Abstract:
A photoepilation device including a compact hand piece applicator and a portable electronics module for use in a non-medical setting. The hand piece, which contains no electrical signals, allows the user to focus on individual hair follicles by observing a magnified image provided on a semiconductor display. The image from the hand piece is transported to a remote CCD through a coherent imaging fiber, which also delivers the therapeutic energy pulse from a remotely located source to the localized target. Destruction of pluripotential follicular stems cells found in the hair bulb and bulge regions is possible via a single low power laser diode. Control of pulse width and spot size attains a range of fluence levels up to 85 J·cm −2 .

Description:
PRIORITY 
       [0001]    This application claims priority to U.S. Provisional Application No. 60/977,851, filed Oct. 5, 2007, the contents of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to methods and apparatus utilizing selective and extended photothermolysis for various cosmetic, health and dermatology conditions, particularly, to techniques using lower power laser diodes for the inexpensive manufacture of safe products that can be used in non-medical facilities such as spas, salons and the home. 
         [0004]    2. Brief Description of the Background Art 
         [0005]    Electromagnetic energy, particularly in the optical band 400 nm to 1200 nm, has been used for treatment of many skin related diseases as well as for cosmetic procedures, such as, hair removal, spider veins, tattoos, port wine stains, and for skin rejuvenation and photodynamic therapy. Laser- and light-based removal of hair, both in men and women, is widely accepted as a successful approach. In today&#39;s market place manufacturers have focused toward three laser-based systems: 1) alexandrite (755 nm), neodymium-doped yttrium aluminum garnet (1064 nm), laser diodes (810 nm) and a broad band intense pulsed light source (IPL). Generally, all systems provide reduction in the growth cycle of removed hair. Multiple treatments have been found to improve upon the longevity of the hair free period. The endpoint for an acceptable treatment requires the destruction of pleuripotential follicular stems cells and not merely the evaporation of the hair shaft. 
         [0006]    Recent data suggests that the stem cells are to be found in upper bulb and bulge regions of the hair follicle. Indeed there may be other areas not yet identified. Laser hair removal (LHR) procedures must target these multiple locations of the stem cells responsible for hair growth. Several techniques have been developed for targeting the destruction of cells. Laser ablation, not typically used for photoepilation, uses high energy short pulses to raise the temperature of the cell above that required for evaporation, however, the target and the absorber must be collocated. Selective photothermolysis (SP) exploits dissimilar absorption coefficients of the photo absorbers and surrounding tissue. However, use of SP for destroying the stem cells responsible for hair growth is compounded because the photo-absorbing chromophore, melanin, is found both in the follicular stems cells and the epidermis. Melanin has a broad absorption spectrum and is responsible for the pigmentation of the hair shaft and the skin. SP techniques are effective if the concentration of melanin is higher, by a factor of five, in the target area. These techniques work particular well for dark hair on light skin. However, unavoidable absorption of photons in the epidermis leads to heat, which needs to be removed if damage to the epidermis is to be avoided. Consequently, innovative hand-pieces which chill the epidermis during treatment have been developed. 
         [0007]    Destruction of cells through thermal denaturing requires that target temperature exceed 70° C. within the thermal relaxation time (TRT) of the tissue, for the hair shaft the TRT is in the range of 35 to 50 ms. Pulse widths exceeding the TRT permit diffusion of heat into surrounding tissue preventing the denaturing temperature to be reached, due to heat leakage. Typically, LHR devices target about 1 cm 2  area of the skin, which is bombarded with photons. Some photons are absorbed in the epidermis, while the remaining migrate, via scattering through the dermis and reach the melanin rich hair shaft and bulb region, where absorption leads to elevation of tissue temperature causing cell destruction. The photons scattered in the backward direction return back to the epidermis resulting in fluence levels, which exceed the incident fluence. 
         [0008]    Based on photon transport theory and clinical data an optimum set of parameters can be established for a particular device. Unfortunately, these parameters are also very patient dependent and use of LHR devices remains somewhat of an art. 
         [0009]    A typical laser diode system will have a variable fluence between 20 to 60 J·cm −2 , a pulse width in the range of 5 to 500 ms, and a treatment spot size of ˜1 cm 2 . The peak power of the source, which determines the size of the LHR system, is proportional to the product of fluence and spot area and inversely proportional to the pulse width. For example, a 100 □s pulse with spot area of 1 cm 2  requires a peak pulse power of 20 kW for a fluence of 20 J·cm 2 . Consequently, this leads to bulky and expensive machines, which need full medical facilities for operation. While the large diameter reduces treatment time and increases penetration depth into the dermis, it lacks the capability to selectively remove hair from a given area, i.e. reduce hair density. 
         [0010]    Another approach for permanent hair removal is based on extended selective photothermolysis (ESP). The target to be denatured can be separated from the photo-absorber, known as the heat source. A closer study of the underlying thermal diffusive processes has led to the use of longer pulses to produce a hot spot in the melanin rich hair shaft. The longer laser pulse produces a hot spot which begins to heat the surrounding tissue, including the hair bulb and bulge. The choice of the pulse width is determined by the TRT and the thermal damage time (TDT). Recent studies have indicated, particularly for techniques using the hair shaft for heat transmission, that a longer pulse width up to 1.5 s may be acceptable, substantially, decreasing the peak power requirement. Several LHR systems using laser diode arrays, with peak power up to 200 W are now in the market. 
         [0011]    Other procedures for efficiently using the available photons in LHR devices include the use highly reflective and thermally conductive applications to the skin prior to laser treatment. Ultrasonic massaging of the epidermis increases the penetration of the dye into. Pre-treatments can be used vital any of the light-based techniques to enhance the efficacy of hair removal, but adds extra time and cost to the treatment. 
         [0012]    Weckwerth U.S. Pat. No. 7,118,563, the disclosure of which is incorporated herein by reference, discloses a rechargeable device suitable for providing therapeutic energy. However, the minimum spot size of 0.25 cm 2  is too large for targeting single hair follicles and thereby causing a reduction in the peak power requirement and their system lacks any imaging device for identifying treatment area. 
         [0013]    Altshchuler U.S. Pat. No. 7,220,254, the disclosure of which is incorporated herein by reference, teaches how the existing technology can be packaged into a self-contained hand-held device for the delivery of therapeutic energy to a skin treatment area, which can be visualized by an image capturing system integrated into the hand-held device. The device combines discrete optical and electronic components to illuminate an area of the skin to facilitate imagining by a CCD/CMOS device. The imaging and treatment optical paths are separated by means of the common practice of using a beam splitter. A more compact and user friendly hand-held device, with few components, would be more desirable, particularly for the home market. In fact, in keeping with this concept, Altschuler et al. Pub. No US 2007/0198004. the disclosure of which is incorporated herein by reference, addresses some of the above problems in disclosing a tethered hand-piece which may be more appropriate for the home market. However, the said photo cosmetic device does not include an imaging capability and uses lower power EMR sources with prolonged exposure times. For hair removal they recommend power levels in the range of 20-500 W, not attainable by a single laser diodes. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention discloses a compact hand piece applicator for LHR, including a coherent imaging fiber (CIF); a fiber optic switch; optical fibers for white light illumination; chilled air delivery system; imaging optics; and an extender for the treatment spot through scanning. The coherent imaging fiber serves a dual purpose: 1) provides an image of the target area, for example, a hair follicle; 2) delivers therapeutic energy from the remote optical source to the target. The spatial cross-sectional distribution of the therapeutic laser energy can be shaped by exciting appropriate pixels in the CIF, for example, a circular spot or a donut shaped spot. The hand-piece provides the ability to alter the size of the target spot, which is expected to be smaller than the diameter of the hair follicle. The laser diode, with a wavelength in the range 750 to 850 nm, provides a broad range of pulse widths applicable to SP or ESP. The power level of the optical source can be increased through the use of multiple single LDs or a single laser diode array. The fiber optic switch, which can be replaced by an optical microphone, controls the delivery of the laser diode energy pulse or pulses. The absence of electrical signals in the hand piece offers added safety to the home user. Further the invention includes a portable electronic system which provides all the controls necessary to operate the system and to interface with other computing devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above and other objects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0016]      FIG. 1  is a block diagram of the portable laser hair removal system of the present invention; 
           [0017]      FIG. 2  is a schematic of the fiber optic hand piece applicator of the device of  FIG. 1 ; 
           [0018]      FIG. 3  is a cross-sectional view of the optical switch of the device of  FIG. 1 ; 
           [0019]      FIG. 4  is a cross-sectional view of a hair follicle with direct illumination of the hair shaft according to the present invention; 
           [0020]      FIG. 5  is a cross-sectional view of the hair follicle with direct illumination of the inner root shaft using a donut beam according to the present invention; 
           [0021]      FIG. 6  is a timing diagram for dual pulse treatment according to the present invention; 
           [0022]      FIG. 7  is a schematic of a dual laser diode illumination scheme according to the present invention; 
           [0023]      FIG. 8  is a schematic for producing a scanning spot on the target according to the present invention; and 
           [0024]      FIG. 9  is a schematic of a preferred embodiment of the fiber optic hand piece applicator according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    The following detailed description of preferred embodiments of the invention will be made in reference to the accompanying drawings. In describing the invention, explanation about related functions or constructions known in the art are omitted for the sake of clearness in understanding the concept of the invention, to avoid obscuring the invention with unnecessary detail. 
         [0026]    The present invention discloses a portable an inexpensive apparatus for locating and capturing the image of a small treatment area, typically, about 250 microns in diameter. Further more the said imaging hand piece, typically less thin 15 mm in diameter, provides for a means to deliver optical energy from a remote source to the target area, preferably smaller than the image size. The small size the hand piece is particularly useful for treatment areas that require a reduction of the hair density and not indiscriminate hair removal. In a preferred embodiment, the hand piece is mounted on a robotic arm for automated laser hair removal. 
         [0027]    Additionally, the small spot can be scanned across the target area to synthesize a large treatment spot. Referring to  FIG. 1  the miniature hand piece applicator (HPA)  100  is an integral part of the flexible umbilical cord  101 , which connects to an electronic console  102 . The HPA can be operated either manually or as part of a robotic arm for automated treatment. In the manual mode, the HPA is moved along the surface of the treatment area  103 , while viewing the color image  104  on a display screen  105 , until a particular target  106 , for example a hair follicle, is located. At this point the image can be captured and stored in an embedded processor system  107 . The imaging system illuminates the target area, transports the image formed at the distal end  108  of the coherent imaging fiber  109  to its proximal end  110 , and captures the image using a CCD/CMOS device  111 . Illumination of the target  103  is achieved by coupling the output from white light emitting diodes  112  and  113  to the proximal end of multimode optical fibers  114  and  115 , which transport the light to the HPA through the umbilical cord. The intensity of illumination is controlled through drive assembly  116 . The microlens assembly in the HPA, see  FIG. 2 , forms a primary image of the target  106  upon the distal surface  108  of the CIF. The magnification of the primary image is adjustable through the height of the baffle  117 . The microlens assembly  118  forms a secondary image of the primary image on the proximal surface  110  at the surface of the CCD  111 . The dichroic beam splitter  119  separates the imaging path from the transmitting path discussed below. 
         [0028]    The transmitting path refers to the optical system responsible for delivering the high energy therapeutic laser pulse (TLP) to the treatment area. Part of this optical system uses the same said CIF described above for capturing the image of the target. In the manual mode, transmission of the TLP is initiated by a user command, which is generated by an optical switch  120  mounted in the HPA Upon receiving the command signal  121  from the optical switch control module  122 , the laser diode driver  123  sends an appropriate current pulse the laser diode (LD)  124 , which is pigtailed to a fiber assembly  125 . The distal end of the fiber assembly is terminated with a microlens assembly  126  which projects the image of the distal surface, via the dichroic mirror  119 , on to the proximal surface of the CIF. The proximal image of the TLP is transported to the distal end of the CIF in the HPA. In this manner, the TLP is delivered precisely to the target with negligible energy leakage beyond the treatment area. The pulse parameters are adjustable through the embedded processor system  107 . 
         [0029]    The optical switch, also discussed in regard  FIG. 3 , modulates an optical signal to define its ON/OFF states. A modulated signal from the light emitting diode (LED) control circuit  122  drives a LED  127  which is pigtailed to an optical fiber  128 . During the ON state the modulated optical signal from HPA is returned back to the control module  122  via an optical fiber  129  which is pigtailed to a photodetector  130 , typically, a pin photodiode. The received optical signal is detected and a waveform  121  is sent to the laser drive module  123 . The waveform  121  generates the TLP with a preset width and contains a delay which prevents generation of further pulses in the event that the optical switch in the HPA either remains depressed or is depressed in rapid sequence. This safety feature prevents the pulse rate from exceeding preset limits. In a preferred embodiment, the optical switch is replaced by an optical microphone in which case the ON signal is generated by the user voice command. 
         [0030]    The HPA  100  also provides for chilled air to be directed at the treatment area. The chilled area is delivered through two stainless steel micro-tubes  131  and  132  from a chilled source and controller  133 . 
         [0031]    Referring to  FIG. 2A , which is a cross-section of the HPA  100 , which is constructed from a cylindrical stainless steel housing  200 . For aesthetic purposes the HPA may be further encased in a specialized molding (not shown). The CIF  109  is located in the central region, surrounded by ring containing tubing and optical fibers as discussed below. The CIF, typically has a diameter of 700 microns and 50,000 individual pixel elements each having a diameter of 4.5 microns. The distal end  111  of the CIF is positioned in the front conjugate plane of the microlens assembly  201 . As illustrated the microlens assembly forms a magnified primary image of the target  106  on to the distal surface  111  of the CIF. The primary image is transported to the proximal surface as discussed above. The image magnification can he controlled by adjusting the height of the opaque baffle  117 . Optical fibers  114  and  115  provide white light illumination  202 , to enhance the quality of the captured image. Stainless steel micro-tubes  131  and  132  are used for transporting chilled air to the target area. Stainless steel channel  203  is used for the optical switch illustrated in  FIG. 3 , while stainless steel channel  204  may include other sensors, for example, a thermistor for monitoring the target temperature. 
         [0032]    During the treatment mode the CIF delivers the optical energy to the target. As illustrated in  FIG. 2   b , it is possible to define any arbitrary spatial distribution  205  and  206  by exciting the appropriate pixels at the proximal surface  110  of the CIF. The microlens assembly  201  produces the desired spatial image on the target. Optical energy is delivered to the treatment area for the programmed precise time and the laser diode disabled until the optical switch is enabled. 
         [0033]      FIG. 3  is a cross-sectional view of the optical switch in the HPA. Two multimode optical fibers  128  and  129  are mounted in the stainless micro-tubing  203 . A modulated optical signal emanates from the distal end of fiber  128 . In the OFF position,  FIG. 3A , the optical signal  300  enters a slab waveguide  301  and is lost. As illustrated in  FIG. 3B , the ON position, the optical signal  300  enters the slab waveguide  301 , and some of the optical signal leaves the slab waveguide and enters the fiber  129  and is detected by the photodetector  130  in  FIG. 1 . The optical switch defaults to the OFF position until switch is moved to the ON position by the user. Activation of the switch will produce a TLP of preset width and repetition rate. This feature adds another layer of safety. 
         [0034]      FIG. 4  shows a cross-section of the hair follicle  400 , which resides in the three layers of the skin: 1) the epidermis  401 , 2) the dermis  402  and 3) the hypodermis  403 . During the anagen phase of the hair growth cycle capillaries  404  provide nutrients to the bulb region  405 , which encompasses the dermal papilla  406 . During this phase of the hair growth cycle the bulb is located 2 to 4 mm below the epidermis. The hair shaft  407  and the inner root sheath (IRS)  408  grow together from the bulb region upward toward the sebaceous gland  409 . Each of the various follicular compartments arises from the germinative cell pool at the base of the hair bulb. The inner most layer of the outer root sheath (ORS)  410  provides the slippage plane. The ORS remains behind and is continuous with the epidermis. The IRS disintegrates just below sebaceous duct and the sheath-free hair fiber exits the pilary canal  411 . The bulge region  412 , the putative site of follicular stem cells and the bulb contain melanocytes, which give the hair shaft its color. These regions are the primary targets for photothermolysis as they exhibit a broad absorption spectrum in the visible and near infrared regions. Melanocytes are composed of eumalanin which is brownish-black and phuemelanin which is reddish. Photons from the TLP need to be delivered to these regions in order to cause cell destruction. SP methods of photoepilation bombard a large area of the epidermis in order to increase the probability of reaching the target areas. Photons in the TLP are lost due to reflection at the epidermis, absorption in the epidermis and scattering in the dermis. The probability of photons reaching the intended targets is extremely low, requiring high surface fluence values and large spot sizes. In addition, deeper targets such as the hair follicle are only reachable at longer wavelength (750-1000 nm). However, the absorption of melanin drops of at longer wavelengths, requiring even higher fluences. 
         [0035]    Decreasing the requirement for peak power through a reduced spot size of the TLP pulse is not a viable solution as the photons migrate out of the target zone very rapidly. Moving to a smaller spot size demands new delivery methods for reaching the intended targets. We describe three optical delivery techniques which target individual hair follicles, typically with a spot size smaller than 10 −4  cm 2 . One of these is the ESP which uses heat diffusion to reach the intended targets by creating hot spots in easily accessible parts of the hair follicle, mainly the hair shaft. However, delivering the TLP directly to the hair shaft, which has a nominal diameter of 80 μm, requires precise spatial location. Imaging and sensor techniques have been proposed for achieving this goal, but all the proposed solutions include scanning functionality in the hand piece, something that should be avoided if the device is to be target for non-medical facilities. 
         [0036]    One possible strategy, illustrated in  FIG. 4 , is to illuminate the hair shaft with a Gaussian laser spot  413 , with a diameter slightly smaller than the hair shaft diameter. Typically, the hair shaft has a diameter of about of 80 μm and the pilary canal has an opening with a nominal diameter of 200 μm. The hair shaft is a highly absorbing medium and has no useful optical guiding properties. Wang, et al. made optical low-coherence reflectometry measurements of longitudinal scans of dark and light hair. They reported that the refractive index of the hair shaft increase from 1.57 for blond hair to 1.59 for black hair. From their data the attenuation coefficient for black and blond hair was estimated to be 34.5 mm −1  and 3.2 mm −1 , respectively. From these measurements, made at 850 nm, the effective penetration depths of 29 μm and 310 μm for the black and blond hairs, respectively was determined. These measurements clearly indicate, contrary to some claims, that the hair shaft is not an optical fiber waveguide. Thus, photons incident on the hair shaft are absorbed within this short layer, causing a localized hot spot  414 . By using lower fluences and longer pulse widths (500 ms), the hair root area can be heated to denaturing temperatures by allowing the heat to diffuse down the hair shaft as indicated by  415 . 
         [0037]      FIG. 5  shows a second illumination strategy, which deposits photons to the melanin rich sites by using the optical guiding channel created by the concentric structure of the hair shaft, the IRS and ORS. Entrance to the three layer waveguide is through the pilary canal  411 . The IRS, which is sandwiched between the ORS and the hair shaft, below sebaceous duct, has a refractive index that is larger than that of the ORS but lower than that of the hair shaft. The three layers form a leaky waveguide, with the photons being absorbed on the hair shaft surface  502  and reflected from the ORS surface  501 . The donut shaped TLP  500  is matched to the size of pilary canal, which has inner diameter bounded by the hair shaft and nominal ring thickness 30-40 μm. Photons enter the pilary canal  412 , which may contain the oil substance excreted by the sebaceous gland and enter the IRS below the sebaceous duct and are guided through the leaky modes to melanin rich bulb region containing the stem cells to be destroyed. As these photons travel in the IRS some are likely to be absorbed by the melanocytes in the bulge. The fluence levels are expected to be lower as none of the incident photons are absorbed by epidermis or the dermis. Consequently the epidermis should experience minimum heat stress. In this configuration pulse widths should correspond to the TRT of the bulb region. 
         [0038]    A third illumination strategy can be a combination of both the above. A short pulse width donut beam can be superimposed on the long pulse width Gaussian beam toward the end of its duration as indicated by the timing diagram in  FIG. 6 . This strategy allows the hair shaft temperature to be elevated by the extended TLP directed at the hair shaft, followed by the donut shaped pulse just prior to the termination of the Gaussian pulse. The Gaussian beam may have a pulsed width in the range of 100 to 500 ms, while the donut pulse width is between 5 and 50 ms. In principle, the two laser diodes may have different wavelength and deliver different fluence levels, which could be matched for the hair color. Referring to  FIG. 7  LD  701  is pigtailed to a single multimode fiber which forms the central part of the distal end  706  of the fiber optic bundle  705 . LD  702  is pigtailed to a fiber bundle  704  comprising of multiple fibers  707  which are arranged in an annular pattern  708  in the distal end of fiber bundle  705 . In this way LD  701  and  702  may either have identical or dissimilar spectral and power properties. The distal end  706  can be integrated to the microlens  126  in  FIG. 1 . 
         [0039]    There may instances when neither of the above strategies for delivering the TLP is acceptable and a larger spot is required. As discussed above, with reference to  FIG. 2 , it is possible to produce any arbitrary illumination shape. For example, an elliptical spot which increases the spot dimension along one axis, while keeping the area small could be used. However, there may be instances when this approach is also not adequate. In such situations a large treatment area can be synthesized by scanning the small spot over the target area. Sharon, U.S. Pat. No. 7,101,365, the disclosure of which is incorporated herein by reference, describes a manual means to pivot the entire hand piece to obtain a limited scan. While Altshuler (discussed above) and Zavisian, U.S. Pat. No. 5,860,967, the disclosure of which is incorporated herein by reference, include a 2-D scanning mechanism in the hand piece. The present invention achieves the desired scanning of the target by scanning an image of the source at the proximal end  110  of the CIF. Referring to  FIG. 8 , dots  801  and  802  show two arbitrary positions of the TLP on the target surface  103 .  FIG. 8B  indicates the position of the corresponding source points on the proximal end  110  of the CIF. The target scan path corresponds to the scanned source image on the proximal end. The scanned image can be generated in number of ways. For purpose of illustration  FIG. 8C  shows 2-D mechanical scanner using mirrors  803  and  804 . The laser source beam  805  bounces of the two mirrors to define a scan path  806 .  FIG. 8D  illustrates an alternative means of obtaining the source scan, using 1×N fiber optic switch. In other words, the output of the input fiber  807  can be directed to any one of the output fibers  808  by means of, for example, a rotating concave mirror  809 . Other types of switches may be used. The output fibers form the distal end  706  of the fiber bundle described in  FIG. 7 . An important difference between the Sharon and Altshuler schemes is that all the scanning components are in the portable electronic module, none of the components are in the HPA. This ensures a compact and safe hand piece suitable for the non-medical facilities. 
         [0040]    There are certain situations when indiscriminate hair removal using a large diameter spot is not desirable. As an example, for cosmetic purposes, patients may require an alteration of the hair density in certain parts of the human anatomy rather than total hair removal. For such applications a LHR system must be capable of targeting individual hair follicles. The HPA described above can be used on a robotic platform to remove hair from any random location. One such embodiment will include a 3-D vision system in capable of creating a digital map of the surface to be treated. Appropriate software algorithms that analyses the hair distribution and hair angle will determine the optimum location of hair follicles to receive the laser treatment. The information would drive the robotic arm to automatically complete the treatment. Safety features, built around limit switches, ensure that the high energy spot remains with the treatment area. 
         [0041]    Another preferred embodiment of the HPA is illustrated in  FIG. 9 . The CIF  109  is surrounded by plurality of multimode fibers  901  which are used for delivering high energy optical pulses to the hair follicle. The output of these multimode fibers is combined into a single spot at the entrance to the hair follicle  106 . A radially bi-focal lens  902  provides disparate magnifications for the CIF  109  and the multimode fibers  106 . The multimode fibers can be used to increase the target fluence by using plurality of optical sources at the same emission wavelength, or alternatively sources with output at different wavelengths could be combined to enhance the efficacy of the treatment. 
         [0042]    An example of the fluence calculation in a preferred embodiment is as follows. An expected fluence F t  [J·cm −2 ] at the target spot of area A t  [cm 2 ] for an imaging system with magnification M t  is related to the power P f  emanating from the pigtailed laser diode by Equation (1): 
         [0000]    
       
         
           
             
               
                 
                   
                     F 
                     t 
                   
                   = 
                   
                     η 
                      
                     
                         
                     
                      
                     
                       
                         
                           P 
                           r 
                         
                          
                         
                           σ 
                           T 
                         
                       
                       
                         A 
                         T 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where η represents all the transmission losses from the output of fiber  125  to the laser spot illuminating the treatment area  103  and σ T  is the pulse width or duration of the optical energy pulse which can be easily controlled between 100 μs to 1 s. Using a conservative estimate of η=0.85, P f =200 mW, A t =10 −1  cm 2 , which is a typical diameter of the hair shaft, and σ T =50 ms, we obtain F t =85 J·cm 2 . The fluence can be easily controlled though a combination of the three parameters, P f , or σ T  or A T . 
         [0043]    While the invention has been shown and described with reference to certain exemplary embodiments of the present invention thereof, it will be understood by those skilled in the art that various changes in from and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims and equivalent thereof.