Lensometers and wavefront sensors and methods of measuring aberration

Abstract

Wavefront measuring systems and methods are disclosed which may be employed, for example, in detecting phase aberrations in a spectacle lens and in an eye. Various embodiments include disposing a modulation pattern in the path of a return beam from the spectacle lens or the eye, and imaging a diffraction pattern at a self-imaging plane relative to the modulation pattern with a detector. The diffraction pattern is analyzed and the results are used to produce a representation of the wavefront phase characteristics that describe aberrations in the lens or eye being measured. Illumination and processing techniques for improving the measurement results are dislcosed. Various embodiments comprise systems adaptable to both measure aberrations in lenses in spectacles as well as in a patient's eyes.

1 . A lensometer for measuring waveshaping properties of a corrective lens across at least a portion of the corrective lens, the lensometer comprising: 
 a light source for emitting light;    beam-tailoring optics that receives light from said light source and outputs a light beam having a beam size at least as large as said portion of said corrective lens to be measured, said light source, said beam-tailoring optics, and said corrective lens disposed along an optical path such that said light beam propagates through said corrective lens; and    a Talbot plane self-imaging wavefront sensor disposed in said optical path to receive said light beam after said beam has passed through said corrective lens, said Talbot plane self-imaging wavefront sensor configured for use in determining the waveshaping properties of the corrective lens.    
     
     
         2 . The lensometer of  claim 1 , wherein said beam-tailoring optics comprises a beam-expander for increasing the lateral spatial extent of the light beam.  
     
     
         3 . The lensometer of  claim 2 , wherein said beam-tailoring optics provides a beam size between about 20 to 80 millimeters across.  
     
     
         4 . The lensometer of  claim 2 , wherein said beam-tailoring optics provides a beam size between about 45 and 65 millimeters in width and 20 and 65 millimeters in height.  
     
     
         5 . The lensometer of  claim 1 , wherein said beam-tailoring optics comprises collimating optics for producing a substantially collimated beam.  
     
     
         6 . The lensometer of  claim 1 , further comprising an obstruction positioned in said optical path to produce a region on said corrective lens having reduced illumination to decrease retro-reflection from said corrective lens into said Talbot plane self-imaging wavefront sensor.  
     
     
         7 . The lensometer of  claim 6 , wherein said obstruction comprises a central obstruction in said optical path to produce a central obscuration in said light beam incident on said corrective lens.  
     
     
         8 . The lensometer of  claim 1 , further comprising null optics in said optical path.  
     
     
         9 . A method of measuring waveshaping properties of a corrective lens across at least a portion of the corrective lens, the method comprising: 
 propagating a beam through said corrective lens;    propagating said beam, having passed through said corrective lens, through at least one two-dimensional modulation pattern thereby producing a near field diffraction pattern at a Talbot plane;    imaging said near field diffraction pattern at said Talbot plane; and    determining a measure of said waveshaping properties of said corrective lens based at least in part on said near field diffraction pattern.    
     
     
         10 . The method of  claim 9 , wherein said beam has a beam size at least as large as said portion of said corrective lens to be measured.  
     
     
         11 . The method of  claim 10 , further comprising expanding said beam such that said beam size is at least as large as said portion of said corrective lens to be measured.  
     
     
         12 . The method of  claim 11 , wherein said beam is expanded so as to increase said beam width from between about 10 to 20 millimeters to between about 20 to 80 millimeters.  
     
     
         13 . The method of  claim 11 , wherein said beam is expanded prior to passing said beam through said corrective lens.  
     
     
         14 . The method of  claim 11 , wherein prior to expanding the beam, the method comprises: 
 propagating the beam through said corrective optics; and    reflecting the beam from a diffusely reflecting surface.    
     
     
         15 . The method of  claim 14 , wherein said beam is propagated through said corrective lens after said beam is expanded.  
     
     
         16 . The method of  claim 9 , further comprising collimating said beam prior to passing said beam through said corrective lens.  
     
     
         17 . The method of  claim 9 , further comprising re-shaping the corrective lens in response to said measurement of waveshaping properties.  
     
     
         18 . The method of  claim 9 , further comprising removing said corrective lens from the path of the beam and measuring an eye having a cornea, pupil, and lens.  
     
     
         19 . The method of  claim 18 , further comprising moving a lens holder holding said corrective lens in place.  
     
     
         20 . The method of  claim 18 , further comprising relocating beam expanding elements such that said beam incident on said eye is smaller than the pupil of said eye.  
     
     
         21 . The method of  claim 18 , wherein said beam is propagated through said corrective lens when said corrective lens are worn by a user such that said beam enters an eye of the user.  
     
     
         22 . The method of  claim 18 , further comprising displacing said beam laterally with respect to said eye such that light from said beam which is reflected from said cornea is deflected at an angle thereby reducing error in said measurement of said waveshaping properties of said eye.  
     
     
         23 . The method of  claim 18 , further comprising introducing a dark region in said beam, said dark region disposed with respect to said eye so as to reduce retro-reflection.  
     
     
         24 . The method of  claim 22 , wherein said beam has a substantially annular intensity cross-section.  
     
     
         25 . A combination lensometer/ocular measurement system for measuring refractive properties of an object under test selected from the group comprising a corrective lens and an eye, said measurement system comprising: 
 a light source which emits a beam of light along a first optical path to said object under test;    beam-tailoring optics which alters one or more characteristics of the beam based on whether said object under test comprises a corrective lens or an eye;    a support structure for positioning said object under test in said beam for measurement; and    a wavefront sensor disposed to receive light from said object under test for measurement of optical wavefronts received therefrom.    
     
     
         26 . The system of  claim 25 , wherein said beam-tailoring optics comprises a beam expander.  
     
     
         27 . The system of  claim 25 , wherein said support structure comprises a forehead rest.  
     
     
         28 . The system of  claim 25  wherein said support structure comprises a spectacle support for supporting spectacles.  
     
     
         29 . The system of  claim 25 , wherein said light source, said corrective lens, and said wavefront sensor are disposed in an optical path, said corrective lens being disposed in said optical path between said light source and said wavefront sensor such that light from said light beam incident on said corrective lens and reflected therefrom does not reach said Talbot self-imaging wavefront sensor.  
     
     
         30 . The system of  claim 25 , wherein said beam-tailoring optics are adjustable to facilitate measurement of the wave-shaping properties of an eye.  
     
     
         31 . The system of  claim 25 , wherein said beam-tailoring optics comprise a diffusely reflective surface and a refractive surface, said refractive surface configured to expand said beam, said diffusely reflective surface disposed with respect to said light source, said refractive surface, and said corrective lens to receive light from said light source and to reflect said light through the refracting surface and onto said corrective lens.  
     
     
         32 . The system of  claim 25 , wherein said spectacle holder is detachable to facilitate measurement of the waveshaping properties of an eye.  
     
     
         33 . A method of measuring waveshaping properties of a wavefront, said method comprising: 
 propagating said wavefront through at least one two-dimensional modulation pattern thereby producing a self-image at a self-image plane of said two-dimensional modulation pattern;    forming an image of said self-image plane;    reducing contributions from portions of said image of said self-image plane based on comparisons of a characteristic of said portions of said image with a threshold; and    determining a measure of said wavefront based at least in part on said image of said self-image plane.    
     
     
         34 . The method of  claim 33 , wherein said characteristic is intensity, said method further comprising reducing contributions from portions of said image at said self-image plane having intensity above a threshold intensity level.  
     
     
         35 . The method of  claim 34 , wherein said reducing said contributions comprises substantially removing said contributions.  
     
     
         36 . The method of  claim 33 , wherein said characteristic is intensity, said method further comprising reducing contributions from portions of said image at said self-image plane having intensity below a threshold intensity level.  
     
     
         37 . The method of  claim 33 , wherein said characteristic is signal-to-noise ratio, said method further comprising reducing contributions from portions of said image at said self-image plane having a signal-to-noise ratio below a threshold level signal-to-noise ratio.  
     
     
         38 . The method of  claim 37 , wherein said reducing said contributions comprises substantially removing said contributions.