FR2674164A1 - DEVICE FOR THE ACCURATE POSITIONING OF AN OPTICAL GLASS DRAFT IN RELATION TO A REFERENCE PLANAR SURFACE. - Google Patents

Abstract

The invention relates to a device for the precise positioning of an optical glass blank (14) relative to the surface of a screen (16) on which the trace of a system of reference marks is displayed. In order to allow precise positioning without the use of an independent optical sighting device while avoiding the parallax phenomenon, the device according to the invention proposes to use an element with unidirectional optical transmission (26) interposed between the surface (17). ) of the screen (16) and the blank (14) so as to require the user to stand vertically with the image of the reference marks. The invention finds particular application in machines for centering optical glasses.

Description

The present invention relates to a device for positioning

  Precise optical glass blank with respect to a flat surface bearing the trace of a reference mark system and on which the blank rests.

  Such a device is used in installations

  for the cutting of optical glasses intended for

  equip corrective glasses of sight.

  The recent installations used by the opticians allow them to exploit computer files that preserve the coding of the shape of the different frames so as to display them on a flat screen In the use of such a device, the optician must place the blank optical glass to be cut in correspondence with the image then used

  from template to a numerically controlled grinding machine.

  The blank of the optical glass is marked with a special ink which enables the blank to be accurately positioned and oriented on the grinding machine so that the dimensions are

  grind on a control device of the rectifier-

  refer to a system of reference axes drawn on the blank in a first phase of work For this purpose, it is necessary to orient the blank on a system of axes and reference marks and mark this system of axes on the blank so as to fix the blank on the actual grinding machine which will machine the

  periphery of the glass according to the different parameters

  very. For this purpose, the grinding machine displays on a V-image display screen the desired shape of the corrective lens as well as the trace of a system of reference marks, including reference axes, with respect to which the optician positions and oriented

the draft.

  The optician places the optical glass blank on the flat face of the screen and orientates it so as to match the marks or marks on the ink deposited on the blank with the system of marks displayed on the screen. . The optician then places an adapter on the blank in a position that matches positioning marks deposited on the adapter with

  the desired orientation of the blank.

  The precise positioning of the blank with respect to the trace of the reference mark system, which must be performed with great precision, can for example be carried out using an optical viewfinder which extends over the machine. to center over the screen at

the vertical of the latter.

  In addition to the relatively high cost of such a

  tif optical sight, it has a large footprint and does not clear the upper face of the centering machine to facilitate others

  operations performed by the optician.

  The object of the invention is to remedy these drawbacks.

  and proposes for this purpose a device of the type mentioned above, characterized in that it comprises

  an element made of unidirectionally optical transmission material

  which is interposed between the trace of the reference mark system and the user's eye of the device so that its transmission axis

  optically perpendicular to the plane surface.

  Through the use of such a transmission element

  unidirectional optician, the optician can position the blank of the optical glass very accurately avoiding all the drawbacks associated with the phenomenon of parallax and perform sighting simply by placing itself above the flat surface, for example the screen, vertically to the reference mark system. According to other features and the invention, and in order to provide a device with a particularly small footprint, the unidirectional optical transmission element is interposed between the trace of the reference mark system and the blank of the optical glass. comprises a screen on which the image of the reference markers is formed, the unidirectional optical transmission element is integrated in a window arranged above the screen and

  on the free surface of which the draft of the glass rests.

  The unidirectional optical transmission element is, for example, an oriented natural quartz slice associated with two crossed polarization filters, or a

slice of spath.

  Other features and advantages of the invention

  will appear on reading the description

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are two diagrams making it possible to illustrate the principle of centering an optical glass blank; Figure 3 is a schematic partial sectional view of a device for positioning a blank made in accordance with the teachings of the invention. In Figure 1, there is shown schematically the elements for explaining the important parameters of the operation of laying an adapter on the blank of an optical glass at the end of the centering operation. The adapter can be a suction cup

  placed in an adapter holder 12.

  The axis ZZ of the adapter, when in the position of setting on a blank 14 of an optical glass, is perpendicular to the flat face of a screen 16 of a centering machine (not shown) on which is displayed the trace of a system of reference marks. In the diagram of Figure 2, we recognize the optical blank 14 which is superimposed with the image 18

  cutting glass that is displayed on the screen.

  The image 18 has a horizontal axis X-X and a vertical axis Y-Y whose point of competition O defines, with

  two other reference points A and B on the X-axis

  X, a system of reference marks for orientation

  and the precise positioning of the sketch 14 -

  The three points A, O and B are associated with three corresponding points A ', O O and B' plotted on the upper face 15 of the blank 14 and aligned on an axis of

reference X'-X '.

  The aiming and positioning operation to be performed by the optician is intended to bring into coincidence the marks drawn on the blank 14 with

those displayed on the screen 16.

  The accuracy of this centering operation is particularly important for the correct realization of a pair of glasses and therefore requires that the optician can overcome the classic phenomenon of parallax if he performs the positioning of the blank without

  using a bulky optical sighting device.

  For this purpose, the invention proposes to use the device of FIG. 3 on which is recognized the blank 14 and the display screen 16 which is here integrated in a centering machine 20 which has simply been illustrated schematic and so

partial silhouette of the building.

  A window or thick ice 22 is placed above

  of the upper face 17 of the display screen 16.

  The blank 14 rests on the free upper face 24 of the window 22 in the same way that it rests directly on the face of the display screen in the

  center known from the state of the art.

  According to the invention, the window 22 comprises in its central part situated opposite the vertical reference axis Z-Z of the device for placing an adapter, an optical transmission element.

unidirectional 26.

  In the embodiment illustrated in FIG. 3, the element 26 is in the form of a cylindrical slice whose thickness is equal to that of the pane 22 so that the upper free face 24

  the latter is continuous and flat.

  The element 26 is made of a unidirectional optical transmission material such as spath so that the light transmission can be effected through the element 26 only along the axis ZZ perpendicular to the upper face 24 of the glass 22 Using a material such as spath, the optical transmission angle around the axis

Z-Z is less than or equal to 2.

  It follows from this phenomenon that the optician is obliged to place himself exactly in the vertical of the trace of the reference marks displayed on the screen 16

  he perceives through 3 / draft 14 and item 26.

  The optician thus avoids any phenomenon of parallax because, if it comes to deviate slightly from the position to the vertical of the landmarks, he can not see these landmarks and is therefore unable to bring

  precisely the marks A ', O' and B 'in

  dence with the A, O and B marks displayed on the screen.

  It is therefore understood that the unidirectional optical transmission element 26 makes it possible to precisely position the blank 14 while completely clearing the upper face of the centering machine by virtue of the suppression of any optical sighting device. the element 26 can be made from a directed natural quartz slice with a particular optical directional axis associated with two crossed polarization filters arranged on either side of the

faces of the quartz slice.

  The dimensions of the slice or blade of material constituting the element 26 may be more or less important, the element 26 may constitute the entire window 22 However, given the cost of this type of material, it is sufficient to limit the presence to an area arranged above the image displayed on the screen vis-à-vis the trace reference marks.

Claims (3)

  Apparatus for precisely positioning a blank (14) of optical glass with respect to a flat surface bearing the trace of a system of reference marks (XX, YY, A, O, B) and on which the blank is based, characterized in that it comprises an element   (26) of unidirectionally optical transmission material   which is interposed between said trace of the reference marker system and the user's eye of the device so that its transmission axis   optical (X-X) is perpendicular to the plane surface.   2 Device according to claim 1, characterized in that the element (26) with unidirectional optical transmission is interposed between the trace of the system of reference marks and the optical glass blank (14) 3 3 Device according to claim 2, characterized in that it comprises a screen (16) on which is formed the image of the reference marks and a window (22) disposed above the screen and in which is   the unidirectional optical transmission element   (26), the blank (14) of the glass resting on the face free (24) of the window (22).   4 Device according to any one of the claims   characterized in that the unidirectional optical transmission element (26) is an oriented natural quartz wafer associated with two cross polarization filters.   Device according to any one of the claims   1 to 3, characterized in that the transmission element   Unidirectional optical projection (26) is a slice of spath.