IL150094A - Method and apparatus for improving safety during exposure to a monochromatic light source - Google Patents

Description

Ref: 14825/02 "•umnDiJiTD TIN πρτ.'ρ ns'Ojn nun ηιττυηπ ΠΕΓΙΙΓΡ l nm ntriu METHOD AND 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 eye safe to bystanders.

Background of the Invention Current medical and aesthetic 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. The eye risk is further enhanced when using near infrared lasers which emit invisible radiation thereby leaving people unaware of the fact that a beam is being fired . Also the short pulse duration emitted by many laser systems doest leave people enough time to protect themselves from an accidental fire of the laser by blinking or moving the eyes.

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 . A very similar basic document which sets safety labeling standards by the food and drug administration (FDA) is $1040.10 21 CFR ch.1 An other document which sets manufacturing standards for the safety of eyes is ISO 15004: 1997E. 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, and are consequently of limited brightness and are not focusable to small spots, 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. 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. - 5 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 within a relatively small solid angle where an eye could be present. As opposed to the present invention, these two patents conform to the state of the art treatments by which the focusing of a laser beam to subcutaneous locations is acceptable and very large solid angles spanned by the beam are disadvantageous . More over, in these two patents, the use of large angles spanned by the fibers would have prohibited efficient imaging and focusing 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 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 close to the treated area, and are essentially harmless to living organs including the eyes . 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 clinical 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 from the laser, and whenever there is a surgical need, may be 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 aesthetic or medical lasers units often include a power or energy meter or are electrically connected to a power or energy meter to assure right treatment parameters. The systems do not include or are not connected to a radiance meter which measures the emitted energy per unit area per solid angle in order to check the eye safety of the system.

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 aestetic or 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 10 nanosecond to 1500 msec, and the diameter of the treated area, normally referred to as spot size, preferably ranges from 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 energy density at the first position is high enough to enable the treatment of unwanted aesthetic and other lesions such as hair removal, photorejuvenation , the treatment of vascular lesions , the treatment of pigmented lesions and tattoos and the treatment of acne, wheras the scattering angle from the frosted section is large enough to reduce the radiance of the converted system and classify the converted laser system as eye safe classl , meaning that the radiance ( energy/cm2/steradian) is below the maximal permitted energy allowed to be emitted from an extended diffused source , thereby enabling work without the use of protective eyeglasses.

The energy density at the first position enables the treatment of unwanted aesthetic and other lesions such as hair removal, photorejuvenation , the treatment of vascular lesions , the treatment of acne, and the scattering angle from the frosted section is large enough to assure that the radiance ( energy/cm2/steradian) essentially conforms with ISO 15004:1997E standard or ANSI Z 136.1 standard for eyesafe devices thereby drastically reducing the necessary eye safety precautions as compared to those associated with the use of high class safety lasers.

The scattering angle of the exit beam at the first position preferably exceeds 40-60 degrees relative to a vertical plane (80 -120 degrees full angle) or essentially approaches scattering from a Lambertian source.

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, tattoo and permanent makeup removal, gynecology, podiatry and urology.

In one embodiment of the invention, the beam which exits a laser with wavelength above 1.45 microns may not be randomly scattered , however should be strongly divergent beyond a plane which is in contact with skin during treatment, with a divergence angle large enough to assure eye safety according to standard ANSI Z 136.1 and skin safety at the second position and efficacy at contact in the first position.

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 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: One) providing a monochromatic light source with a distal end; Two) providing a frosted assembly comprising a frosted section; Three) attaching said frosted assembly to the distal end of the monochromatic light source; Four) placing said frosted assembly on a skin location to be treated; Five) providing means for skin cooling; Six) 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 Seven) 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 divergent and 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.

In one aspect of the invention the frosted assembly scattering angle is large enough to classify the laser system as eye safe classl , meaning that the radiance ( energy/cm 2/steradian) is below the maximal permitted energy allowed to be emitted from an extended diffused source , thereby enabling work without the use of protective eyeglasses The scattering angle from the frosted section is large enough to assure that the radiance ( energy/cm2/steradian)is close to or essentially conforms with ISO 15004: 1997E or ANSI Z 136.1 standards thereby drastically reducing the necessary eye safety precautions as compared to those associated with the use of high class safety lasers.

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 or acrylic , transparent paper, densely packed fibers such as a fiber bundle light concentrator, NaCl, CaF2, glass, ZnSe and BaF2.

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 such as polycarbonate or acrylic, 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 or an array of densely packed microlenses such as Fresnel lenses or concave or convex spherical lenses.. 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 a holographic diffraction patern or by a randomly distributed array of thin fibers. The array of thin fibers is preferably a conical fiber bundle light concentrator.

In one aspect of the invention, particularly when very large extended diffuser scattering angles are necessary to achieve eye safe conditions, a fiber or a microlenses array are placed in front of a tapered light guide which may be hollow or made from dielectric material and is coated with reflecting material. The papered light guide gradually increases the beams input angle. The tapering angle and the light guide dimensions are selected to attain a close to 120 degreed exit angle. A light diffuser is placed at the exit of the tapered light guide , followed by a flat protective window. The distance of the fiber from the tapered light guide is such that the intensity of unreflected light from the fiber at the light guide exit is low enough to assure eye safe conditions with the said diffuser.

In another aspect of the invention , large scattering angle sub assemblies are serially installed, each sub assembly consisting of a diffuser placed in front of a light guide with reflecting walls. Each subassembly gradually increases the scattering angle until the necessary exit angle for eye safe conditions is attained.

In another aspect of the invention more than one diffuser are present in the assembly , said diffusers are in essentially in contact during treatment thereby achieving high enough energy density for efficacy of treatment, and the diffusers are separated by a distance large enough to achieve class I eyesafety in case of accidental fire when the laser is not treating.

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: a. 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 b. 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.

In an other aspect of the invention , the pulse duration or the distance between pulses of a laser which emits trains of pulses is selected to be long enough to enable eye safe operation of the converted laser according with ANSI Z 136.1 standard with a diffuser with scattering angle between 10 degrees and 120 degrees.

In another aspect of the invention , particularly (although not solely) when invisible radiation is used , a small visible light flashing mechanism is added to the treatment handpiece , said flashing mechanism emits visible light prior to firing the treatment laser pulse, thereby providing a visible warning flash which enables the eye to blink or move in order to avoid staring at the light source in case of accidental firing of the laser beam in the direction of an eye.

In another aspect of the invention , a small visible light flashing mechanism is added to the treatment handpiece of a non laser high intensity light based treatment device such as used for hair removal or photorejuvenation or the treatment of vascular lesions which emits visible or invisible pulsed light of duration shorter than the eye blinking response time, said flashing mechanism emits visible light prior to firing the high intensity treatment pulse, thereby providing a visible warning flash which enables the eye to blink or move in order to avoid staring at the light source in case of accidental firing of the laser beam in the direction of an eye.

In another aspect of the invention a mean is added to the treatment system which enables the measurement of radiance (energy density per steradian) emitted by the system and thereby measures and confirms the eye safety of the system when used without protective eyeglasses.

In an other aspect of the invention an eye protective ring ( rim?) is attched to the treatment handpiece , said ring surrounds the distal end of the treatment handpiece and absorbs the reflected radiation from the treated skin thereby enhancing the comfort of the treating nurse.

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; Figure 7e illustrates an eye safe assembly which consists of the positioning of a fiber in front of a tapered light guide with coated reflective walls of dimensions and tapering which results with a very large exit angle ( such as 120 degrees ) , followed by a frosted assembly with lower scattering angle located at the exit of the light guide.

Figure 7f illustrates another embodiment whereby an array of microlenses is placed in front of the tapered light guide.

- Figure 7g illustrates another embodiment which consists of two serial 80 degrees holographic diffusers and coated light guides, which serve to generate a 120 diffusion angle! - Figure 7h illustrates a diffusing unit which utilizes an angular beam expander without a light guide; - 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 which utilizes two diffusers in contact in operating mode and separated in standby mode for enhanced eye safety in case of accidental fire of the laser .

- 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 half angle angular divergence is usually greater than 45-60 degrees relative to the propagation axis of collimated beam 4. 60 degrees half angle is very close to the half angle generated by an ideal Lambertian diffuser. The very large scattering angle is often necessary to achieve eye safe conditions due to the high energy density necessary for the clinical efficacy of the system.

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 noncoherent 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 or acrylic.

Frosted section may also be produced by using a large angle holographic diffuser such as produced by Physical optics corporation(PCO) , USA and distributed by EDMUND USA, placed almost in contact in front of an additional diffuser . The holographic diffuser may be of at least 80 degrees scattering full angle and the second diffuser adding additional scattering as necessary up to the an amount necessary to reach 120 degrees diffusion angle. There are additional embodiments which utilizes more than one diffuser as explained below and partially illustrated in figures 7g.

A close to Lambertian diffuser of 120 degrees may be produced from acrylic or polycarbonete by pressing material against an appropriate surface with a very densed array of Frensnel microlenses, such as produced by Fresnel Technologies inc. USA. Or by serially placing arrays of microlenses surfaces separated by waveguides as depicted in figures 7e. Achieving ideal Lambertian type of diffuser with a close to maximal 3.14 steradian scattering solid angle is the proffered configuration for the reduction of radiancy below the maximal permitted energy per solid angle 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 or acrylic , and may be produced from other materials as well, such as ZnF2. In all cases the frosted surface may be chilled if necessary in order to be capable to withstand the high power densities necessary to attain clinical efficacy.

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.

In the case of long wavelength lasers which do not focus on the eyes retina ( 1345nm -10.6 microns), an element which strongly diverges the beam at the exit of a surface which is in contact with the skin during treatment may be enough to assure eye safety ( without the use of a frosted element). Energy density should be kept high enough for efficacy, however very strong divergence will assure safety from a distance of a few cm. For example, a miniature 0.21 Joule/pulse Erbium laser which operates with a spot size of lmm2 ( 2.1 Joules/cm2 which is above threshold for tissue ablation), will be quite safe from a distance of 10 cm if the beam has a divergence angle of 90 degrees.

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, particularly designed to achieve diffusing angles larger than 80 degrees and as close as possible to 120 degrees or ideal Lambertian may be produced in several ways: • Sandblasting the surface of a plate of glass or Sapphire or acrylic or polycarbonate with fine particles having a size of 1-200 microns, depending of the wavelength of the laser beam, comprised of, by example, aluminum oxide; • Sandblasting the surface of a mold 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 and replicating the surface on pressed hot acrylic or other material • Chemical etching the surface of a glass plate or Sapphire 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, a light diffusing acrylic plate Mylar high quality wax paper or graphical "Pergament Paper" to a glass plate; • Generating a diffraction pattern on the surface of a glass plateor acrylic or polycarbonate by means of a holographic process to thereby control the divergence angle through the diffraction pattern which is preferably as high as 80 degrees or higher and using a second diffuser placed almost in contact with the first one to add additional diffusion if required, and the diffusers may be separated by lightguides if thermal dissipation problems are created by the contact between the dif users. The light guide can also be chilled in order to chill the diffuser if thermal damage may be generated with an uncooled diffuser if made from plastic materials.

• 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. The fiber bundle has a very large numerical aperture ( exit angle) , above 40 degrees half angle.

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 or concave microlenses 57, as shown in Fig. 7d. The process may also be replaced by pressing melted acrilic in the multimicrolens mold instead of using a UV curing technique.

Figure 7e illustrates a very wide angle (close to Lambertian) frosted assembly which is capable to endure high power laser levels by using glass made low angle diffusers. That kind of assembly is useful in cases where high energy densities are needed for clinical efficacy and only very wide angle scattering angles can assure eye safety. As depicted in the figure, fiber 201 is located in front of a tapered light guide 202. Rays that exit from fiber 201 with half angle divergence A impinge the inner walls of light guide 202. Rays 203 then are reflected from the inner walls of the light guide at an increasingly smaller reflection angle R. The walls are coated with a reflecting coating since impinging angles may be higher than the critical angle for total internal reflection. The tapering angle and the dimensions of the light guide as well as the distance of the fiber from the light guide are selected so that exit half angle C of diffused light 208 which propagates from distal end 204 of the light guide is at least 60 degrees. Also, the distance between fiber 201 and distal end 204 is selected so that the energy density of rays 207 emitted from fiber 202 to distal end 204 without any reflection from the light guide wall will be sufficiently low to be considered eye safe when scattered from small angle diffuser 205, which induces a relatively small scattering angle and is proximately placed with respect to distal end 204 of the light guide. A frosted plate 205 which may have a relatively small scattering angle is placed at the exit of the light guide. The following parameters can be selected to provide the necessary eye safe conditions: Fiber half angle divergence- 25 deg.; light guide input diameter: 15 mm; Light guide tapering angle: 3 deg.; light guide length: 142 mm; distance of fiber to light guide: 16 mm.

With the parameters stated above, the calculated intensity of the free beam from the fiber is approximately 400 times smaller than full intensity at the light guide exit (The area of the free beam emitted by the fiber is - 37a 400 larger than the exit area). With a 10 degrees diffuser at the light guide exit, which is 12 times more directional than a 120 degrees diffuser, (leading to a 12 **2 =144 higher brightness) the radiance ( J/cm2/strad) of scattered free beam 207 is 144/400 lower than the radiance of the 120 degrees extended diffused beam 208.) Figure 7f illustrates an embodiment whereby an array of microlenses 210 is installed in front of a tapered light guide as already described in Figure 7e. The array of microlenses 210 is particularly useful when the exit angle from the fiber in Figure 7e is small, resulting in a very long eye safe tapered light guide which may not be practically used in a clinic. Array 210 is configured such that light rays 203 that exit therefrom with half angle divergence A impinge the inner walls of hght guide 202.

Figure 7g illustrates two 90 degrees holographic diffusers 220 and 221 in contact with light guides 222 and 223, respectively. In order to increase the divergence, two holographic diffusers are used. Light rays 218 propagating from a monochromatic light source are scattered by diffuser 220 to a half angle of D and then are reflected within the inner wall of light guide 222. The scattered hght rays are further scattered by diffuser 221 to a half angle of E, are reflected within light guide 223, and exit the diffuser unit at a half angle of F, which approaches 60 degrees, the value corresponding to an ideal transmitting diffuser. The light guides are chilled in order to chill the holographic diffusers, which are often made from plastic material and otherwise may not tolerate high power lasers. Since the angular diffusion angle from a frosted element is a random process, the combination of two 90 degrees diffusers provide a 120 degrees diffuser ( ~ 90 X sqrt(2)).

Figure 7h illustrates diffusing unit 700, which comprises another type of - 38 angular beam expander, namely one which comprises a set of concave and .convex mirrors. Small angle fiber 701 from which light rays 703 exit with a small half angle divergence A, such as 5 degrees, is advantageously employed since diffuser unit 700 provides a high angular amplification. Half angle divergence A is selected so that a light ray 703 impinges on convex mirror 702 and is reflected therefrom to concave mirror 705. A ray 703 is further reflected from mirror 705 at an angle that enables it to impinge upon, and be scattered by, diffusively transmitting element 710, which is affixed to concave mirror 705.

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 - 39 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.

Fig9 illustrates another preferred embodiment of the invention in which two separated diffusers are used to enhance the eye safety of the system. In the operating position , the two diffusers 301 and 302 are brought in contact by the operator which places the treating handpiece 303 on the skin and essentially act as a single strong scattering diffuser. The energy density necessary to achieve efficient treatment is minimally affected and a slight increase of the laser energy can compensate for energy density losses. However, when the handpiece is not placed on the skin and the laser is not supposed to be fired, the diffusers separate with the aid of springs by a distance R large enough to assure that the energy density on - 40 diffuser 302 is low and the radiance from the outmost diffuser 302 is below eye safe level.

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, - 41 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. which brings ANSI Z 136.1. 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 eye exposure (MPE) while staring at a diffusing surface which totally reflects a laser beam. MPE depends on thelaser energy density ( J/cm2) , exposure duration and the laser wavelength and the solid angle into which the laser beam diffuses. The safety level of a laser unit is evaluated by comparing the MPE to the actual radiace (AR) of the laser the laser source. Staring at the exit of a frosted assembly is equivalent to staring at a reflecting extended diffuser with 100% reflectivity ., MPE is the maximum permissible radiance of a beam exiting the frosted assembly according to the present invention which doesn't necessitates protective eyeglasses at all according to either ANSI Z 136.1 or ISO 15004:1997 E. The maximal eyesafe permitted energy for the visible anf near IR radiation and an extended diffuser source is given, according to ANSI Z 136 .1, by 10*kl*k2*(tAl/3) Joules/cm2/steradian , t given in seconds where kl=k2=l - 42 for 400-700 nm wavelength, kl=1.25 and k2=l at 750 nra , kl=1.6 and k2=l at 810 nm , kl=3 and k2=l at 940 nm and kl=5 and k2=l at 1060 to 1400 nm. The safety limit set by ISO 15004 : 1997 E for pulsed radiation is 14 Joules/cm2/steradian.

The actual radiance (AE) of atreatment system is the actual energy per cm2 per steradian emitted from the frosted assembly. The ratio between MPE and AR indicates the safety level of the laser unit employing a frosted assembly. A ratio higher than 1 is essentially not regulated at all. . A ratio between 1 and 0.2 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. A ratio of 1-0.7 (up to 14 J/cm2/strad which is the highest permissible pulsed radiance reaching the eye per ISO 15004 : 1997 E )would indicate quite a safe laser without the use of any protective eye glasses. The ratio can go down to 0.7 since ISO allows for 30% inaccuracy of measurements. Prior art laser sources which do not incorporate a frosted assembly have a ratio which is several orders of magnitudes lower than 0.1 and necessitates the use of eye protective glasses as well as many other safety precautions.

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 which scatters light into a solid angle 3.14 strad which is equivalent to that attained by an ideal Lambertian diffuser 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 Dornier Germany, . The parameters for a noncoherent 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 hair removal are based on one produced by - 43 Altus (USA) or DEKA( Europe).. 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 MPE for each wavelength and duration is based on ANSI and ISO.

The table shows that the exit beam according to the present invention is essentially as eye-safe or safer than broad band non-coherent intense pulsed light sources, such as those used for professional photography or those used for cosmetic surgery.In many cases the converted laser sources do not necessitate any protective eyeglasses. In most cases they are safer than an accidental glance into the sun for a fraction of a second .It must be appreciated that the eye safety of some of the converted lasers is achievable only with very large scattering angle , close to 120 degrees or PAI (3.14) steradians. Small angle scattering may not be eye safe when operated at energy densities used in aesthetic treatments, although they are much safer than conventional coherent lasers.

The radiance ( energy/unit area/steradian) of the system can be measured to assure that the treatment system complies with the standards for laser eye safety. In one embodiment of the invention the converted laser system incorporates an eye safety measurement device ( " eye safety meter"). Such a device consists of an energy meter such as produced by OPHIR , USA and a lens with an aperture placed in front of the energy meter. The energy meter field of view is limited to a defined solid angle. The diffused assembly is brought to a defined position in front of the lens and imaged on the energy meter. The measured detected energy when the laser is fired - 44 divided by the aperture area and solid angle provides the radiance of the system. The laser may be used to authorize firing only if eye safety is confirmed.

There are cases where the eye safety of a laser such as an infrared laser which emits invisible radiation is enhanced by adding a preflashing device to the laser system. The preflashing device provides a short visible light flash a fraction of a second prior to firing the treating beam. The preflashing should occur approximately 0.25 seconds prior to firing the laser since protective blinking response to light takes approximately 0.25 seconds .Preflashing can be added also to pulse visible lasers or IPL sources. The preflashing device may be similar to camera flashes or utilize diodes as in some other cameras.

As can be seen from the above description, a frosted assembly with large diverging diffusing angle of the present invention, which is mounted to the exit aperture of a conventional laser unit, induces the exit beam to be scattered at a large angle.. 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. Protective eyeglasses are mostly not necessary or reduced to simple sunglasses thereby simplifying the work in the aesthetic clinic. Nevertheless, the exit beam generally retains a similar level of energy density as the beam generated from the exit aperture when the frosted assembly is very close or essentially in contact with the target location, and is therefore capable of performing various types of treatment, both for cosmetic surgery and for industrial applications. - 45 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 - 46 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.

The laser was also clinically tested for hair removal from arms and bikini lines of 10 patients using a 30 degrees diffuser and a 90 degrees holographic diffuser produced by Physical Optics Corporation ( USA ) placed in contact with a gel layer which was applied to the skin.

Energy density was 30 Joules/cm2. Pulse duration was 20- 40 milliseconds. The diffuser was applied to one side and the laser was used without a diffuser on the other side for comparison. Follow up of 4 months shows good results and no difference between the results obtained with or without the diffuser.

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. - 47 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 or acrylic.

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 such as produced by Deka ( Italy) having a wavelength of 1064 nm, pulse duration ranging from 0.5-100 msec, and having an energy level of 0.5-60 J is suitable for hair removal at energy densities of 35-60 J/cm2.

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, or sapphire. Diffusion angle is close to 120 degrees.

With an array of light guides a scanner may be integrated with the frosted assembly. - 48 Example 4 A long pulse diode laser unit having a wavelength ranging from 810-830 nm, or of 910 nm or 940 nmpulse duration ranging from 1-200 msec, and having an energy level of 0.5-30 J is suitable for hair removal at energy densities 30-50 J/cm2.

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 acrilic polymer.Diffusion angle is close to 120 degrees. 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 r or of 910 nm or 940 nm ( such as produced by Dornier, Germany), 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. Energy density is 20-40 j/cm2. 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 such as acrilic with scattering angle - 49 close to 120 degrees.. 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 20-300 msec.

The diode laser may also be used without a scanner, in which case the laser will be pulsed for a duration of approximately 10-300 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 with incresed pulse duration up to 40 milliseconds , a dye laser having a wavelength of 585 nm and manufactured by N-Light/SLS ICN, a diode laser having a wavelength of - 50 1.45 microns and manufactured by Candela, or a Nd:Glass laser having a wavelength of 1.55 microns with long pulse duration of 30 millisec , 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 and diffusion angle is 120 degrees full angle..

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 - 51 (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 Nd:YAG or Dye laser. A Dye laser at a wavelength of 585 nm and manufactured by Candela 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. In that case the frosted assembly utilizes two serial diffusers in contact during treatment and separated during non contact with the skin. 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. - 52 The addition of a double diffusers 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 - 53 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.

In another embodiment of the invention with a Co2 laser, it is possible to use a negative lens which strongly diverges the C02 laser beam from the treatment plane which is essentially in contact with the skin .In that case eye safety is achieved.

A second laser which may be used in that conjunction is an Erbium laser operated at energy density above 2 Joules /cm2. Ablation is shallower than attained with a Co2 laser and application can be extended to tatto or permanent make up removal. - 54 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 nmor 585 nm, or at other wavelengths which are absorbed by natural porpherins present in P acne bacterias , such as produced by Cynachore, or SLS may treat acne lesions, as well as laser operating at 1.45 microns as produced by Candella. The addition of a frosted assembly to the laser unit may considerably enhance their eye safety and simplify the use of the laser 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 - 55 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 photo thermolysis. 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 the 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 are coated on 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. - 56 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.

Claims (1)

1. 50094/2 57 An eye safe handpiece, comprising: a) a handpiece body for transmitting monochromatic light through a distal end of said body to a target, said distal end being positionable at a predetermined location substantially in contact with said target; b) light delivery means for delivering said hght from a monochromatic hght source to said distal end; c) means for directing the light which is transmitted through said distal end to said target; and d) a diffusing unit attachable to said body, said diffusing unit including at least one diffusively transmitting element that is transparent to said hght wherein a diffusing surface of said diffusively transmitting element is disposed internally to said handpiece body; wherein the energy density of the hght exiting said distal end at said position ranges from 1 to 90 J/cm2, wherein the radiance of the hght exiting said distal end at said position is less than 14 J/cm2/sr or less than 10*kl*k2*(tAl/3) J/cm2/sr, where t is a laser pulse duration in seconds, kl=k2=l for a wavelength ranging from 400 to 700 nm, k 1=1.25 and k2=l for a wavelength of approximately 750 nm, kl=1.6 and k2=l for a wavelength of approximately 810 nm, kl=3 and k2=l for a wavelength of approximately 940 nm, and kl=5 and k2=l for a wavelength ranging from 1060 to 1400 nm. The handpiece according to claim 1, wherein the target is a skin target. 150094/2 58 3. The handpiece according to claim 1, wherein the diffusively transmitting element has a proximal face and a distal face, the proximal face being a diffusing surface. 4. The handpiece according to claim 1, wherein the location at which the distal end is positioned is spaced from the target by a distance of less than one tenth of the diameter of a light beam exiting the distal end. 5. The handpiece according to claim 1, wherein the location at which the distal end is positioned is spaced from the target by a distance corresponding to less than 50% of the diameter of a light beam exiting the distal end. 6. The handpiece according to claim 1, wherein the monochromatic light is selected from the group of collimated laser beam, convergent laser beam, concentrated multiple laser beams, fiber guided laser beam, coherent and non-coherent intense pulsed light, and light emitting diodes. 7. The handpiece according to claim 1, wherein the monochromatic light source is selected from the group of laser units of pulsed Diode operating at a wavelength from 800 to 940 nm>' pulsed Dye, pulsed Alexandrite, pulsed Ruby, and pulsed Nd^YAG operating at a wavelength of approximately 1064 or 1320 nmi pulsed KTP operating at a wavelength of approximately 532 nm! Excimer, Dye, and Nd^YAG operating at a wavelength of approximately 1064, 1320 and 1440 nmi frequency doubled Nd^YAG, Ruby, Alexandrite, Diode including diodes operating at a wavelength of 810 to 830 nm, 150094/2 59 approximately 940 nm, and approximately 1450 nm; stack of diodes, LICAF, Er:Glass, Er:YAG, ErTSGG, C02, isotopic C02 and Holmium. 8. The handpiece according to claim 1, wherein the monochromatic light source is a non-coherent pulsed light emitting diode operating at a wavelength from 800 to 980 nm. 9. The handpiece according to claim 1, wherein the monochromatic light has a wavelength ranging from 400 to 1800 nm. 10. The handpiece according to claim 1, suitable for cosmetic applications and medical applications. 11. The handpiece according to claim 1, suitable for industrial applications and surface treatment of materials. 12. The handpiece according to claim 10, suitable for hair removal, coagulation of blood vessels located on a face or legs, treatment of rosacea, tattoo removal, removal of pigmented lesions in the skin, skin rejuvenation, treatment of psoriasis, treatment of acne, skin resurfacing, skin vaporization, collagen contraction, dental applications, removal of pigments from the gums, teeth whitening, dermatology, gynecology, podiatry, urology, and reduction of pain. 13. The handpiece according to claim 12, suitable for laser welding of transparent plastic materials. 150094/2 60 14. The handpiece according to claim 12, suitable for laser annealing, evaporation of paint and ink stains, vaporization of metallic conductors, and cleaning of buildings, stones, antique sculptures and pottery. 15. The handpiece according to claim 1, wherein the duration of a laser pulse ranges from 10 nsec to 3000 msec. 16. The handpiece according to claim 1, wherein the distal end is substantially planar and has a diameter greater than 3 mm. 17. The handpiece according to claim 1, wherein the material of each 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, CaF2, glass, ZnSe and BaF2. 18. The handpiece according to claim 1, wherein the diffusing unit is further provided with a clear transmitting element distal to a diffusively transmitting element, the diffusively transmitting element and clear transmitting elements being mutually parallel and perpendicular to the longitudinal axis of the diffusing unit. 19. The handpiece according to claim 18, wherein the clear transmitting element is made of a material selected from the group of glass, sapphire, transparent polymer including polycarbonate and acrylic, BaF2, NaCl and ZnF2. 150094/2 61 The handpiece according to claim 18, wherein the distance between the proximal face of the diffusively transmitting and clear transmitting elements is less than 2 mm. The handpiece according to claim 1, wherein each diffusively transmitting element is provided with a plurality of irregularities which are randomly distributed thereabout. The handpiece according to claim 1, wherein the diffusively transmitting element is formed by a diffraction pattern or by a randomly distributed array of thin fibers. The handpiece according to claim 1, wherein the diffusing unit comprises a holographic diffuser. The handpiece according to claim 1, wherein the diffusing unit further comprises a reflective and/or a refractive optical element. The handpiece according to claim 1, wherein the diffusing unit further comprises at least one light guide. 26. The handpiece according to claim 25, wherein the light guide is made of a material selected from the group of solid glass, sapphire, plastic and liquid dielectric material. The handpiece according to claim 1, which comprises monochromatic light source. 150094/2 62 28. Apparatus, in addition to the handpiece as defined in any of claims 1 to 27, further comprising a scanner. 29. Apparatus, in addition to the handpiece as defined in any of claims 1 to 27, further comprising means for skin cooling. 30. Apparatus according to claim 29, further comprising means for adjusting skin temperature in conjunction with the skin cooling means. 31. Apparatus, in addition to the handpiece as defined in any of claims 1 to 27, further comprising means for measuring the radiance of the light exiting the distal end. 32. Apparatus according to claim 31, further comprising control circuitry in communication with the radiance measuring means, for generating a warning or deactivating the light source, as a result of a mishap, if the radiance of light exiting the distal end is greater than a predetermined safe value. 33. Apparatus, in addition to the handpiece as defined in any of claims 1 to 27, further comprising means for setting the energy density of light exiting the distal end. 34. Apparatus, in addition to the handpiece as defined in any of claims 1 to 27, further comprising at least one component selected from the group of means for cooling the diffusively transmitting element, means for controlling pulse duration in accordance with the color of the target or skin type of a patient, means for positioning the distal 150094/2 63 end at a predetermined location substantially in contact with the target, and means for repositioning any of the aforementioned components from the vicinity of a first target to the vicinity of a second target. 35. Method for laser welding, comprising: a) providing apparatus according to any of claims 1 to 9, 15 to 28, and 31 to 34; b) attaching a diffusing unit to a handpiece body," c) applying welding material to a target; d) positioning the distal end of the handpiece body at a predetermined location substantially in contact with said target; e) setting the energy density and pulse duration of monochromatic light exiting the distal end in accordance with properties of an element to be welded including its spectral properties, size, depth from upper surface, and its thermal properties; and f) firing the light source for a sufficient period of time to allow said element to be welded. 36. Method for surface treatment of materials, comprising: a) providing apparatus according to any of claims 1 to 9, 15 to 28, and 31 to 34; b) attaching a diffusing unit to a handpiece body; c) positioning the distal end of the handpiece body at a predetermined location substantially in contact with a target; d) setting the energy density and pulse duration of monochromatic light exiting the distal end in accordance with 150094/2 64 properties of a target to be ablated including its spectral properties, size, depth from upper surface, and its thermal properties; and e) firing the light source for a sufficient period of time to allow said target to be ablated. 37. The method according to claim 36, wherein the target to be ablated is selected from the group of paint or ink stains, a metallic coating, buildings, stones, antique sculptures and pottery. 38. The method according to any of claims 35 to 37, wherein the energy density of the monochromatic light is approximately 200 J/cm2. LU22ATTO a^Krr