KR100257782B1 - Target domain profiling of target optical surfaces using excimer laser photoablation - Google Patents

Abstract

A method for inducing a cylindrical force to an optical surface comprises providing a target optical surface to a device capable of indexing the position of the target along a beam path of a laser capable of optically cutting the target material, and along the at least one axis. Passing the target through the area of the laser and controlling the product of the laser intensity over time to control the amount of ablation of the target along at least one axis of the target.

Description

Method of Forming Region Profile of the Surface of Optical Member Using Excimer Laser Light Abrasion

1 is a graphical diagram showing the cross-sectional shape of an excimer laser beam, showing the energy distribution of the excimer laser for X and Y angular coordinates.

2 is a perspective view of an apparatus for scanning a laser beam used in the present invention along the surface of a blank of a contact lens member.

3 is a schematic illustration of optical members defining the dimensions needed to show the relationship between an ablation profile and a scanning scheme.

3 (a) is a schematic explanatory diagram of an optical member showing an area and a parameter used to exhibit an ablation effect with respect to the radius of curvature of the surface of the optical member.

4 shows the surface of a contact lens having a surface ablated by a shelf.

5 and 6 show an interferogram of a toric contact lens constructed with a treatment method according to the invention.

7 is an interference photograph of a torus contact lens on the market.

8 is an interference photograph of a lens having a spherical power varied according to the present invention.

* Explanation of symbols for main parts of the drawings

1: beam 2: reflector

3: fixed angle mirror 4: scannable mirror

5: lens 6: optical member

Various methods are known for forming the surface of an optical member. The oldest known method among these will be a method of using a shelf to change the shape of the surface of the optical object. This method, of course, dates back to the manufacture of the first lens and is still in use today.

In addition, various methods have been developed for forming the surface of the optical member. However, these methods also rely on lathe technology to make mold pieces used to form the finished optical object. Recently, the idea of using a high energy laser to selectively ablate the surface of an optical object has been proposed.

The present invention provides an efficient and precise means of using an excimer laser to selectively alter the surface of an optical object.

The present invention includes a method of modifying the shape of the surface of an optical object. This is particularly useful for making optical objects with toric surfaces that are more accurate and accurate than ever possible.

The present invention relates to a novel method of modifying an optical surface by varying the refractive power of a spherical or cylindrical shape of the optical surface. This new method uses high energy radiation to ablate material from contact lens black in a controlled manner to produce the desired contact lens shape. In particular, the method uses the advantages of an excimer laser beam with a relatively constant pulse beam intensity to sweep over an area of the surface of the optical member. By controlling the speed of the beam swept relative to the member along a given axis, the amount of ablation performed along that axis at a given point can be controlled.

The beam from the excimer laser has a rectangular cross section and has a nearly uniform radiant intensity about one axis of symmetry. Also the intensity of this beam is not completely uniform, but its profile can be measured and described in the above processing. The main feature of the beam is that the pulse intensity profile is substantially fixed. The present invention uses this feature to control light ablation of the surface of the optical member.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 shows a general cross-sectional view of an excimer laser having an intensity distribution of the laser along the X and Y coordinates. As will be appreciated, the intensity of the beam about the X axis is substantially uniform throughout, excluding the edges. The present invention describes a method of cutting the beam edges and as a result provides a beam to the member with uniform strength.

Controlling the ablation of the complete lens surface is accomplished by scanning the beam along the Y axis relative to the surface of the optical member to be altered. When such beam scanning is performed at a constant speed, as shown on the surface of the optical member, the effect of simply expanding the beam profile to the Y axis occurs.

It should be noted that the excimer laser operates with short pulses of about 20 nanoseconds and has a very constant total pulse energy from pulse to pulse. The intended ablation process requires many pulses to form the desired object. During ablation, which typically lasts from 0.1 to 30 seconds, the excimer laser beam region can form a linear or nonlinear, gentle, continuous ablation profile along one axis of the member in a constant manner relative to the surface of the optical member. have.

Scanning the excimer laser beam can be accomplished by at least two means. FIG. 2 shows that the beam 1 is reflected at 90 degrees by the reflector 2 fixed at 45 degrees. The beam is then reflected 90 ° by the fixed angle mirror 3, which may be either a mirror with full reflectivity or a mirror with partial transmission. In case such a mirror has a partial transmission, mirror means for examining the beam profile of the excimer laser can be provided. The means for moving the scannable mirror 4 in parallel with the initial beam path causes the mirror to move the beam from its incidence path to scan the beam area against the surface of the optical member.

Another method of practicing the present invention uses a mirror that sweeps the beam area with respect to the surface of the optical member by varying the angle of incidence of the reflector to the beam. Instead of the fixed angle mirror 3 in the device shown in FIG. 2, the mirror can be placed on the axis of the axial plane swept against the member by a laser. Although using a combination of reflectors that scan linearly with the lens placed on the axis, other means, such as the linear servo-mechanism shown in the figures, will not be necessary for effective beam scanning.

Assuming that the intensity of the laser and the pulse velocity of the laser are substantially constant, the optical abrasion is proportional to the speed when the reflector 2 moves along the Z axis, and the surface of the optical member that is ablated under a constant speed of the reflector Is made uniform for

Since light abrasion as a function of Y is proportional to the instantaneous speed of the beam along the Y axis (or the speed of the mirror along the Z axis), the light abrasion is controlled by controlling the speed profile of the mirror when sweeping the beam over the member area. You can control the degree.

FIG. 2 also shows a device with a lens that reduces the beam to increase the intensity of the beam when it enters the optical member 6. It is to be understood that this device is actually optional in the present invention and that the beam can be used in the present invention without reducing its cross-sectional area.

A mathematical expression showing the relationship of ablation to scanning of a pulsed beam is as follows.

1) T = K · H · N / V

Where T is the thickness of the material removed, K is a constant, H is the repeatability (pulse rate) of the laser, N is the number of scans, and V is the instantaneous speed of the beam.

When a continuous laser is used, the above relation can be expressed as follows.

2) T = KlN / V

Where K1 is a constant. K and K1 are constants for the ablation of a given material under certain circumstances. Therefore, these constants depend on the composition of the optical member, the ambient atmosphere condition of the optical member, the wavelength of the beam and the intensity of the beam.

If the scanning speed is not constant, ablation performed along the axis of the optical member can be defined as follows.

3) Delta T = KHN (Vl-V2) / (VlV2)

Where Vl and V2 are the beam velocities at points Pl and P2 and delta T is the difference in material between the two points (see also FIG. 3).

In order to change the radius in the vertical plane with delta T, the removable delta T must match the difference in the saggital delta S between the original radius and the new radius at the total distance to all points on the vertical plane. See also 3 (a)).

4) Delta 5 = Delta RYo ² / 2R ²

Here, since Y is the distance from the center of the lens to the point P on the vertical plane, assuming that P1 is the initial position at the center of the lens,

5) Delta R = (2KHR ² ) / Vo

The change in the cylindrical power (cylinder power) is K2 · H · N, where K2 is a constant independent of the radius of the optical member. This can ablate a lens that has a different radius of curvature in the Y axis and a radius of curvature in the X axis, that is, a toric lens. In addition, the change of the magnification of a cylindrical shape does not depend on the initial curvature of an optical member. For example, a scan that changes the magnification in a spherical lens to 0.25 diopters will cause the curvature of the surface of the optical member to change to the same degree irrespective of the initial radius of curvature of the member.

Of course, the ablation profile is controlled by the product of the beam intensity profile function including the pulse rate function and the scan rate profile function. In this case, the constant beam pulse velocity is proportional to ablation as a ratio of V + A / Yo ² , where V is the instantaneous velocity of the beam being scanned, A is the ablation constant, and Yo is the axis of symmetry of the cylindrical shape caused by the optical member. Distance from the beam, such ablation causes a cylindrical component to be caused on the surface of the optical member.

To combine the ablation profiles, the velocity functions are combined so that the resulting profile Vr at each point is 1 / Vr = (1 / V1 + 1 / V2).

Also, because the beam cannot be scanned at infinite speed, the abrasion should be accounted for at all points scanned at a given constant pulse rate. Thus, all ablation profiles have a constant maximum and minimum ablation component made of them.

The desired ablation profile necessary to induce a change in the magnification of the cylindrical shape can be achieved by controlling the pulse velocity of the laser. Achieving a desired ablation profile depends on controlling the product of the scan rate as a function of time and the pulse rate of the laser as a function of time.

Alternatively, the ablation profile can be controlled at a constant sweep speed by controlling the pulse rate of the laser. It is evident that the repetition rate H can be varied instead of or with the scan rate for different points on the surface. The total amount of material removed at each point is proportional to the repetition rate as shown in equation (1). If the velocity remains constant, the change in repetition rate needed to generate a given profile can be accurately and easily derived in the same way as the velocity profile using Equation 1 at each point.

If various types of profile modifications are made at a constant rate, the repetition rate distributions for each individual profile at each point are added together, and the resulting repetition rate distribution produces a composite profile.

If the speed changes with the repetition rate, the H-V ratio should be used to determine the etch depth at each point in accordance with equation (1). If multiple profile types are added together, the repetition rate H or velocity V must be configured equal to each profile distribution for each point. This is a simple variant using equation (1). Since each point can be processed separately in further processing, it is evident that further processing can still be used where the repetition rate and speed change at every point in the distribution. However, the function generated with respect to repetition rate and speed must be continuous for the area to be etched.

The means used to control the movement of the scanning mirror can be provided by a servo-mechanism driven by a stepper motor controlled via digital electronic means. As a result, the velocity profile may be controlled through a computer program and may be in any desired form.

Another method of practicing the present invention is to move the surface of the optical member in a controlled manner along the X axis with respect to the laser beam area to perform controlled ablation. This differs from the approach shown in FIG. 2 in that it moves the member rather than the beam.

Unlike the shape of the particular device described above, the shape of the fixed optical member is determined by the shape of the initial optical member and the degree of abrasion, expressed as a function of X and Y on the member surface. For example, it is possible to form a lens from a contact lens button (disk of contact lens material). In order to form the disk into a finished lens, a significant portion of the material has to be ablated, which takes considerable time. On the other hand, the contact lens material may be substantially in the form of a spherical contact lens. Therefore, when making a toric lens with a relatively low toricity, only a small amount of ablation along one axis can be used to convert a lens with a spherical magnification into a toric lens, so that the time required to make the lens Minimum. Other surfaces that can be modified include corneas, intraocular lenses, glasses, and other optical elements.

One of the major advantages of the present invention over conventional methods of forming toric contact lenses is that the method of the present invention can make toric lenses having a relatively low degree of toricity better, in particular. This is even more so when R curvature x, which is the radius of curvature for the x axis, is close to R curvature y, which is the radius of curvature for the y axis. Another advantage of the system is that it can produce highly accurate toric lenses of high cylindrical shape. That is, the two radii formed in the toric lens can be specified with greater precision than can be obtained through the state of the conventional lathe technology.

As will be appreciated by those skilled in the art, the present invention can be used to form the front and back surfaces of toric lenses. This method can also be used to produce lenses of good quality spherical lenses and lenses with double focus and other shapes. For example, a bifocal lens can be manufactured by masking an area of the optical member and changing the spherical magnification with respect to the unmasked area, resulting in a lens having two areas with different magnifications.

The method may be used for plastic contact lens materials, as long as the radiation source used has sufficient energy and a suitable wavelength to induce light ablation. Specific materials include poly 2-hydrooxyethyl methacrylate (pHEMA), poly N-vinyl-2-pyrrolidone (pNVP), polymethyl methacrylate (pMMA), as well as other contact lens materials known to those skilled in the art. Non-hydrate forms of copolymers for such compounds. The gas permeable material may also be used with contact lens materials of silicon, in particular materials of fluorosilicone.

The choice of radiation source used for a particular type of lens material is influenced by the following factors: That is, the critical intensity and ambient atmosphere conditions needed to generate the photoabrasion mechanism to give an advantage over conventional attenuation modalities that depend on the emission wavelength, wavelength plot and material type (part of the ablation pattern is optimized by the presence of the reactant gas, It requires an "inert" atmosphere).

In addition, it has been found that the treatment of abrading plastic biomedical materials produces different kinds of stress on the surface of the material that is sometimes ablation. Surprisingly, this effect can be improved by constant ablation of the entirety of the front surface of the optical member. By removing the material to a certain thickness, the material becomes a material and its surface is homogeneous.

The following examples illustrate several applications of the present invention. These embodiments do not represent all the possibilities of the present invention for forming the surface of the optical member. Although the same treatment used to form the contact lenses can generally be used to form the optical surface of the eye, the embodiment for forming the cornea is not presented. In this case, the cornea will be considered the light surface of the fascia member.

Example 1

An unhydrated soft contact lens material having a spherical back surface is disposed in the device shown in FIG. 2 as the surface of the optical member. This lens is made of a polymecon material, which is widely used to make soft contact lenses. The back surface of the lens is scanned by the excimer beam when the scanner is scanned along the z-axis in a nonlinear manner that takes more material from the edge of the lens than the center of the lens along one axis. The lens is shown before being scanned by the excimer laser to be close to a perfect sphere by interferometric means. 4 shows the interference photograph of the lens before laser ablation. 4 shows that the entire back surface of the lens is within several interference fringes when it is spherical, which shows a deformation of less than 1 micron with respect to the surface of the lens.

By the method of the present invention, after scanning with a laser, this lens becomes a toric lens. 5 and 6 are interference photographs of two axes of the rear surface of the lens. As is evident for each axis, the lens is in several interference stripes having a given radius about that axis and also having a different radius about the other axis. This indicates that the two radii of the toric lens are exactly what is expected. In this case the radius of the two expected axes is 6.996 mm and 7.115 mm and the actual obtained radii are 6.991 and 7.108 mm. For comparison, interference photographs of commercially available toric lenses are shown in FIG. At least 20 interference fringes can be seen here on the back surface of the lens.

Example 2

Lens material having a spherical back surface is mounted in the apparatus shown in FIG. The lens is scanned along the axis by a function that changes the magnification of the cylindrical shape of the lens with respect to the axis. The lens is rotated 90 ° and scanned again using the same scanning function used when making the first scanning sweep. Thus, coherent analysis of the lens reveals that even if the lens has a different power than the original material, the spherical power of the lens changes and the lens still has a nearly complete back surface. Shown in FIG. 8 is an interference photograph of the ablated lens. As shown in FIG. 8, there are a few interference stripes on the entire back surface of the optical member of the lens. In addition to the corresponding calculated magnification change of several diopters in the finished hydrated lens, the initial and final radii of a series of nine lenses with spherical radii are changed in the manner shown in Table 1.

TABLE 1

Example 3

A lens material having a spherical back surface is mounted in the apparatus shown in FIG. The lens is scanned twice about one axis to form a cylindrical shape, which is then rotated 90 ° and scanned once with the same parameters. These cylindrical components are added to produce a spherical change in magnification and a resulting cylindrical change. The initial radius of the surface is 7.470 mm. After two sets have been scanned, the surface has two radii of 7.382 and 7.292 on a vertical line, which results in a 0.008 mm change in spherical radius with an additional 0.090 mm cylinder.

Claims (10)

Providing a contact lens material to a device capable of indexing the position of the lens with respect to the beam path of an excimer laser capable of optically polishing the material constituting the contact lens material; Scanning the area of the excimer laser with respect to the contact lens material along at least one axis and controlling the product of the time and the beam intensity to control the amount of ablation of the contact lens material along at least one axis of the contact lens material A method for producing a contract lens having a magnification of a toric body, the method comprising: Contact lens, characterized in that for removing the stress caused by the contact lens by ablating material selectively and non-uniformly with respect to the surface of the lens, including the step of uniformly cutting the entire surface of the contact lens with light abrading means. Surface treatment method. And controllably sweeping the area of the surface of the optical member by a predetermined sweep velocity profile with a high energy beam in a predetermined manner to selectively ablate the material along the axis in a predetermined manner. Method of surface formation. 4. The sweep speed profile of claim 3, wherein the sweep speed profile is defined by the general formula V = A / Y0 ² , where V is the instantaneous speed of the beam when the beam is scanned, A is the ablation constant, and Yo is caused in the optical member. And the ablation causes the cylindrical component to occur on the surface of the optical member. a) controllably sweeping the surface area of the optical member with respect to axis X in a predetermined manner in accordance with a predetermined sweep speed profile, thereby selectively ablation of material along the axis X in a predetermined manner; and b) repeating step a along an axis perpendicular to the axis X used in step a. 4. The method of claim 3, wherein the sweep speed profile is selected to add a prism with respect to the surface of the optical member. 4. The method of claim 3, wherein the sweep speed profile is defined to remove the prism from the surface of the optical member. 4. The method of claim 3, wherein the method is used to make toric contact lenses from contact lenses having spherical power. 4. The method of claim 3, wherein the method is used to reshape intraocular lenses. 4. The method of claim 3, wherein the method is used to reshape the corneal surface.