System and methods for measuring ophthalmic lens

Abstract

The system and methods are made to apply interferometry to ophthalmic applications. The system makes use of a low-coherence interferometer to obtain a plurality of measurements of a contacts lens. The system and methods characterizes the surface profile of both surfaces of a contact lens, a thickness profiles, and combines these measurements with an index information to reconstruct a complete model of the contact lens.

What is claimed is: 
     
         1 . A system for characterizing the surface properties of one or both surfaces of a contact lens, the system comprising:
 an optics assembly including a light source configured to generate a low coherence light beam;   a beam splitter configured to create a first light beam and a second light beam from the light beam generated by the optics assembly;   a diverger assembly including at least one lens configured to propagate the first light beam;   a measurement assembly configured to house the contact lens and receive the first light beam from said diverger assembly and direct the first light beam to at least one contact lens surface, the at least one contact lens surface creating a first reflected light beam and said measurement assembly being configured to direct the first reflected light beam towards said beam splitter;   a reference assembly configured to receive the second light beam and direct a second reflected light beam to said beam splitter to provide a wavefront reference for measuring the contact lens; and   an imaging assembly, and   wherein said beam splitter being configured to merge the first reflected light beam and the second reflected light beam into a combined light beam and directing the combined light beam to said imaging assembly, and   said imaging assembly configured to receive the combined light beam from said beam splitter and create an image with an interference pattern from the combined light beam.   
     
     
         2 . The system of  claim 1 , wherein said measurement assembly includes:
 a cuvette configured to hold the contact lens to be characterized;   a distance measuring device; and   a controller that moves the contact lens to multiple positions in the measurement assembly and for controlling the path length through said reference assembly based on at least the location of the contact lens as provided by said distance measuring device.   
     
     
         3 . The system of  claim 2 , wherein
 said distance measuring device is configured to track a plurality of positions of the contact lens, and   said controller configured to calculate the distances between the confocal measurement position and cat's eye focal measurement position based on position signals received from said distance measuring device.   
     
     
         4 . The system of  claim 1 , wherein a said beam splitter includes at least one of a polarizing beam splitter, plate beam splitter, and a cube beam splitter. 
     
     
         5 . The system of  claim 1 , wherein said measurement assembly includes:
 a mounting structure having a ring configured to mount said contact lens into a position for receiving of the first light beam; and   a cuvette containing at least one chamber configured to be filled with fluid into which the contact lens and said mounting structure are placed during characterization of the contact lens.   
     
     
         6 . The system of  claim 1 , wherein said reference assembly includes:
 a reference prism configured to match the optical path lengths and material dispersions of the second light beam to the optical path lengths and material dispersions of the first light beam passing through said diverger assembly and said measurement assembly;   a tank configured to be filled with fluid such that at least part of said the reference prism is submerged into the fluid; and   a reference tank window configured to provide shifting motion of the second light beam to balance the motion of the contact lens in the fluid filled cuvette, and wherein said reference prism causes the second light beam to pass through said reference prism and return back at least part of the second light beam through the fluid in said tank to said beam splitter.   
     
     
         7 . The system of  claim 1 , wherein said imaging assembly is configured to collect the surface properties of the at least one contact lens surface from at least one of at least one cat's eye focal measurement position and at least one confocal measurement position. 
     
     
         8 . The system of  claim 1 , further comprising a computer-implemented device configured to use optical modeling to compensate for the refraction that occurs at a first face of the contact lens when measuring a subsequent surface, and
 wherein said imaging assembly is configured to collect the surface properties of the contact lens on the subsequent face of the contact lens from at least one of an optical cat's eye focal measurement position and an optical confocal measurement position.   
     
     
         9 . The system of  claim 1 , wherein said imaging assembly including a processor configured to execute a program for calculating a number of measurements of at least one of
 the at least one contact lens surface and   at least one thickness of the contact lens.   
     
     
         10 . The system of  claim 1 , wherein said reference assembly includes at least one member having a phase-shifting surface. 
     
     
         11 . The system of  claim 1 , wherein said measurement assembly is configured to provide a measurement wavefront to the at least one contact lens surface by propagating the first light beam to the at least one contact lens surface and returning the first reflected light beam towards said beam splitter. 
     
     
         12 . A method for producing a whole lens reconstruction of a contact lens, the method comprising:
 moving at least one contact lens through a series of positions, each position relates to a plurality of contact lens surfaces; and   adjusting a submersion depth of a reference prism to match a path length for at least one contact lens position,   for each contact lens position:
 generating a planar low coherence light beam from a light source, 
 splitting the generated light beam by a beam splitter into a first light beam and a second light beam, 
 propagating the first light beam to a measurement assembly, the measurement assembly directing the first light beam onto a contact lens surface which reflects at least part of the first light beam back to the beam splitter as a first reflected light beam, 
 propagating the second light beam to a reference assembly, the reference assembly reflecting at least part of the second light beam to the beam splitter as a second reflected light beam to provide a wavefront reference for measuring the contact lens, 
 merging the first reflected light beam and the second reflected light beam by the beam splitter to form a combined light beam, and 
 said beam splitter directing the combined light beam to an imaging assembly, the imaging assembly focusing the combined light beam to form an optical image of the contact lens containing an interference pattern; 
   correcting at least one optical image for any refractions that are present from one surface of the contact lens that arise during measurement when the light beam passes through the one surface to reach another surface of the contact lens; and   producing a whole lens reconstruction based on the plurality of optical images of the contact lens, and   wherein the whole lens reconstruction includes at least one thickness of the contact lens and surface properties of the plurality of surfaces of the contact lens.   
     
     
         13 . The method of  claim 12 , wherein the positions include:
 a confocal measurement position for each surface of the contact lens; and   a cat's eye measurement position for each surface of the contact lens.   
     
     
         14 . The method of  claim 13 , further comprising calculating the at least one thickness of the contact lens between opposing surfaces of the contact lens. 
     
     
         15 . The method of  claim 14 , further comprising calculating the at least one thickness profile of the contact lens based upon the at least one thickness and the surface properties of the opposing surfaces of the contact lens. 
     
     
         16 . The method of  claim 15 , further comprising calculating a transmitted wavefront map of the contact lens based upon all of the thickness profiles of the contact lens and respective values for an index of refraction of the thickness profiles. 
     
     
         17 . The method of  claim 12 , wherein
 the plurality of surfaces of the contact lens includes a first surface and a second surface; and   the positions include: a confocal measurement position for the first surface and the second surface, and a cat's eye measurement position for the first surface and the second surface, and   the method further comprising:
 calculating the thickness of the contact lens between the first surface and the second surface; and 
 calculating the thickness profile of the contact lens based upon the thickness and the surface properties of the first surface and the second surface. 
   
     
     
         18 . The method of  claim 12 , further comprising creating at least one simulated whole lens reconstruction with a processor using calculated measurements of at least one surface of the contact lens and the thickness profile of the contact lens obtained from a separate measurement. 
     
     
         19 . The method of  claim 12 , further comprising creating at least one simulated whole lens reconstruction with a processor using calculated measurements of at least one of
 one surface of the at the plurality of contact lens surfaces,   a transmitted wavefront map of the contact lens obtained from a separate measurement, and   an index of refraction of the contact lens.   
     
     
         20 . A method for simulating a whole lens reconstruction, the method comprising:
 generating a light beam from an optics assembly, wherein said optics assembly includes a light source to generate a low coherence light beam, and at least one collimation lens configured to provide the light beam with a planar wavefront;   splitting the light beam with a beam splitter into a first light beam and a second light beam;   propagating the first light beam to a measurement assembly, wherein the measurement assembly includes a cuvette containing at least one chamber filled with fluid in which a contact lens sits, and a mounting structure on which the contact lens is placed into a position for receiving of the first light beam, the measurement assembly directing the first light beam onto a contact lens surface to cause return of a first reflected light beam back towards the beam splitter;   propagating the second light beam to a reference assembly, wherein the reference assembly includes a reference prism configured to match the optical path lengths and material dispersions of the second light beam to the optical path lengths and material dispersions of the first beam in said measurement assembly, a tank filled with fluid and configured to at least partially submerge the reference prism into, and a reference tank window configured to provide shifting motion of the second light beam to balance the motion of the contact lens in the fluid filled cuvette, and wherein the reference prism causes the second light beam to pass through the reference prism and return a second reflected light beam through the fluid in the tank to the beam splitter;   combining the first reflected light beam and the second reflected light beam with the beam splitter to form a combined light beam;   directing the combined light beam from the beam splitter to an imaging assembly having a detector, wherein the imaging assembly detecting with the detector at least one fringe pattern of said combined light beam and interference patterns of said combined light beam to form an optical image of the contact lens;   moving the contact lens held in the cuvette through a series of measurement positions to provide a plurality of optical images to be detected by the imaging assembly;   correcting at least one optical image for any refractions that are present from another surface of the contact lens that arise during measurement; and   producing a whole lens reconstruction based on the plurality of optical images of the contact lens, and   wherein the whole lens reconstruction includes the at least one thickness of the contact lens and surface properties of the plurality of contact lens surfaces.