PROCESS AND SYSTEM FOR MATERIAL REMOVAL

Abstract

An arrangement including an air conveying device and a suction device guiding an air flow across a site for a duration of a process. The direction of air flowing towards the surface and a tangent to the surface at the ablation site intersect at an angle. A flow velocity of the air flow is controlled. A direction of air flowing away from the surface and the tangent at the site intersect. The flow velocity is selectable, within a specified range. A flow velocity is variable.

Claims

1. (canceled)

2. An arrangement for ablation of material from a surface of an object by application of laser radiation, in a process of photorefractive keratectomy, comprising: an air conveying device and a suction device guiding an air flow across an ablation site for a duration of an ablation process; wherein a direction of air flowing towards the surface and a tangent to a surface at the ablation site intersect at an angle of 0 to 70; wherein a flow velocity of air flow is controlled to be in a range from 1 meter/second to 10 meter/second; wherein a direction of the air flowing away from the surface and the tangent at the ablation site intersect at an angle of 0 to 70; wherein the flow velocity of the air flowing over the ablation site before a start of the ablation process is preselectable within a specified range, and wherein the flow velocity is variable during the ablation process.

3. The arrangement as claimed in claim 2, the air conveying device comprising outlet openings and a suction device comprising entrance openings, and wherein air conveyance and definition of a flowing direction of the air is effected by two flow channels arranged consecutively in the direction of the laser beam and wherein the two flow channels are shaped as two rings centered around the laser beam, one of the two rings presenting the outlet openings and the other of the two rings presenting the entrance openings for the air flow.

4. The arrangement as claimed in claim 2, further comprising controls for preselecting a temperature, a relative air humidity or both the temperature and the relative air humidity within specified ranges before the start of the ablation process.

5. The arrangement as claimed in claim 2, further wherein the air conveying device keeps the air flowing across the ablation site during the ablation process with at least one quality selected from a group consisting of a temperature of minus 8 C.,-a relative air humidity of 80%, and a flow velocity of 3 meters/second.

6. The arrangement as claimed in any of claim 2, further comprising controls that vary the temperature and/or the relative air humidity within specified ranges during the ablation process.

7. The arrangement as claimed in claim 6, further comprising controls that vary the flow velocity within a range of 1 meter/second to 10 meters/second, an air heating device, controls for varying the temperature within a range of minus 20 C. to plus 30 C., an air humidifying device, controls that vary the relative humidity within a range of 0 to 100% or a combination of the foregoing.

8. The arrangement as claimed in claim 7, wherein the air humidifying device comprises a nebuliser that nebulises 0.5 ml to 2 ml of water per minute with a droplet size of <4 mm.

9. The arrangement as claimed in claim 6, further comprising control circuits that, during the ablation process, effect changes of temperature, relative humidity, flow velocity or a combination of the foregoing according to specified time schedule functions.

10. The arrangement as claimed in claim 7, further comprising control circuits that, during the ablation process, effect changes of temperature, relative humidity, flow velocity or a combination of the foregoing according to specified time schedule functions.

11. The arrangement as claimed in claim 8, further comprising control circuits that, during the ablation process, effect changes of temperature, relative humidity, flow velocity or a combination of the foregoing according to specified time schedule functions.

12. The arrangement as claimed in claim 6, further comprising sensors that measure temperature, humidity values or a combination of temperature and humidity values from the direct environment of the ablation site and, that via evaluation devices, are coupled with control circuits by which changes of temperature, relative humidity, flow velocity or a combination of the foregoing are effected as functions of the measured temperature, the humidity values or a combination of the temperature and the humidity values.

13. The arrangement as claimed in claim 7, further comprising sensors that measure temperature, humidity values or a combination of temperature and humidity values from the direct environment of the ablation site and, that via evaluation devices, are coupled with control circuits by which changes of temperature, relative humidity, flow velocity or a combination of the foregoing are effected as functions of the measured temperature, the humidity values or a combination of the temperature and the humidity values.

14. The arrangement as claimed in claim 8, further comprising sensors that measure temperature, humidity values or a combination of temperature and humidity values from the direct environment of the ablation site and, that via evaluation devices, are coupled with control circuits by which changes of temperature, relative humidity, flow velocity or a combination of the foregoing are effected as functions of the measured temperature, the humidity values or a combination of the temperature and the humidity values.

15. The arrangement as claimed in claim 9, further comprising sensors that measure temperature, humidity values or a combination of temperature and humidity values from the direct environment of the ablation site and, that via evaluation devices, are coupled with control circuits by which changes of temperature, relative humidity, flow velocity or a combination of the foregoing are effected as functions of the measured temperature, the humidity values or a combination of the temperature and the humidity values.

16. The arrangement as claimed in claim 10, further comprising, to measure humidity values, a straylight measuring device wherein an intensity of a reflection of a laser beam from the material surface is used as a measure of humidity, the laser beam emitting wavelengths in the visible or infrared spectral range.

17. The arrangement as claimed in claim 12, further comprising a thermal camera for the contactless measurement of current temperatures on the material surface.

18. The arrangement as claimed in claim 2, further comprising an excimer laser emitting laser emitting radiation at a wavelength of 193 nm as a source of ablation energy.

19. The arrangement as claimed in claim 3, wherein the two flow channels are separated from the surface of the object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which:

[0036] FIG. 1 is a system to remove material with the help of laser radiation, in which a laser beam is directed at the material surface and a device to climatize the environment at the surface is provided to feed a climatized air stream.

[0037] FIG. 2 is an example of the embodiment of a feed and discharge device for a climatized air stream directed at the material surface and its arrangement in the vicinity of the point of removal.

[0038] FIG. 3 is one way to position measuring devices to determine the temperature and humidity values in the vicinity of the point of removal.

[0039] FIG. 4 is another possible embodiment of the device to feed and discharge a climatized air stream.

[0040] While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.

DETAILED DESCRIPTION

[0041] In FIG. 1, a tubular channel 1 is shown. A laser beam 3 exits the end of this channel and is directed at the surface of an object 2. A system of this type can, for example, be used to change the curvature of contact lenses or can be used for photorefractive keratotomy in which the curvature of the cornea of a human eye can be corrected by means of the effect of the laser radiation in removing the biological tissue of the cornea.

[0042] It is assumed that during the ablation process, an energy input into the tissue of approximately 0.5 watts occurs. In the process, a majority of the energy is used for the ablation, but a considerable portion is converted to undesirable thermal, acoustic and fluorescent energy. The thermal loss portions would mainly disrupt the removal conditions since it influences the tear film, i.e. the moisture on the cornea, and the hydration characteristics of the cornea itself.

[0043] In order to attain a defined removal rate and thus the possibility of a defined shape of the cornea surface, the objective of the invention should be to lessen or if possible entirely remove undesired influences on the ablation conditions, by keeping the climatic environmental conditions constant.

[0044] According to the invention, to this end a tubular channel 4 is provided that is connected to an air conveyor (not shown) via a connection fitting 5 and a connecting line connected to it (also not shown).

[0045] The air conveyor feeds air to the tubular flow channel 4, and this air exits the flow channel 4 through discharge openings 6.

[0046] Here, the discharge openings 6 are arranged such that the flow directions 7 of the discharging air, which make an acute angle with the laser beam 3, are directed toward the surface of the object 2.

[0047] Flow channel 4 is circular and arranged centrally around the laser beam 3, whereas the discharge openings 6 are distributed radially symmetric around the laser beam so that the flow directions 7 as a whole form approximately a circular cone surface. The laser beam 3 passes through the center of this cone surface.

[0048] The distance of the flow channel 4 to the object 2 is such that the peak of this circular cone surface coincides approximately with the point at which the laser beam 3 meets the object 2.

[0049] This results in the flow directions 7 meeting approximately at the point where the laser beam 3 meets the object 2 and counteracting one another such that the flow directions 7 reverse, with the flowing air being discharged radially outward. This results in the ablation by-products such as smoke and ablated tissue particles being collected by the air stream and discharged in the radial direction along with the air.

[0050] This results as much as possible in the ablation products not passing through the laser beam 3 and thus not being able to impair the intensity of the laser's radiation.

[0051] Also, according to the invention, the air conveyor is coupled to a climatization device for the air fed to the flow channel 4. The climatization device is designed such that the temperature and relative humidity of the air can be regulated. Also, means are present with which the temperature values, values for the relative humidity and also values for the amount of air fed per unit time can be pre-established prior to the beginning of the ablation process. To this end, both the air conveyor as well as the climatization device is equipped with means to enter commands, such as keys, switches or rotating knobs, which are part of a control system. Devices of this type for the purposes of air feed and climatization of the air, as well as corresponding input means are known from the state of the art and therefore do not need to be explained here in more detail.

[0052] If, for example, as a source for the laser radiation an Excimer laser, preferably an MEL 70 G-Scan, is provided that issues the very sensitive laser radiation having a wavelength of 193 nm, the invention can provide, by pre-selection of a temperature of 37 C., a relative humidity of approximately 100% and a flow velocity of approximately 0.5 m/s, that the climatic environmental conditions surrounding the point of removal during the ablation process are held constant within a relatively narrow range. This also ensures a relatively constant rate of removal, with the required precision being attained during shaping as much as possible.

[0053] In addition, both the air conveyors as well as the climatization devices can also be equipped with means to maintain the pre-selected values. Devices of this type that maintain the temperature, the humidity as well as the flow velocity of the air, are also known from the state of the art and are therefore not explained here in more detail.

[0054] In an exemplary embodiment shown in FIG. 2 of the inventive system, in addition to the tubular flow channel 4, there is another tubular flow channel 8 provided that also encircles the laser beam 3 similar to flow channel 4, said channel 8 being located at a larger distance than flow channel 4 from the object 2, however. Also, in contrast to flow channel 4, it is not connected to an air feed device to feed air, but to a suction device (not shown in the drawing) that is connected to the flow channel 8 via a hose line (also not shown in the drawing) and via a connection fitting 9. Flow channel 8 has inlet openings 10 that are positioned essentially in the same arrangement as the discharge openings 6 in flow channel 4.

[0055] When this system is operated, an air stream is produced around the laser beam 3 that is first directed out from the discharge openings 6 of flow channel 4 toward the object 2 and then from the object 2 to the inlet openings 10 of flow channel 8.

[0056] In contrast to the embodiment variation according to FIG. 1, in this arrangement the ablation by-products are not discharged radially from the laser beam 3 outward, but (approximately in the opposite direction to the laser beam 3) are discharged through the inlet openings 10 into flow channel 8 and from there to the suction device. The result of this is that the ablation by-products (smoke, tissue particles) are not able to pass through the laser beam 3 and also do not contaminate the environment at the point of ablation or lead to odors endured by the person being treated.

[0057] In the process, the air exits the discharge openings 6 with a prescribed constant temperature, relative humidity and flow velocity and in this way provides for the defined climatic conditions at the object 2.

[0058] In contrast, in another embodiment of the system, instead of the temperature and humidity values of the air as well as its flow velocity being held constant during the removal process, measurement sensors can be provided to detect temperature and humidity values in the direct vicinity of the point of removal and for these sensors to be connected to the air conveyor and the climatization device via a control system.

[0059] This makes it possible to react to ongoing changes in the climatic environmental conditions very quickly by having the temperature of the flowing air or even its relative humidity increased or lowered based on the values detected so as to counteract the effect of the thermal dissipation within an even narrower range.

[0060] Examples for the arrangement of such measurement sensors are shown in FIG. 3. Here, for example, a light scattering measurement device is provided to measure the humidity value at the point of removal, said device consisting of a laser diode 11 that directs light in the visible or infrared spectral range at the object 2, and a photo detector 12 that receives the reflection of the laser radiation issued from the laser diode 11 and whose output signals are a measure of the humidity at the cornea surface.

[0061] The photodiode 12 is connected via a signal path 13 to the climatization device through an evaluation and control circuit (not shown).

[0062] The reflected scatter intensity of the laser radiation issued from the photo diode 11 essentially determines whether there is still a film of moisture present on the cornea surface or the extent to which it has already dried out.

[0063] To collect temperature values from the direct vicinity of the point of removal, a commercially available temperature meter can be used, such as a thermal camera, with its direction of measurement such that the temperature values are detected at the point of removal and are forwarded via a signal path 14 to the evaluation and control circuit that is connected to the climatization device.

[0064] This invention permits, in addition to the suctioning of the ablation by-products, a defined temperature and humidity to be established by means of a compact system in the direct vicinity of the treated location, for example of an eye being treated through photorefractive keratotomy. In this way the removal characteristics of the cornea tissue are held constant. As shown in detail, steady-state equilibrium of air humidity and temperature is established during the laser treatment by means of controlled feed and withdrawal of tempered, humidified air at defined flow velocity in the direct vicinity of the treatment location.

[0065] In a preferred embodiment, during the entire ablation process saturated air is used that is heated approximately to body temperature, and that has a relatively low flow velocity of approximately 0.5 m/s. A moisture film present on the object 2 before beginning the removal process first requires a low ablation rate. Since, however thermal energy is released during the ablation process, this leads to the moisture film increasingly drying out and as a result the ablation rate increasing. This is counteracted in the manner described.

[0066] When working with an Excimer laser as the radiation source for a wavelength of 193 nm, it should be noted that the absorption for this wavelength is considerably higher in water than in air or in another blanketing gas, such as nitrogen. Consequently, it is clearly necessary to counteract the tendency to dry out so as to maintain constant removal conditions. Insofar as this is concerned, the system according to the invention makes it possible to always establish temperature and humidity equilibrium between the object (contact lens or cornea) and the climatized environment at its surface. Variables such as an initially thick moisture film as well as increased drying out due to the energy input are compensated using the means proposed by the invention.

[0067] FIG. 4 shows another possible embodiment concerning the feed and withdrawal of a climatized air stream 7 directed toward and away from the surface of the object 2. As FIG. 4 shows, the end of the tubular channel 1 facing the object 2 has a conical section 16 with two chambers 17 and 18 that enclose the laser beam 3 concentrically. Chamber 17, which opens up into an annular discharge opening 19 is connected to an air climatization and conveying device (not shown in the drawing) that produces climatized air in chamber 17 at elevated pressure. The annular discharge opening 19 is designed such that the climatized air stream 7 discharged due to the overpressure is directed at the surface of the object 2 where it is reflected.

[0068] Chamber 18 is connected to a suction device (not shown in the drawing) that produces a reduced pressure. It has an annular inlet opening 20 through which the air stream 7 reflected by the surface of the object 2 is sucked and flows into the chamber 18 and is discharged to the suction device.

[0069] Hose lines can be provided to connect both chamber 17 to the air climatization and conveying device and to connect chamber 18 to the suction device, both of which are connected via connection fittings. The air climatization and conveying device and the suction device can be commercially available assemblies so that a more detailed explanation is not necessary here.

[0070] As already accomplished with the system according to FIG. 2, the embodiment according to FIG. 4 also permits the ablation products to be suctioned off without them passing through the laser beam 3 and thus impairing the intensity of the laser radiation. Because of the climatized air stream 7, the surface of the object 2 cannot dry out, resulting in uniform removal conditions being ensured.

[0071] Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

[0072] Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.

[0073] Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended.

[0074] Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein.

[0075] For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. 112(f) are not to be invoked unless the specific terms means for or step for are recited in a claim.