Compact scanning lens for use in an ophthalmic laser therapy device

Abstract

The present invention relates to a single-stage scanning lens (10, 100) for use in an ophthalmic laser therapy device (1) with a scanner (170), for guiding laser radiation (90, 190) from the scanner (170) into a focus (95, 195) in a processing volume (80, 180). To ensure high-quality sections, a large number of optical elements are required, which require a large amount of installation space. The object of the present invention is therefore to provide a scanning lens (10, 100) with a compact design, while at the same time achieving simplicity of the optical components used. The problem is solved by a single-stage scanning lens (10, 100) with one or more diffractive optical elements (130), wherein the one or more diffractive optical elements (130) each have a diffractive structure whose respective associated refractive power is a maximum of 10 dpt. The task is further solved by a corresponding ophthalmological laser therapy device (1).

Description

[0001] The present invention relates to a single-stage scanning lens for use in an ophthalmic laser therapy device with a scanner, for guiding laser radiation from the scanner to a focus in a treatment volume. The invention further relates to an ophthalmic laser therapy device.

[0002] Refractive errors in the human eye have long been corrected with lenses in the form of eyeglasses. However, in recent years, various approaches have been developed to correct refractive errors through modification of the cornea. The modification alters the curvature of the cornea and thus the refractive power of the eye. This is typically achieved by removing corneal tissue. By removing corneal tissue from the eye, the refractive power of the cornea is altered in such a way that – taking into account the overall imaging properties of the eye – the refractive error is reduced or even completely eliminated.

[0003] Carl Zeiss Meditec AG has developed a particularly gentle corneal modification procedure called SMILE. In this procedure, a femtosecond laser creates flat incisions in the cornea that enclose a lenticule-shaped piece of corneal tissue. This lenticule is removed from the cornea through a similarly created access incision. This creates a change in the curvature of the anterior surface of the cornea (i.e., at the interface between the cornea and air). This change in curvature alters the refractive power of the cornea, thus correcting any refractive error.

[0004] To create the flat incisions in the cornea, laser radiation for treating the eye is focused within the tissue - i.e. below the surface of the tissue - in such a way that optical breakthroughs are created in the tissue. Various processes initiated by the laser radiation take place sequentially in the tissue. If the power density of the radiation exceeds a threshold, an optical breakthrough occurs, which creates a plasma bubble in the material. This plasma bubble grows after the optical breakthrough occurs due to expanding gases. If the optical breakthrough is not maintained, the gas created in the plasma bubble is absorbed by the surrounding material and the bubble disappears again. However, this process takes much longer than the formation of the bubble itself. A plasma bubble that separates previously bonded layers of material is usually referred to as photodisruption.For simplicity, these processes are summarized here under the term "optical breakthrough." This term encompasses not only the actual optical breakthrough, but also the resulting effects in the material. If a large number of optical breakthroughs are created next to one another in the fabric, a flat cut (a cut surface) can be created.

[0005] The deflection of the laser beam in the volume to be treated (e.g., the cornea) is typically achieved using scanners. These are designed to deflect the laser beam laterally (in a plane perpendicular to an optical axis of the laser therapy device) and preferably also to shift the focus axially (parallel to the optical axis; using axial or z-scanners). Tilting mirrors (also called scanning mirrors) are often used as lateral scanners; these can be tilted around one (or more) axes to deflect the laser beam. To keep processing times short (especially when treating one eye), the scanning mirrors used must be moved very quickly. In principle, this is easier with very small mirrors than with large mirrors (due to the mirrors' moment of inertia) - however, smaller mirrors must be tilted very far to cover the entire field to be treated.The reason for this is that the product of tilt angle and mirror diameter is determined indirectly via the processing field and the numerical aperture (light conductance or etendue). In practice, the mirror size, i.e., the beam diameter at the mirror, must therefore be chosen as a compromise between speed and processing field.

[0006] When performing the described refractive correction procedure, precise positioning of the laser beam is of particular importance. Movement of the treated eye must be avoided as much as possible. A contact element (also called a contact lens) is typically used for this purpose. One side of the contact element is brought into contact with the eye. The eye is optically coupled to the therapy device via the contact element; at the same time, the eye is fixed in place.

[0007] To guide the laser beam from the scanner to the contact element, a lens, also known as a scanning lens or scanning optics, is used. The scanning lens's task is to capture the laser beam provided by the lateral scanner (via the tilt angle range) and, if applicable, by the z-scanner (via a z-focus range) and to guide it toward the processing volume so that a focus can be created there.

[0008] Apart from the already mentioned tilt angle range of the scanner and the size of the processing field (or processing volume) that must be covered, there are further requirements for a scanning lens, as described below: Typically, laser-assisted refraction correction of the eye (as well as in material processing) uses short laser pulses with pulse widths between 50 fs and 1000 fs. Strong focusing of the pulses and the associated spatial and temporal concentration of the energy of a pulse result in the non-linear interactions described above with the material being processed in a very spatially limited area. This ensures fine cuts without damaging surrounding material. Depending on the type of material processing and the nature of the interaction with the material being processed, the central wavelength of the laser radiation used can be in the near ultraviolet spectral range, as well as in the visible or near infrared spectral range. The central wavelength can therefore cover a range from approximately 350 nm to approximately 1500 nm.Due to the finite pulse length, the laser radiation used always also has a finite spectral full width at half maximum around the center wavelength. Depending on the pulse length, this ranges, for example, between 0.5 nm and 50 nm. The scanning lens must therefore be designed for the center wavelength used as well as for the entire spectral width of the laser pulse to ensure that a laser pulse does not "smear" spatially or temporally. This is the only way to ensure that the desired interaction with the material being processed is achieved across the processing volume—for example, photodisruption in the cornea of ​​an eye.

[0009] In laser-assisted refractive correction, the laser energy delivered to the eye during treatment should be kept as low as possible, while still exceeding a disruption threshold. To achieve this, focusing the laser beam on the smallest possible volume is advantageous. This results in the requirement for a large numerical aperture for the scanning lens, while simultaneously avoiding aberrations to ensure high-quality sections.

[0010] Depending on the application, it may be desirable to simultaneously observe or monitor the volume being processed. For this purpose, the scanning lens can be equipped with a beam splitter, through which light emitted (e.g., reflected) within the processing volume is coupled to an observer or a sensor (e.g., a camera). The space required for beam splitting is then unavailable for additional optical elements.

[0011] The available space for optical elements in a scanning lens is further limited by the fact that a minimum distance must be maintained from a scanning mirror to avoid collisions. In the case of ophthalmic laser therapy, the geometry of the eye socket, as well as the patient's nose and temple, must also be considered; this results in requirements for a minimum working distance or the free diameter of optical elements.

[0012] Despite the mentioned constraints regarding the installation space, it is important to ensure good optical correction of the focused laser beam.

[0013] On the one hand, aberrations for the laser wavelength lead to lower power at the focus, thus requiring higher pulse energy to reach the threshold for material processing. On the other hand, the laser pulse has a finite spectral width due to the short pulse duration. However, the scanning lens must be free of chromatic aberrations in this spectral interval—it must therefore have achromatic correction. Otherwise, the pulses broaden as they pass through the scanning lens, and temporal focusing is lost. This task typically requires many combinations of positive and negative lenses made of crown and flint glass.

[0014] Therefore, scan lenses with an intermediate image are known in the prior art; these are so-called "two-stage" scan optics (see, for example, US 8702770 B2). The intermediate image provides more installation space, which can be used for lenses of different refractive powers, refractive indices, and Abbe numbers in order to meet the requirements described above. However, it is desirable to keep the number of lenses low in order to keep the material costs of lenses and mounts as well as the adjustment of the optical components low, and to minimize the installation space of the scan lens. DE 10 2004 009 212 B4 therefore proposes a scan lens that does not require an intermediate image. However, this uses two diffractive optical elements (DOEs) to ensure the required optical correction of the focused laser beam. The DOEs are highly sensitive with regard to their installation position and manufacturing tolerances.

[0015] The object of the present invention is therefore to provide a scanning lens with which the disadvantages of the prior art are eliminated and with which, in particular, a compact design can be achieved while at the same time maintaining the simplicity of the optical components used.

[0016] According to the invention, the object is achieved by the features of the independent claims. Preferred developments and refinements are the subject of the dependent claims.

[0017] A first aspect of the invention relates to a single-stage scanning lens for use in an ophthalmic laser therapy device with a scanner, for guiding laser radiation from the scanner to a focus in a processing volume. A single-stage lens is understood to mean that it has no intermediate image, in contrast to a two- or multi-stage lens, which has at least one intermediate image. An ophthalmic laser therapy device is designed to treat a patient's eye using laser radiation. The laser radiation is bundled at a focus in order to exert its therapeutic effect there; for example, by severing tissue such as the cornea of ​​the patient's eye. For therapy, it is generally desirable to be able to shift (deflect) the focus; for this purpose, the ophthalmic laser therapy device has a scanner.The scanning lens captures the laser beam deflected by the scanner and directs it to a focus. The laser beam is guided in an imaging manner. The volume into which the focus of the laser beam is transferred when the scanner is deflected is called the processing volume. This can be a portion of the patient's cornea. The scanning lens encompasses all optical elements located in the laser beam path between the scanner and the material to be processed, including the processing volume (e.g., up to the eye).

[0018] The scanning lens has an entrance lens facing the scanner. This entrance lens is the first optical element encountered by the laser radiation after leaving the scanner during operation of the ophthalmic laser therapy device. This can be, for example, a single lens, a lens group, a mirror, a prism, or a plane-parallel plate.

[0019] The scanning lens also includes an exit lens facing the processing volume. The laser beam exits the scanning lens through the exit lens, from where it hits the material to be processed (the eye to be treated) within the processing volume. There is no other optical element between the material to be processed and the exit lens. The exit lens can be, for example, a single lens, a lens group, a mirror, a prism, or a plane-parallel plate.

[0020] In addition, the scanning lens has one or more diffractive optical elements (also called DOEs). One diffractive optical element has a diffractive structure, wherein the refractive power associated with the diffractive structure is a maximum of 10 dpt, preferably a maximum of 7 dpt, particularly preferably a maximum of 5 dpt or 3 dpt, or the plurality of diffractive optical elements each have a diffractive structure, wherein for each of the diffractive structures, the associated refractive power is a maximum of 10 dpt, preferably a maximum of 7 dpt, particularly preferably a maximum of 5 dpt or 3 dpt.

[0021] A diffractive optical element can be assigned a refractive power: The diffractive (diffracting) effect of the diffractive optical element is caused by the diffractive structure, which generates path differences between the partial beams. The path differences between the partial beams can be caused by "grooves." For the purposes of this application, a diffractive optical element (DOE) is understood to be an optical element that, across its free diameter, uses a diffractive structure to generate a diffractive effect and generates a path difference between the partial beams. If the diffractive optical element is intended to achieve a focusing (or defocusing) effect, the diffractive structure can be described by a rotationally symmetric groove number polynomial. The DOE therefore has a ring-shaped grating structure.The grating structure is generally not periodic across the radius; rather, a periodicity equal to the square of the radius can occur. As a result, each “ring” of the diffractive optical element has the same area. If the periodicity deviates across the radius, the number of grooves (rings) across the radius (= groove density) inevitably changes. In order to exert a diffractive effect, the DOE (or all of the DOEs) must have at least two grooves across their free diameter. The free diameter of the DOE is the area used for imaging light guidance when the scan lens is used in an ophthalmic laser therapy device. Typically, the DOE has a larger diameter, which can be used for mounting (e.g., in a mount) within the scan lens.The refractive power assigned to a diffractive optical element corresponds to the difference between the refractive powers of the optical element with and without the diffractive structure. If, for example, the diffractive structure is applied to a plane-parallel substrate, the substrate alone has a refractive power of 0 dpt (diopter). The refractive power assigned to the diffractive structure thus corresponds to the refractive power of the DOE. If the diffractive optical element is designed such that the diffractive structure is applied to a substrate that itself has a refractive power other than zero (for example, on a lens with a refractive power of x dpt), the DOE has a refractive power other than x dpt of (x+Δ) dpt (with Δ ≠ 0). The refractive power assigned to the diffractive structure is Δ dpt; it is also referred to as "additive refractive power" or "add power".

[0022] A maximum refractive power of 10 dpt is characterized by the fact that it results in only minimal beam deflection. The focal length f' corresponding to the assigned refractive power (as the inverse of the refractive power) is at least 100 mm. Similarly, maximum refractive powers of 7 dpt, 5 dpt, or 3 dpt correspond to focal lengths f' of at least approximately 143 mm, 200 mm, or approximately 333 mm, respectively.

[0023] The focal length f' in turn is related in a paraxial approximation to a furrow density v via the following formula: ƒ'=D2⋅ν⋅λ

[0024] Here, D is the free diameter of the diffractive structure. λ is the wavelength for which the focal length f' is calculated.

[0025] For a free diameter of D = 20 mm and an assigned refractive power of 10 dpt (corresponding to a focal length of f' = 100 mm), a groove density of v = 95 grooves per mm results at a wavelength of λ = 1050 nm. With an assigned refractive power of the DOE's diffractive structure of only 3 dpt, the groove density in the example decreases to approximately 29 grooves per mm.

[0026] The low maximum assigned refractive power and the resulting low maximum number of grooves of the DOE advantageously ensure that manufacturing and installation tolerances are improved compared to the state of the art. At the same time, the diffractive optical element, due to its anomalous dispersion, allows for the correction of chromatic aberrations. This also ensures a compact design of a scanning lens, as an intermediate image is eliminated.

[0027] It should be noted that a DOE (or multiple DOEs) can also deviate from rotational symmetry. An example of this would be an elliptical groove number polynomial. In this way, an astigmatic refractive power can be generated. Other groove arrangements are also conceivable. Additionally or alternatively, a grating structure (groove structure) can be present that deviates from a quadratic radius dependence. This makes it possible, for example, to realize a refractive power that varies across the radius of the DOE.

[0028] According to an advantageous embodiment of the scanning lens, all diffractive optical elements are arranged between the entrance optics and the exit optics. Along the beam path of the scanning lens, the laser radiation first passes through the entrance optics before reaching the DOE; the exit optics, in turn, are arranged downstream of the DOE in the beam path. This provides special protection for the one or more DOEs.

[0029] If the exit optics is designed as a contact element that allows the eye to be optically coupled to the therapy device (and simultaneously fixates the eye), this contact element is generally only usable once. Compared to a solution with a DOE on the contact element, this can result in cost savings. This applies to both the manufacturing costs for the contact element and the additional costs for the increased requirements for precise positioning of a replaceable contact element with a DOE.

[0030] In a further advantageous embodiment of the scanning lens, at least one of the diffractive optical elements is arranged in a half of the scanning lens facing the processing volume.

[0031] Typically, a single-stage scanning lens has a first section of optical elements that expand the laser beam; the laser beam is guided divergently there. In a second section of optical elements, the laser beam is guided convergently to focus it. Therefore, the half of the scanning lens facing the processing volume is understood to be the part of the scanning lens in which the laser beam is guided convergently.

[0032] If a DOE is located in the half of the scanning lens facing the processing volume, it can enable particularly efficient color correction, especially for both longitudinal and lateral chromatic aberrations. It can also be used to influence or correct higher-order aberrations.

[0033] According to a particularly advantageous embodiment of the scanning lens, it has exactly one diffractive optical element. This further reduces the costs of manufacturing a DOE as well as the effort required for installation and adjustment in the scanning lens.

[0034] In a further advantageous embodiment, the scanning lens is characterized in that the proportion of high-index lens materials is at least 50%, preferably at least 60%. The scanning lens thus has at least one lens with a lens material. A high-index lens material has a refractive index of at least 1.75, preferably at least 1.8 or 1.9. The refractive index for the center wavelength of the laser radiation is to be considered.

[0035] A “proportion” of high-refractive lens materials is understood to mean the number of lenses with high-refractive lens material to the number of all lenses of the scanning lens.

[0036] Lenses made with lens materials with high refractive indices generally produce fewer aberrations than those with low refractive indices. In addition, lenses made with high-index lens materials allow for smaller curvatures of the lens surfaces, thus requiring less space. This allows the scanning lens to be designed even more compactly. However, it should be noted that high-index lens materials exhibit dispersion that is unfavorable for lens design, leading to significant chromatic aberrations. Only in combination with at least one diffractive optical element is it possible to use such a high proportion of lenses with high-index lens materials and simultaneously correct chromatic aberrations.

[0037] According to a particularly advantageous embodiment, the scanning lens is characterized in that the entrance optics are a negative lens made of a high-refractive-index material. A high-refractive-index lens material has a refractive index of at least 1.75, preferably at least 1.8 or 1.9. A negative lens is also called a diverging lens; light incident on a negative lens parallel to its axis is deflected divergently. A negative lens has a virtual focal point on the incident light side. The negative lens can be biconcave; it can also have the shape of a meniscus lens.

[0038] By designing the entrance optics as a negative lens, the transmission length of the scanning lens can be increased, thus providing more space for additional optical elements required to correct image aberrations. For the problem described here, the transmission length is defined as the geometric distance between a scanner's rotational axis and the focus of the laser beam.

[0039] Additionally or alternatively, the scanning lens is characterized in that a partial optics located directly upstream of the exit optics has a cemented group with negative refractive power or consists of a cemented group with negative refractive power, wherein a lens of the cemented group facing the processing volume is a positive lens made of a low-refractive lens material. A low-refractive lens material has a refractive index of no more than 1.65, preferably no more than 1.55, particularly preferably no more than 1.5. "Upstream" means that there are no other optical elements in the beam path between the exit optics and the partial optics. The cemented group can consist of two or more lenses that are cemented together.Since the lens of the cement group facing the processing volume is a positive lens (also called a converging lens), but the cement group as a whole has a negative refractive power, the cement group includes at least one lens with negative refractive power.

[0040] The positive lens (converging lens) of the cement group facing the processing volume is preferably made of crown glass. Furthermore, the curvature of the lens on the side of the processing volume is preferably less than on the opposite side, which is a cemented surface. The cemented surface is preferably formed with a high-index flint glass in the form of a meniscus lens as the cementing partner. This combination ensures, on the one hand, a positive influence on the curvature of the processing volume (correction of field curvature) and, on the other hand, has a corrective effect on the chromatic aberrations of the scanning lens. Furthermore, the overall scattering effect of the cement group creates the necessary space for additional lenses inside the lens.

[0041] In a further advantageous embodiment, the scanning lens is characterized in that a refractive surface of the scanning lens is aspherically shaped. In other words, the scanning lens has at least one lens with a lens surface that is aspherically shaped. A refractive surface is understood to be an optical surface of a refractive optical element (i.e., a lens). Image aberrations can be corrected more easily with the help of aspheres.

[0042] Preferably, the scanning lens comprises only a single, aspherically shaped, refractive surface. This reduces the effort and cost of manufacturing a scanning lens.

[0043] Additionally or alternatively, the surface of the entrance optics facing the scanner is aspherically shaped. The laser radiation reflected by the scanner thus initially strikes an aspherical surface of the entrance optics. This allows for particularly efficient correction of aberrations. Particularly preferably, the surface of the entrance optics facing the scanner is the only aspherical surface of the scanning lens.

[0044] According to a particularly advantageous embodiment, the scanning lens is characterized by comprising a beam splitter. The beam splitter is designed to decouple light that can be emitted or reflected from the processing volume. The beam splitter is preferably arranged along the beam path between the entrance optics and the exit optics; the entrance or exit optics can also include the beam splitter or consist of the beam splitter. The beam splitting by the beam splitter can be achieved, for example, by selecting angles, separating wavelengths (i.e., spectrally), by polarization, and / or by a splitting ratio.

[0045] Preferably, the beam splitter is designed to allow the coupling of an observation beam path for observation of the processing volume. An observation beam path is understood to be an imaging light path from the processing volume through the exit optics of the scanning lens – possibly through additional optical elements – to the beam splitter, where the observation beam path is decoupled from the scanning lens and is no longer identical to the beam path of the laser radiation.Typically, the observation beam path continues after the beam splitter: one or more optical elements that are no longer part of the scanning lens join the beam splitter and end in an optic that is shaped as an eyepiece for direct observation of the processing volume, or they end in a sensor, for example a pixelated camera sensor such as a CCD or a CMOS sensor, to enable digital observation of the processing volume.

[0046] Typically, a smaller numerical aperture is required for the observation beam path (for the same field in the processing volume) than for the laser radiation. Therefore, the beam path intended for the (pulsed) laser radiation is preferably not deflected by the beam splitter; the laser radiation can therefore pass through the beam splitter in transmission – i.e., "stretched." The comparatively smaller installation space required for the observation beam path can be "folded" more easily than would be possible for the laser beam path. Since the use of a beam splitter in the beam path of the scanning lens requires installation space that is then unavailable for additional optical elements, the entrance optics are advantageously designed as a negative lens (preferably made of a high-index lens material).In this way, the transmission length of the scanning lens can be increased so that the space required for the beam splitter can be created.

[0047] In a further development of the scanning lens, the beam splitter is designed as a Bauernfeind prism. The Bauernfeind prism preferably has a wedge angle α of less than 30°, particularly preferably a maximum of 27° or a maximum of 25°. The wedge angle is the angle opposite the exit surface of the reflected beam.

[0048] A Bauernfeind prism is a reflection prism. It has a splitter layer on one side. The splitter layer is designed to separate the beam path for the laser radiation from the observation beam path. The laser radiation, coming from the scanner direction, enters the Bauernfeind prism on the side with the splitter layer and exits the Bauernfeind prism on the other side (without reflection). The observation beam path, viewed from the direction of the processing volume, enters the Bauernfeind prism on the side on which the laser radiation exits the Bauernfeind prism. The observation beam path is reflected at the splitter layer; this is where the beam splitting occurs. For this purpose, the splitter layer is preferably designed for spectral separation, for example, as an edge filter.The reflected observation beam re-enters the same side of the Bauernfeind prism where it entered. Here, the observation beam is redirected by total internal reflection (TIR). Finally, the observation beam exits the Bauernfeind prism on its third side. This side is opposite the wedge angle α.

[0049] Typically, a "classic" Bauernfeind prism has a wedge angle of 30°. By using a Bauernfeind prism with a wedge angle of less than 30° (or a maximum of 27° or 25°), the space required for the beam splitter can be minimized. A Bauernfeind prism with a wedge angle of less than 30° is referred to in the application as a modified Bauernfeind prism.

[0050] A classic Bauernfeind prism has angles of 30°, 60°, and 90°. The smallest of the three angles (or the smaller of the two acute angles) corresponds to the wedge angle α. The wedge angle α of a classic Bauernfeind prism is therefore 30°. A modified Bauernfeind prism also has two acute angles. The wedge angle α of a modified Bauernfeind prism can therefore also be understood as the smallest acute angle. This definition is consistent with the above description of the beam paths for the laser radiation, the observation beam path, and the wedge angle α.

[0051] According to an additional or alternative development of the scanning objective, the beam splitter has a refractive index of at least 1.6, preferably at least 1.75. The beam splitter thus comprises a prism material with a refractive index of at least 1.6 or at least 1.75. Within a beam splitter with a high refractive index, divergent beam bundles fan out less than within a beam splitter with a low refractive index. The claimed refractive indices can advantageously further reduce the installation space required for the beam splitter.

[0052] The claimed refractive indices are particularly advantageous when using a Bauernfeind prism as a beam splitter. This allows total internal reflection (TIR) ​​to be ensured for a modified Bauernfeind prism even at small wedge angles (less than 30°, preferably a maximum of 27° or 25°).

[0053] In an additional or alternative development of the scanning lens, it features a compensation wedge in addition to the beam splitter. The compensation wedge comprises a prism material that preferably corresponds to the prism material of the beam splitter.

[0054] The compensation wedge compensates for dispersion and optical path length, ensuring (essentially) the same dispersion and optical path length for all locations within the processing volume. This prevents image aberrations (especially chromatic aberrations) in the processing volume for the laser beam.

[0055] If the prism materials of the beam splitter and the compensation wedge are not identical, the refractive indices and the Abbe numbers of the beam splitter and the compensation wedge are preferably (essentially) identical, at least for the center wavelength (and a spectral width) of the laser radiation.

[0056] The compensation wedge is advantageously located directly adjacent to the beam splitter in the beam path. The compensation wedge and beam splitter are preferably arranged so that laser radiation incident from the direction of the scanner first passes through the compensation wedge and then strikes the beam splitter. The compensation wedge can be cemented to the beam splitter—preferably on the side of the beam splitter that has the splitter layer.

[0057] Furthermore, the compensation wedge is advantageously arranged along the beam path between the beam splitter and the entrance optics.

[0058] According to an additional or alternative development of the scanning lens with a beam splitter, the beam splitter is arranged within the scanning lens in a half facing the scanner. The entrance optics can also include the beam splitter or consist of the beam splitter itself.

[0059] Typically, a single-stage scanning lens has a first section of optical elements that expand the laser beam; the laser beam is guided divergently there. In a second section of optical elements, the laser beam is guided convergently to focus it. Therefore, the half of the scanning lens facing the scanner is understood to be the part of the scanning lens in which the laser beam is guided divergently.

[0060] Preferably, the beam splitter is arranged so that only the compensation wedge is located between the beam splitter and the entrance optics. In other words, along a beam path for the laser radiation, the compensation wedge and the beam splitter are directly adjacent to the entrance optics. There are no other optical elements between the beam splitter and the compensation wedge, nor between the compensation wedge and the entrance optics in the beam path.

[0061] Particularly preferably, the entrance optics are designed as a negative lens - in particular as a negative lens made of a high-refractive material.

[0062] Furthermore, the beam splitter preferably additionally or alternatively has a refractive index of at least 1.6 (or at least 1.75); preferably, the beam splitter is designed as a (modified) Bauernfeind prism. When using a compensation wedge, this also has the aforementioned refractive indices.

[0063] The above-mentioned preferred embodiments with regard to entrance optics and refractive indices produce a beam path that particularly efficiently increases the transmission length of the scanning lens, so that the use of a beam splitter (in particular a Bauernfeind prism) in the half of the scanning lens facing the scanner is particularly well enabled.

[0064] The arrangement of the beam splitter in the half facing the scanner is advantageous because it allows the further beam path (from the beam splitter) to be positioned at a distance from the processing volume for observation. The limited space above the eye (including the surrounding nose and forehead) can thus be used particularly efficiently. Furthermore, the number of optical elements can be reduced if the beam path for the laser radiation and the observation beam path run together for a particularly long time.

[0065] According to an additional or alternative development of the scanning lens with beam splitter, the scanning lens is designed for the center wavelength of the laser radiation and for a center wavelength of an observation radiation. The center wavelength of the laser radiation and the center wavelength of the observation radiation differ from each other by less than a factor of two.

[0066] A "design" of the scanning lens for the center wavelengths means that the transmission of the scanning lens is particularly high for these wavelengths. Anti-reflective coatings are typically optimized to prevent losses at the interfaces of the optical elements. In addition, the "design" means that the separation of laser radiation and observation radiation in the beam splitter is particularly efficient. If, for example, a splitter prism such as a Bauernfeind prism is used as the beam splitter, the splitter layer is typically designed so that the transmission for the laser radiation is greater than 95%, preferably greater than 97%; at the same time, the splitter layer is designed so that the reflection for the observation light is greater than 97%, preferably greater than 98%.

[0067] As shown above, the power assigned to the diffractive structure of the DOE is wavelength-dependent. By maximizing the center wavelength deviation, it is advantageous to ensure that the assigned powers differ by less than a factor of two. This simplifies the design of the part of the observation optics that is not part of the scanning lens.

[0068] In a further development, the center wavelength of the observation radiation is between 780 nm and 900 nm and the center wavelength of the laser radiation is between 1000 nm and 1100 nm. A beam splitter can then have a dichroic layer for beam splitting, which has an edge at about 950 nm.

[0069] In one embodiment of the scanning objective, the exit optics are designed as a contact element. A contact element is also referred to as a contact glass. One side of the contact element is designed to come into (physical) contact with the material to be processed (e.g., the cornea of ​​an eye). For this purpose, the surface of the contact element facing the processing volume can have a curvature that is preferably adapted to the geometry of the object to be processed; e.g., the contact glass can have a curvature with a radius between 5 mm and 30 mm (preferably between 15 mm and 25 mm), and thus be similar to the curvature of the front surface of the cornea of ​​a human eye.

[0070] The contact element can also be designed to fix the eye - for example by suction.

[0071] The scanning lens is preferably also designed such that the contact element has a detachable connection to the rest of the scanning lens. This allows a new (sterile) contact lens to be used for each laser therapy treatment, while the rest of the scanning lens remains unchanged.

[0072] According to a further embodiment of the scanning lens, it is designed to provide a numerical aperture between 0.2 and 0.6 in the processing volume. These numerical apertures allow for the creation of a small focus in the processing volume, enabling an optical breakthrough.

[0073] Additionally or alternatively, the scanning objective is designed to provide a processing volume with a diameter of at least 6 mm and / or up to 15 mm. These diameters allow for the delineation of lenticules in the cornea of ​​an eye, which are particularly advantageous for refractive correction through corneal modification.

[0074] Additionally or alternatively, the scanning lens is designed to guide laser radiation incident from the scanner with a beam diameter of at least 10 mm and / or a maximum of 20 mm to the processing volume. The beam is guided in such a way that at least 80% of the incident laser radiation is geometrically guided through the scanning lens, preferably at least 90%; particularly preferably, the beam is guided without any trimming.

[0075] Additionally or alternatively, the scanning lens is designed for a center wavelength of the laser radiation between 350 nm and 1500 nm, preferably between 750 nm and 1100 nm or between 1000 nm and 1100 nm.

[0076] In summary, the scanning lens according to the invention requires fewer than ten (refractive) lenses compared to the prior art with two-stage scanning optics. A scanning lens according to the embodiments described above can be realized with only five to eight (refractive) lenses (whereby one lens can be designed as a contact element) and has a (preferably single) diffractive optical element and optionally a beam splitter, which is preferably designed as a (modified) Bauernfeind prism. Due to its low refractive power, the DOE can be easily manufactured and adjusted in the scanning lens.

[0077] A second aspect of the invention relates to an ophthalmic laser therapy device. According to the invention, the ophthalmic laser therapy device has a scanning lens according to one of the embodiments described above. Additionally, the laser therapy device comprises a laser device for providing the laser radiation. The laser device is preferably a device that provides laser pulses with a pulse duration of femtoseconds or picoseconds, and whose focused laser beam is capable of severing the tissue of a patient's eye by means of optical breakdown due to nonlinear absorption. For this purpose, the laser device can comprise or consist of, for example, a femtosecond laser or a picosecond laser. Additionally or alternatively, the laser device can be designed to ablate tissue of a patient's eye; for this purpose, the laser device can have an additional laser source.

[0078] A femtosecond laser, for example, has a wavelength in a range from 750 nm to 1100 nm. However, the use of femtosecond lasers at other wavelengths is also conceivable in principle. The pulse duration of a femtosecond or picosecond laser that can be used here can be selected from a pulse duration range of 50 fs to 5 ps. The pulse energy of a femtosecond or picosecond laser that can be used here is advantageously in a pulse energy range of 20 nJ to 20 µJ. Typically, a laser device can provide laser pulses with a laser pulse frequency of up to 50 MHz. However, the laser device can be configured to reduce the laser pulse frequency.

[0079] The laser therapy device further comprises a scanning device with at least one scanner for shifting the focus of the laser radiation within the treatment volume. The scanning device of the ophthalmic laser therapy device is designed to shift or scan the focus of the laser radiation within the treatment volume (e.g., in the cornea of ​​an eye). Scanning of the pulsed laser beam should be possible without restriction in all three spatial directions x, y, and z. Accordingly, the scanning device should be designed to perform both lateral scans in the x and y directions as well as z scans along the optical axis of the laser radiation.

[0080] The ophthalmic laser therapy device can further comprise a control unit for controlling the ophthalmic laser therapy device. The control unit is connected to the laser device and the scanning device for controlling them. For this purpose, the control unit can forward signal data to the corresponding devices. The control unit can typically access all controllable devices of the ophthalmic laser therapy device. It can be constructed in one or more parts and can communicate with the controllable devices of the ophthalmic laser therapy device via wired or wireless communication channels.

[0081] According to an advantageous embodiment of the ophthalmic laser therapy device, it is characterized in that the at least one scanner is arranged at or near a focal point of the scanning lens. The focal point is understood to be the imaginary intersection point of parallel light incident into the exit optics. The scanner is "near" the focal point if, for a centered position of the scanner, it is less than 60% of the focal length from the focal point, preferably less than 50%, particularly preferably a maximum of 40%.

[0082] If the scanner is located at or near the focal point of the scanning lens, telecentric light incidence can be ensured within the processing volume. This is advantageous for enabling optical breakthroughs across the entire processing volume with the same laser power.

[0083] A third aspect of the invention relates to the use of a scanning lens. According to the invention, a scanning lens according to one of the above-described embodiments is used for the laser-based treatment of a visual impairment. Preferably, the scanning lens is used in an ophthalmic laser therapy device according to one of the above-mentioned embodiments.

[0084] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

[0085] The invention is explained in more detail below by way of example with reference to the accompanying drawings, which also disclose essential features of the invention. They show: - Fig. 1 is a diagram of an embodiment of an ophthalmic laser therapy device according to the invention; - Fig. 2 shows a lens section for a first embodiment of a scanning lens; - Fig. 3 a lens section for the first embodiment of a scanning lens with co-observation device; - Fig. 4 shows a lens section for a second embodiment of a scanning lens; - Fig. 5 shows a lens section for a third embodiment of a scanning lens; - Fig. 6 a lens section for a fourth embodiment of a scanning lens.

[0086] In Fig. Figure 1 schematically illustrates an embodiment of an ophthalmic laser therapy device 1. A laser device 20 emits laser radiation 90. The laser radiation 90 is deflected laterally by a scanning device 30. In addition, the ophthalmic laser therapy device 1 also has a further scanning device (not shown) for axial deflection. The scanning lens 10 focuses the laser radiation 90 at a focus 95 in the cornea 85 of an eye. Fig. 1, the focus 95 is shown for two positions in the cornea 85 for different settings of the lateral scanning device 30 and the axial (further) scanning device. The scanning devices allow the focus 95 of the laser radiation 90 to be adjusted within a processing volume 80, which is Fig. 1 is delineated by a dotted line. Any advantageous fixation of the eye by means of a contact element relative to the ophthalmic laser therapy device 1 is not shown.

[0087] During operation, the control of the laser device 20 and the scanning devices 30 is fully automatic via signal data that is transmitted from the control unit 40 to the respective devices 20 and 30. This is indicated by arrows that point from the control unit 40 to the devices 20 and 30, respectively. The control unit 40 ensures suitably synchronous operation of the laser device 20 and the three-dimensional scanning devices. The transmission of the signal data can be via signal data lines or wirelessly. The signal data required during operation is determined in the control unit 40 on the basis of the control data. The control data can be received in advance by the control unit 40 from a planning unit (not shown) as a control data set via unspecified communication channels, such as a control line. The transmission of the control data can also be carried out using memory chips (e.g., via USB or memory stick), magnetic storage devices (e.g.,floppy disks), wirelessly via radio (e.g., WLAN, UMTS, Bluetooth), or wired (e.g., USB, Firewire, RS232, CAN bus, Ethernet, etc.). As an alternative to direct communication, it is also possible to arrange the planning device spatially separate from the control unit 40 and to provide a corresponding data transmission channel. The transmission preferably takes place before the operation of the ophthalmic laser therapy device 1, i.e., before signal data is transmitted to the laser device 20 and the scanning device 30.

[0088] In Fig. 2 shows a lens section for a first embodiment of a scanning lens 100. The task of the scanning lens 100 is to focus the laser radiation 190 incident from the direction of a scanner 170 in a focus 195 in the processing volume 180 (as also in Fig. 1 (delineated by a dotted line). In the example shown, the processing volume 180 is located in the cornea 185 of an eye whose refraction is to be corrected. In this embodiment, the scanning lens 100 is optimized for the use of laser radiation 190 with a center wavelength in the near infrared (NIR; between 1000 nm and 1100 nm).

[0089] The laser radiation 190 incident on the scanning lens 100 from the direction of the scanner 170 first strikes an entrance optic 110, then passes through two prisms 145 and 140, is then refracted by two further lenses, and then passes through a diffractive optical element 130. From there, the laser radiation 190 strikes a partial optic 160 of the scanning lens 100 and finally passes through an exit optic 120.

[0090] The beam path of the laser beam 190 is shown for three tilt positions of the scanner 170. For a center position of the scanner 170 (shown as a solid line), the beam path is shown by solid (solid) lines - one line each for two edge beams and one line for a center beam. The scanner 170 is shown as a dashed line for a first deflection. The corresponding edge beams and the center beam are also shown as dashed lines. For this scanner position, a focus 195 results on the Fig. 2 shown right side of the processing volume 180. For a second deflection, the scanner 170 is shown as a dotted line. The corresponding edge rays and the center beam are also shown as dotted lines. For this scanner position, a focus 195 results on the Fig. 2 shown left side of the processing volume 180.

[0091] In this first embodiment, the entrance optics 110 is designed as a negative lens. In this way, the beam path is widened immediately after entering the scanning lens 100, creating additional space for optical elements for the required optical corrections. The entrance optics 110 is formed from a high-refractive-index lens material. This has the advantage that the curvature of the lens can be smaller for the same refractive power than when using a low-refractive-index lens material. This allows the entrance optics to remain smaller and create additional space. The surface of the entrance optics 110 facing the scanner is aspherically shaped. It is the only aspherical surface in the scanning lens 100 according to this first embodiment.Since state-of-the-art solutions typically comprise multiple lenses with aspherical surfaces, the manufacturing effort (and thus the costs) can be reduced in the embodiment shown here.

[0092] In this first embodiment, the exit optics 120 is formed as a contact element 125. The surface of the contact element 125 facing the processing volume 180 has a curvature with a radius similar to a typical radius of curvature of the anterior cornea of ​​a human eye. In this embodiment, the contact element 125 is made of a low-refractive lens material; however, the use of a high-refractive lens material is also possible.

[0093] From the perspective of the processing volume 180, the exit optics 120 is directly adjoined by the partial optics 160, which is formed as a cemented group of two lenses. The partial optics 160 is thus positioned upstream of the exit optics 120. A spherical (low-refractive index) converging lens of the partial optics 160 faces the exit optics 120; the converging lens of the partial optics 160 is cemented to a high-refractive index, spherical meniscus lens. The partial optics 160 as a whole has a negative refractive power. Similar to the entrance optics 110, which is designed as a negative lens, the negative refractive power of the partial optics 160, which is positioned upstream of the exit optics 120, creates installation space for additional optical elements.

[0094] From the perspective of the processing volume 180, the diffractive optical element 130 adjoins the partial optics 160. This is the only diffractive optical element in the scanning objective 100 according to the first embodiment. The position of the diffractive optical element 130 in the beam path is selected such that only minimal beam deflection is required. The diffractive optical element 130 has a diffractive structure with a refractive power of approximately 1.3 dpt (corresponding to a large focal length f' of 750 mm). With a free diameter of D = 42 mm and a center wavelength of λ = 1050 nm, this is achieved by a maximum groove density v of less than 27 grooves per mm. The DOE 130 thus has a low maximum groove density compared to the prior art, which simplifies manufacturing and positioning.At the same time, the diffractive optical element 130, due to its dispersion, allows a chromatic correction to be made, which is caused in particular by the high proportion of high-refractive lens materials.

[0095] From the direction of the scanner 170, a compensation wedge 145 and a prism are connected to the entrance optics 110. Both are made of a high-refractive (identical) prism material. The prism can be shaped as a Bauernfeind prism and serve as a beam splitter. This is described in Fig. 3. If beam splitting is not required, the compensation wedge 145 and the prism can be replaced with a plane-parallel element (made of the same prism material). The compensation wedge 145 and the prism can also be omitted; for this, the distance between the input optics 110 and the subsequent lens must be adjusted (as well as the chromatic correction).

[0096] Two spherical (high-refractive index) converging lenses are arranged in the beam path between the prism and the diffractive optical element 130.

[0097] The scanning lens 100 according to the first embodiment thus consists (with respect to the optical elements) of a single DOE 130, two prisms with high-refractive index prism material, a low-refractive index exit lens 120 (contact element 125), a high-refractive index entrance lens 110, and three high-refractive index lenses and one low-refractive index lens (in two individual lenses and a cemented group of two lenses). Thus, four of the six lenses of the scanning lens 100 have a high-refractive index lens material.

[0098] It is understood that in the Fig. In the embodiment shown in Figure 2, as well as in all subsequent representations of lens sections, the optical elements are shown only up to their free diameters—i.e., in a radial extent corresponding to their optically effective surfaces. Of course, the actual elements can extend beyond this extent, for example, to be mounted.

[0099] This here in Fig. The embodiment shown in Figure 2, despite its compact design as a single-stage scanning lens 100 (without intermediate image), allows a good correction of image aberrations (in particular chromatic aberrations), in order to enable 180 optical breakthroughs and thus high-quality cuts in a human cornea in the entire processing volume.

[0100] In Fig. Figure 3 shows a lens section for the first embodiment of a scanning lens 100, which additionally has a co-observation device. Entrance optics 110, compensation wedge 145, the two high-refractive index converging lenses, the diffractive optical element 130, as well as the partial optics 160 and the exit optics 120 formed as a contact element 125 are connected to the Fig. 2. Only the prism is designed as a modified Bauernfeind-Prima 140 for beam splitting. The wedge angle α is 25°.

[0101] The observation beam path is shown hatched for three beams of observation radiation 152. The observation beam path extends from the processing volume 180 through the exit optics 120 and the partial optics 160, as well as the DOE 130 and the two high-refractive index converging lenses, to enter the beam splitter 140 on one side 142. The beam path then impinges on a second side within the modified Bauernfeind prism 140, which has a splitter layer 144. The splitter layer 144 is designed as a dichroic layer; wavelengths up to approximately 950 nm are reflected, while longer wavelengths are transmitted. In this way, the laser radiation, which in the present embodiment has a center wavelength between 1000 nm and 1100 nm, can pass through the splitter layer.Since the observation is to take place at wavelengths between 780 nm and 900 nm, the light of the observation radiation 152 is thus reflected at the splitter layer 144; this is where the beam is split between the beam path for the laser radiation and the beam path for observation (also called “co-observation”) of the processing volume. It then strikes the already irradiated side 142 of the modified Bauernfeind prism 140. Due to the selected wedge angle α and the simultaneous use of a highly refractive prism material of the beam splitter 140, total internal reflection occurs on this side 142. The observation beam path is thus guided further within the Bauernfeind prism 140, finally exiting at the side opposite the wedge angle α. The side of the modified Bauernfeind prism 140 opposite the wedge angle α is different from the illustration in . Fig. 2 tilted. This serves to avoid image errors in the observation beam path.

[0102] Typically, an aperture (not shown) is arranged along the observation beam path (now no longer part of the scanning lens 100), followed by a co-observation optics 150, which ultimately reach a sensor 155. The co-observation optics 150 are designed to sharply image a focal plane of the laser radiation 190 onto the sensor 155. The signal from the sensor 155 can be read out, optionally further processed in a computing unit (with a working memory), and finally displayed as an image on a display device (not shown), such as a monitor. The data from the sensor 155 can also be stored in a memory unit. Alternatively, the observation beam path could also have an eyepiece for direct observation in addition to or as an alternative to the sensor 155.

[0103] Co-observation in the visual spectral range is also possible. However, the design of the splitter layer 144, the DOE 130, and the co-observation optics 150 is simplified (as shown in the exemplary embodiment) if the center wavelengths of the laser radiation 190 and the observation radiation 152 differ by less than a factor of 2.

[0104] Based on Fig. 3 shows that, despite a single-stage design of the scanning lens 100, co-observation can be realized by using high-refractive materials and a modified Bauernfeind prism 140.

[0105] In Fig. 4 shows a lens section for a second embodiment of a scanning lens 100. Here too (as in Fig. 2) the incident laser radiation 190 on the scanner 170 as well as three beam bundles for three tilt positions of the scanner 170 are shown (each with two edge beams and one center beam; for the three tilt positions as solid, dashed, or dotted lines). Comparable components are identified by reference numerals as in Fig. 2 marked.

[0106] Like the first embodiment, this second embodiment is also designed for laser radiation 190 with a center wavelength between 1000 nm and 1100 nm. The laser radiation 190 incident on the scanning lens 100 from the direction of the scanner 170 initially strikes an entrance optic 110; this is designed as a negative lens in the form of a meniscus lens with a high-refractive index lens material. A compensation wedge 145 and another prism, which can be designed as a modified Bauernfeind prism 140, follow along the beam path. Both prisms are made of high-refractive index prism material. The wedge angle α (not shown) of the modified Bauernfeind prism 140 is 25°. The modified Bauernfeind prism 140 is suitable for beam splitting between the laser radiation 190 and an observation beam path (not shown). The beam splitting is analogous to the splitting as in Fig. 3, with a splitter layer on one side of the Bauernfeind prism 140 and with another side that deflects the observation beam path via total internal reflection. If an observation is to be carried out, the side of the modified Bauernfeind prism 140 opposite the wedge angle α is preferably Fig. 4 tilted to avoid image errors in the observation beam path.

[0107] Along the beam path for the laser radiation 190, the modified Bauernfeind prism 140 is followed by two positive lenses made of high-refractive-index lens material. The lens facing the Bauernfeind prism 140 has an aspherical surface on the side facing the Bauernfeind prism 140. The scanning lens 100 according to this second embodiment does not have any further aspherical surface.

[0108] A diffractive optical element 130 adjoins the two positive lenses along the beam path for the laser radiation 190. This is the only diffractive optical element 130 in the scanning objective 100 according to the second embodiment. The position of the diffractive optical element 130 in the beam path is selected such that only minimal beam deflection is required. The diffractive optical element 130 has a diffractive structure with a refractive power of approximately 2.3 dpt (corresponding to a focal length f' of 440 mm). With a free diameter of D = 30 mm and a center wavelength of λ = 1050 nm, this is achieved by a maximum groove density v of less than 33 grooves per mm. The DOE 130 thus has a low maximum groove density compared to the prior art, which simplifies manufacturing and positioning.At the same time, the diffractive optical element 130, due to its dispersion, allows a chromatic correction to be made, which is caused in particular by the high proportion of high-refractive lens materials.

[0109] Along the beam path for the laser radiation 190, the diffractive optical element 130 is followed by a negative lens (shaped as a meniscus lens) made of high-refractive lens material, a positive lens (also made of high-refractive lens material) and an exit optic 120, which is shaped as a contact element 125.

[0110] The scanning lens 100 according to the second embodiment thus consists (with respect to the optical elements) of a single DOE 130, two prisms (compensation wedge 145 and modified Bauernfein prism 140) with a high-refractive prism material, a (low-refractive) exit optic 120 (contact element 125), a high-refractive entrance optic 110, and four high-refractive lenses. Thus, five of the six lenses of the scanning lens 100 have a high-refractive lens material.

[0111] This here in Fig. The second embodiment shown in Figure 4 also allows, despite its compact design as a single-stage scanning lens 100, a good correction of image aberrations (in particular chromatic aberrations), in order to enable 180 optical breakthroughs and thus high-quality cuts in a human cornea in the entire processing volume.

[0112] In Fig. 5 shows a lens section for a third embodiment of a scanning lens 100. Here too (as in Fig. 2 and Fig. 4) the incident laser radiation 190 onto the scanner 170 as well as three beam bundles for three tilt positions are shown (each with two edge beams and one center beam; for the three tilt positions as solid, dashed, or dotted lines). Comparable components are also identified here with reference numerals as in Fig. 2 and Fig. 4 marked.

[0113] In contrast to the first two embodiments, this third embodiment is designed for laser radiation 190 with a center wavelength between 350 nm and 420 nm. The laser radiation 190 incident on the scanning lens 100 from the direction of the scanner 170 initially strikes an entrance optic 110; this is designed as a negative lens with a high-refractive index lens material. The side facing away from the scanner 170 has an aspherical surface. The scanning lens 100 according to this third embodiment does not have any further aspherical surface.

[0114] A compensation wedge 145 and another prism, which can be designed as a modified Bauernfeind prism 140, follow along the beam path. Both prisms are made of high-refractive prism material. The wedge angle α of the modified Bauernfeind prism 140 is 25°. The modified Bauernfeind prism 140 is suitable for beam splitting between the laser beam 190 and an observation beam path (not shown). The beam splitting is analogous to the splitting as described in Fig. 3, with a splitter layer on one side of the Bauernfeind prism 140 and with another side that deflects the observation beam path via total internal reflection. If an observation is to be carried out, the side of the modified Bauernfeind prism 140 opposite the wedge angle α is preferably Fig. 5 tilted to avoid image errors in the observation beam path.

[0115] Along the beam path for the laser radiation 190, the modified Bauernfeind prism 140 is followed by a positive lens made of high-refractive-index lens material. This is followed by a diffractive optical element 130. This is the only diffractive optical element 130 in the scanning objective 100 according to the third embodiment. The position of the diffractive optical element 130 in the beam path is also selected here such that only minimal beam deflection is required. The diffractive optical element 130 has a diffractive structure with a refractive power of just under 5 dpt (corresponding to a focal length f' of just over 200 mm). With a free diameter of D = 46 mm and a center wavelength of λ = 400 nm, this is achieved by a maximum groove density v of less than 290 grooves per mm.The DOE 130 thus exhibits a low maximum groove density for a diffractive structure designed for the aforementioned short center wavelength, simplifying manufacturing and positioning. At the same time, the diffractive optical element 130's dispersion allows for chromatic correction, which is caused by the high proportion of high-index lens materials.

[0116] Along the beam path for the laser radiation 190, the diffractive optical element 130 is followed by a partial optics 160, which, as a kit group, consists of a high-refractive meniscus lens and a low-refractive positive lens. The cemented surface between the two lenses is diverging. Finally, along the beam path, an exit optics 120, shaped as a contact element 125, follows.

[0117] The scanning lens 100 according to the third embodiment thus consists (with respect to the optical elements) of a single DOE 130, two prisms (compensation wedge 145 and modified Bauernfein prism 140) with a high-refractive prism material, a (low-refractive) exit optic 120 (contact element 125), a high-refractive entrance optic 110, and two high-refractive lenses and one low-refractive lens. Thus, three of the five lenses of the scanning lens 100 have a high-refractive lens material.

[0118] This here in Fig. The third embodiment shown in Figure 5 also allows, despite its compact design and the small number of optical elements as a single-stage scanning lens 100, a good correction of image aberrations (in particular chromatic aberrations), in order to enable 180 optical breakthroughs and thus high-quality cuts in a human cornea in the entire processing volume.

[0119] In Fig. 6 shows a lens section for a fourth embodiment of a scanning lens 100. Here, too (as in the embodiments described above), the incident laser radiation 190 on the scanner 170 as well as three beam bundles for three tilt positions of the scanner 170 are shown (each with two edge beams and one center beam; for the three tilt positions as solid, dashed, or dotted lines). Comparable components are designated by reference numerals as in Fig. 2, Fig. 4 and Fig. 5 marked.

[0120] Like the first and second embodiments, this fourth embodiment is also designed for laser radiation 190 with a center wavelength between 1100 nm and 1300 nm. The scanning lens 100 shown here according to the fourth embodiment has no aspherical surfaces; rather, all surfaces of the optical elements are spherical (or flat). The laser radiation 190 incident on the scanning lens 100 from the direction of the scanner 170 initially strikes an entrance optic 110; this is designed as a negative lens with a high-refractive index lens material. A compensation wedge 145 and another prism, which can be designed as a modified Bauernfeind prism 140, follow along the beam path. Both prisms are made of high-refractive index prism material. The wedge angle α of the modified Bauernfeind prism 140 is 25°.The modified Bauernfeind prism 140 is suitable for splitting the beam between the laser beam 190 and an observation beam path (not shown). The beam splitting is performed analogously to the splitting described in . Fig. 3, with a splitter layer on one side of the Bauernfeind prism 140 and with another side that deflects the observation beam path via total internal reflection. If an observation is to be carried out, the side of the modified Bauernfeind prism 140 opposite the wedge angle α is preferably Fig. 6 tilted to avoid image errors in the observation beam path.

[0121] Along the beam path for the laser radiation 190, the modified Bauernfeind prism 140 is followed by three positive lenses made of high-refractive-index lens material. The positive lenses, in turn, are followed by a partial optics 160, which consists of a cemented group with a low-refractive-index positive lens (converging lens), a high-refractive-index negative lens, and a second low-refractive-index positive lens. The positive lens of the partial optics 160 facing away from the scanner 170 has a diffractive optical element 130 on the side facing away from the scanner 170. This element is located on the concave surface of the positive lens. The position of the diffractive optical element 130 in the beam path is also selected so that only minimal beam deflection is required. The diffractive optical element 130 has a diffractive structure to which a refractive power of approximately 6.5 dpt can be assigned (corresponding to a focal length f' of 155 mm).With a free diameter of D = 13 mm and a center wavelength of λ = 1200 nm, this is achieved by a maximum groove density v of less than 35 grooves per mm. The DOE 130 thus has a low maximum groove density compared to the state of the art, simplifying manufacturing and positioning. At the same time, the diffractive optical element 130, due to its dispersion, allows for chromatic correction, which is particularly caused by the high proportion of high-index lens materials. Finally, an exit optic 120, shaped as a contact element 125, follows along the beam path.

[0122] The scanning lens 100 according to the fourth embodiment thus consists (with respect to the optical elements) of a single DOE 130, two prisms (compensation wedge 145 and modified Bauernfein prism 140) with high-refractive prism material, a (low-refractive) exit optic 120 (contact element 125), a high-refractive entrance optic 110, and five high-refractive and two low-refractive lenses. Thus, five of the eight lenses of the scanning lens 100 have a high-refractive lens material.

[0123] This here in Fig. The fourth embodiment shown in Figure 6 also allows, despite its compact design and with the exclusive use of spherical lenses as a single-stage scanning lens 100, a good correction of image aberrations (in particular chromatic aberrations), in order to enable 180 optical breakthroughs and thus high-quality cuts in a human cornea in the entire processing volume.

[0124] The features of the invention mentioned above and described in various embodiments can be used not only in the specified exemplary combinations, but also in other combinations or alone, without departing from the scope of the present invention. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 8702770 B2

[0014] DE 10 2004 009 212 B4

[0014]

Claims

[1] Single-stage scanning lens (10, 100) for use in an ophthalmological laser therapy device (1) with a scanner (170), for guiding laser radiation (90, 190) from the scanner (170) into a focus (95, 195) in a processing volume (80, 180), comprising • an entrance optics (110) facing the scanner (170), • an exit optic (120) facing the processing volume (80, 180), and • one or more diffractive optical elements (130), wherein the one or more diffractive optical elements (130) each have a diffractive structure, wherein a refractive power associated with the diffractive structure is a maximum of 10 dpt, preferably a maximum of 7 dpt, particularly preferably a maximum of 5 dpt or 3 dpt. [2] Scanning lens (10, 100) according to claim 1, characterized by that all diffractive optical elements (130) are arranged between the entrance optics (110) and the exit optics (120). [3] Scanning lens (10, 100) according to claim 1 or 2, characterized by that at least one of the diffractive optical elements (130) is arranged in a half of the scanning objective (10,100) facing the processing volume (80, 180). [4] Scanning lens (10, 100) according to one of claims 1 to 3, characterized by that the scanning lens (10, 100) has exactly one diffractive optical element (130). [5] Scanning lens (10, 100) according to one of claims 1 to 4, characterized by that a proportion of high-refractive lens materials is at least 50%, preferably at least 60%, wherein a high-refractive lens material has a refractive index of at least 1.75, preferably at least 1.8 or 1.

9. [6] Scanning lens (10, 100) according to one of claims 1 to 5, characterized by , that • the entrance optics (110) is a negative lens made of a high-refractive material, wherein a high-refractive lens material has a refractive index of at least 1.75, preferably at least 1.8 or 1.9, and / or • a partial optic (160) immediately upstream of the exit optic (120) has a cement group with negative refractive power, wherein a lens of the cement group facing the processing volume (80, 180) is a positive lens made of a low-refractive lens material, wherein a low-refractive lens material has a refractive index of maximum 1.65, preferably maximum 1.

55. [7] Scanning lens (10, 100) according to one of claims 1 to 6, characterized by that a refractive surface of the scanning lens (10, 100) is aspherically shaped, wherein preferably the scanning lens (10, 100) has only a single aspherically shaped, refractive surface, and / or preferably the surface of the entrance optics (110) facing the scanner (170) is aspherically shaped. [8] Scanning lens (10, 100) according to one of claims 1 to 7, further comprising a beam splitter (140). [9] Scanning lens (10, 100) according to claim 8, characterized by that the beam splitter (140) is designed as a Bauernfeind prism, which preferably has a wedge angle α of less than 30°, particularly preferably a maximum of 27° or a maximum of 25°. [10] Scanning lens (10, 100) according to claim 8 or 9, characterized by that the refractive index of the beam splitter (140) is at least 1.6, preferably at least 1.

75. [11] Scanning objective (10, 100) according to one of claims 8 to 10, further comprising a compensation wedge (145) with a prism material which preferably corresponds to a prism material of the beam splitter (140). [12] Scanning lens (10, 100) according to one of claims 8 to 11, characterized bythat the beam splitter (140) is arranged within the scanning objective (10, 100) in a half facing the scanner (170). [13] Scanning lens (10, 100) according to one of claims 8 to 12, characterized by that the scanning objective (10, 100) is designed for a center wavelength of the laser radiation (90, 190) and for a center wavelength of an observation radiation, wherein the center wavelength of the laser radiation (90, 190) and the center wavelength of the observation radiation differ from each other by less than a factor of two. [14] Scanning lens (10, 100) according to one of claims 1 to 13, characterized by that the exit optics (120) is designed as a contact element (125). [15] Scanning lens (10, 100) according to one of claims 1 to 14, characterized by that the scanning lens (10, 100) • provides a numerical aperture between 0.2 and 0.6 in the processing volume (80, 180), and / or • provides a processing volume (80, 180) with a diameter of at least 6 mm and / or up to 15 mm, and / or • is designed to guide laser radiation (90, 190) incident from the scanner (170) with a beam diameter of at least 10 mm and / or a maximum of 20 mm to the processing volume (80, 180), and / or • is designed for a center wavelength of the laser radiation (90, 190) between 350 nm and 1500 nm, preferably between 750 nm and 1100 nm. [16] Ophthalmological laser therapy device (1), comprising - a scanning lens (10, 100) according to one of claims 1 to 15, - a laser device (20) for providing the laser radiation (90, 190), and - a scanning device (30) with at least one scanner (170) for shifting the focus (95, 195) of the laser radiation (90, 190) in the processing volume (80, 180). [17] Ophthalmological laser therapy device (1) according to claim 16, characterized bythat the at least one scanner (170) is arranged in or near a focal point of the scanning lens (10,100). [18] Use of a scanning lens (10, 100) according to one of claims 1 to 15 for laser-based treatment of a visual impairment.

Images