of first, second and third positively powered lens components arranged in series, said third component being forward of said flat imaging plane and having a focal length of about 5 mm to about 100 mm.  
     
     
         71 . The lens assembly of  claim 67  wherein said focal length is about 10 mm to about 50 mm.  
     
     
         72 . The lens assembly of  claim 71  wherein said focal length is about 20 mm.  
     
     
         73 . The lens assembly of  claim 67  further comprising an aperture stop interposed between said relay lens element and said second corrective lens element.  
     
     
         74 . The lens assembly of  claim 67  further comprising an optical filter interposed between said field flattening lens element and said flat imaging plane.  
     
     
         75 . The lens assembly of  claim 67  wherein said first corrective astigmatic lens is at a distance of less than 30 mm to said object.  
     
     
         76 . The lens assembly of  claim 67  wherein said object is spherical or aspherical.  
     
     
         77 . The lens assembly of  claim 67  wherein said object is an ophthalmic lens.  
     
     
         78 . A lens assembly for imaging an object having a curved surface onto a flat imaging plane wherein said curved surface is immersed in an aqueous fluid and is curved concave toward said assembly, and said object is illuminated such that illuminating light is transmitted through said object to exit from said curved surface and said fluid as divergent light, which comprises: 
 (a) a refractive lens element onto which said divergent light exiting from said curved surface and said fluid is incident, said refractive lens to direct said light onto a relay lens element to converge said divergent light; and    (b) a field flattening lens element having a positive power to focus light transmitted through said rely lens element onto said flat image plane.    
     
     
         79 . The lens assembly of  claim 78  wherein said relay lens assembly is a doublet comprising a concave lens component of negative power having a first index value and a first dispersion value, said concave lens cemented to a positive lens component having a second index value and a second dispersion value, said second index value being lower than said first index value and said second dispersion value being lower that said first dispersion value.  
     
     
         80 . The lens assembly of  claim 78  further comprising an optical filter interposed between said field flattening lens element and said flat image plane, and a faceplate interposed between said optical filter and said flat image plane.  
     
     
         81 . The lens assembly of  claim 78  wherein said object is spherical or aspherical.  
     
     
         82 . The lens assembly of  claim 78  wherein said object is an opthalmic lens.  
     
     
         83 . The lens assembly of  claim 78  wherein said fluid is water or saline solution.  
     
     
         84 . An ophthalmic lens inspection carrier comprising a pallet having a top surface and a bottom surface and at least one well for receiving an ophthalmic lens container, said well extending through said pallet and having a frustroconical shape the divergent end of which is situated at said bottom surface and the sides of said well form an angle of between about 35° and about 55° relative to said bottom surface.  
     
     
         85 . The carrier of  claim 84  wherein said angle is about 45°.  
     
     
         86 . The carrier of  claim 84  wherein the sides of said well have been bead blasted.  
     
     
         87 . An ophthalmic lens inspection carrier assembly comprising a pallet having a top surface and a bottom surface and at least one well for receiving an ophthalmic lens container, said well extending through said pallet and having a frustoconical shape the divergent end of which is situated at said bottom surface and the sides of said well form an angle of between about 35° and 55° relative to said bottom surface; and a lens container inserted into said well from the top surface of said pallet.  
     
     
         88 . The assembly of  claim 87  further comprising an ophthalmic lens within said lens container, said ophthalmic lens having a convex surface which convex surface faces the bottom surface of said pallet.  
     
     
         89 . The assembly of  claim 87  wherein said angle is about 45°.  
     
     
         90 . The assembly of  claim 87  wherein the sides of said well have been bead blasted.  
     
     
         91 . A lens assembly for directing light onto a convex surface at an angle of incidence substantially normal over said surface which comprises: 
 (a) a field lens element to diverge and aim diffuse light at a relay lens element, said relay lens element acting to at least partially collimate said light and direct said substantially collimated light to said convex surface; and    (b) a focusing lens group interposed between said relay lens element and said convex surface, said focusing lens group comprised of a plurality of lens elements to converge and relay said at least partially collimated light to said convex surface at an angle of incidence substantially normal over said surface.    
     
     
         92 . The lens assembly of  claim 91  wherein said plurality of lens elements, in order from said relay lens element, is comprised of at least a planoconvex lens and first and second meniscus lenses.  
     
     
         93 . The lens assembly of  claim 92  wherein said first and second meniscus lenses are substantially identical.  
     
     
         94 . The lens assembly of  claim 91  wherein said convex surface is on an ophthalmic lens.  
     
     
         95 . A lens assembly for directing illuminating light onto a convex surface such that said illuminating light strikes said convex surface at an angle of incidence substantially normal to said convex surface which comprises a planoconvex field lens to diverge and aim diffuse illuminating light at a equiconvex relay lens to partially collimate and direct said light partially collimated light to said convex surface, and a focusing lens group interposed between said relay lens and said convex surface, said focusing lens group comprised of, in order from said relay lens, a planoconvex lens and first and second meniscus lenses to converge and relay said partially collimated light to said convex surface at an angle of incidence substantially normal to said convex surface.