Method for making an object made of translucent synthetic...

Electric heating – Metal heating – By arc

Reexamination Certificate

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C219S121650, C219S121670

Reexamination Certificate

active

06188040

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention concerns marking any translucent synthetic material object, i.e. applying a symbol to that object for identifying and/or tracing it.
The symbol can include, for example, a serial number, a reference number or any other inscription relating to the characteristics of the object concerned, the treatment it has undergone or that it is to undergo.
The present invention is more particularly, although not necessary exclusively, directed to the situation in which the object is an ophthalmic lens.
To assure the identification and/or the tracing, i.e. the “traceability”, of an ophthalmic lens, whether it is a mineral glass ophthalmic lens or an organic material (synthetic material) ophthalmic lens, and thereby to enable its characteristics to be determined at any time by a simple reading process, it is necessary to apply to it a symbol including all the required information, in encoded form or otherwise.
In the case of a mineral glass ophthalmic lens, or more generally any object made from such glass, for example the molding shells used to mold synthetic material ophthalmic lenses, it has been proposed to use an etching process, in particular a laser etching process.
This is the case, for example, in published French patent application N°2 732 917 (application N°95 04314 filed Apr. 11, 1995).
In the above French patent application, it is proposed to cause the beam from a YAG laser to interfere with a layer of a particular material, in this instance a cement capable of reacting with the glass, applied to the surface of the object to be treated beforehand for this purpose.
This has the advantage of combining the resulting etching with a coloration which, by increasing the contrast of the etching, facilitates and renders more accurate subsequent reading of the symbol obtained in this way.
In the case of marking mineral glass objects, it is therefore satisfactory.
However, although they may be acceptable for mineral glass objects to be used many times, for example molding shells for molding synthetic material ophthalmic lenses, the costs inherent in the use of a cement of this kind are less acceptable for synthetic material objects which are not re-used, for example the ophthalmic lenses themselves, because they represent an unnecessary increase in the overall cost of such items.
Moreover, no such cement is necessary in this case, an appropriate choice of its wavelength enabling the laser beam to react directly with the synthetic material.
BRIEF SUMMARY OF THE INVENTION
A general object of the present invention is an arrangement which advantageously achieves sufficient contrast of the symbol obtained for subsequent reading of the symbol to be reliable, despite the absence of cement.
To be more precise, the present invention consists firstly in a method of marking a translucent synthetic material object, for example a synthetic material ophthalmic lens, it being understood that this material is then not only translucent but also transparent, and that the object concerned can be bare, varnished or coated with any material, for example an anti-reflection material.
The method in accordance with the invention is generally characterized in that said object is etched in the form of cells and each etched cell is in the form of a well and has at least one projection upstanding on the bottom of said well.
Trials have confirmed that, with a projection of this kind, each etched cell appears on reading as an area sufficiently dark to be identified as actually being an etched cell.
The reason for this is probably that the projection leads to local diffusion and/or refraction of light enabling the required identification of an etched cell as such by contrast with a non-etched cell.
When, in a preferred embodiment, the etching is assured in a manner known in itself using a laser, each etched cell is made, for example, by using the laser to execute at least two shots offset relative to each other.
As also confirmed by trials, the offset between the shots provides a very simple way to obtain the required projection.
Because of this offset, the shots resemble scanning with a small amplitude which conditions the width finally obtained for the etched cell formed in this way.
In practise three laser shots forming two projections for each etched cell constitute, in accordance with the invention, a good compromise between fast execution of the symbol required and sufficient definition of the latter for subsequent reading.
The present invention further consists in any translucent synthetic material object, and in particular any ophthalmic lens, provided with a symbol of the above kind.
Trials show that subsequent reading of this symbol can advantageously be reliable, even after the application to any such object of a layer of any thin and transparent material, such as a varnish or an anti-reflection material.
The present invention further consists in a symbol reader enabling such reading to be effected in a simple manner.
The symbol reader is generally characterized in that it includes a CCD camera and an illuminating device adapted to generate a beam the transverse dimension of which is between one and three times that of the symbol to be read.
For example, this illuminating device is an illuminating strip disposed transversely to the optical axis of the system.
To read the symbol on a translucent synthetic material object it is sufficient to dispose the symbol on the object between the CCD camera and the illuminating strip.
No calibration or supplementary adjustment is necessary.


REFERENCES:
patent: 4194814 (1980-03-01), Fischer et al.
patent: 37 28 622 (1988-05-01), None
patent: 196 08 937 (1996-09-01), None
patent: 2 621 529 (1989-04-01), None

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