Abstract:
The present disclosure relates to an apparatus for determining the orientation of ophthalmic lenses ( 20, 22 ). The apparatus includes a recording device and a reference-frame unit that can be fitted onto a frame ( 14 ) while a patient is wearing it. Said frame has two half parts ( 11, 13 ) and a central bridge ( 15 ). The reference-frame unit includes a first element forming an arch ( 24 ) that has a central portion ( 26 ) indicated by a first reference mark ( 54 ), and a second element ( 56 ) indicated by a second reference mark ( 58 ), mounted on said frame. According to the disclosure, the apparatus includes two cameras ( 60,62 ) separated vertically from each other and pointing at the eyes from two angles of view ( 64, 66 ); and the two cameras ( 60, 62 ) enable two images of said reference-frame unit ( 24, 56 ) to be recorded simultaneously in order to evaluate the relative positions of the two reference marks ( 54, 58 ) and provide a value that represents the slope of said half parts ( 11, 13 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §371 National Phase conversion of PCT/FR2009/000532, filed May 5, 2009, which claims benefit of French application Ser. No. 08/02624, filed May 15, 2008, the disclosure of which is incorporated herein by reference. The PCT International Application was published in the French language. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for determining the orientation of the ophthalmic lenses belonging to a frame and to a method for determining the orientation of the ophthalmic lenses belonging to a frame likely to be implemented by virtue of said apparatus. 
     There are already known installations for measuring this orientation and more specifically for measuring the curvature of the frame. 
     The frames, commonly called spectacle frames, comprise two receiving half-parts forming two receptacles and into which the ophthalmic lenses are respectively driven. The two half-parts are linked together by a central bridge and they are respectively equipped with two arms opposite the central bridge. In this way, said two receiving half-parts extend symmetrically to one another relative to a main plane of symmetry dissecting said central bridge. Thus, the frames are designed to be adjusted on the face of a patient, the central bridge resting on his nose, the two half-parts respectively in front of his eyes and the two arms respectively on his ears. The curvature then represents the inclination of the two receiving half-parts, and consequently of the ophthalmic lenses, relative to a plane perpendicular to the abovementioned main plane of symmetry, or quite simply to the inclination of the two receiving half-parts, one relative to the other; an inclination of 180° would then correspond to a zero curvature. 
     The known apparatuses comprise a recording device, which includes a digital camera and means for processing the image supplied by the camera. They also comprise a first positioner element provided with a first reference mark and a second positioner element provided with a second reference mark. The first positioner element can be adjusted on the spectacle frame by defining a median plane of the frame, whereas the second positioner element is adjusted on the frame so as to define an orientation of the receiving half-parts. 
     Reference should be made to the document FR 2 903 504, which describes such an apparatus. 
     Thus, by virtue of the camera used to record an image of the positioner elements resting on the frame which is in turn on the face of the patient, the position of the first reference mark with respect to the second reference mark is then determined in order to deduce therefrom the curvature of the frame. 
     Although this type of apparatus is efficient, and does already make it possible to provide a good assessment of the curvature, it is necessary to provide even more accurate values of the inclination of the receiving half-parts. Above all, it is now necessary to offer simple equipment that does not require the people intended to use them to have any particular skills. 
     Thus, a problem that then arises and that the present invention aims to resolve, is to provide an apparatus that makes it possible to accurately obtain more accurate values of the curvature and also that is simple to use. 
     In order to resolve this problem, the present invention proposes an apparatus for determining the orientation of ophthalmic lenses belonging to a frame. This apparatus comprises, on the one hand, a recording device and, on the other hand, a reference-frame unit that can be installed on a frame while a patient is wearing it. Said frame has two receiving half-parts able to receive ophthalmic lenses and a central bridge that links said two half-parts; said two half-parts extending symmetrically to one another relative to said central bridge. Said reference-frame unit comprises two independent elements, a first element forming an arch having a central portion marked with a first reference mark and two fixing ends designed to be fitted respectively into the lateral edges of said half-parts to keep said central portion away from said frame, and a second element marked with a second reference mark, fitted onto said frame between the two lateral edges, said recording device comprising a camera pointing at the eyes of said patient from a determined viewing angle in order to record an image of said reference-frame unit fitted onto said frame. Said apparatus comprises processing means for assessing, from said image, the relative position of the two reference marks and for providing a value representative of the inclination of said half-parts relative to one another. According to the invention, the apparatus also comprises another camera separated vertically from said one camera and pointing at the eyes of said patient from another viewing angle; and the two cameras can be used to simultaneously record two images of said reference-frame unit fitted onto said frame from the two viewing angles in order to accurately assess the relative position of the two reference marks and to provide a value representative of the inclination of said half-parts. 
     SUMMARY OF THE INVENTION 
     Thus, one characteristic of the invention lies in the use of a second camera in order to simultaneously record the two images of the reference-frame unit fitted onto said frame from the two distinct viewing angles. It is specified that the simultaneous recording of the two images means that the two recordings are taken at exactly the same instant or at instants that are very close together, provided that the patient remains immobile between these two instants. This way, knowing the position of said cameras, the viewing angles and the position of the patient relative to the cameras, the two apparent distances that separate the two reference marks are measured on the two recorded images and the real distance, and consequently the curvature, are deduced therefrom. How this value corresponding to the inclination of the receiving half parts relative to one another can be obtained will be explained in more detail hereinafter in the description. 
     According to a particularly advantageous embodiment, said second element of said reference-frame unit is fitted onto said central bridge. Thus, the curvature is measured with even greater accuracy. Specifically, since the element forming an arch is joined to the frame via its fixing ends fitted to the lateral edges of the half-parts, which makes it possible to keep said central portion substantially perpendicular to said main plane of symmetry, regardless of the curvature of the frame, the variations of the curvature of the frame induce large amplitude variations in the position of the central bridge. 
     Furthermore, said element forming an arch has calibration reference marks, that is to say, at least two calibration reference marks separated from one another by a known determined distance, for example 110 mm, so as to be able to deduce therefrom the apparent distance between the first and second reference marks that appear on the images by applying a simple rule of three. The expression “apparent distance” is used here because the first and second reference marks are not a priori located in the same plane. However, on the one hand, the two calibration reference marks spaced apart from one another will be adjusted to the greatest possible distance and on the central portion and, on the other hand, the position of the cameras and of the patient will be adjusted so that the calibration reference marks are located in one and the same plane on the images. Such a characteristic is obtained if the optical axis of the optical system of the cameras is perpendicular to the segment defined by the calibration reference marks. 
     Moreover, with said first element defining a median plane of the first element, said central portion advantageously comprises a projecting rod or barrel that extends substantially perpendicularly to said median plane of the first element, and said first reference mark is located on said free end of said rod. In this way, not only is the distance between the two reference marks increased further, because the apparent distances that separate the central bridge and the first reference mark on the images supplied by the two cameras are further increased, which makes it possible to increase the measurement accuracy, but also is the viewing angle of the cameras easily calculated relative to the rod. 
     To do this, said processing means include an angle calculation module, for determining the angle of said projecting rod relative to said viewing angles. This calculation is performed using calibration reference marks, by virtue of which a hypothetical line is produced on the images, from which line the distance that separates it from the first reference marks is measured. Furthermore, said angle measurement module is designed to also calculate the pantoscopic angle of said frame, that is to say the angle of the median plane of the frame relative to the vertical. 
     Furthermore, said processing means include a lens/eye distance calculation module for determining, from the value representative of the inclination of said half-parts, the distance that separates the eyes of the patient from the ophthalmic lenses. To do this, it is necessary to also know the distance that separates the eyes of the patient from the first reference mark. Therefore, said processing means can also be used to assess, from said images, the relative position of said first reference mark and of the reflection of the light on the apex of the corneas, the corneal reflections, so that the calculation module then determines the distance that separates the eyes of the patient from the ophthalmic lenses. As will be specified in the detailed description, the corneal reflections are manifested, on the images, by a small-diameter off-white spot on the cornea. In this way, all the parameters necessary for the adjustment of the ophthalmic lenses in a frame are likely to be determined by the apparatus according to the invention. 
     Advantageously, said cameras are fitted in a vertical plane so as to obtain two images on which the apparent distances that separate the first and second reference marks are as far apart as possible from one another. Specifically, the barrel-forming projecting rod bearing the first reference mark and the second element bearing the second reference mark and located on the central bridge are contained in a substantially vertical plane. In this way, the cameras give two images on which the distance variation amplitude between the two reference marks is maximum and consequently, a greater accuracy is obtained in the curvature calculation, as will be explained hereinbelow. 
     According to a second aspect, the present invention relates to a method for determining the orientation of the ophthalmic lenses belonging to a frame, said method being of the type whereby:
         a recording device and a reference-frame unit are provided, which unit can be fitted on a frame worn by a patient, said frame having two receiving half-parts able to receive ophthalmic lenses and a central bridge linking said two half-parts, said two half-parts extending symmetrically to one another relative to said central bridge, said reference-frame unit comprising two independent elements, a first element forming an arch having a central portion marked with a first reference mark and two fixing ends designed to be fitted respectively into the lateral edges of said half-parts in order to keep said central portion away from said frame, and a second element marked with a second reference mark, fitted onto said frame between the two lateral edges, said recording device comprising a camera pointing at the eyes of said patient from a determined viewing angle;   an image of said reference-frame unit fitted onto said frame is recorded;   from said image, the relative position of the two reference marks is assessed; and,   a value representative of the inclination of said half-parts relative to one another is provided.       

     According to the invention, said method also comprises the following steps:
         another camera is provided that is separated vertically from said one camera and pointing at the eyes of said patient from another viewing angle;   two images of said reference-frame unit fitted onto said frame are recorded simultaneously from the two viewing angles; and,   the relative position of the two reference marks is accurately assessed in order to provide a value representative of the inclination of said half-parts.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other particular features and advantages of the invention will become apparent from reading the following description of a particular embodiment of the invention, given as an indicative but nonlimiting example, with reference to the appended drawings in which: 
         FIG. 1  is a diagrammatic front view of the eyes of a patient provided with elements of the apparatus according to the invention; 
         FIG. 2  is a diagrammatic plan view according to the arrow II of the elements represented in figure  1 ; 
         FIG. 3  is a diagrammatic side view according to the arrow III of the elements represented in  FIG. 2 ; 
         FIG. 4  is a diagrammatic representation of the apparatus according to the invention; and, 
         FIG. 5  is a block diagram of an element of the apparatus according to the invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a pair of spectacles  10  fitted on the face  12  of a patient. This pair of spectacles  10  has a frame  14  equipped with two arms  16 , and two ophthalmic lenses  20 ,  22  which extend respectively in front of the eyes  19 ,  21  of the patient. The frame  14  has two receiving half-parts  11 ,  13  designed to receive the ophthalmic lenses  20 ,  22  and a central bridge  15  that links the two receiving half-parts  11 ,  13 . Furthermore, the frame  14  is equipped with a first arch-forming reference-frame element  24 . This first element  24  has a central portion  26  which extends longitudinally between two opposite ends  28 ,  30 , which respectively include a fixing end  32 . The fixing end  32  has a front arm  34  able to rest in front of the ophthalmic lenses  20 ,  22 , and opposite, a shorter, rear arm  36  resting behind the ophthalmic lenses  20 ,  22 . Thus, the fixing ends  32  overlap the ophthalmic lenses  20 ,  22  and respectively the lateral edges  35 ,  37  of the two receiving half-parts  11 ,  13 , in the vicinity of the two respective arms  16 ,  18  of the frame  14 , while leaving the visual space of the patient free. The first element  24  which is thus totally attached to the frame  14 , has two opposite calibration reference marks  38 ,  40  respectively fitted at the two opposite ends  28 ,  30 . These two calibration reference marks  38 ,  40  respectively present a white-colored mark in the form of a disk with a black dot  42 ,  44  at its center. Furthermore, the two black dots  42 ,  44  are spaced apart by a known distance, for example equal to exactly 110 mm. 
     Moreover, as will be seen in this  FIG. 1 , the representation of the pupils  46 ,  48  of the eyes  19 ,  21  of the patient, which pupils  46 ,  48  are able to present, in their center, an off-white mark corresponding to the reflection of the light, whether natural or artificial, at the apex of the cornea. When the space in which the apparatus is located is dark, an artificial light will advantageously be provided to emphasize the abovementioned off-white mark on the apex of the cornea. This off-white mark on a black background can easily be identified by automatic image processing means and corresponds substantially to a point on the straight line corresponding to the optical axis of the eye. 
     The first arch-forming reference-frame element  24  defines a median plane Pm substantially parallel to the plane of  FIG. 1 , and the central portion  26  includes a barrel-forming projecting rod  50  at the end  52  of which a first positioning reference mark  54  is marked. Just like the opposite calibration reference marks  38 ,  40 , this first positioning reference mark  54  has an off-white colored mark in the form of a disk and a black dot at its center. 
     Furthermore, the central bridge  15  of the frame  14  has a second reference-frame element  56  consisting of a pellet glued onto this central bridge  15 . This pellet has a second positioning reference mark  58  also consisting of a white-colored disk with a black dot at its center. 
     The first reference-frame element  24  and the second reference-frame element  56  constitute the two elements of a reference-frame unit for which the cooperation mode will be explained hereinbelow. 
     Reference should now be made to  FIG. 2 , showing, in a plan view, the elements represented in  FIG. 1 . This  FIG. 2  shows the two receiving half-parts  11 ,  13  symmetrical to one another relative to a vertical plane of symmetry P intersecting the central bridge  15 . These two receiving half-parts  11 ,  13  respectively define two half-planes P 1 , P 2 , intersecting the vertical plane of symmetry P at the level of the central bridge  15  by defining one and the same straight line Dt. A plane P 3  perpendicular to the vertical plane of symmetry P and containing the straight line Dt is parallel to the median plane Pm of the first reference-frame element  24  and it can be used to define the curvature of the frame  14 . Specifically, the curvature corresponds to the angle formed respectively by the two half-planes P 1 , P 2 , and the plane P 3  perpendicular to the main plane of symmetry P. It will be also be observed that this curvature can also be defined as being the inclination of the two half-planes P 1 , P 2  relative to one another, an inclination of 180° corresponding to a zero curvature. Furthermore, it will be noted that the first positioning reference mark  54  and the second positioning reference mark  58  are both intersected by the vertical plane of symmetry P and that, the greater the curvature of the frame  14 , the closer together these two positioning reference marks  54 ,  58  become, and, conversely, that the lesser the curvature, the more distanced from one another these two positioning reference marks  54 ,  58  become. Thus, the principle of the apparatus according to the invention lies notably in the measurement of this distance between the two positioning reference marks  54 ,  58 , in order to determine the curvature. 
       FIG. 3 , which illustrates a side view according to the arrow III, shows elements represented in  FIG. 2 , the barrel  50  and the pellet  56  glued onto the bridge  15 , and more specifically in the plane of  FIG. 3 , the distance d that separates the two positioning reference marks, one  54  at the end  52  of the barrel  50 , the other  58  on the pellet  56 . 
     The apparatus according to the invention also comprises a recording device represented in  FIG. 4  and comprising two CCD-type digital cameras, a top one  60  and a bottom one  62 , separated vertically from one another by a determined distance a and pointing at the face  12  of the patient at a distance D from the latter. The apparatus also includes processing means  63  represented in  FIG. 5 . These processing means  63  include an image processing module  65  that can be used to assess, from the images supplied and recorded by the cameras  60 ,  62 , notably the relative position of the two positioning reference marks  54  and  58 , as will be detailed hereinbelow. They also include a calculation module  67  that can be used to assess the inclination of the first reference-frame element  24  relative to the vertical by virtue of the calibration reference marks  38 ,  40  and the first positioning reference mark  54 . 
     The patient is then fitted with the frame  14  which is provided with its second reference-frame element  56  consisting of a pellet glued onto the central bridge  15  and including the second positioning reference mark  58 ; the frame  14  being equipped with its first reference-frame element  24  including the first positioning reference mark  54 . 
     Thus, two images of the face  12  of the patient are recorded respectively and simultaneously via the two cameras  60 ,  62  and from two different viewing angles, one  64  substantially horizontal, the other  66  close to 20° relative to the horizontal. 
       FIG. 1  then illustrates the image viewed by the top camera  60  from the substantially horizontal viewing angle  64 . Firstly, the processing means  63 , via the image processing module  65  and the calculation module  67 , determine the angle formed by the axis A of the barrel  50  relative to the viewing angle  64  of the top camera  60 . To do this, the image processing module  65  hypothetically defines a line intersecting the two calibration reference marks  38 ,  45  and then measures, in the plane of the image, for example by counting pixels, the distance d 0  that separates the first positioning reference mark  54  from the barrel and this hypothetical line in a perpendicular direction. The length l of the barrel  50  being known, the central portion  26  extending in one and the same plane Pm, and the two calibration reference marks  38 ,  45  being spaced apart by a known distance, in this case by 110 mm, the calculation module  67  naturally deduces, from the distance that separates the first positioning reference mark  54  from the hypothetical line, the angle of inclination of the axis A of the barrel  50  relative to the viewing angle  64 . 
     Obviously, this angle is also measured in the same way on the image recorded via the bottom camera  62 , relative to the other viewing angle  66 . 
     Furthermore, the processing means make it possible to measure, on each of the images, the apparent distances d 1 , d 2  between the positioning reference marks  54 ,  58 , and that appear represented in  FIG. 3 . 
     In this way, knowing the viewing angles  64 ,  66  and the orientation of the axis A of the barrel  50  relative to these viewing angles, and also by determining the apparent distances d 1 , d 2 , the calculation module  67  deduces therefrom the real distance d that separates the two positioning reference marks  54 ,  58 . 
     Reference should be made once again to  FIG. 2  to show how it is possible, from this real distance d that separates the two positioning reference marks  54 ,  58 , to calculate the angle α, or curvature of the frame. 
     The dimensions of the fixing ends  32  are also determined, and they make it possible to ascertain the exact distance d 4  that separates the central portion  26  from the lateral edges  35 ,  37  of the two receiving half-parts  11 ,  13 . The distance that separates, along the central portion  26 , the two fixing ends  32  is also known. Furthermore, by virtue of the real distance d, the position of the abovementioned plane P 3 , which is tangential to the central bridge  15  at the level of the second positioning reference mark  58 , is determined. The inclination of the two half-planes P 1  and P 2  relative to the plane P 3  perpendicular to the plane of symmetry P, and consequently the curvature value, are then deduced therefrom, via the calculation module  67 . The processing means  63  have a display terminal  69  for displaying the results of the abovementioned calculations. 
     Moreover, to obtain full knowledge of the ophthalmic parameters, the apparatus also makes it possible to determine the distancer d vo  that separates the ophthalmic lens from the eye. Thus, according to the same calculation principle, the calculation module  67  firstly determines, by virtue of the two images from the abovementioned two cameras  60 ,  62 , and via the image processing module  65 , the distance that separates the two reflections of the cornea that appear white in the images, from the first positioning reference mark  54  situated at the end  52  of the barrel  50 . 
     The three-dimensional coordinates of each of the apexes of the corneas are then obtained. Since the curvature of the frame has already been calculated, the calculation module  67  can calculate the coordinates of each of the points of the frame and, more specifically, the coordinates of the intersection of the points of the frame and of the axis of the cornea and, consequently, of the eye. It then deduces therefrom the distance that separates the ophthalmic lens from the eye.