IL147009A - Method and apparatus for improving safety during exposure to a monochromatic light source - Google Patents

Description

Ref: 13645/01 147009/2 ηατ]ΐΊ3ΐ ΐπ TI N πρη·7 πΕτωπ mil mrriDnn iww1? wm APPARATUS FOR IMPROVING SAFETY DURING EXPOSURE TO A MONOCHROMATIC LIGHT SOURCE METHOD AND APPARATUS FOR IMPROVING SAFETY DURING EXPOSURE TO A MONOCHROMATIC LIGHT SOURCE Field of the Invention The present invention is related to the field of laser-based light sources. More particularly, the present invention is related to eye-safe and skin-safe laser-based light sources for skin treatment, as a result of esthetic and medical problems associated with such skin, that require very high spectral power density. Even more specifically, the present invention is related to a method and apparatus for transforming a coherent laser beam into a non-coherent monochromatic beam, which can be efficiently utilized for treating skin at a very short distance but is inherently safe to bystanders.

Background of the Invention Current medical and esthetic laser systems are generally considered as high-risk systems due to the low divergence of the light beam that is emitted from these systems. In these systems a light beam with a high power density is generated, which hardly attenuates as the beam propagates through air, or through an air-like medium, to a distant target location whereat it could cause damage to bodily tissue. In the case of a laser source emitting visible, or near visible, light, damage could result by burning a small portion of an eye retina, if the beam is accidentally aimed to someone's eyes. Such beam could even cause blindness.

Therefore, in order to minimize the risk of damaging living tissues, or causing other kind of damages, special, and often, high-cost precautions must be taken. For example, such precautions might include the use of expensive (and inconvenient to use) coated protective eyeglass filters with very high optical density and damage-resistant values to optical radiation (i.e. thermal and mechanical durability). Some of the properties of such filters are included in standard documents such as ANSI Z136.1, which is the basic American National Standard document regarding the safety of laser beams. Other precautions forbid using highly reflective surfaces in a room, where the laser system resides. Special shades and/or curtains are also utilized for preventing an accidental laser beam from escaping the room or facility, thereby protecting people outside the treatment room.

Of all the risks, the risk of permanently blinding people is the most common and severe. The currently most eye-hazardous lasers are those referred to as a pulsed-laser. For example, a Ruby, Nd:YAG, Alexandrite, LICAF, Diodes, Dye lasers, Erbium-Glass, Excimer lasers, etc. are examples of a pulsed-laser. High-class Continuous Working (CW) lasers, such as Nd:YAG, KTP and Diode lasers (at any wavelength between 630 and 1320 nm) are also known for their risk in causing blindness. Moreover, these lasers are at times used for cosmetic surgery in the vicinity of the eyes, such as for eyebrow removal or skin rejuvenation around the eyes, and therefore such surgery causes additional risk to eye damage. Other infrared lasers (pulsed and CW), such as CO2 and Erbium, are also capable of causing severe eye damage from a distance by burning the cornea due to the strong absorption of laser beams emitted from such laser sources in the aqueous humor of the eyeball.

There is also a risk of hair and skin burns, if the laser units are mishandled, even if operated in remote locations. Should a collimated laser beam hit a flammable material in the treatment room, a fire may result.

The risks associated with coherent lasers do not stem only from the capability to generate highly collimated beams, but also from the capability to concentrate the entire laser energy onto a confined surface from a distance, with the appropriate focusing optics.

Due to the extremely high thermodynamic temperature of lasers as electromagnetic radiation sources, as compared to the much lower temperature of conventional non-coherent light sources, the efficacy of optical intensity preservation during the focusing or imaging of laser beams, is close to 100%. Conventional non-coherent light sources, however safer to use, cannot be imaged without substantial intensity loss, due to the limitation dictated by the second law of thermodynamics.

All of the above-mentioned risks associated with visible and near infrared lasers have led to very strict governmental regulations regarding the operation of medical and esthetic laser-based systems, causing a substantial increase in the expenses of both manufacturers and operators of these systems. According to some of these governmental regulations, the operation of laser devices/systems is restricted to trained and skilled personnel, i.e. technicians or nurses under the supervision of a physician. In many countries, non-medical personnel such as cosmeticians are not allowed to handle laser-based systems at all. As a result the laser cosmetic business volume is restricted to a small fraction of its potential volume.

According to some aspects of medical and cosmetic laser systems, the treatment is focused on selected targets at the outer surface of the skin or within the skin. Each of these targets, for example, hair, vascular lesions, pigmented lesions, tattoos, mild collagen damages resulting in fine wrinkles, and sun-damaged skins, have different optical spectral absorption characteristics. Therefore, these applications utilize laser systems that are capable of generating visible or near infrared light having a wavelength within the range of 310-1600 nm. There exists, therefore, a risk of directing a laser beam having an incorrect wavelength to a selected treated organ/tissue, which may severely damage this organ/tissue. Even if the organ is treated by a laser beam having the correct wavelength, there is always a risk that the laser beam might be mistakenly aimed to other areas, which are highly sensitive to the selected wavelength, thereby resulting in damage.

As opposed to laser systems, non-laser incoherent diffused sources, such as Intense Pulsed Light (IPL) sources, which are based on high voltage arc lamps, are generally considered to be damage-safe from a distance, since IPL systems have a limited light source temperature (color), usually in the range of 1000- 10,000 °C, in contrast to as high as 1,000,000 °C in laser systems. However, IPL systems have reduced spectral selectivity due to their broad spectral bands. Consequently, IPL-based systems offer rather limited treatment capabilities in comparison to laser-based systems.

US 5,595,568 discloses a hair removal laser-based system, in which a convergent beam is utilized. The system is capable of focusing the beam before it reaches the treated area. A collimated coherent beam enters a transparent cell with convergence properties, and is slightly focused in the skin. However, the beam generated according to the method disclosed herein is extremely risky to the eyes.

US 5,879,346 discloses emitting a laser beam from an optical fiber. The laser beam is collimated or converged on a tissue by imaging the distal optical fiber at infinity or on the tissue. However, the beam generated according to this method is also extremely risky to the eyes.

US 6,197,020 and US 6,096,029 extend the (two) above-mentioned US Patents by imaging the distal surface of a bundle of optical fibers at a distance beyond the system in order to focus the beam below the tissue surface. The systems disclosed herein are also extremely risky to the eyes since all the laser energy is preserved even after transporting the beam to a distal confined spot. As opposed to the present invention, these two patents conform to the state of the art treatments by which the focusing of a collimated laser beam to subcutaneous locations is acceptable. G. Vargas and A. J. Welch, in their article "Effects of Tissue Optical Clearing Agents on the Focusing Ability of Laser Light within Tissue" ("Lasers in Surgery and Medicine", Supplement 13, 2001, p. 26) describe techniques for reducing the scattering of light energy within a tissue, in order to provide for a more focused spot and, thus, more efficient treatment of dermal lesions. However, as already described, there is a trade-off between the efficiency of a laser device and the potential risk in its operation; i.e., as the beam is more focused, the treatment becomes more risky.

US 5,226,907 discloses a coherent Nd:YAG laser for hair removal. US 5,059,192 discloses a coherent Ruby laser for hair removal. US 5,879,346 discloses a collimated Alexandrite laser beam with a scanner for hair removal. US 5,066,293 discloses a Dye laser with condensed beam for treating vascular lesions. US 5,312,395 and US 5,217,455 disclose laser systems for treating pigmented lesions and, US 4,976,709 and US 6,120,497 disclose coherent laser systems for treating non-ablative contraction of collagen or non-ablative skin rejuvenation. All of these laser systems utilize a coherent beam that is directed from a remote location to a limited treated area, without loss of coherence. The energy that is conveyed by the beam is scattered only within the treated skin/organ.

Another family of medical and esthetic lasers treat external, or depthless, skin faults. These kinds of lasers emit infrared beams, the energy of which is strongly absorbed by water. These beams have, therefore, poor penetration capability and are useful only for treatments at the outer (i.e. external) suface of the skin. Such lasers are, for example, Holmium lasers, CO2 lasers, Erbium lasers, etc., which are utilized for focused pin-point (e.g. having a diameter of 50-200 microns) and superficial (i.e. penetrating to a depth of 20-150 microns) ablations of epidermal or papillary dermal tissue in conjunction with a scanner for large skin coverage, as disclosed in US 5,411,502. Techniques for ablating larger tissue pits (i.e. having a diameter of 2-10 mm and depth of 20-150 microns) for skin resurfacing (by utilizing either a CO2 laser or an Erbium laser) are disclosed in US 5,558,660, in US 5,957,915 and in US 5,655,547.

The laser systems disclosed hereinabove utilize the coherent properties of a laser beam either for pin-point focusing of the beam, or for applying a larger and highly intensified beam to the treated area. Although very effective, these laser systems are risky, as already explained.

Currently, broadband non-coherent light devices, as opposed to monochromatic devices, are utilized, for wide range of esthetic applications. These devices usually include intense pulsed light source, such as described in US 5,626,631 and US 5,344,418, for treating vascular lesions, in US 5,885,773, for hair removal, and in US 5,964,749, for ablative skin rejuvenation. The devices disclosed in these disclosures are inherently non-coherent (i.e. they are considered to be extended scattered light sources). As such, these devices are useless if not kept relatively close to the treated area, and harmless to living organs. Consequently, such devices can be operated by non-medical staff, such as estheticians in many countries. However, these low-risk devices have a significant drawback, which is the broad spectral range of the energy emitted therefrom. Consequently the emitted energy cannot be optimally utilized for specific applications, which normally involves selective absorption of light (i.e. with a specific wavelength) by the chromophores contained within the treated organ. An additional drawback of performing a surgical procedure with an intense pulsed light, broad spectrum device concerns the selection, prior to treatment, of optimal values for a large number of parameters (e.g. spectral filters and time duration). Due to the large number of parameters, the learning curve is much longer (i.e. relative to laser systems) and results in a higher risk to patients.

Currently, frosted (optical) glass is utilized as part of ordinary illumination lamps. Incandescent and fluorescent lamps are manufactured either with a clear glass envelope or with a sand blasted frosted envelope. However, the light energy of illuminating lamps cannot be utilized for cutting, vaporizing or coagulating tissue from a distance, regardless of the closeness of the lamp to the treated tissue. Frosted glass is intended in such lamps to reduce the brightness of the light source.

US 4,736,743 discloses a Nd:YAG-based microsurgical laser system, in which miniature Sapphire tips are utilized as frosted elements. However, the Sapphire tips are intended to replace an electrosurgical scalpel by improving the vaporization of tissue whenever the tip is in contact with the tissue. For this matter, the frosted Sapphire tip is mounted to the beam-side of the tip that is in contact with the tissue, and consequently the heating and carbonization of the tissue is enhanced by allowing it fast vaporization. However, the tip(s) has to be cleaned from tissue debris after each usage. In addition, the frosted tips start the treatment from the outer surface of the tissue (incisions, vaporization, coagulation) and are not adapted for treating underlying lesions without affecting the outer surface of the skin as well. The frosted tips are also small (e.g. less than 1mm), and are usually sharp or rounded, and are intended for having close contact with the treated tissue. Another problem is that frosted tips, along with corresponding optical fibers, are detachable, whenever there is a surgical need, from the laser in use during surgical procedures, and are replaced by non-frosted optical fibers. Therefore, precautionary measures must be implemented while operating such high-class surgical laser systems.

US 5,449,354 discloses the utilization of radially frosted optical fibers in lasers for medical applications. These elongated frosted optical fibers are used interstitially deep inside tissues for the removal of tumors, or in cavities within the body for the treatment of bleeding organs. These frosted optical fibers are thin and used to coagulate a mass of tissue surrounding them. Similar fibers are intended for use in conjunction with a photodynamic procedure for therapy of cancer located within cavities. Such lasers are intended for relatively long operating periods (e.g. several minutes) at a very low power density (e.g. around 100 mW/cm2) in order to obtain a photochemical effect. The diffusing optical fibers, the design of which is described in e.g. US 5,527,308 and in US 5,814,041, are aimed at bringing the light energy into the body cavities or to conform to the shape of an organ and ensure homogeneous radiation. However, such laser systems are dangerous if mistakenly aimed at other bodily locations, including the eyes.

It is quite common to cool the surface of the skin during laser treatments of skin lesions. US patents 5,595,568 and 5,735,844 teach tissue cooling with a device which preserves the coherence of the treatment beam and does not reduce risks and does not scatter the treatment light. US patents 5,057,104 and 5,282,797 also teach tissue cooling and use smooth transparent surfaces. The tissue cooling devices used in conjunction with esthetic and surgical lasers do not reduce the risks associated with lasers and do not randomly scatter the laser beam, and as a result, allow operation only from short distances from the location to be treated.

US 6,011,890 and US 5,745,519 disclose systems, in which the output light energy of multiple low power laser sources are combined, thereby generating a higher power laser system. This technique is based on concentrating the light from spatially separated low power lasers into single optical fibers and bundling these fibers into a single light guide.

US patent 6,142,650 discloses a laser flashlight which is intended to illuminate criminal suspects and forensic scenes from a long distance while protecting their eyes. This patent utilizes multiple low power lasers split in different directions in a way that assures that the eyes are exposed to a limited number of beams. The patent does not convert the coherent lasers into non-coherent light sources and the lasers are not of the types utilized in laser surgery or esthetics.

The prior art laser units are not capable of generating a beam with a high energy level that may be used for esthetic or surgical procedures without presenting a risk of injury or damage to property, such as by igniting a fire.

It is an object of the present invention to provide an exit laser beam that may be used for surgical procedures.

It is another object of the present invention to provide an exit laser beam that is not injurious to an operator, observer or to objects located in the vicinity of or at a distance from a target location.

It is an additional object of the present invention to provide an exit laser beam that may be used for industrial applications.

Other objects and advantages of the invention will become apparent as the description proceeds.

Summary of the Invention The present invention relates to a method of improving the safety during exposure to a monochromatic light source, comprising: providing a monochromatic light source with a distal end, providing a frosted section that is transparent to the monochromatic light, attaching said frosted section to the distal end of the monochromatic light source, and allowing the monochromatic light to be randomly scattered by said frosted section, whereby at a first position of said frosted section relative to a target location the energy intensity of an exit beam from said frosted section is substantially equal to the energy intensity of the monochromatic light and at a second position of said frosted section relative to a target location the energy intensity of an exit beam from said frosted section is significantly less than the energy intensity of the monochromatic light.

The monochromatic light is a coherent laser beam, which is collimated or has the capability of being collimated. The monochromatic light is preferably selected from the group of collimated laser beam, convergent laser beam, concentrated multiple laser beams, or a combination thereof. Each of the concentrated multiple laser beams is preferably directable by a conical reflector.

The monochromatic light source is preferably selected from the group of Excimer, Dye, Nd:YAG, Ruby, Alexandrite, Diode, stack of diodes, LICAF, Er:Glass, Er:YAG, Er:YSGG, C02, isotropic C02 and Holmium lasers. The energy density level of the monochromatic light source preferably ranges from 0.01-2000 J/cm2, the duration of treatment at a target location preferably ranges from 1 nanosecond to 1500 msec, and the diameter of the treated area, normally referred to as spot size, preferably ranges from 1-20 mm.

The exit beam preferably remains scattered even though liquid residue accumulates on the frosted section.

The exit beam at the second position of the frosted section is substantially not injurious to eyes, skin or to objects disposed relatively proximate to the monochromatic light source. At a second position, preferably greater than 10 cm, the exit beam is not capable of igniting a fire.

The exit beam at the first position of the frosted section is suitable for treatment of lesions in human tissue. At a first section, the distance between the frosted assembly and the target location at the first position is preferably the smaller of 2 mm and the diameter of the monochromatic light. The energy density level of the beam and the duration of treatment at a target location are preferably selected so as not to cause a burn in the epidermis.

The refraction angle of the exit beam at the first position preferably exceeds 42 degrees relative to a vertical plane.

The exit beam at the first position is suitable for cosmetic and medical surgery, wherein the monochromatic light is preferably provided with a wavelength between 308-1600 nm. The exit beam is therefore suitable for applications selected from the group of hair removal, coagulation of blood vessels on the face and legs, as well as on other parts of the body, tattoo removal, treatment of rosacea, treatment of acne, removal of pigmented lesions in the skin, treatment of psoriasis, skin resurfacing, and skin vaporization. Likewise the exit beam may heat collagen, thereby inducing collagen contraction.

The exit beam at the first position is also suitable for dental applications wherein the monochromatic light is preferably provided with a wavelength between 308-1600 nm. Accordingly, the exit beam is suitable for removal of pigments from the gums and for teeth whitening.

The exit beam at the first position is also suitable for a treatment which requires a large amount of absorption by water present in tissue wherein the monochromatic light is provided with a wavelength between 1750 nm and 11.5 microns. Such a treatment is selected from the group of treatment of pain and dermatology including skin resurfacing, gynecology, podiatry and urology.

Likewise, the exit beam is suitable for laser welding of transparent plastic materials and for surface treating of materials, such as laser annealing, evaporation of paint and ink stains and for the cleaning of buildings, stones, antique sculptures and pottery.

In one preferred embodiment, the beginning of the exit beam is coherent for a predetermined length, after which it is randomly scattered.

In another preferred embodiment, the laser beam is controllably repositionable to scan target locations of the frosted section. The sequence of target locations to be impinged by the exit beam is preferably programmable.

The present invention also relates to a method of cooling skin which is irradiated with monochromatic light, comprising: a) providing a monochromatic light source with a distal end; b) providing a frosted assembly comprising a frosted section; c) attaching said frosted assembly to the distal end of the monochromatic light source; d) placing said frosted assembly on a skin location to be treated; e) providing means for skin cooling; f) allowing the monochromatic light to be scattered by said frosted section, whereby the energy intensity of an exit beam from said clear section is substantially equal to the energy intensity of the monochromatic light, the temperature of the skin location to be treated thereby increasing; and g) allowing said skin cooling means to cool said skin location, whereby upon repositioning of said frosted assembly from said target location to a predetermined position the energy intensity of an exit beam from said frosted section is significantly less than the energy intensity of the monochromatic light.

The frosted assembly may further comprise a clear section, the frosted and clear sections being transparent to the monochromatic light, a gap being formed between the frosted section and clear section, and the method further comprises the steps of placing said clear section on a skin location to be treated and inserting the skin cooling means within said gap.

In one aspect, the skin cooling means is a fluid transparent to the monochromatic light, said fluid flowing through a conduit inserted within the gap. The fluid is preferably in fluid communication with an external cooler.

In another aspect, the skin cooling means is a thermoelectric cooler, the thermoelectric cooler operative to cool the lateral sides of the section placed on the skin location to be treated.

The present invention also relates to an apparatus for improving the safety during exposure to an essentially coherent monochromatic light source, comprising a frosted assembly attachable to the distal end of the monochromatic light source, said frosted assembly including a frosted section that is transparent to the monochromatic light source, said frosted assembly adapted to allow the essentially coherent monochromatic light to be randomly scattered by said frosted section, whereby at a first position of said frosted assembly relative to a target location the energy intensity of an exit beam from said frosted assembly is substantially equal to the energy intensity of the monochromatic light and at a second position of said frosted assembly relative to a target location the energy intensity of an exit beam from said frosted assembly is significantly less than the energy intensity of the monochromatic light.

The monochromatic light is an essentially coherent laser beam. The monochromatic light source is selected from the group of Excimer, Dye, Nd:YAG, Ruby, Alexandrite, Diode, stacked diodes, LICAF, Er:Glass, Er:YAG, Er:YSGG, C02) isotopic C02 and Holmium lasers.

The laser unit is capable of generating a beam having a wavelength between 308-1600 nm or between 1750 nm to 11.5 microns. The energy density level preferably ranges from 0.01-2000 J/cm2 whose duration of treatment at a target location preferably ranges from 1 nanosecond to 1500 msec. The laser unit is preferably provided with a power level ranging from 1-2000 W, when under continuously working operation.

The frosted assembly is preferably essentially cylindrical. Alternatively it may be rectangular.

The material of the frosted section is preferably selected from the group of silica, glass, sapphire, diamond, non-absorbing polymer such as polyethylene, Mylar or polycarbonate, transparent paper, densely packed fibers such as a fiber bundle light concentrator, NaCl, CaF2, glass, ZnSe The frosted assembly is further provided with a clear section distal to the frosted section, the frosted and distal sections being mutually parallel and perpendicular to the longitudinal axis of the frosted assembly. Both faces of the clear section are preferably planar and smooth. The clear section is made of a material selected from the group of glass, sapphire, transparent polymer, NaCl, BaF2 and ZnF2.

The frosted and clear sections are preferably provided with the same dimensions. The gap between the frosted and clear sections is preferably less than 2 mm.

The frosted section is provided with a plurality of irregularities which are preferably randomly distributed. In one aspect the irregularities longitudinally protrude from a base substrate, and in another aspect they are embedded within the substrate and have an index of refraction different than the index of refraction of the substrate. The spacing between adjacent irregularities is preferably equal to the combined length of approximately 1-10 wavelengths of the monochromatic light. The slope of each irregularity with respect to the longitudinal axis of the frosted assembly preferably ranges from 0 to 50 degrees. Alternatively, the irregularities may be spherical. Alternatively, each irregularity is provided with a substantially equal diameter.

In one aspect, the frosted section may be formed by sandblasting or by etching, thereby producing irregularities. In another aspect, the frosted section is formed by a diffraction pattern or by a randomly distributed array of thin fibers. The array of thin fibers is preferably a conical fiber bundle light concentrator.

In another preferred embodiment, the apparatus further comprises a plurality of reflectors, the angular disposition and distance relative to the frosted assembly of each reflector being repositionable, whereby to accurately direct the monochromatic light to a selected target location on the frosted section. The apparatus also further comprises a processor, said processor suitable for the programming of the sequence of target locations to be impinged by the monochromatic light.

In another aspect, the apparatus further comprises a scanner for rapid repositioning of the monochromatic light to a target location on the frosted section.

The distance between the frosted assembly and the target location at the first position is preferably the smaller of 2 mm and the diameter of the monochromatic light.

The distance between the frosted assembly and the target location at the second position is preferably greater than 10 cm.

The frosted assembly is attached to the distal end of the monochromatic light source by an attachment means. In one aspect, the frosted assembly is fixedly attached to the distal end of the monochromatic light source. In another aspect, the frosted assembly is integrally formed together with the distal end of the monochromatic light source during manufacturing, the frosted assembly being disposed internally to the outer wall of the monochromatic light source. In another aspect, the attachment means is releasable. In yet another aspect, the attachment means is permanently attached to the monochromatic light source and displaceable, whereby in one position of a displaceable frosted assembly the monochromatic light source is coherent, not propagating through a frosted section, and in a second position at which said displaceable frosted assembly is attached to the distal end of the monochromatic light source, the monochromatic light is noncoherent, propagating through the frosted section.

In an additional embodiment of the present invention, the apparatus further comprises a means to evacuate vapors or particles from a target location to thereby prevent a change in optical properties of the frosted assembly. Particles may be produced during propagation of a monochromatic light having a wavelength less than 1800 nm.

The evacuation means is preferably U-shaped in vertical cross-section, to allow for contact with a target location at its lateral ends and for evacuation of vapor or particles through a gap formed by its central open region.

The evacuation means may further comprise a relay optics device, whereby to concentrate the exit beam from the frosted assembly onto the target location. A relay optics device is particularly useful during applications in which an excessive amount of smoke is produced and the exit beam becomes diffracted.

The relay optics device is preferably an optical regenerator, said optical regenerator being provided with an internal coating, such that said coating emits light energy when stimulated by incoming photons of a degraded exit beam. The optical regenerator is preferably tubular, a wall of the optical regenerator being formed with a smoke evacuation port.

The present invention also relates to an apparatus for cooling skin which is irradiated with monochromatic light, comprising: ' i. a frosted assembly attachable to the distal end of a monochromatic light source comprising a frosted section, said frosted assembly adapted to allow the monochromatic light to be scattered by said frosted section; and ii. means for skin cooling, whereby the energy intensity of an exit beam from said frosted assembly is substantially equal to the energy intensity of the monochromatic light upon placement of said frosted assembly at a position adjacent to a target skin location, the temperature of the skin location to be treated thereby increasing, said skin cooling means adapted to reduce the rate of increase of temperature at said target skin location, whereby upon repositioning of said frosted assembly from said target location to a predetermined position the energy intensity of an exit beam from said frosted assembly is significantly less than the energy intensity of the monochromatic light.

The frosted assembly preferably further comprises a clear section, said frosted and clear sections being transparent to the monochromatic light, a gap being formed between said frosted and clear sections, said skin cooling means being insertable within said gap.

In one aspect, the skin cooling means is a fluid transparent to said monochromatic light, said fluid flowable through a conduit inserted within the gap. The fluid is preferably a liquid or a gas and is in fluid communication with an external cooler.

In another aspect, the skin cooling means is a thermoelectric cooler, the thermoelectric cooler operative to cool the lateral sides of the section placed adjacent to the skin location to be treated.

In one aspect, the apparatus further comprises a scanner, said scanner being adapted to rapidly reposition the monochromatic light to a target location on the frosted section, the skin cooling means capable of continuously cooling the skin at a corresponding target skin location.

Brief Description of the Drawings In the drawings: Fig. 1 illustrates a side view of various laser units equipped with a frosted assembly, in accordance with the present invention, wherein the delivery system shown in Fig. la is an articulated arm, in Fig. lb is an optical fiber and in Fig. lc is a conical light guide; Fig. 2 illustrates a side view of the distal end of a laser unit, showing how the frosted assembly is attached thereto, wherein the frosted assembly is externally attached to the guide tube in Fig. 2a, is attached to a pointer in Fig. 2b, is releasably attached to the guide tube in Fig. 2c, is integrally formed together with the guide tube in Fig. 2d and is displaceable in Fig. 2e whereby at one position the exit beam propagates therethrough and at a second position the exit beam does not propagate therethrough; Fig. 3 is a schematic diagram of various configurations of prior art laser units, wherein Fig. 3a shows a non-scattered beam directed by reflectors to a target location, Fig. 3b shows a non-scattered beam directed by an optical fiber to a target location, Fig. 3c illustrates prior art surgery performed with a laser beam and scanner, Fig. 3d shows the propagation of prior art refracted laser beams towards a blood vessel, Fig. 3e shows an ablative laser beam focused on tissue in conjunction with a scanner, and Fig. 3f shows the formation of a crater in tissue by an ablative beam; Fig. 4 is a schematic diagram illustrating the advantages of employing a frosted assembly of the present invention, wherein Fig. 4a shows the relative location of the frosted assembly, Fig. 4b shows that a collimated laser beam is transformed into a randomly scattered beam, Fig. 4c shows that a scattered beam reduces risk of injury to the skin and Fig. 4d shows that a collimated laser beam reduces risk of injury to the eyes; Fig. 5 is a schematic drawing showing the propagation of a laser beam towards a blood vessel, wherein Fig. 5a shows the propagation of an unscattered laser beam towards a blood vessel, Fig. 5b shows the propagation of a scattered laser beam towards a blood vessel, Fig. 5c illustrates the formation of an ablation by means of an unscattered laser beam. Fig. 5d illustrates the formation of an ablation by means of an scattered laser beam in accordance with the present invention, and Fig. 5e illustrates the scattering of a laser beam distant from a blood vessel; Fig. 6a is a schematic drawing showing the accumulation of liquid residue on a frosted section and Fig. 6b is a schematic drawing in which a frosted section is shown to be mounted within a hermetically sealed frosted assembly; Fig. 7 illustrates the production of a plurality of microlenses, wherein Fig. 7a illustrates the sandblasting of a metallic plate, Fig. 7b illustrates the addition of a liquid sensitive to ultraviolet light, Fig. 7c illustrates the removal of the metallic plate and Fig. 7d illustrates the generation of a scattered laser beam through the microlenses; Fig. 8 is a schematic drawing of another preferred embodiment of the present invention in which a scanner rapidly repositions a coherent laser beam onto a plurality of target locations on a frosted section; Fig. 9 is a schematic drawing of another preferred embodiment of the present invention in which the coherence of the laser beam is retained for a predetermined length at the beginning of the exit beam, wherein a frosted section having a random array of craters is utilized as shown in Fig. 9a, a random array of fibers is used as shown in Fig. 9b, and a collimated beam is shown in Fig. 9c which diverges at a distance greater than the Rayleigh range; ~~ Fig. 10 is a schematic diagram of various means of cooling skin during laser-assisted cosmetic surgery, wherein Figs. lOa-d are prior art means, while Fig. lOe utilizes cooling fluid and Fig. lOf utilizes a thermoelectric cooler; and — Fig. 11 is a table that delineates the eye safety when being exposed to an exit beam from a frosted assembly.

Detailed Description of Preferred Embodiments Fig. la illustrates a high-intensity laser unit, generally designated by 10, which is suitable for use with the present invention. Laser unit 10 operates at a wavelength ranging between 300 and 1600nm or between 1750nm and 11.5 microns, either pulsed, with a pulse duration of 1 nanosecond to 1500 milliseconds and an energy density of 0.01-200 J/cm2, or continuous working with a power density higher than 1 W/cm2. Laser unit 10 is provided with a frosted assembly, generally designated by 15, which induces the exit beam to be randomly scattered. An exit beam is randomly scattered when its angular divergence is greater than 45 degrees relative to the propagation axis of collimated beam 4.

Laser unit 10 comprises amplifying medium 1 activated by power supply 2 for increasing the intensity of a light beam and two parallel mirrors 3 that provide feedback of the amplified beam into the amplifying medium, thereby generating a coherent beam of ultrapure frequency. The laser unit emits a coherent beam 4 which propagates through a delivery system 5 to distal end 6. The delivery system depicted in Fig. la is articulated arm 7a. Frosted assembly 15 is fixedly attached to the distal end of guidance tube 12 by attachment means 16, which may be a set of screws or by bonding or other means known to those skilled in the art, thereby inducing non-coherent randomly scattered beam 14 associated with a narrow spectral bandwidth that does not present any risk of damage to bodily tissue if the laser is inadvertently directed to an incorrect target location.

The frosted assembly includes a passive refractive element that preserves the wavelength of coherent beam 4, as well as its narrow bandwidth, which is generally less than one Angstrom.

Frosted assembly 15 is preferably cylindrical or rectangular, although any other geometrical shape is equally suitable, and comprises frosted section 13, which is proximate to distal end 6 of the laser unit and clear section 17. Both frosted section 13 and clear section 17 have the same dimensions and are bonded to frosted assembly 15. Frosted section 13 and clear section 17 are preferably separated by narrow gap 18. Due to the existence of gap 18, the laser beam will remain scattered even if clear section 17 shatters, thereby preserving the inherent safety of a laser unit that incorporates the present invention. The width of gap 18 is as small as possible, usually 0.1 mm. However, frosted assembly 15 may be adapted to a configuration in which frosted section 13 contacts clear section 17. Alternatively, frosted assembly may be provided without a clear section, whereby the frosted surface of frosted section 13 faces the laser unit and its smooth surface faces the tissue.

Scattering is achieved by means of minute irregularities of a non-uniform diameter formed on the substrate of frosted section 13. Frosted section 13 is preferably produced from thin (0.1 -0.2 mm) sand blasted or chemically etched glass or thin (usually less than 50 microns) sheet of non-absorbing light diffusing polymer, such as adhesive Scotch "Magic tapes" produced by 3M, USA, light diffusing polyethelyne, light diffusing polycarbonate, or Mylar. Similarly frosted section 13 may be produced from light diffusing paper such as transparent "Pergament" drawing paper, and may also be produced from other materials such as ZnSe, BaF2, and NaCl, depending on the application and the type of laser used. Both faces of clear section 17 are essentially planar and smooth. Clear section 17, which is capable of withstanding the thermal stress imposed by a scattered laser beam, is transparent and made from sapphire, glass, a polymer such as polycarbonate, and may be produced from other materials as well, such as ZnF2.

As depicted in Fig. lb,the delivery system may also be optical fiber 7b into which laser beam 4 is focused. Frosted assembly 15 is mounted on guidance tube 8, which directs the beam exiting the distal end of optical fiber 7b by attachment means 16. Furthermore, as depicted in Fig. 1, the laser unit may be comprised of array 11 of miniature lasers, such as those provided with high power diode lasers, e.g. the Lightsheer produced by Coherent, USA, for hair removal. The beam delivery system for this configuration is preferably conical reflector 7c. In this configuration, frosted assembly 15 is fixed to distal end 6 of light guide 7c and transforms the high- risk beam into randomly scattered beam 14.

Figure 2 illustrates various methods by which frosted assembly 15 is attached to a laser unit. In Fig. 2a, bracket 19 which supports frosted assembly 15 is attached to guidance tube 12 of an existing laser unit, such as one in use in a clinic, by attachment means 16a, which may be a set of screws or by bonding. As shown in Fig. 2b the laser unit is provided with pointer 31, or any other equivalent subassembly which enables the user to direct beam 4 to a desired target location on the skin, by the focal length and beam diameter which are dictated by lens 9 mounted within guidance tube 12. In this alternative, frosted assembly 15 may be externally attached to guidance tube 12, or may be attached to pointer 19. In Fig. 2c, frosted assembly 15 is attached to Velcro tape 16c, or another type of adhesive tape. This type of attachment means is sufficient for temporary usage. In Fig. 2d, frosted assembly 15 is integrally formed together with guidance tube 12 during manufacturing, internal to the outer wall thereof. Fig. 2e illustrates a releasable attachment means, whereby in one position of a displaceable frosted assembly the exit beam is coherent, not propagating through a frosted section, and in a second position in which frosted assembly 15 is attached to guidance tube 12, the exit beam is noncoherent and propagates through a frosted section.

In prior art cosmetic laser surgery, as shown in Fig. 3a, laser unit 20 emits a non-scattered coherent beam 24 from distal end 23 via reflectors 21, 22, by optical fiber 29 in Fig. 3b, or alternatively by deflectors 27 as shown in Fig. 3c, to site 26 that is to be treated within tissue 25. Following the surgery, a well-defined spot is generally produced having a size of up to 20 mm, depending on the specific application and device. Furthermore, beam 24 may be directed by means of motor 28 as shown in Fig. 3c in those situations in which extensive surgery is desired and tissue 25 needs to be scanned. When the wavelength ranges from 310-1600 nm, i.e. ultraviolet and near-infrared, the beam is scattered into individual rays 30, as shown in Fig. 3d, while propagating to blood vessel 32 from site 26. Blood vessel 32 is presented as an example and could be replaced by a hair follicle or any type of skin lesion. At wavelengths ranging from 1750 nm to 11.5 microns, i.e. far infrared, lasers are often used in focused pin-point ablation, that is, having a diameter ranging from 50-200 microns at a shallow depth of 20-150 microns, of epidermal or papillary dermal tissue in conjunction with a scanner, as shown in Fig. 3e. The lasers are used mainly for ablation of tissue, the formation of a crater shown in Fig. 3f. Laser 20, which is capable of effecting the desired surgery at a large distance between distal end 23 and target site 26 for the various applications shown in Figs. 3a-d, nevertheless can cause severe damage if the beam is not properly aimed.

In contrast, the present invention, which is schematically depicted in Fig. 4, presents a much lower risk to the patient and to observers. As shown in Fig. 4a, frosted assembly 15 is attached to distal end 9 of the laser unit. Frosted assembly 15 transforms the coherent, usually collimated laser beam 24 into homogeneous, randomly scattered beam 14 shown in Fig. 4b. As a result beam 14 significantly reduces risk of injury to the skin as shown in Fig. 4c or to the eyes as shown in Fig. 4d since a collimated beam is not directed to these parts of the body. At very short distances of less than one tenth of the diameter of beam 24 from distal end 23, beam 24 has not begun to completely scatter and increase its diameter and is therefore efficacious as a means for performing cosmetic surgery as shown in Fig. 4c, although an increase in the laser power level may sometimes be needed to compensate for reverse reflections from the frosted assembly into the laser unit. Compensation, in terms of an increase in the needed power level for the laser unit, for reverse reflections is usually be close to 16% due to four air-glass interfaces with 4% Fresnel reflection, and at times may attain 50%. An anti-reflection coating may be used to reduce reflection. For laser units which operate at approximately 10-20% of their maximum energy capacity, it is possible to place the exit plane of the frosted assembly, whether a frosted or clear section, at a distance from the skin corresponding to approximately 50% of the exit beam diameter.

Fig. 5 demonstrates the advantages of the present invention. Fig. 5a illustrates conventional coherent laser beam 24 at a wavelength of 308-1600 nm. The collimated beam contacts tissue 25 at a diameter of D before being scattered into individual rays 30 during propagation to target destination 32. Fig. 5b illustrates the result of attaching frosted assembly 15 to the laser unit. When frosted assembly 15 is disposed at a small distance from the tissue surface, the diameter of the scattered beam which contacts tissue 25 is increased by a negligible value of Ad, assuming uniform scattering, in comparison with the original beam diameter of D. If the thickness t of frosted assembly 15 is less than one-tenth of original beam diameter D, there will be a loss of less than 20 percent in the original beam intensity. Also, the refraction angle Θ, corresponding to an index of refraction of 1.5 for keratin, into the tissue relative to collimated beam 24, when a gap exists between frosted section 13 and clear section 17, will never exceed the critical angle of 42 degrees. At a refraction angle less than this critical value, possible additional scattering in tissue is minimized. Consequently light intensity within the tissue is preserved, therefore generally retaining the clinical efficacy, i.e. the ability to perform a surgical procedure, of the laser unit.

Just as superficial ablation 29 is formed in tissue 25 as a result of a high intensity beam in the 1.8-11.5 micrometer spectral range as shown in Fig. 5c, a similar ablation may be formed in tissue 25 with the use of frosted assembly 15, with the addition of Ad, as shown in Fig. 5d. A thin spacer (not shown) may be advantageously added in order to evacuate vapors or smoke that have been produced during the vaporization process. Such a spacer is e.g. U-shaped in vertical cross-section, to allow for contact with a target location at its lateral ends and for vapor evacuation along the gap formed by its central open region. For surgical procedures with which a very fast ablation rate is needed, e.g. 1 cm3/sec for a skin thickness of 0.1 cm, the spacer is necessarily relatively thick and the gap between the ablated tissue and the frosted assembly is relatively large, e.g. approximately 20-30 mm.

When an excessive amount of smoke is produced and the exit beam becomes diffracted before impinging on the tissue, it may be necessary to add a relay optics device (not shown), which regenerates the degraded exit beam between the frosted assembly and the tissue. An optical regenerator is provided with an internal coating, such that a new and stronger beam with the same characteristics as the degraded beam is produced when the coating emits light energy when stimulated by the incoming photons of the degraded beam. Cylindrical or conical tubes internally coated with gold with an inlet diameter equal to the exit diameter of the frosted assembly are exemplary optical regenerators for this application. A small smoke evacuation port is preferably drilled in the wall of the tube.

While the laser is an effective surgical tool when the frosted assembly is very close to the tissue surface, safety is ensured after the frosted assembly is repositioned so that it is disposed at a distance of a few millimeters, depending on the laser energy, from the tissue surface. As shown in Fig. 5e, the intensity of scattered beam 14 which impinges upon the surface of tissue 25 is much less than the beam intensity which results when the frosted assembly is proximate to the tissue surface.

The frosted assembly is adapted to induce random scattering despite any adverse external conditions encountered during the surgical procedure. The most likely cause of a potential change in rate of scattering of the laser beam passing through frosted assembly 15 results from contact with tissue. Following a surgical procedure in which the frosted assembly contacts tissue, liquid residue 36, such as sebum, water and cooling gel, as shown in Fig. 6a, may accumulate on frosted section 13. The refractive index of liquid residue 36 may be such that, in combination with the refractive index of frosted section 13, refracted beam 38 approaches the pattern of collimated beam 24 that impinges on the frosted assembly.

To minimize the risk of injury which may exist if the refracted beam is nearly collimated, frosted section 13 is mounted within frosted assembly 15, which is preferably hermetically sealed with sealing element 39 as shown in Fig. 6b, to prevent the accumulation of liquid residue on the former. Clear section 42 is attached to the distal end of frosted assembly 15 by adhesion and by means of a spacer (not shown), and is separated from frosted section 13 by air gap 41. Clear section 42 and frosted section 13 are mutually parallel, and both are perpendicular to the longitudinal axis of frosted assembly 15. When the air gap is less than a predetermined value, a corresponding increase in beam diameter due to scattering is limited, thereby ensuring a minimal effectiveness of the radiation carried by the laser beam for clinical applications. It would be appreciated that accumulation of liquid residue on clear section 42 will not compromise the inherent safety of a laser unit equipped with a frosted assembly. Since scattering occurs at frosted section 13, and the combined index of refraction of air gap 41, clear section 42 and liquid residue is not sufficient to cause the scattered beam to be once again collimated, the inherent safety of the laser unit is preserved. The accumulation of liquid residue will not affect the clinical efficacy of the laser unit since clear section 42 is held close to a target location during a surgical procedure.

An additional advantage resulting from the separation of clear section 32 from frosted section 13 relates to added safety. Even if clear section 42 is broken, frosted section 13 will scatter the laser beam.

A frosted section may be produced in several ways: • Sandblasting the surface of a plate with fine particles having a size of 1-200 microns, depending of the wavelength of the laser beam, comprised of, by example, aluminum oxide; • Chemical etching the surface of a glass plate with, by example, hydrogen fluoride; • Etching the surface of a glass plate with a scanned focused CO2 laser beam; • Applying a thin sheet of light-diffusing polymer, such as adhesive "Magic Tape" produced by 3M, USA, a light-diffusing polyethylene or polycarbonate sheet, Mylar high quality wax paper or graphical "Per game nt Paper" to a glass plate; • Generating a diffraction pattern on the surface of a glass plate by means of a holographic process to thereby control the divergence angle through the diffraction pattern; and • Providing a randomly distributed array of thin fibers, arranged e.g. in the form of a conical fiber bundle light concentrator, such as that produced by Schott, Germany.

Figure 7 illustrates the scattering effect that is achieved by sandblasting. As shown in Fig. 7a, metallic plate 50 is bombarded with aluminum oxide particles 48, thereby creating a random distribution of craters 51, each of which having a different size. Liquid 52, which is sensitive to ultraviolet light, is spilled on metallic plate 50 in Fig. 7b and polymerized by ultraviolet radiation. After removal of plate 50, for reuse in the next production batch, transparent frosted plate 53 is produced, as shown in Fig. 7c covered on one side with a random distribution of convex lenses 55 of miniature size. Lenses 55, which have a very short focal length of approximately a few wavelengths, convert a collimated laser beam into a strongly divergent beam with a complete loss of coherence. It is possible to use a similar technique to produce a surface with convex microlenses 57, as shown in Fig. 7d.

Fig. 8 illustrates an embodiment of the present invention by which tissue, having a larger surface area than the area of the beam impinging thereon, may be treated without overexposure to a laser beam. In prior art systems using a scanner, the treatment beam is quickly displaced in a programmable fashion from one location to another on the tissue to be treated. Although this method provides rapid and reliable treatment, there is a significant risk, however, that the laser beam is liable to be aimed at eyes, skin or flammable materials located in the vicinity of the laser unit.

The frosted assembly generally designated by 60 is shown. In this embodiment the frosted assembly is rigidly attached to delivery system 61, which is provided with a scanner. Frosted section 63 is formed with a plurality of visible target locations 66 and is placed close to the skin, facing the distal end of delivery system 61. Frosted assembly 60 is preferably provided with a clear section, as described hereinabove. Coherent collimated or convergent exit beam 64 is directed via a plurality of repositionable reflectors 65 to a predetermined target location 66 graphically indicated on frosted section 63. The beam that impinges upon a predetermined target location 66 is randomly scattered and converted into non-coherent beam 67 whose intensity is essentially similar to that of exit beam 64. Reflectors 65 are controllably repositionable by means of a scanner, whereby they may be displaced from one position and angular disposition to another, so as to accurately direct exit beam 64 to another target location 66. The sequence of which target location is to receive exit beam 64 after a selected target location is programmable and is preferably semi-random to reduce pain which may be felt resulting from the treatment of two adjacent target locations, with the time increment between two doses of laser treatment being less that less than a preferred value. A programmable sequence precludes on one hand the chance of a target location not to receive an exit beam at all, and on the other hand precludes the chance of not to be inadvertently exposed twice to the exit beam. With the usage of frosted assembly 60, small-diameter beams, e.g. 0.1-7.0 mm, may be advantageously employed to treat a tissue having an area of 16 cm2.

Fig. 9 illustrates another embodiment of the present invention in which the coherence of the original laser beam is retained for a predetermined length at the beginning of the exit beam, after which it is randomly scattered. This is achieved by using irregularities of equal diameter d, where d = SQRT( λ * L) , λ equaling the wavelength of the laser beam and L equaling the Rayleigh range, which is defined as the distance until the beam area is doubled. Since the irregularities are of an equal diameter, the laser beam is not immediately scattered upon impinging the frosted section. The optical propagation of the beam at the immediate exit of an irregularity of diameter d approaches a plane wave, wherein the beam diameter increases by a factor of 2 at distance L beyond the frosted section. The propagation at a distance greater than L is spherically divergent, and all of the rays mix by scattering at different angles of divergence and completely lose coherence. Therefore the effectiveness of treatment with the propagating laser beam is essentially retained for a distance of L.

The irregularities are randomly distributed on the surface of a transparent glass sheet and transform the glass sheet into a frosted section. The irregularities can be a random array of craters 150, e.g. chemically etched, formed in the proximal side of the glass sheet as shown in figure 9a. Similarly the irregularities may be a random array of fibers 151, such as those produced by Schott, Germany, as shown in Fig. 9b. As can be seen in Fig. 9c, collimated beam 152 impinges on frosted section 153 and propagates as a collimated beam for distance L corresponding to the Rayleigh range and diverges at a distance greater than L. The incorporation of a plurality of randomly distributed irregularities results in scattered beam 155 beyond distance L. The clinical advantage of this embodiment is to add the capability, if necessary, of applying a thick cooling layer, e.g. provided by a gel, between the skin and the frosted assembly. With the application of a cooling layer, the laser unit may be held at such a position that the distal end of the frosted assembly is separated approximately from the tissue to be treated, e.g. 1-2.

Fig. 10 illustrates another preferred embodiment of the invention in which a frosted assembly is provided with a skin cooling system. Transparent skin cooling devices are often used in conjunction with skin laser treatments. However they do not scatter laser light and do not reduce the risks associated with exposure to a laser beam. Figs. 9a-d illustrate prior art skin coolers. In Figs. 10a and 10b transparent lenses or plates 80 are in contact with tissue 79. Cooling liquid 81, which flows through conduit 83, conducts heat from the heated skin to a cooler. Treatment laser beam 82 propagates without being scattered through the cooling device and penetrates the skin. In Fig. 10c gaseous coolant 84 is used. In Fig. lOd, highly conductive plate 86 is in contact with tissue 79 and chilled by thermoelectric cooler 85.

As shown in Fig. lOe, frosted assembly 75 comprises frosted section 74, clear section 70 and conduit 71 formed therebetween. Conduit 71 is filled with a low temperature gas or liquid of approximately 4°C, which enters conduit 71 through opening 72 and exits at opening 73 .The cooling fluid preferably flows through a cooler (not shown). Frosted assembly 75 is positioned in contact with the skin, for treatment and cooling thereof. Clear section 70 is preferably produced from a material with a high thermal conductivity such as sapphire, in order to maximize cooling of the epidermis. Frosted section 74 is disposed such that its proximal face is frosted side and its distal face is planar, facing conduit 71. In Fig. lOf, the frosted assembly comprises frosted section 74 made from sapphire, which is chilled at its lateral sides 75 by thermoelectric cooler 76. The proximal side of 74 is frosted and the smooth distal side faces the skin. The parameters of the flowing fluid and of the cooler are similar, by example, to the Cryo 5 skin chiller produced by Zimmer , CA, USA .

The eye safety when exposed to the exit beam of the frosted assembly is significantly improved relative to prior art devices.

Parameters for eye safety analysis are presented in "Laser Safety Handbook," Mallow and Chabot, 1978. A laser beam which is reflected from a light diffusing surface is categorized as an extended diffused source if it may be viewed at a direct viewing angle A, greater than a minimum angle Amin, with respect to a direction perpendicular to the source of the laser beam. If a reflected beam may not be viewed at angle A, it is categorized as an intrabeam viewing source. Since a reflected beam is more collimated when viewed at a distance, viewing conditions are intrabeam if the distance R from the source of the laser is greater than a distance Rmax.

Another significant parameter is the maximum permissible exposure (MPE), which depends on the exposure duration and the laser wavelength. The safety level of a laser unit is evaluated by comparing the MPE to the actual exposure (AE) at the ocular pupil at a distance R from the laser source. The maximum permissible intensity (MPI) is the maximum laser energy per cm2 which allows a person to stare at a diffused object during total reflection of this energy. MPI is derived from MPE by multiplying it by Π. Since staring at the exit of a frosted assembly is equivalent to staring at a reflecting extended diffuser with 100% reflectivity, MPI is the maximum permissible intensity of a beam exiting the frosted assembly according to the present invention. The actual intensity (AI) of the treatment system is the actual energy per cm2 emitted from the frosted assembly. The ratio between MPI and AI indicates the safety level of the laser unit employing a frosted assembly. A ratio higher than 1 is essentially not regulated. A ratio between 1 and 0.1 would be close to high intensity flashlight sources used in professional photography and intense pulsed light sources used in esthetic treatments, and are much safer than prior art laser sources. Prior art laser sources which do not incorporate a frosted assembly have a ratio which is several orders of magnitudes lower than 0.1.

Fig. 11 is a table which presents a comparison in terms of eye safety between the exit beam of a laser beam with a frosted assembly, according to the present invention, and an intense pulsed light, both of which are used in cosmetic surgery. The parameters for a non-coherent diode-based laser unit are based on one produced by Diomed, UK. The parameters for a non-coherent Alexandrite-based laser unit are based on one produced by Sharplan/ESC (Epitouch). The parameters for a non-coherent Nd:YAG-based laser unit intended for vascular lesions are based on one produced by ESC (Vasculight). The parameters for a non-coherent Nd:YAG-based laser unit intended for photo-rejuvenation are based on one produced by Cooltouch, USA. The parameters for a non-coherent dye-based laser unit are based on one produced by ICN (Nlight). The parameters for an intense pulsed light laser unit are based on one produced by ESC. The parameters for a ruby Q-switch laser unit are based on one produced by Spectrum or ESC. The MPI for each wavelength and duration is based on the MPE tables delineated in "Laser Safety Handbook," by Mallow et al.

The table shows that the exit beam according to the present invention is essentially as eye-safe as broad band non-coherent intense pulsed light sources, such as those used for professional photography or those used for cosmetic surgery. The only laser unit employing a frosted assembly which is more risky, i.e. has a substantially lower safety level ratio, than a non-coherent intense pulsed light source is the ruby laser. It would be appreciated that that a ruby laser unit employing a frosted assembly is several orders of magnitude safer than a conventional ruby laser unit, which may have a MPI/AI ratio as high as 100,000-1,000,000. In view of the difference in safety between IPL systems currently in use, it is assumed that a MPI/AI ratio ranging from 1-0.1 is characterized as essentially being as safe as an IPL system.

As can be seen from the above description, a frosted assembly of the present invention, which is mounted to the exit aperture of a conventional laser unit, induces the exit beam to be scattered. As a result the exit beam is not injurious to the eyes and skin of observers, as well as to objects located in the vicinity of the target location. Nevertheless, the exit beam generally retains a similar level of energy as the beam generated from the exit aperture when the frosted assembly is very close to the target location, and is therefore capable of performing various types of treatment, both for cosmetic surgery and for industrial applications.

Example 1 An experiment was performed to demonstrate the efficacy of the present invention in which transparent light diffusing adhesive "Magic Tape," manufactured by 3M, having a thickness of 100 microns was attached to the distal end of an Alexandrite laser unit having a diameter of 8 mm. The energy level of the laser beam is 11 J/pulse. The laser beam was directed to the white (rear) side of a black developed photographic paper having a thickness of 300 microns. For comparison, the laser beam was also directed to the photographic paper without the use of the adhesive tape.

The ablation of the black paper after the beam had propagated and scattered through the white paper provides a visual simulation of the capability of the laser beam to penetrate transparent light-scattering skin in order to treat black hair follicles (or any other type of lesion) under the skin.

The energy of the laser beam transmitted through the adhesive tape, which caused the laser beam to scatter, was measured by directing the beam to an energy meter located at a distance of 1 mm from the distal end of the laser unit. The energy of the scattered laser beam dropped from 11 to 10 J. The results of this experiment indicate that the frosted section did not absorb a significant amount of energy, since a loss of 10% is expected in any case due to Fresnel reflection.

When the laser beam was directed to the white (rear) side of a developed photographic plate at a distance of 1 mm, an ablation of the black color on the opposite side of the photographic paper resulted. There was no difference in the results between usage of frosted tape or not. This experiment demonstrates that the performance of a non-coherent Alexandrite laser beam, according to the present invention, at a distance of 1 mm is essentially equal to the corresponding coherent laser beam.

When the laser beam was directed, without the addition of the frosted tape, at the photographic paper from a distance of at least 8 mm, an ablation resulted that is identical to that which was generated from a short distance of 1 mm. However, when a frosted tape was applied to the exit aperture of the laser unit from a distance of at least 8 mm, the scattered beam did not result in an ablation. Accordingly, the present invention allows for a high level of safety and lack of damage to bodily tissue when disposed at a relatively large distance therefrom.

Example 2 A long pulse Alexandrite laser unit having a wavelength of 755 nm, pulse duration ranging from 0.5-200 msec, and having an energy level of 1-20 J is suitable for hair removal.

The diameter of the frosted assembly ranges from 1-20 mm. The gap between frosted and clear sections is 10% of the beam diameter, ranging between 0.1-2 mm, depending on the diameter, and preferably 0.2 mm. The frosted section is made from glass or a light- diffusing sheet of polymer. The clear section is made for example from glass, sapphire or polycarbonate.

The prior art energy density of 10-50 J/cm2 is not significantly reduced with the employment of a frosted assembly.

A frosted assembly having a diameter of 1-3 mm is particularly suitable for lower energy lasers, which are relatively small, remove hair at a slower speed from limited area and are inexpensive. An application of such a laser, when employed with a frosted assembly, includes the removal of eyebrows. Eyebrow removal requires a relatively high level of precision, particularly at their periphery. A scanner, such as the Epitouch Alex model manufactured by ESC may be used to treat a relatively large area Example 3 A pulsed Nd:YAG laser unit having a wavelength of 1064 nm, pulse duration ranging from 0.5-200 msec, and having an energy level of 0.5-30 J is suitable for hair removal.

The diameter of the treated area, or spot size, ranges from 0.5-15 mm. The gap between frosted and clear sections is 0.2 mm. The frosted section is preferably made from fused silica, sapphire or polymer. A scanner may be integrated with the frosted assembly.

Example 4 A long pulse diode laser unit having a wavelength ranging from 810-830 nm, or of 910 nm or 940 nm, pulse duration ranging from 1-200 msec, and having an energy level of 0.5-30 J is suitable for hair removal.

The diameter of the treated area, or spot size, ranges from 1-20 mm. The gap between the frosted and clear sections ranges from 0.1-2 mm, and preferably is 0.2 mm. The frosted section is preferably made from fused silica, sapphire or polymer. A scanner may be integrated with the frosted assembly. The delivery system to which the frosted assembly is attached may be a conical light guide, such as that manufactured by Coherent or Lumenis, a guide tube produced e.g. by Diomed or a scanner produced e.g. by Assa.

Example 5 A continuous working diode laser unit having a wavelength ranging from 810-830 or 810-980 nm and having a power level of 10-300 W is suitable for hair removal. The invention converts a continuous working diode laser unit, which is in a high safety class and usually limits operation to the medical staff, into a lower safety class, similar to non-coherent lamps of the same power level.

The diameter of the treated area, or spot size, ranges from 1-10 mm, depending on the energy level. The gap between frosted and clear sections ranges from 0.1-2 mm, depending on the spot size, and preferably is 0.2 mm. The frosted section is preferably made from glass, sapphire or polymer. A scanner may be integrated with the frosted assembly.

A scanner, such as manufactured by Assa of Denmark or by ESC, may be used to displace a reflected collimated beam from one aperture to another formed within the frosted assembly. The scanning rate is variable, and the dwelling time at each location ranges from 20-200 msec.

The diode laser may also be used without a scanner, in which case the laser will be pulsed for a duration of approximately 10-200 msec.

Example 6 A Ruby laser unit having a wavelength of 694 nm, pulse duration ranging from 0.5-30 msec, and having an energy level of 0.2-20 J is suitable for hair removal.

The diameter of the treated area, or spot size, ranges from 1-20 mm. The larger spot sizes can be generated by Ruby lasers manufactured by Palomar, ESC and Carl Basel, which provide an energy density ranging from 10-50 J/cm2. The smaller spot sizes can be generated by inexpensive low energy lasers, which are suitable for non-medical personnel. The gap between frosted and clear sections ranges from 0.1-2 mm, and preferably is 0.2 mm. The frosted section is preferably made from fused silica, sapphire or polymer.

Example 7 High risk laser units, such as Nd:YAG having a wavelength of 1.32 microns and manufactured by Cooltouch, a dye laser having a wavelength of 585 nm and manufactured by N-Light/SLS/ICN, a diode laser having a wavelength of 1.45 microns and manufactured by Candela, or a Nd:Glass laser having a wavelength of 1.55 microns, may be used for non-ablative skin rejuvenation. This application is aimed at the treatment of rosacea, mild pigmented lesions, reduction of pore sizes in facial skin and mild improvement of fine wrinkles, without affecting the epidermis. The advantage of these lasers for non-ablative skin rejuvenation is related to the short learning curve and more predicted results due to the small number of treatment parameters associated with the single wavelength. By implementing a frosted assembly, the laser unit becomes safe and may be operated by non-medical personnel. The N-Light laser unit is initially operated at approximately 2.5 /cm2 for collagen contraction. The addition of a frosted assembly makes the laser unit as safe as an IPL. The diameter of the frosted assembly ranges from 3-10 mm.

A laser beam may be generated with a considerably less expensive laser unit, having an energy level ranging from 0.5-3 J and a slow repetition rate such as 1 pps, and generating a spot size ranging from 1-3 mm. In the case of wrinkle removal, the operator may follow the shape of the wrinkles with a small beam size. Such a non-coherent laser beam having a beam size of 1-3 mm is particularly suitable for estheticians. With this application, the gap between the frosted and clear sections should be close to 0.2 mm, smaller than one-tenth of the beam diameter.

Example 8 A pulsed Nd:YAG laser unit having a wavelength of 1064 nm and manufactured by ESC and having an energy level of 0.5-60 J is suitable for treatment of vascular lesions. The pulse duration ranging from 1-200 msec, depending on the size of the vessels to be coagulated (300 microns to 2 mm) and the depth thereof below the surface of the skin. A LICAF (Litium Calcium Fluoride) laser unit at a wavelength of 940 nm may also be advantageously used for this application, and its associated laser beam is better absorbed by blood than the NdrYAG or Dye laser. A Dye laser at a wavelength of 585 nm and manufactured by Candela and a quasi-CW KTP laser at a wavelength of 532 nm and manufactured by Laserscope or Iriderm may be used to treat vessels located at a low depth below the skin surface, such as those observed in port wine stain, telangectasia and spider veins.

The diameter of the treated area, or spot size, ranges from 1-10 mm, depending on the energy level. The gap between frosted and clear sections ranges from 0.1-2 mm, and is preferably 0.1 mm, depending on the diameter of the laser beam. The frosted section is preferably made from fused silica, sapphire or polymer. A scanner may be integrated with the frosted assembly.

Example 9 Q-Switch laser units having a pulse duration ranging from 10-100 nsec and having an energy density of 0.2-10 J/cm2 is suitable for removal of pigmented spots, mostly on the face and hands, as well as removal of a tattoos. A Q-switched Ruby laser as manufactured by ESC or Spectrum, a Q-Switch Alexandrite laser manufactured by Combio.and a Q-Switch Nd:YAG laser may be used for such an application.

The diameter of the treated area, or spot size, ranges from 1-10 mm, depending on the energy level. The gap between frosted and clear sections is approximately 0.2 mm. The diameter of the frosted assembly ranges from 1-10 mm. The frosted section is preferably made from glass, sapphire or polymer.

The addition of a frosted assembly to the aforementioned laser units renders pigmented lesion and tattoo removal by laser to be a considerably less risky procedure. Tattoo removal is achieved only by means of a laser beam, and is not attainable with intense pulse light sources.

The removal of pigmented lesions may also be performed with the use of an Erbium laser unit operated at a wavelength of 3 microns. Most pigmentation originates from the epidermis, and such a laser beam penetrates only a few microns into the skin. With implementation of a frosted assembly, this procedure may not necessarily be performed by medical specialists. Estheticians will be able to treat a large number of patients, particularly since an Erbium laser is relatively inexpensive. A scanner may also be used with this laser unit to treat a relatively large area of skin.

Another application of the present invention involves the field of dentistry, and relates to the treatment of pigmented lesions found on the gums. Q-switched as well as Erbium lasers may be used for this application.

Example 10 A Co2 laser may be used for wrinkle removal. In prior art devices, such a laser is used in two ways in order to remove wrinkles: by ablation of a thin layer of tissue at an energy density greater than 5 J/cm2 with a Coherent Ultrapulse, ESC Silktouch, or Nidek C02 laser and scanner for a duration less than 1 msec; or by non-ablative heating of collagen in the skin for lower energy densities, such as at 3 W, which may be achieved by operation of a continuously working ESC derma-K laser for 50 msec on a spot having a diameter of 3 mm.

With implementation of the present invention in which a frosted assembly is attached to a C02 laser, a laser beam having a wavelength of 10.6 microns may be generated. As opposed to other far infrared sources whose thermal and spectrally broad bandwidth involves less control of penetration depth, the interaction of a laser beam with tissue according to the present invention is highly controllable and its duration can be very short.

The frosted section is preferably made from a material that is transparent to a C02 laser beam such as ZnSe, NaCL or from polymers, e.g. polyethylene. The diameter of the frosted assembly ranges from 1-10 mm.

During ablation, the clear section of the frosted assembly may be separated from the tissue to be treated by a thin spacer having a thickness of approximately 1 mm to allow for the evacuation of vapors or smoke produced during the vaporization process.

Example 11 A Nd:YAG or oyher laser unit may be used for treatment of herpes. A diode laser with selective absorption of Cyanin green or other materials by fatty lesions may be used for treatment of acne. Both of these lasers may be used for treatment of hemorroids and for podiatric lesions on the feet.

Example 12 A dye laser unit operating at a wavelength of approximately 630 nm, 585 nm, or at other wavelengths when absorbed by porpherins, such as produced by Cynachore, Candela or SLS may treat acne lesions. The addition of a frosted assembly to the laser unit may considerably simplify the use of the laser by for such treatments by nurses and non-medical staff.

Example 13 CO2 laser units operating at an average power of approximately 1-3 W/cm2 are currently used by physicians to treat pain. The addition of a frosted assembly may enable the use of a highly safe device for that procedure in pain clinics by non- medical personnel. The delivery system of the laser beam may be an articulated arm or an optical fiber.

Example 14 It is advantageous to use an eye-safe laser unit for welding. The employment of a frosted diffusing section is an excellent way to reduce the risks associated with laser welding.

When welding thin transparent parts, such as those made from plastic, e.g with a diode laser unit, it is often advantageous to employ a large surface scanner or a large diameter beam which will irradiate a large surface area and selectively activate all target locations with appropriate chromophores (by heat). Such a scanner is in contrast to a scanner which is specifically targeted to the geometrical locations at which welding materials are present. The dwelling time of the welding laser beam at the target locations depends on the size of the welding element and the depth of material to be melted. The dwelling time is also dependent on the size of a target location treated in photothermolysis. As an example, welding a strip having a thickness of 50 micron to a substrate necessitates a dwelling time of approximately 1 msec, while a strip having a thickness of 200 microns requires a dwelling time of 16 msec. The dwelling time is proportional to te square of the thickness. Some welding chromophores are transparent in the visible part of the spectrum, but exhibit strong absorption in the near infrared part of the spectrum.

Example 15 Another industrial application for the present invention is associated with microstructures to be evaporated. Paint stains or ink may be selectively evaporated from surfaces such as clothes, paper and other materials that need cleaning by use of various pulsed lasers. One example of this application is related to the restoration of valued antiques. Another example is the selective vaporization of metallic conductors which have coated materials such as glass, ceramics or plastics. Vaporization of metallic conductors can be achieved with a pulsed laser, which is generally separated by a short distance from a target location and whose beam has a duration ranging from 10 nanosecond to 10 milliseconds. Pulsed Nd:YAG lasers are the most commonly used ablative industrial lasers, although other lasers are in use as well. Pulsed Nd:YAG industrial lasers may attain an energy level of 20 J concentrated on a spot of 1 mm, equivalent to an energy density of 2000 J/cm2. The addition of a frosted assembly to an industrial laser considerably increases the safety of the ablative device.

Pulsed Nd:YAG laser units are also suitable for improving the external appearance of larger structures, such as the cleaning of buildings, stones, antique sculptures and pottery. The laser units in use today are extremely powerful, having a continuously working power level of up to 1 kW, and are therefore extremely risky. The addition of a frosted assembly considerably improves the safety of these laser units.

A frosted assembly, when attached to an Excimer laser unit, is suitable for photo-lithography, or for other applications which use an Excimer laser unit for a short target distance.

With the addition of a frosted section, all of these applications become much safer to a user.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims. 147009/6

Claims (9)

1. Handpiece, comprising: (a) a bracket for transmitting light having an energy density ranging from 0.01 to 2000 J/cm2, a wavelength ranging from 308 to 1600 nm, and a pulse duration ranging from 1 nanosecond to 1500 msec through a distal end of said body to a skin target; (b) light delivery means for delivering said light from a light source to said distal end; c) a diffusing unit with a diffusively transmitting element mounted within said bracket, said diffusively transmitting element being transparent to said light; and (d) a thin U-shaped spacer adapted for contact with a target and allowing an evacuation of vapors or smoke produced during a skin treatment process.

2. The handpiece according to claim 1, wherein the spacer for distancing the diffusively transmitting element from the skin target is selected such that the evacuation of vapors or smoke which has been produced during the treatment process prevents a change in optical properties of the diffusing transmitting element.

3. The handpiece according to claim 1, further comprising, or in communication with, cooling means, said cooling means being in contact with the transmitting element.

4. The handpiece according to claim 3, which is suitable for evacuating vapors condensing on the transmitting element. 147009/6 -47-

5. The handpiece according to claim 1, wherein the spacer for distancing the diffusively transmitting element from the skin target includes walls that are positioned by means of the lateral ends thereof so as to be in sufficient contact with the skin target.

6. The handpiece according to any of claims 1 to 5, wherein said diffusively transmitting element has a plurality of irregularities which are randomly distributed.

7. The handpiece according to any of claims 1 to 6, wherein said diffusively transmitting element is selected from the group of silica, glass, sapphire, diamond, non-absorbing polymer, light -diffusing polymer, polycarbonate, acrylic, densely packed fibers, NaCl, LaF2, glass, ZnSe and BaF2.

8. The handpiece according to any of claims 1 to 7, wherein said diffusively transmitting element is provided with an anti-reflective coating.

9. Handpiece of claim 1, substantially as described and illustrated.