System for detecting anomalies and/or features of a surface

Abstract

A cylindrical mirror or lens is used to focus an input collimated beam of light onto a line on the surface to be inspected, where the line is substantially in the plane of incidence of the focused beam. An image of the beam is projected onto an array of charge-coupled devices parallel to the line for detecting anomalies and/or features of the surface, where the array is outside the plane of incidence of the focused beam.

What is claimed is:  
     
         1 . A method for detecting anomalies and/or features of a surface, comprising: 
 focusing a beam of radiation at an oblique incidence angle to illuminate a line on the surface, said beam and a direction through the beam and normal to the surface defining an incidence plane of the beam, said line being substantially in the plane of incidence of the beam; and    imaging said line onto an array of detectors, each detector in the array detecting light from a corresponding portion of the line.    
     
     
         2 . The method of  claim 1 , said imaging being such that an image of the line at said array is longer than the array.  
     
     
         3 . The method of  claim 1 , wherein said imaging images a center part of the line onto said array.  
     
     
         4 . The method of  claim 1 , wherein said focusing focuses the beam of radiation substantially only in a direction normal to the plane of incidence.  
     
     
         5 . The method of  claim 4 , said focusing including passing a beam of radiation through a cylindrical lens or to a cylindrical mirror.  
     
     
         6 . The method of  claim 1 , further comprising controlling a cross-sectional dimension of the beam of radiation and said oblique incidence angle in order to select length of the illuminated line.  
     
     
         7 . The method of  claim 6 , said controlling including expanding a beam of radiation so that the beam has a desired diameter after expansion.  
     
     
         8 . The method of  claim 1 , wherein said imaging focuses the line along an optical axis that is substantially normal to the line.  
     
     
         9 . The method of  claim 1 , said imaging employing a variable aperture, said method further comprising controlling the aperture of the variable aperture in response to roughness of the surface.  
     
     
         10 . The method of  claim 1 , further comprising causing relative motion between the surface and the beam so that the line scans the surface to detect anomalies and/or a surface feature.  
     
     
         11 . The method of  claim 10 , wherein said causing step moves the surface and leaves the beam and the array substantially stationary.  
     
     
         12 . The method of  claim 1 , said oblique angle being in a range of about 45 to 85 degrees from a normal direction to the surface.  
     
     
         13 . The method of  claim 1 , wherein said focusing employs an objective, and wherein the line is in a focus plane of the objective.  
     
     
         14 . The method of  claim 1 , further comprising performing time delayed integration at the array of detectors.  
     
     
         15 . A method for detecting anomalies of a surface and/or a surface feature, comprising: 
 focusing a beam of radiation at an oblique incidence angle to illuminate a line on the surface, said beam and a direction through the beam and normal to the surface defining an incidence plane of the beam; and    imaging said line onto an array of detectors outside of the plane of incidence, each detector in the array detecting light from a corresponding portion of the line.    
     
     
         16 . The method of  claim 15 , wherein said focusing is such that said line is substantially in the plane of incidence of the beam.  
     
     
         17 . The method of  claim 16 , said array being shorter than an image of the line at the array formed by said imaging, wherein said imaging images a center part of the line onto said array.  
     
     
         18 . The method of  claim 15 , said focusing including passing a beam of radiation through a cylindrical lens or to a cylindrical mirror.  
     
     
         19 . The method of  claim 15 , further comprising causing relative motion between the surface and the beam so that the line scans the surface to detect anomalies and/or a surface feature.  
     
     
         20 . An apparatus for detecting anomalies of a surface, comprising: 
 means for focusing a beam of radiation at an oblique incidence angle to illuminate a line on the surface, said beam and a direction through the beam and normal to the surface defining an incidence plane of the beam, said line being substantially in the plane of incidence of the beam;    at least one array of detectors; and    a system imaging said line onto the at least one array of detectors, each detector in the at least one array detecting light from a corresponding portion of the line.    
     
     
         21 . The apparatus of  claim 20 , wherein an image of the line formed by the system at the array is longer than the array.  
     
     
         22 . The apparatus of  claim 20 , wherein said system images a center part of the line onto said array.  
     
     
         23 . The apparatus of  claim 20 , said focusing means focusing the beam substantially only in a direction normal to the plane of incidence.  
     
     
         24 . The apparatus of  claim 23 , said focusing means including a cylindrical lens or a cylindrical mirror.  
     
     
         25 . The apparatus of  claim 24 , said focusing means including a cylindrical lens that has a principal plane substantially parallel to the surface.  
     
     
         26 . The apparatus of  claim 25 , wherein said focusing means focuses an input radiation beam directed at the focusing means, said input beam being substantially normal to the surface and to the principal plane of the lens.  
     
     
         27 . The apparatus of  claim 26 , said focusing means further comprising a diffraction grating for redirecting radiation from the lens towards the surface at an oblique angle to the surface.  
     
     
         28 . The apparatus of  claim 25 , wherein said focusing means focuses an input radiation beam directed at the focusing means, said input beam being in a direction oblique to the surface and to the principal plane of the lens.  
     
     
         29 . The apparatus of  claim 24 , said focusing means including a cylindrical mirror that has two substantially straight edges, wherein a plane defined by the two edges is substantially parallel to the surface.  
     
     
         30 . The apparatus of  claim 20 , further comprising an expander expanding the beam of radiation prior to focusing by the focusing means.  
     
     
         31 . The apparatus of  claim 20 , wherein said at least one array of detectors is outside of the plane of incidence.  
     
     
         32 . The apparatus of  claim 20 , wherein said system has an optical axis that is substantially normal to the line.  
     
     
         33 . The apparatus of  claim 20 , said system including a variable aperture for varying a collection angle of the system.  
     
     
         34 . The apparatus of  claim 20 , further comprising means for causing relative motion between the surface and the beam so that the line scans the surface to detect anomalies and/or a surface feature.  
     
     
         35 . The apparatus of  claim 34 , said at least one array of detectors being substantially stationary relative to the beam when relative motion is caused between the surface and the beam.  
     
     
         36 . The apparatus of  claim 20 , said oblique angle being in a range of about 45 to 85 degrees from a normal direction to the surface.  
     
     
         37 . The apparatus of  claim 20 , said at least one array of detectors being a linear array substantially parallel to the line.  
     
     
         38 . The apparatus of  claim 20 , said system comprising lens means having a Fourier plane, said apparatus further comprising a filter and polarizer substantially in the Fourier plane.  
     
     
         39 . An apparatus for detecting anomalies of a surface and/or a surface feature, comprising: 
 means for focusing a beam of radiation at an oblique angle to illuminate a line on the surface, said beam and a direction through the beam and normal to the surface defining an incidence plane of the beam;    an array of detectors outside of the plane of incidence; and    a system imaging said line onto the array of detectors, each detector in the array detecting light from a corresponding portion of the line.    
     
     
         40 . The apparatus of  claim 39 , wherein said focusing means is such that said line is substantially in the plane of incidence of the beam.  
     
     
         41 . The apparatus of  claim 40 , said array being shorter than an image of the line at the array formed by the system, wherein said imaging images a center part of the line onto said array.  
     
     
         42 . The apparatus of  claim 39 , said focusing means including a cylindrical lens or a cylindrical mirror.  
     
     
         43 . The apparatus of  claim 39 , further comprising means for causing relative motion between the surface and the beam so that the line scans the surface to detect anomalies and/or a surface feature.  
     
     
         44 . The apparatus of  claim 39 , wherein said system has an optical axis substantially normal to the line.  
     
     
         45 . The apparatus of  claim 39 , said system comprising lens means having a Fourier plane, said apparatus further comprising a filter and polarizer substantially in the Fourier plane.  
     
     
         46 . An apparatus for detecting anomalies and/or a surface feature on a first and a second surface of an object, comprising: 
 means for focusing a beam of radiation at an oblique incidence angle to illuminate a line on the first surface, said beam and a direction through the beam and normal to the first surface defining an incidence plane of the beam, said line being substantially in the plane of incidence of the beam;    at least one array of detectors;    a system imaging said line onto the at least one array of detectors, each detector in the at least one array detecting light from a corresponding portion of the line; and    means for detecting anomalies and/or a surface feature of the second surface.    
     
     
         47 . The apparatus of  claim 46 , said first and second surfaces being on opposite sides of the object.  
     
     
         48 . An apparatus for detecting anomalies and/or a surface feature on a first and a second surface of an object, comprising: 
 means for focusing a beam of radiation at an oblique angle to illuminate a line on the first surface, said beam and a direction through the beam and normal to the first surface defining an incidence plane of the beam;    an array of detectors outside of the plane of incidence;    a system imaging said line onto the array of detectors, each detector in the array detecting light from a corresponding portion of the line; and    means for detecting anomalies and/or a surface feature of the second surface.    
     
     
         49 . The apparatus of  claim 48 , said first and second surfaces being on opposite sides of the object.