Device and process for marking an ophthalmic lens with a pulsed laser of wavelength and energy selected per pulse

Abstract

A device for marking an ophthalmic lens (3), the lens (3) being made of at least one preset material, includes a laser (1) configured to produce permanent engravings on the lens (3) and configured to emit a focused beam of pulsed ultraviolet laser radiation that includes at least one radiation wavelength ranging between 200 nm and 300 nm, has a pulse length ranging between about 0.1 ns and about 5 ns, and has an energy per pulse ranging between about 5 μJ and about 100 μJ. A laser marking process configured to produce permanent engravings on an ophthalmic lens (3) via this device is also described.

Claims

1. A process for marking an ophthalmic lens produced from at least one predetermined material, the process being implemented by a device including a laser and an energy attenuator, the process comprising: laser marking permanent engravings on the lens using the laser, the marking including emitting, by the laser through the energy attenuator, a focused pulsed beam of ultraviolet laser radiation having at least the following parameters: a radiation wavelength comprised between 200 nm and 300 nm, a pulse duration comprised between about 0.1 ns and about 5 ns, an energy per pulse of the pulsed beam of laser radiation comprised between about 20 μJ and about 120 μJ, and an energy per pulse at the focal point comprised between about 10 μJ and about 80 μJ; and calibrating the energy attenuator by a probe placed between the energy attenuator and the ophthalmic lens.

2. The process as claimed in claim 1, wherein the energy per pulse at the focal point is comprised between about 10 μJ and about 65 μJ.

3. The process as claimed in claim 2, wherein the energy per pulse at the focal point is comprised between about 10 μJ and about 60 μJ.

4. The process as claimed in claim 1, wherein the focused beam of ultraviolet laser radiation has a peak power comprised between about 2.5 kW and about 1 MW.

5. The process as claimed in claim 4, wherein the peak power is comprised between about 10 kW and about 100 kW.

6. The process as claimed in claim 1, wherein the focused beam of ultraviolet laser radiation has a pulse frequency comprised between about 100 Hz and about 10 kHz.

7. The process as claimed in claim 6, wherein the pulse frequency is comprised between about 100 Hz and about 1 kHz.

8. The process as claimed in claim 1, wherein the pulse duration is comprised between about 0.1 ns and about 2 ns.

9. The process as claimed in claim 1, wherein the radiation wavelength of the focused ultraviolet laser beam is comprised between about 230 nm and about 290 nm.

10. The process as claimed in claim 1, wherein the energy per pulse emitted by the laser is comprised between about 30 μJ and about 80 μJ.

11. The process as claimed in claim 10, wherein the energy per pulse emitted by the laser is comprised between about 35 μJ and about 80 μJ.

12. The process as claimed in claim 11, wherein the energy per pulse emitted by the laser is comprised between about 40 μJ and about 60 μJ.

13. The process as claimed in claim 1, further comprising focusing a beam of ultraviolet laser radiation onto a focal plane of an F-theta lens with a focused beam diameter in the focal plane of the order of about 20 μm to about 50 μm.

14. The process as claimed in claim 13, further comprising regulating, by an energy attenuator, a fluence of the beam of ultraviolet radiation focused on a surface of the ophthalmic lens to be marked according to a plurality of operating modes of the attenuator, the plurality of modes each defining a determined fluence value.

15. A process for marking an ophthalmic lens produced from at least one predetermined material, the process being implemented by a device including a laser and an energy attenuator, the process comprising: laser marking permanent engravings on the lens using the laser, the marking including emitting, by the laser through the energy attenuator, a focused pulsed beam of ultraviolet laser radiation having at least the following parameters: a radiation wavelength comprised between 200 nm and 300 nm, a pulse duration comprised between about 0.1 ns and about 5 ns, an energy per pulse of the pulsed beam of laser radiation comprised between about 20 μJ and about 120 μJ, and an energy per pulse at the focal point comprised between about 10 μJ and about 80 μJ; and calibrating the energy attenuator by determining a curve representing the energy per pulse of the pulsed beam, as a function of an angle of orientation of a polarized filter relative to an axis of polarization of the pulsed beam to define the energy per pulse and regulating an operating mode of the energy attenuator based on the defined energy per pulse.

16. The process as claimed in claim 1, wherein the energy attenuator includes a polarized filter, the probe is placed between an F-theta lens and the ophthalmic lens, and the energy attenuator is calibrated by measuring the energy per pulse output from the F-theta lens, as a function of the energy per pulse issued from the laser and of an operating mode of the energy attenuator.

17. The process as claimed in claim 1, wherein the calibrating is carried out during one or more of (i) an initial regulation of one or more of the energy attenuator and the laser, and (ii) during a maintenance operation.

18. The process as claimed in claim 1, further comprising verifying the marking and correcting the marking depending on a result of the verifying.

19. The process as claimed in claim 18, wherein the verifying comprises evaluating a visibility of the marking.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention will become more clearly apparent on reading the description given with reference to the appended figures, which are given by way of nonlimiting indication, and in which:

(2) FIG. 1 illustrates the order of various steps of a process for manufacturing a lens;

(3) FIG. 2 schematically shows a marking device according to one exemplary embodiment of the invention;

(4) FIG. 3 shows a block diagram of a marking process according to one embodiment of the present invention; and

(5) FIG. 4 shows various operating steps of the marking process illustrated in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) FIG. 1 schematically shows the principle production steps of an ophthalmic lens.

(7) A substrate is first produced according to a preestablished prescription, for example being machined by turning in step 40.

(8) Here the term “substrate” refers to a body of the ophthalmic lens. A substrate conventionally has one edge and two surfaces that are separated from each other by the edge. Conventionally, one face, called the back face, is often concave, whereas the other face, called the front face, is often convex, but the inverse is possible.

(9) After machining, the faces of the lens are polished in step 50.

(10) Next, the lens optionally receives one or more what are called functional treatments on at least one of its faces, often on the back face, such as for example a coloring treatment in step 60, and/or one or more varnishing treatments in step 70, and/or possibly also an antireflection treatment in step 80.

(11) The treatments referred to as “varnishing” treatments are such as defined above.

(12) The treatments referred to as “antireflection” treatments are here such as defined above.

(13) After polishing, or even after the last of the aforementioned functional treatments if the lens receives one or more thereof, the lens is finished.

(14) The edge of the lens is given the shape of a frame for which it is intended either before polishing, or before functional treatment but after polishing, or generally after the functional treatments, when the lens is finished.

(15) By virtue of a device and process according to the invention, details of which will be given below, it is possible to produce, in step 90, permanent markings during the manufacturing process of the lens.

(16) It is for example not only possible to produce technical markings before or after the polishing in step 91, i.e. before the functional treatments, but also commercial markings in step 92 once the lens has been finished, i.e. either after polishing if the lens receives no functional treatments or after the last functional treatment step if the lens receives one or more functional treatments, such as on the varnish for example if the lens has undergone varnishing.

(17) The term “marking” is here understood to mean the result of engraving of an ophthalmic lens, referred to here as the ophthalmic lens to be marked, so as to form a marking. A marking step may allow a plurality of markings to be produced; for example, in the context of technical markings, there are at least two markings positioned at 34 mm from each other, equidistant relative to a fitting point of the lens, and forming a horizontal axis of the ophthalmic lens.

(18) Each marking is formed of at least one point or spot. If a marking comprises at least two spots, i.e. a plurality of spots, two consecutive spots are distanced from each other by a predetermined distance/separation.

(19) Each spot, for its part, is produced by at least one pulse of laser radiation at a precise location or by a plurality of pulses, i.e. at least two pulses.

(20) FIG. 2 schematically shows a device according to one embodiment of the present invention, especially allowing the marking step 90 of the process described above to be implemented.

(21) The device mainly includes a laser source 1 and an optical assembly 2.

(22) The laser source 1 emits a pulsed beam of infrared radiation.

(23) The optical assembly 2 allows for its part the beam of laser radiation to be focused so as to allow the desired engraving to be produced on a surface 31 of an ophthalmic lens 3, made of at least one predetermined material, which lens 3 is positioned on a holder 4.

(24) Conventionally, it is therefore the last layer that is engraved, for example especially the substrate or varnish depending on the circumstances.

(25) Dependent thereon, the lens is positioned in the frame of reference of the device differently.

(26) To produce a marking, the device is configured to emit a focused beam of ultraviolet radiation and advantageously with the following parameters: a radiation wavelength comprised between 200 nm and 300 nm, or even between about 230 nm and about 290 nm, preferably between about 208 nm and about 220 nm, for example about 209 nm or about 210 nm or about 213 nm, or alternatively more particularly between about 260 nm and about 270 nm, for example about 261.7 nm or about 263 nm or about 266 nm; a pulse duration comprised between about 0.1 ns and about 10 ns, or even preferably between about 0.1 and about 5 ns or even 2 ns; and an energy per pulse at the focal point comprised between about 5 μJ and about 100 μJ, or even between about 10 μJ and about 80 μJ, or even between about 10 μJ and about 65 μJ; and an energy per pulse emitted by the source is then comprised between about 20 μJ and about 120 μJ, preferably between about 30 μJ and about 80 μJ, and preferably higher than 35 μJ, or even higher than 40 μJ, or indeed even between about 40 μJ and about 60 μJ.

(27) Advantageously, the device is also configured to have a high peak power, i.e. between about 2.5 kW and about 1 MW, or even between about 20 kW and about 50 kW, and/or a pulse frequency comprised between about 100 Hz and about 10 kHz.

(28) The laser source 1 thus emits pulses with a determined energy per pulse, at a given pulse frequency, for a given wavelength. The pulse duration is generally fixed by the design of the laser source. Thus, the pulse frequency and the duration of each pulse induce a low average power, while having a high peak power.

(29) In one particular example, the device is configured to emit ultraviolet radiation and advantageously with the following parameters: a radiation wavelength of about 266 nm; a pulse frequency of about 1 kHz; a pulse duration of about 1 ns; and an energy per pulse at the focal point comprised between about 10 μJ and about 25 μJ depending on the material engraved.

(30) For example, the laser source is then configured to emit pulses having an energy per pulse, before an attenuator, comprised between 40 μJ and 60 μJ.

(31) For example: for an Orma® lens, which is mainly composed of a CR39 polymer, a spot is generally marked by eight pulses at an energy per pulse of about 25 μJ on the surface to be marked; for a polycarbonate, a spot is generally marked by one pulse at an energy per pulse of about 15 μJ on the surface to be marked; for a material of refractive index value of about 1.74, a spot is generally marked by three pulses at an energy per pulse of about 10 μJ on the surface to be marked; for the material called Stylis®, generally having a refractive index value of 1.67, a spot is generally marked by one pulse at an energy per pulse of about 25 μJ on the surface to be marked; for the material called Ormix®, of refractive index generally equal to about 1.6, a spot is generally marked by two pulses at an energy per pulse of about 15 μJ on the surface to be marked; and for a marking on an HMC varnish, with a view to creating a visible marking, a spot is generally marked by ten pulses at an energy per pulse of about 25 μJ, and for a faint marking, in order to mark an anti-smudge coating and/or antifog coating, by one pulse at an energy of about 10 μJ.

(32) Of course, with such a device the energy per pulse could be much higher.

(33) To this end, the laser source 1 of the device according to the invention includes a solid-state laser that emits a pulsed beam of infrared radiation. Such a laser especially has the advantage of being inexpensive for high peak powers, and induces very little or even no environmental constraints. Furthermore, its maintenance is simple.

(34) The expression “solid-state laser” is understood to mean a laser the excitation medium of which is defined in opposition to lasers having a gaseous or liquid excitation medium. What is meant is that the excitation medium is either a solid or ionic crystal or an optical fiber.

(35) One particularly advantageous such source is for example an Nd-YAG laser that emits principal radiation at a wavelength of about 1064 nm.

(36) To obtain ultraviolet radiation from a laser source emitting infrared radiation, the device here includes a multiplier 5 that is positioned at the output of the laser source 1. The multiplier 5 allows the radiation frequency of the laser radiation emitted by the laser source 1 to be multiplied, generally by a factor comprised between three and ten. The multiplier is chosen, depending on the wavelength emitted by the laser source, so as to obtain, as output from the multiplier, ultraviolet radiation that is able to be absorbed by the material and that is sufficiently energetic to destroy chemical bonds of the material of the lens, while using optical components that allow a suitable pulse frequency and duration to be achieved.

(37) In the case of an Nd-YAG laser emitting radiation the frequency of which corresponds to a wavelength of 1064 nm, it is for example then necessary to quadruple its radiation frequency. More precisely, at the output of a factor-four multiplier, the radiation will have a radiation frequency corresponding to a wavelength of about 266 nm.

(38) In the present exemplary embodiment, the multiplier 5 is positioned between the laser source 1 and the optical assembly 2.

(39) In practice, the laser source 1 and the multiplier 5 may for example be contained in the same housing, or be two separate elements to be juxtaposed on an optical line of the device. If needs be, the combination of the laser source and a multiplier in the same housing provides a system, referred to as a “laser system” for convenience, that is possibly very compact.

(40) In the present exemplary embodiment, the optical assembly 2 includes an afocal system 6, an attenuator 7, a scanner head 8 and an F-theta lens 9.

(41) The afocal system 6, the attenuator 7, the scanner head 8 and the F-theta lens 9 are here on the whole mounted in series.

(42) The afocal system 6 is an optical system allowing the radiation beam that is delivered thereto to be enlarged. In this case, it allows its cross section and its diameter to be tripled. For example, the beam of ultraviolet radiation output from the multiplier has a diameter “d”. It enters into the optical assembly 2 via the afocal system 6. At the output of the afocal system 6 it therefore has a diameter “3×d”, i.e. a tripled diameter. The afocal system could also have a different enlargement factor, for example comprised between two and ten.

(43) Here, the afocal system 6 is fixed, i.e. the same enlargement factor is always applied to a beam of given diameter. This is due to the composition of the afocal system 6. However afocal systems the enlargement factor of which is adjustable, i.e. variable, do exist. One of the advantages related to the use of a fixed afocal system is that a simpler and less costly structure is achieved.

(44) At the output of the afocal system 6, the ultraviolet irradiation enters into the attenuator 7.

(45) The attenuator 7 mainly allows a fluence to be regulated. The fluence is expressed in J/cm.sup.2 for example. It is the amount of energy (in J) per pulse incident on the surface of the ophthalmic lens to be marked per unit area (in cm.sup.2 for example).

(46) The attenuator 7 here has the particularity of being adaptable.

(47) In other words, the attenuator 7 here has a plurality of operating modes; it is configured to have a plurality of attenuation levels. The variation is for example either continuous or incremental. It is thus possible to adjust the energy of the beam depending on the material of the lens to be marked.

(48) The optical assembly 2 thus has an optical path (after the frequency multipliers 5), i.e. between the afocal system 6 and the F-theta lens 9, that has a degree of energy transmission of about 80% to 90%, and that may decrease as the optical assembly ages. However to engrave, by ablation, very different materials, and above all in order to allow the same fluence to be produced on the surface of the lens for a given focused beam diameter on the surface of the lens despite of aging of the source or of the optical path, it is necessary to be able to control the fluence over time. To do this, either the laser source is reconfigured to emit a radiation beam at another energy level, or it is then judicious to have an adaptable attenuator (adaptable in the sense adjustable) mounted in series at the output of the laser source so as to make it possible to adapt the energy of the radiation emitted by the laser source. Here, the laser source 1 is preferably a fixed-energy source, this making the device more economical. It is then preferable to provide an adaptable attenuator 7 in compensation.

(49) The fluence is determined so as to be high enough to achieve an ablation marking mechanism as a function of at least one predetermined parameter of the material of the ophthalmic lens. The parameter of the material on the basis of which the fluence is determined is for example chosen from a degradation parameter and an absorbance at the marking wavelength. To this end, for example, a performance table may be produced by calibrating the device for various commonly used materials, for example by producing a few engravings on test substrates and by measuring a fluence corresponding to a rendered visibility, both with the naked eye and by way of viewing systems such as a video camera, a microscope, or even alignment/control machines.

(50) The performance table for example allows an operating mode of the attenuator to be paired with a type of material to be engraved or an energy at the focal point to be paired with a material to be engraved.

(51) Pairing an energy at the focal point with a material to be engraved is a more advantageous option since it is not necessary to remake the performance table for each material as the system ages; it is enough to redo an attenuator energy/operating mode calibration, which is easier. However, this option requires that it be possible to measure the energy at the focal point per pulse.

(52) According to one advantageous alternative, the performance table may also be produced by measuring a visibility of a marking on said material for a pulse energy and/or a given operating mode of the attenuator and measuring a deformation induced by the marking.

(53) Thus, the determination of the value to be applied may be based on charts and/or tables of values indicating the fluence required for a given material and knowledge of the fluences allowed by the various operating modes. The operating mode of the attenuator 7 is chosen depending thereon.

(54) In the case of an adaptable attenuator 7, the device, and here the optical assembly 2 in particular, includes a probe 11.

(55) The probe 11 is placed between the attenuator 7 and the ophthalmic lens 3 to be marked, and here between the F-theta lens 9 and the lens 3 to be marked. The probe 11 is especially configured to calibrate the attenuator 7 and/or to calibrate a system comprising the laser source 1 and the attenuator 7, by measuring the energy per pulse output from the F-theta lens, which is substantially identical to the energy at the focal point, as a function of the energy per pulse issued from the laser source 1 and of an operating mode of the attenuator 7.

(56) After exiting the attenuator 7, the beam passes through the scanner head 8. The scanner head 8 makes it possible to pilot an orientation of the laser beam in the direction of the F-theta lens 9, and a position of the focused laser beam in a focal plane of the F-theta lens 9. The spots to be marked are defined and the scanner head is synchronized with the laser pulse frequency in order to illuminate/target in succession predetermined locational points corresponding to the spots to be marked.

(57) To do this, the scanner head 8 here comprises mirrors 10 to orient the beam, but the beam could be oriented by other means, such as for example a magnetic field.

(58) After exiting the scanner head 8, the beam here passes through the F-theta lens 9.

(59) An F-theta lens is a flat field lens forming a focal plane. If thus allows the beam to be focused in the focal plane with a determined beam diameter in the focal plane, thereby allowing the spots to be produced with a wanted diameter.

(60) The F-theta lens 9 is here located at the output of the optical assembly 2. Furthermore, in the present case, it is located just above the ophthalmic lens 3 to be marked.

(61) In the present exemplary embodiment, the F-theta lens 9 has a focal length of about 160 mm.

(62) The optical assembly 2 is thus configured to focus the beam of ultraviolet laser radiation onto the surface of the lens 3 for example with a focused beam diameter on the surface of the ophthalmic lens 3, when said surface is positioned in the focal plane of the F-theta lens, of the order of about 20 μm to about 50 μm. This for example makes it possible to obtain a marked spot of a diameter of about 15 to about 30 μm.

(63) Thus, to produce a marking, the various spots, if a plurality of spots are required, are produced by modifying the orientation of the beam by virtue of the scanner head 8.

(64) If various markings are to be produced, it is the position of the lens 3 to be marked that is then modified.

(65) To do this, the device furthermore for example includes a mechanism (not shown) for adapting the distance between the optical assembly 2 and the holder 4 of the ophthalmic lens 3 to be marked, in order to allow the altitude of the lens 3 to be modified during the marking process, if the latter includes the production of a plurality of markings.

(66) The device lastly preferably includes a computer and a controller, forming a command/control unit 12.

(67) The command/control unit 12 includes systematic elements configured to execute a computer program in order to implement each of the steps of a marking process, including predetermined operating parameters in order to emit the pulses of ultraviolet laser radiation with the aforementioned parameters, namely: a radiation wavelength comprised between 200 nm and 300 nm after multiplication forming a beam of ultraviolet radiation; a pulse frequency is comprised between about 100 Hz and about 10 kHz; a pulse duration comprised between about 0.1 ns and about 5 ns; an energy per pulse comprised between about 5 μJ and about 100 μJ; and a peak power comprised between about 2.5 kW and about 1 MW.

(68) Thus, the device presented above allows the various steps of the following process to be implemented.

(69) As illustrated in FIG. 3, the marking of an ophthalmic lens (steps 90 to 92), such as the ophthalmic lens 3, for example includes the following steps: a step 100 of positioning and blocking the lens; a step 200 of parameterizing and/or of performing calibrations; at least one step 300 of producing at least one engraving; and at least one step 400 of verifying the at least one engraving.

(70) If a plurality of engravings are required, the position of the lens is adjusted, and the following engraving is produced. The calibration and parameterizing steps then become optional.

(71) FIG. 4 shows operating steps of the process illustrated in FIG. 3.

(72) In this example, the device is configured: in step 201, to calibrate the attenuator 7 at least using the probe 11, in step 202, to receive predetermined operating parameters and/or parameters of the material of the ophthalmic lens 3 to be marked; in step 203, to receive at least one geometric characteristic of the ophthalmic lens 3 to be marked; in step 204, to determine a fluence; in step 205, to determine an altitude of the holder of the ophthalmic lens 3 to be marked; in step 206, to determine a ratio of a beam width output from the afocal system 6 to a focal length of the F-theta lens 9 in order to obtain a wanted spot diameter; in step 207, to determine a pulse frequency and a pulse repetition number per spot; in step 208, to determine a spacing between two consecutive spots; in step 301, to emit pulses using the laser source 1; and in step 302, to pilot the laser beam using the scanner head 8.