WO2003103523A1

WO2003103523A1 - Eye safe dermotological phototherapy

Info

Publication number: WO2003103523A1
Application number: PCT/IL2003/000277
Authority: WO
Inventors: Michael Slatkine
Original assignee: Inolase 2002 Ltd.
Priority date: 2002-06-06
Filing date: 2003-04-03
Publication date: 2003-12-18
Also published as: WO2003103523A8

Abstract

A method and apparatus are disclosed for improving bodily safety during exposure to an intense pulsed light source (4) by diverging the light, such as with a diffuser (15). At a first position of the distal end of the light source the energy density of exit light from the distal end is substantially equal to the energy density of the light required for desired applications, such as effecting an aesthetic improvement, and at a second position of the distal end the radiance of the light emitted therefrom is significantly less than the radiance of the intense pulsed light. Eye safety is further enhanced by attaching at least one element of adjustable opacity to the handpiece of the light source, so that subcutaneously backscattered light may be absorbed by the at least one element.

Description

EYE SAFE DERMOTOLOGICAL PHOTOTHERAPY

Field of the Invention

The present invention is related to the field of intense pulsed light sources. More

particularly, the present invention is related to providing an eye-safe, intense

pulsed light source that is suitable for correcting aesthetic skin disorders that

require a very high energy density. Even more specifically, the present invention

is related to a method and apparatus for improving bodily safety during exposure

to an intense pulsed light source, by diverging the intense pulsed light which

provides the required energy density of light for desired applications at a very

short distance, but is inherently safe to the eyes of bystanders.

Background of the Invention

Intense Pulsed Light (IPL) sources are used for the treatment of a variety of

aesthetic skin problems, including hair removal, skin rejuvenation including

wrinkle removal, treatment of vascular lesions, treatment of acne, etc. Intense

pulsed light sources are broad band sources, such as Xenon flash lamps, spectrally

filtered to obtain narrower and more selective emission wavelengths. Typical

energy density levels utilized in hair removal are 5-50 J/cm², with pulse durations ranging from approximately 3 to 300 msec. IPL sources are mostly operated in a

multiple pulse train mode such as a 50 msec pulse which consists of three pulses

of 3 msec each with a 20 msec delay between the pulses. The treatment area is

often close to 1 x 4 cm. Such treatment is generally conducted by trained personnel, such as nurses under

the supervision of a physician. Aesthetic systems based on high intensity light are

divided into monochromatic pulsed laser sources, such as described in US Patent

No. 5,879,346 and non-coherent broad-band IPL sources, such as described in US

Patent Nos. 5,683,380, 5,885,273, 6,187,001, 6,280,438, 6,214,034, 5,964,749, and

6,387,089.

These prior art systems are extremely risky to the eyes and may cause blindness if

a bystander or a patient accidentally stares at the distal end of the treatment

system. As a result, the safety level of prior art laser and IPL sources utilized for

aesthetic treatments is such that protective eyeglasses are mandatory. The use of

both laser and IPL sources without supervision of a physician is prohibited in

many countries.

In addition to the accidental risk associated with directly staring at the distal end

of a pulsed light based treatment device without wearing protective eyeglasses,

there is a longer term risk associated with unavoidable staring at the treatment

site. The treated skin backscatters bright light which originates from the

treatment device, and the backscattered light repeatedly reaches the eyes of an

operator, causing severe eye fatigue .

The conversion of an IPL aesthetic source into an inherently eye-safe device which

does not require medically trained operators and which does not necessitate the

use of inconvenient protective eyeglasses would therefore be advantageous. Protective eyeglasses, which are needed for the attenuation of backscattered

treatment light and should transmit ambient illuminating hght having a broad

band spectrum for adequate visibility, limit the field of view of an operator and are

opaque at a broad range of wavelengths, resulting in a darkened treatment site.

The need for protective eyeglasses during aesthetic treatments is obviated if the risks associated with direct staring at the distal end of an IPL source and with

skin backscattering are eliminated. Co-pending International Patent application

PCT/IL02/00635 by the same applicant, the description of which is incorporated

herein by reference, discloses a laser unit suitable for aesthetic treatment, which

is converted into an eye-safe laser unit.

One cause of eye risk associated with aesthetic treatments with a non-coherent

IPL source is the possibility of staring directly at the flash lamp through a light

guide (see Fig. 2). When a light guide is not employed, as described in U.S. Patent

No. 6,187,001, direct view is even more probable. The energy density emitted

directly from a flash lamp, e.g. having a size of 3 x 40 mm, may reach an energy

density level of 40-60 J/cm² or higher. The flash lamp may be considered a diffused

light source which emits energy at a solid angle close to 3.14 steradians, achieved

by ideal diffuser sources with 100% transmission and provided with Lambertian

angular scattering properties. As a result, the radiance, i.e. the energy density per

solid angle, of the flash lamp is close to 15-20 J/cm²/steradian. In many cases

radiance may be even higher than that level. The maximal permitted radiance or accessible emission limit (AEL) emitted from

an extended diffused light source used without protective eyeglasses is given in

the FDA eye safety standard 1040.10 21 CFR Ch.l and in the ANSI Z136.1

standard, and is a function of wavelength and pulse duration. If divided into

narrow spectral segments, the radiance for each spectral segment is given by the

equation:

AEL = 10 * kl *k2 * T ^A 1/3, where kl equals 1 in the visible part of the

spectrum, 1.6 at a wavelength of approximately 800 n , 3 at a wavelength of

approximately 980 nm and 5 at a wavelength of approximately 1064 nm, k2 =1,

and T is the pulse duration expressed in seconds.

Most intense pulsed light sources operate in spectral bands having a lower limit of

approximately 585 nm (kl=l) or 645 nm wavelength (kl =1) for photorejuvenation

and 755 nm (kl=1.3) or 810 wavelength (kl=1.6) for hair removal. The energy

content at a higher wavelength is smaller. As a result, the maximal permitted

radiance from IPL sources approximates AEL = 10 * 1.5 * T ^Λl/3. For a pulse

duration of 3 msec often used for photorejuvenation, which is strongly based on

absorption of light in extremely thin vessels with a thermal relaxation time of less

than 1 msec, the AEL is approximately 3 J/cm²/sr, a value much less than the

radiance emitted by a flash lamp of 15-20 J/cm²/sr, as referred to hereinbefore. An

IPL source used with high efficacy in aesthetic treatments is therefore not eye-

safe and emits a radiance which may be 6-13 times above the safe limit set by the

aforementioned FDA standard. It will be appreciated that even a factor of 2 above the accepted standard for eye safety requires the use of inconvenient protective

glasses during an aesthetic treatment.

It will be appreciated that there is a trade off between the efficacy of an intense

light source used in aesthetic treatments and the corresponding eye or skin safety.

As the efficacy is higher, the energy density is higher, and therefore there is a higher risk of burning the skin since such an intense light source is in contact

with the skin. To prevent skin burning, some prior art intense light sources are

provided with a chiller, which chills the skin just before firing the IPL.

Although a variety of IPL sources are used in the treatment of aesthetic skin

disorders such as devices produced by LUMENIS USA (Epilight, Quantum),

RADIANCY, PALOMAR (USA), DEKA (ITALY), SYNERON (Israel), and the

fluorescent frequency-shifted PLASMALITE™ (USA, SWEDEN), they all suffer

from the high risk associated with the existence of a direct line of sight between a

flash lamp and the eye. Furthermore, prior art aesthetic systems which utilize

high energy, short pulse duration flash lamps for hair removal, wrinkle removal,

skin rejuvenation or the treatment of acne, lack protective measures, such as a

light diffuser placed within the line of sight between the flash lamp and skin,

which would obviate the use of protective eyeglasses during the treatment.

As mentioned above, in order to completely eliminate the necessity of wearing

inconvenient protective eyeglasses during aesthetic treatments with IPL sources, the amount of backscattered treatment light which reaches the eyes should also be

reduced .

Protective eyeglasses used in conjunction with IPL sources, such as those

produced by Glendale USA, Laser-R Shield USA, Bolle, France, or Yamamoto,

Japan are generally based on selective absorption of light by an optical filter.

Since the protective eyeglasses used to reduce broad band radiation associated

with IPL sources are dark, the visibility of the treatment site, which is usually

illuminated by broad band radiation, is similarly reduced. Other protective

eyeglasses, such as those disclosed in US Patents Nos. 4,462,661, 5,671,035,

5,022,742, 5,841,507, 5,519,522, 4,968,127, 5,208,688 and 6,170,947, are based on

the attenuation of light by liquid crystal devices. These prior art devices are

relatively heavy and cumbersome, and limit the field of view of an operator.

Additional aesthetic systems related to the current invention are devices

incorporating both IPL and laser sources in a single system. For example, a

"Quantum" system produced by LUMENIS incorporates a spectrally broad-band, non-coherent IPL source for hair removal or photorejuvenation and a

monochromatic coherent Nd.YAG pulsed laser operated at 1064 nm for the

treatment of leg veins. Coherent laser sources, like all prior art aesthetic lasers,

are extremely risky to the eyes, having a radiance which is often more than 10,000 times above the AEL .

Other relevant prior art is disclosed in US Patent Nos. 5,595,568, 5,879,346,

5,226,907, 5,066,293, 5,312,395, 5,217,455, 4,976,709, 6,120,497, 5,411,502, 5,558,660, 5,655,547, 5,626,631, 5,344,418, 5,964,749, 4,736.743, 5,449,354,

5,527,308, 5,814,041, 5,595,568, 5,735,844, 5,057,104, 5,282,797, 6,011,890,

5,745,519, and 6,142,650.

If the eye safety level of a laser and of an IPL source were reduced to a level below

that listed in the aforementioned standards, such a device would be able to be

operated by personnel without any medical background, such as aestheticians,

and also by individual users at home.

Prior art IPL sources used for aesthetic treatments are incapable of generating

non-coherent light at both a high enough energy density, which would assure

treatment efficacy, and at a low enough radiance, which would not present a risk

of injury to the eyes of bystanders .

It is an object of the present invention to provide a non-coherent IPL source that

may be used for aesthetic procedures.

overcomes the disadvantages of the prior art.

It is another object of the present invention to provide an IPL source that is not

injurious to the eyes of an operator or of an observer located in the vicinity of, or at

a distance from, a target. It is yet another object of the present invention to provide an IPL source which

does not necessitate the use of protective eyeglasses, without causing severe eye

fatigue.

It is yet another object of the present invention to provide an IPL source which

could be operated by personnel without any medical background.

Other objects and advantages of the invention will become apparent as the

description proceeds.

Summary of the Invention

The present invention comprises a method of improving bodily safety of

bystanders exposed to an intense pulsed light directed to a target, comprising: providing a source for generating intense pulsed light, causing said source to

generate at least one pulse of polychromatic light, directing said pulsed light to a

target, and diverging said pulsed light at a diverging location between said source

and said target, whereby the energy density of light exiting from said diverging

location is substantially equal to the energy density of the intense pulsed light,

and at a distance from said diverging location the radiance of said exiting light is

significantly less than the radiance of the intense pulsed light.

As referred to herein, "intense pulsed light" is defined as polychromatic hght

delivered by at least one pulse, which may be supplemented by energy at radio

frequencies being directed at the target simultaneously with said light. Likewise an "intense pulsed light source" is defined as an instrument that generates said

intense pulsed light or fluorescent pulsed light (FPL), wherein said instrument

may comprise an optical frequency shifter for shifting the wavelength of the

pulsed light being directed to the target.

Preferably, said pulsed light source is provided with an assembly connected to the

light source, for directing said light to said target, which assembly will be called

the light propagation assembly and the diverging location is the distal end of said

propagation assembly. Also preferably, a scattering unit is provided at said

diverging location, said unit comprising at least one scattering element, also called

hereinafter "diffuser," wherein each of said scattering elements or diffusers is

transparent to said intense pulsed light. As this term is used herein, "scattering"

means randomly changing the direction of adjacent light beams so that they

randomly diverge from one another, without any substantial change in the

wavelength of the incident light. Scattering is typically caused, and is caused in

the present invention, by the structure of a medium through which the light

propagates.

As referred to herein, "distal" means a location closer to a target, and therefore

more distant from the light source; "proximate" means a location more distant

from a target, and therefore closer to the light source; "axial" means a direction

from the center of the light source to the center of the target; and "transversal

means a direction perpendicular to the axial direction. Therefore, if the propagation assembly is so placed that the diverging location is close to a first target, light having substantially the energy density of the generated pulsed light

will impinge on said first target, but light having a significantly reduced radiance

will impinge on a second target that is farther away from said diverging location.

If the first target is the intended target of an optical treatment and the second

target is an object that might be hurt by the intense pulsed light, the method of

the invention will combine the effectiveness of the optical treatment while

protecting objects that are not the intended targets of the treatment. Hereinafter,

it will be said that the distal end of the propagation assembly is "in the first

position" with respect to a target close to said assembly, tjφically the intended

target of an optical treatment, and "in the second position" with respect to an

object distanced from said assembly, typically an object that might be hurt by the intense pulsed light.

In another aspect, the method further comprises:

a) providing a diffusing unit transparent to the intense pulsed light

comprising at least one angular beam expander and at least one diffuser; b) attaching said diffusing unit to the distal end of the propagation

assembly of the intense pulsed light source (hereinafter, briefly, the propagation assembly); and

c) allowing the intense pulsed light to propagate through said at least

one angular beam expander and said at least one diffuser, whereby to scatter said intense pulsed light. The energy density of the intense pulsed light at the first position (as hereinbefore

defined) of the distal end of the propagation assembly ranges from 1 to 100 J/cm².

In one aspect, said first position is in contact with a target to which the intense

pulsed light is directed.

The radiance of the divergent intense pulsed light at the second position of the

distal end of the propagation assembly (as hereinbefore defined) is less than

10*kl*k2*(t^Λl/3) J/cm²/sr, where k2=l and t is pulse duration of the intense

pulsed light in seconds, kl=l for a wavelength ranging from 400 to 700 nm,

kl=1.3 for a wavelength of approximately 570 nm, kl=1.6 for a wavelength of

approximately 830 nm, kl=3 for a wavelength of approximately 940 nm, and kl=5

for a wavelength greater than 1050 nm.

The wavelength of the intense pulsed light ranges from 400 to 1300 nm.

The duration of a pulse of the intense pulsed light ranges from 100 microseconds

to 1000 msec.

The intense pulsed light source is placed with its propagation assembly at the first

position for applications selected from the group of hair removal, skin

rejuvenation, wrinkle removal, treatment of vascular lesions, treatment of

pigmented skin, treatment of acne, treatment of herpes, treatment of psoriasis

and tattoo removal. In another preferred embodiment, the method of improving bodily safety of

bystanders, according to the invention, further comprises the steps of: providing at

least one element of adjustable opacity attached to a handpiece of the intense

pulsed light source, placing said handpiece at a position in close proximity with

said target, increasing the opacity of said at least one element, generating light

from said source, allowing light rays to propagate through the skin and to be

backscattered, and allowing said backscattered light to be absorbed by said at

least one element.

As referred to herein, "handpiece" means a hand-held element having an

elongated, or any other suitable, shape, from which intense pulsed light exits and

which facilitates directing the intense pulsed light to a desired target. Said

handpiece is adapted to house the intense pulsed light source, propagation

assembly, and any control system needed for optimal operation of the invention.

Preferably, the opacity of the at least one element is increased synchronously with, or shortly before, the generation of the light and is decreased following the

generation of the light, whereby the skin is visible during those periods when light

is not emitted by the source. The activation time of the at least one element is up

to 1000 milliseconds and the deactivation time is less than 100 milliseconds.

In one aspect, the at least one element is attached externally to the handpiece.

The inclination of the at least one element relative to the handpiece is preferably

adjusted, in response to an instantaneous position of a bystander. In another aspect, the visibility of the skin is increased by activating a

supplementary light source.

The present invention also comprises an apparatus comprising an intense pulsed

light source, for improving bodily safety of bystanders exposed to the light

generated by said source, comprising a handpiece, *a propagation assembly for

directing the hght of said source, contained within said handpiece, means

attached to said guide assembly, said means adapted to increase divergence of the

intense pulsed light at a given distance between the source and a target, whereby

at a first position of the distal end of said propagation assembly in close proximity

with said target the energy density of an exit beam from said distal end is

substantially equal to the energy density of the intense pulsed light and at a

second position more distant than said first position from said target the radiance

of the light emitted from said distal end is significantly less than the radiance of

the intense pulsed light.

In one preferred embodiment, the diverging means is also a scattering means.

In one aspect, the scattering means comprises a diffusing unit attachable to the

distal end of the guide assembly of the intense pulsed light source, said diffusing

unit including at least one diffuser that is transparent to the intense pulsed light. In one aspect, the scattering means comprises a diffusing unit attachable to the

distal end of the propagation assembly of the intense pulsed light source, said

diffusing unit being selected from the group of at least one angular beam

expander, at least one micro-prism and at least one diffuser, or a combination

thereof.

The diffusing unit is preferably disposed between the intense pulsed light source

and the distal end of the propagation assembly.

In one aspect, the first position is substantially in contact with a target to which

the intense pulsed light is directed.

In one aspect, a coupler is disposed between the distal end of the propagation

assembly and the target.

In one aspect, the apparatus further comprises a mirror disposed between the

distal end of the propagation assembly and the target, said mirror preventing

direct view of the source.

The energy density at the first position of the distal end of the propagation

assembly ranges from 1 to 100 J/cm², the pulse duration ranges from 100 microseconds to 1000 milliseconds, and the wavelength of the intense pulsed light

ranges from 400 nm to 1300 nm. In one aspect, the apparatus further comprises a means for skin cooling, said skin

cooling means being adapted to cool the diffusing unit at the first position of the

distal end of the propagation assembly.

In one preferred embodiment, the apparatus further comprises a dual optical

generation system said dual system being operative to controllably generate either

monochromatic light or broad band intense pulsed light, comprising an apparatus

for improving bodily safety of bystanders exposed to a monochromatic light source,

comprising a means attached to the distal end of the propagation assembly of a

monochromatic light source, said means adapted to cause the monochromatic light

to be divergent, whereby at a first position of said distal end relative to a target

the energy density of an exit beam from said distal end is substantially equal to

the energy density of the monochromatic light and at a second position of said

distal end relative to a target the energy radiance of the light emitted from said

distal end is significantly less than the energy radiance of the monochromatic

light, said dual system being operative to controllably generate monochromatic

light and/or intense pulsed light.

The diverging means of the monochromatic light or of the intense pulsed light is

preferably a scattering means which comprises a diffusing unit attachable to the

distal end of the propagation assembly, said diffusing unit including at least one

diffuser that is transparent to the hght. The diffuser is preferably produced such that any area thereof with a diameter of

0.75 mm scatters impinging light rays to such a degree that said area functions as

an extended diffused light source when viewed from a distance of 200 mm. The

diffuser is made from a material selected from the group of sapphire, glass and

polycarbonate.

Preferably, the diffuser has a first diffusive face and a second smooth face in

opposed relation to said first face, the diffuser being attached to the distal end of

the propagation assembly in such a way that said second face is distal with

respect to said first face.

In another preferred embodiment, the apparatus for improving bodily safety of

bystanders, according to the invention, comprises at least one element of

adjustable opacity externally attached to a handpiece of the intense pulsed light

source and so positioned so as to absorb substantially most of the subcutaneously

backscattered light resulting from the generation of said intense pulsed light

directed to a skin target.

In one aspect, the opacity of said at least one element is adjustable upon

generation of said light.

The element is selected from the group of a liquid crystal window, a spectral

density filter, an attenuation filter, a mechanical shutter, or a combination

thereof. The opacity of a density filter is preferably a predetermined constant value in

accordance with the spectrum of intense pulsed light.

In one aspect, the apparatus further comprises control circuitry for synchronizing

the opacity adjustment of the at least one element, in response to the generation of

the light. The control circuitry is operative to cause the at least one element to be

substantially transparent during those periods when light is not emitted by the

source.

In another aspect, the apparatus further comprises a supplementary light source

externally attached to a handpiece of the intense pulsed light for increasing skin

visibility.

In one aspect, the attenuation filter is an optical band pass filter. The wavelength

of the light that passes through the filter preferably is based on the chromophore

of a lesion to be treated by the light.

In another aspect, the attenuation filter is a spectral filter which blocks the

backscattered light and transmits the supplementary light.

The present invention is also directed to a method of aesthetic improvement,

comprising: a) providing a source for generating intense pulsed light and a light

propagation assembly by which said hght is directed to a target;

b) positioning the distal end of said propagation assembly at a first

position in close proximity with said target;

c) causing said source to generate at least one pulse of polychromatic

light;

d) diverging said pulsed light at a location between said source and said

target, whereby at said first position the energy density of light exiting from said

diverging location is substantially equal to the energy density of the intense

pulsed light; and

e) effecting an aesthetic improvement, wherein the radiance of the light emitted from said diverging location, at a second

position distant from said target, is less than 10*kl*k2*(t^Al/3) J/cm²/sr, where

k2=l and t is pulse duration of the intense pulsed light in seconds, kl=l for a

wavelength ranging from 400 to 700 nm, kl=1.3 for a wavelength of

approximately 570 nm, kl=1.6 for a wavelength of approximately 830 nm, kl=3 for a wavelength of approximately 940 nm, and kl=5 for a wavelength greater

than 1050 nm.

In one aspect, the energy density is at least 1 J/cm² at the first position.

In one aspect, the aesthetic improvement is selected from the group of hair

removal, skin rejuvenation, wrinkle removal, treatment of vascular lesions,

treatment of pigmented skin, treatment of acne, treatment of herpes, treatment of

psoriasis and tattoo removal. In another aspect, the aesthetic improvement is self-effected without use of

protective eyeglasses. During a self-effected aesthetic improvement, a patient

positions the diverging location in close proximity to his skin, holds a handpiece of

the light source, and generates the light while viewing and selecting areas of the

aesthetic improvement.

Brief Description of the Drawings

In the drawings:

Fig. 1 is a schematic drawing of a prior art intense pulsed light source;

Fig. 2 is a schematic drawing which demonstrates the potential damage to

an eye associated with the firing of a prior art intense pulsed light source;

Fig. 3 is a schematic drawing of an intense pulsed light source in

accordance with the present invention, showing an optical effect that results as

intense pulsed light is scattered;

Figs. 4a-e illustrate different configurations of diffusing units attachable to

an intense pulsed light source;

Figs.5a-c schematically illustrate different configurations of devices adapted

to conduct heat from a heated diffuser, following the generation of an intense

pulsed light source, in accordance with the present invention;

Figs. 6a-h schematically illustrate different configurations of a

backscattering protection unit;

Fig. 7 is a schematic drawing of a dual laser and IPL generator, in

accordance with the present invention; Fig. 8 is a picture of an arm of the patient, illustrating the efficacy of

diffused intense pulsed light, in accordance with the present invention; and

Figs. 9a-b are pictures of the distal end of an intense pulsed light source

without and with a diffuser, respectively, showing the lowered radiance that may

be reahzed with the use of the present invention.

Detailed Description of Preferred Embodiments

The present invention is a device for improving bodily safety during exposure to

an intense pulsed light (IPL) source, which device is adapted to diffuse the intense

pulsed light, the diffused light providing the required energy density of light for

desired applications at a very short distance but being inherently safe to the eyes

of bystanders.

In a first embodiment, the IPL source is provided with a diffusing unit which

causes the light exiting from said unit to be scattered. The exit light is scattered to

such a degree that the radiance of said exit light is less than the accessible

emission limit (AEL), and therefore is not injurious to the eyes of bystanders that

are in a direct line of view thereto.

Fig. 1 illustrates a prior art intense pulsed light source designated generally as 1,

as disclosed in US Patent No. 5,683,380, which is suitable for aesthetic treatments

at a target skin location 14. IPL source comprises high intensity pulsed flash lamp

4, which generates polychromatic light, and light guide 8. Generated light rays

such as 5 and 6 are either reflected from reflector 7 into light guide 8 or propagate directly through light guide 8 without any intermediate reflection. The light

energy is transmitted through the light guide and may be reflected by wall 9 of the

light guide towards the skin. The light exits light guide 8 through distal end 11

thereof, which is planar and transparent to the non-coherent light. Distal end 11

is generally placed in contact with target skin location 14, or is extremely close

thereto. The light impinges the skin with a minimal loss in energy density and

due to the extremely small spacing between the distal end 11 and skin 14. The

light energy which propagates through the skin is scattered to a large degree

within the skin and just a small fraction thereof reaches hair follicles 2, blood vessels 3 or collagen bundles 12. Concerning hair follicles, for example, the

scattered light impinges and destroys a hair strand contained within a given

follicle. Intense pulsed light sources are broad band sources, resulting in the

absorption of a percentage of the energy, for example, in one part of the spectrum by melanin in hair filaments and a percentage of the energy in another part of the

spectrum by blood vessels.

The selected spectral band and pulse duration of the IPL source depend on the

specific application. The energy density of the IPL source at distal end 11 of the

light guide, or upon impinging skin 14, has to be above a predetermined threshold

level in order to be efficacious. For example, IPL sources are operated at a

relatively high energy density of 7 -55 J/cm² for hair removal. Some systems

utilize trains of 2-3 pulses, with each pulse having a duration of approximately 2.5

msec at a wavelength substantially above 700 nm (Gold MH, Dermatol. Surg. 1997, 23(10), 909-1). Photorejuvenation is performed at an energy density of 36 J/cm² with three pulses, while each pulse has a duration of 2.5 msec (M.B.Taylor,

ASLMS Abstracts, April 2001, Abstract 130). In other systems, an energy density

level of 10 J/cm² is used. The angular divergence of intense pulsed light may often

be a half angle of 50 degrees, or a solid angle of approximately 2 steradians,

depending on the dimensions of the light guide.

Referring now to Fig. 2, potential eye injury when directly staring at prior art IPL

source 1 may be demonstrated. Light rays 5 or 6 are reflected by wall 9 of light

guide 8, and since they do not necessarily impinge eye 20 they are not definitively

injurious to the eye. However, a direct line of sight 22 may nevertheless be

established between flash lamp 4 and eye 20, causing eye 20 to be exposed to the maximum radiance of the flash lamp. The radiance of the light propagating

directly from the light guide, as represented by direct line of sight 22, is much

greater and more injurious than that which exits distal end 11, since the solid

angle spanned by flash lamp 4 is considerably less than that spanned by distal

end 11, following the reflection of light rays 5 and 6 by wall 9.

Fig. 3 illustrates IPL source 25, in accordance with an embodiment of the present

invention. The distal end of light guide 8 is provided with diffusing unit 15

attached thereto by any means well known to those skilled in the art. The light

guide may be divergent in order to increase the angular divergence of the

propagating light. Diffusing unit 15 comprises diffuser 19, e.g. made of sapphire.

By adding such a diffuser with a diffusing angle of A to the light guide, the image of the flash lamp is blurred on the retina and the flash lamp seems to be an

enlarged extended diffusing source 31, with a width larger than flash lamp 4.

As referred to herein, "diffusing angle" is defined as the angular distribution of

energy that results following the interaction of light with a diffuser, at which

angle the energy density is one-tenth that of the maximum energy density of the

light. A diffuser having a full angle ranging from 4 to 120 angles is suitable for the

present invention.

Scattering is achieved by means of minute irregularities of a non-uniform

diameter formed on the substrate of diffuser 19. Diffuser 19 is preferably produced

from thin sand blasted or chemically etched glass or sapphire, e.g. having a

thickness from 0.1 to 1.0 mm, or a thin sheet of non-absorbing light diffusing

polymer, e.g. having a thickness of less than 500 microns, such as light diffusing polycarbonate.

A diffuser which approaches an ideal transmitting diffuser and induces a scattering half angle of 60 degrees and a scattering solid angle of 3.14 sr may be

produced from material such as polycarbonate by pressing the material against an

appropriate surface provided with a very dense array of Frensnel microlenses,

such as those produced by Fresnel Technologies Inc., USA, or by placing arrays of

microlenses surfaces separated from a light guide as depicted in Fig. 4a.

Diffuser 19 may be produced in several ways: • Sandblasting the surface of a plate of glass, sapphire, acrylic or

polycarbonate with fine particles having a size ranging from 1 to 200 microns;

• Sandblasting the surface of a mold plate with fine particles having a size

ranging from 1 to 200 microns, comprised of, by example, aluminum oxide and

reproducing the contour of the newly formed mold plate surface by pressing hot

acrylic, or other suitable material thereon;

• Etching the surface of a glass or sapphire plate by chemical means, such

as with hydrogen fluoride;

• Etching the surface of a glass plate with a scanned focused CO2 laser

beam; and

• Applying a thin sheet of light-diffusing polymer, such as a polycarbonate

sheet, to a glass plate.

Diffuser 19 is positioned such that its diffusive side faces the flash lamp, whereas

its smooth side faces the skin so that any liquid such as sebum which may adhere

to the diffuser will adhere to the distal smooth end thereof and will therefore not

modify its diffusive properties. The diffuser may be similarly produced in other

ways, such as by sandblasting, such that it conforms with FDA eye safety

standard 1040.10 21 CFR Ch.l. Diffuser 19 is preferably produced from sapphire

which has a high thermal conductivity, and may also be produced from other

materials as well such as glass or highly durable polymers.

The AEL for visible and near-infrared radiation exiting a diffusing unit, for which

protective eyeglasses are unnecessary, is based on an extended diffuser source defined by ANSI Z 136.1 as 10*kl*k2*(t^Al/3) J/cm²/sr, where t is in seconds and

kl=k2=l for a wavelength of 400-700 nm, kl=1.25 and k2=l at 750 nm , kl=1.6

and k2=l at 810 nm , kl=3 and k2=l at 940 nm and kl=5 and k2=l at a

wavelength of 1060 to 1400 nm.

The improved eye safety of the present invention relative to the prior art may be

realized by determining the AEL associated with an exemplary IPL source- a

Xenon flash lamp having a diameter of 2 mm, a length of 40 mm, an energy

density of 30 J/cm², and a spectral band of 645 - 1100 nm, generating a pulse

duration of 30 milhseconds- propagating through a light guide having a length of

120 mm and a distal end having a size of 10x40 mm.

The radiance R of the flash lamp without a diffuser, as in the prior art, is equal to

the energy density of the light (30 J/cm²) divided by the solid angle spanned by the flash lamp light (π, as for any black body light source), further divided by 2,

due to 50% backward light propagation and multiplied by the ratio of the width of

the light guide distal end to that of the flash lamp (10:2) . As a result, R= 75/3.14,

and is approximately equal to 24 J/cm²/sr, approximately 5 times greater than an

AEL of 5 J/cm²/sr, as specified by the ANSI Z 136 .1 standard for a pulse duration

of 30 milliseconds.

In contrast, with the addition of a diffuser, the flash lamp diameter is blurred to a

size of A x L, where A is the diffusing half angle in radians and L is the light guide

length. Therefore, for a diffusing angle of 10 degrees (equal to 1/6 radians), which

is typical for a chemically etched diffuser, and a light guide length of 120 mm, a blurred flash lamp diameter of 20 mm results, corresponding to a reduction in

radiance by a factor of 10. As a result, the radiance of a diffused IPL source is

approximately one-half of the eye-safe limit and therefore the IPL source may be

operated without need of protective eyeglasses.

During treatment, the distal end of the light guide is placed on the skin target, or

in close proximity thereto. Accordingly, it will be appreciated that the addition of a

diffuser to the distal end of the light guide does not affect the treatment efficacy of

the IPL source. The energy density of the light which impinges tissue, after being

scattered by the diffuser, is substantially equal to that of the light emitted by the

flash lamp, due to the proximity of the distal end of the light guide to the skin target.

Other configurations for improving eye safety during exposure to intense pulsed

light are shown in Figs. 4a-e, in accordance with the present invention. In Fig. 4a

an array of micro-lenslets 51 is employed, such as an array available from Fresnel Optics Corp. (USA), wherein each lenslet has a diameter of 0.7 mm. A micro-

lenslet, as referred to herein, has a semicircular cross section, with a diameter

ranging from 0.1-2.0 mm. In Fig. 4b two diffusers 52 and 53 are used. In Fig. 4c

the IPL source is provided with a metallic back reflector 60, without a light guide.

Back reflector 60 is etched as well as transparent distal end 54, to allow for

increased scattering. In Fig. 4d a reflecting mirror 55 is installed, which conceals

flash lamp 34 and prevents direct view of a high radiance zone. In Fig. 4e a pair of

concave and convex reflectors 64 and 65, respectively, are used to thereby conceal flash lamp 34 and prevent staring directly at the flash lamp. Light guide 70 may

be used in conjunction with the configuration of Fig. 4e to further reduce the

emitted radiance. The light which exits from diffuser 53 is received by hght guide

70 and is reflected within its inner wall, resulting in wide angle diffusing from the

entire exit surface of the light guide. A diffusing unit may also be provided with an

array of micro-lenslets, micro-prisms or a combination thereof.

Transparent skin cooling devices are often used in conjunction with skin

treatments. Some skin cooling devices utilize a low temperature transparent

liquid flowing across the distal end of a handpiece in contact with the skin in order

to dissipate the heat generated by the IPL. Other skin chillers utilize a

thermoelectric unit to chill the distal end of a handpiece and to thereby transfer

heat from the skin. However the prior art devices do not scatter IPL and

consequently do not reduce the risks associated with eye exposure to the IPL.

In one embodiment of the present invention, a device for scattering IPL is also

provided with a coohng device. As shown in Fig. 5a, transparent cooling fluid ιsι,

e.g. a low temperature gas or liquid of approximately 4°C, flows across diffuser

180 having a high thermal conductivity, e.g. a sapphire diffuser. Cooling fluid 151

flows through conduit 171, such that it is admitted to the cooling device at port

173 and exits therefrom at port 174. The distal end of the cooling device is in

contact with skin target 185, and conducts heat from the heated skin. In Fig. 5b,

cooling fluid 151 passes through vessel 190, thereby increasing its dwelling time

in the vicinity of diffuser 195. In Fig. 5c thermoelectric chiller 140 chills diffuser 147, the distal end of which is in contact with skin target 185, and may also chill

light guide 145.

Figs. 6a-h illustrate another embodiment of the present invention in which a

handpiece, through which light propagates from an IPL source, is provided with a

liquid crystal backscattering protection unit for attenuating light backscattered

from the skin, which would normally cause an operator to suffer from eye fatigue.

Operators of IPL sources are subject to long term exposure of trains of flash light

pulses reflected from the skin of a patient. Although each optical pulse reflected

from the skin is diffused and is not capable of burning a portion of the retina, the

cumulative effect of a train of pulses results in the tiring of an eye of an operator

since the pupil repetitively expands and contracts in response to the change in

radiance of the light which is incident on the eyeball.

The effect of eye tiring as a result of backscattered radiation is illustrated in Fig.

6a, wherein light guide 202 is positioned to be substantially in contact with skin

201. Light ray 200 which is reflected by the wall(s) of light guide 202 propagates

through skin 201 and emerges from the skin as reflected rays 203 due to internal

backscattering within the skin. Rays 203 impinge eye 1204, resulting in eye tiring

after extended exposure.

As shown in Fig. 6b, eye tiring is prevented by adding a shield around, and

perpendicular to, the distal end of a handpiece of the IPL source. In the illustrated example, normally transparent liquid crystal window 205, e.g. of 2 mm thickness,

is affixed to the distal end of light guide 202. When not activated, window 205 is

transparent and skin 201 is visible to eye 204 by line of sight 210. Window 205 is

provided with transparent electrodes 206 and 207 connected to a power supply

(not shown) by wires 208 and 209, respectively.

When liquid crystal window 205 becomes activated, e.g. by a low voltage of 6V, as

shown in Fig. 6c, its optical properties change and the window becomes opaque to

reflected ray 203. Eye 204 is no longer exposed to reflected ray 203 and eye tiring

is therefore prevented. Window 205 is activated synchronously with, or shortly

before, e.g. 10 msec before, the activation of a flash lamp, so that it will be opaque

during the short duration of flashlight emission from the IPL source. Window 205

may be advantageously activated in accordance with a predetermined timing

sequence by means of control circuitry (not shown). Since the duration of a

treatment pulse is usually not longer than 300 msec and the delay between

successive pulses is approximately 1-3 seconds, the short-duration opacity of the

liquid crystal allows the skin to be visible during those periods when pulses are

not emitted. It will be appreciated that as the transversal dimension of window

205 increases, i.e. perpendicular to the distal direction, more reflected rays will be

absorbed by the liquid crystal. The transversal protrusion of one side of window

205 from light guide 202 ranges from 5-100 mm, and is preferably less than 40

mm. Fig. 6d schematically illustrates a device, generally indicated by numeral 510,

which comprises IPL source 530 that generates hght reflected by reflector 535 and

propagated through light guide 520, handpiece 542, which encircles the light guide

and is held in close proximity to skin target 555, and backscattering protection

unit 540, which is attached externally to handpiece 542. Backscattering protection

540 may comprise a plurality of assemblies 537 that are pivotally displaceable

with respect to the handpiece 542 and that house a corresponding liquid crystal

window 541. Electrical wires 543 and 544 in contact with translucent conducting

surfaces 545 and 546, respectively, of an assembly 537 are adapted to change the

opacity of the corresponding liquid crystal window 541.

Light 547 which exits the distal end of light guide 520 and propagates through

skin 555 is partially scattered, as indicated by numeral 548, by the skin and may

repeatedly impinge eye 523 of an operator. By generating a potential between

surfaces 545 and 546, the opacity of window 541 is increased and backscattered

light 548 which propagates through the instantaneously darkened window 541 is

considerably dimmed. By deactivating the potential, the transparency of window

541 is reset. Since a liquid crystal window is effectively a light polarization device,

an activated window 541 dims to some extent the visibility of the treatment site

which is normally illuminated by non-polarized room light 549. Room light 549

passes twice through window 541- as it propagates towards skin target 555 and as it is reflected therefrom and impinges eye 523. As shown in Fig. 6e, backscattering

protection unit 540 may comprise a high intensity, miniature light source 550 for

the illumination of skin 555, which is externally attached to handpiece 542 at an attachment point between assembly 537 and skin 535. Lamp 550 may emit white

light, thereby compensating for the attenuation of room light 549 at skin target

555.

An exemplary liquid crystal window 541 is a homogenous analog dye guest host

liquid crystal shutter produced by CRL Opto, UK, which has a response time of 20

milliseconds from an activated to deactivated state and a decay time of 70

milliseconds, and is therefore suitable for applications for which visibility cannot

be impaired more than 300 milliseconds. The transition from an activated state to

a deactivated state is at 3.3 V, and since the window has a sufficiently low power

requirement, small Lithium batteries may in use for tens of hours of operation

without replacement.

Another exemplary liquid crystal window is a matrix of liquid crystal pixels,

wherein a thin-film transistor is located at each pixel intersection, requiring a

relatively low amount of current to control the luminance of a pixel. The average

optical transmission of the liquid crystal may therefore be varied with a wide

dynamic range by switching the current through some of the transistors.

An exemplary light source 550 is a white LED, such as the "Photon Microlight II"

produced by L.R.I, OR, USA, having a width of approximately 3 mm. The

illumination of such a light source is maximum at a distance of a few centimeters,

generating a temperature of 6500 deg Kelvin color with a sufficiently low power consumption such that two 3-Volt Lithium batteries are sufficient for over 100

hours of operation.

As shown in Fig. 6f, each backscattering protection unit 540 may comprise a

density filter 551 in addition to liquid crystal window 541. Density filter 551,

which has a predetermined constant opacity in accordance with the spectrum of

the IPL, absorbs some radiation of the backscattered light, permitting only a

fraction thereof to be transmitted. Density filter 551 may be advantageously

employed during the generation of a very bright backscattered pulse, for which a

liquid crystal window could not provide adequate attenuation, e.g. following

inadvertent separation of the distal end of the handpiece from a skin target. The

lack of visibility at the target skin target due to the high attenuation effected by a

density filter may be compensated by increasing the illumination of the low power-

consumption light source 550 upon conclusion of the firing of the IPL, e.g. after a

train of pulses.

As shown in Fig. 6g, each assembly 537 provided with a liquid crystal window may

be pivotally displaceable with respect to handpiece 542. The angular disposition of

assembly 537 is adjustable, so as to provide optimal protection to eye 523, as the

operator changes position, for example, from a sitting to a standing position, or moves side to side.

As shown in Fig. 6h, backscattering protection unit 540 may comprise eye

protection shield 581, e.g. having a conical shape, which may be used for several

applications such as for hair removal. Shield 581 may be a low cut-off filter at the invisible 810 nm wavelength, i.e. is adapted for filtering backscattered IPL at a

wavelength longer than 810 nm. Light at a wavelength longer than 810 nm is

suitable for treating hair without damaging the epidermis. If the optical

transmission of shield 581 at a wavelength below 810 nm is high, the illumination

of room light 549 may be sufficiently high so as to provide adequate visibility at

the skin target. However, if the room illumination is not sufficiently high, light

source 550 may supplement the illumination.

Fig. 7 illustrates a dual system for aesthetic treatments. Dual system 380

incorporates a power supply which can energize both an IPL source 383, which is

insertable through port 381, and laser source 384, which is insertable through

port 382. Each of the IPL source 383 and laser source 384 is provided with a

diffusing unit at the corresponding distal end so that the light which exits

therefrom is eyesafe to a bystander. Co-pending International Patent application

PCT/IL02/00635 by the same applicant, describes an eye-safe laser unit suitable

for aesthetic treatments, wherein a diffusing unit is attached to the distal end of

the laser source. Similarly other configurations for converting highly risky

monochromatic laser units, which are suitable for aesthetic treatments, into non¬

coherent, eye-safe units are described therein.

Example 1

Fig. 8 illustrates the efficacy of diffused intense pulsed light, according to the present invention. A single IPL pulse having an energy density of 20 J/cm² and a pulse duration of 20

milliseconds was directed at an arm 113 of a patient having a hair density of

approximately 40 hairs/cm². A sapphire diffuser, which was thermoelectrically

chilled to a temperature of approximately 4°C, with a diffusing angle of 10 degrees

was attached to the distal end of the light guide of the IPL source. A cut-off

spectral filter with a surface area of 8 x 40 mm, which transmits light at a

wavelength longer than 750 nm, was attached externally to the handpiece of the

IPL source.

The arm of the patient was marked with a plurality of dots 117 to indicate the

skin target at which the IPL was to be directed, an area of 8 x 40 mm. The pulse of

IPL light was fired on October 27, 2002 and the shown picture was taken on

December 15, 2002, at which time the hair density within the treatment zone was

less than 4 hairs/cm². The hair density in the untreated zone was equal to the

hair density within the treated zone before the treatment. It can be seen that an

IPL source provided with a diffusing unit at the distal end thereof is efficacious for

hair removal.

The addition of a diffusing unit can be equally effective for other applications. A

spectral band greater than 550 nm can be utilized for the treatment of vascular

lesions, greater than 400 nm for the treatment of acne, greater than 750 for hair

removal of subjects with dark skin, and greater than 550 nm for

p hotore j uvenation. Figs. 9a and 9b are pictures of the distal end of the IPL source used for the

aforementioned treatment without and with a 10 degrees sapphire diffuser,

respectively. A blinding flash lamp 30 is seen in Fig.9a, whereas the addition of

diffuser 32 resulted in a safe low-radiance, extended diffusing surface, as shown in

Fig. 9b. A filter was added to the camera before the picture of Fig. 9a was taken,

so as to ensure camera integrity, and it will be appreciated that the radiance

emitted by flash lamp 30 was much greater than the light that exited diffuser 32.

Example 2

A small-sized IPL source, which generated a relatively low energy density of 5

J/cm², can be used as a shaver for home use, necessitating shaving only once in

two weeks.

The operator may place a handpiece having a width of 3 cm and a length of 5 cm

on his own face. After the operator depresses the activation switch located on the

handpiece with his thumb, he may shave his face with IPL while viewing his

reflection in a mirror, without need of protective eyeglasses.

A Xenon flash lamp, which has a diameter of 1 mm and a length of 20 mm, with a

spectral emission of 550 nm, thereby being greatly absorbed by melanin, may be

employed. One fired pulse may remove facial hair from an area of 4 x 20 mm. The

pulse duration may be 3 milliseconds, to ensure efficacy at the low energy density 5 J/cm², and the pulse repetition rate may be once in 3 seconds. The face of the

operator may be completely shaved within 3 minutes.

A sapphire diffuser having a half-angle of 10 degrees may be attached to the distal

end of the handpiece, at a distance of 12 mm from the flash lamp. With the

aforementioned parameters, the flash lamp diameter will appear to be 2 mm and

the radiance will be equal to AEL, a value of approximately 2 J/cm²/sr for a pulse

duration of 3 milhseconds. Therefore shaving could be safely conducted without

needing protective eyeglasses. The IPL will not be injurious to the eyes of the

operator, even when the handpiece is separated from his face during the firing of

the light.

As can be seen from the above description, a diffusing/diverging unit of the

present invention, which is mounted to the exit aperture of an intense pulsed light

source induces the exiting light to be divergent and/or scattered at a wide angle.

As a result, the exiting light has a small enough radiance not to be injurious to the

eyes of observers which may accidentally stare directly at the hand piece.

Nevertheless, the exiting light generally retains a similar level of energy density

as the light generated from the exit aperture when the diffusing/diverging unit is

very close or essentially in contact with the target, and is therefore capable of performing various types of treatment. Protective eyeglasses are generally not

needed, particularly since a backscattering protection unit is added to the

handpiece, and therefore an IPL source may be operated in an aesthetic clinic or even in one's home by personnel without any medical training, in a less

cumbersome and safer way than which was known heretofore.

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. Method of improving bodily safety of bystanders exposed to an intense pulsed

light directed to a target, comprising: providing a source for generating intense

pulsed light, causing said source to generate at least one pulse of polychromatic

light, directing said pulsed light to a target, and diverging said pulsed light at a

diverging location between said source and said target, whereby the energy

density of light exiting from said diverging location is substantially equal to the

energy density of the intense pulsed light, and at a distance from said diverging

location the radiance of said exiting light is significantly less than the radiance of

the intense pulsed light.

2. Method according to claim 1, wherein the light source is provided with a

light propagation assembly for directing said light to the target, and the diverging

location is the distal end of said propagation assembly.

3. Method according to claim 2, wherein the distal end of the light propagation

assembly has a first position with respect to a target that is close to said assembly

and a second position with respect to an object that is distant from said assembly.

4. Method according to claim 3, further comprising placing the light

propagation assembly in the first position relative to an intended target of an

optical treatment and in the second position relative to an object that might be

hurt by the intense pulsed light.

5. Method according to claim 2, further comprising the step of scattering the

intense pulsed light, the radiance of said scattered intense pulsed light being

significantly less than the radiance of the intense pulsed light.

6. Method according to claim 5, further comprising:

a) providing a diffusing unit transparent to the intense pulsed light unit

comprising at least one diffuser;

b) attaching said diffusing unit to the distal end of the propagation assembly of

the intense pulsed light source; and

c) allowing the intense pulsed light to be scattered by each of said diffusers.

7. Method according to claim 5, further comprising:

a) providing a diffusing unit transparent to the intense pulsed light comprising at

least one angular beam expander and at least one diffuser;

the intense pulsed light source; and

c) allowing the intense pulsed light to propagate through said at least one angular

beam expander and said at least one diffuser, whereby to scatter said intense

pulsed light.

8. Method according to claim 3, wherein the energy density of the intense pulsed light at the first position of the distal end of the propagation assembly

ranges from 1 to 100 J/cm².

9. Method according to 3, wherein the first position is substantially in contact

with a target to which the intense pulsed light is directed.

10. Method according to any of claims 3 to 9, wherein the radiance of the

divergent intense pulsed light at the second position of the distal end of the

propagation assembly is less than 10*kl*k2*(t^Al/3) J/cm²/sr, where k2=l and t is

pulse duration of the intense pulsed light in seconds, kl=l for a wavelength

ranging from 580 to 700 nm, kl=1.3 for a wavelength of approximately 570 nm,

kl=1.6 for a wavelength of approximately 830 nm, kl=3 for a wavelength of

approximately 940 nm, and kl^δ for a wavelength greater than 1050 nm.

11. Method according to claim 1, wherein the wavelength of the intense pulsed

light ranges from 400 to 1300 nm.

12. Method according to claim 1, wherein the duration of a pulse of the intense

pulsed light ranges from 100 microseconds to 1000 msec.

13. Method according to claim 3, wherein the intense pulsed light source is

placed with its propagation assembly at the first position for applications selected

from the group of hair removal, skin rejuvenation, wrinkle removal, treatment of

vascular lesions, treatment of pigmented skin, treatment of acne, treatment of

herpes, treatment of psoriasis and tattoo removal.

14. Method according to claim 1, further comprising the steps of: providing at least

one element of adjustable opacity attached to a handpiece of the intense pulsed

light source, placing said handpiece at a position in close proximity with said

target, increasing the opacity of said at least one element, generating hght from

said source, allowing light rays to propagate through the skin and to be

backscattered, and allowing said backscattered light to be absorbed by said at

least one element.

15. Method according to claim 14, wherein the opacity of the at least one element

is increased synchronously with, or shortly before, the generation of the light.

16. Method according to claim 14, wherein the opacity of the at least one element

is decreased following the generation of the light, whereby the skin is visible

during those periods when light is not emitted by the source.

17. Method according to claim 14, wherein the time of increased opacity of the at

least one element is up to 1000 milliseconds and the time of decreased opacity is

less than 100 milliseconds.

18. Method according to claim 14, further comprising the steps of attaching the at

least one element externally to the handpiece and adjusting the inclination of the

at least one element relative to the handpiece, in response to an instantaneous

position of a bystander.

19. Method according to claim 14, wherein the visibility of the skin is increased by

activating a supplementary light source.

20. Apparatus comprising an intense pulsed light source for improving bodily

safety of bystanders exposed to the light generated by said source, comprising a

handpiece, a propagation assembly for directing the light of said source, contained

within said handpiece, means attached to said propagation assembly, said means

adapted to increase divergence of the intense pulsed light at a given distance

between the source and a target, whereby at a first position of the distal end of

said propagation assembly in close proximity with said target the energy density

of an exit beam from said distal end is substantially equal to the energy density of

the intense pulsed light and at a second position more distant than said first

position from said target the radiance of the light emitted from said distal end is

significantly less than the radiance of the intense pulsed light.

21. Apparatus according to claim 20, wherein the diverging means is also a

scattering means.

22. Apparatus according to claim 21, wherein the scattering means comprises a

diffusing unit attachable to the distal end of the propagation assembly of the

intense pulsed light source, said diffusing unit including at least one diffuser that

is transparent to essentially coherent intense pulsed light.

23. Apparatus of claim 21, wherein the scattering means comprises a diffusing

unit attachable to the distal end of the propagation assembly of the intense pulsed

light source, said diffusing unit being selected from the group of at least one

angular beam expander, at least one micro-prism and at least one diffuser, or a

combination thereof.

24.Apparatus according to claim 22 or 23, wherein the diffusing unit is disposed

between the intense pulsed light source and the distal end of the propagation

assembly apparatus.

25. Apparatus according to claim 20, wherein the first position is substantially in

contact with a target to which the intense pulsed light is directed.

26. Apparatus according to claim 23, further comprising a coupler disposed

between the distal end of the propagation assembly and the target.

27. Apparatus according to claim 23, further comprising a mirror.

28. Apparatus according to claim 27, wherein the mirror is disposed between the

distal end of the propagation assembly and the target, said mirror preventing

direct view of the source.

29. Apparatus according to claim 20, wherein the energy density at the first

position of the distal end of the propagation assembly ranges from 1 to 100 J/cm², the pulse duration ranges from 100 microseconds to 1000 milhseconds, and the

wavelength of the intense pulsed light ranges from 400 to 1300 nm.

30. Apparatus according to claim 20, further comprising a means for skin cooling,

said skin cooling means being adapted to cool the diffusing element at the first

position of the distal end of the propagation assembly.

31. Apparatus according to claim 20, further comprising at least one

element of adjustable opacity externally attached to the handpiece and so

positioned so as to absorb substantially most of the subcutaneously backscattered

light resulting from the generation of the intense pulsed light directed to a skin

target, the opacity of said at least one element being increased upon generation of

said light.

32. Apparatus according to claim 31, wherein the opacity of said at least one

element is adjustable upon generation of said light.

33. Apparatus according to claim 31, wherein the element is selected from

the group of a liquid crystal window, a spectral density filter, an attenuation filter,

a mechanical shutter, or a combination thereof.

34. Apparatus according to claim 33, wherein the opacity of a density filter

is a predetermined constant value in accordance with the spectrum of the intense

pulsed light.

35. Apparatus according to claim 31, further comprising control circuitry for

synchronizing the opacity adjustment of the at least one element, in response to

the generation of the hght.

36. Apparatus according to claim 35, wherein the control circuitry is

operative to cause the at least one element to be substantially transparent during

those periods when light is not emitted by the source.

37. Apparatus according to claim 31, further comprising a supplementary

light source externally attached to the handpiece of the intense pulsed light for

increasing skin visibihty.

38. Apparatus according to claim 33, wherein the attenuation filter is an

optical band pass filter.

39. Apparatus according to claim 38, wherein the wavelength of the light

that passes through the filter is based on the chromophore of a lesion to be treated

by the light.

40. Apparatus according to claim 33, wherein the attenuation filter is a

spectral filter which blocks the backscattered light and transmits the

supplementary light.

41. Apparatus according to claim 20, further comprising a dual optical generation

system comprising an apparatus for improving bodily safety of bystanders exposed

to a monochromatic Hght source, comprising a means attached to the distal end of

a propagation assembly of a monochromatic light source, said means adapted to

cause the monochromatic light to be divergent, whereby at a first position of said

distal end relative to a target the energy density of an exit beam from said distal

end is substantially equal to the energy density of the monochromatic light and at

a second position of said distal end relative to a target the radiance of the light

emitted from said distal end is significantly less than the radiance of the

monochromatic light, said dual system being operative to controllably generate

monochromatic light and/or intense pulsed light.

42. Apparatus according to claim 41, wherein the means for diverging the light is a

scattering means which comprises at least one diffusing unit attachable to the

distal end of the propagation assembly of the monochromatic light source, said

diffusing unit including at least one diffuser that is transparent to the light.

43. Apparatus according to claim 22 or 42, wherein the diffuser is produced such

that any area thereof with a diameter of 0.75 mm scatters impinging light rays to

such a degree that said area functions as an extended diffused light source when

viewed from a distance of 200 mm.

44. Apparatus according to claim 22 or 42, wherein the diffuser is made from a

material selected from the group of sapphire, glass and polycarbonate.

45. Apparatus according to claim 44, wherein the diffuser has a first diffusive face

and a second smooth face in opposed relation to said first face, the diffuser being

attached to the distal end of the propagation assembly in such a way that said

second face is distal with respect to said first face.

46. Method of aesthetic improvement, comprising:

a) providing a source for generating intense pulsed light and a light

propagation assembly by which said light is directed to a target;

b) positioning the distal end of said propagation assembly at a first

position in close proximity with said target;

c) causing said source to generate at least one pulse of polychromatic

light;

d) diverging said pulsed light at a location between said source and

said target, whereby at said first position the energy density of light exiting from

said diverging location is substantially equal to the energy density of the intense

pulsed light; and

e) effecting an aesthetic improvement,

wherein the radiance of the light emitted from said diverging location, at a second

k2=l and t is pulse duration of the intense pulsed light in seconds, kl=l for a

wavelength ranging from 400 to 700 nm, kl=1.3 for a wavelength of

than 1050 nm.

47. Method according to claim 46, wherein the energy density is at least 1

J/cm² at the first position.

48. Method according to claim 46, wherein the aesthetic improvement is

selected from the group of hair removal, skin rejuvenation, wrinkle removal,

treatment of vascular lesions, treatment of pigmented skin, treatment of acne,

treatment of herpes, treatment of psoriasis and tattoo removal.

49. Method according to claim 46, wherein the aesthetic improvement is

self-effected.

50. Method of claim 46, wherein the aesthetic improvement is effected

without use of protective eyeglasses.

51. Method of claim 49, wherein a patient positions the diverging location in

close proximity to his skin, holds a handpiece of the light source, and generates

the light while viewing and selecting areas of the aesthetic improvement.