Abstract:
Described herein is an apparatus and method for characterizing the precise dimensions of a pair of eyeglass frames, including that of the internal setting groove, through a non-mechanical measurement mechanism. The intended spatial resolution in all three orthogonal axes (x, y, &amp; z) is better than 50 microns (millionths of a meter).

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates to a machine which determines ophthalmic frame groove dimensions in up to three axes of a metal or plastic optical frame so that a ophthalmic lens can be cut with a precise bevel allowing the lenses to individually fit inside the eye wire with their optical centers aligned to a user&#39;s pupil positions with minimal frame distortion. 
       BACKGROUND OF THE INVENTION 
       [0002]    Existing techniques to measure eyeglass frame dimensions employ a mechanical stylus. See, for example, US20140020254, US20130067754, and U.S. Pat. No. 8,578,617, which all describe mechanical contact methods to measure the shape and dimensions of the frame needed to fit the glass. These patents describe measuring the groove of the frame to get information about the shape and dimensions of the frame which assists an eyeglass maker to decide on the dimensions to cut a lens and its bevel to fit a frame. 
         [0003]    The problems with these methods include:
   a. Measurements with a stylus in the tracer machine at a optician&#39;s office location result in errors in the lens cut at a lab which has the cut/edger machine due to calibration errors between the different instruments. The mechanical instrument needs to be calibrated often in the optician&#39;s office to ensure accurate measurements.   b. The tracer stylus often falls out of the groove and fails to accurately measure the depth due to groove width or sharp curving turns around the frame corner. The resulting lens may end up with gaps between the frame and the lens in those corners.   c. Frame shapes can be easily distorted, especially thin plastic frames, because the lenses (dummy or actually used) are removed for enabling stylus-based measurement.   d. Frame bending can occur as a result of bevel incorrectly positioned on the lens edge. This results in the frame user feeling that the frame does not look like what he expected while trying on the frame with dummy lenses.   e. Additional time and shipping charges result from the need to ship frames to the remote lab for tracing, cutting, edging and fitting of the lens to the selected frame. Any delay can impact frame scheduling, sometimes for multiple opticians, piling up in the labs for measurement and processing.   
 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention eliminates a physical stylus tracing the lens shape by using an imaging system to create a computer model, and then using that model to determine how a lens should be best cut to fit the frame. 
         [0010]    A computer model of an eyeglass frame lens groove is created in a two-stage process, which is then used to manufacture the lenses. A microscopic camera is used to track a frame&#39;s lens groove and provide data for the computer frame model. A lighting system is designed specifically to assist the camera to create images which the programmed computer can use to find frame and groove contour lines. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a better understanding of the disclosure, and to show by way of example how the same may be carried into effect, reference is now made to the detailed description along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts. 
           [0012]      FIG. 1A  shows the front view of a typical pair of eyeglass frames. 
           [0013]      FIG. 1B  shows an orthogonal side view of a typical pair of eyeglass frames shown in  FIG. 1A . 
           [0014]      FIG. 1C  shows the top view of a typical pair of eyeglass frames shown in  FIG. 1A , showing the significant degree of curvature (wrap) associated with the frames. It also shows the curve of the front face of the lens, also known as the “Base Curve”. The base curves are typically standard values. 
           [0015]      FIG. 1D-1F  show an example of a frame-groove imaging and curve-fitting process.  FIG. 1D  shows the captured imaging data of the frame&#39;s upper and lower surface, and contour lines of the lens grove.  FIG. 1E  shows the imaging data after a curve-fitting adds missing information.  FIG. 1F  shows the Groove Width  37  and Location  39  of the Groove  27  with respect to the frame edges. Tracking this distance allows a more precise determination of the bevel of the lens so it matches the Frame  11  better than in the prior art. 
           [0016]      FIG. 2A  is a block diagram of a first embodiment of the invention, referred to as the Imaging Method, consisting of a first Frame Measurement stage, and a second Grove Measurement stage. 
           [0017]      FIG. 2B  is a block diagram of a second embodiment of the invention referred to as the Mechanical Touch Probe Method. 
           [0018]      FIG. 3A  shows an orthogonal view of the Frames  11  and Camera  13  used in the Imaging Method acquiring a full field-of-view front Macro-Image  15 . 
           [0019]      FIG. 3B  shows the Imaging System  17  positioned to begin capturing Micro-Images  19  of the Frame  11  using a Camera Mirror  55 . 
           [0020]      FIG. 3C  shows the groove imaging system in relation to a Frame  11  (used to acquire z-axis or depth information for all methods described herein), including the Touch Probe  31 , Z-Axis Stage  35  and Touch Probe Retraction Spring  57 . 
           [0021]      FIG. 4A  shows the Imaging method, specifically using the Z-Axis Laser  25  and Laser Camera  26 , which determine height of Frame  11  at a number of points on the Frame  11 .  FIG. 4B  shows the Mechanical Touch Probe method, specifically using the Touch Probe  31 , Z-Axis Stage  35  and Touch Probe Retraction Spring  57 . 
           [0022]      FIG. 5  shows the multi-color LED Frame Lighting  41  sheet used for background and foreground zone based illumination, and the Frame Mount  51  apparatus. 
           [0023]      FIG. 6  is an orthogonal view of an optional advanced base using a six-axis Hexapod for the Frame Holder Assembly shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    While the making and using of various embodiments of the present disclosure are discussed in detail below, it should be appreciated that the present disclosure provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The disclosure is primarily described and illustrated hereinafter in conjunction with various embodiments of the presently—described systems and methods. The specific embodiments discussed herein are, however, merely illustrative of specific ways to make and use the disclosure and do not limit the scope of the disclosure. 
         [0025]    Two measurement methods are disclosed in the present invention: (1) an Imaging Method; (2) a Mechanical Touch Probe Method. In both of these methods, a computer model of an eyeglass frame lens groove is created in a two-stage process, which is then used to manufacture the lenses. The two methods differ only in their first stage, in which the initial data to drive a microscopic camera is collected. 
         [0026]    These methods capture multiple images from the interior of an eyeglass lens grove; the computer processes the images to identify, measure and store the features of the frame&#39;s lens groove. In the current embodiment, a user removes a lens from the left side of the frames to allow for the frame groove can be measured and modeled. This method can be used to generate a standalone three-dimensional model generation of the lens that is cut and beveled. 
         [0027]    The Imaging Method uses a Z-Axis Laser  25  to determine the vertical dimension (z-axis) of the top of a Frame  11  as it is mounted in the invention, as it creates a computer model of the Frame  11  and designs the lens to properly fit the Frame  11 . 
         [0028]    The Mechanical Touch Probe method uses a Touch Probe to find the vertical dimension, rather than a camera and laser, to correct the computer model for the frame&#39;s curvature, 
         [0029]    The objective of the invention is to characterize the precise shape of a pair of eyeglass frames, including that of the internal groove (see  FIG. 1A-1D ), to a spatial resolution of better than 50 microns in all three physical directions, referred to as “x”, “y”, and “z”. 
         [0030]    The imaging system based method is performed in two stages. The first stage measures the dimensions of a pair of glasses. The second stage focuses on the frame&#39;s inside grooves in which a lens fits and is held in place. Together, these processes produce a data set sufficient to cut the real lens and form the proper bevel on its edge. 
         [0031]    One embodiment of the first stage is the Imaging System, shown on  FIG. 2A , in which a two-step imaging system is used to capture images of the frames and dummy lenses. The first step is to create an image of the entire Frame  11 , referenced as the Macro-Image  15 . Then the camera approaches the Frame  11  and creates images taken very close, known as Micro-Images  19 , generating highly detailed images from with a microscopic field of view. From these detailed Micro-Images  19 , the profiles of the Frame  11  and Dummy Lenses  21  are constructed in detail. 
         [0032]    In the Frame Measurement stage of the Imaging Method, the eyeglass Frame  11  is positioned by small steps in the x-y plane with a computer-controlled linear X-Y Stage  33 , as shown in  FIG. 3B . Commercially available stages may be positioned within 2 microns (millionths of a meter). A Camera  13  creates a full front Macro-Image  15 , as shown in  FIG. 3A . This image is processed to determine Frame Points  23 , coordinates of locations around the Frame  11  and Lenses  21  where the Camera  13  should create microscopic images to add detail in the Frame Model  49 . 
         [0033]    In the current embodiment, the algorithm overlays places two lines horizontally across the lens locations on the Macro-Image  19 , and two vertically over both lens areas. The algorithm determines the x- and y-coordinates of points close to the boundary of the Frame lens. In this embodiment, this process creates eight sets of coordinates, called Frame Points  23 . 
         [0034]    The Camera  13  is then placed in a position close to the frame to capture Micro-Images  19  in front of each Frame Point, as shown in  FIG. 3B . In this stage, the invention lowers a Camera  13  and Mirror  55 . The Camera  13  captures images of the reflection on the Mirror  55 , which is positioned toward the Frame Groove  27 . During this process, the Frame Lighting  41  is automatically adjusted to generate the most visible contour lines in the in the image. 
         [0035]    These Micro-Images  19  are recorded, and any mismatch between expected coordinates is used to correct initially collected coordinate data. The Frame Groove  27  is thereby tracked in real time as the Camera sweeps in a full circle, tracking the Groove  27  during the sweep, and collecting its modeling data. 
         [0036]    The Micro-Images  19  are taken at a constant distance from the Frame  12  and lens. This is necessary to keep the pixel scale the same in each Micro-Image  19 . The constant distance is maintained by Z-Axis Stage  35 . Its data may be supplied either by the Mechanical Touch Probe Method, shown in  FIG. 4 , or the Groove Measurement (Image Method), shown in  FIG. 3C . 
         [0037]    By applying established and proprietary image processing algorithms, the exact coordinates of points on the boundary of the Frame  11  and Lens  21  may be determined to better than one-micron accuracy in any dimension. 
         [0038]    For the Groove Measurement (stage  2 ), the Camera  13  must have miniature imaging capability system. 
         [0039]    This imaging system is rotated with the frame in series of steps. A series of Micro-Images, close-up photos, is taken over a full 360 degrees. The steps can be as little as two microns, depending on the precision of the encoders used on each positioning stage 
         [0040]    The Micro-Images are processed to determine the thickness of the groove and its path in the x-y plane. This process also gives the z-axis data with respect to the frame scan in stage one. 
         [0041]    As shown in  FIG. 4B , the Mechanical Touch-Probe Method is used to collect z-axis depth data over the Frames  11 . It uses a commercially-available linear positioning Z-Axis Stage  35  that can measure changes in height with micron accuracy. 
         [0042]    To initiate the Mechanical Touch-Probe Method, the eyeglass frames are mounted on a high-accuracy X-Y Stage  33 . The probe is mounted on a Z-Axis Stage  35 . 
         [0043]    The Frame Point  23  position data from the Imaging Method (described above) is used to position the probe. The probe samples the depth of the frame at each of the strategic Frame Points  23 . These measurements characterize the profile of the Frame  11 . 
         [0044]    The method disclosed assumes that the invention&#39;s user has no access to factory construction data of the eyeglass Frames  11 . However, if this data is available, then it provides significant data to begin a successful model, including the ‘A’ and ‘B’ industry dimensions of lens height and depth. 
         [0045]    The current embodiment of the method described is typically performed on the left lens, and a dummy lens is kept in the right lens Frame Groove  27 . This allows the user to detect if a dummy lens  27  is missized or misshapen by comparing the examination results of the method on the left side of the frame with the expected shape found on the right, during the first stage of the process, using the Macro-Image. 
         [0046]    The current invention also uses a color and intensity controllable light array with multiple independent zones to improve contrast, front and back lighting in the area of interest, when different types of frame materials, like metal, plastic, transparent plastic, translucent plastic or rimless frames are measured in the same apparatus. This allows easy detection of edges and groves under a variety of material conditions. 
       LEGEND 
       [0047]      
         [0000]    
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Frame 11 
               
               
                   
                 Camera 13 
               
               
                   
                 Macro-Image 15 
               
               
                   
                 Imaging System 17 
               
               
                   
                 Micro-Image 19 
               
               
                   
                 Lens 21 
               
               
                   
                 Frame Point 23 
               
               
                   
                 Z-Axis Laser 25 
               
               
                   
                 Laser Camera 26 
               
               
                   
                 Frame Groove 27 
               
               
                   
                 Touch Probe 31 
               
               
                   
                 X-Y Stage 33 
               
               
                   
                 X-Stage 33X 
               
               
                   
                 Y-Stage 33Y 
               
               
                   
                 Z-Axis Stage 35 
               
               
                   
                 Groove Width 37 
               
               
                   
                 Groove Position 39 
               
               
                   
                 Frame Model 49 
               
               
                   
                 Frame Lighting 41 
               
               
                   
                 Frame Mount 51 
               
               
                   
                 Z-Stage Encoder 53 
               
               
                   
                 Mirror 55 
               
               
                   
                 Touch Probe Retraction Spring 57 
               
               
                   
                 Hexapod 59