Light-based skin treatment devices

Abstract

A light-based skin treatment device for treating skin by laser-induced optical decomposition of hair or skin tissue. A focusing system has an exit focusing lens for focusing an incident light beam onto a focal spot in the hair or skin tissue. The lens has a central aperture. This helps to reduce retroreflections from the lens surface that could damage the focusing system.

Description

Technical Field

[0001] The present invention relates to a light-based skin treatment device. The device comprises a light source, an optical system and a transparent exit window. The light source is used to provide an incident light beam for treating the skin by laser-induced optical breakdown (LIOB) of hair or skin tissue. The transparent exit window allows the incident light beam to leave the device. The optical system is provided for focusing the incident light beam onto a focal spot in the hair or skin tissue outside the skin treatment device. Background Art

[0002] Such light-based skin treatment devices are used, for example, for wrinkle treatment and hair trimming. In light-based wrinkle treatment, the device forms a focal spot in the dermis of the skin to be treated. The power and pulse duration of the laser and the size of the focal spot are selected so that the laser-induced optical breakdown (LIOB) phenomenon affects the skin, thereby stimulating the regrowth of skin tissue and thereby reducing wrinkles. In light-based hair cutting, the incident light beam is focused inside the hair, and the LIOB phenomenon causes the hair to be cut through.

[0003] For example, the international patent application published as WO 2005 / 011510 describes a device for shortening hair, the device comprising a laser source for generating a laser beam during a predetermined pulse time, an optical system for focusing the laser beam onto a focal spot, and a laser beam manipulator for positioning the focal spot at a target location. The size of the focal spot and the power of the generated laser beam are such that the laser beam has a power density in the focal spot above a characteristic threshold of the hair tissue, above which, for a predetermined pulse time, a laser induced optical breakdown (LIOB) phenomenon occurs in the hair tissue. WO 2008 / 001284 discloses further details and discusses, for example, laser beam requirements and required focusing system characteristics, such as the numerical aperture of the exit lens.

[0004] Usually, when the power density (W / cm 2 ) exceeds a threshold value, which is characteristic for a particular medium. Below the threshold value, the particular medium has relatively low linear absorption characteristics for the particular wavelength of the laser beam. Above the threshold value, the medium has strong nonlinear absorption characteristics for the particular wavelength of the laser beam, which is a result of medium ionization and plasma formation. This LIOB phenomenon can lead to several mechanical effects, such as cavitation and the generation of shock waves, which damage the medium in locations around the location of the LIOB phenomenon.

[0005] LIOB utilizes high intensity sub-nanosecond or (so called picosecond) laser pulses to generate the high photon flux required for multiphoton absorption in the skin. The nonlinear LIOB process occurs in the focal spot volume only when the extremely high photon flux generated in the focal spot by high numerical aperture (NA) focusing exceeds the intensity threshold required for optical breakdown.

[0006] LIOB based skin treatment devices use Class 4 lasers which are potentially dangerous to the user. Therefore, it is important to include safety measures to ensure the safety of both the user and the expensive equipment.

[0007] Traditionally, LIOB utilizes basic Gaussian TEM 00 mode, where the transverse profile of the light intensity of the beam is described by a Gaussian function. For a Gaussian beam, the peak intensity, i.e. the intensity at the beam axis, is twice the power divided by the effective mode area (effective mode area = πw 2 , where w is the mode radius). 00 When a Gaussian beam is used to create LIOB, the exit focusing lens is often damaged by back reflections from the skin, especially in the center of the beam, corresponding to the peak intensity.

[0008] A damaged lens can lead to poor treatment efficacy and adverse side effects to the user. In particular, a damaged exit window has a deleterious effect on the device's ability to provide sufficiently tight focus at the desired location, which may reduce the efficacy of the treatment process and / or may increase the occurrence of adverse side effects, such as skin irritation. If superficial lesions form above the dermis, ecchymoses (microbleeds) may occur due to microrupture of capillaries, leading to reduced efficacy, increased side effects, and social downtime.

[0009] Although many active safety systems have been reported in the past, they are sensitive to failure and can be quite complex and therefore expensive.

[0010] Another option is to use a Gaussian to top hat converter to convert the single mode Gaussian laser beam profile to a flat top laser beam profile.

[0011] There remains a need for a simpler, passive, and robust system to further improve device and user safety compared to Gaussian intensity and top-hat intensity profiles. Summary of the invention

[0012] The invention is defined by the claims.

[0013] According to an example of the first aspect of the present invention, there is provided a light-based skin treatment device comprising:

[0014] a laser light source for providing a pulsed incident light beam for treating the skin by laser-induced optical disintegration of hair or skin tissue; and

[0015] a focusing system for focusing the incident light beam into a focal spot in the hair or skin tissue,

[0016] Therein, the focusing system comprises an exit focusing lens having a central evacuated or gas-filled orifice.

[0017] The aperture in the exit lens creates a ring-shaped focused beam. By distributing the laser energy in a ring rather than a Gaussian beam profile, the peak irradiance of the laser at the skin surface can be reduced. This reduces the intensity at any given point on the skin while maintaining the photon flux in the focal spot volume, which can be achieved using a Gaussian intensity profile. Back-reflected light is reduced due to the peak intensity at the center of the beam. This prevents damage to the contact window or exit lens and potential skin damage, thereby improving the safety and efficacy of LIOB-based skin treatments.

[0018] For the same photon flux in the focal spot area, annular illumination generates a reduced level of light back-reflected from the skin along the axis of the beam where the laser power is minimum, compared to Gaussian illumination with maximum intensity on the axis of the beam.

[0019] The laser light source preferably comprises a 1064 nm laser. This provides low absorption and scattering inside the skin and therefore provides a greater penetration depth.

[0020] The laser light source is for example suitable for delivering pulses with an energy of 1 to 10 mJ and having a pulse duration of 100 fs to 10 ns, for example 100 ps to 10 ns. This provides energy levels suitable for LIOB.

[0021] The exit focusing lens preferably has a high numerical aperture to provide effective tight focusing to the desired point for safe operation of the system.

[0022] The diameter of the orifice is, for example, less than 1 mm, such as less than 0.5 mm.

[0023] The area of ​​the aperture is, for example, less than 5% of the area of ​​the exit focusing lens, or less than 5% of the effective aperture of the exit focusing lens.

[0024] The apparatus may comprise a beam shaping apparatus for generating a ring-shaped pulsed incident beam.

[0025] The beam shaping device may include:

[0026] A spatial light modulator; or

[0027] Phase mask; or

[0028] Blanking mask; or

[0029] Holographic panels; or

[0030] Grating.

[0031] These are the various options for creating the desired ring beam.

[0032] The present invention also provides a light-based skin treatment method, comprising:

[0033] providing a pulsed incident light beam for treating skin by laser-induced optical disintegration of hair or skin tissue;

[0034] The incident beam is focused into a focal spot in the hair or skin tissue by focusing using an exit focusing lens with a central aperture less than 1 mm in diameter.

[0035] The pulsed incident light may be a 1064 nm laser with a pulse having an energy of 1 to 10 mJ and a duration of 100 fs to 10 ns (eg, 100 ps to 10 ns).

[0036] The method may include generating an annular pulsed incident beam.

[0037] These methods are non-therapeutic, particularly cosmetic, methods used for skin rejuvenation or hair removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Examples of the present invention will now be described in detail with reference to the accompanying drawings, in which:

[0039] Figure 1 A known LIOB skin treatment device is schematically shown;

[0040] Figure 2 A known focusing lens is shown in more detail;

[0041] Figure 3 One possible way to implement beam shaping to reduce damage due to back reflections is shown;

[0042] Figure 4 shows in more detail a known focusing lens according to the invention; and

[0043] Figure 5 A laser treatment method is shown. DETAILED DESCRIPTION

[0044] The present invention will be described with reference to the accompanying drawings.

[0045] It should be understood that the detailed description and specific examples, although indicating exemplary embodiments of the device, system and method, are intended only for illustrative purposes and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the device, system and method of the present invention will be better understood based on the following description, the appended claims and the accompanying drawings. It should be understood that the drawings are only schematic and are not drawn to scale. It should also be understood that throughout the drawings, the same reference numerals are used to represent the same or similar parts.

[0046] The present invention provides a light-based skin treatment device for treating skin by laser-induced optical decomposition of hair or skin tissue. A focusing system has an exit focusing lens for focusing an incident light beam onto a focal spot in the hair or skin tissue. The lens has a central aperture. This helps to reduce back reflections from the lens surface that could damage the focusing system.

[0047] Before describing the present invention in detail, one example of the type of apparatus to which the present invention relates will be outlined.

[0048] Figure 1 A system 1 for treating skin 3 having a surface 5 is shown.

[0049] The system 1 comprises a light source 9 for generating a laser beam 11 during at least a predetermined pulse time, and comprises an optical system 13 for focusing the laser beam 11 into a focal spot 15 and positioning the focal spot 15 in a target location within the skin 3, which location is at least partially transparent to light from the light source 9.

[0050] exist Figure 1 Examples of the optical system 13 schematically shown in the figure include a beam deflection and dichroic beam splitting system 17, an aberration correction system 19, a beam scanning system 21 and a focusing system 23, which may include one or more mirrors, prisms, beam splitters, polarizers, optical fibers, lenses, apertures, shutters, etc. For example, the scanning system includes a scanning prism.

[0051] The focusing system has focus depth selection, beam shaping and focusing, and contact / output window. There is a perimeter after the suspension to maintain contact of the contact / output window.

[0052] At least parts of the optical system 13 and / or the optical path of the laser beam 11 may be sealed, for example for eye safety, for example comprising an opaque tube and / or one or more optical fibers.

[0053] The light source 9 is configured to emit a predetermined number of laser pulses at a predetermined wavelength and at a predetermined pulse duration and repetition rate. The system 1 is configurable so that the target position of the focal spot 15 is below the surface of the skin. The size of the focal spot 15 and the power of the generated laser beam are such that in the focal spot 15, the laser beam 11 has a power density that is above a characteristic threshold of the skin tissue, above which, at a predetermined pulse time, a laser-induced photobreakdown event occurs.

[0054] There may be an articulated arm between the laser source 9 and the beam deflection and dichroic beam splitting system 17. The beam deflection system 17 and subsequent components form part of the handpiece. Due to alignment errors in the mirrors of the articulated arm, the beam may be expanded before entering the articulated arm and then compressed before beam steering and aberration correction.

[0055] The skin 3 comprises multiple layers with different optical properties. The epidermis comprises the outermost layer and forms a waterproof protective barrier. The outermost layer of the epidermis is the stratum corneum, which, due to its microscopic roughness fluctuations, hinders the optical coupling between the device 1 and the skin 3. Therefore, preferably a coupling fluid is provided between the focusing system and the skin, the refractive index of the coupling fluid being intended to match the refractive index of the skin and / or the exit lens of the focusing system.

[0056] Beneath the epidermis, there is the dermis. The dermis contains collagen fibers that are targeted by skin treatments.

[0057] In one example use of the system, the purpose of skin treatment is to create a focal spot 15 of the pulsed laser beam 11 in the collagen of the dermis in order to create microscopic lesions that lead to new collagen formation.

[0058] The light source 9 can be controlled by an optional controller 25, which may provide a user interface. Furthermore, one or more parts of the optical system 13 may be controlled by an optional controller (not shown), which may be integrated with the light source controller 25 to control one or more properties of the target position and / or the focal spot.

[0059] The laser beam focusing parameters can be determined by appropriate settings of the beam shaping and / or focusing system, for example by adjusting the numerical aperture of the focusing system. The optical system has a numerical aperture of at least 0.2, preferably at least 0.4, more preferably at least 0.6. Such values ​​of the numerical aperture are relevant to the safety of the upper skin layers, in particular the epidermis.

[0060] Suitable light sources include Q-switched Nd:YAG lasers emitting laser pulses at a wavelength of about 1064 nm with a pulse duration of about 100 ps to 10 ns. In this range, plasma generated by LIOB is very localized, i.e., has a small spatial extension, which minimizes the risk of accidental damage to surrounding tissue. Furthermore, the peak power required to achieve LIOB is essentially independent of the pulse duration within this range. However, other pulse durations may also be used, for example in the range of about 100 fs to 100 ps.

[0061] The pulse energy may be 1 to 10 mJ.

[0062] The exit lens 50 is a high NA focusing lens.

[0063] 1064 nm is preferably used for treatment because absorption and scattering within the skin is relatively low and thus provides a large penetration depth. Other lasers, for example, Nd:Cr:Yag triple lasers and / or diode lasers may also be used. Another example is an Er:YAG laser, having an emission wavelength of 1645 nm.

[0064] The beam deflection and dichroic beam splitting system 17 comprises a dichroic beam splitter which reflects the laser light but passes light of visible wavelengths. Thus, light of visible wavelengths received from the skin 3 is captured by the optical system and provided as a feedback signal 11' which can be used to control the system manually or automatically.

[0065] The depth of focus provided by the focusing system 23 is preferably adjustable.

[0066] Figure 2 A focusing system is shown with a conventional exit focusing lens 30 which provides focused laser pulses into the skin 3, creating a LIOB at the focal spot 15. The intensity profile is shown as curve 32, having a central portion 34 of high intensity and an annular band 36 of low intensity.

[0067] The first directly back-reflected light will come from the exit surface of the focusing lens 30 and if there are multiple layers 30A, 30B, 30C before the skin, such as Figure 2 As shown, each layer will contribute to the retroreflected light. The incident ray and the directly reflected ray are represented by arrows 38. The light rays bent by the focusing function of the lens will not contribute to the directly retroreflected light.

[0068] For example, layers 30A, 30B, 30C are provided to improve optical coupling with the skin and may comprise gels containing a mixture of polar and non-polar substances, transparent foils and oils. The use of such additional layers is explained in more detail in, for example, WO 2013 / 128380.

[0069] As mentioned above, Figure 3 As shown, a Gaussian to top hat converter may be used to convert a single mode Gaussian laser beam profile 40 to a top hat laser beam profile 42 .

[0070] Figure 4 The method of the present invention is shown in which the exit focusing lens 50 is modified to include a central aperture 52. For simplicity, although additional coupling layers may of course be present, Figure 4 Not shown.

[0071] Normally, there will be immersion fluid underneath the entire aperture of the lens 50. This means that the effective aperture of the lens will be smaller than the maximum practical lens aperture.

[0072] For example, the area of ​​the central aperture is only a few percent of the area of ​​the effective aperture (diameter) based on the lens. Typically, the area will be less than 5%, for example in the range of 0.25% to 5%. For example, for an actual lens aperture of 4 mm, the effective aperture may be 3.6 mm (hence an area of ​​10.2 mm). 2 ), and the diameter of the central orifice is, for example, in the range of 0.2-0.4 mm (hence the area is 0.03 mm 2 ) to 0.50mm 2 ).

[0073] The purpose of the aperture is to prevent damage to the lens due to peak intensity in a very small area at the center.

[0074] The orifice is usually filled with air. It is possible for the orifice to fill with immersion fluid between the lens and the skin, but due to the small size of the orifice, less than 1 mm in diameter (more typically less than 0.5 mm), the likelihood of this filling is low.

[0075] Even if the aperture is filled with immersion fluid, in any case the damage of the retroreflection is likely to be limited to the immersion fluid in the gap and is not a problem. This is because the diameter of the central aperture is very small compared to the effective aperture filled.

[0076] Thus, the aperture may be filled with air, or a lens immersion fluid or coupling medium. Preferably, the aperture is filled with a fluid (liquid or gas) having a different refractive index than the lens, so that the fluid does not perform the same focusing function of the lens. The aperture may even be evacuated and then sealed. The aperture may thus be open or may be closed.

[0077] The fluid in the orifice is static. The orifice therefore does not serve as a flow channel but rather as an interruption in the lens function. The orifice is for example filled with a static medium having a refractive index different from that of the lens, for example a medium having a refractive index below 1.3 at the wavelength of the laser.

[0078] The intensity profile is shown as curve 54, with a low intensity central portion 56, a medium intensity ring 58, and a high intensity ring in the middle of the central intensity ring. Of course, this is a generalization, as the intensity distribution is smooth rather than discrete. The high intensity portion transitions from the central circle to an annular ring of larger diameter, thus reducing the peak irradiance but maintaining the total flux.

[0079] This prevents damage to the contact window / exit lens and potential skin injury, thereby improving the safety and effectiveness of LIOB-based skin treatments. This design reduces light reflected back from the skin along the axis of the beam.

[0080] The laser beam pulse can have a circular cross-sectional shape. The use of a circular beam will result in energy loss, but this is very small.

[0081] The laser beam may alternatively be shaped before reaching the exit focusing lens 50 to form a ring-shaped laser beam. Figure 4 The beam shaping device 64 is schematically shown in FIG. In this way, there is no wasted laser energy which does not contribute to the focused beam. The ring beam can be created in many different known ways by employing wavefront control, for example using a spatial light modulator, a phase mask, a barrier mask, a holographic plate or a grating.

[0082] A beam shaping solution will be chosen that minimizes conversion losses, is low cost, and is least sensitive to system tolerances.

[0083] Skin treatment may include a hair removal shaving process. During use, the focusing system 23 is moved over the skin surface to perform shaving. The focusing system forms an exit window for allowing an incident light beam to leave the device. The focusing system then forms an optical blade.

[0084] Skin treatments may include skin rejuvenation for reducing wrinkles that occur in human skin due to the normal aging process. During use, the focusing element is pressed or held against the skin to be treated. The exit window formed by the focusing system is held parallel to the skin, and the incident light beam leaves the exit window and enters the skin in a direction substantially perpendicular to the skin surface.

[0085] In both examples, an immersion fluid may be provided between the focusing system and the skin surface. Preferably, an immersion fluid is used that has a refractive index close to that of the focusing system 23 skin contact lens and the skin or hair where LIOB will occur. For this purpose, fluids having a refractive index of about 1.4 to about 1.5 are suitable. Likewise, although water has a slightly lower refractive index of 1.33, water may also be a suitable immersion fluid for certain devices and applications.

[0086] Figure 1The system has a specific set of optical components between the laser and the focusing system. However, this arrangement is not intended to be limiting. The feedback system of the present invention can be used in different system configurations with fewer or greater numbers of components.

[0087] Figure 5 A light-based skin treatment method is shown, comprising:

[0088] In step 70, a pulsed incident light beam is provided for treating the skin by laser-induced optical decomposition of hair or skin tissue; and

[0089] In step 72, the incident light beam is focused onto a focal spot in the hair or skin tissue by focusing using an exit focusing lens having a central aperture.

[0090] It should be noted that the embodiments mentioned above are examples rather than limitations of the present invention, and that a person skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference numerals placed in brackets shall not be construed as limiting the claims. In the claims, the verb "comprise" and its conjunctions do not exclude the presence of elements or steps other than those stated in the claims. The word "one" or "an" before an element does not exclude the presence of multiple such elements. The present invention may be implemented by means of hardware comprising several different elements, and by means of appropriately programmed computers. In a device-type claim enumerating several devices, several of these devices may be implemented by the same item of hardware. Although specific measures are recorded in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A light-based skin treatment device (1), comprising: a laser light source (9) for providing a pulsed incident light beam (11) for treating the skin (3) by laser-induced optical decomposition of hair or skin tissue; and a focusing system (23) for focusing the incident light beam (11) into a focal spot (15) in the hair or skin tissue, The focusing system comprises an exit focusing lens (50), the incident light beam (11) has a circular cross-sectional shape when reaching the exit focusing lens, and the exit focusing lens has a central aperture (52) with a diameter less than 1 mm, so that the incident light beam (11) with the circular cross-sectional shape is shaped into a ring-shaped focusing beam.

2. The device according to claim 1, wherein: The laser light source includes a 1064nm laser.

3. The device according to claim 1 or 2, wherein: The laser light source is suitable for delivering pulses with an energy of 1 to 10 mJ.

4. The device according to claim 1 or 2, wherein: The laser light source is adapted to deliver pulses having a pulse duration of 100 fs to 10 ns.

5. The device according to claim 1 or 2, wherein: The laser light source is adapted to deliver pulses having a pulse duration of 100 ps to 10 ns.

6. The device according to claim 1 or 2, wherein: The diameter of the orifice is less than 0.5 mm.

7. The device according to claim 1 or 2, wherein: The area of ​​the aperture is less than 5% of the area of ​​the exit focusing lens, or less than 5% of the effective aperture of the exit focusing lens.

8. The device according to claim 1 or 2, wherein: The orifice is filled with a static fluid.

9. The device according to claim 8, wherein: The refractive index of the static fluid is different from the lens refractive index of the exit focusing lens.

10. The device according to claim 1 or 2, wherein: The orifice is evacuated and sealed.

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